texts: Can someone double check my resistor identification?

texts:
I have a resistor I need to replace.  It is fairly large measuring 11mm long with 4mm diameter.  All of the hobby resistors I have are 1/4 watt and make this thing look gigantic.

Do you think it is a 1 watt, or is there some larger value it could be?

I am also attempting to read the bands, and I see: Red Red Silver Gold.  Which is a 0.22 Ohms 5%.  Am I reading this correctly?

I was actually able to find the schematic for this power supply, and it is a .22 Ohm.


texts: How does this high pass filter in a mini color organ function?

texts:
I am trying to figure out how this filter circuit works:

The filter is part of a mini color organ from Forrest Mims Engineer's Mini-handbook. I know it is a high pass active filter which will only illuminate the green LED at certain frequencies, but every other high pass active filter I've looked at has the cap and resistor in series both going to the inverting input. Can somebody please help me undertstand how this filter works? Thank you!


texts:
I am trying to dim a 24v led-strip with a 3.3v PWM-signal coming out of a ESP32. Currently I have this circuit:

But there is one problem. It works for dimming till ~40%. But when I turn the PWM off, the LED-strip keeps on at the ~40% brightness. When removing the connection between U1 and Q1 the LED-strip stays on also (~40%).

U1 was necessary because otherwise the PWM signal at 1.0 duty-cycle wasn't enough to fully turn the LED-strip on. It barely turned on actually. (LED strip activates at around 18v)

I'm not the best engineer when it comes to circuits, so excuse me if I am making a dumb mistake.

I would like to hear your thoughts and suggestions.


texts:
Most of the ADCs I see are designed for a single sensor voltage.

I have read that this is not a problem for something like an acoustic sensor like a hydrophone because the ADC can be multiplexed so fast that it easily samples the sound.

So, for example, if you want to sample at 10 kHz, which is sufficient for underwater situations, and you have a 100 element array, then you would just need for the ADC to be able to sample at 10 kHz * 100 = 1 MHz which an ADC can do no problem.

Is that analysis correct, or are there multichannel ADCs that accept 100 or 1000 analog inputs and have an advantage over multiplexing? If so, what is that advantage?


texts:
I'm building my first arduino project, and I could use some help building up the relay portion.

My goal is to control a water pump that's running at 110V, 3/4hp, rated at 9A, and measured to run at 500 watts.

Initially I selected a 10A relay module from Sainsmart:

amzn.com/B0057OC6D8
www.sainsmart.com/arduino-pro-mini.html

However, after reading about motor loads, I'm worried that I undersized the relay. Now I'm looking at:

A 20A EM relay:

amzn.com/B00R7TTSMI
Is this enough of a safety factor for my motor size
Would the Arduino have enough current to drive the coil, would I need additional circuitry to drive it?

A 25A SS relay:

amzn.com/B0087ZTN08
Pro, comes with a heatsink
Would the 25A really be enough to support the startup spike of the pump motor?

A 40A SS relay:

www.sparkfun.com/products/13015
amzn.com/B00HV974KC
amzn.com/B00E1LC1VK
Does not include heatsink. Do I really need a heatsink for a constant 9A running through a SS relay?

How about a flywheel diode? I'm guessing that for an EM relay I should include a flywheel diode. I've seen reference that SS relays normally include snubber circuitry. Is this the case, and would either of the SS relays basically be drop-in with my application (5V arduino logic pin, directly to VDC side, 110VAC hot line through the VAC side).

I've read that EM relays are beefier and more reliable than SS. And I've also read that EM tends to fail open, whereas SS fails closed (potentially destroying my pump). However, the idea of a relay with no moving parts, zero-crossing switching, and an onboard snubber is really attractive.

What's your recomendation?
Thanks for your help in choosing.


texts: What to call the cells of memory in a computer or a microcontroller?

texts:
I don't know if this is the right forum to post this question, but I thought so because this forum is for educators and I'm a trainer and my question is related to education.

I want to do an introduction for a technical manual about basics of microcontroller, and got to the memory chapter.

I started with a definition for the three main memory types in a microcontroller, which are:

Program memory (ROM): Which is basically a flash memory for storing the program HEX file for execution.
Data memory (RAM): Which is for processing data during operation of the microcontroller, but the data is lost after resetting the microcontroller.
EEPROM: Which has the advantage of reading and writing data during the operation of the microcontroller and also keep the data after resetting the device.

Then, I posted a picture of microcontroller's block diagram and how it's connected to the internal units as a subtitle of the memory chapter.

The next subtitle is the term "registers" as they are the building block of any type of MEMORY in computer, whether it's ROM, RAM or EEPROM. Because I found this information in a website, and want to be sure.

This is the link to the website:

Link

Section 5.1: Registers. As the previous section is 4. Program Memory.

Then in section 5. Data memory, the author explain the sub-parts of Data memory which are:

5.1 Registers
5.2 Bits and bytes

So, my question here, is: Registers are memory cells to every memory type, and the difference is that ROM memory are non-volatile registers, RAM are volatile registers and EEPROM is also non-volatile registers? So they all are basically register.

=====================================================

Add1: I want to add this picture I found in an eBook:

So, the only memory called registers is the CPU registers other memories called just memory. But how about the arrangement in microcontroller sector?

=====================================================

My updated question is how registers differ from other memory cells in other types of memories? Like, Flash and EEPROM memories.


texts: How to solve current source prb W/O using Nodal Analysis?

texts:
I have the full solution to this problem, but it is using nodal analysis.
I am not a fan of Nodal Analysis. Is there a different approach to this problem?


texts: Why does my lightbar draw more current when connected to a battery than a power supply

texts:
When I measure the current draw of the lights when connected to a car battery, they draw about 2.4A

However if I connect the lights to a 12V power supply, they only draw around 0.8A. Even though the power supply says it can output 5.4A at 12V

I'm just wondering why this is, and is it possible to force the power supply to give the lights 2.4A
Edit: after measuring the voltage of the power supply when the lights are connected, it is only 8V which explains why the current draw is lower. It does read 12V with nothing connected though, What does this mean?
Thanks


texts: How to estimate the voltage gain, Input impedance, current gain, power gain, and output impedance for the amplifier in the fig?

texts:
β of the BJT is 100 and from dc analysis it is found that the quiescent point is ICQ=4.12mA and VCE = 6.72V.
If the emitter resistor RE is subdivided into RE1=100 Ω and RE2=900 Ω, with bypass capacitor in parallel with RE2. How to calculate the answers, How this circuit is affected by this change?

Ans: By Ac equivalent circuit,
I have calculated input impedance
Zi=(beta+1)re || (R1||R2) = 6.770Kohm/5.36Kohm = 1.263 Kohm

Where re is the dynamic emitter resistance = 26mv/Ie
and to calculate Ie, I did DC analysis and by Thevenin equivalent ckt (Vth=5/15*15 =5V & Rth=R1||R2= 3.33 Kohm)
then by KVL , Ib=Vth-Vbe/Rth+(beta+1)*1Kohm= 0.127microA
therefore Ic=100*Ib=1.27mA and Ie=Ib+Ic=1.291mA.  so re=26mv/1.291mA=20.13ohm

then output impedance is
Zo=ro||Rc...... by ac equivalent circuit
ro is not given so I assumed ro>> very high
therefore Zo=Rc=1Kohm

Av= -betaIbRc/Ib(beta+1)re
assuming beta+1 ~ beta
Av= -Rc/re = -49.67

I am stuck with Ai(current gain) calculation and Power gain calculation now


texts: 2-way mini motion sensor (mirror switch)?

texts: So a mirror switch will switch ON with 1st "swipe" and OFF on 2nd "swipe". I want to set it up in a 2-way configuration whereby if you pass switch 1 it's ON and then pass switch 2 it's OFF, then pass switch 2 again and it's ON again and so on much like a 2-way lighting circuit. I assume the sensor needs to be a 2-way or can i do this with a 1-way sensor? anyone know anything like this?


texts: A system simulator that allows for verilog modifications?

texts: My current research is on hardware security against software attacks, thus I wanted to run some sample C code attacks using a simulator. Do x86-64 simulators (i.e. Marssx86 or QEMU) allow for the user to modify the architecture by adding verilog code? Is there an x86 simulator (either 64 or 32 bits) which creates a processor using verilog?


texts: Configure Serial with registers on STM32l073RZ

texts:
I'm trying to configure the Serial of my STM32L073RZ with registers to send datas on the PA_9 pin.
Currently I have this script

#include "mbed.h"

void usartSetup (void) {
    RCC->IOPENR |= RCC_IOPENR_IOPAEN;
    GPIOA->ODR |= GPIO_ODR_OD9;
    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;            // enable clock for USART1
    USART1->BRR  = 160000 / 96;              // set baudrate
    USART1->CR1 |= (USART_CR1_RE | USART_CR1_TE);  // RX, TX enable
    USART1->CR1 |= USART_CR1_UE;                    // USART enable
}

void SendChar(){
    while (!(USART1->ISR & (USART1->ISR | USART_ISR_TXE)));
    char stringtosend[4];
    stringtosend[0] = 'T';
    stringtosend[1] = 'e';
    stringtosend[2] = 'x';
    stringtosend[3] = 't';
    for(int send = 0; send < 4; send++){
        USART1->TDR = stringtosend[send];
    }
}

int main() {
    usartSetup();
    SendChar();
}

You can also see my project here on the mbed website

When I display the pin state with my oscilloscope this one is always to zero.

Does anyone can help me ?

Thank you !

