texts: Question about the Inrush Current in LDO

texts:
I have a doubt with inrush current limiting for an LDO. To understand that, I referred old literature of capacitors and others. I have some conflicting arguments which I need to clear out:

This is from Wikipedia:

  The current into a capacitor is known to be
      : the peak inrush current will depend upon the capacitance C and the
      rate of change of the voltage (dV/dT). The inrush current will
      increase as the capacitance value increases, and the inrush current
      will increase as the voltage of the power source increases. This
      second parameter is of primary concern in high voltage power
      distribution systems. By their nature, high voltage power sources
      will deliver high voltage into the distribution system. Capacitive
      loads will then be subject to high inrush currents upon power-up.
      The stress to the components must be understood and minimized.

This passage says that inrush current depends upon capacitance
value, voltage to applied to it.
From my basic understanding: for sudden changes the capacitor is a short and the capacitor will not allow any changes in voltage suddenly. So, when we turn ON power at that instant C will be short having 0 voltage across it. So the max current will depends on the ESR of cap and any series path resistance. It doesn't depends on the capacitance value.
This passage says: Inrush current depends on ESR of the cap and not on value of capacitor, which contradicts the previous passage.

From all these how can we calculate how much transient will there be?

One more confusion: most of the regulators specify controlled slew rate of the output to mitigate this inrush current limiting problems. But the slew rate limiting will work for capacitors connected on the output side. But there will be capacitors that will be connected on input side of the regulator. Will those have large currents?


texts: arduino nano broken or not after reversing l7805 pins?

texts: I tried to breadboard a project using arduino nano and l7805 regulator power by 12v dc from wall. I pluged the regulator backwards, output to 12v and input to 5v arduino pin, by mistake for a couple of seconds and I think I destroyed the arduino. Now the blink sketch that was uploaded is not workink and when I try to upload it again it says avr not in sync.  The power led is on and also the ftdi chip is recognised by windows.  Is it possible I detroyed it or not? What happened when I reversed the regulators pins?


texts: Protecting digital electronics from nearby high voltage sparks

texts:
I am controlling a high voltage power supply to generate corona discharge. To switch it on and off I am using an AC relay controlled by a microcontroller as shown in the figure.

The controller switches the power supply on for one minute and than shuts it down for 10 seconds.

Now the problem which I am facing is that sometimes during corona discharge there are sparks and when ever it sparks the microcontroller restarts(I know this because when it boots the LEDs blink on the board) and the HV power supply turns off before that one minute duration.

I tried putting the micro and the relay inside a Faraday shield and grounded everything but it does not seems to work. Also, other thing I noticed is that whenever I removed the relay and drive the HV power supply without the microcontroller the sparks have no effect on the controller.

Any suggestions on how to use the HV power supply with the microcontroller and protect it from the sparks?


texts: Meaning of a potentional tolerance value for a dimension in a mechanical drawing

texts:
The mechanical drawing below contains two dimensions (2-Ø2.30 and 4-Ø0.92) that I can't make heads or tails of. I have spent quite a while researching mechanical dimensional and tolerance conventions again, since I could not remember what this format meant. I was not able to find this particular format after looking through just over ten web pages with varying search terms.

My educated guess would be that the prefix (4- / 2-) is some special format of a tolerance value. Since the drawing is in millimeters and the hole diameters are quite small, I don't assume these prefixes to be in millimeters.
From what I can tell, the suggested diameters are 2.3mm and 0.92mm, but I stand to be corrected.

I would appreciate any feedback on what these values exactly refer to.

Source: https://katalog.we-online.de/em/datasheet/61400416021.pdf


texts: Calculating effective bit precision of DAC due to range restriction

texts:
Say I have a 16-bit DAC which outputs a range from 0-5V. My application only requires an output from 4-5V. I am interested in the effective precision of the DAC due to this range restriction.

Is the formula 16 - log((5 - 0)/(5 - 4))/log(2) = 13.68 bits valid?


texts:
What is the impact on a PCB design if it is panelized? I received a message from a PCB manufacturer:

  In your order, the quantity of boards is large and the boards are quite small. Can we panelize the boards for easier handling? If no, will cost an extra $32USD additional

While I wouldn't mind saving $32, I'm also worried the panelization will leave ragged marks on the PCB edges. Is that the case?


texts: What should a load cell response curve look like?

texts:
I have ordered some load cells from a Chinese supplier, and I asked for a load/output calibration report.
The chart they sent me looks like this...

Correct me if I'm wrong - but this is supposed to be a 5kg load cell - so it should be linear between 0 and 5kg, right?

How am I supposed to used one that is so obviously non-linear??

Thanks

EDIT: Specifications

Capacity 5kg
Accuracy 0.1%FS
Rated output 1.0±0.15mv/v
Operating voltage 6~12V
Input resistance 1000Ω
Output resistance 1000Ω
Electrical connection Excitation red Signal+ blue Signal- white
Cable φ0.8×350mm


texts:
I need to determine the "health" of car batteries in the field.

My objective is to predict when a car battery is likely to fail from data collected while the vehicle is in use. I am targeting 3 states - good Battery, Battery needs charging, Bad battery needs replacing.

In preparation, I will be testing batteries with various states of charge in a garage environment measuring voltage and current using automotive battery testers, current clamps and Oscilloscope and checking if the engine starts.

In the field I have the capability to measure voltage at 100Hz at every cranking event for a period of 5 seconds. In addition I can measure engine temperature, ambient temperature (but not battery Temp), Trip details - Duration, time of trip, engine size, time for engine to start.

I am unable to measure current remotely in the field.

The intention is to then "Prove" that      the status of the battery condition in the field matches that of the measure in the garage.

Does my proposed        experiment seem logical?

Are there any other factors that i should consider? I can then determine if I am capable of measuring them.

Any other input on the subject of developing the algorithm would also be welcome


texts:
I am trying to demodulate my PWM by using a low pass filter shown(the inductor of 6uH and capacitor of 10uF forms my low pass filter). The PWM was created using a triangular waveform produced by XFG1 function generator and a sine wave(which represents my audio signal) produced by XFG2 function generator. The sine wave is at 3kHz and the triangular wave is at 300kHz. I choose a cut-off frequency for my LPF to be at 20kHz. The problem I have is that the output frequency should be 3kHz,since am demodulating the PWM I should get my sine wave frequency(3kHz), but the probe(PR1) is showing 20.5kHz. Can anyone explain why this is happening?

The oscilloscope shows the output of the LPF filter(blue), and the output of the comparator(red).


texts: Will this MOSFET be suitable for driving a 12V 1-2A Load from an Arduino?

texts:
I have an Analog 12V RGB LED strip (which only requires 1-2 amps at most) that I want to control using an Arduino Uno. I looked into how I could go about doing this and saw that i could use several Logic Level MOSFETs to control the RGB pins on the LED strip.

I intend for the Arduino to send PWM signals to the gate (with a 10k pulldown) to control the brightness of the LEDs.

I can easily get hold of some STP55NF06L N-Channel MOSFETs which I initially thought should be able to do the job since the Gate Threshold Voltage is 1.7 volts. However I read too much off of the internet about what MOSFETs can be used with Arduinos and now I am unsure if they will work. One website told me one thing while someone else told me another. There was a lack of a clear cut definition.

Will these MOSFETs work with the 4-5V signal from an Arduino? If not, can you suggest any alternatives?

Also, if anyone can explain what should I be looking at in the datasheet to help me figure out if they are logic level, I'd be extremely thankful.


texts: How can I isolate a power well to reduce noise

texts:
I am designing a digital board which will drive a very coarse (simple on-off) high[er] current speaker. I am worried that the switching of the speaker will cause noise in the power supply driving it. If this was the same power well as the microcontroller, that wouldn't be good.

I will use separate ground and power planes for the power to the amplifier circuit. I don't want to actually use a separate power supply for it's power plane, but think a simple filter might work better. Could I just put an inductor/choke between the "main" power plane and the amp's power plane? I envision with the capacitor, this would essentially form a low-pass filter.

Does this make any sense? Any considerations I should take in selecting values? What about even doing anything in board traces/geomentry to make a simple/crude inductor or provide other isolation?

If I were really concerned about this - I would use a separate power supply. I haven't built the circuit yet and am not seeing any specific problems, so I am just trying to sort of minimize any potential problems. Thus, doing a simple isolation as such might just be a quick and easy thing to do.

Any good tips?


texts:
Got an OLED module with a FPC ribbon that has pitch 0.75mm. How do I prototype with a breadboard? I can only find breakout boards for a pitch of 0.5mm. Not only that, how do I prototype with a PCB, when I can't even find connectors for 0.75 mm.

Any idea how I can use this module?


texts: It has been mentioned in some articles that, in SiC (silicon carbide) diodes, as the temperature increases, avalanche voltage decreases and leakage current increases. What exactly does that mean?


texts:
I am using a SainSmart 5V 2-Channel Relay Module for Arduino to drive a hot plate (110V, 1000W).

I plugged my Arduino VCC and GND to the VCC and GND pins of the relay board and I drive both relays simultaneously through one of the digital output pin. The relays are controlling both the phase and the neutral of the cooking plate. In order to control my temperature, I turn the relays on or off in a 15 seconds window.

Twice, already, my relays appeared to die. The LED still works, and I still hear the noise when it is toggled, but the contact is not made anymore.

What am I doing wrong? How can I fix it?


texts:
I want to use the MCP1703 regulator in battery powered projects.  The datasheet of this regulator says that the quiescent current is typical 2 uA.

I measured the quiescent current for the MCP1703-5 at 80 uA.  For the MCP1703-3.3 I measured 50uA of quiescent current.

For measurement I connected the (6 to 12) volt DC to input and left the output unconnected.

Why is the quiescent current so high ?


texts: Guys I have a silly doubt. above is a standard circuit. I wish to ask how can a small signal current exist through the transistor shown above? The current source ( which is dc) will always force the saturation cureent of nmos to be = ID. So how can there be a situation of small signal analysis of nmos? As far I understand iD = ID + id, where second order distortion is neglected. So id (the ac component) will always be forced to be zero because of current source right??


texts: What is the metal part on top of this connector?

texts:
I'm wondering what the metal parts on top of these connectors are for:

Are they just for a spot to "grab" for pick and place, and these metal parts will be removed later?

Attribution for picture: Mill-Max


texts: What are those small metal bars going across a PCB for?

texts:
In quite a lot of PCBs that I have seen, they often have these small metal bars going across from one point to another.

