texts: GPS splitter with 200Ω DC load and 50Ω RF impedance on all ports

texts:
How can the GPS400 signal splitter provide a \$200~\Omega\$ DC load and \$50~\Omega\$ RF load to GPS receivers on all four ports?

Most GPS receiver modules require an active antenna.  As a result, most receiver modules provide a DC bias on the RF connector to power said active antenna.  These modules typically implement an "antenna fault" detector circuit that checks for a DC load.  The assumption is that if there is a load, the the active antenna is present.

When working with a simple:

  GPS module <-> cable <-> Active antenna

everything works as expected.

The problems come up when there are multiple GPS receivers that all need to use a single active GPS antenna.  In my case this would the antenna mounted outside the building with a single cable running in to the lab.

I was able to find the GPS400 splitter to do just what I need.  The GPS module that will power the antenna is connected on port 1.  Ports 2,3,4 are then presented with a dummy 200ohm load to prevent an "antenna fault" detection on the remaining modules.

What I understand:

It uses a Wilkinson Splitter to split the RF signal while preserving the 50ohm input impedance.
The use of DC blocks on ports 2,3,4 to prevent the DC bias from passing through to the input port.
The use of a \$200~\Omega\$ resistor to ground which presents a DC load for ports 2,3,4.

The closest to a schematic from the datasheet is this:

What I do not understand:

Why does this configuration not affect the output impedance on ports 2,3,4?
If there is a \$200~\Omega\$ resistor to ground in parallel to the \$50~\Omega\$ antenna, shouldn't the output impedance be \$40~\Omega\$ instead?


texts: Implications of using a 145 ohm cable for RS-485

texts:
My current workplace has made some custom cables that have conductors for DC power and conductors for for RS-485 communications in the same bundle. My predecessor apparently had the cables measured to have a 145 ohm characteristic impedance. I believe most RS-485 drivers specify 120 ohm cable, so what will the implications be for using this slightly mismatched cable? Data rate is 57 kbit/s.

Also, the DC power wires that are in the cable are used to power brushless DC motors at 36 V and about 8 A. Should I be concerned about induced noise on the data cables? The data cables are not separately shielded and are not twisted pairs either.


texts: Laser Diode and LEDs in parallel: LEDs don't light

texts:
I have a 3x1.5V battery pack (AA alkaline). It's fresh and with no load sits at 4.8/4.9V.

In parallel, I have 3 LEDs, each with their own resistor. That works fine..

I can also switch in a 5V laser diode module. That also works fine..

But if I attach everything at the same time, the laser diode module is lit, but not the LEDs.

I suspect/hope this is some fairly straightforward concept - but if the battery is sitting as it is, everything works well and these are fairly low-power devices, all connected in parallel - I don't understand it.

Can anyone guide me in the right direction?


texts:
We’re working on a product that makes use of USB HS, and are having some connection and consistency issues.
Originally, our product was USB FS-based and we had no connectivity issues; with this second iteration the design was adjusted to use USB HS with a new MCU and the same cable. The ergonomics of the cable in particular are important to our application, rendering typical USB cables with more robust shielding unsuitable.
The cable’s specs:

A  2-meter long run of Tensility 4-strand cable
(not twisted-pair, but has a lay length of around 3.5cm)
Gold-plated USB connectors and a 4-pin Molex
Picolock (gold-plated on both male and female ends) on the device side.
Inductance of the cable is 1.2uH, capacitance is 97pF, resistance is 0.92 ohm, and impedance is ~111 ohms (which we believe to be relatively close to the USB spec of 90 ohms).

On some systems, the USB HS connection will work consistently and flawlessly each time. On others, it will be port-dependent with success rates ranging anywhere from 30-80%.
Issues seem to occur in decreasing frequency with cable lengths around 2m to 1.6m, and are mostly resolved at around 1.5m. Additionally, any of the following seem to improve our device’s performance:

Shielding the cable in aluminum foil
Twisting the cable (~10-20 turns in the 2 meter length) axially
Creating a twisted pair out of D+/D- on a fully stripped cable (with no shielding)

We have access to some rudimentary test equipment, namely an oscilloscope (Siglent 1104XE), multimeter, LCR meter (DE-5000), and a digital logic analyzer if there are any relevant measurements that are missing.
We have many cables ready to go -- enough for the entire foreseeable run of the product -- but production of the boards is done iteratively in smaller batches with no large batches yet produced. With that in mind: are there any board or cable- related mitigations that are worth investigating in our case?


texts: Audio Amplifier Design (CE Amplifier - Class AB Power Amplifier)

texts: I am trying to design a Audio Amplifier which provides a gain of 20db (10V/V). I have managed to design the following circuit but the output voltage gets clipped and clamped. Please find the schematic file at sendspace.com/file/i5rw9n .


texts:
My Wife's hair straightener broke, after I took it apart i noticed that a connection broke to one of the heating elements so it never heated up. These heat up to 350F.

The solder joint will be on the heating element.

How can I keep my solder joint from melting?


texts: What is the role of the BJT and capacitor C2 in the capacitive power supply circuit shown below?


texts: With limited components, how do I emulate a reverse-biased zener diode?

texts: I understand that reverse-biased zener diodes don't conduct at all until they've reached a certain breakdown voltage, after which their voltage drop remains constant.  I want to use this property in a circuit, but I don't have any zener diodes.  Can I emulate one with just resistors, transistors and capacitors?


texts:
Assuming base b=2, is there a particular advantage in terms of performance when comparing SRT division to non restoring division?

In Non restoring division, for each iteration, the output digits belong to the set {-1,1} which implies that an addition or subtraction is always performed.

In SRT for each iteration the output digits belong to the set {-1,0,1}, where the 0 has the meaning of not performing operation when the partial reminder is particularly small,

Is the only advantage the fact that it allows to bypass some addition subtraction? Does just this thing make the whole division faster? I also suppose that full advantage can be taken if one design such divider asyncronously, am I wrong?


texts: How to set timeout using AT commands and ELM327

texts:
Hello I'm working on Android App that can read data from CAN bus. The interface I'm using is ELM327. The problem is that this interface uses Bluetooth. So I cannot read all the data from CAN bus because after half of the sec the buffer is full. The the interface is v. 1.4.7. And I am using Bluetooth terminal on Android. The commands I used:

ATZ -> to reset the interface

ATH1 -> set header

ATS1 -> set spaces

ATL1 -> Linefeeds on

ATAL -> Sets long message

Then I want to set delay for lets say 1 sec

ATST FF -> Set delay to 1 sec

ATSP 6 -> I'm using CAN so this is protocol no 6

ATCM 170 -> setting mask

ATCF 176 -> set filter

ATMA -> Monitor all

And using that there is no delay.. Is there any way to 'slow down' a little bit this lets say flow control? It is very important because without delay the buffer is full in half of a sec. I will be grateful for any help! Thank you M.


texts: What efficient techniques exist for rectifying high voltage?

texts:
I want to rectify 120V (mains North America) at a relatively high amount of current (5 amps), so naturally my first idea is to just find a bridge rectifier. After finding one capable of the current and voltage, I realize that the power dissipated would be high enough to warrant a heat sink due to the large forward voltage of the diodes.

V(fwd) = 1.1v per diode
2 diodes are always in conduction so 2.2v drop
2.2 * 5 = 11 watts of heat dissipation

I started looking into alternatives but I did not seem to come up with much. So, back to the question, what solid state techniques exist to rectify high voltage AC that remain efficient even under high currents?


texts:
We are developing a mobile application for smartphones (Iphone, Android, BlackBerry, etc) and want to allow navigation at indoors.

We can buy and place indoor gps antennas but will this solve our problem and let us to navigate users?

I searched a lot and found some systems; but they are bundled with chips and antennas. But we couldn't attach chips to users phones.

So do you have any suggestions?


texts:
This isn't asking the equation to determine the necessary resistor for LEDs, but more asking the general practice for selecting them.

I've seen multiple circuits that have used much higher resistor values than what I would deem to be necessary. For example, I have seen a design that has used a \$330\Omega\$ resistor for a red LED with a forward voltage of \$2V\$, and forward current of \$20mA\$ on a circuit with \$5V\$ supply. By my calculations that's twice as high as it needs to be (\$150\Omega\$).

I've read else where that this resistor is the 'playing it safe' choice, in that they use that wherever and can be confident they wont blow the LED. But is there any other reason behind it? Other than purposely halving the LED brightness.

Perhaps this prolongs the life of the LED? In my circuit I've selected the theoretical correct resistor value for each LED, but want to know if there's a practical rule I'm missing as the resistor values are quite small at times.


texts: Induction in transformer coil relationship to magnetic field lines in core

texts:
From my understanding is the process of induction described by a magnetic field line which approaches a wire perpendicular and creating an local electric field in it which can be detected which measuring electrical voltage at the ends of the wire.

What bothers me is this process in a secondary transfer coil. The magnetic field lines are inside the core and do not cut the coil wire at the surface of the core.

Does one need to differentiate between induction by magentic field lines cutting a wire perpendicular and the sum of magentic field lines inside a loop of wire? How exactly does induction happen in the last case compared to the first case?


texts:
Im using eagle, and was wondering how i'd produce arrows like this:

Is there a specific name for these? That show connections between many schematics.


texts:
I have noticed that a lot of CRTs have a coloured coating inside of them that would appear to have practical purpose other than maybe protecting the aquadag. Paints and plastics tend to be avoided in vacuum scenarios, so I can't imagine that the green coating is paint. Would anyone happen to know what the green layer is and why it's there?

To be clear, I know from breaking one of these open that it's a flat layer of green. In this image, the CRT PDA (The black lines) is helical, but I've also seen this green in banded PDAs.


texts: What sensor (or sensor strategy) would detect the presence of a human within a defined radius of a fixed point in a room?

texts:
I would like to reliably detect the presence of a human within a defined radius of a fixed place in a room. Think of a diamond in an art museum -- if there's a person within 5 feet of it, I could use the sensor to output a signal as a continuous 1 otherwise 0. Further, would it also work for a half-circle (such as a portrait on the wall in the museum)?
I am currently doing this with OpenCV and a webcam, but there's too much delay > 200 ms in processing. I'm hoping for a better approach that can provide latency < 20 ms.


texts: How do I connect wires to this micro stepper motor?

texts:
I want to use these motors for a small tactile display but I'm not sure how to connect to the motor connections they're so small.
I was thinking about potentially using a semi-rigid PCB. If so is this something that I can make myself or something I'd want to get manufactured. The goal is to have an array of maybe 20 of these, with each being independently controllable.
Any tips or advice would be really helpful. I'm a bit lost here.


texts: LCD SPI clock frequency with STM32L0 MCU

texts:
I'm designing a PCB that includes LCD Display NHD-C12832A1Z-FSW-FBW-3V3 (datasheet) connected to the STM32L071KZU6 microcontroller (datasheet).