EDIT:

Below you can see my current script, it work fine for write and read something, I juste want to configure external clock on the PB_5 pin but it's note working. I also try to configure the UART in smart card mode

#include "mbed.h"

void board_init(void){
    RCC->IOPENR |= RCC_IOPENR_IOPBEN;
    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;            // enable clock for USART1
    USART1->BRR  = 320000 / 96;              // set baudrate

    GPIOB->MODER &= ~GPIO_MODER_MODE5_0;
    GPIOB->MODER |= GPIO_MODER_MODE5_1;

    GPIOB->MODER &= ~GPIO_MODER_MODE6_0;
    GPIOB->MODER |= GPIO_MODER_MODE6_1;

    GPIOB->MODER &= ~GPIO_MODER_MODE7_0;
    GPIOB->MODER |= GPIO_MODER_MODE7_1;

    GPIOB->AFR[1] |= 0x500000;
    GPIOB->OTYPER &= ~GPIO_OTYPER_OT_5;
    GPIOB->OTYPER &= ~GPIO_OTYPER_OT_6;
    GPIOB->OTYPER |= GPIO_OTYPER_OT_7;

    USART1->CR3 |= USART_CR3_DMAT;

    //Secure element part
    USART1->CR2 &= ~USART_CR2_LINEN;
    USART1->CR3 &= ~USART_CR3_HDSEL;
    USART1->CR3 &= ~USART_CR3_IREN;
    USART1->CR3 |= USART_CR3_SCEN;
    USART1->GTPR = 32 >> 1;
    USART1->CR2 |= USART_CR2_CLKEN;
    USART1->CR3 |= SMARTCARD_NACK_ENABLE;
    USART1->CR2 |= SMARTCARD_STOPBITS_1_5;
    USART1->CR1 |= USART_CR1_PCE;

    USART1->CR1 |= (USART_CR1_UE | USART_WORDLENGTH_8B);  // RX, TX enable
    USART1->CR1 &= ~USART_CR1_RE;
    USART1->CR1 &= ~USART_CR1_TE;
}

void delay(int cnt) {
    while (cnt-- > 0) {
        asm("nop");
    }
}

int usart_rec(void) {
    /* Wait until the data is ready to be received. */
    while ((USART1->ISR & USART_ISR_RXNE) == 0);

    // read RX data, combine with DR mask (we only accept a max of 9 Bits)
    return USART1->RDR & 0x1FF;
}

void usart_rec_str(int array[], int sizeArray){
    USART1->CR1 |= USART_CR1_RE | USART_CR1_TE;
    for(;;){
        pcMain.printf("%i",usart_rec());
    }
    USART1->CR1 &= ~USART_CR1_RE;
    USART1->CR1 &= ~USART_CR1_TE;
}

void usart_snd(int data) {
    USART1->TDR = data;

    // wait for TX
    while ((USART1->ISR & USART_ISR_TXE) == 0);
}

void usart_snd_str(char *str) {
    USART1->CR1 |= USART_CR1_TE;
    int   i = 0;
    while(str[i] != 0) {
        usart_snd(str[i++]);
    }
    USART1->CR1 &= ~USART_CR1_TE;
}

void usart_snd_str(int array[], int size) {
    USART1->CR1 |= USART_CR1_TE;
    for(int j = 0; j<size; j++) {
        // read blocking form usart
        usart_snd(array[j]);
    }
    USART1->CR1 &= ~USART_CR1_TE;
}


texts: Why is the input to output delay time for transistors not provided in the datasheet?

texts:
I am using this BC807-40 transistor.

My maximum collector current through the transistor is 200mA.

I want to calculate the delay time between the transistor input Vbe and output Ic.

Is there a way or formula to calculate the delay time theoretically?  I couldn't find any delay specification mentioned in the datasheet.

Whereas, for a MOSFET which I have used in a different circuit, I was able to find the delay time:

It is mentioned in the datasheet as turn on delay time and turn off delay time.

But this delay parameter is not available for all transistors.

Why don't the manufacturers of transistors mention this delay in their datasheet? Is it because transistors switch slower when compared to MOSFETs? Or which switches much faster between input and output?

Please explain.


texts:
I want to use a transistor to control a 5v power source but Im confused on how to control the base pin.

How much voltage can I put on the base pin? I've seen tutorials which use 5v with a 1k resistor, but doesnt this exceed the saturation voltage of 0.7v?
Also if I were to use a voltage divider circuit to lower the voltage, would this provide enough current to turn on the transistor?

Im using a tip120 transistor. Thanks for any help


texts:
I built a circuit that pulses a 50-ohm electromagnet when a 'trigger' magnet passes over a hall-effect sensor.  This circuit swings a pendulum and simultaneously plays an audio clip as long as the 555 timer output is high.

Schematic:

(Link to this design on Circuit Lab website)

This worked perfectly on a breadboard, but when I mounted all components on a small soldered circuit board, the audio module now resets (starts from the beginning, indicating a loss of power) each time the coil is triggered.

I used (4) AA batteries so I could tap the 3rd cell to provide ~5v to the audio module and avoid using a 7805 or similar.

I have an electronic engineering background, but not enough experience to know what may be causing the problem or what modifications are needed.  I also unfortunately do not have an oscilloscope.

I am very interested to understand what may be causing the problem and very much appreciate any help the forum can provide.

Many thanks in advance!


texts: Can I use 74HC14 or NPN transistor instead of MOSFET as level shifter

texts:
I have SN74HC14 or BC548 / 2N2222 transistors. I need level shifter for I2C between arduino and RPi.
Here's simple circuit from the internet

Problem is I don't have any MOSFETs. Can I use NPN transistors instead? or do I better use 2 74HC14 NOT gates as single MOSFET?


texts: Is Gain Block can be used a Power Amplifier

texts:
I have chosen 2 datasheets of MMIC Power Amplifier:

HMC311ST89 MMIC AMPLIFIER – DC-6GHZ  -16db Gain
HMC637ALP5E – DC-6GHZ – 13db Gain

My intention is to use the 1st one as Power Amplifier. I was wondering whether I am going right because the 1st one description is GAIN-BLOCK whereas, the 2nd one is mentioned as Power Amplifier as per the respective datasheet.


texts: What is the effect on kWh if the power company reduces line voltage to a residence?

texts:
We just received our power bill and it is showing a 30% rise in kWh for the past month. Nothing has changed in our home. We were even gone one full week in the month.

To make it more interesting, this past summer our stove would not ignite because the line voltage was 108 V because it requires a 2.4 amps through the igniter before the gas valve will open (at 120 V). I contacted the electrical supplier and they came out, confirmed the condition and changed the tap because AC units were pulling the line down. All was well. They then came back out weeks later, but I don't know what they did. (Changed it back, perhaps?) Yesterday we tried to use the oven and wala-no ignition. I was in a hurry to go somewhere and could not check the voltage, but when I did last night it was 114 V. Are the higher kWh usage and low line voltage related issues? I don't know. With refrigerators and pumps on the line as inductive loads, will their changes in efficiency at lower voltage cause higher kWh? It would seem so since losses would go up. That's the main question.


texts: Has someone here ever made a DIY LiDar from scratch that can 3D scan? If yes, can you give an explanation regarding the process of doing so?

texts: We've been tasked to create a LiDar system from scratch (we're not allowed to use modules like TFMini and vl53l0x, we have to make it from scratch) that can output 3D projections. So far we've been successful in creating a module, but we're not so sure how to implement the 3D modelling part. The only idea that I have is we'll have to use a micro-controller unit or something even more powerful.


texts: Can we possibly have too large wire to drop voltage over a long distance?

texts:
I had a argument with a friend about whether how can we possibly have too large wire gauge?
Assumption 1. The voltage will never drop over a long distance (200 feet) because the wire is too large. No matter of low voltage is and how little amps source provide.
Assumption 2. The voltage will drop more over a long distance (200 feet) on too large wire (AWG 16 vs AWG 6), if the voltage is low (5V) @ 0.5 Amps source providers.
It sounds like a extreme case but it comes from the phase that "Too large wire never drop current but only hurt your pocket".


texts: How does the overdrive voltage relate to the transistor size?

texts:
I am a student currently learning analog IC design. I am wondering how the overdrive voltage of a transistor(Let's say NMOS/PMOS), relates to the size of the transistor.

For example, if an NMOS transistor M1 with size 1X has an overdrive voltage of Vov, what is the overdrive voltage of NMOS transistor M2 with size 0.25X in terms of Vov? Similarly, if a PMOS transistor M3 with size 1X has an overdrive voltage of Vov, what is the overdrive voltage of PMOS transistor M4 with size 4X in terms of Vov?

Thank you!


texts: Power Consumption and Expected Lifetime for a given design

texts:
I have a requirement where I need to sense proximity with Hall Effect Magnetic switch and to send the detection over Bluetooth. There are space constraints for this module and hence coin power cell is most suitable.

I have researched and found low power chips such as Murata MRMS201A Magnetic switch and Murata LBCA2HNZYZ-TEMP Bluetooth Module. I have already got the components and development board for the Bluetooth module.

Datasheets:
Magnetic Switch
Bluetooth

The circuit I have designed

The specs for sensor are:

MRMS201A

and for LBCA2HNZYZ-TEMP

Based on these specs could someone please help me to estimate the power consumption and life expectancy for 3V 225mAh coin cell or if I use an AA cell. The value of R1 should also be selected to reduce power consumption and LED1 Spec could be assumed to be standard. Or a very low power LED could also be used, if someone suggest me the part number.

Any design modification to enhance the battery life is also welcome. One I have thought is that the power supply to MRMS201A should be triggered by Bluetooth module only i.e. it does not sense the proximity always but only when Bluetooth module triggers it to sense.

My goal is that the circuit should run at least 6 months without changing the battery and I have very less experience with electronics circuit design.


texts: Does Altium Designer 14 work with Windows 8?

texts:
I have a AD 09 license from my school, and they said it would not work on a W8 pc. Now I am in process of getting a new laptop. Since most laptops come with W8, I am wondering if I will be able to run Altium if I upgrade it too. Does anybody here have any experience?

I tried searching, but "Altium designer windows 8" doesn't really bring up anything, for or against.

Another option is to install W7 on the laptop, but I am not sure if all the drivers are available for anything else than W8. (Although I think some W8 pro computers come with a downgrade option)


texts: ‘One for all’ standardized land pattern v.s. specified land pattern in datasheet

texts:
I’ve designed lot of ‘simple’ PCBs for hobby and proof-of-concept purposes, but never for (mass)manufacturing. In order to do so in the future, and further expanding my design skills and knowledge, I’m exploring the different package outline standards.

By now I learned there is no such thing as “one main standard for all packages”. Instead, there are multiple standards for multiple packages, set up by multiple organizations. ‘Most recognized’ are IPC and JEDEC standards.

But even within IPC there are multiple versions. IPC-7351B is the most recent from IPC (at the time of writing).

I learned* there is no such thing as a “standard” 0603 (1608 metric) package outline for example. Instead, a 0603 footprint (aka ‘land pattern’) depends on desired board density and the used soldering technique in manufacturing (wave or reflow).

*by reading in the standards itself as well as these interesting threads:
here,
here
and
here.

This was quite a revelation to me as I previously assumed those generic packages were standardized in a way (because they are so common).

Anyway, I accepted this reality of chaotic standards and I understand I had to choose one standard for myself to work with.
I choose IPC as it is by far the most used in the industry.

My CAD software (Autodesk Eagle) offers a very practical package generator which satisfies IPC norms. It generates a land pattern for - and 3D model of - a desired package which is IPC compliant.

However now I'm faced with a dilemma. I discovered not only a “standard 0603” does not exist (which I'll solve by sticking to one standard), but apparently even a “standard LQFP48”, for example, does not exist!

For example: take following components
from Microchip
, from TI
, from STM
; they all have an LQFP48 package with same case size and pad pitch.

However, all three datasheets specify a slightly different land pattern for what I thought was the exact same LQFP48. The difference is subtle, and only affects the extension (length) of the pad and pad width (0,25 - 0,27 - 0,30 respectively), but it is there!

So what is the rule of thumb now? What would experienced PCB designers choose if these components were in the same design?

option 1: Using 3x a different land pattern for what is actually described as the same package outline.

option 2: Use the IPC-7351 compliant LQFP48* for all three.