Here is an image of what I am talking about. In this example it is a charger:

J2 and J3 are what I am talking about

For reference, here is the other side of the PCB:

So,

What are these called?
What is the point of these? Why not just use tracers in the board or a wire?


texts:
I am trying to implement a minimal partial reconfiguration project using the Vivado GUI. I have successfully enabled the project for reconfiguration and created a partition definition. The problem lies when I try to add a second reconfigurable module using the partial reconfiguration wizard.
After adding the second reconfigurable module and setting up the config and design runs to include this new reconfigurable module, I get the following error message:

ERROR: [Vivado 12-172] File or Directory '1/PR_Testing/PR_Testing.srcs/sources_1/new/Pr_Unit_3.vhd' does not exist

I know for a fact that the file does exist as I just created and simulated it.
Does anyone have any idea what the cause of this may be, and how it could possibly be fixed? The command executed by Vivado from the Journal file is:
add_files -norecurse {C:/MEng_Project/Dev/Phase 1/PR_Testing/PR_Testing.srcs/sources_1/new/Pr_Unit_3.vhd}  -of_objects [get_reconfig_modules pru3]
Many thanks in advance.


texts:
To avoid noise from the external system I tried to isolate the internal completely. So I added DC-DC isolated converter with signal isolation. I have attached the picture. Still when reading data and communicating with VFD it receives data (sometimes garbage) and the PC cursor shows unusual behavior which gets data from the FTDI(FT232R) connected to it.

What might be the reason of getting this noise because the internal system is fully isolated with the RS485 system.


texts:
I'm using an ATmega328P to provide a software-selectable 2, 4 or 8 MHz clock to my home made SBC.  This works just fine.  However, I am adding a programmable sound generator (PSG) to the board and it requires a 1-2MHz clock.

I want to keep the board simple and avoid flip-flop clock dividers and output selects due to the variable system clock speed, so I was hoping I could configure the ATmega328P to provide a second (non-variable) 2 MHz clock for the PSG.

Problem is, I'm not experienced with AVRs and their timer fuses and don't even know if this is possible with the ATmega328P?  If it is, how can I set up another pin to and its timer to provide the 2 MHz clock signal?

Bonus (almost unrelated) question: Can a 20 MHz AVR provide an 8 MHz clock pulse, as it's not a factor of 20?

EDIT:  Just to clarify a couple of points:

1) The ATmega328 is running at 16 MHz.  I'm using one clock/timer output to produce the required 8 MHz clock I need for the main board.

2) I need a separate (but ideally in-step with the 8 MHz clock) 2 MHz clock for the PSG.  I was hoping to be able to set up another clock output from the ATmega328?


texts: Magnetic switch, master/slave socket and dust collection

texts:
I have a dust collection (JET DC-1100CK) and table saw. I bought a 400V master/slave unit, connected all together and it does not work.

I talked to the JET seller and he told me that the dust collection uses a magnetic switch and is only compatible with the master/slave unit made by JET.

I don't want to resort to rewiring the switch, due to warranty, yet. Do you have some ideas how to fix this without breaching warranty (ie. by not messing the dust collection at all)?

One stupid idea I had was to use a strong magnet to hold it in ON position all the time, but it's probably stupid and naive, or?


texts: Maintaining constant voltage at end of long wire

texts:
I have a long 1 mm wire, about 1.5 meters long (and 1.5 m back). At the end of a wire I have a device that requires 3.7 V and can pull anywhere from 0 to 6 A at a time. However, when it pulls a high current I am noticing that the voltage drops and the device shuts down. Is there any way I can maintain a constant voltage at the device, regardless of the current drawn?
Some notes:

Using a thicker wire is not an option.
I cannot move the power supply closer to the device.

So I am looking for something that can regulate the voltage at the device's end.


texts: Finding relevant voltages and current in a BJT

texts:
I'm supposed to find Vb, Ve, Ic, Vc and Vce for this circuit but I have never seen anything like this, so I'm lost on how to even approach it.

Do I start from KVL and write two loops? But then there's way too many unknowns. Here's a very poor attempt at writing one:

Top loop: -VR1 - Vbc - VRc + 20 = 0
Bottom loop: -VR2 - VRe - Veb = 0

Do I assume the NPN transistor is in active mode and set Vbe = 0.7v? We don't know that until we find the actual relevant voltages around the transistor.

This somewhat resembles a voltage divider, but it doesn't seem like one.

Rough guideline is fine, I'd like to know a starting point on how to tackle this problem.


texts: i want to know the usage of a low pass filter and the usage of the phase

texts:
Good morning.
i would like to know a practical example about low pass filter and high filters..
and whats the use of calculating the phase between the input and output


texts:
I've been reading documentation on 1-wire and I think I'm having a brainfart.  How does the slave differentiate a read slot from a write slot?

reference:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/126

For example, lets say I want to read.  First i go through the reset procedure and check if any slaves are on the line.  Afterwards  I pull the line down for time A (~6us) and then release.  The slave should then keep the line low or release it which would be a read of 0 or 1.

How is this any different from write?  If I bring the line down for time A (~6us) and then the slave keeps it low I would think that looks identical to a write 0 slot. Similarly, if I bring the line down for time A (~6us) and then release and the slave allows it to go high that would look identical to a write 1 slot.


texts: Explain an oddity with coax internet signal loss

texts:
I debated which StackExchange site was best to post this question to. Please feel free to move it if I chose wrong.

In my house, coax enters the wall in one bedroom and is terminated 1 foot later at a female connector. Since my computer and cable modem are in another room, at that termination I placed a male-male joiner to which I connected a 25 ft cable. This cable goes through the floor and under the house, where it meets up with another male-male joiner, and then another 25 ft cable, which climbs back up through the floor in my computer room, and connects to my cable modem. The reasons for this long rat's nest of a route are historical and forgotten, but most likely due to laziness and simplicity. :-)

Now, once a month or so my internet connection drops out. Most of the time, simply cycling the power on the modem is enough to fix it. Rarely though, when cycling the power does not work, I've observed that disconnecting and then reconnecting the coax cable from the modem (while leaving it powered on) does work, which is very strange. But it gets even stranger! Even more rarely, say maybe once every two years, there will be an outage that is not fixed by either of the procedures above. However, in this case if I move back to the first bedroom where the coax enters the house and disconnect/reconnect the connection at the joiner there, then the problem is fixed.

To summarize:

Most connection dropouts are fixed by cycling modem power
Maybe 10% require cycling the coax connection at the modem
Maybe 1% (ultra rare) require cycling the coax connection further upstream from the modem

In none of these "connection cycling" cases are the connections loose or in any other obvious physical way suspect. Can anybody explain this weirdness?


texts:
I am having some trouble writing to FLASH on the MSP430F5529. I have gone through the examples provided by TI and read through the user guides and part datasheet, but have been unable to find the problem. My goal is to save the baud rate enumeration in FLASH and look it up on boot. Applicable code is below:

static const uint32_t baudRegister = 0x1980;  // Baud rate register flash location (Info A)

//Change baud rate
void changeBaud(uint8_t baudEnum) {
    eraseSegment(baudRegister);               // Erase flash segment
    writeFlashByte(baudRegister, baudEnum);   // Write baud enumeration to FLASH
    WDTCTL = 0;                               // Force uC reset
}

//Erase flash segment
void eraseSegment(uint32_t address) {
    int8_t *flash_ptr = (int8_t *)address;

    __bic_SR_register(GIE);                   // Disable interrupts

    FCTL3 = FWKEY;                            // Unlock FLASH control regs
    FCTL1 = FWKEY + ERASE;                    // Select segment erase
    *flash_ptr = 0;                           // Dummy erase byte
    FCTL3 = FWKEY + LOCK;                     // Lock FLASH control regs

    __bits_SR_register(GIE);                  // Re-enable interrupts
}

//Write byte to FLASH
void writeFlashByte(uint32_t address, uint8_t data) {
    uint8_t *ptr = (uint8_t *)address;

    __bic_SR_register(GIE);                   // Disable interrupts

    FCTL3 = FWKEY;                            // Unlock FLASH control regs
    FCTL1 = FWKEY + WRT;                      // Enable writing of segment
    *ptr = data;
    FCTL1 = FWKEY;
    FCTL3 = FWKEY + LOCK;                     // Lock FLASH control regs

    __bis_SR_register(GIE);                   // Re-enable interrupts
}

changeBaud() is called from within main(), and it is passed an enumeration for the baud rate (example: 1 = 300bps, 2 = 600bps, ... 6 = 9600bps, 7 = 14400bps, etc).

When I run eraseSegment() the contents of the FLASH at address 0x1980 remain as 0xFFFF. I think this is expected (0xFFFF means cleared). However, when I run writeFlashByte() when I get to the line *ptr = data; it does not seem to do anything. While debugging I have confirmed that data has the correct enumeration value and ptr is the correct address, but for some reason writing data to *ptr does not load the memory with the value of data.

I am quite new to writing data to flash, so this one has me stumped. The code above is based on TI's examples available in MSPWare.

What might cause this problem?


texts: Power supply issues with LCD and MPC23017 expander chips

texts: I have an Arduino Uno and I'm working on a project that requires me to use six MCP23017 chips on a I2C bus plus a LCD 16x2 monitor. I need MCP23017 chips to power 36 LED's at the same time (8 LED's per four chips, 4 LED's on the fifth one + sixth for some input pins). So far I figured to drop the current with resistors for LED's to about 5 mA per LED. So that's about 180 mA for LED's and at least 120 mA for LCD monitor. I believe that Arduino Uno has a max of 200 mA through 5V pin. So is there any way for me to drop the current below the required limit? Also I do need to adress each pin with LED individually.


texts: When should I use USART instead of UART?

texts: I want to make a communication between my PIC18F4550 and my PC but I'm getting stuck whether I should use UART or USART for long distance. When it's more advantageous to use the one instead of the other one?


texts: I have two coils covered in a box and I don't know the physical arrangement of the two coils and mode of each winding in a magnetically couple DC circuit. How can I make an experiment to determine the dot convention of the two coils?


texts: Charging supercapacitor parallel with different sources

texts: Is it possible to charge one supercapacitor with multi voltage sources in same time? All rated at near by 4V for example, 4.05, 4.1, 4.0 volts.


texts: Two different SPI modes in one microcontroller

texts:
I am interfacing two chips with SPI communication with atmega328. One chip uses SPI mode 0 and other one SPI mode 1.
Is it advisable to toggle modes in micro each time interrupt request is received from any chip. What other options do i have.
I tried doing bit bang SPI for one but the max clock i could achieve was 900kHz, while my min clock requirement is 1Mhz for both chips.


texts: Driving WS2811 LED strip from microcontroller

texts:
I'm planning to drive the input of a WS2811 based LED strip (total approx 450 LEDs) from a microcontroller/arduino, as per the diagram below.

Do I need a transistor, buffer or anything else between the microcontroller GPIO and the WS2811 DIN? Or can I safely hook it up directly?

Also am I correct in reading from the WS2811 datasheet that even though the LED strip takes 12v, the WS2811 itself will run at 5v, and as a result the Din voltage should be at 5v too?


texts: STM32: Busy flag is set after I2C initialization

texts:
For the reference: the same problem is described there, but the author's solution doesn't work for me - I2C busy flag strange behaviour

I used STM32CubeMX to generate project template with I2C peripherals initialization. Unfortunately it works somehow strange: after HAL_I2C_MspInit(I2C1) is being invoked, bus is considered permanently busy.