I'm afraid that the SPI interface of the LCD will not work with the SPI clock from the MCU.

According to the MCU's datasheet, it says that fCLK is 16MHz in SPI master mode while the LCD (the SPI slave) has Tscyc of 50ns -> 20MHz.

Am I correct that this is a problem? How can I make them work together?

MCU:

LCD:

Thanks!


texts: Can drain and source length be smaller than minimum channel length in CMOS technology?

texts: I know the channel width can't be smaller, but what about drain and source? Say, in 0.18u technology, what would be a typical drain/source length?


texts: Fast, cheap, wireless data transmission with Raspberry Pi

texts:
I need some advice on a project.

I want to wirelessly transmit packets of data from a Raspberry Pi to several microcontrollers (Arduino or other). The frequency must be at least 15 packets/s per slave device. I am not really sure about using wifi, as it is usually not very cheap and requires setting SSIDs and passwords manually. Another thing is range. I need around 30m reach.

So far, from my research I have come to only these 2 solutions:

If its the only solution, then wifi
433/ 2.4NRF - RF modules seems to be a nice solution, but I feel there is going to be huge technical problems and limitations

To be honest, I am quite desperate. I can’t find any wireless solution for long, sustainable, reliable, fast transmision of data between master and slaves, simplex. The communication I want to establish is more of a radio transmision than transmitting commands to the slaves.

If you have any recommendation, or can point me to a particular technology that solves this problem, I will be grateful.

One packet contain array of 60 int8 plus short string. Slaves up to 10.


texts: AYTINYx4 - execute other code during analog conversion

texts:
I am using an ATTINY44 in my current project.
As I need to do some time sensitive switching I would like to avoid any unnecessary delay.
To control another device (not time sensitive) I need to read an analog value though.
I read several examples (including I checked below code from the Arduino cores (for analogRead()) and most are setting the ADSC bit and then waiting with a while loop for the conversion to finish.
I also read about the free running mode in the datasheet and noise reduction mode (conversion during idle time).

So now my questions:

Is this while loop just bad coding or are they doing it for noise reduction (because in free running mode, also other code would be executed during conversion)?
If I put the check for ADSC to be cleared in my main loop, what would be the advantaged / disadvantages?
If this method is for for noise reduction, how much added inaccuracy (maybe a ballpark figure) can I expect - I can live with +-2 or 3LSB?

Code from wiring_analog.c:

// start the conversion
sbi(ADCSRA, ADSC);

// ADSC is cleared when the conversion finishes
while (bit_is_set(ADCSRA, ADSC));


texts: Connecting six protected 18650 cells 3S2p for close to 12V, suggestions?

texts:
I want to make a 12V range battery array with 2P 3S 18650 cells.  The cells will be charged in an external charger NOT in the pack. They are removable in holders So I can pluck them out and charge externally.  I have the basic plan below.
Some criteria:
The amp draw is relatively low at around 1A.
I used the protected cells so one or more cells can't discharge below recommended volt limit. The protection also prevents a good cell from trying to charge and dump too much current into a bum cell that may be in parallel with it. That would be rare unless there is a mistake or a bad cell, it is a precaution. That is the theory.
The question is do I need BMS and if so how and where would I put it?  Would I use a regular 3S BMS and treat each two battery cluster as one cell?  Would a BMS conflict with the protection chips in the batteries?
Any suggestions? Thanks.


texts: Need help debugging my project: Fuses popping like crazy, but I can't find the reason why

texts:
I recently made a voltage and current controlled supply from a kit I found. It worked for about 15 minutes and then fuses started popping. Unfortunately, I have no idea why, because power supply worked for some time fine then and there were no changes to (just voltmeter connected all the time to output) it when fuse problems started.

At first, I thought that some part overheated and malfunctioned, but everything felt cool. Next idea was that a piece of debris inside the box might have caused a short circuit somewhere. I carefully checked the box and didn't find anything which could have caused short circuit.

Next thought was that maybe IC died. I already asked about that here, so I decided to separate circuit board and transformer and check transformer to make sure it was working correctly. So on one side I had PCB and on the other 50 VA transformer connected to a Graetz bridge rectifier. Here's the picture of the transformer part of the circuit.

I connected ends of the rectifier to my multimeter and powered on the transformer and got around 25 V, as expected. A minute or two later, fuse died again. To me this looked very strange, because the rectifier wasn't actually connected to anything.

Since I run out of required fuses, I decided to connect my multimeter in place of the fuse and see what's going on with current. At first, I connected it to 20 A range and saw that at the time I press the power switch, I get around 0.02 A. In less then a second, that falls to zero. I switched to milliamp scale and got same 20 mA. After power-cycling transformer again, the 200 mA fast multimeter fuse for milliamp scale died.

By this time I was left only with a 10 A fuse, so I decided to do some testing with it. Since the original recommended fuses were of 315 mA fast type, I decided to be extra careful. I checked insides of the box again, checked both switches, all wires and as far as I can see, everything is working correctly. I turned the transformer on with 10 A fuse and did some voltage measurements. I get around 27 V when the ends are serially connected and around 13.5 V when I'm using only one end of the transformer. When measuring DC voltage at the rectifier, I get around 25 V for both secondary coils and around 13 V for one secondary coil. I also get around 9 V AC at the rectifier for both secondary coils and around 3.5 V AC for single secondary coil. I also noticed that when power switch is in OFF position, I get around 3 V AC at the rectifier input and around 3 V DC at the rectified output. These only disappear when I pull the power plug.

After all this, I concluded that there must be something in the transformer/rectifier part of the circuit that is making fuses blow. Any ideas how to find out exactly what it is?

Also, is the behavior of the rectifier normal and should I change the switch to double pole switch which would control both power lines?

EDIT 1

I connected the PCB to the rectifier and turned it on with 10 A fuse. I'm running a small 9 V DC radio from the power source and it seems to be working correctly. Could it be that the recommended fuse current is wrong? The transformer's maximum output current is 2.1 A, so if I'm calculating correctly, maximum input current should be 230 mA. I used 315 mA fuses, so the should have survived full load on the transformer. IS there something I'm missing here?

EDIT 2

Looks like the fuses could be blowing because of inrush current of the transformer. How would I solve that problem? One of the fuses I used and which blew was a slow acting fuse, so they aren't the solution.


texts: Do EVs with a DC motor require an inverter and/or/nor a converter between the battery?

texts:
I'm somewhat familiar with Tesla's electric vehicles and that they use AC motors, but I'm completely unfamiliar with EVs that use DC motors. I know that in a Tesla an inverter is required to convert DC from the battery to AC for the motor, but since a battery always supplies DC, do batteries supply a DC motor with power directly in EVs that use a DC motor instead? Or what sits in between?

Also, if no inverter is required, which type of component is commonly used to regulate the frequency and amplitude of the DC motor in EVs?


texts:
I have been reading about the concept of  flyback transformers and converters, which has led to various misunderstandings concerning the basic operation of a transformer.
Firstly, dc current don't induce voltage in the secondary windings of any transformer. But in a flyback converter, I read that when the switch is ON, current will build up in the primary winding, and a diode that was added in the secondary winding will prevent current flowing in the secondary winding, until the switch is open or OFF.
Same with a RCC converter.When the transistor turns ON, current will be induced in the auxillary winding.How does this happen?
So can a dc or a short constant current induce voltage in another winding of a transformer?


texts:
For sensing capacitance value of sensors below circuit has common usage in literature.

I want to continue talking about simulated circuit in bottom.
Could be possible writing an equation similar to Vout/Vin=XC2/XC1 using virtual ground?(2nd pin of OPAMP)
XC1= 723ohm, XC2=723 ohm
Without R1 in the feedback path, output voltage negative rail saturated

With R1, gain is -1 and output

What is the role R1?
What is the transfer function of this circuit?

The simulated circuit


texts:
I am looking to source a four-pin, 1.0 mm pitch, vertical JST connector -- either BM04B-SRSS-TB(LF)(SN) or BM04B-SRSS-TBT(LF)(SN).  The latter has an extra 'Pick and Place' feature in Digikey.  I can't find any info on JST's datasheet for the parts, nor can I find any info on the interwebs.  There's a US$0.18 cost difference (the extra feature costing more, not surprisingly) between the parts.

What is this feature specifically?  Can the connectors without this feature still be used in pick and place manufacturing?


texts:
I built a simple RF communication system with a 433MHz transmitter and a receiver. The transmitter needs to transmit in a 180º range (I mean in one half of a sphere, I don't know how to say that in English), the receiver must be omnidiectional.

I was told that a good antenna for small 433MHz modules is a one quarter wave lenght wire, and also that the shape is important, but I didn't found on google what are the best shapes.

What are the possible shapes for auch an antenna? What are the pros and cons of each of them?


texts: STM32f7 ADC DMA transfer not populating the buffer

texts:
I'm trying to compute the FFT of a 100 kHz signal from the STM32f746G discovery board using the HAL and CMSIS DSP libraries and I've run into a few issues.