*in IPC terms this would be: QFP50P900X900X160-48

Since the differences are so subtle, I know both options would probably turn out just fine but what is the general rule here?
What is ‘good practice’?

Many thanks!


texts: Start capacitor on shaded pole to increase starting torque- how to size

texts: Can I add a capacitor to a shaded pole motor to increase starting capacity? How do I size it? I have a single pole squirrel cage motor running a conveyor toaster that is dying while trying to start. Just want to give it a bump 120v 60hz i=1:320.7


texts: How can I add a power-off delay to this circuit

texts:
This may seem simple but I am trying to learn EE. In the below circuit, how can I add a delay when the button is released the relay will stay energized for approx. 5 seconds.

My Circuit:

Coil Voltage Nominal 5VDC; Max - 6.5vdc
Input voltage = 6VDC

As I mentioned I am learning. My initial thought was a resistor–capacitor circuit (RC circuit). But I am not sure how to achieve this. Thank you for the help.

Edit - as suggested I added a schematic. I hope its correct.


texts: SIM 800L, I lose signal (+CSQ=0,0) once I insert the SIM card

texts:
I have a GSM/GPRS module, SIM800L, and I am facing network difficulties with it.
If the SIM card is not inserted, the antenna connects perfectly to the network with +CSQ=0,16.  However, once I insert the SIM card, I lose network connection and +CSQ=0,0.


texts:
I have designed and built a small solenoid and... it doesn't exert any force on the steel bolt I am using as a plunger. I could freely move the plunger back and forth without any resistance.

I am using 0.2mm copper wire with a plastic coating.
The coil cross-section is 15mm x 3mm (inside radius = 2.5mm, ouside radius = 5.5mm)
I calculated that I could get about 1125 turns on the solenoid with a resistance of 14.7 Ohms. For the actual solenoid I measured 11.7 Ohms.
The solenoid frame is made of plastic.
The plunger has a 3mm diameter and the gap between the coil and the plunger is 1mm, of which 90% should be plastic and 10% air.
The overall radius of the solenoid is 5.5mm.
I applied 12V and the total current draw was 1.02A.
The solenoid became hot after 20 or 30 seconds, as expected.

I put the values into this calculator: http://www.daycounter.com/Calculators/Magnets/Solenoid-Force-Calculator.phtml

I = 1.02
N = 1125
A = 95 mm2 (PI x 5.5mm x 5.5mm)
g = 1mm

and it give a force of 78.598 N.

Clearly I have done something fundamentally wrong, but what?

Could it be the steel bolt?

I've looked for an iron substitute but couldn't find anything except old nails with a large taper.

What would happen if I tried a 3mm diameter neodymium magnet?

Thanks, Andy


texts: How much do people charge for EE R&D work?

texts:
My software startup is considering a project for a client that has a significant hardware component: a custom device with GSM, GPS and CAN connectivity for use inside a vehicle. We'll design the board ourselves (we have hardware experience), and we'll have to research CAN codes for locking/unlocking car doors, produced prototypes and write the firmware from scratch.

We'll soon have to negotiate a price for the R&D (calculating the per-device cost will be easier), but we don't know what is typical in the industry. How much should work like that cost? I'm just looking for a ballpark figure.


texts:
I built the following preamp to use with guitars

Basically the idea is to keep it on a single rail so that I can use it off the same battery with this power amp
https://www.eleccircuit.com/bridge-amplifier-bcl-18w-by-tda2009/
The Power amp is working fine, and the preamp seems to work fine when I run it across an oscilloscope, but when I connect a guitar to the preamp and the preamp to the power amp there is a repetitive thumping sound. The thumping sound dissappears if I put a 10k resistor between the output of u2 and ground but only on an 8 ohm speaker. If I use a 4 ohm speaker the thumping is still there. Also with the 8 ohm speaker and the 10k resistor when I turn the volume down on the guitar the hum of the system increases. Can anyone see what I'm doing wrong here?
Also, unrelated, but I want to add a volume pot into this preamp circuit but am unsure where to put it without affecting the input impedence which I want to keep high.
***UPDATE: So it's taken me ages to get back to this project, but today I went through and tried all the suggestions below. Still when I connect the 4 ohm speaker it is not working. With an 8 ohm speaker now everything is okay. Can anyone suggest why I would have this problem with the lower impedance speaker?


texts: How to measure the total current driven in a building by observing the electricity meter?

texts: Electricity meters show power. How can I measure roughly how many total current in amperes is driven at an instant in a building including a 3 phase AC motor?


texts:
While studying the re model of a common emitter transistor i found these two different models that are considered equivalent. But i do not understand how they can be equivalent when in one figure current source is connected directly to ground and all the current from the source goes to R(L)//R(C) while in other figure current from current source is divided through a node

and only a portion of the current from the current source goes to R(L)//RC.


texts:
I have a 24V power supply line which I would like to transform to 5V (<1A) in order to supply my chips. Voltage regulators would waste a lot of energy in this range. I looked at some datasheets of such switching regulators e.g. TSR1-2450. On page 1 it is stated that an efficiency of 92% can be achieved.
How is the energy loss calculated?
I would understand it that way: Regulation from 24V to 5V@1A results in 5W maximal output. With 92% efficiency the circuit would need

5W*1.08 = 5.4W


texts:
Ok,  I haven't done any experiment and please don't get all technical "what type of scales are used"

But here is my question

Does the weight of and electromagnet change when it on?

Here is my though!  If you place an electronic magnet on a weighing scale and weighed it.  Would the weight change when you turned it on.

Would the magnetic field generated by the electromagnet attract or repel against the earth magnetic field changing its weight in a Positive or Negative direction

What's your thoughts.  Dose magnatisum play a role in gravity?


texts: Calculate the gain of the instrumentation amplifier for an input current I

texts:
I'm a little confusing to calculate the gain of my instrumentation amplifier due to different variables and conditions that may influence the gain.

I am creating a project, which needs to inject a 1mA electric current into the patient's body through 2 electrodes (Current Electrodes), receive this signal through 2 other electrodes (Voltage Electrodes), and amplify this signal, which will be sent to an AD converter.

The 1 mA electric current will be produced by a voltage controlled current source, the voltage used in voltage controlled current source will be a sinusoid of 1.98V pp (With a frequency sweep from 1KHz to 100KHz) with the voltage ranging from -0.99V to +0.99V.

The instrumentation amplifiers used in the current source are of type AD8606 (Analog Devices), with a single supply GND and + 5V.
The instrumentation amplifier will be INA118 with a single supply GND and + 5V (GND on pin 4 and 5V on pin 7).

Two questions:

1) For example, for a gain equal to 2 in the INA118 (Rg = 50KOhm), what will be my expected output voltage? Remembering that:

The gain of the instrumentation amplifier is 2.
Its power is single supply + 5V.
The input will be 1.98V pp in 1mA.

2) Another detail, my AD converter only receives positive signals, so I need to compensate the AC component of the output of my instrumentation amplifier, I intend to do this by adding + 2.5V (Vdd / 2) on reference pin 5. In doing so, what will be the Expected value of my output voltage?

My biggest problem is to understand the difference between the gain applied to a voltage, and the gain applied to a current, because I am not applying the voltage directly as it is normally done, I am applying through a current source.

The schematic is very similar to this:

I will use o AD5933 and a HPF (High pass filter or Capacitor Block DC), in the output of the HPF, the voltage will be 1.98V pp (-0.99V to +0.99V). The current source use two opamps (AD8606 with single supply +5V), the outputs of the current source (E1, E2) are the 2 current eletrodes, Z represent the patient's body, and E3, E4 are the two voltage electrodes. The AD5933 is a Sine wave generator and a ADC.

Thank you so much!


texts: Why most non-invasive current sensors have a minijack at the other end?

texts:
If I search on google for non-invasive current sensor and click on the images tab, in most cases, I see a minijack at the other side of the wire.
What is the reason for this? Is this minijack supposed to be connected somewhere specific?


texts: MOSFET won’t turn-off at low drain current

texts:
I am trying to design a MOSFET driver circuit for a bi-directional DC/DC converter. The load current is about 17A rms Max. Max input voltage will be about 54V DC. The image below is not the whole circuit obviously, just the driver for highside PMOS.
I am not using a bootstrap circuit and NMOS/driver because in some situations I would like the MOSFET to be permanently on.
Now it is not really a problem but when my load current falls below about 2A, the load voltage wont go all the way down to 0V anymore. My guese is due to drain-source capacitance, but I really have no idea. Anyone that can explain this phenomenon to me?
Here is my circuit:

This is the output current and voltage for a large load (R8=5.86 Ohm):

Input signal (V4) and MOSFET output voltage for a large load (R8=5.86 Ohm):

This is the MOSFET switching voltage and current for R8=5.86 Ohm:

Vgs for R8=5.86 Ohm:

This is the output current and voltage for a small load (R8=1k Ohm):

The MOSFET switching voltage and current for R8=1k Ohm.

Vgs for R8=1k Ohm:

I uploaded the LTspice circuit here.


texts:
Is there any material/device invented to quickly connect SOIC-14 like integrated circuits to, eg, breadboard? I am aware of adapter boards, but what if I want something without soldering? (I am not speaking of very high frequencies and too complex SMDs)

For example, if I remember correctly, I saw similar technology used for small LCD displays (where some kind of resin and evenly spaced wires provided very fine connection from the board to the LCD), so I guess, this kind of technique is possible. SOIC 14, in this example, would require two such  "wired pillow" connection terminals, which can be mapped to pins and/or wires.

Is there anything like this existing? Or maybe something with similar purpose, but universal enough to be useful with several cases?

UPDATE: There are prototype boards in existence, which make it much easier (and cheaper) to work with SMDs, eg http://www.whitewing.co.uk/protoboard.html . I wish, there were more such boards available for all kinds of SMDs.

UPDATE2: Actually, I have found anything I needed here: http://www.proto-advantage.com/store/ It seems, they have adapters for nearly everything. ZIF sockets, proposed in the answer, are also quite convenient in use.


texts: Why the body of a gas truck is grounded?

texts:
So there is a gas station near my place that was on fire. I asked one of the workers after this incident about the cause of fire and it appeared something was not right with grounding. Does anyone know the reason why people  ground  the body of a gas truck while filling a tank ?

Also this happen when electricians work on transmission lines .


texts:
I am currently doing a design where I basically have two different types of (digital) signals. The first signal group is fully differential (P/N pair). The other group are single ended signals referenced to ground.

I would like to transfer both these signals via Twisted Pair cabling to another board. The cable producer specifies that the twisted pair cable has a (differential) impedance of 100Ohms, which is what if perfectly fine for the differential signals.

For the single ended signals, lets assume I have an output driver impedance of 50 Ohms and an input impedance of 50 Ohms as well so what I would basically want is a cable impedance of 50 Ohms.

How is this issue addressed in the real world? Is this an issue at all? Is the differential impedance of 100 Ohms "the same" as a single ended impedance around 50 Ohms?

