texts: 4N33, optocoupler, photodarlington, getting voltage without connecting any supply

texts:
We are using 4N33, optically coupled isolator (datasheet link). The circuit is shown below.
In the schematic with R3--> 10K, it was not working so we change to 200K ohm, C2 & ZD1 are not connected.
The 4N33 optocoupler is part of the circuit where it is being used for 28V power sensing.
The circuit where it is being used has linear voltage regulator of 9V & 5V connected. When the board is being powered ON, we are getting voltage at 3.3V bus, even without connecting 3.3V linear voltage regulator we are getting varying voltage between 0.7V to 2.8V. We are not able to understand even if 28V is not connected, we getting 0.7V to 2.8V in the 3.3V bus. After removing the 4N33 from the IC base, the voltage at 3.3V bus returned to zero.
Then we change the resistor R3 to 6.8M ohm, even with the IC connected the voltage is 0.02V.
Is it EMI noise which is getting amplified. How come without giving 3.3V we are getting voltage.


texts: Could HDMI be potentially used as a power supply alternative for smartphones?

texts:
I understand that HDMI's pin 18 carries a +5V charge.  Similarly, USB carries 5 volts and this is used to charge many smartphones with a micro/usb connector.

Could it possible to build a smartphone that charges with an HDMI port?  Would that be completely impractical currently?


texts: Handling design design exceptions in multi-channel designs in Altium

texts:
Let's say I have a design with 5 channels. All channels are exactly the same, except the last one which has limited functionality compared to the other 4 channels and thus doesn't need some of the components.
How to handle this in Altium without creating a schematic sheet for the 4 channels and a separate copy for the 5th with just the few changes? It seems I can't place a compile mask directive in a specific channel only.
At the moment I design all 5 channels the same, place them all and route them normally on the PCB and just don't populate the components not needed on the 5th.


texts: Can I use negative voltage generator TC7660 as voltage doubler to drive LED of MAXIM30101 oximeter IC?

texts:
I am trying to use two AAA battery to generate two power supplies,

1.8V(via regulator AM1117)
5-6V to drive LED (using voltage doubler TC7660).

Both these voltage is requirement of Oximeter sensor MX30101/MX30102.
Below is the schematic

I am using negative voltage out of TC7660, and use it as a ground input the LED supply(PGND) of IC MAXIM30101, this would generate equivalent voltage of 3V*2 =6V.
From datasheet of MAXIM30101(https://datasheets.maximintegrated.com/en/ds/MAX30101.pdf) it is showing different grounds for GND and PGND, but I still have doubt how is it different than having actual 6V power.
So can we safely use negative voltage generator as a voltage doubler supply power to LED driver?


texts: 2 Switch Forward Converter Volt-Sec/Charge Balance

texts:
I am attempting to design a 2 switch forward converter. I understand how to do the volt-sec balance and charge balance when the converter is as shown in the ideal 2 switch forward converter below.

I get confused on how to apply these steady-state analyses when a DC link capacitor is inserted, along with the leakage inductances. I understand volt-sec balance for the magnetization inductance though.

The circuit I am talking about is here please disregard component values as I am just trying to grasp theoretical operation:

simulate this circuit – Schematic created using CircuitLab

For instance, let's say the converter is in the first mode which is when both FET's are on. How do you apply the volt-sec balance to the secondary side? would the KVL for the secondary side look like Vsecondary - Vleak_inductor_secondary - Vmain_inductor - Vout = 0 (please accept the polarities I have assumed)? If so how do you deal with the leakage inductor in the overall equation when determining the input to output voltage relation? Also, it seems that the inductor would ramp up during this stage of when the FETs are on, but at the other stage(s) how does this inductor burn off the energy so it doesn't continually ramp up each cycle? Back through the transformer?

For the DC link capacitor does charge balancing need to be applied? And should I incorporate this capacitor's effect in the charge balance waveform on the output capacitor?

Hopefully, my questions are clear but if they are not please let me know.

Thank you in advance!


texts: re-attach battery driven gamepad to PC power supply

texts:
There are times at that I get mad about empty AA batteries or accumulators losing their capacity too early. And since the gaming computer is running anyway, I thought about using one of the molex connectors to run a wire out of the computer casing and use it as power source for the currently battery-driven gamepad.