My first issue was trying to trigger the ADC conversion using a Timer2 Trigger Update but it seems there's an issue with Timer2 TRGO based on section 2.2.1 of the errata sheet here. I finally got it to work using Timer 1 with the following settings.

static void MX_ADC1_Init(void)
{

  ADC_ChannelConfTypeDef sConfig;
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV8;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;
  hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T1_TRGO;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = ENABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
    */
  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_15CYCLES;   // 1 Msps Sampling rate.
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

And my Timer setup looks like this:

static void MX_TIM1_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 0;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = ((SystemCoreClock/2) / 100000) - 1;  // APB1 Timer clock is HCLK/2 for 100 Khz signal.
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
  if (HAL_TIM_Base_Init(&htim1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_UPDATE;
  sMasterConfig.MasterOutputTrigger2 = TIM_TRGO2_UPDATE;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

My issue is when I start DMA and try to populate a buffer, only part of the array is populated and this seems to happen at random. I've come across something similar here
but the suggestion of setting hdma_adc1.Init.MemDataAlignment = DMA_MDATAALIGN_WORD and initialising the buffer to uint32_t doesn't seem to work for me. A sample output of my buffer looks like this:

My main function looks like this:

uint32_t ADC1ConvertedValue_s[2048];
 uint32_t ConvertedValue_s[2048];
 int endConv;
 \\initialise Timers and ADCs
 HAL_TIM_Base_Start(&htim1);
 HAL_ADC_Start_DMA(&hadc1, ADC1ConvertedValue_s, 2048);
 while (1)
  {
         if(endConv == 1)
         {
             HAL_TIM_Base_Stop(&htim1);
             HAL_ADC_Stop_DMA(&hadc1);

         }
  }

And I copy the values in the HAL_ADC_ConvCpltCallback

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
 UNUSED(hadc);
    endConv = 1;

     for(i= 0; i< 2048; i++)
    {

        ConvertedValue_s[index_fill_adc_buffer] =
        ADC1ConvertedValue_s[index_fill_adc_buffer];

    }

 }

Where am I going wrong here? I think the timer Period and Prescaler values are fine so I'm not sure that's the issue. I also think the ADC sampling rate of 1 Msps is correct and more than adequate. I've been tearing my head out trying to figure this out and some help would be appreciated.


texts: What does "off-state output terminal voltage" in optocouplers mean?

texts:
I was looking at possible options of what optocouplers to use in my project. I was looking at these parts.

https://www.fairchildsemi.com/search/?searchText=MOC3023-M#N=&&Nao=0&&Ntk=All&&Ntt=MOC3023-M&&Ntx=mode+matchallpartial&&Nty=1&&showAll=true&&showHrd=false

I am looking for a zero-crossing optocoupler.

As I look into their data sheet, I came into the term "off-state output terminal voltage" I tried googling the term but it just redirects me to data sheets of other components. It just so happens that also this "off-state output terminal voltage" is the only major difference in the datasheets of the optocouplers that I see.

Can I get the MOC3163M that is rated off-state output terminal voltage = 600v even though my application is using 220 V?


texts:
I'm trying to translate a 3.3v PWM signal through an optocoupler to the 12V side of a circuit, filter it to obtain a relatively clear DC voltage, and scale that to 0-10V for a control element.

So far, my circuit looks like this:

The square wave gen is emulating the PWM signal, the resistive divider should scale the voltage from 12V to 10V and the RC filter should re-create the variable DC voltage from the PWM signal.

What I'm experiencing though, is that at 50% duty cycle, the filtered output is not 5 volts as expected, but slightly lower, at 4.69V.

What is the source of this inaccuracy?
What do i need to take into consideration to make a reliable linear output?

Please advise!

Thanks in advance,
-S


texts: Where to find a discrete transmission gate

texts:
I have a project where I need to switch analog signals. Ideally, I would like to just use a few transmission gates to do this, but I cannot find anyone who sells or produces them! I've checked Digi-Key, Allied Elec, and Mouser, but nothing.

Can someone answer the following:

Why is a standard component so hard to find?  Am I using the wrong words?
If I am using the wrong words, what are the right ones?
Can someone recommend a specific part or family of parts for me to check out? (Looking for individual gates in SOT-23 or maybe 4 - 8 in TSSOP or QFN.)

Sorry if this violates the "no shopping or buying recommendations" rule, but I'm not looking for a recommendation, I'm looking for verification of existence!


texts: Matrix has a voltage drop on a coil that should not be receiving any current

texts:
I am making a matrix of electromagnets (each with about 120 Ohms resistance) and I am using a circuit like this for the columns (low side of the switch):

simulate this circuit – Schematic created using CircuitLab

For the high side (rows of the matrix) here is what I am using:

simulate this circuit

:

I have a test 2x2 matrix hooked up right now (with two rows and two columns as shown) When I power 0,0 (i.e. signals on col 0 and row 0 are high, the others low) I still get about a +4V drop on the coil at (0,1), which is definitely not what I expected. Does anyone know why? My guess is because of the lack of diodes but since the 4V is in the + direction I'm not too sure. Another guess is that my resistor values are wrong, but to be honest I'm not sure at all how to figure that out.

EDIT: After further probing, the coil at (0,1) also turns on and has a voltage reading of about 3.8V, as well as the coil at (1,1) with a voltage drop of 3.8V


texts: Why does this PUT oscillator max out at about 25 Hz?

texts:
I'm a beginner working through the Make: Electonics book, and I got to the circuit that uses a PUT to create an oscillator.  Here as image of the circuit:

The voltage builds at the red arrow until a threshold that turns on the PUT. Then current flows through the PUT, lights the LED, the voltage at the arrow drops, the PUT turns off, and it repeats.

I replaced the 470K with a potentiometer so I could adjust the rate of voltage buildup at the red arrow, and thus adjust the frequency of the oscillator.  Here is a picture of what happens as I turn the pot down through about 52Kohms. The frequency rises to about 25 Hz and then the wave stays at bottom and the LED stays lit, instead of flashing.

What is happening to cause this?


texts: Soldering lifted central pin of TO-252-5 package

texts:
I found a very nice voltage regulator of ST (LD39300). But the LD39300PT-R has a package with a lifted central pin (TO-252-5, DPak (4 Leads + Tab), TO-252AD).
Here is a photo:

I just want to do a routing of my PCB but I don't know how to solder the central ground pin.

With an extra cable?

Why is the central pin not manifactured like the rest?


texts: Is it possible to modify a Gerber silkscreen before production?

texts:
Basically, I'm building a electronics project, where Gerbers are supplied for me to fabricate at a PCB house. However, I want to add my own logo and a few personal touches to the silkscreen before printing.

(BTW, the license for the design allows people to modify it for personal use)

Is it possible to remove or add elements to the silkscreen without the use of expensive Gerber software (which I can't afford)? Also, I've heard that Gerber files are ASCII human readable and small edits can be done directly on a text editor. Is that really doable?


texts:
I am currently working on a GPS module tracking a drone-mounted device. I am using the ublox CAM-M8Q GPS module on a breakout board.

The internal antenna is working fine, however the signal is rather bad so I'm trying to use the external antenna. I'm using the hardware integration manual from ublox for reference for connecting the antenna. This it the external antenna with LFA I am using. As pointed out in this thread I connected the supply voltage for the LFA as such:

However with the antenna connected like this I'm not getting any signal. What did I do wrong and how can I improve this circuit?


texts: Applying KVL on PNP Voltage Divider Bias BJT

texts:
The circuit above is a PNP Voltage Divider Bias BJT. From the book, to get the emitter current, the circuit was transformed first into a Thevenin equivalent circuit then applied KVL from base to emitter:

Vth + (Ib)(Rth) - Vbe + (Ie)(Re) = 0

Where Vth = Vcc (R2 / R1 + R2) and Rth = (R1)(R2) / (R1 + R2)

Finally, Ie = (-Vth + Vbe) / [Re + (Rth / Beta)]

Questions:

1.) From the KVL done from base to emmiter, shouldn't it be -Vth as this is PNP type and the polarities are reverse. Also, why is Vbe is "-" when it should have been reversed too when in PNP? Also, the source Vcc is negative.

2.) If I want to get Vce, applying KVL from Vcc to emitter ground, is: -Vcc + IcRc + Vce = 0 right? Vcc starts from negative, so the polarity of the Rc is negative to positive which is the same for Vce.

3.) When getting Vce, looping at either from emitter ground or from source, why are we ignoring IeRe in the loop when getting Vce?

Note: The book didn't show the Thevenin equivalent for the PNP VDB, it was just stated that it is the opposite of the previewed NPN VDB.


texts: PCB design rule errors, but can't understand why

texts:
I am trying to create a PCB using NI Ultiboard. My circuit is a SECPIC DC-DC converter and controlling the L1 current. This is my circuit:

and I get this error:

Design rule error: Net "VOUT" close to net "3".
Design rule error: Net "3" close to net "VOUT".

This is the area of the error (zoom of the second picture):

I can't understand why I get this error, because in Multisim the circuit is working fine. Can anyone explain the cause for the error?


texts: Op amp analysis: when are the "negative feedback rules" applicable?

texts:
When we build op amp circuits that use negative feedback, like so:

... we can analyze the circuit very easily, by assuming that $$v^- = v^+$$ due to negative feedback (when also assuming the op amp is ideal, of course).

Besides the obvious high-precision cases where these simplified models break down, when is this and when is this not valid?
For example, if we replace the feedback resistor with some other element - perhaps a capacitor, inductor, diode (regular silicon diode, zener diode, etc.), or some combination of them and other common circuit elements - how do we know where this simplification is valid?
Also, even if we stay with a resistor as the feedback element, as the resistance becomes very, very high, at some point we can pretty much consider it an open circuit, and so clearly this model breaks down somewhere along the way.

So, the question is: under what constraints is this approximation "true enough" to give useful results?

EDIT:

For another example, consider the basic inverting log amplifier circuit:

If we solve the Shockley diode equation

$$i_D = I_S(e^{vD/VT} - 1)$$

for vD, we get $$v_D = VT \ln{\left(\frac{i_D}{I_S} \right)}$$
(ignoring the 1, which is mostly irrelevant as the exponential will be rather huge)

If we then use the virtual short method to see that $$i_D = \frac{v_{in} - 0}{R_{in}}$$  we get the correct expression for the output:

$$v_{out} = -VT \cdot \ln{\left( \frac{v_{in}}{I_S R_{in}} \right)}$$

So, the virtual short method works here. But since this diode will be an open circuit when $$v_{out} > v^-$$ I'm not sure how to figure out beforehand that the analysis will be valid.


texts: Writing a Function at specific memory location of Flash

texts:
I want a function to go at specific memory location of Flash and I am not able to figure it out.

Do I need to do modification in Linker File?

Also, I have idea that in GCC, I would use #pragma directives by which I can put my code in specific section but don't know how to assign that section to specific address.

I am using Keil and programming LPC2138.


texts: Picking a power supply for a TMC2130 stepper driver and motor

texts:
I'm trying to pick a power supply and need a little more guidance before I'm comfortable spending money on one.

This site explains how to calculate your figures for power supplies but isn't too descriptive. https://learn.watterott.com/silentstepstick/faq/

Their example:

What power supply do I need?
A power supply (Psup) with a few times higher voltage than the motor phase
voltage and a current of roughly the power of the motor (Pmot) plus the
mechanical output power (Pout) is at least needed.