What I understand is that a typical coaxial cable has an impedance of around 50 Ohms, but what about single ended signals on a twisted pair cable?


texts: STM32: Difference between HAL_xxx_Init() and HAL_xxx_MspInit()

texts:
When using the HAL (Hardware Abstraction Library) for any of the STM32 micro controllers:

For a given peripheral, why do you have to call an HAL_...init() , as well as a HAL..._MspInit() - why are several 'inits' separated?


texts: Is my reasoning about an ATMega328p connected to equipment requiring an open-drain pin correct?

texts:
I am part of a research group that is developing a concept for a PCB for an external piece of equipment. This piece of equipment can be controlled with a microcontroller. It communicates to my microcontroller through I2C, using SDA and SCL pins. However, it uses another pin; they call it an "interrupt pin" and it allows slaves to send commands to the master. The external piece of equipment states in its interfacing description that this interrupt pin should be controleld by an open-drain pin on a microcontroller. Fair enough.

Our microcontroller is an ATMega328p with Arduino bootloader. In prototyping I have abused Arduino's pinMode to emulate open-drain:

void setup ()
{
  digitalWrite (pin, LOW) ;
}

void loop ()
{
  ...
  pinMode (pin, OUTPUT) ; // drive pin low
  ...
  pinMode (pin, INPUT) ; // hi-Z state
}

But as you probably know, this results in odd waveforms when the signals are checked with an oscilloscope. In the thread linked, the guy who ran into the same issue added an external 10k pullup to the pin and it solved his waveforms. It seemed to work correctly.

As none of us are very knowledgeable about this specific issue; are we correct in assuming that if a piece of external equipment requires control by an open-drain pin on "some microcontroller", this can be realized by switching INPUT/OUTPUT on an ATMega328p together with a 10k pullup resistor added to the pin?


texts:
I'm trying to draw a single pixel using DMA2D.
I did the following code it's not working at all.
LCD Display Width is 320, Height is 240.

I assumed a 1x1 pixel rect as a pixel.

  DMA2D_HandleTypeDef hdma2d;
  hdma2d.Instance = DMA2D;
  hdma2d.Init.Mode = DMA2D_R2M;
  hdma2d.Init.ColorMode = DMA2D_OUTPUT_RGB565;
  hdma2d.Init.OutputOffset = 320-1;

  if (PIXELWINDOW.pos.x <= PIXELWINDOW.end.x &&

      PIXELWINDOW.pos.y <= PIXELWINDOW.end.y) {
      HAL_DMA2D_Init(&hdma2d);
      HAL_DMA2D_Start(&hdma2d, c, (uint16_t)OLED_BUFFER[0] + (PIXELWINDOW.pos.x + PIXELWINDOW.pos.y*320)*2, 1, 1);
      HAL_DMA2D_PollForTransfer(&hdma2d, 10);
  }


texts: Protect device from losing power when to much current is drawn

texts:
I use an EVX 3014 RC ESC (BEC provides 5V & 1.5amps) and I'm worried that to much of the current will be drawn to the motors that not enough of it will be available to the raspberry pi computer (Rev 1 Model B) on board the car. Will the ESC provide enough power through the BEC to the pi at all speeds, if not how can I give the pi a secure power supply?

EVX 3014

raspberry-pi b rev1


texts: Why isn't software USB/TTL on ATmega328p working?

texts:
I've tried to implement an AVR-CDC project. I found this website which is recommended by V-USB (I know it is pretty old project.)
I drew this schematic:

I've built a PCB basef on it and then I've uploaded the ATmega328p HEX file into the chip.
The problem is when I connected it to my PC, it dorsn't recognize anything and nothing appears as USB or ttyX (I'm on Ubuntu) or when I connect it to Arduino Pro Mini through RX-TX-Vcc-GNF pins nothing appears.
I've tested USB port is fine because it powers the main board. The ATmega328p chip is Ok because I can program it through SPI connector.  The Arduino is fine because I can program it with another USB/TTL module.  The PCB is fine because I did a continuity test on it.
Any help would be appreciated.


texts:
I have an e-bike battery of capacity: 4.3Ah (Li-ion). Specifications: http://industrial.panasonic.com/cdbs/www-data/pdf2/ACA4000/ACA4000CE285.pdf

For charging, the label on battery says "Rating 25.9V 4.05Ah 105Wh"
and charger output is DC+29.2V 2.0A

Due to its usage and age, I want to replace 18650 cells in it.
Most probably cell capacity is 2150mAh. Total 20 cells.

I wanted to know if I can upgrade the cell to something like Panasonic NCR18650B which is approx 3400mAh so that overall battery capacity will be increased. If it is possible, generally does this type of upgrade requires any circuit change in battery? Same charger ok?
NCR18650B specifications: http://na.industrial.panasonic.com/sites/default/pidsa/files/ncr18650b.pdf


texts: Running 2 5V USB battery power packs, Can I use them in parallel

texts:
Can I run two 5v power packs in parallel to give me more mAh's (Time)? Or will one try and charge the other?

Example

I.E. connect both 5V lines together, both GND lines together to my device


texts:
I have a question : The electron beam in TV picture carries \$10^{15}\$ electrons per second, determine the voltage needed to accelerate the voltage needed to accelerate the electron beam to 4W
I need help with verification of what I've done.


texts: What happens when a MOSFETs gate is left open?

texts: I was working with an interface with a MOSFET and I ran into a case where high impedence might be an input to the MOSFET's gate, essentially leaving the gate open. Would the MOSFET exhibit the same electrical & physical behavior as if the gate was connected to GND?


texts: How can I find whether RF transmitter and receiver are not in range?

texts:
Suppose I have a device A with RF transmitter and device B with RF receiver with range 10 meters.

Is there a way a A gets notified when B is out of range? Do we have to keep checking from A at regular interval that B is accepting signals or not?


texts: A monostable multivibrator using two NPN transistors works as desired in LTSpice, but in reality is very different

texts:
I designed a simple monostable multivibrator to extend a pulse of width \$\approx\$ \$1{\mu}s\$, to \$8ms\$ (to illuminate an LED when something happens on a bus).

This is the circuit here, and the output as simulated with some background noise in LTSpice.

Is there anything obvious as to why it does not work? I debugged the circuit meticulously for potential problems in assembly and cannot find any.

What I see at the output potential is essentially the same thing that is input. A pulse seems to propagate all the way to the output node, except that instead of being \$Ground\$ to \$V_{cc}\$, it's around \$Ground\$ to \$V_{cc} - 1.0V = 2.3V\$ and its pulse duration mimics the input very closely. I cannot adequately explain this. I would have assumed that if it worked, this potential should be around \$3.3V\$ as the right transistor is not biased and may only develop some weak diffusion. This means the potential that appears at the output should be the result of the divider of \$R_{O,2}\$ and \$R_2\$ with \$V_{be,q2}\$ not affecting this potential, this gives around \$3.20V\$.

The NPN transistors I am using are inside a BC847BPN package (SOT363) if that suggests anything I have missed. Also in reality, the resistors used for modelling the inputs for \$V_{cc}\$ and \$V_{noise}\$ are not present, and \$V_{noise}\$ is just to aid in the simulation.

\$C_3\$ was intended to be \$100n\$ but in reality I measured it to be \$180n\$, hence its odd value in the simulation. The voltage drop across the diode is \$0.7V\$ measured in reality also, and its reverse breakdown is 45V and supports \$200mA\$ in the forward direction.

Just to reiterate, my input pulse is positive from \$Ground\$ to \$3.3V\$ and I need the output to also be close in magnitude. I can pass it through a Schottky if need-be.

Image of the real circuit. The DO-323 region has the 7 passives and diode, the SOT-23 region has the two transistor packages BC847BPN on its top right and middle top locations.

The photo of the circuit made up


texts: Orientation of an electrolytic capacitor in a circuit

texts:
I am attempting to debug the following circuit. Looking at the schematic, starting at Vin on the left of the diagram, I want to figure out if the 10uF capacitor is the issue with the circuit.
This capacitor has no indication for how the positive or negative sides need to be oriented in the circuit. How cna I determine which way the capacitor is supposed to be oriented in the circuit?


texts:
I am trying to build a bluetooth audio headset and decided to use CSR8645 chip, but while trying to understand diagram of this chip i couldn't identify one part of it.
I am uploading picture suspicious part inside red area , so could you plese let me know if you have any clue about this part.

Best Regards


texts: How does filter rectifier circuits work?

texts:
The voltage coming out from rectifiers is not smooth and a filter rectifier circuit is used to  smoothen it for more stable constant DC voltage. Consider a RC-filter rectifier. In my school it was told that the capacitor is capable of passing only the AC current through it and the DC current comes out through the other branch.

But, I'm not getting any intuition on it. How does it actually work? The AC or DC part of the current all are the same part of the final current coming from the rectifier. So, going into the level of the conductors and electrons how does this process work?


texts:
I'm trying to design a guitar distortion pedal, though it is not working as expected.
The built circuit behaves differently than the simulated LTspice model.
I currently do not have access to a scope, so right now I have no idea what's going wrong.
For some reason when I use the test pedal, the only distortion comes from the op-amp (clipping at the rails), however I would like for it to clip from the diodes.
I'm not too sure what's going on.  If the voltage is high enough to reach the rails, it should clip from the diodes, and this is also what happens on spice.
Any help as to why this is happening would be much appreciated.
The circuit left of "in" simulates the guitar pickup, and the last resistor simulates the amplifier (roughly.)


texts: LM2576 vs modern step-down switching regulators - EMC requirements and other differences

texts:
I'm looking for some cost reduction in my design and I want to replace TPS54302 with LM2576 or LM2575.
In my case - switching regulator works as a pre-regulator with 12-24V input and ~6V output, followed by 3.3V 200mA linear regulator and 5.0V 1A LDO. Additionally circuit with about 30 LEDs (15mA each) is powered directly from pre-regulator.
TPS54203 features (from datasheet):

LM2576 features (from datasheet):

So the main difference (regarding EMI) is that TPS54203 has frequency spread feature, which "reduces EMI" (or more correctly - spreads EMI over some frequency range).
Another difference is that TPS54203 works near 400kHz and LM2576 works at fixed 52kHz.
And third main difference is efficiency I guess. I don't worry about this, device is not battery-powered and there will be no problem with heat disspation.
Questions:

Shall I worry about EMI/EMC when I replace TPS54302 with LM2576?