The plan:
Molex connector gives 12V/5V, convert the 5V to 1.4V

My tests:

AA akku, Multimeter, Gamepad:  the gamepad drains roughly 60mA
power supply, Multimeter, electronic parts:
5V of power supply are converted to 3.3V by a MCP1702-3302;
the remaining 1.9V shall be reduced by ~30 Ohm resistors in series.
As the power supply is switching power to the 5V and the MCP1702 is also switching to 3.3V, I added a 10V/2200 microFarad capacitor at the end, before running power to the gamepad and connecting is to ground.

Result:
The gamepad's power Led is fading/blinking, the device is not working.

I understood that resistors reduce power and current, thus I took the current into account:
R= U/I = (3.3V-1.4V) / 0.06A = 31.67Ohm
Measuring the resulting voltage with the gamepad attached was driving my multimeter crazy.

Is my approach okay?
Does the capacitor flatten the switched power enough to simulate a battery?


texts: How to connect chip pin to either vcc or groud externally?

texts:
I have a board that i use ic which one pin need to be externally decided to be connected to VCC or ground based on LED lightening

The schematic use this symbol for a connector to indicate this

How can i implement this in my PCB ?


texts:
Please go easy on me as I am new to Altium and not much of a software geek - actually have no idea what a script is. Anyway - question is - how do I add a script to Altium Designer, and how do I execute/run it? Is it as simple as downloading these files and dragging them into the Altium interface?
I downloaded the files here: https://github.com/Altium-Designer-addons/scripts-libraries.
I then opened Altium and pressed File > Launch script, and navigated to the folder where the script I want to execute was held. This is the "planarTX" script.
The issue starts here. Once I have pressed the script to execute it.. nothing happens. Just goes back to the normal grey screen as if nothing has happened. Am I missing something here?
EDIT: I am able to launch other scripts in Altium. For some reason, this particular script will not work...


texts: Reading the Amperage of a DC Current Source using a Multimeter

texts:
Hello everyone this question is probably basic but i am having problems with a current source that i am trying to test:

So if memory doesn't fail me you connect the black connector to ground and the red one to positive and then i should get the amperage which in this case is in miliampers and should say 60 but i get always 0, of course the unit might be malfunctioning but i can get the voltage ok, what am i doing wrong? or the unit is to blame?

Update 1

I made two mistakes so far, one i had my probe on A instead of mA, and second i had the black probe on ground, now i switched it to "-", however my result is now 10mA instead of 60mA

Update 2

Well after much tinkering with the unit i found the problem, some of the components on the motherboard are dead, either downright broken to just not giving any reading when probed with the multimeter. So the answer is that the unit is defective. However @Tony Stewart. EE since '75 was the closest to the root of the problem so i selected his answer as right. Thanks everyone!


texts: is there any impact of Electron's spin in CRT?

texts:
fact-1. Electron's (or any-other particles) magnetic behavior depends upon mass, charge and spin.

fact-2. All electrons are not the same. Though all electron have the same mass and charge; an electron can have any 1 of the 2 possible "Spin"... (+1/2) and (-1/2) (though later-on the electron can flip to opposite spinned state).

fact-3. Moving electrons, in CRT TV, deflected using Magnetic Coils.

Now , my question is, does all the electrons coming out from the cathode in a CRT TV, deflected irrespective of spin (i.e. deflection in CRT does not depends on spin)? or some-how the cathode release all electrons of same spin? or indeed depends upon spin?


texts: How do IC's know when there is a downward or upward transition of a clock pulse?

texts: Title pretty much says it all.  But how do most IC's, micro-controllers, etc. know when a clock cycle starts a downward or upward transition from the clock source?


texts: How to compensate for grid quality changes in three phase power

texts:
Suppose I measure both current and voltage going to an electric motor. So that I have two continuous streams of three phase data (current and voltage).

I want to use this data to diagnose potential problems with the motor. Some motor faults are supposed to have a small effect on the current pattern of the motor.