For example 3 stepper motors with 2 coils/phases and every phase has
3.3 Ohm with a 1.2A current rating and a voltage of 4V.

Pmot = 2 coils * 4V * 1.2A = 9.6W (standstill power without load)
Pout = 0.20Nm * (2pi * 1000rpm / 60) = 20.9W (mechanical power)
Psup = 3 * (Pmot + Pout) = 91.5W (electrical input power)

At 24V this is a current of 3.8A (I=91.5W/24V).

I'm using a single 3.2V stepper motor with 2.0A/phase

Here's my calculations using their formulas:

Pmot = 2 coils * 3.2V * 2A = 12.8W
Pout = 1.2Nm * (2pi * 1000rpm/60) = 125.7W
Psup = 12.8W + 125.7W = 138.5W
Vsup = 24V
Isup = 5.77A

I just kinda assumed I should use a 24V supply and got the current from that and the power. I have seen other people use a 12V, but wasn't sure what would be best. At 12V I would need a supply that's 11.5A!! Right?

So assuming I go with a 24V supply, would I try to find one that's 24V and as close to 5.77A without going over? Or is it ok if I use one that's 6A. I couldn't find anything in the TMC2130 datasheet about max input current limits.

Any advice is greatly appreciated.


texts: Powering a NEMA 17 motor | Wattage Vs Voltage

texts:
I apologize if the question is silly as this is my first project involving stepper motors and I'm confused about power supply specifications.
So I'm working on a project involving:

3 NEMA 17 Stepper motors with 4.2 kg-cm torque
3 A4988 drivers

Now the motor is rated for 3.2 V 1.2 Amps/phase. So, at 3.2 V the motors require 3.6 A of current in total which means a wattage of about 11.5 W.
So can I use any power supply which can deliver sufficient wattage or should the power supply be capable of delivering 3 Amps regardless of its voltage?
Is an 18V 2A supply sufficient or do I require a 12V 4A power supply?


texts:
I am designing a LED Headlight for my car. But I am confused about my BJT, I dont know if it is suitable or not. The overall design is given below.

The problem is, when I run the ckt under engine off (power source is the battery, 11.86v) then there is no problem, even all the components are ice cool. But when I start the engine (power source becomes the dynamo, 13.5v) then in 2 seconds I start to see smoke from the BJT and just under 5 seconds it is blown. I see a small hole up on the emitter pin. Can anybody tell me what could be the reason?

Besides, if you want datasheet, all the model numbers are given in the diagram.
If you want to know, I couldn't find any data sheet for my LEDs so I measured the amps on my own, I am giving you a link of those LEDs.

http://www.ebay.com/itm/10Pcs-DC-9-12V-10W-Cool-White-High-Power-800-900LM-SMD-LED-Lamp-Flood-Light-Chip-/390876125031


texts: Mounting a heavy PCB in standing position

texts:
Due to space restriction I want to mount the PCB vertically and secure it with M3 screws to the box bottom like this:

simulate this circuit – Schematic created using CircuitLab

It's a power source board with a lot of big capacitors and is heavy, I'm not sure about doing it. are the capacitors going to fall off after a while? is it OK to mount a heavy PCB vertically?


texts: What is proper polyphase AC terminology?

texts:
I'm not entirely clear on the proper terminology for polyphase AC systems. I hear it used informally, but I'm not sure what the proper formal names are, if there are any. How I've got it in my head is this:

A leg is a current-carrying conductor
A phase is the voltage difference between two of these conductors

Is this accurate? Also, is there standard nomenclature for the names of the legs vs. the names of the phases? (A B C, 1 2 3, AB BC CA, that sort of thing.)


texts: What does "1 second short circuit protection" mean?

texts:
In the datasheet of R1SE DC-DC family I read:

Short Circuit Protection (SCP)    below 100 mΩ    1 second

What does it mean?
After 1 second of short-circuit the device will burn? What kind of "protection" is this?


texts: Current draw calculations for a brush-less motor are way off

texts:
I've been attempting to calculate how much current a BLDC will draw given a known propeller size, thrust, internal resistance, Kv rating, Supply Voltage(Vin) and idle current. My propeller parameters are as follows;

Diameter=34;                               %Propeller diameter(In)
Pitch=11;                                  %Propeller pitch(In)
Pitch_m=Pitch*0.0254;                      %Propeller pitch(M)
Radius_m=0.0254*(Diameter/2);              %radius in meters
Area=pi*(Radius_m^2);                      %Disc Area

The information I have about the motors is it's idle current, internal winding resistance and its Kv rating.

%Motor Characteristics (Defined)
Io=1.30;                                       %No load current(I)
Rm=0.21;                                      %Internal Resistance(R)
Kv=100;                                        %Revolutions per Volt

I'm calculating the fluid speed using some basic thrust equations I grabbed off of a forum.

%Thrust equations
rho=1.225;
Pconst=1.15;
Thrust=130.9;                           %Reference thrust from experimental results
V=sqrt(Thrust/0.5/rho/Area);            %speed of fluid moved by propeller
P_aero=Thrust*V;                        %aerodynamic power
Pmec=P_aero*Pconst;                     %mechanical power
RPM=V/(Pitch_m/60);                     %revolutions per second

Finally, I am calculating the motor's current as follows (not everything below is used)

%Motor Equations
Ke=1/Kv;
Kt=Ke;                                  %Torque constant equals back emf constant
Vin=40;                    %Input Voltage(V)
a=-Rm/Pmec
b=(Vin+(Rm*Io))/Pmec
c=-1*((Vin*Io)/Pmec)
p= [a b c];
Iin= roots(p);
Vloss=Iin*Rm;

To explain the a, b , c and p I came to that by expanding out the following and finding the roots.

Pmec = (Vin - Rm * Iin) * (Iin - Io)

When I run this in MATLAB, the values I get are;

Mechanical power:     2874.5 Watts
Aeronautiical power:  25003 Watts
Vin:                  41V
Iin:                  174A

I get 174A for Iin, which is a colossal current value. On the manufacturer's website, the current draw for this motor when it's producing 13392 grams of thrust is 52 amps at 2092 Watts of power given a 40 Volt Supply.

Motor is a Tmotor U12KV100.
The equations are from the forum linked below

https://www.rcgroups.com/forums/showthread.php?587549-Motor-formulas

edit: There was an order of magnitude error in the script. I have since corrected the error however the current consumption is still unrealistic and well off the experimental data provided by the manufacturer.

edit2: clarified some confusion on Vin. I was calculating how much voltage required even though I knew the supply voltage 40.


texts: How can I use an LED driver (QX5252) to light up 3 different color LEDs (Green, Yellow, Purple)?

texts:
I am trying to light up 6 LEDs with the common garden light circuit (2v Solar panel and 1.2V battery). The problem is that I want to light up 2 yellow LEDs, 2 green LEDs, and 2 purple LEDs simultaneously. When I connect them to the QX5252 without any resistors only the yellow ones turn on. I added resistors to balance the current and it kind of worked. All the LEDs turn on but they turn off after like 1 minute. Then I disconnect and connect the battery and they turn on for another minute. Could you please let me know how I can make this project happen?

Here is the Schematic:


texts: Discharging 18650 at higher Peak-Amperage than rated max continuous Amperage?

texts:
I am using Sanyo NCR18650BL cells. They are rated for 7A max continuous discharge, but i could not find any info on temporarily discharging them at a higher rate (for example 10A per cell). Is it acceptable to discharge a cell (during a very short period of time for example 1 minute) at a higher peak amperage than the rated continuous max amperage? (provided the battery pack temperature is being monitored via the bms and as soon as temperature gets over for example 70 celcius the bms cuts the power or more likely limits the power to  for example 7A per cell).
Or is it a bad idea and a no-go to discharge any cell (even temporarily) above rated continuous max amperage?
cell info: http://www.nkon.nl/sk/k/NCR18650BL-specification.pdf
Could you give me an indication of how bad the effect on cell life/capacity would be caused by this temporary higher discharge rate?
My bms can handle 200A but is adjustable (via bluetooth), can adjust max amperage adjusting to current temperature.
Thank you very much!


texts: Does two different regulators act as different power supplies for MCU and Relays

texts:
I'm driving 4 coil relays with an MCU through BJTs. As I activate one by one, sometimes the third won't even turn on, and if it does, it nor anyone will turn off, as if the MCU freezed. I'm totally sure this is because of noise since Relays are 5V, the MCU is 5V and of course, the power supply is only one, and to worsen the case, it's an SMPS taken from a cellphone charger. I've improved the board by adding a 470uF decoupling capacitor very close to the MCU (ATMEGA328P), and it did indeed enhance the functionality of the MCU. Without the capacitor, it would barely turn on just one relay. Since the relays are 4, it's undoubtably the coil inductance giving the power rails a LOT of turbulence. As I've read around the Internet, the only way out of this is to use two different power supplies (and optionally an optotransistor for better isolation). One for the MCU and logical parts, and other for the relays. If you could give me a simpler solution, it'd be great, but otherwise I'd like to know if using a 12V transformer and two 7805 for each appliance is enough, or do I have to make two rectification stages or even to use two different transformers.

P.S. I've also googled on the use of Solid State Relays, but they don't seem to be very cost-efficient for this, and I don't even know if I'm going to find them available here in my country.

EDIT

The schematic is this. The 470uF cap and 10k pullup resistor in RESET pin are not present here, but I added them to the board.


texts: Capacitor Vrms vs Vpeak Rating in Transformerless Supply

texts:
Why is it that when calculating for voltage across the capacitor in transformerless power supply we need to use peak voltage not RMS voltage value.

To be clear I am referring to the rating of C1 in this circuit diagram.


texts:
Based on this post, let me assume that I have a input source of 94 dB SPL / 1 Pa that a microphone is picking sounds from.

The microphone has a sensitivity of -46dBV/Pa , this gives 0.005012 V RMS/ Pa.

Let us assume the ADC has unity preamp gain and no additional gain. Let us also assume an ideal case where there is no degradation in signal due to noise  before ADC.

Now, I'm guessing the signal measured at ADC would be the same as input, which is 0.005012 Vrms.

20×log 0.005012/005012 = 0 dB

so the dB SPL will be (-46) + 0 = -46 + 94 = 48 dB SPL.