Is there something else (besides EMI) that should I worry about when I replace TPS54302 with LM2576?


texts: Over-voltage protection for mini-computer

texts:
I am working on a mobile robot and have damaged 2 RPis as a result of what appears to be a transient over-voltage situation. Please see the attached drawing of the basic setup. The failure is not repeatable so its tricky to figure out what exactly is causing it (after the first failure, I changed the DC-DC converter). Is there anything that appears to be missing? The only common action between the two failures I can recall is the e-stop button is used. The motor controller from Roboteq (FBL2360) allows regeneration but it has been capped at 35V which the DC-DC converter is able to handle. These over-voltage situations also damage the USB devices connected to the RPis and there are some expensive components so any recommendations to further protect those?
Here's the DC-DC converter


texts:
I need to power a device with an AC square wave with no DC bias. I have an input DC signal from a microcontroller from 0-5V.
I need to use the input signal to create a variable amplitude AC square wave from -5 to +5V. I can use a 555 timer to create an astable oscillator and op amps to double the input signal, but I don't know how to shift it to +/-5 volts. I also have some IRF540 MOSFETS I could use but I'm not sure how to vary the output voltage through the input from the microcontroller.
The output AC signal is 2khz and 50% duty cycle. It's important the signal has no DC bias as this may damage the device.


texts: Avoiding confusion between no input and a zero in binary?

texts:
Suppose I'm transmitting data through FM where 0 is 2Hz and 1 is 4Hz. The transmitter is transmitting 2Hz when there is no input. If I fed the recieved binary to a UART port of a microcontroller, how would the microcontroller differentiate between no data and 0?

This becomes relevant when transmitting ASCII characters for instance. Suppose the following string:

01000110 01101111 01101111 01100010 01100001 01110010

Because I've added spaces, we could translate this to:

Foobar

But to a machine the string would look like this:

010001100110111101101111011000100110000101110010

How would you create those "spaces" so you don't get ASCII characters messed up when you're receiving binary?


texts: Is is possible to calculate the MTBF or Failure rate from a given datasheet when manufacturer have not given these details?

texts: As there are new components getting added to the mouser or digikey, is it possible to calculate the failure rate based on some pre known facts and values? some vendors don't reply for weeks and I can't wait that long for MTBF value.


texts:
Pardon the potentially silly question.
I have been reading about photovoltaic (PV) cells and max power point tracking (MPPT).  From what I understand, a MPPT module can use a DC-DC converter to change the voltage on the PV's terminals to its corresponding MPP voltage (Vm).  My question is, how are the PV cells terminal voltage clamped to Vm?
For example, the PV terminal voltage is 20 V and Vm is 17 V.  Can we create a circuit like this to achieve MPP?

PV 20V->DC-DC Converter 17V -> Other stuff

This means that the PV terminal voltage is still at 20 V.
Or, do we need to accomplish this?

PV 17V -> Other stuff

Where a DC-DC converter forces the terminal PV voltage to be 17 V.  If this is the case, how is this actually done?

I feel like I'm missing something really obvious.


texts: Is there a limit for the max charger supply current for this power bank?

texts:
To charge this power bank 5V supply is needed through micro USB. It says FOR the power bank the charge current: ≤ 2200 mA.

What does that indicate for the power supply max current which charges this power bank? Does that mean one should use a 5V supply/adapter with Imax>2.2A or Imax<2.2A?

(Normally when we use a supply for a device we apply exact voltage with minimum current the device needs or more. For example a device with input sepcs 5V 2A would work fine with a supply rated for 5V 4A. But it wouldnt work for 5V 0.5A)

But in this case it is not that clear to me.


texts: BJT Differential Amplifier with active load Analysis


texts: How does this DC Electric Motor Control Circuit Works

texts:
I'm trying to figure out how does this DC motor controller circuit works. The circuit originally controls 2 DC motors for lifting a table. I extracted section relating to one motor only.
I added my own analysis with red text of what I think the circuit is doing.
My Questions
1- Is it a feedback loop circuit that I have identified? if yes, how does it work? any references?
2- Why is the PWM signal connected to multiple transistors and MOSFET just to drive IOUT to ground ?


texts: How to measure a signal that uses a virtual ground using Arduino

texts:
I've created an EEG system that measures the potential difference between:

1) The differential amplification between EEG voltages.
2) a virtual ground between two 9V batteries.

I'm trying to measure the output of this EEG system using an Arduino, but I'm not sure how to do this since the Arduino and the EEG circuit are both using different grounds. (there is a gronud electrode plugged into the virtual ground as well)

Does anyone know how to solve this?


texts: Solenoid Actuator (Linear) Force Calculation

texts:
what is the simplest form of law to calculate Solenoid electromagnetic force.
i.e. a relation between force and electric current
knowing that i'm given a Force constant with measuring unit N/A^2 (newton per ampere^2)


texts:
I'm using this script to run the simulation

#vlib work
view structure
vsim -t 1ps -voptargs=+acc -L work BiPhase_tb
do BiPhase_wave.do
run -all

From what I see the simulation time is 1 picosecond, but the siumlation won't stop at that and just continues running (this is my understanding from the status bar underlined in the screenshot below):

How do I make the simulation time a specified duration (e.g. 1ps)?


texts: I'm making a simple dark sensor project with a light dependent resistor (LDR) and I want to replace the LED with a buzzer but it doesn't work

texts:
I replaced the resistors with small ones to give the buzzer more current,but itstill doesn't work. I checked my buzzer and it's working fine.  The circuit works perfecly with the LED in the breadboard and the simulation program.
I'm using a TMB12A05 buzzer.


texts:
I am understanding the working of a buck regulator LT3845 from linear tech. The datasheet is - here.

My doubt pertains to the SHDN pin on the IC. The SHDN pin is connected to the Vcc via a voltage divider and requires approx 1.2-1.3V to turn the IC on. Now, the SHDN threshold varies with respect to Temperature. There are 2 graphs of the Shutdown Threshold vs Temperature (a rising and a falling of Shutdown threshold). What exactly is mean by Shutdown Threshold (rising/falling). The graphs are given in page 5. A screen shot is placed below -

What does this pertain to ? Shouldnt the behaviour/voltage for the SHDN pin be the same (be it rising or falling) ?


texts: Resistance measured low in constant DC voltage supply

texts:
I have a DC power supply, which I have connected to an electrical circuit on a breadboard whose total or equivalent resistance is to be measured. The power supply comes with a voltage and current display. Now whenever I measure the resistance by taking the ratio of voltage (V) and current (I) from the display, the resistance $$R=V/I$$ is found to be smaller than the actual one (tested theoretically and also by measuring using a multimeter).

For instance, as shown in the image here, the voltage (V) is 14.29 Volts and current (I) is .055 Amperes, which means resistance is R=V/I=259.82 Ohms where my actual resistance should be around 271 Ohms.
What can be majorly responsible for this discrepancy, the display's voltmeter circuit's internal resistance? Or can there be a more complex reason since the circuit is supposed to have digital elements inside (can any research paper be cited in that case)?


texts: Feedback fraction of Colpitts oscillator

texts:
Here I have a Colpitts oscillator:

The feedback fraction is C1/C2.
However during an LTSpice simulation if we set C1 = C2 the oscillation is not underdamped. How is this possible since we will get a feedback fraction of 1 and the voltage gain of a BJT is always less than 1 so the oscillation must die out?


texts:
In the schematic of arduino due there's a mosfet between of "USBVCCU2" and 5V line.
http://arduino.cc/en/uploads/Main/arduino-Due-schematic.pdf
I refered to T2 (FDN340P) P-Channel Mosfet. What's the usage of that mosfet?


texts: Startup current of an induction motor when using VFD

texts:
A 3-phase AC induction motor has the following ratings:

rated power: 130kW

input power: 140kW

rated voltage: 3x400 V

rated current: 270A

supply freq: 50Hz

there is no soft-start

The motor will be used with the following variable frequency drive (VFD):
http://www.clrwtr.com/PDF/Vacon/Vacon-100-Application-Guide.pdf

In this VFD case will the motor's startup current be more than 270A? The motor will sometimes run at its rated current. But my concern is: Will the motor drive more than 270A at start-up or will the VFD take care of that? Because Im afraid to damage the surrounding system with too high currents. Does VFD take care of the startup current problem?


texts: Electronic Circuit Simulator API/Libraries

texts:
Are there any Electronic circuit simulator libraries/API that I can use to construct virtual circuit simulators like SPICE etc? My main research area is not Electronic simulation since I'm a Computer science undergrad so I have to give priority to Software Engineering aspects.

thanks


texts: AVR ATmega644p: can't clear OC0A pin on CTC mode

texts:
I made an IR blaster for controlling TV (on and off) based on ATmega644p. I am using Timer0 in CTC mode to generate 38kHz waveform.
This is the code:

#include <mega644p.h>
#include <delay.h>

void start_waveform(void);
void stop_waveform(void);

// IR singal pattern
int ir_signal[] = {
    1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, -1,
    1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, -1,
    1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, -1,
    1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 2
};
int index;

void main(void)
{
    // Pin input for button (PB0)
    DDRB &= ~(1 << 0);
    // Pin output for IR LED (OC0A) (PB3)
    DDRB |= (1 << 3);

    TCCR0A |=
        // Toggle OC0A at compare match
        (1 << COM0A0) |
        // Mode 2 CTC
        (1 << WGM01);

    // Make 38kHz output frequency (F_CPU = 16MHz, Prescaler = 8)
    OCR0A = 25;

    while (1)
    {
        // If button is pressed
        if (!(PINB & (1 << 0)))
        {
            // Transmitt IR signal
            for (index = 0; index < 64; index++)
            {
                if (ir_signal[index] == -1)
                {
                    start_waveform();
                    delay_us(280);
                    stop_waveform();
                    delay_ms(45);
                }
                else if (ir_signal[index] == 0)
                {
                    start_waveform();
                    delay_us(280);
                    stop_waveform();
                    delay_us(760);
                }
                else if (ir_signal[index] == 1)
                {
                    start_waveform();
                    delay_us(280);
                    stop_waveform();
                    delay_us(1780);
                }
                else if (ir_signal[index] == 2)
                {
                    start_waveform();
                    delay_us(280);
                    stop_waveform();
                }
            }

            delay_ms(500);
        }
    }
}

void start_waveform()
{
    // Start waveform at prescaler = 8
    TCCR0B |= (1 << CS01);
}

void stop_waveform()
{
    // Stop waveform
    TCCR0B &= ~(1 << CS01);
}

This code works for turning on and off the TV, but the problem is; sometimes after the IR signal end, the IR LED is still on. I have tried adding code to make sure the PB3 is turn off using this code, but it is not working:

void stop_waveform()
{
    // Stop waveform
    TCCR0B &= ~(1 << CS01);
    // Make sure PB3 is turn off
    PORTB &= ~(1 << 3);
}

I am curious what's wrong with this code?


texts: Gain-bandwidth product proof for open loop/closed loop opamp

texts:
On the forum, post #12, Ghar claimed that the proof gain-bandwidth product from wikipedia is awful and he gave another proof but with feedback.

https://en.wikipedia.org/wiki/Gain%E2%80%93bandwidth_product
http://forum.allaboutcircuits.com/threads/op-amps-and-gain-bandwidth-product.43799/

The wikipedia proves gain-bandwidth product constant for open-loop opamp while Ghar proved for closed loop opamp.