The way I understand it do changes in the grid mean small variations in the voltage. Either in the RMS or in the frequency of the measured voltage. If these differences are small over time, the grid quality is good. If the differences are big, the grid quality is poor.

Since I measure both current and voltage my intuition says I should be able to go to a representation which is more or less invariant to these small changes in voltage. I was thinking about the instantaneous electrical power.

I know instantanious electrical power is given by:

P(t) = I(t) * V(t)

So I could multiply the current waveforms with the voltage waveforms and get the instantanious power.

However, what I am not sure of is what the effect is of small variations in voltage due to changes in the grid. For example, how do these changes affect the current and the power? I assume the motor runs the same before and after a small variation in the voltage, is that correct? If I look at the instantaneous power instead of at the current, am I less susceptible to changes in the grid than when I look at just the current? Or do you know of other/better ways to compensate for changes in the grid?


texts: Coefficient of coupling in Resonance circuit

texts: How to find coefficient of coupling in B/w 2 inductor are in series RLC CKT


texts:
I'm a beginner-ish in PCB making and I want my workflow to be faster by using an oven instead of doing all the solder by hand. I searched for few hours without answer to my question.
A low temperature solder paste melting point is 138°C, so around 165°C reflow.
On the datasheet of all my IC, it is written that the Absolute Max temperature is 150°C.
I want to know if it's okay to go over the max temperature of ICs to solder them to a PCB in an oven.
Am I forced to use low temperature solder paste, or can I go with higher melting point solder paste?
The main IC I have are power mosfets and a ESP32 Wrover (which is pre-packaged).


texts: TTP223 capacitive sensor on USB switch takes two presses to work

texts:
I'm trying to solder a TTP223 capacitive touch sensor to a USB switch (specifically a "UGREEN USB 3.0 Switch, 2 In 4 Output") to rig a sort of capacitive KVM switch to a desk PC I'm building, however I'm having trouble with it. It seems that when I connect the VCC and IO ports to the switch, it takes two presses of the button to work and I'm not entirely sure why. I've tried the same thing with a DisplayPort switch (CABLEDECONN DisplayPort 8K DP 1.4 Switch) and it works fine.
Apologies if I've missed any important details, this is my first real dive into anything electronics based, so I'm not even really sure how to go about debugging it. I haven't connected the ground wire to anything, and I'm not sure if it should be. Does anyone have any ideas of what may be the issue, or how I go about testing things?
Below I have a picture of the board that does work:

and the one that doesn't:

EDIT: I've tested both boards with a multimeter, and the voltage over the DisplayPort board is 3V whereas the USB has 5V. I'm guessing this has an impact, but I'm not really sure what to do about it.


texts: LED modulated @ high voltage -vs- constant @ low voltage

texts:
I'm experimenting with LEDs with Arduino and have a question.
For example; I have one basic 20mA LED that runs constant at 3.3v.
I have another LED with that I PWM with a low duty cycle (6%). I up the voltage of this LED by x%~.

I have learned from this experiment that if the second LED passes the 20mA, it burns out.
That's why currently it has to run less bright than the first LED. By my calculations (V/A measurement) it comes at 33%~ of wattage used by LED 1.

My question is: say I replace LED 2 with a LED rated with a higher amperage, will I match the brightness of LED 1 with same wattage used? Or will LED 2 still experience more stress and energy loss to heat?

(I intended the question to be applicable to a broad range of LEDs, not just 20mA LEDs)

Duplicate question

For other readers wondering, this is another post with a similar question:
Does pulsing an LED at higher current yield greater apparent brightness?

Edit

I found out some new things (also thanks to that link); some LEDs are notably more efficient when current is overdriven. Big LEDs are inefficient regarding this.

Also resistors will burn a lot of heat, and limit the rise of current (so a much higher voltage is needed to force the current through the LED than without resistor in front). I noticed one of my COB LEDs has resistors on it, and at roughly the same brightness, the resistors will seriously heat up and overall the COB LED will be inefficient. Perhaps matching the resistor better for the overdriven scenario would work, but at the moment I am relying on my variable voltage supply and no resistor at all.