If I try to apply

__HAL_RCC_I2C1_FORCE_RESET();
HAL_Delay(1000);
__HAL_RCC_I2C1_RELEASE_RESET();

That resolves problem with BUSY flag, but causes problem - SB bit not being set after START is generated. According to debugger, I2C registers are cleared completely after the reset - I suspect this is the problem with that method.

I also confimed short voltage drop at SDA line during startup, that is probably the cause of the issue. I took a closer look at SDA/SCL pins initialization code generated by CubeMX:

void HAL_I2C_MspInit(I2C_HandleTypeDef* hi2c)
{

  GPIO_InitTypeDef GPIO_InitStruct;
  if(hi2c->Instance==I2C1)
  {
  /* USER CODE BEGIN I2C1_MspInit 0 */

  /* USER CODE END I2C1_MspInit 0 */

    /**I2C1 GPIO Configuration
    PB6     ------> I2C1_SCL
    PB7     ------> I2C1_SDA
    */
    GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_7;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

    /* Peripheral clock enable */
    __HAL_RCC_I2C1_CLK_ENABLE();

  /* USER CODE BEGIN I2C1_MspInit 1 */

  /* USER CODE END I2C1_MspInit 1 */
  }

}

I changed it to put clock enable before HAL_GPIO_Init() invocation and now my I2C communications works (at least I didn't noticed anything weird yet).

Finally, my question is - is there any better solution for this? CubeMX places clock enable code after the GPIO init method invocation. I can stay with two invocations of __HAL_RCC_I2C1_CLK_ENABLE(), but that's quite ugly in my opinion, so I am looking for any better solution, either software or hardware.

Device is STM32F100RB on STM32VLDiscovery board (with STLink v1), in case that matters.


texts: How to design a auto-touch attachment for capacitance screen?

texts:
I’m thinking about developing an attachment which is able to “touch” the capacitance touch screen just like the human fingers do, it might be a membrane layer can be sticked to the capacitance touch screen, when sending different signals to it, it will “touch” at specified coordinates of the screen like human fingers do. Meanwhile, the layer should be transparent.
Does anyone have idea? Very appreciate it.


texts: Help on making an electronic Etch-A-Sketch in Virtual BreadBoard?

texts:
I have beginner-level electronic experience, and I use Virtual Bread Board. I'm trying to make an electronic etch-a-sketch made up of a 30 by 30 grid of N-Way LEDs (It's a thing in VBB I'm not sure if they really exist but they're called LED[N] in VBB). My idea right now is to use 2 potentiometers that adjust voltage or capacitance, to make it work. I'm not sure how I would make the drawing system work, but I think using POT's (not slide POT's) is a good place to start, and it's also accurate to the original etch-a-sketch. any help would be appreciated. My goal is to avoid using an Arduino in this project, because VBB's Arduino is a bit messy and unreliable.
If you don't know what an Etch-A-Sketch is, here's a link to the Wikipedia page on it.
https://en.wikipedia.org/wiki/Etch_A_Sketch


texts: Converting a tachometer signal into something a microprocessor can understand

texts:
I am attempting to build a digital dashboard for my car (a 1998 honda civic), I have run into a bit of trouble, wherein the tachometer signal is quite hairy. I was wondering if someone would lend me a hand in cleaning it up so that I can feed it to a microcontroller (an arduino uno, just to keep things simple).

I have an oscilloscope and have scoped the tach signal. Here is an image of it:

This is at 50v per division vertical and 5 milliseconds per division horizontal. Unfortunately just an analog scope.

There is a pretty serious spike in voltage, (presumably) when the ignition coil is charging, then it drops down to around 40v, and then further down to about 14v for the long wait until it discharged and is grounded out. There is ringing on each of these transitions that will have to be dealt with to the tune of 50khz as well.

I would greatly appreciate any suggestions as to how to clean this up.


texts: Is there an electrical design reason for phone SIM cards being inaccessible until a battery is detached?

texts:
So far I haven't seen a cell phone that allows to detach the SIM card without first detaching the battery - the SIM card is placed behind the battery and inaccessible unless the battery is detached.

I assume there's some electrical engineering reason for that - like maybe detaching a SIM card with battery installed will damage it.

Is there any electrical engineering reason for that?


texts:
I am trying to setup a PIC24FJ64GB002 for UART communication in MBLAB using XC16.  I am using the USB CDC demo to communicate with a device, and I am trying to relay that information to an arduino using the PIC.  I am confused as to what frequency the cpu is running at.  I am using an external 8 MHZ crystal, with several bits set in the demo.  Bits relating to the oscillator are set here.

#include <p24FJ64GB002.h>
#include "system.h"
#include "usb.h"

/** CONFIGURATION Bits **********************************************/
_CONFIG1(
    WDTPS_PS1 &
    FWPSA_PR32 &
    WINDIS_OFF &
    FWDTEN_OFF &
    ICS_PGx1 &
    GWRP_OFF &
    GCP_OFF &
    JTAGEN_OFF
)

_CONFIG2(
    POSCMOD_HS &
    I2C1SEL_PRI &
    IOL1WAY_OFF &
    OSCIOFNC_ON &
    FCKSM_CSDCMD &
    FNOSC_PRIPLL &
    PLL96MHZ_ON &
    PLLDIV_DIV2 &
    IESO_OFF
)

_CONFIG3(
    WPFP_WPFP0 &
    SOSCSEL_SOSC &
    WUTSEL_LEG &
    WPDIS_WPDIS &
    WPCFG_WPCFGDIS &
    WPEND_WPENDMEM
)

_CONFIG4(
    DSWDTPS_DSWDTPS3 &
    DSWDTOSC_LPRC &
    RTCOSC_SOSC &
    DSBOREN_OFF &
    DSWDTEN_OFF
)

/*********************************************************************
* Function: void SYSTEM_Initialize( SYSTEM_STATE state )
*
* Overview: Initializes the system.
*
* PreCondition: None
*
* Input:  SYSTEM_STATE - the state to initialize the system into
*
* Output: None
*
********************************************************************/
void SYSTEM_Initialize( SYSTEM_STATE state )
{
    //On the PIC24FJ64GB004 Family of USB microcontrollers, the PLL will not power up and be enabled
    //by default, even if a PLL enabled oscillator configuration is selected (such as HS+PLL).
    //This allows the device to power up at a lower initial operating frequency, which can be
    //advantageous when powered from a source which is not gauranteed to be adequate for 32MHz
    //operation.  On these devices, user firmware needs to manually set the CLKDIV<PLLEN> bit to
    //power up the PLL.
    {
        unsigned int pll_startup_counter = 600;
        CLKDIVbits.PLLEN = 1;
        while(pll_startup_counter--);
    }

    switch(state)
    {
        case SYSTEM_STATE_USB_HOST:
            PRINT_SetConfiguration(PRINT_CONFIGURATION_LCD);
            break;

        case SYSTEM_STATE_USB_HOST_CDC_BASIC:
            BUTTON_Enable(BUTTON_USB_HOST_CDC_BASIC);
            PRINT_SetConfiguration(PRINT_CONFIGURATION_LCD);
            break;
    }
}

I then use this function to initialize the UART

void UART_INIT()
{
   AD1PCFGL = 0xFFFF;
   __builtin_write_OSCCONL(OSCCON & 0xbf);
   TRISBbits.TRISB15 = 0;
   __builtin_write_OSCCONL(OSCCON | 0x40);
   RPOR7bits.RP15R = 3;
   U1BRG = 103; //set baud speed
   U1MODE   =   0x8000;  //turn on module
   U1STA    =   0x8400;  //set interrupts
   IEC0bits.U1TXIE = 0;
   IFS0bits.U1RXIF = 0;
   IFS0bits.U1TXIF = 0;
}

And this function to transmit a byte

void send(char c)
{
   while(U1STAbits.UTXBF == 1);
   U1TXREG = c;
}

I am trying to figure out what value FCY should be defined to be.  I assumed that it would be 16 MHZ, (96MHz / 3) / 2 but the code did not work at that setting.  Could there be another problem in the code?

I am making all pins digital and setting the UART pin as an input with this code

__builtin_write_OSCCONL(OSCCON & 0xbf);
AD1PCFGL = 0xFFFF;
TRISBbits.TRISB15 = 0;
UART_INIT(9600);
__builtin_write_OSCCONL(OSCCON | 0x40);

Finally, I use the functions like this

UART_INIT(9600);

while(1)
{
send('H');
send('e');
send('l');
send('l');
send('o');
send(' ');
send('W');
send('o');
send('r');
send('l');
send('d');
send('\n');
}


texts: Feedthrough capacitor in analog switches

texts:
I'm just wondering if anyone knows what feedthrough capacitor is, and how it can affect our switch.

As far as I'm concerned, if we use FETs as switches, feedthrough capacitors are the one that connect the input with the output. ( it can have values around 1pf-10pf).
If I'm right, what problems can cause these parasitic capacitances?

Thanks in advance.

p.s

When I say input tied to output, I'm refering about parasitic capacitances that connect the drain with the source.


texts: Is there a standard way to probe SPI without causing data corruption?

texts:
When I connect my oscilloscope probes to my SPI lines, the line voltages get affected a lot and so my SPI comms fail.
I am using a breadboard as an intermediary between the two devices and adding cables to the breadboard to scope from.
Is there a better way to probe SPI? I'm currently looking to snip my wires to expose the metal and probe that way to reduce the length of the SPI connections.
Any better ideas would be appreciated.
Running SPI at 10 MHz


texts: How do I read a datasheet for a solid state relay?

texts:
I'm looking to use several (12-18) solid state relays to control a set of water valves (24V AC solenoids, 20ma holding current, 40ma inrush current), and I'm having trouble finding suitable parts, probably because I don't understand the datasheets I'm reading very well.

Most of the low-current (<=150mA), inexpensive (~$1) SSRs that I've found have maximum "input forward voltage" ratings in the 1.0v-1.5v range (see here for a typical example). Does this simply mean that I need a 38 ohm resistor between my MCU (3.3v) and the SSR?

What do the other ratings mean, such as these:

Repetitive peak OFF-state current (output)
ON-state voltage (output)
Holding current (output)
Minimum trigger current (transfer)

I assume that ON-state voltage is the minimum voltage required over the output of the SSR for it to turn on, so at 24v, I'm well above the minimum, correct?