Could you please tell me that if the wikipedia proof is wrong? I don't see any thing wrong with it. However, reading Ghar's post makes me confused.

I attach the Ghar's post in the image below just in case some member can't access it.

Note: Let's consider single pole opamp only.
This site also gave the same proof as wikipedia.

http://masteringelectronicsdesign.com/why-is-the-op-amp-gain-bandwidth-product-constant/


texts: Does this VCO produce a sine wave or square wave

texts:
I'm looking at the datasheet for the analog devices hmc431lp4 voltage controlled oscillator, and I can't tell if its output waveform is a sine wave or square wave. The datasheet doesn't label the oscillator as being harmonic or relaxation. I'm wondering because I am trying to understand a homemade radar system I found online. Do FMCW systems like this project require a sinusoidal RF signal to operate?

Link to datasheet.

Link to project I'm looking at.


texts: Can a power surge pass through a household DC power adapter?

texts:
I assume that all DC adapters for household electronics use a bridge rectifier.  Is that (still) correct, or are other designs now in common use for household AC-DC converters?

Without explicitly adding surge protection components and circuitry (MOVs, etc.), do any of these common AC-DC converter designs do anything to attenuate voltage spikes, or otherwise isolate the DC output from spikes on the AC side?  If so, how?


texts: Filter construction: Nonperiodic frequency response

texts:
I am confused about the construction of filters for non-periodic signals which attempt to limit the output to a certain frequency range(by frequency I mean with respect to the Fourier Transform).

How are they constructed? How do you even find the non-periodic frequency response of a filter?

Lets say I want to construct an along filter which limits the output of an aperiodic signal to a certain frequency range(approximately) which has an impulse response approximately like the Sinc function.

What does it look like? How is it done?

Thank you for the information.


texts: Many Data from Different Transmitters to Single Receiver Simultaneously

texts:
In my Project transmitters constantly transmit some data. I want to receive all the data in single receiver at the same time. I searched about RF transmitter and receiver. But Many to One not possible at the same time in RF. What type of transceivers I can use? I can't use wifi coz in my projects the nodes adds or leaves dynamically and wifi takes a moment to connect.

Is there any type of transceivers can I use? I am new to Electronics and I don't know much about it.


texts:
I ordered some Pro Minis however get some WAVGAT clone thingies. The first problem was it is running too slow (4x slower) when compiling with default "Pro or Pro Mini" board profile. Serial however works in this situation but at 2400 baud instead of 9600 baud (Serial was initialized with 9600 baud).

Then I download the board definitions for the WAVGAT clones and select "WAVGAT Pro Mini". After uploading the same code, the clockspeed looks okay however no serial output at all (tried every baud speed available at the serial monitor).

Any idea how to fix this?

Here is the sample code:

#include <Arduino.h>
void setup()
{
  // put your setup code here, to run once:
  while( !Serial ) {}
  Serial.begin( 9600 );
  pinMode( 13, OUTPUT );
}

void blinkLed()
{
  digitalWrite( 13, HIGH );
  delay( 1000 );
  digitalWrite( 13, LOW );
  delay( 1000 );
}

void loop() {
  // put your main code here, to run repeatedly:
  blinkLed();
  Serial.println( "hello" );
  delay( 1000 );
}

Update:

The board I have has a WAVGAT AVGA328P MCU, which is actually a Light Green LGT8F328P MCU instead of a the original Atmel/Microchip ATMEGA328P. This MCU can run at max 32Mhz instead of max 16Mhz.


texts:
I am curious, generally speaking, as to what are the physical processes behind the workings of a CPU. I understand that the reason why computers use binary is because it means that data can be stored magnetically by direction, or electrically by charged/discharged.

For example, if I have two bytes 01110000 and 00001111, what electrically happens when, say, the second is subtracted from the first?

(I understand that a fully-detailed answer to this would be company secret, but I am asking out of curiosity and not for anything specific to a given manufacturer.)


texts: Switched neutral option in switch datasheet

texts:
Looking at this datasheet for a mains switch, the 'preferred option' (5503 on the sheet) is called 'switched neutral'. I cannot see how both the live and the neutral can be switched with only 3 pins, as surely you need four (two for input live/neutral and two for output live/neutral) which leads me to believe that only the neutral is switched in this arrangement.

I also don't see how the circuit diagram makes sense, as if the mains plug is connected to pins 2 and 3 then this should just give a short across them when the switch is closed. If instead the mains plug is connected to pins 1 and 2 then only one of the live/neutral can be switched (depending on which one is connected to pin 2).

As only switching the neutral sounds like a terrible idea, combined with the lack of understanding of the circuit diagram, this leads me to assume I have misunderstood something quite badly. Any help you could give me in this matter would be greatly appreciated.

EDIT: The only way I can see the switch working properly is if we have the following setup:

      Pin 1          Pin 2         Pin 3
       (*)            (*)           (*)
       / \             |             |
      /   \            |             |
     /     \           |             |
    /       \         live          live
   /         \        mains         circuit
  /           \
neutral    neutral
mains      circuit

as when the switch is closed pins 2 and 3 become continuous. This seems to disagree with the answers below, where pin 2 is the common neutral pin. Have I misunderstood the answers as well as the datasheet?


texts: Starting sequence in PFC AND SMPS Design

texts:
In the design of power supplies, we often use Active PFC and downstrem SMPS, to regulate the output voltage, and  we often use IC controllers like MC33262 for PFCs and NCP1252 for AC-DC converters. These IC require a DC input voltage as VCC.
If we take the example of MC33262,that needs a VCC of 12V, and used as a PFC in a 230 Vrms in a main line to feed a flyback converter as downstream SMPS, how do we get this VCC=12V in the starting sequence when the only existent voltage is the full-wave rectified one ?


texts: Easiest / cheapest way to build a dc power supply in the 150VDC range

texts:
I am looking to build a power supply to power a 150 V DC armature motor that will pull a maximum of 4 A. The cheapest I have seen so far is the following on ebay.

I'm looking to build one myself but can't find anywhere online that will give me a guideline as to whats involved. Can anyone point me in the right direction


texts: How important is op amp supply cleanliness?

texts: Say I have a simple non-inverting amplifier op amp application as shown. The input signal is far from the rails. Now say the +12 and -12 V supplies are not ideal DC, but rather have lots of ripple or noise, causing them to go anywhere from +/- 12-13 V. What effect would this have on the output signal quality? Would this affect other applications? (again, the input signals not in danger of reaching the rails)


texts: What is a disable input for on a motor controller for?

texts:
I'm trying to figure out this motor controller I recently got and it has two pins called PWM / D2 and PWM / D1, disable inputs. I don't understand the description for them and don't know what they are for or how to use them. Will somebody please explain?

  PWM / D2    DEFAULT LOW - Inverted disable input: when D2 is low, OUT1
  and OUT2 are set to high impedance. A D2 PWM duty cycle of 70% gives a
  motor duty cycle of 70%. Typically, only one of the two disable pins
  is used, but the default is for both disable pins to be active.

  PWM / D1    DEFAULT HIGH - Disable input: when D1 is high, OUT1 and OUT2
  are set to high impedance. A D1 PWM duty cycle of 70% gives a motor
  duty cycle of 30%. Typically, only one of the two disable pins is
  used, but the default is for both disable pins to be active.


texts: Characteristics of a DC motor control system

texts:
I am designing a DC motor controller model. I have a second order system so the step response oscillates and overshoots the final value somewhat.

I have seen a lot of theory on calculating rise time, settling time, and overshoot.

My question is what effect do these things actually have on a DC motor?

Should I be focused on making the overshoot less or changing the rise time in order for the system to react faster?


texts: Naming convention for a voltage follower op amp

texts:
I have a voltage divider which creates a 1V signal that is sent to a voltage follower op amp.

This might be a silly question, but is there a well accepted naming convention for this very common type of circuit? "+1V raw" and "+1V" sounds a bit weird but I didn't know what to name these ports.

Since this is a very, very common circuit, I thought there should be some sort of unwritten convention on these?

Thanks


texts: How to power ESP8266 from changing voltage

texts:
So I'm very new to electronics of all sorts, have done some basic repairs but I'm interested in learning more.

The project I have in mind is to use the cheap and easily available Doit NodeMcu Lua ESP8266 ESP-12E to send me a push notification anytime the door buzzer is rung. I would like to embed this project inside of the internal phone housing in my apartment and use the wifi to send the notification.

My door buzzer seems to receive a voltage of 4.4v when idle, when the door bell is pressed that changes to 13.3v.

My questions are:

Can I somehow use the 4.4v to power the ESP? How do I safeguard it from the increased voltage when active? Some sort of voltage regulator that would still allow the buzzer to be rung?
How do I use this voltage change to create an alert? I know I can, but do I need additional sensors or will the ESP be able to handle it?

Here are some images of my door phone http://imgur.com/a/H0GJU

If anyone can draw me a fritzing diagram or similar I'd be very grateful.

Other information.

I'm using Pushover which I understand only allows HTTP (not HTTPS) with these units.
I live in Denmark.
I have access to a hackerspace for basic supplies.

EDIT: I think that a 3.3v voltage regulator IC would allow me to do the powering part, would you use a wire-tap style connector to add it in from the +ive buzzer wire?


texts: how to plot on the same bode plot a manual function plot() with function bode()?

texts: I have a a transfer function that I plotted manually using Plot(w,abs(f1(w)))(plotted for a digital filer since I dont have signal toolbox) and I have another function that I used directly bode(f2(s))(analog filter). I would like to plot them both in one bode plot?


texts:
This is my first 'real' PCB, since it also contains AC power together with a bit of DC it would be awesome if someone could check my design.
Description:
I'm building the MPCNC project and would love to connect all my devices / switches to a single pcb. The pcb will be powered by AC 230v and will reroute the power to different screw terminals through some 12v relays. I will be converting 12v from the 230v mains. Max current that will be 15A.
After my initial research I kept into account the following:

added enough fuses
all components are rated for the required current / voltage
trace width high enough for max 35C temp rise
kept Live and Neutral traces on different planes
created a copper pour on the top plane (disabled on the image to more clearly show the traces but you can see the red dash outline)
kept the 12v traces far enough away from the 230v traces
user clearance of 4mm for the copper pour to account for creepage
between 2 live traces where the distance was shorter I added a slot to prevent creepage

Should I do a ground pour on the bottom plane as well? If so, do I connect them through vias or through the ground terminal of my source terminal?
Already want to thank you in advance for any help!
EDIT: after the comments below I made the following changes.

Added flyback diodes to the coils of the relays
copper poured both sides for ground plane and connected both top and bottom ground plane to the ground terminal of the incomming source power

EDIT#2:

Added slots in between all the AC screw terminal ports for extra safety.
Increased the clearance in the top ground plane to 4.5

I'll be getting this produced soon after the last changes and a final double check from my side.
Thanks to @RonBeyer @rdtsc @Andyaka @le_top for the feedback, it's really appreciated!


texts: How does a TDM multiplexer "catch" all bits?

texts:
In time-division multiplexing, how do we make sure that there are no dropped bits?