Why is the output not 94 dB SPL which is what I thought the output should be because we are inputting a 1 Pa sound?


texts: Why SATA is simplex even though it has separate TX and RX pairs?

texts:
Why is SATA simplex even though it has separate TX+/- and RX+/- pairs? Why can't it be full-duplex like SAS (which has the same interface with multiple ports and is full-duplex).
If I am wrong with this concept please correct me.


texts: Why does the voltage across the diode drop with parallel resistor value in this circuit?

texts:
I was a little confused with the voltage divider circuit with a diode in parallel to the upper resistor, so I simulated the circuit where the resistance R1 is varied from zero to 10k:

(Green plot is the voltage across the diode and R1 with respect to zero to 10k resistance.)

Normally in this scenario, the diode drop is always expected to be around 0.7V.

At first I thought the voltage across the diode will always dictate the voltage across R1. But as you see below a certain resistor value it is not the case and the voltage across the resistor and the diode starts dropping drastically. How can this be explained mathematically or from a circuit theory point of view?


texts: "Ignoring" a dangerous AC level, while performing ADC conversion on DC level

texts:
I need to monitor a plasma cutter's DC voltage. I selected the AD629 from Analog Devices and have a schematic and layout that works on a test bench.

Admittedly, my talents are in software and what I know about EE just makes me dangerous. :)

My concern is that welders and plasma cutters emit a high-frequency AC signal in order to start the arc. Not knowing any better, it seems to me that signal would fry my board. Although I've seen torch-height controllers and similar and see no obvious technique for "shielding" the PCB from this.

I am assuming that a 5K volt AC signal would happily create arcs anywhere the POS and NEG lines are very close -- such as on a PCB.

How is this working?


texts: I have a conceptual question: What means "high" code density? and why is it so important?


texts:
I know how to create a full adder using a 4:1 mux with A and B as the select lines. However, now I need to create a full adder using B and Cin as the select lines.

the CoutMux and SumMux columns represent what the input lines would be for those 4:1 Multiplexers. I'm not sure how to get the values for the other inputs because the value of Cout and Sum is constantly changing while the value of A is the same.

Here is the original question if I didn't explain correctly:

Using two 4-to-1 MUXes, connect Cin and B to the control lines of the MUXES, and connect 1, 0, A, or A' to each input.


texts: Open-circuit Output Voltage of Bipolar Output Stage

texts:
In TI's doc Designing With Logic, p. 16, it shows a method to calculate the internal resistance (\$R_{o}\$): using the open-circuit output voltage (\$V_{o}\$) and short-circuit current (\$I_{os}\$).

$$
R_{o} = \frac{V_{o}}{I_{os}}
$$

I can understand the method to get \$R_{o}\$, but i can't understand how get the 'open-circuit output voltage', if it's output floating, ideally there will no current flow in Q1 and Q2, where the voltage come from?


texts:
is it possible to make a logic OR gate with 2 diodes in series like this:

simulate this circuit – Schematic created using CircuitLab

For my project this would be easier to wire than the usual parallel configuration.


texts: Does the contact pad need to match the footprint shape of the SMD

texts:
If the contact pad is larger than the footprint, or has a different shape but is still large  enough to make full contact with the SMD, will this lead to problems during reflow soldering?

I am designing a metal core PCB on which I will be mounting LM561c samsung diodes. I am striving for a high thermal dissipation factor, to preserve the effeciency of the diodes.


texts:
I've been looking at impedance matching a circuit, but I'm struggling to find an equation for calculating the values of the resistors in the output network.

Given this circuit:

How are the values 475R and 56.2R calculated?


texts: How to change the default white background in 3D mode inside Altium?

texts: In the pcb 3d view I want to change the background color from the default white to something more dark, how can I achieve this?


texts: Best way to examine the values of a pin?

texts: New to Pic and microcontrollers in general. I have a PIC16f1779 chip and I want to read the values of an ADC pin (RD1) that is hooked up to a potentiometer. I was wondering how I can see the values of pin RD1. Is there any similar thing to Arduino's simple read() function?  From my research there's not, without setting up a serial connection. So what's the best way to look at RD1? Do I need to interpret the values from the memory view of MPLab, and if so how would I do that?Thanks in advance


texts:
I have an LDR and it reads higher than 17K ohm when the lighting conditions meet my requirements.
I wish to be able to activate a vibrator motor (coin type 3 Volts) when the LDR has a resistance higher than 17K Ohm.
I have no idea though how to do so.
Any ideas more than welcome!


texts:
I have an assignment in college and I would like to ask some questions:

You are to design a Mealy state diagram for a safety device. Assume that two debounced push-buttons, A and B, are available to enter the combination. An electromechanical interlock guarantees that the buttons cannot be activated simultaneously. The lock should have the following features:
The combination is A-A-B-A-B-A. If this sequence is correctly entered, an output signal is asserted that causes the lock to open.
For any state, three B pulses in a row should guarantee to reset the control to its initial state.
When any out-of-sequence use of the A push-button occurs, an output is asserted that rings a bell to warn that the lock is being tampered with.
Once the lock is open, pressing either A or B will cause the lock to close without signaling an error. Draw a Mealy state diagram for this finite state machine. Indicate what each state represents and what input conditions cause state and output changes. Not everything may have been specified, so write down any assumptions you make.

I have to implement this Mealy machine using D flip-flops and MUX'es.
I have 10 states for my machine:
S0 -> "Input Start" // Nothing happened
S1 -> A
S2 -> AA
S3 -> AAB
S4 -> AABA
S5 -> AABAB
S6 -> AABABA -> this means EXIT
S7 -> B
S8 -> BB
S9 -> A -> "ALARM ON"

*****EDIT to add machine pic

My questions are:

From what should I start in creating the truth table (on this specific assignment -- How can I think the necesarry flip-flops and MUX'es)?
How can I create this specific diagram? Using only MUX'es and D-Flipflops?


texts: How to provide gap between two separate structure or microstrip lines in ADS(Advanced design systems)?

texts: I want to provide gap between two resonators. Here is an image. How do I provide those gap M12 and M23.


texts:
I want to connect a 3.3V TFP401 to a 2.5V spartan 6 LX45T FPGA. It looks like each device is tolerant to the other device's voltage:

TFP401:

DVDD                                      Min: 3.0V   Nom: 3.3V  Max: 3.6V
Input voltage range, logic/analog signals Min: –0.3V  Max: 4V
High-level digital input voltage(1)       Min: 2V     Max: DVDD
Low-level digital input voltage(1)        Min: 0V     Max: 0.8V

Xilinx Device:

This means that both are going to be transmitting at their respective voltages and are tolerant to receiving at the opposite voltage. I can't see anything wrong with this?

I'm just not sure about one thing:
Do I have to be concerned about current drive strengths? If a device drive current is spec'ed to drive a voltage to 2.5V within a specified time, and the receiving device expects a 3.3V input with different high/low thresholds, then the input slew rate could possibly be out of spec since the signal takes longer to be detected as "high" on the receiving end?

I don't think this is a big issue because I can specify in my timing that the signal is a LVCMOS33 signal on a 2.5V line and the FPGA can compensate accordingly. Also I can change the drive strength on the FPGA as needed. I just want to be sure that this is really the case.

Clarification: At the moment my intention is to use LVCMOS33 for inputs and LVCMOS25 for outputs. I've never seen this done before. Good idea, bad idea?

Edit 1: Implications of using LVCMOS25 for in and out:

Case 1: FPGA out, TFP401 in.

FPGA out 2.5V.
    FPGA   Output Low   is 0.4V max
    FPGA   Output High  is 2.1V min

TFP401 in 3.3V.
    TFP401 Input  low   is 0.8V max <-- Fine.       FPGA out low  is below TFP by 0.4V.
    TFP401 input  high  is 2.0V min <-- Borderline. FPGA out high is above TFP by 0.1V.

Case 2: TFP401 out, FPGA in.

TFP401 out 3.3V.
    TFP401 Output low   is 0.8V max
    TFP401 Output high  is 2.4V min

FPGA in is 2.5V.
    FPGA   Input  low   is 0.7V max <-- Problem. TFP out low  is above FPGA by 0.1V.
    FPGA   Input  high  is 1.7V max <-- Fine.    TFP out high is above FPGA by 0.7V.

FPGA numbers taken from here, page 10.

TFP401 numbers taken from datasheet linked in first line.


texts:
I'm getting really confused about a specific BJT circuit. I want to control LCD brightness and contrast as suggested here.

Apprently a capacitor is used to filter PWM output to the contrast pin, and an emitter-follower BJT topology is used to control brightness. However there are some aspects of this particular implementation that I've yet to understand:

Why isn't a simple capacitor is used in the brightness pin, similarly to the contrast pin?
In the emitter-follower, is the BJT operating in linear or saturation zones?
Why does the author discard the base emitter voltage (0.6V) in his calculations?


texts:
I built an IoT device that sleeps and wake with Texas TPL5111. (Timed wake system with external wakeup option). Also i have external sensors and want to awake system with sensor interrupts. 2 wan on this section.

Using I2C multiplexer like PCF8574 (have an int output). Sensor interrupt pins connected to PCF8574 I/O pins. And PCF8574 INT output is used to control TPL5111 shut pin.
Using a logic design to combine interrupt pins.

OR Gate = SN74HCS32 (combining sensor interrupts)
AND Gate = SN74HCS08 (for enable or disable sensor interrupt)
NAND Gate = SN74HCS00 (for inverting active low inputs)

Which solution is effective in low power consumption IoT device.

Thanks for answers.


texts:
What is the difference between having a voltage divider vs just using a resistor in series.

So for example, I have an input voltage with 12V, and two resistors in a voltage divider, R1=10k, and R2=10k, so my voltage is evenly split to 6V. How is this different from having one resistor (R=6k, I=1mA) in series?


texts: Explanation of a sample circuit for the FL5160 Dimmer controller

texts:
While looking for dimmer circuits, I stumbled upon the FL5160 Dimmer controller and it's specification at https://www.onsemi.com/pub/Collateral/FL5150-D.pdf The example schematic (for example, the three wire circuit on page 3) connects DC ground to the common terminals of two MOSFETs in series. It appears that when Q1 and Q2 conduct, there's no isolation between the AC mains and the DC part of the circuit.

Looking around, I see this is pretty common, for example, https://sound-au.com/project157.htm also has a 3 wire dimmer circuit that has the ground connected similarly.

Am I understanding this correctly ? Or something like a optocoupler is preferable here assuming dim would be controlled by a human operator ?


texts: Can a malfunctioning relay in an amp cause or allow a speaker to crackle when turning the vol potentiometer?

texts:
Ok, so this question has several layers, I admit it.