Minimum trigger current and holding current are the amounts of current across the output required to turn and keep the SSR on? Wouldn't the current drop to zero at the zero voltage crossing? I'm not sure what these ratings mean.


texts: OP amp noise density and Johnson noise (Thermal noise) for 16bits ADC

texts:
I am trying to create a analogique amplification chain between a piezo sensor (10mVPP) and 16 bits ADC in 3V3 range. I try to simulate the chain on LTSpice to get the lower noise density I can get.
@3V3 for 16bits  3.3/2^16  = 50.35 µVRMS for 1 LSB.
When I simulate the noise on a nominalistic chain I quickly go over the ADC LSB only with thermal noise.
I think I misunderstand my result.
In this exemple I just put an OPAMP with gain x400 and two filter HP 1.5 kHz and LP 50 kHz and I already go 523 µVRMS that is 10 times the LSB of the ADC... (This use 4 bits of my ADC just for thermal noise)
Can someone help me to clarify this ?
(I know it's just a simulation and not real life, but I don't understand why I can't go down to 1 LSB on 16 bits on simulation)
Schematic

Noise analysis

Signals

Response


texts:
I got the EVAL_AD9784_PMDZ and Zedboard reading data. It is differential ADC, 2 probes with 1 common ground. The ground is at the ZedBoard GND level (as expected). The voltage input is +7.5, GND, -2.5 V on connector J3 - according to specification and 3.3[V] and GND on Zedboard.

Lately, the probes are giving off voltage of 2.5 [V]. I would like to ask, whether it is faulty behaviour.

I havent measured the difference between probe and ground before, when it seemed to work properly, but I would expect the probe wouldnt force any voltage on measured signal.

EVAL_AD9784_PMDZ (please mind that jumper SL1 is in position B on my board - allegedly correct position):

the schematics:

Could the troubles come from U8 (second picture in schematics)?

ADDITIONAL INFO (EDIT):

When there is analog signal 2.5 [V] (peak-to-peak), 0 [V] offset, 0.3 Hz, and -VS_EXT is disconnected the board works fine, except when signal is getting closer to 0 [V].

From my point of view, this implies that there is something wrong with the negative voltage supplied to both OP-AMPs on inputs.


texts: the non inverted input on TI UC3705 or UC3706 transistor dirvers not working but inverted works fine?

texts:
DATASHEET TI UC3705
I have a UC3705 running fine on inverted input digital signal on the pin number 7 at +5 volts and pin 6 at ground from my siglent SDG1032X with a square wave 5 volt hi and 0 volt at low with frequency of 60 hertz. Pin 1 and 2 are 19 volts. pin 4 is output and DSO shows a fine 60 hertz 19 volt square wave output. I did notice that pin 6 which is the digital input ground must be connected to the power ground pin 5 or there is no output.
pin 3 is open and pin 8 is open.
However if I try to use the non-inverted input pin 8 instead of inverted input pin 7 I get no output?
Does anyone have any experience on TI UC3706 or UC3705 as I tested this on both these chips and get no output with noninverted pins as input?


texts:
I'm working on project that requires I switch a 12v power supply on the high side of a circuit, using a 3.3v micro controller.  To make this work, I'm thinking a can connect a PNP transistor on the 12v high side, and connect the base to the collector of an NPN.  Then connecting the base of the NPN to the 3.3v pin on the microcontroller and the emitter to ground.  I found this example online:

This leads to my question...I need to create 8 separate switches on this one circuit...Does this PNP to NPN high-side switch still work if I connect multiple in series??  Here is my current schematic...

The LED represent the load for the 12v supply.
In this configuration, does the transistor still work like if there were only one NPN and one PNP...Or does the current get amplified with each NPN/PNP in the series?


texts: Would a stepper motor driver chop a high current to its max allowable limit efficiently everytime?

texts: We are using this stepper motor driver A3967(https://www.sparkfun.com/products/12779). If we increase the input current to the driver to 2Amp, will it cutoff the current to the motor at 750mA everytime since it is a chopper driver?


texts:
i am working on a mp3 player project for hobby use,i use atmega644pa @12Mhz and use fatfs library via spi.Avr has no enough sram to the long file names so I tried to store long file names in a text file and display it line by line on my display.At the first sight i succeded but when the file names get bigger the program gets slower. my line reading program is here:
char line[150]; /* Line buffer */

char* readline(const char * filename,int num){
    FIL fp;     /* File object */

    FRESULT fr;     /* FatFs return code */

    fr = f_open(&fp,filename, FA_READ); /* Open a text file */

        int i=0;

    while (f_gets(line, sizeof line, &fp)) {  /* Read every line  */
            if (num==i)  // if desired line equals i
            {
                break;
            }
             i++;
            }

    f_close(&fp); /* Close the file */

    return line;

}

I need faster line reading function or more efficient way to store files to display,Thank you.


texts: I have designed the following circuit using a PMOS (FDC6312P) as a load switch. The gate of the PMOS will be driven by an NPN transistor that can be controlled using the MCU's GPIO. I need to make sure that upon power-on, the load switch remains guaranteed off unless explicitly driven by the NPN through the MCU GPIO. Am I doing it right?


texts: The most common Audio Amplifier uses a NPN and a PNP BJT as an emitter follower to drive a low impedance speaker .This has been true for about 40 years.Some idle current is set up by a biasing circuit to reduce crossover distortion .With no bias and hence no idle current the music will sound terrible at low power.The better circuits used techniques like a  thermally coupled VBE multipler transistor to keep the idle current relatively constant with changes in temp or supply volts.Is there an optimum idle current where distortion in minimised ? Is it only important that the idle current is above a certain amount ? Is it better to run more idle current assuming that power drain and heat are not a problem? The idle current figures given in old magazines for old circuits seem rather nominal .Is there a proper design equation or are there sensible rules of thumb?


texts: I'm trying to design a simple solid state relay that can be in the off state when an AC Source is applied (schematic one) and then source up to 150mA to a small resistor when that AC Source is removed (schematic two). My one problem here is I cannot seem to turn on the MOSFET with this wiring scheme, as the Gate and Source are shorted. Any ideas on how to fix this? (Can assume DC Source is 2.5V, AC Source is high, up to 1kV peak)


texts: What types of non-RJ45 cable assemblies plugs/sockets are common? I need to carry instrumentation signals (8 of them) which are a mix of small signal and 60Vpp. I cannot use RJ45 in case someone thinks its Ethernet and destroys their PC by connecting to it


texts: How to use USBee AX logic analyzer under Linux?

texts: I've got clone of USBee AX logic analyzer, to play with one and see if I need a device of such type at all. Unfortunately, I haven't found any Linux software that supports one. I have tried Sigrok, but it shows "Failed to configure samplerate" when I try to acquire data. I'm not sure if it is "clone problem" or something. Windows USBee software works ok with my device.


texts: Convert something that runs off two D cell batteries to instead run off a car battery

texts: I do not know much, but I have a portable shower (http://help.venditiogroup.com/support/solutions/articles/6000178636-zenvida-portable-tankless-water-heater-outdoor-shower-260-pcwh01) that I would like to set up to be powered by the 12V car battery that runs the water pump which is a necessary but separate part of the shower.  All the 2 D batteries do is spark to light LP to heat the water.  The lock on the battery compartment broke and the MFG wants $10 to send me a replacement.  This is a mostly permanent set up where the car battery is on a solar charger and I just don't see the logic in maintaining the D cell batteries but I am clueless to what would be necessary to convert and would appreciate any assistance that can be provided.


texts: How to calculate V/f value for an Induction motor?

texts:
I want to implement constant V/f in variable speed Inverter of a 3-phase Induction motor, 1500 rpm, 4-poles. I also know the equation:

V/f = 4.44 × N x Phi
Phi is maximum value of flux, f is frequency and N is number of turns.

How can I calculate or measure the constant value of V/f for the above motor using above equation? What will be the value for N and Phi?

Or is there any other way to find out the constant value of V/f of an ACIM?


texts: What are the limitations of using a LDR sensor?

texts:
I have to explain limitations for a photoresistor/LDR . I've read the book, and searched online but find nothing.

Can I get help with this ? Are things that the sensor can NOT do, which other tools can do better? What are the limitations? How do the sensors' features set restrictions?

LDR datasheet


texts: Plugging a LDR into GPIO pins of a Raspberry Pi

texts:
I want to connect a LDR into the GPIO pins of my Raspberry Pi, I know that Raspberry Pi doesn't have an analog-to-digital converter so what I want to do is to signal a HIGH signal (3.3v) on the GPIO when there is low resistance on the LDR (something below 200 ohms) and a LOW signal when the resistance of the LDR is high (above 2k for instance).
The maximum current that I can safely drawn from the GPIO pins of the Raspberry Pi, according to the documentation is 50mA, how do I calculate the resistor needed, will I need to add a pull up/down resistor too ? I don't have a clear idea on how to do that on a safe way without burning my processor.

I imagine that I also have to plug a resistor on the circuit to make sure that it always has a resistance when the LDR is on a very low resistance state.

Update: it worked fine, I built the circuit and it is shown in this post, thanks for the help.


texts:
I'm looking at this accelerometer LIS3DH and the datasheet says that it could enable interrupt generation on X/Y/Z "high" or "low" events. What do these events actually mean? When are "high events" generated? For X high events, are they generated when the sensor increases w.r.t. the X axis? Are these events indications of direction of movement?

Thanks


texts: Relay sticking when switching mains for LED power supply

texts:
I'm switching on an LED strip power supply using an Arduino, but my relay has just started sticking. The relay switches the mains for a 5V 20A power supply. The relay board is this style.

The relay is apparently rated for 10A @ 250VAC, so I think should be fine for the continuous current, but I guess the inrush current when the power supply is first switched on is what's causing the relay contacts to fuse.

I have another 4 of these relay boards spare, so I'm wondering if I can either a) Somehow limit the inrush current to the power supply so that I can just use one of these boards, or b) Figure out the inrush current so I can use a more suitable relay.

If I go with b) - does anyone know of a relay that would be up to the task? Ideally 5v with the same package as the ones on those boards so I can do a straight swap, but I'm guessing the ones that can handle the higher inrush current are probably a bigger package, right?

Edit:
Here's a quick schematic of the setup:

The reason I'm switching on the AC side instead of the 5V was really just for power saving, so that the power supply isn't on constantly, only when I want it on (when the Arduino signals D5 high).

The relay is sticking in the on position - the output stuck on closed and when the whole thing was unplugged (both USB and AC), I managed to give the relay a few taps and it eventually unstuck and opened up again.


texts:
I've an Enable pin active-high that have maximum voltage rating of 3.0v, but I use a 3.3v MCU outputs. I've also a 3.0v voltage regulator on board.

Should I use resistor voltage divider or there is a possibilty to use 3.0v voltage regulator? And how should I connect it?


texts: Is it possible to make the 7490 in BCD encoded output mode (divide by 10) have a "start" state and limit its count to a certain number? What I am looking for is a way to make the 7490 start at 1 (0001) and then have it count up to 5 (0101) then back again at 1.


texts:
I am working on  stm32l053 (nucleo 64) and I want to track time with integrated RTC. Since I am quite new to stm32 development I am using CubeMX and HAL libraries.

My problem is that the time is not changing over time, the HAL_RTC_GetTime() function is always returning time that was configured at the beginning in the MX_RTC_Init() function generated by CubeMX.