Consider this example. Let's say we have a 4-to-1 multiplexer. Each input line is 200 bit/s. The unit of transmission is 8 bits, that is, each time slot has 8 bits, and therefore each frame is 32 bits.

So now the selector is at the first input, and because a time slot is 8 bits, the selector must stay on the first input until 8 bits are transmitted to the output. And after the first input has transmitted 8 bits, the selector will then switch to the second input.

But before the selector switch to the second input, the second input was already transmitting at the same rate, that is, although the line is open, it is still changing its state between high and low at the same rate. So therefore, before the selector switch to second input, 8 bits were already lost. And before it switches to third input, 16 bits were lost, and before the last input, 24 bits were lost, and so on.

What am I missing?


texts: What does frame, word, and bit mean on a FPGA

texts: I know that frame, word, and bit is some sort of address.  But what does that mean exactly?  The reason I am asking is because I am trying to render an image of a FPGA based frame, word, and bit addresses and data related to those addresses.


texts: What kind of time delay switch to choose to reverse motor for just a couple of seconds

texts:
I would like to know the following:

I have a motor driving a lead screw which transports a part either up or down.
When going down and something comes in the way a switch gets triggered by the obstical which stops the down movement until the obstical is removed (and the switch released). It will continue to go down until it hits an end switch which stops the whole thing.
All this works fine.
However, now I would like to reverse the motor if something gets in the way. So...if going down, something gets in the way I do not want it to just stop. I would like it to go up for 2-3 seconds and then continue to go down until it reaches the end switch which stops everything as usual.

So...I tried to find a time delay relay and noticed that there are quite a few options. A few I do understand and know I can't use them for my application. The other ones....I have to admit....I don't really understand how they work.

Could somebody be so kind telling me what kind of time delay switch/relay I have to choose and how to integrate it in to my current circuit.

BTW a programmable timer will start the down movement if in "on" mode. If timer turns off the motor reverses and the part goes up. Everything is 12V. A DPDT relay reverses the motor.

I hope I gave all necessary info necessary.

Thanks a lot!!!


texts: Measuring rotation over z-axis (gravity axis) inside an metallic duct

texts:
Well from my first research from the web I wasn't able to tell if what I need can be done.

The thing is, I need to measure the rotation over z-axis (yaw), in other words, to know the relative angle from the start point. The prototype goes down (z-axis negative direction) in the duct and it can eventually rotate, but it's not expected to rotate a lot or even fast.

So I found that it could be done with a compass but my prototype travels inside a metallic duct.

I tested my phone compass inside the duct and it went nut. So my first question is if the compass inside my phone is similar to the ones i found in IMU's and so.

Also saw some stuff about gyro and accelerometer, and I'm my way I've found a lot of info about Kalman Filter, but I'm kindda noob.

So my second question is, are the accelerometer and gyro able to measure yaw rotation. Even those "cheap" ones?

Where you guys think I should go from here?

Thanks in advance! (Sry for any bad English)


texts: Design to replace several jumper on a dense PCB

texts:
I'm working on the design of a board which include a lot of Jumpers (around 40). They are used in order to provide a possibility to connect or disconnect parts of the schematics. Signals are all analogic.

As my board is small and I already have quite a lot of components, I'm thinking of a way  to reduce the space used by jumpers (header with 2 pins , 2,54mm). It is possible for me to cut a group at  a time (lets say, unplug 8 jumpers at time).

I am thinking of using of CMOS switches, such as CD4066, with output control pins themselves drived by jumpers,  but I am not sure if it is the best way to go. I am also paying attention to the noise induced.

So my question is, do you have better suggestions to improve space reduction and / or noise induced ?

Additionnal information on signals used : +/-12 Vpp range, 15Hz-100kHz frequency range.


texts:
I've got some question about stack-up for 4 layer PCB.

My design is rather simple but due to many connections all arround PCB it couldn't be made with 2 layer PCB, this is why I picked 4 layer board.

My PCB is 1.6mm thick, with 1oz copper on all layers (incl. internals).

I'm using 1st layer as a power/signal layer with some locals ground pours that are connected with multiple vias to inner ground plane (which is 2nd layer // and whole 2nd layer is big ground pour without any slots [excl. vias clearance]).

Question is should I use 3rd layer as a power/signal and 4th as a big ground pour? Or should I swap it and make 3rd layer as a GND and 4th as a signal/power.

Due to many connections it's not possible to place power only traces on 3rd layer and signals on 4th because there will be some slots here and there and it will make my current loop alot longer, this is why I combined power and signal to one layer.
From mechanical point of view 1st and 2nd layer are adjacent do each other, similiar for 3rd and 4th.

I'm very curious which option could be better for me - I hope some of you might help ;)

PS: all component pads are located at 1st layer, there is no MCU's or any other high speed signals like clocks etc.
PCB is mostly occupied with power IC's like supervisors, LDO's and some audio stuff.


texts: Max acceptable resistance between IC ground and PCB ground plane

texts:
I tend to be very paranoid when it comes to making PCB's to the point where I try to use 50+ mil tracks for ground wires when routing the board. After, I fill the remaining space on the board with a ground plane.

I have come across a situation where I tried routing with fewer wire jumpers and even though routing is 100% successful, the ground pin from a DIP IC leading to some components consists of a 20mil wide track with a length between 5mm and 1cm before the track turns into a large ground plane (at least 200mil wide).

Since wires have resistance, I just want to make sure that such traces leading to ground planes are acceptable. If I could, I'd connect the DIP IC ground to a middle of a > 200mil wide ground plane.

So will my circuit be negatively affected by resistance/inductance if the ground of a DIP IC is connected to a large > 200mil ground plane through a 20mil track of 1cm length?

If no, then what's the maximum length I can use at 20 mils before noticing any bad effects?

My circuit will be done on a single-sided FR4 PCB with 1oz copper thickness, and My other PCB tracks and spacings are minimum 10.5 mils.

The power going through the circuit is 5VDC and the speed of operation is no more than 24Mhz.

I will add that the IC's used in my circuit are the 74HC types and cmos types.


texts: How to identify an unknown LCD pins from scrap, and use it for Arduino

texts:
I've got an unknown LCD from scrap, I don't know what each pin is.
can anyone help me with this?
it has 19 pins that 16 are functional.
also when I touch each pin with hot solder some signs turn on.


texts:
Which direction should the diode, cathode or anode, be facing for a car security alarm wire? Below is a diagram.

When the doors are closed, the wires are testing at 10.1 Volts, settings on the system could be set for either negative or positive door trigger input.

A system that tests wires as always on when doors are closed means it's a negative door trigger?


texts: FTDI code 10 - what can I do to resolve problem?

texts:
I am using the FT230X as a USART to USB interface on my boards. The first few work OK but then with the last one I get a Code 10 (cannot start) on my PC. It works fine on another PC when tried.

I have read this, and also updated, uninstalled and reinstalled the drivers. Nothing has been of any use.

Has anyone else had this problem and solved it?


texts: Replace in-series incandescent lamps in a makeup mirror with LEDs

texts:
This is my first post here.

My wife uses a makeup mirror which has 10 x BA9s in series. Each lamp is 3W 24V and since we are in Europe they run on AC 230V nominally (reading off a multimeter is sometimes 243V and even 248V).

A few months ago one of the original bulbs burnt out and the only local replacement I found were 24V 4W BA9S. Now every 4-5 weeks the 4W bulb burns out. I have marked the replaced bulb and it is always the one which burns out.

I thought of replacing all ten incandescent lamps with 24V LEDs from aliexpress. The ones I found are 2W and are meant to be used in vehicles.

My question is, would directly replacing the incandescent bulbs with LEDs lead to a worse situation if one of the SMD LEDs burns out?  Can I add some sort of resistor to the 4W incandescent so that the bulb voltage is somehow limited when the makeup mirror is switched on?

Thank you for any help.


texts: Current source for high current LED driver- 24Vdc/max:16A

texts:
I am working on designing a current source for a LED driver, which can work up to max:16A, as long as stays On less than 500msec.
Actually, the leds circutry is a Dome-light which is divided in 4 sectors. The 4 sectors have a common ground and they are trigger in PNP mode(24Vdc) individually.

I am using a current sense-resistor of 10mOhm resistance, between a n-channel mosfet`s source terminal and ground. The voltage measured on the current sense-resistor is feed to a differencial OpAmp which output controls the mosfet´s gate voltage. Nothing new here, it is the simplest current source circuit.
I am using a digital rheostat to create a voltage divider which sets the OpAmps reference voltage on the non-inverting terminal:

 Components:
 - TLV2372IP (Op Amp)
 - MCP4162 (Digital Rheostat)
 - STP55NF06L (Mosfet 60V,55A,Rds-On 18mOhm)
 - Current sense-resistor 10mOhm/0.1% tolerance.

Basic schematic:

simulate this circuit – Schematic created using CircuitLab

Questions:

The circuit drives the current to the leds array with stability. The power supply is a Meanwell DR-120-24/5A. Why can I get 4,6,8 or 15 Amps currents?If the power supply is rated 5 Amps max? (I didn´t have a higher current rated power supply at hand).
I found in internet that a N-Channel or P-Channel MOSFET High-Side Drive should be more stable and worth to try. But How? I don´t know how to go about it. Could you give me some ideas, please?

This circuit it is for using the Dome_light for a photometric stereo machine vision application. Actually, I am a machine vision programmer. I am not an electronics engineer, sorry for not giving more information.
Thanks in advanced

EDIT:IMPORTANT!

I have said that the circuit drives current with stability. But I know that this low-side driver will be unstabled if there is noise in the power supply or noisy enviroment like in a factory.It works steady only by chance.
 It is why I will need to change the circuit to work in high-side, I think... Also as you can see, in the real circuit I have used a voltage follower with a second opamp which gives the sense resistor voltage-drop to the differential opamp.


texts:
I want to design a capacitive proximity sensor to detect human presence at a distance of 10-15 cm.
Now I made my research on this type of sensor but everything that i found doesn't tell me about the size of such sensor, Can anyone help on how to calculate the size of the sensor?
The sensor Shape is circulaire and there is no constraint on it's size but the smaller the better.
I'm using a capacitive sensor because the system that i'm working on isn't fixed in one place, it is portable, so i don't need it to detect any object i only want it to detect human presence and the best option that i found is capacitive sensor which doesn't detect any object but only grounded objects, but if there is  any better option that would be great.


texts: What is a more effective shield for magnetic fields between 300 and 500kHz Solid copper or copper mesh?

texts:
I am working on a PCB that is very crowded, and has high gain amplifiers working between 300kHz and 500kHz

Typically I would use Mu metal or similar for shielding at this frequency, but obviously nobody makes Mu metal PCBs.  So I have a choice of solid or hatched pours.  External shields are not an option.