I recently acquired a Lepai 2020A+ amp. It is, I believe, the latest version PCB because it has the two relays for speaker protection instead of just the one.

I'm new to electronics, so please excuse my total lack of knowledge.

What I understand is that the function of these relays is to delay the power output to the speakers when the device is turned on; to avoid any pop that may damage the former. It may also work when turning off the device, to avoid a thump... but of this I'm not sure. It's a cheap amp with cheap components.

Anyway, I received it and I noticed the left channel had a slight crackle when I turned the vol pot. It started right when I brought it out of 0 percent. But then it started crackling at around 20, then 50. I assumed it was rust or just the protective film flaking off of the cheap pot. So I sprayed it with some contact cleaner. After much caring for it, I've been able to reduce the crackling back to the original crackling I heard when I first turned the pot. If the amp has been off several hours, then it will slightly crackle when turning the pot up from 0. If I turn the pot a couple of times before turning on the device, then there's no audible issue.

All the time, this is only happening on the left channel. The right one is 100 percent clean. Other than this, the amp works as expected.

However, the other day the amp was off and I turned the pot and heard a slight crackle. I did notice, when I first received the amp through the mail, that if turned off and disconnected, the circuit still retains some power: first thing I did; right out of the box, I switched it on without connecting it and that intensely unnerving blue light the Lepai has around the vol control came on and fade off for a couple of seconds.

So I'm still trying to make sense of this issue. Trying to know if it's a faulty, old pot that's seeing its last days on the left channel and, therefore, I should just invest in a better pot and change it (because the rest of the amp modestly rocks) or if it's more complicated than that... perhaps an issue with the left channel relay, etc., and I'd better change the device entirely.

I probably am shooting way off the mark here but the first thing I thought when I heard that crackle when the amp was off was that perhaps the speaker-protection relay for the left channel is not working. But does a relay like this only work during on and off? Or does it still work throughout the process? And, if so, does it have the ability to "filter" these noises?

I'm thinking that even if some "filter" component (not necessarily the relay; if any of you knows the Lepai maybe you know if it has any filter incorporated) is not working like it should, that horrible noise must be coming from the vol pot. Am I wrong to think that? And to think that if the right channel is completely clean, then it must be an issue with the side of the pot that outputs to the left channel?

And finally, could this noise be digital and coming from deeper in the circuitry or does it necessarily have to be analog and coming from the pot?

I know this is a layered question but I've been looking for individual answers all over the net and can't find any, so I'm hoping somebody out there can help me out by guiding me into electronics though this, my first mod project.

Thanks a lot in advance!


texts:
I'm novice to vhdl coding. I'm implementing BZFAD which is a low power multiplier.

In the Block diagram as shown below I have a transistor block(M1) whose input are driven from the ring counter. I'm confused as to how these transistor can be implemented using VHDL.

I'm using Xlinx ISE tool to implement the same.


texts: Unusual harmonic data reading from phototransistor in a simple arduino setup

texts:
I have a very simple circuit for detecting ambient light readings with an arduino, but I'm noticing a sinusoidal pattern to the readings I'm getting that are hard to pin down the source of. How do I eliminate the noise so I get a more or less constant reading?

My circuit is:

simulate this circuit – Schematic created using CircuitLab

My code is simply:

int analogPin = 0;

int val = 0;

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  val = analogRead(analogPin);
  Serial.println(val);
  delay(33);
}

I graphed the results and it looks like this, oscilating between the values of 175 and 110, on a scale that goes from 0 to 1000 normally:

The period is about 8.5 seconds between crests, with downward blips about once every 1.4 seconds. Nothing in the light around me would explain this obviously... what's going on? How do I get more consistent values?

Solution

I took random samples over the course of the sample period and that seemed to help out a lot.

int analogPin = 0;     // potentiometer wiper (middle terminal) connected to
analog pin 3
                       // outside leads to ground and +5V
int val = 0;           // variable to store the value read
int maxwait = 200;
int varwait = 2000;

void setup()
{
  Serial.begin(9600);              //  setup serial
}

void loop()
{
  long sum = 0;
  int count = 0;
  int endTime = millis() + maxwait;
  while(millis() < endTime){
    sum += analogRead(analogPin);
    count++;
    delayMicroseconds(rand() % varwait);
  }
  Serial.println(sum / count);
}


texts:
I have replaced several light fixtures with LED in my company. The 400 watt hi-bays I replaced with 95 watt LED. They work great.
I replaced a set of office lights that were track halogen with 7 watt LED pot lights. They work great..... until.

The problem. We have a large turret punch press and the ram operates with a large servo motor. With every single stroke of the press the lights flicker. So if the press stroke is 100 hits per minute or only 50 hits per minute the lights will flicker accordingly. These are the only lights affected.

Is it possible to add in capacitors or a 1:1 transformer? My electrician has no answers. Power into the building is 600v and the press has its own transformer 600-480. The light circuit is 120v.

The LED lamps are GU10.
Brand is LUXWAYBGU07LEX 480LM, 120V, 60HZ, 7W, 40D, 45mA 3000K, CR190, 24314, DIMMABLE.

Thank you in advance for any solutions or ideas


texts: Circuit Design - Need 35mA through UV LED using a GPIO controlled switch

texts:
I was trying to achieve this using a PNP transistor as a switch circuit and the voltage drop was too significant and I was only able to achieve 13mA. Circuit here

I was advised to use a FET instead. Would this be as simple as swapping the PNP for any FET? How would I design a circuit to reach 35mA through my UV LED (while being controlled by a GPIO pin)?

UV LED - 340nm: UF4VL-1H321


texts: Part difference - regulator 50kHz flutter

texts:
Here's an odd one.
A device that used before LDO LDF33DT-TR 3V3 regulator was fine - (total draw is around 180ma.)
Componant shortage meant we changed to LF33CDT - now we have a 50kHz 1V flutter on the 3V3 rail - looking at the datasheet the only difference is 500mA as opposed to 1A supply limit - any ideas?
LDF33 (working)
LF33CDT (flutter)


texts: TDMA in telephone circuit switching - isn't there delay in transmitting a particular user's speech?

texts:
Let's do a simple case on the left with X and A user telephones.

So the way an analog signal (user's speech X) is handled, is that it is sampled at 8000 bits / sec.

The high-speed C-channel has 128 kilo bits/sec of capacity.

X only transmits at 64kbps

A transmits at 64 kbps too.

However, if the switch 1 only "listens" to X for some time constant, and then switches to A, wouldn't it make the speech of X seem slury/ with pauses? Let's imagine user X is talking continuously for 5 minutes, if switch 1 is switching between X and A, then there will be short pauses in what user X is saying, isn't it?

So why is circuit switching even considered as a viable option in telephone communication? It's not.


texts: Enable switch (transistor) at certain voltage with comparator

texts:
So right now I have a boost converter with a capacitor at the output as energy storage. My idea was to use a comparator (DC) comparing capacitor Voltage vs. reference, and the output was connected to the transistor (switch), so the load would be charged with the energy, but it doesn't seem to work as intended. Any suggestions?

Forgot to add: imgur.com/a/FbHe7 I want R2 to enable a switch so there is a connection to R1, when a certain voltage on the capacitor is reached


texts:
I need help determining what are some helpful bits of information to include in a new schematic number scheme. For example:

Schematic ID

Revision (Major, Minor, Fix)

etc.

Its not critical, but I would like to define some good info to include in the numbering system before I commit to it for this new project.

Thanks


texts: FTDI USB/TTL-serial converter - what are TXD, TXL, RXD and RXL?

texts:
I've got a couple of TTL USB/serial converters.  I think they're FTDI chips.

As well as pins marked TX and RX, there are unpopulated holes marked TXD, TXL, RXD and RXL.

I've previously thought that TXD and RXD were aliases for TX and RX.  Is this true?

What could TXL and RXL be?


texts:
Can anyone explain what the voltage divider rule is? How has the author of this book used it for analyzing the Voltage Divider Bias circuit for transistors?

And can anyone explain how the two resistors are parallel? And how has the author assumed the battery to be a short circuit (as shown in Figure 4.28)?

Thanks a lot.

________________________________---

From above link:


texts: Simplifying circuit for Thevenin's theorem

texts:
I am supposed to find a Thevenin's equivalent circuit for this one:

I am struggling with simplifying it to calculate Rth. When I apply short circuit to voltage source I achieve a junction connected to R1, R3, R7+R6 and R4. How to handle it?


texts: How does soldering affect the internal bonding between the IC die and its package?

texts: In other words, How does the IC fabricator solder these thin wires between the die and the pads and guarantee that the soldering iron temp (300C for example) on the IC pads won't desolder them?


texts:
Hello I am a software engineer and I dont have much experience of analog electronics.

I am doing a project of weight measurement using HX711 weighing sensor .
below shown is a rough schematic of my circuit .

 I am trying to measure various weights . As i increase the load cell capacity the fulctuations seems to increase as well .
For load cells of 1 ton and more the fluctions increase tremendously . I have interfaced Hx711 with raspberry pi using this library Tatobari-hx711.
i tried averaging that is given in this library ,that too doesnt seem to work.
I also read that the Excitation vtg to load cell thru HX711 is noisy so i am powering the loadcell from SMPS itself .

Questions

1) Is there a simple way to reduce fluctions ? What can I try ?
2)what can be done in software to reduce noise ?

3)if the output of load cells is same (0-20mv) why does this issue arise ? is it due to multiplication factor ? lower range load cells work fine ..is it due to stable first bits of ADC output ?

4)I read somewhere that fluctions can be reduced using some hardware peripherals like resistors .
how to do it ?


texts: Three phase motor driver DC link, DC bus capacitor values

texts:
I am designing a motor driver for a three phase brushless motor and have been looking for a capacitor value for the DC bus of this circuit (C1). Most of what I have found when researching deals with smoothing capacitors during rectification of an AC to DC circuit.

What I am looking for is to calculate the capacitor size 1 - to allow the power supply or battery to catch up due to the high current draw. 2 - to suppress the high voltage coming back into the circuit due to induction. From what I know so far is appears that the capacitor size isn't super critical to meet requirement 1, something between 100~1000 uF. Also the inductance values for L1, L2, and L3 is not representative of the actual motor.