Here is my code for testing:
Vars:

RTC_TimeTypeDef currTime = {0};

in while

    while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
      HAL_RTC_GetTime(&hrtc, &currTime, RTC_FORMAT_BIN);
      char timeBuff[20];
      sprintf(timeBuff,"%d,,,%d...%d\n", currTime.Hours, currTime.Minutes, currTime.Seconds);
      HAL_UART_Transmit(&huart2, timeBuff, sizeof(timeBuff), 100);
      HAL_Delay(1000);

  }

And here is the generated MX_RTC_Init() function:

static void MX_RTC_Init(void)
{

  /* USER CODE BEGIN RTC_Init 0 */

  /* USER CODE END RTC_Init 0 */

  RTC_TimeTypeDef sTime = {0};
  RTC_DateTypeDef sDate = {0};

  /* USER CODE BEGIN RTC_Init 1 */

  /* USER CODE END RTC_Init 1 */
  /** Initialize RTC Only
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_12;
  hrtc.Init.AsynchPrediv = 127;
  hrtc.Init.SynchPrediv = 255;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }

  /* USER CODE BEGIN Check_RTC_BKUP */

  /* USER CODE END Check_RTC_BKUP */

  /** Initialize RTC and set the Time and Date
  */
  sTime.Hours = 10;
  sTime.Minutes = 15;
  sTime.Seconds = 0;
  sTime.TimeFormat = RTC_HOURFORMAT12_PM;
  sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sTime.StoreOperation = RTC_STOREOPERATION_RESET;
  if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BIN) != HAL_OK)
  {
    Error_Handler();
  }
  sDate.WeekDay = RTC_WEEKDAY_SATURDAY;
  sDate.Month = RTC_MONTH_MAY;
  sDate.Date = 25;
  sDate.Year = 19;

  if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BIN) != HAL_OK)
  {
    Error_Handler();
  }
  /** Enable the WakeUp
  */
  if (HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, 5, RTC_WAKEUPCLOCK_CK_SPRE_16BITS) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */

  /* USER CODE END RTC_Init 2 */

}

Serial output is:

10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
.
.
.

PS.
RTC WakeUp is working as expected so the RTC is counting but I guess it is not storing counts in registers.


texts:
I bought a new speaker and it hums even with volume knob turned to 0. After opening it up, I noticed it was the iron transformer oscillating (and screwing it tighter does reduce the noise).

How is it possible to produce a 100Hz noise out of 50Hz mains ac? Is there any method to reduce this oscillation besides mechanical locking?


texts: How do we compute power from current and voltage samples? Can we quantify its accuracy?

texts:
I have a datalogger that periodically samples current values by measuring the voltage across a power resistor connected in series with a battery and sensor (the load). The datalogger also samples the voltage across the sensor. Let's call the current samples i[n] and voltage samples v[n]. Sampling of both signals is controlled programmatically (i.e., I specify in code how often to sample each parameter).

p(t)=i(t)v(t) and if we had measured the current and voltage signals continuously (as analog signals and not sampling, as I'd done), we could have built a circuit that "continuously multiplied" i(t) and v(t). p(t) would have been a continuous value.

Instead, we have the discretized the signal by sampling it and so we could only compute p[n] as i[n]*v[n].

How representative is p[n] of the actual power being drawn, p(t)? Why might someone (say an engineer who's in charge of designing the power subsystem) be interested in sampling p[n] at a higher frequency?

Also, what can we say about p[n] if the samples weren't simultaneous (i.e., i[1] was measured 1.5 seconds from the start and v[1] was measured 1.525 seconds from the start)?


texts: Waterproof connector to hack electric toothbrush

texts:
I have an Oral-B Triumph 5000 whose battery needs replacement.

I would like to bring out the positive and negative connectors to both allow external charging/discharging/refresh (external smart chargers like BC-700 do a better task) and to allow plug-in operation with an external 1.5V power supply.

The space inside the device is very limited, so I don't know which connector I would be able to add inside the casing (see this Youtube video) so I may need to bring out a cable with a power connector.

Even keeping in mind that I can build small objects with a 3D printer, I don't know which power connector (hopefully small, not a big, screw-in, industrial connector) are available for use/modification: during cleaning and during operation plenty of liquids flow around. During operation in battery-only mode, the connector should not expose the contacts (directly connected to the internal battery), to avoid shorting them out.

Which small connector (like audio jack, but waterproof) or which external, cabled and compact waterproof connector are available for the purpose, rated for 2A operation?

I was able to find this one: https://www.adafruit.com/product/743 but I cannot find the exact model number to know more about it, and also when disconnected (battery operation in my case) the contacts are exposed. I would need to build a plug (silicone?) myself to close them.

Edit: the question was asked here because it seems that waterproof electrical connectors are part of this website, see tags "waterproof, connectors".


texts: Why does this Zener diode circuit not produce the Zener voltage?

texts:
Why does the measured voltage at the op-amp input equal 2.02V?

simulate this circuit – Schematic created using CircuitLab


texts: Grounded thermocouple vs "grounded" thermocouple

texts:
I'm having problems with documentation and what appears to be conflicting use of the word grounded. The way I understand it, a thermocouple can be [grounded, ungrounded, or unsheathed] (http://www.omega.com/techref/themointro.html). But neither of the two wires are actually connected to ground, they're still floating when they go into the thermocouple amplifier.

However, I've been reading a lot about thermocouples and they talk about grounding them by connecting the T- side to ground through a 1M resistor. This is a completely different type of grounding to me (http://www.analog.com/library/analogdialogue/archives/44-10/thermocouple.pdf)

I'm trying to use a Max31855 breakout board, and it specifically says it's not compatible with grounded thermocouples. So which grounding do they mean? I've not had either wire connected to ground (but I'm using a K-type grounded thermocouple), and occasionally a static shock when I touch it will reboot my Arduino and send out all kinds of garbage over the serial.


texts: Wiring 3 50w LED Chips Off a 12v Battery

texts:
I have 3 of the following chips: 50w, 12v chips (https://www.amazon.com/gp/aw/d/B081QBC9MZ?ref=ppx_pt2_mob_b_prod_image) with the following specs:
Features & details
Current: 3750mA
Voltage: DC12-14V
Color temperature:3000-3500K Luminous flux:3500-4000LM
Lifespan:50000h
I want to wire them to a sealed 12v battery onboard my kayak.
What would’ve the best way to wire them? Series, parallel...how many amp battery should I purchase?


texts:
I have an AC speaker set and it is plugged into an outlet. Then the outlet is put into a transformer where the transformer output is 17V 2.5A AC. Then from the transformer is put through a bridge rectifier and turned DC. My question is, how powerful of a battery will I need to power it?

(I'm assuming that I simply need to connect the battery leads to the output of the bridge rectifier.)

Update:
Just figured out that the amp chip is a TDA8947J, if that helps at all :)


texts:
Are AC adapters (e.g. laptop chargers) electrically isolated from ground because they have a transformer?

I'm asking this because I read that isolated transformers have a 1:1 ratio whereas AC adapters are commonly a step-down.


texts: Design review for photoresistor-controlled linear regulator

texts:
I would appreciate some comments/insights/criticism on my design:
I want to turn on/off a linear regulator (MIC5504) based on the light. I have tried just using a resistor and photoresistor voltage divider on the gate of the FET, but this causes flickering in certain lighting conditions (which is somewhat reduced with a 0.1uF cap, but whatever).
To overcome this, I decided to put in a Schmitt trigger roughly between 2/3V.
The op-amp then turns the FET on, enabling the 3.3V linear regulator.
I have not picked an op-amp. I have LM358P on hand, but am willing to go for some SOT-23 alternative, like AD8541. Not sure what the best "general purpose" op-amps are, but I feel like any old op-amp would work for my scenario. The reason I want to go for SOT-23 is because I have breakout boards to DIP for them on hand.
(The battery is connected to a BQ21040 for charging, but that is not included in this schematic.)
(I'm also aware that the battery won't stay at 3.7, and will be somewhere between
4.2 and 3-ish V. In those cases, I'm OK with the trigger values changing).


texts: Differences between flip-flops and gates

texts: Whatever I searched the web I found things about differences between latches and flip-flops. I'm so new in electronics, my question is what is the difference between gates and flip-flops?


texts:
I've been trying to understand the working of DRAM chips but apparently in a lot of confusion.
Suppose there are 8 banks in a single chip on a module. Is it only one bit that comes out of a single bank and a byte out of a chip altogether?
And out of the 8 bytes coming out of a channel, how does the memory controller accesses only one byte?


texts: How do a single-side band signal and a double-side band signal look like in time domain?

texts:
I understand what SSB and DSB mean in frequency domain.
For SSB, the signals appear at one side of the carrier frequency.
For DSB, the signals appear at both sides of the carrier frequency.
So now suppose the signal is a sinusoidal Acos(w1t) at baseband and the carrier frequency is a sinusoidal Bcos(w2*t) where w2 > w1. If these two signals are applied to an SSB mixer and a DSB mixer, then how the resulting SSB and DSB signals look like in time domain?


texts: How to measure voltage of each bank in a Marx Generator?

texts:
If I have a 10 stage Marx generator with each stage at 2.5kV, when I erect all the stages the last stage's negative terminal will be at 22.5kV with respect to ground.

If I want a voltage measurement of these capacitors what is the best way to do this?  I am worried about violating the standoff internal to my differential probes   since the probes would all share a common ground on the supply/measurement side.


texts: Lower current through different transistors

texts:
I'm building a small PIR driven circuit, currently a simple PIR activated light, and for this I'm using an RGB LED strip as I had it lying around from another project.  The diagram that follows works fine with a 2N7000 transistor.

Looking at its datasheet, the 2N7000 can only handle a small current which won't be enough when I increase the length of the LED strip - it'll need to handle something like 1A.  I tried replacing the 2N7000 with some MOSFETs I had lying around, an IRF540 and a ST 16NF06FP.  With either of these, the LEDs light but only  dimly.  Why is this and what can I do to fix it?


texts: Why not switching extra inverters with opposite MOSFETs in CMOS XOR gate?

texts:
Below you can see a CMOS XOR gate. I wonder why we do not change extra inverters like A' or B' with opposite MOSFETs.

For example, could not we just put the green construction in the place of red one?

Here is my design after switching all MOSFETs according to description I have provided.


texts: Is it right to apply superposition theorem to the RC circuit with non-zero initial capacitor voltage?

texts:
I'm having confusion with applying superposition to simple RC circuit with non-zero initial capacitor voltage.

simulate this circuit – Schematic created using CircuitLab

Consider a simple RC circuit series connected with voltage source of step voltage \$V_s=8u(t)\$, and let's say initial voltage of the capacitor is \$V_c = 2V\$.

It's obvious that the value of \$V_c\$ over time is

\$
V_c = 2+(8-2)(1-e^{t/RC})
\$.