I seem to have success with a 3W LED, running at 1 W. By eye, the constant and the overdriven PWM'd seem to have the same brightness per watt.
My theory is that using a higher rated LED and running at an average lower wattage increases efficacy per Watt; which is generally true but especially so when overdriven.
I had less success with a few COB LED strings in parallel with a resistor each, I assume because of the earlier mentioned resistors burning a lot of energy.


texts: Finding out antenna gain in 3-D space (azimuth and elevation)

texts: I found a cross-sectional view of a patch antenna's gain below. I would like to know how can I determine the antenna's gain for every azimuth and elevation angle in 3-D space?


texts: Stepper: Distribution of Microsteps within a full step

texts:
I am currently working on a project to precisely move a XY-table using stepper motors in microstepping mode.  The goal is to reach 1/16 microstepping and there is an encoder with 4000 pulses per resolution to account for missed steps.

In full-step mode the steppers work correctly, but in microstepping mode the motor steps only every n-th step, e.g. every fourth in 1/4 microstepping and every eighth in 1/8 microstepping mode. This was tested by stepping at 1Hz and observing the motor.
I expected the microsteps to be approximately equally distributed within one full step (i.e. 1/4 microstepping = 1.8° / 4 per step = 0.45° microsteps), is this a misconception? If so, what is the point of microstepping if you can still only reach full steps accurately?

Several motors of different makes where tested, with the load of the table aswell as without it, but they all show this behaviour.

Hardware used is:
Stepper Motor Controller: Texas Instruments DRV8711
Stepper Motor: Nanotec ST4118S1404-B
Pulsegeneration: STM32F446ZET
Evaluationboard: Pololu High-Power Stepper Motor Driver 36v4

Any tip is helpful, as the project is missing its point without sufficiently accurate microstepping.

Currently my guess is that the stepper-drivers circuit is faulty or it is misconfigured. To address the circuitry issue we ordered an evaluation board which we will test this week.


texts: PTH drill diameter do the IPC take the pin distance in account?

texts:
I wonder if the IPC take the Pin distance tolerance in account for the drill diameter? (see p in pic). I can't find any guidelines for it anywhere.

Or is it just so that it's implicitly,common sense that the drill diameter shall be: pin tolerance distance + maximum pin diamter = minimum drill diameter?

That is what I would assume if there isn't any guidelines in any IPC?


texts:
I'm using STM32F103.I'm trying to make a code that run every second.
here is the code

//Clock is 32Mhz
unsigned long usStart,usStop;
CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
DWT->CYCCNT = 0;
DWT-> CTRL |= DWT_CTRL_CYCCNTENA_Msk;
usStop = DWT->CYCCNT / 32000;
While(1){
usStart = DWT->CYCCNT / 32000;
if(abs(usStart - usStop) >= 1000){
    HAL_GPIO_TogglePin(GPIOC,GPIO_PIN_13);
    usStop = DWT->CYCCNT / 32000;
   }
}

After aproximatly 20second the code crash and stop working.
I couldn't figure out why this happens.I thought that was because of the CYCCNT overflows so I added abs() in the diffrence calculation but still the same problem.


texts:
I'm writing bare metal firmware for an STM32F070. When I set the AHB Prescaler (AHBCLKDivider) to a value greater than 1, the systick interrupt never happens, i.e. SysTick_Handler() is never called. This in turn makes HAL_Delay() hang the system when called.

Why is this happening? Is it possible to have the systick interrupt enabled when using the AHB Prescaler?

My clock initialization code is below. I tweaked it based on code generated by STM32CubeMX.

Also, what is the meaning of the parameter that is passed to HAL_SYSTICK_Config()? Does it need to be adjusted based on the prescaler settings?