This circuit drives a 24 V motor with a peak current of 30 A, lets say with a 20 kHz PWM signal.


texts:
I am trying to use a QSFP-DD port on an FPGA to breakout and interface with 4 or 8 SFP+ ports. I am curious if this is possible. From my research online, it seems like this all depends on the module you're using (QSFP+ for 10G, QSFP28 for 25G).
I researched online and there seem to be QSFP-DD to 8 SFP cables. The issue is that the SFP side doesn't specify if its SFP+ or SFP28. It seems like SFP+ and SFP28 support two different rates (10 and 25 respectively). I've tried emailing the vendor, but they just say the cable can support both speeds which seems to contradict everything I read online. The FPGA spec says it can handle 8x 10/25, but my issue seems to be knowing how/if it can breakout to the 8 links? Has anyone ever dealt with this issue or know how I may get my solution to work?
Any insight would be appreciated.
Thanks in advance!


texts: What is the charger voltage graph while charging Lithium battery with CC/CV approach?

texts:
What is the voltage graph from the point of view of the charger while performing a CC/CV charging?

Isn't a "Dedicated Lithium Ion CC/CV charger" simply "a Constant Voltage DC Source with Current Limit" (like we use in labs)?

Looking closely to the CC/CV transition of the graph, there is a sharp turn in the battery current¹. If the internal resistance of the battery is not changing that sharp - which I think it's not the case -, this is a good indication of a sharp voltage change on the output of charger. It might be quite possible that the charger exceeds the CV value right before the CC/CV transition point to keep the current constant, and then, lower the output to preserve the required CV level.

Is there any point in the charging process that the output of the power source exceeds the CV limit in CC stage?

Edit (Conclusion)

Regarding the answers, IMHO, the "CC/CV" declaration for the battery charging process is quite misleading by definition.

"Constant Current" term leaves the terminal voltages undefined by definition. However, according to the answers, it is defined and can not be greater than CV limit at any point during the charging process.

IMO, it would be clearer if it was defined as "CV+CL (current limit)" for the charging stage.

¹: It was because of the two capacitors in the equivalent circuit model.


texts: The Output of High/Low Pass filters and the DB changes that occur

texts:
I recently just learned what a dB is (decibel) and am trying to figure out why in high/low pass filters these drops occur. Also how they're affected.

Say I have a high pass filter with a cutoff frequency of 60HZ. If my input voltage of 5V pk is at a frequency of 60HZ it seems my output voltage will see a 3 dB drop down to 3.535 V. How can I calculate the expected dB drop given my cutoff frequency in this case? For example say I wanted to know what frequency I need my 5V signal to come out at 2.5V (6 dB drop).

This is probably super nooby but I'd appreciate any insight on this topic you guys have to share.

EDIT: Another side thought but on-topic: I'm talking about an RC circuit above however this can also be done with an LR circuit correct? When is it advantageous to use one over the other?


texts: VI component tester not working properly when capacitor is placed parallel with diode

texts:
I am trying to repair mainboards with VI component tester. (Such as this device and that device.)

I check the characteristic VI curves of the components on the card and identify the defective parts which is diode, condenser, mosfet, IGBT...

In general, these devices do the measurement correctly, but especially in circuits such as diode and condenser parallel.

The VI curve of the capacitor is shown on the display when measured at the end of the diode.

Is it posible to measure the diode VI curves, even though a capacitor is in parallel to it?

Is there a way to look at the parts without disassembling them?


texts: Confusion in minimum gate triggering current of SCR

texts:
I was reading an article about working and properties  of SCR from eleccircuit.com and in a section How to pick a SCR -it is written that we should check its rating and one of the mentioned rating in this article is - IGTmin rating (Minimum gate triggering current) i.e the minimum gate current that can trigger the SCR.
But isn't minimum gate current rating should be zero because at breakdown forward voltage we need no gate current at all  for forward conducting mode?
And how this minimum gate current (IGTmin) rating is calculated, what is its significance?


texts:
Context
I'm designing an audio amplifier input stage. This amplifier is fully differential. Among other things, one of the design goals is to have good CMRR for UNbalanced (single ended) inputs with RCA to XLR cables (pins 1 and 3 tied to GND at RCA connector).
I mostly succeeded in this goal, except for the high end of the audio spectrum. At 20kHz, the CMRR with unbalanced input drops around 30dB from CMRR at 20Hz. This is in case of a source output impedance of 600 ohm, unbalanced with the low impedance ground of the single ended output.
The cause of the declining CMRR at higher frequencies, is in fact the RF input filters of the amp. It consists of a 100 ohm - 100pF RC networks very close to the input connector, preventing RF signals reaching any electronics where they might be demodulated into audible signals. These 2 RC networks are implemented on pins 2 (hot) and 3 (cold).
My quest
If it would be possible to have a selectable impedance at pin 3 (cold input) that could be matched with pin2 output impedance at the source, the CMRR would be much better at higher frequencies.
This would mean 3 or 4 settings, preferably freely combined. A similar system is often found in phono preamps, where input loading resistors and capacitors can be combined with dip-switches.
The trouble is, that it must happen in the RF input network, where GHz signals should successfully drain to chassis instead of entering the signal chain. I have no clue if or how this could be implemented without compromising RF draining performance.
Edit: added schematic and simutaltion
The schematic is simple enough as it's a separate passive input connector PCB.
The added switches are imaginary for now as I have my doubts they can be layed out in a way that does not compromise RF performance.

Simulation of the input network. First unbalanced:

Next balanced:

Now these are theoretical results and component tolerances significantly reduce CMRR performance, but the large differences between balanced and unbalanced input signal remains.
Edit2: reactions to answers and comments
It has been suggested that RCA to XLR cables are nonsense and should be avoided because they have no added value. Well, I disagree. Consider this type of connection between an unbalanced source and a balanced sink:

In this scenario, the balanced cable can cleary do it's work with regard to noise rejection. Even with the high frequencies compromised, at low frequencies it's still effective and performing better than an unbalanced input. Furthermore, an unbalanced input allows noise currents on to the active PCB's where they can cause havoc with all single ended circuitry.  So, IMHO balanced inputs are always better performing, regardless the source that is connected to it.
Another suggestion was capacitive shunting of the differential input (behind the RF RC filter). A typical value would be 1nF. I had thought of this myself and it does indeed work in order to improve high frequency performance of CMRR. But it only works to prevent positive gains above 1Mhz, it does not change anything at 20kHz. Furthermore, this works equally well if implemented in the gain stage further down the chain.


texts: Negative input voltage on Isolated Differential ADC

texts:
I am trying to interface with negative voltage input signal ranging from -5V~5V or -10V ~ 10V.

Since the input signal may be floating or have ground reference, I am planning on galvanically isolating ADC and input side from everywhere else.

I am considering flowing configurations in below picture.

The absolute maximum voltage on the input pin of the ADC(AIN+ and AIN-) are -0.3V to (VDD+0.3V).

If I use the first configuration for +/- 5V range signal(floating or not floating), will it be able to get the signal correctly?

Also, the system may have to interface with +/- 10V range signal, I used simple resistive voltage divider in order to take the voltage level down to acceptable range.

Please look at the configuration and see if it's viable.


texts: RC circuit with sinusoidal voltage - initial behavior?

texts:
For a simple RC circuit with a sinusoidal voltage source, the differential equation is: $$\frac{dq}{dt}=\frac{sin(t)}{R}-\frac{q}{RC}$$ When I plot the solution to this differential equation using euler's method, I get this:

I'm confused as to what is happening in the first few cycles.
Does this have something to do with transient response? Or are the initial conditions in combination with the sin(t) source forcing it to do that?

Obviously, as t increases, it settles into an equilibrium, but why does it not start out in equilibrium?

Thanks for the help.


texts:
I'm flipping out because I cannot find the answer to this anywhere.  It's wholly philosophical.  In reference to the amps of power supplies/adapters:

If all that matters is that enough amps are supplied, why aren't all power supplies/adapters just built with something like 100 amps or maybe 10 amps?

Why have us running around wondering: "Does this supply enough amps?"?
Why do they not all just supply plenty


texts:
I have been experimenting with a Soundcard Oscilloscope and I am having some problems understanding what's going on! I have attached a screenshot of my digital scope setup. My hardware setup is simple. I have a male to male TRS jack running from my line out into my mic input. I have been experimenting with a simple sine wave.

When I measure the output voltage of my line out (Stereo plug - TRS) with a voltmeter I get a reading of 26mV for the right channel and 12mV for the left channel (Left and Right speakers not the left and right scope channels). However, the scope is reporting an effective voltage of 508mV rms for the left channel and the right channel (not in the screen shot) is saturated at 783mV rms.

Why do the 26mV and 12mV readings remain constant on the line out when I adjust the signal from my sine wave amplitude or change the volume and balance control of my PC soundcard? The voltmeter reading never changes. The voltage changes on the scope, but not on the voltmeter. What am I missing?

My second question has to do with the soundcard max voltage readings I am getting. When I boost the frequency or amplitude of the wave it saturates at 2 volts. I am guessing +2 and -2 is the max input/output of my soundcard? The research I have done would agree with this conclusion but I would appreciate some input! If this is the case why can't I get a 2 volt reading on the voltmeter instead of this micro volt jitter?

Thanks for your time!


texts: Is it possible to have a continuous quantized signal or a discrete infinite precision signal?

texts:
When converting an analog signal to the digital domain I understand that one does two things.

An analog signal is continuous and must be sampled in to discrete time segments (Discretization)
The analog signal ideally represents the true value but in the digitization must be quantized to specific values in our system (Quantization)

Is it possible to have one without the other, if so in what context? I hope i'm being clear with my question.


texts:
I came across Ben Eater's Youtube channel and website and thought I'd give the clock circuit a shot (possibly doing the entire 8-bit computer thing in the future). He conveniently put list of items online what's in the kit. I wanted to order it from him, but shipping is quite expensive as I am not based in the US.

I can find basically all items, I do have some trouble finding the ICs though. One is a Hex Inverter 74LS04, but I cannot find that one (and also not the 74LS08 and 74LS32).

When searching for an inverter I do find the 7416, could that be a decent replacement (I checked the datasheets, and I don't really see a big differences). Same for the AND and OR gates, can I safely use ones that look the same on the first look?


texts:
I am trying to clearly identify a fried ceramic capacitor in order to replace it. By chance, I could take a picture on another device of the same type:

So far what I found after some search:

I suppose that "101 K" is 100 pF +/- 10%.
SL2KV (or is it SL2KY?) might be: dielectric = SL, max voltage = 2kV ?
6D from "9 6 D" might be "2016 december/january" as it is written on some Murata capacitors.
Leads have "outside kinks" and 5 mm spacing. Diameter is around 6 mm.