I don't have any controlled impedance tracks.

My only worry is the high frequency AC magnetic fields.  We use copper mesh shielding in our RF cages, which works rather better than I expected. I suspect this is due to the shorted turns.

I asked a couple of shielding companies, but they don't characterize their meshes for this sort of application.

Can someone point me to data that would indicate whether solid or meshed copper pours would perform better in this situation?


texts: How can I switch two wires using solid state relays?

texts:
I want to add a "reverse" function to a brushless motor ESC - in theory, it can be done by simply switching any two of the three output wires - I would like do to it via solid state relays, but I am not sure how to configure them - basically I want to be able to change which wires go where, so for example:

A --> B
C --> D

switches into

A --> D
C --> B

when I energize/de-energize the circuit

I am new to using solid state relays, however I would like to use them if possible. I believe that they do cross at 0, but at different time intervals, so I am not sure if I can rely on that to occur (I don't want to cause a short circuit by A --> C or vice versa) or how to ensure a "break before make" functionality such that both paths break before any new paths are made.

other possibly important specs: these will be handling 20A or so of current at ~14 volts

I am looking for guidance as to how I should wire this up or where to begin, even what specs I should look for in the relays.

P.S. - I would prefer an answer involving solid state relays.. I don't really want to use an H bridge that would need to support ~20A or so, nor drop ~1.4 volts, as that would waste a ton of power


texts:
I have a LoRa module called Adafruit Feather M0. I tried programming with Arduino in order to eventually display data. The data doesn't show up.
What I've done is that I've registered my LoRa device on the things network, and also connected this device from the things network to Yggio database. It uses MQTTS.
I then downloaded Adafruit boards etc in the Arduino IDE and ran the Feather M0 example code for "hello world" and modified this code with my device ID etc. But it still doesn't work to see the hello world message. The Yggio database is supposed to be connected to a gateway.
Does anyone know if I've missed something in order to display the data?


texts:
This is an interface circuit of Quadrature Encoder (A, A', B, B') with MCU. I cannot make sense of the working of OpAmps in this circuit. Is it some standard circuit for doing signal conditioning or is it doing some signal processing on the input signals? And what could be the purpose of OA and OB outputs?

edit:
better quality image added

edit:
data for possible encoders added as image.


texts:
I'm not sure if this is right site for this, but couldn't find better.

I've been given an task to create something that has light intensity like police beacon. I need it to be cheap, so I'm looking at dealextreme.com LED emitters , but there aren't any good user experience videos.

I don't know if the LEDs are right for this and how should I pick right one from these LEDs.


texts: Extending an RF ground plane outside a small PCB

texts:
I am making an RF PCB with a surface-mount antenna on it. It is a quarter-wave antenna, so the ground plane should also be as long as a quarter wavelength for good RF performance.

For example, a 915MHz antenna needs a ground plane 3.3 inches (8.4cm) long. Let's imagine my PCB is 1 inch wide. As a 4 layer PCB, it would cost $10 * 3.3in^2 = $33 at OSH Park. Every time I screw up a design, that's $33 more wasted.

I read an article by Antenova about tiny ground planes. I noticed this method for dealing with small ground planes:

  Your ground plane does not have to be your host PCB. A copper extension can be added. However, care must be taken not to loop this piece of copper around and underneath the existing ground. An example of this is a watch application. In this case, the ground extension can be run into the watch strap.

Copper extension? I have free access to CNC machines that can mill FR-1 copper boards! I can extend my ground plane past my tiny PCB... right?

Option 1: My first idea was to place a copper sheet (FR-1) under the RF PCB and use through-holes to solder the PCB to the copper sheet. Here's a side view and a top view of that stack-up:

That FR-1 copper sheet should extend the size of my RF ground plane. I then remembered this bit from the article:

  However, care must be taken not to loop this piece of copper around and underneath the existing ground.

Uh-oh. I now have a small ground plane (PCB layer 2) with a large ground plane (FR-1 copper sheet) underneath it! There will be about 60 mils (1.5mm) between the small ground and the large ground, with only the border of through-holes connecting them. So I had another idea.

Option 2: I can connect the copper sheet to the edge of my PCB with a row of through-holes. This will avoid overlapping any of the ground planes.

This fixes my last issue, but that edge connection is weaker and could easily snap.

The big question: does expanding a PCB ground plane with another copper plane tend to help or hurt RF performance? If so, can I get away with Option 1? It's my favorite.

I am just worried that the through-hole connections between the two planes will look like a big impedance bump to the RF signals. If through-holes are a bad choice, I can always get creative with land pads under the PCB, but those will make bottom-layer routing complicated.

I cannot find other examples of this practice on the internet. If you ask me to tune it with impedance matching, there is only so much I can do with a tiny ground plane. Also, getting access to a VNA would be a long and tedious process.

I can't use flexible dipole antennas because I have size and rigidity constraints.

This is a problem that I am trying to solve with creativity. I can't keep throwing money at my problems.


texts: For two clocked components in series, how do you ensure that the output of the first is captured by the second?

texts:
I'm working through the open Nand to Tetris course offered by Nissan and Schoken. I've just finished chapter 5, where we construct a 16-bit computer using a hardware description language and an instructor-provided hardware simulator.

Building a Modern Computer from First Principles - Nand to Tetris course

The CPU that we build for the computer uses three clocked components: a program counter, an address register, and a data register. You can see a diagram of the CPU on page 94 of the PDF below, and a diagram of the whole computer on page 97:

Chapter 5 - Computer Architecture

The output of the program counter connects to an external ROM which instantly outputs the instruction at the address specified by the program counter. If the outputted instruction is a "set address" instruction, it propagates instantly to the CPU address register, where it will be stored on the next falling clock edge.

My question follows. Both the program counter and the address register are clocked components. They are connected in series, with the output from the program counter feeding (eventually) to the input of the address register, like so:

 ___________________      _____________        ____________________
|  program counter  |    |  ROM 32K    |      |  address register  |
|         ^         |--->|             |----->|         ^          |
|___________________|    |_____________|      |____________________|

In a physical implementation of this circuit, how could I ensure that the ouput from ROM 32K would be stored successfully in the address register? Both components update on a falling clock edge. Imagine that the falling edge signal takes .2 clock cycles to reach the program counter, update it, and then propagate through the ROM, but takes .8 clock cycles to reach the address register. In this case, the output from the ROM would change before the falling clock edge reaches the address register.

The hardware simulator in our class solves this problem by storing new component states on falling clock edges and then propagating the new component state on rising clock edges. This ensures that component component B can capture component A's output before component A outputs a new state. I was wondering how this problem would be solved in a physical implementation.


texts: Using internal pull-ups for I2C on PIC18F

texts:
I'm working with a PIC18F46J53 and it was working quite well without any troubles.  Suddenly, I found a hindrance on my path.

I used RB4 and RB5 pins as I2C bus pins for communicating with an EEPROM (24LC256). And I pulled up the bus lines using external 10k on both SDA and SCL.

Whenever I initialize TRISB pins RB4 and RB5 as inputs a solid 3.2v will appear across them as I2C bus. But recently a problem popped up on my board: one pin, SCL, shows ~3.2V whereas SDA shows 0.8V - I2C,then, didn't work anymore. I cross checked the I/O pin configuration and when I enabled the internal pull-ups on the PORTB the voltage on SDA rose up to 2.0v and I2C worked fine with EEPROM.

  From the datasheet:

  RBPU: PORTB Pull-up Enable bit

  1 = All PORTB pull-ups are disabled
  0 = PORTB pull-ups are enabled by individual port latch values

To fix the problem I trust both pins SDA and SCL must have 2.8-3.2 V on the bus when configured as input. But it seems to be working with 2.0V on the SDA pin and 2.9V on SCL.

I would like your inputs to this problem if you have countered any difficulties like this before.

Where should I search to fix the problem? It's working for now but I trust I would have missed something in any case. When and how should one use pull-ups?  I have used both external and internal in this case to get I2C working.  What is the best way to do so?


texts: MOSFET delay time when transitioning between triode and saturation regions. Charging and discharging mosfet

texts:
Summary
For a mosfet, transition from saturation to triode region happens much quicker than from triode to saturation. Why?

Details
UPDATE: the load resistor was removed.

Fig.1: Schematic

Fig.2 Transient analysis

Notes:
1) BSIM4 SPICE model of MOSFET is used. Model parameters used (file cmosedu_models.txt) can be downloaded here.

Initially, the transistor is in saturation region (Vgs=350mV > Vth=280mV, Vds=V(out)=400mV > Vdssat=50 mV). Idssat=10uA.
After Vgs has increased, the transistor moves into triode region and its Vds goes down from 400 mV to 8 mV (below Vdssat).
Then, the opposite transition happens.
Transistion from triode to saturation takes around 6 ns, while transition from saturation to triode happens almost instantaneously.Why such a difference?

Appendix

Fig.3: Transistor parameters (for the operating point corresponding to Vgs=350mV).
Source: CMOS Circuit Design, Layout, and Simulation, Third Edition. R.J. Baker. Page 300.


texts: Turning on MOSFET and sensing to microcontroller input pin

texts:
I've got a stereojack, and I'd like to turn on an LED and also make an input pin to a microcontroller HIGH (For interrupt sensing).
The Vs is 3.3v
The LED has a Vf of 2.9v
The MOSFET has a gate threshold of 1v
I'd like to at least protect the GND pin from a short (Since the jack tip can touch the ring when inserting I've heard), so I've added a 1K series resistor to limit current.
Now this obviously makes a 3.3v -> 10K ->0.3v -> 1K -> 0v voltage divider. Am I right in thinking that this 0.3v LOW signal is ok? Both to keep the MOSFET Drain-Source closed and also for the microcontroller pin to be seen digitally as "LOW".
Thanks in advance!
EDIT: I've noticed there has to be a 0.7v drop across the diode! Hmm, is there a way to protect the input pin from any unwanted reverse voltage coming from the sleeve without dropping that voltage?
EDIT: I've removed the diode to remove that 0.7V and added a schottky instead
EDIT3: I've taken out the schottky, just added  a TVS to clamp any unwanted transient voltages to 3.3


texts:
I am using a CD4051 analog multiplexer to interface with ADC.

The system multiplexes from 8 identically setup inputs.

The voltage at an Ch X pin of multiplexer appears exactly as it is on COM pin until it is below about 1V.

However, as it increases above 1 V, the offset(voltage drop) starts to gradually increase with input voltage.

2V at Ch X pin leads to 1.98V at COM pin.

The supply voltage for both ADC and analog multiplexer is 3.3V

The Ron of analog multiplexer is 125 Ohms but there is virtually no current flowing through it, since the input impedance of the ADC is 6M Ohms.

I tried removing 1K resistor connecting COM pin and ADC input, but the drop voltage increased to 30mV from 20mV.

The result is that There is about 1 % nonlinearity. What is wrong and How should I improve it?