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

   /**Initializes the CPU, AHB and APB busses clocks
   */
   RCC_OscInitStruct.OscillatorType =
      RCC_OSCILLATORTYPE_HSE |
      RCC_OSCILLATORTYPE_HSI |
      RCC_OSCILLATORTYPE_LSE |
      RCC_OSCILLATORTYPE_LSI |
      RCC_OSCILLATORTYPE_HSI14;
   RCC_OscInitStruct.HSEState   = RCC_HSE_OFF;
   RCC_OscInitStruct.HSIState   = RCC_HSI_ON;
   RCC_OscInitStruct.HSICalibrationValue = 16;
   RCC_OscInitStruct.HSI14State = RCC_HSI14_OFF;
   RCC_OscInitStruct.LSEState   = RCC_LSE_OFF;
   RCC_OscInitStruct.LSIState   = RCC_LSI_ON;
   RCC_OscInitStruct.PLL.PLLState = RCC_PLL_OFF;

   if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
   {
      Error_Handler();
   }

   /**Initializes the CPU, AHB and APB busses clocks
   */
   RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                               | RCC_CLOCKTYPE_PCLK1;
   RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_HSI;
   RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1; //TODO
   RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;   //TODO

   if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
   {
      Error_Handler();
   }

   PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_RTC;
   PeriphClkInit.RTCClockSelection    = RCC_RTCCLKSOURCE_LSI;

   if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
   {
      Error_Handler();
   }

   GPIO_InitTypeDef gpioInit =
   {
      .Pin  = GPIO_PIN_0,
      .Mode = GPIO_MODE_OUTPUT_PP,
      .Pull = GPIO_NOPULL,
      //.Speed = GPIO_SPEED_FREQ_LOW,
      //.Alternate = 0,
   };

   /**Configure the Systick interrupt time
   */
   HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq() / 8000); //TODO: is this correct when using prescalers?

   /**Configure the Systick
   */
   HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK_DIV8);

   /* SysTick_IRQn interrupt configuration */
   HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}


texts:
I am building a small water pump (5 V) controlled by an Arduino, and I want to reduce voltage from 9 V to 5 V.

Do I need to use capacitors when using an L7805CV voltage regulator?


texts:
I made an Hidrogen generator (HHO) like YouTube :
https://m.youtube.com/watch?v=zq8YMON9hjA&list=PLPCtNZjqSVUhWVzuxEkzlyrz1CatH8OiF&index=29&t=504s
but , it does not working at all.
Electric issues- I Do not know why.
Especially , in the project it îs not mention the electric resistance.
I put the component into a PC frame.
I made an electrolite with KOH 15-20% of water of about 2kohms. I used a PC 12V source 20 A. And nothing happened inside of Orange collor- photo- Hydrogen generator- see Photos- no Bubling, no Hydrogen.
I made exactly , except electrolite- it îs not specified the concentration or resistance, please help me with some ideas.The man who made the project does not answer to my question at comments of video clip.
Many thanks.
Costas.


texts: square 3 bit input using two 3 bit adders and logic gates

texts: I am trying to figure out how to make a circuit that squares a 3-bit input using 2 3-bit binary adders and logic gates. Could someone point me in the right direction on how to design this? Thanks.


texts: Antenna Design for Omnidirectional transmission

texts:
I have been working on a custom drone for quite some time now. One thing I have found an issue with is the remote control antenna orientation in relation to the drone. In some directions I will get absolutely no signal. (The antenna type pictured below).

On the receving end, I am using a standard NRF24L01+ with a PCB antenna.

Eventually, I would like to add another PA+LNA version to the drone with a lightweight antenna such as this.

Is there a better antenna design that will give me omnidirectional transmits and receives? On the remote control I do not care about weight so they can be as heavy as they like, but I would like to keep the weight as little as possible on the drone, which is why I bought the "wire-like antenna".

I know that each antenna needs to be used for a correct frequency, in this case 2.4Ghz, but other than that I do not know much about wireless antennas.


texts: Communications engineering, call arrival rate, poisson

texts: I am taking a course in communication engineering which involves some probability theory that I'm not quite familiar with. Please see the attached image for my problem. I don't get why that equation is valid. The two events are dependent (call arrival and call failure) so I initally thought an application of Baye's rule would solve it. Can someone please explain this to me?


texts: My rechargeable Ni-MH AA batteries went through the wash in my pocket! Are they safe to use?

texts: I havent used them yet, but I'm getting the impression they will be fine to recharge and use after they dry out.  Is this true?


texts: Generation of sine waves within the audible range using a DAC

texts:
I am trying to generate up to 20 khz sine wave with the TLC5615 DAC but have only been able to obtain a maximum of 100 hz. I am using a 20 MHZ atmega328 MCU to transfer the required 16 bits (2 padding, 10 bit precision, 4 dummy bits) and also to act as the software defined clock for the device. In order to generate the sine wave I have a lookup table with ~64 values in order to obtain a decent sine wave.