The problem is that, when searching for this kind of component on Digikey, Farnell or Radiospares, there is either too many choices or not enough. I cannot find, for instance, what is the constructor or if it is single or multilayer.

More detail: I am trying to repair a TV whose stopped working, probably because of a lightning surge. The power supply board is showing 2 fried components: this one and a resistor I could easily identify. I hope by replacing these 2 components that the board will work again.


texts: Can the discharge when plugging a laptop to a power outlet can do any harm?

texts:
In this question the OP ask if (s)he should connect a power source into a power outlet first or into the laptop first. While the question has been closed, i think there is a very valid point to consider:

When I plug a laptop power adapter into the laptop first and only then into a power outlet, there is a big, visible and audiable discharge. I've been using several power sources and they all behave the same.

Can this discharge be harmful in any way? For example, can it overload the power source or damage the electrical contacts or the outlet? Or even get transferred through the power source to the laptop?

Returning back to the linked question: For many years I've been following the general principle to first plug a power source into a device and then to the power outlet, because the power source should shield the device from any jitter caused by plugging it in. (However I'm not a specialist and this could be completely wrong.) But seeing and hearing this discharge every time makes me a bit uneasy.


texts:
I have been working on this problem:

The way I approached this problem is given (I used Kirchhoff's laws on Electrical equivalent of magnetic circuit) :

I have two doubts here:

My working does not give the right answer, can someone tell the mistake in my solution?

As per the book's solution, "Total ampere turns is equal to that required for path E and that required for two paths C or D".

Can someone explain this?
PS: If my solution is not clear due to handwriting or other issues, please contact me by commenting, I shall explain you my method.


texts: Why does the transistor work with collector and emitter swapped?

texts:
simulate this circuit – Schematic created using CircuitLab

Yesterday, I saw a schematic exactly the same as this, except the voltage connected to the relay was 12 V and different from the voltage at the base (TTL levels). I told the designer that it wouldnt work because the collector is now more negative than the base and emitter; not how it should be for an NPN BJT.

Imagine my surprise when this guy simulated the circuit above (which, i think, is even worse than the original) in Proteus and the relay switched! I scrambled to figure out why this happened and noticed that as the base resistor was increased to 1k, the relay didnt switch again. But this didnt explain how the base-emitter junction became forward-biased in the first place, since there is exactly 0 V between the left of the base resistor and the rightmost terminal of the relay.

What crucial detail am I missing or do I not know here? Is there any condition when this general design would work as expected, to drive some load?

The actual transistor in the simulation was a TIP41 NPN BJT. The relay was a 2 V relay. When it was increased to 4 V, it still switched.


texts:
I'm having problems when I try to update programs in my STM32F407 discovery.

It was working well until I tried to use the PA13 pin as an input in my program. I tried to update the program, it didn't work, and after that I receive the errors:

  Error: libusb_open() failed with LIBUSB_ERROR_NOT_SUPPORTED Error: init mode failed (unable to connect to the target)

When I checked in the manual I saw that port PA13 is named JTMS-SWDIO and i used for JTAG or SW debugging. Is it possible that this assignment set another debug configuration?

If this is right, is it possible to perform a hardware hard reset on the board to delete this new debugging set up?


texts: Best Practices for Using Brass Standoffs Electrically?

texts:
I'm working on a project where I am trying to eliminate some cable assembly and connector costs. In my particular project I happen to have three brass standoffs that join together two boards. Board one is the mainboard, containing the power, mcu, and so on. The board I am joining to is essentially a single channel touch sensor. Right now I use JST connectors to get the job done and they work great, but add connector and cable assembly costs. I am contemplating just using the brass standoffs as the electrical connectors (already need to be there) and adding copper pads to both the boards to get the job done.
I understand people do this sort of thing but in researching mechanical solutions it looks like I'd just end up adding cost in terms of washers, since they have to be brass too and are not exactly cheap (washer suggestions welcome, btw) and they bring their own problems.
Is it a terrible idea to try and solve this with some loctite or hot glue? The design won't be subjected to extreme vibration or anything like that.
In general, is using standoffs electrically to be avoided? I would appreciate any sage wisdom on this topic.


texts: Voltage Rectifier Fails When Doorbell Button Shorts Inputs

texts:
I am working on a project that involves powering a 3.3V microcontroller off a doorbell transformer. The design uses a full-wave bridge rectifier (1) to convert the AC voltage from the doorbell transformer to DC, which is smoothed by a capacitor. A switching regulator (2) then converts the DC voltage from the bridge rectifier to 3.3V to power the MCU.

Since the doorbell still needs to function, a switch is used to trigger the doorbell chime. However, I am running into an issue: when the doorbell button is pressed, shorting the AC inputs to the bridge rectifier, it destroys the switching regulator.

One initial thought provided by a previous question was that the doorbell solenoid created a high voltage inductive kick that was killing the circuit. To prevent this, a bidirectional TVS diode was installed across the doorbell solenoid (3) for ESD supression. The bridge rectifier does not appear to have any issues and continues to function normally even after the switching regulator fails.

I am working to find a way to allow the doorbell to be triggered without damaging the voltage regulator and I would greatly appreciate any insight into why the regulator might be failing.

All of the datasheets for the components are listed below:

1) Comchip Technology DF206ST-G: Bridge rectifier

2) RECOM Power R-78E3.3-1.0: Switching regulator

3) Wurth Electronics 824501751: TVS diode

edit: In a previous question I thought that the bridge rectifier was failing. It turns out that it is actually the regulator failing.


texts: Removing ripples from PWM controlled LED in camera vision application

texts:
I have made a camera vision setup with highpower LED's which are controlled with a simple NE555 timer and a mosfet. The LED system is lighting up an area where a camera is looking, but unfortunately i am experiencing ripples/stripes on the video stream due to the nature of the PWM dimmer. Is there a way to reduce these stripes or even eliminate them?

The camera: http://charmedlabs.com/default/?page_id=211

NE555 circuit:


texts: which is the physical cause of hold time of a D flip flop? Why is it necessary to keep its input data constant for a certain amount of time?


texts: What PIC24 C compilers are out there, and what is your opinion or review on them?

texts:
Specifically, the PIC24 series.

I tried out microchips C30 compiler, but it seems to be a bit too complicated for me, and I couldn't find any libraries with it.

Then I tried CCS, and it seems far too simple, and I cannot view the code for say, I2C_write, which is quite unnerving for me.

What about Hi-tech C? I did not get a chance to check it out yet, is it in your opinion good or bad?

Are there any other C compilers for pic24 out there? Does not matter if they are free or not, as long as they have some examples.


texts: Best way to hand-solder this TQFP (SMD) component

texts:
So I'm working on a small project right now that requires a ATmega32U4RC. I'm trying to test/prototype with it, but it's a surface-mount component, so I can't just place it in my breadboard. So I found this, which is perfect for what I want.

The problem is that I haven't soldered in quite some time. I've also never soldered a component with such tiny leads.

Needless to say, I ended up with this:

Yea, I know it's bad :(
The solder-wick didn't really seem to want to do it's job (anyone know why this is?), so I couldn't really clean it up.

Are there any tips for doing this (tools that might help me, etc.)? Is there an easier way to do this than hand-soldering?


texts:
I am controlling a multiplexed LED matrix with a combination of an ADG1408 as power switch and a TLC5940 as current sink.
The system works almost perfectly except for some LEDs that do not stay OFF but turn ON very dimly. I attach a link to a GIF where the effect can be seen.
I saw this effect for the first time when I was prototyping on a breadboard, but it was only visible on the first LED. Now it is visible on two or three LEDs.
The schematic of the system is as follows:

What could be the reason for the LEDs not staying off? I tried adding some pull-down resistors on the logic pins A0, A1, A2 and EN but it made no difference.
The voltage on the LEDs is 10V with a fixed current of 0.01A


texts: Can a 1.3W rated SOT23 MOSFET deal with 0.9 W peaks?

texts:
I have a TL431 LDO voltage regulator that uses a tiny P MOSFET in a SOT23 case rated at maximum 1.3W (IRLML6401TRPBF). Can it handle 0.9W bursts of 1 second every 10 seconds without a heatsink?

I would put multiple MOSFETs in parallel but current won't be distributed evenly.


texts:
Today I ran out of gates on my Xylinx Spartan 3 (Basys2 by Digilent) FPGA.

This was not a surprise to me as I had implemented an 8 bit x 2048 array for use as an FIFO buffer.

Code: type MEMORY is array(0 to (MEM_L - 1)) of std_logic_vector(7 downto 0);

where MEM_L is an integer, value 2048.

I read through the product brief, and as I understand it there is 72 kB of bi-directional RAM on Spartan 3E series FPGA's.

However I do not know how to use it (program it) using VHDL. How would I go about declaring that I want some data to be stored in RAM memory?

Initially I assumed the use of RAM was up to the compiler (synthesizer and implementer tools) and that I was not able to control how it was used directly, however I suspect that I was wrong in this assumption, because the implementation process failed due to my FIFO being too large for the number of gates supported. (Approx 100 k gates.)

I should add that I wasn't able to find an answer through google, perhaps I didn't know quite what to search for?

EDIT: That should have said 78 kb of ram, 78000 bits.


texts:
The tool shed of my current residence has holes in it, and it rained heavily the last few weeks, during which the expected outcome of one of my flood lights blowing a fuse occurred.

I don't want to waste money replicating the scenario, but I am curious as to ask is the colour spectrum for the blown globe is purely coincidental, or is it an expected outcome?


texts:
I'm very new to electronics engineering, so please forgive me if I'm asking stupid questions!

I'm working on a device which is based around an Atmel Sam L21 ARM MCU with 4 UART devices attached (amongst other things), and powered by a couple of AA batteries. I've attached a very crude diagram of how things are connected, but I have the following questions:

Which pins are used to power the MCU? I assume it's either VDDCORE or VDDIN and a GND pin at the top.
Do I need to add decoupling capacitors between the power supply and the MCU?
Are the peripheral devices powered directly from the batteries, or through the VDDIO pins on the MCU?
Again, do these need decoupling capacitors between the peripherals and the MCU?

I've read a couple of really detailed posts on here that relate to how and when to use decoupling capacitors, and I'm planning on reading through them again today to get my head around it all, but if someone could help me out with this power supply stuff, I'd be hugely appreciative!