But if I split the voltage source \$V_s=8u(t)\$ with two voltage sources \$V_{s1}=4u(t), V_{s2}=4u(t)\$, then the corresponding \$V_{c1}\$ and \$V_{c2}\$ will be

\$
V_{c1} = 2+(4-2)(1-e^{t/RC})
\$.

\$
V_{c2} = 2+(4-2)(1-e^{t/RC})
\$, respectively.

Then, applying superposition yields \$V_{c1}+V_{c2}=4+4(1-e^{t/RC})\$, which is different from

\$
V_c = 2+(8-2)(1-e^{t/RC})
\$.

Where am I doing wrong?

Is it wrong to apply superposition theorem to non-zero state of capacitor?


texts: why speed is not directly proportional to torque in dc machine?

texts:
I have a conceptual doubt about torque-speed relation in a DC motors. It's probably a gap in my thinking but I'm posting this question anyway.
As per me "in case of dc machine we see that the armature rotates because of the developed torque.so from the physical point of view it leads that if armature gets more torque then it will rotate at high speed; i.e. speed directly proportional to torque."
BUT why the reverse thing happens????? why speed is inverse proportional to torque....?/?
pls, explain physically......


texts:
The the most prevalent analogy for understanding electricity is the water hose one. I personally like this because it's very understandable but I have a question about how this works with resistors.

I understand that resistors will limit current which because of ohms law will affect the voltage but in a hose, decreasing the hose diameter (current) would increase the water pressure (voltage). Am I wrong on my understanding of this principle?


texts: Using a zener diode and a bjt to regulate voltage received by a controller

texts:
Okay, here goes…

I’m trying to create a circuit that will prevent low conductance (from rain water exposure) which occasionally shorts a particular switch, from triggering a controller input that the switch is sent to. The controller input needs to see ONLY voltages of 9-12V, but the rain water is causing a conductance of ~3V. — The controller sends a 12V signal that is read by the input when the switch is closed — So, I am trying to create a circuit that will output 3V only when the switch conductance is at minimum 9V+.

I’m including a screenshot of a circuit I think could work. I was having a slight problem during testing, which is difficult for me to explain because of my lack of knowledge/experience. But I think I might be simulating the partial conductance incorrectly. So, I’m only asking if you think this circuit should work for the intended purpose… or if something else might do the job better.

Hopefully all that made sense. Thanks for any advice. Please be gentle!

--------- Edit ---------

I am adding a hand-drawn diagram to try to clear up some vagueness my original post might've had. I may have used slightly incorrect terminology, so apologies for that. But what I'm basically trying to accomplish is to keep the voltage received by the controller well below 3V until the switch is essentially closed, as opposed to just getting moisture across its terminals.

Going forward, the the switch will be replaced. However, this fix is more for the field... like if somebody had the device and needed to just add a simple attachment to it to correct the issue, without going to a shop to get it serviced.


texts:
I am looking for a single BRIGHT LED light.
I'm using:

1 red 5mm LED
AC adapter of 5V 2.5 amps
1 ohm resistor

It works, but doesn't seem very bright.
Am I correct or completely wrong?
What is the best color LED and resistor to optimize output using the 5V power supply?
FYI this is my 1st attempt of this type. I appreciate any feedback and advice.

Image enclosed.
Looking for a BRIGHT light.


texts: Off delay timing function for a relay, using a Arduino

texts:
Heres my following circuit: https://imgur.com/a/qTV8zgR
Here's the timing function I want to implement; https://www.google.com/search?q=off+delay&client=opera&hs=bme&sxsrf=ALeKk02eXHrXUiuMNRkKWItoB9XjcOx3MQ:1593207461707&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjuyLumuKDqAhUIuRoKHawTBvwQ_AUoAXoECBgQAw&biw=1920&bih=939#imgrc=oOvFUPbuLDG-ZM
I want to implement an "off delay" digitally. I got the "on delay" and the " triggered on/off delay" but am having a hard time figuring out how to implement the "off delay" using a microcontroller.
Q = Is it possible? If yes how to implement a off delay using a micro controller and no imtermediary circuit to hold power like capacitor or something.


texts:
I have a string of multi colour LED lights - two colours are connected in one polarity, and the other two colours are reversed. They come with a controller that is able to turn all the LEDs on at once by reversing the polarity at a high frequency.

I'd like to get rid of that controller and control them with my own microcontroller. I'm looking for a part or circuit design that could reverse the polarity of that load based on a digital high/low signal. I could then feed this a PWM signal from my micro at a 50% duty cycle.

I had thought about using a H-bridge (I have some L293Ds to hand) but that on its own won't quite do what I want, as I have to bring one input low and the other high.

Could anyone point me in the right direction? Perhaps I'm just thinking about this in the wrong way.


texts:
I'm building a light indicator system with four states (All lights off, Red light on, Amber light on, and Green light on). I want to be able to go from one state to the next with just one button press, which rules out having individual on/off switches for each light, and also a rotary switch because going from Green back to Off would require switching on Amber and Red. A momentary push button is the preferred option.

I've been looking at Set/Reset Latches with NAND gates similar to the "Sequential Logic -> Flip-Flips -> SR Flip-Flop" example on http://www.falstad.com/circuit/. This example uses two two-input NAND gates where one input is pulled high and grounded on button press, the other input is tied to the output of the other NAND gate. To get this to work with four states I was thinking about using two 4012 Dual 4-input NAND gate CMOS integrated circuits, but the wiring becomes significantly more complicated compared to using a simple rotary switch.

Is there a simple way to achieve this functionality, with a type of mechanical switch or an integrated circuit that just takes the 4 inputs and has 4 outputs?


texts: How is unsigned integer max implemented in hardware?

texts:
I'm working on a design that involves a lot of max functions (and max functions as arguments to other max functions).

In an effort to simplify the hardware design I was wondering how max is implemented in hardware?

Mathematically, Max(a,b) can be represented as [(a + b) + abs(b - a)]/2.

Is this how its implemented in hardware? (i.e. in stages; addition, bit shift division, etc.)

If so, how is the absolute of the difference calculated?


texts: Best choice between flyback diode or an RC snubber

texts: I have a motor that has a 24 Vdc (15 ohm) brake attached that tends to weld / burn up the contacts in the ice cube relay that controls it after a year or so. I was wanting to put some protection on it. Would it be better to put a flyback diode across the brake or an RC snubber across the relay contact?


texts:
simulate this circuit – Schematic created using CircuitLab

How does the capacitor behave here?

I tried and the led flashed. Does the capacitor work like a diode after charging?


texts: How does the 3.3V output work in this PSU circuit?

texts:
I am trying to understand how computer PSUs work.
I found the following circuit in Wikipedia and I noticed that, unlike the 12V and 5V outputs, there is no winding in the transformer for the 3.3V output. Instead, a coil is connected to the 5V secondary before the diode.

I have some experience in swith mode power supplies but I did not see this circuit before.
How does this 3.3V output circuit work?


texts: how to choose diode for PWM of high amperage solenoid?

texts:
I'm making a pulseable solenoid circuit via PWM at around 20 hz.
THe solenoid is a heavy industrial type that pulls a whopping 18 amps.
My snubber circuit gets hot and burns up as the current is too high for the zener and the schottky.
What can I change to allow this circuit to manage the high current fly-back from this solenoid?


texts:
The IC ICL232 needs some capacitors. Should these capacitors be ceramic or any other type?

When does the capacitor type matter?


texts: Unexpected output for a passive filter circuit with low ohm resistor

texts:
With a simple filter circuit (either high pass or low pass), I'm seeing unexpected behavior in the o-scope output when I use a resistor with a low ohm value (e.g., 10 Ohms). Since a picture is worth 1000 words, here's my o-scope readout at the cutoff frequency (with a waveform generator creating sin waves at 160 KHz, w/amplitude of 11 V):

Here's the high pass filter circuit design I'm using:

There are probably several issues, but from my POV at least two issues appear relative to other circuits I've built and tested:
1) The dual sin waves offset by half a cycle, one faint and one 'blurry'. Note: the 'faint' wave flickers rapidly and is not always there.
2) The amplitude is a fraction of what I would expect (and what it is with other circuits I build w/higher ohm resistors). In this case I was expecting a voltage of ~8 V.

If I try other higher ohm resistors, they seem to work fine and I get readouts that have Bode plots in-line with expectations (e.g., 22k Ohm, 500pF for a cutoff of 14 KHz has a clean readout with a drop in signal that matches expectations).

Question: Why does this behavior occur when using a low ohm resistor, while higher ohm ones work fine?

Any help or reference links that will help me understand would be greatly appreciated. Apologies if I missed something basic, new to hobby electronics.


texts:
I designed a simple triangle wave oscillator based around a switchable curent soure. It works for a few cycles, then it becomes unstable and finally stops working altogether. Why is this?

If anyone wants to simulate this - here is the link.

One other thing - occasionally, the osillator will manage 20 cycles, other times it won't complete a single one. Why is the simulation apparently not deterministic?


texts:
When I select multiple designators and when I select "properties" - only one designator changes. I have same problem with setting other parameters on multiple objects.

How can I change all existing designator font sizes on PCB in Altium?


texts: Why are contactor coils connected to two different safety relay outputs?

texts:
When looking through a manual for a safety relay, I began to wonder why the coils of the load contactors (K3 and K4 on pages 14-15) are always connected to two different NO contacts of the safety relay?

Why not just connect K3 and K4 to a single safety contact, in parallel? Since the safety contacts are internally a series of redundant monitored contacts, this doesn't seem like it would compromise the system's safety in any way.


texts: Calculating charge when current is a piecewise function

texts:
The current is defined as follows:\$\$

\$ i=\begin{cases}
      4 & 0<t<1 \\
      4t^2 & t > 1 \\
   \end{cases}
\$

The goal is to calculate the charge from \$t=0\$ to \$t=2\$ s

What I've tried:
I've tried integrating both parts.

\$\int 4dt=4t+c\$
\$\int 4t^2dt=\frac{4}{3}t^3+c\$

Then I fill in \$2\$ in the second integrated equation and \$0\$ in the first equation, and I subtract.
I get \$\frac{32}{3}\$ coulombs as the answer, but I should get \$\frac{40}{3}\$ coulombs.

Where did I go wrong?


texts:
In this paper
"Critical Bandwidth for the Load Transient Response of Voltage Regulator Modules",
they have an equation about average inductor current during the step-down transient.
They don't show the derivation. How to arrive at this equation ?

... the  step response  inductor  current  with  voltage-mode  control ...
With the loop closed,the oscillation frequency is modified to the level of the control bandwidth,  which  is  much  faster  than  the  condition  in  the open loop.  The inductor  current  rising time  is approximately a quarter of the oscillation period. Thus, the average inductor current during the step-down transient is about


texts: LED driver PT4115: how to avoid arc around IC pins?

texts:
I built a LED driver with PT4115 IC. The board lighted LEDs up but sparks appeared around SW, VIN & GND pins after 10 seconds and the phenomenon didn't damage the IC. I recorded it by my mobile phone.

Spark around pins

Below is the schematic and the PCB board:

I removed R2, D2 and R3 so the DIM pin is floating. It should help us to concerntrate to this problem.

I checked every pin of the IC and didn't find any short or something wrong. I thought that something conductive around these pins and start to conduct after 10 seconds. It is very strange and confused me.

Any good suggestion?


texts: How does USB 3.0 negotiate power states?

texts:
I noticed, in another question, a comment regarding USB power states.  I know that USB 2.0 negotiated power by tying the D+ and D- lines to specific voltages but I can't seem to find any information on USB 3.0 power state negotiation.

Since USB 3.0 has two sets of D+/D- lines, and I can't seem to find any information on this, does it either:

Pull both sets of data lines to specific voltages
Send actual data through to ask for power instead of setting static levels
Just pull one set of data lines to the specific voltages?
Or something else?

Bonus points if you can find the actual voltage levels or data for the different states.


texts: My question is this. I'm using this ic mppt SM72445 along with a 250 watt solar panel, mppt output configured to 50.4 or 51 volts, 12-cell lithium-ion battery pack and bms, if the load is less than the output of mppt the battery will be charged, but what happens when the load is greater than the mppt output and there is a voltage difference between the mppt output and the battery? example ; mppt output = 50.4V 5A / battery pack = 46.8V 3.9Vcell * 12 / load = 10A my doubts are for the difference in voltage between the two sources, mppt and battery in parallel


texts:
Firstly i want to mention that I am not even close to an engineer or i have absolutely no experience with electronics. Here is my case. I have an old laptop with broken power button. It is not just the button, the whole circuit for the button is broken from the motherboard. I played a little bit and I found the 2 dots(on the mother board) that i have to connect in order to turn on the laptop. Here comes the idea. I want to solder wires to the dots and then connect them to a a socket like (Mono Chassis Socket). I am not really sure if this is possible because the socket basically has 2 outputs so I want to avoid using 2 different jacks. Wait a second I forgot to mention why i want to use jacks. So, basically i want to have an external BIG button(or switch) which i will be connecting to the socket via male jack for establishing a connection between the dots. I know it is a simple thing but can you lead me in the right direction?

What socket should i use(it have to be really compact one)?
Will it even work with jacks?
Perhaps a different more interesting solution?


texts: How to avoid SD Card and W1500 SPI mixup on the Ethernet Shield?

texts:
In an answer Kevin Mark points to a solution/reason for the usage of the Ethernet shield together with the SD Card. The documentation says that SD Card and the Ethernet chip both share the SPI bus and that I have to set different pins on HIGH to tell the Ethernet shield to use the Ethernet OR the SD Card.

How would such a solution look like?

pinMode(4, OUTPUT);
digitalWrite(4, HIGH);

// Now I can use the SD Card?

pinMode(10, OUTPUT);
digitalWrite(10, HIGH);

// Now I can use the Ethernet (W5100)?

// Do I have to (re)set 4 to LOW?
// Any possibility to use both at the same time?
// Can I use the Ethernet/SD Card without the setting of pin 4 or 10?
// Why is this missing on the official code examples? Is it really necessary?


texts: Can USB data transfer between Arduino and Android with the 5V power line disconnected still work?

texts:
I am using an Android tablet to talk to an Arduino board in a project which will need to run for many hours. It is all being powered off one lead acid 12V battery.

I would like to run the Android off its own power line so I would have the D+ and D- and GND connected straight to the Arduino and the power coming from another reg (of course both using same ground). This is to ensure that I can send enough current to power the Android.

But I also want to have a switch (maybe a FET or even relay or what not) in between which can cut off the power all together to the Android and still maintain a data connection. So that I can even further save power by running the Android to a lower power threshold until I begin charging it.

Is this possible?


texts: Can a single potentiometer be hooked up to multiple fans to control their speed?

texts:
I have recently learned about potentiometers and their "variable resistance" porperty.

I am looking to hook up a Potentiometer in order to control 4 12VDC Fans.

I am not sure if that is a good idea, but I would like to control all of them at the same time.

I currently have a PWM splitter that can split up to 8 PWM fans, so i know it's possible in some respect, but not sure if the resistance in the potentiometer is split across each 12v dc, which would affect which Potentiometer I have to buy I would assume?

Also, my fan has a 3 pin input (red, yellow, black) which, according to Which wire is negative on this PC fan?

Says "7v sensor" or "tachometric singal" so I'm curious exactly what that is for?

I do have a plug that split out into red/black, so I guess the Yellow has some purpose that isn't super important then?

Any advice is appreciated, thanks!


texts:
I have done few BLDC motor controllers with trapezoidal modulation and they work fine. Now i'm trying to build another one with space vector modulation but as it doesn't work well i'm getting more and more confused.

I have 3 PWM signal pairs (total of 6 signals) driving 3 phase integrated FET driver. What i need to know is how exactly should the 6 PWM signal waveforms look like for a space vector (SV) modulation. Nearly all the SV images in internet show only the 3 signals and i am not certain what they are exactly (phase output, high or low control signal?).

The first question is:
Should the high and low PWM signals of one leg be inverted with each other? In other words - should one of the leg signals always be active (active = FET conducting) ? Of course some dead-time is needed.

This solution didn't work well because both motor and driver got very hot even at low speeds. Maybe i have something else wrong, but if i just theoretically think of this (and look at signals with logic analyzer) then some things doesn't make sense.
Let's say i want to have low duty cycle (10%), then according to SV PWM all 3 low side FET's are ON (conducting) most of the time. But that means the motor is actually braked (slow decay)!

It really confuses me because this logic means that polarity of each phase is swapped on every PWM period. Also - with trapezoidal modulation one leg is always undriven (high and low FET are both off), but that's not the case in SV. Or do i need very high PWM frequency to get smooth output? I'm using 16 kHz because driver can't handle more by spec.

Then i did an assumption that if SV phase should be positive then i pulse the high side PWM signal and keep low side inactive. And if phase should be negative then i pulse low side PWM signal and keep high side inactive. My theory was that the motor should free-wheel when doing like that. But it didn't work well. Also i suspect in such way the inducted current flows through body diodes...

Anyway, i don't want to just try. I'd like to know which way is correct and then continue the development process.


texts: Doing nodal analysis on a circuit with a capacitor.

texts:
I'm looking at with the switch open. I get

While going through the nodal analysis I get

V1 = 3V

Does that mean current across the resistor would then just be 1mA?


texts: Opening serial port for reading, when data is already flowing

texts:
I have a drummachine (Roland TR505, but all of this would be true with any other device) sending a byte 11111000 (Timing Clock MIDI message), 48 times per second, to a MIDI OUT port. It works well.

I'm reading MIDI signal on my electronic device via software with classical serial port reading techniques (at 31500 baud, etc., I totally respected the MIDI standard in my electronic schematic).

[ROLAND TR505]  =====MIDI cable=====> [MY ELECTRONIC DEVICE]

I have a tricky situation:

If I power on my electronic device and I let the serial port reading software start, and then I power the TR505 on, it works : the flow of bits coming to serial port is correctly interpreted. It works perfectly.
If I power the TR505 (i.e. the bits are already flowing to serial port), and then I power on my electronic device, there is a problem : probably my device starts reading serial data in the middle of a byte, i.e. data is wrongly interpreted.

Question: when you connect a device already powered on, already sending data to another device which listens serial port, how to ensure that the listening device won't start in the middle of a byte?

i.e. if the bits flow is:

...0111100001111000011110000...

how will my device know it's byte1=11110000 and not byte1=01111000 ?

Here is the software code in Python:

import serial

ser = serial.Serial('/dev/ttyAMA0', baudrate=38400) # Note: there's a well known hack in /boot/config.txt to make this work at 31500 baud, which is normally not supported on Raspberry; in short baudrate is not the problem

while True:
    data = ord(ser.read(1)) # read a byte


texts: How to cut costs when fabricating large PCBs?

texts:
I've looked online at PCB fabrication companies, and they invariably price their boards according to the size of the board as the primary factor.

Why is this? The physical board itself isn't that expensive, is it? I'm guessing it's because the size of the boards dictates how many they can produce simultaneously, and that's the primary limiting factor in their profitability - Is that right?

Anyway, is there a way to keep the costs down when fabricating large (~8x10 in.) but sparsely populated (~50 components) boards (other than just ordering from the cheapest Chinese factory I can find)?

It seems silly to pay $50 for a board that's only gonna have $10 in parts on it.


texts: In Verilog, does an event control always execute once at the beginning?

texts: As illustrated in the image below, there is an event control with the variable r (for reset). I have not initalized c in  the top module, but it shows in simulations that it starts at a low state. The only reason I think this is is due to the c output being set to 0 from the always @(r) statement. Why does this execute if r does not change? Or is it technically 'changing' when I initialize it in my simulation?


texts:
Do the electrons at the anode (negative end) of a battery flow through the copper to the cathode end or is it only the copper atoms electrons that flow to the cathode end of the battery or does both happen?

Another one that puzzles me is do the electrons at the anode end of the battery ever strike the copper atoms valence electrons? And if so is that what causes heat? Or is heat produced when the copper atoms strike each other when they randomly zigzag to the positive end of the terminal?

Last one is when the copper atoms lose electrons because it's attracted to the positively charged terminal. That copper atom becomes a cation how does current flow if that atom has a net positive charge?


texts: Transferring a 1MB bitstream to a FPGA and reading it out

texts:
I am using Spartan 3E Starter Kit and I need to store a sequence of bits around 1MB long. It is a constant bitstream and will be known to me at the time of programming the board. I need to be able to read out one bit at a time from this stream. I believe I need to put this sequence of bits in the flash memory on the board since I need it to be persistent even when power is not given to the board. Any clue how that is to be done?

Can someone point me to a tutorial on how to put this data on the flash and how to read it out to some other module that processes it?

Xilinx Devices:

Spartan-3E FPGA (XC3S500E-4FG320C)
CoolRunner™-II CPLD (XC2C64A-5VQ44C)
Platform Flash (XCF04S-VO20C)
Clocks: 50 MHz crystal clock oscillator

Memory:

128 Mbit Parallel Flash (28F256)
16 Mbit SPI Flash (M25P16)
64 MByte DDR SDRAM (MT46V16M16)


texts:
I've see people asking about transformers in series to get high voltage but what about transformers in series to get 6v, 600amps?
I'm at 3v 600 amps currently but I want to bump up the voltage without losing amps.


texts:
I'm trying to use a DC-DC converter to charge a mobile phone.

This is the converter....TRACO 12v-5v converter

The converter is relatively low power, (5w) and can supply a maximum of 1amp. Testing with both a USB voltmeter and a multimeter indicates that the device is correctly wired and producing 5v.

However, when I plug in my iPhone (or tablet or any other mobile device) there's no sign of any actually charging taking place. (I would normally expect to see a little lightening strike zig-zag symbol appear on the battery)

Is this because there is a minimum current requirement to power the mobile device?
Is the device likely to be not charging at all? or is it probably charging ok, but at a very slow rate?

I know that if I were charging a lead-acid battery at a very low current then the battery would still charge, albeit very slowly.

If there is a minimum current requirement for my mobile device, what's it likely to be? I know I can buy higher current 5v supplies, but would prefer to know exactly what I need before hand rather than just buying DC-DC converters on a trial and error basis.

UPDATE - I have left the 'data +' and 'data -' unconnected, and simply connected ground to ground, and Vcc to 5v. My understanding (perhaps wrong) is that a USB device should be able to charge itself with this configuration. It's only if attempting to fast-charge a device 'data +' and 'data -' need to be connected to anything.


texts: Using a chip with two different power input requirements

texts: I am working on a design that uses the TI TMDS351 chip. (Datasheet: http://www.ti.com/lit/ds/slls840b/slls840b.pdf ) This chip requires both a +3.3V in and a +5V in. Now, every other device on the board operates at 3.3 so power to the board is provided at +5V and regulated down to 3.3v before being sent to the power plane layer. For the 5v in, can I just have a line directly to the 5v pin on the bottomost "slow signal" layer? Will that cause emi problems?


texts: Need help identifying SOD-123 packaged Zener diode with WG G0 marking

texts:
I'm looking for help identifying a SOD-123 packaged Zener diode with WG G0 marking like the one in the photo.  The board has quite a few of these with one of them completely burnt.  The closest I've come across is a BZT52C11, but it doesn't quite have the same markings.
Any help is appreciated.


texts: Current through an ideal inductor at steady state

texts:
Find the current through the \$\mathrm{5 \space mH}\$ inductor when the circuit reaches a steady state

When the circuit reaches a steady state, a current of \$\mathrm{4 \space A}\$ will flow through the resistor (since voltage across the inductors are zero). The inductors themselves are ideal, and have a resistance of \$\mathrm{0 \space \Omega}\$. Thus, the current through each inductor should be \$\frac 42 = \mathrm{2 \space A}\$. However, my textbook seems to disagree and says that the current is \$\frac 83\$ A. I am aware that \$X_L = \omega L\$, but that is for an AC circuit and not a DC circuit.

Why is the current through two ideal inductors in parallel (at steady state) divided in the inverse ratio of their inductances?


texts: How do I view the pin numbering scheme in an Altium library?

texts:
I use the misc library of Altium, for example the capacitor and resistor symbols and footprints. Later, I need to replace the footprint with my own. How are the pins numbered in the misc library?

How can I open a component from the Altium-integrated misc library to verify which pin of the sch library symbol is numbered 1 or 2?


texts: Powering Atmega, DAC and Bluetooth in Car

texts:
I'm looking for a proper power supply schematic which would fit my needs and would have all required protections (overcurrent, overvoltage, reverse current, etc) for use in car. I want to power Atmega 328p (3.3v@8MHz), PCM5102 and CSR64215 module with it. They all should be powered from 3.3V. Any suggestions?

So I've decided to use DC-DC switching regulator for the first stage and multiple LDO's at the end which will bring the voltage down to 3.3V and power rest of the circuit. For the first stage I chose BD9778F switching regulator with built-in power MOSFET which features wide input voltage range (7V-35V). For the end part I'll probably use AMS1117 LDO's. I already draw the schematic for the first power stage and would like to get some feedback from you if possible. Thank you!


texts: Representation/Effect of a delay element in the frequency domain?

texts:
If I have a simple RC low pass filter in which the output is taken across the capacitor, with a particular cut off frequency say x Hz.

Now if I were to introduce a delay in the path of the resistor, how will the bandwidth of the LPF change? How do I visualize this delay in the frequency domain?


texts:
Are shoes like this used in professional labs or is this just a gimmick?

http://www.esdshoe.com/products/Lightweight-Classic-Mid-High-ESD-Composite--Basketball-Shoe-%252d-Men%27s.html


texts: How is this 3 VAC power supply charging this 18 VDC battery?

texts:
My cheapo 18V Black and Decker cordless drill recently died, and thinking I could maybe fix it, I took everything apart and then couldn't figure out how it was ever working in the first place! Here's a picture of the internals:

The wall wart is 3.6 VAC, 200 mA output, which runs straight to the terminals of the 18 VDC battery at the bottom of the picture (and I've taken the battery apart to make sure and there is no circuitry inside, just battery cells). This seems completely odd, and I can't figure out how the battery ever charged while it was working.

The only thing I can possibly figure is that the switch housing also contains boosting/rectifying in addition to the PWM etc... to run the motor at various speeds according to the depression level of the switch. There does appear to be a transistor attached to silver colored heat sink, and I'd imagine they could be implementing both the PWM and a switching power supply with that, but that seems ... advanced for a cheap B&D drill, or maybe not? It also seems strange that the boosting circuitry would be connected to the same leads as those coming off the VAC power supply.

Measuring with my multimeter, I get 4 VAC from the wall wart open circuit, and connected to everything I measured 1.7VAC at the battery terminals, and 1.8V DC. (but again, this system is broken in that the charger no longer seems to work.)

Can someone shed light on how they think this setup is supposed to work? (and bonus points if you can think of what broke?). Thanks!


texts: How to determine vias and through holes from 4-layer Gerber files

texts:
I'm trying to understand the difference between the vias and plated through-holes in these reference Gerber files. On layer 3, I don't understand why there are so many holes (vias)?.

Why are some holes on layer 3 and the NC drill not on the other layers?

And the other holes in the NC drill that don't appear on any of the other layers, what are they? Vias? (I can see them in the final render.)

Layer 1

Layer 2

Layer 3

Layer 4

NC drill/thru-hole

PCB top render

PCB bottom render


texts: What is this component in series with my water heater's thermocouple?

texts:
The other day we had our water heater go out and the issue was diagnosed to a faulty thermocouple.  When the repair man removed the faulty thermocouple he noticed the following disk-like component in series about mid-way down the copper tubing.

This device had one of its two terminals broken off of the bottom (not shown) and was most certainly the cause for the failure.  The repair man's replacement thermocouple had no such device inline and when asked what this was he replied it was a transistor.  I very much doubt this device is a transistor as there are only two, not three, terminals but I didn't want to argue.

So, what exactly is this component and what is it's function?  As stated, the replacement thermocouple does not have this but it appears to be functioning correctly.


texts: Measuring current with a multimeter - What did I do wrong?

texts:
I wanted to measure the current of a generic lithium ion battery charger. I set I plug my red lead in the A 10A max fused and black into COM. The charger is rated at 600 mA and my other lead plug is fused to 250 mA so obviously that wouldn't work.

So I put my leads on either side of the battery and there's a small spark. Did I break something?


texts:
I have a PCB from a humidifier which ceased to work. It could be water damage but I am not sure.

I sm unsure if it is the transformer or some capacitor.
Please advise if I can repair or if it is better to take the good parts and throw away the rest.


texts: Designing multiple buck converters on a PCB

texts:
I have an application where I need 12V, 5V, and 19.5V from a 24 V power source. I am intending to use
 3 XL4016 buck converters and proper fuses that supply the correct voltages to the respective devices. Currently, all the converters and fuses are all over the place and I am wondering whether I can put all the buck converters, fuse holders, and connectors together in a custom made PCB? If so, should I be designing a buck converter from scratch or can I use the schematics diagram(of XL4016) to build the PCB?

Any other design advice for the above scenario is appreciated as well!


texts:
I am trying to use a comparator to detect an open circuited signal.

If I place a pull down resistor on the input as shown below, will the comparator operate correctly when Vin is removed and the inverting terminal is left open?

I am concerned that offset/bias voltage/current requirements will not be met if I use such a high value pull down resistor.

Edit: to be more clear, the reason I am asking this is because I used an extremely high impedance source (1M) as an input to to the comparator and the comparator did not function as expected. I suspect this was due to there not being sufficient bias current.

simulate this circuit – Schematic created using CircuitLab


texts: Condom packages often say "electronically tested". How can you test a condom electronically?


texts: What do you call a flexible rubber boot that protects wires?

texts:
I'm not sure if this is the correct site to post it on, but it seemed closest related to electronics.
I'm diy-ing a laptop and I have a couple of 15-pin FFCs that have to be flexed a little over 100 degrees (not a completely sharp bend though) in one direction when the laptop is opened. I'd like to provide some extra protection to the wires from the elements and whatnot, as it will be a ruggedized type laptop, as well as give the cable some extra rigidity so that it reduces the chance of it being pinched upon closing.
What I'm looking for is a (preferably) rectangular rubber boot protector which is 'collapsible', like the type found between a car door and the frame. Is this/what is the correct term? I can't find much on google except for some (round) cable end stress relievers.
Edit- sorta like this thingy:


texts: How do I tell sleeve from sleeve shunt on this connector?

texts:
I need to change a DC jack to a different one (with long bushing).

I'm not to sure which terminal connector is what from the manufacturer's diagram.

The DC jack is a L712A from Switchcraft (Manufacturer Ref)

And this is the diagram they provide: http://www.switchcraft.com/Drawings/L712A_cd.pdf

How do I tell which one is which?

Edit: Here's a photo of the jack if that's any help:

Edit 2: Photo of the other side


texts: What data is stored in an eeprom that’s not in the flash memory?

texts:
I’m wondering generally what information is stored in an eeprom that’s different than what’s in the flash drive that contains firmware?

Mostly in mobile devices. Does the eeprom contain user settings like wallpaper, app locations etc or is there something else specific to hardware like IMEI etc?

Is the eeprom in a mobile phone comparable to bios in a pc or used differently?


texts:
In my C18 compiler (PIC, PIC18F66K22)
The following code:

char *message = "Test";

Leads to an empty string.
It's because "Test" would be saved in ROM, learned that the hard way...

But I believe it's valid C to do char *message = "Test"; so C18 is not compliant with the C-standard or how could I best describe this?

Is there an easy (withouth copying from ram to rom or using sprintf to put rom text in a ram variable?) way to specify that the text should be RAM?
I tried:

ram char *message;
message = (ram char *)"Test";

Without succes.


texts:
I'm doing a project in which I use DDR interfaces to transmit and receive data between different FPGAs. The FPGA transmitter will send data at 125 MHz and the receiver will use 250 MHz to sample the received data.

For the project I am using the MachXO2 family of Lattice. In principle, I had thought of using an external 125 MHz oscillator to then pass it through the internal PLL and convert it to 250 MHz using the CLKOS output. My doubt is that in the datasheet it specifies that the DDR interface requires the use of a dedicated PCLK pin. I have made simulations of the code, and after trying to implement it, in the synthesis phase I get an error if I try to connect the CLKOS output of the PLL to the DDR receiver.

My question is, how can I approach this problem? Can I somehow use CLKOS from the PLL or is it impossible? Should I look for an external oscillator of 250 MHz and connect it to a PCLK pin?