Here is all of the code

int sine[] = {0x7fc ,0x868 ,0x8d4 ,0x93c ,0x9a8 ,0xa10 ,0xa78 ,0xadc
,0xb3c ,0xba0 ,0xbfc ,0xc58 ,0xcb0 ,0xd04 ,0xd58 ,0xda4 ,0xdf0 ,0xe34 ,0xe74
,0xeb0 ,0xee8 ,0xf1c ,0xf4c ,0xf74 ,0xf98 ,0xfb8 ,0xfd0 ,0xfe4 ,0xff0 ,0xff8
,0xffc ,0xff8 ,0xff0 ,0xfe4 ,0xfd0 ,0xfb8 ,0xf98 ,0xf74 ,0xf4c ,0xf1c ,0xee8
,0xeb0 ,0xe74 ,0xe34 ,0xdf0 ,0xda4 ,0xd58 ,0xd04 ,0xcb0 ,0xc58 ,0xbfc ,0xba0
,0xb3c ,0xadc ,0xa78 ,0xa10 ,0x9a8 ,0x93c ,0x8d4 ,0x868 ,0x7fc ,0x794 ,0x728
,0x6bc ,0x654 ,0x5ec ,0x584 ,0x520 ,0x4bc ,0x45c ,0x400 ,0x3a4 ,0x34c ,0x2f4
,0x2a4 ,0x258 ,0x20c ,0x1c8 ,0x188 ,0x148 ,0x110 ,0xe0 ,0xb0 ,0x88 ,0x64 ,0x44
,0x2c ,0x18 ,0xc ,0x0 ,0x0 ,0x0 ,0xc ,0x18 ,0x2c ,0x44 ,0x64 ,0x88 ,0xb0 ,0xe0
,0x110 ,0x148 ,0x188 ,0x1c8 ,0x20c ,0x258 ,0x2a4 ,0x2f4 ,0x34c ,0x3a4 ,0x400
,0x45c ,0x4bc ,0x520 ,0x584 ,0x5ec ,0x654 ,0x6bc ,0x728 ,0x794};

#define samples 120

#define intL 16

void setup(){

  pinMode(11,OUTPUT);
  pinMode(12,OUTPUT);
  pinMode(13,OUTPUT);
}

int j = 0;
int k = intL-1;

unsigned int cval = 0;
int current = 0;

byte currentBit = 0;

void loop(){

  PORTB = B00000000;

   cval = sine[j];

  while(k != 0)
  {
    currentBit = (cval >> k) & 1;

    if(currentBit)
    {
      PORTB = B00010000;
      PORTB = B00110000;
      PORTB = B00010000;
    }
    else
    {
      PORTB = B00100000;
      PORTB = B00000000;
    }

      k--;
  }

   PORTB = B00001000;

  k=intL-1;

  j++;

  if(j == samples)
  {
    j = 0;
  }
}

Within the loop method I maintain a counter of the current value of the wave. I also maintain a counter of the current bit that needs to be written and in order to write in LSb order, that counter has to count backwards. Then I shift the word by that specified amount. After I know the value, I trigger the clock, write the value and set the clock once more. After the word has been shifted into the DAC you have to drive Chip Select input high.

I am afraid this is about performant as it could get using the lookup method, so I would like to know if there are any alternatives or what I need in order to achieve ~20 khz frequencies.


texts: Where to find I2C register information for MAX21000+?

texts:
The datasheet for the MAX21000+ IC contains a table listing all of the registers and their default values but doesn't include any description of each of the register bits.

I assume there must be a supporting document but can't find it anywhere. Any ideas?

The datasheet can be found here (warning PDF): http://datasheets.maximintegrated.com/en/ds/MAX21000.pdf


texts: High-frequency voltage amplifier (opamp) keeps clipping and oscillating

texts:
I've been working with the following very basic opamp circuit:

simulate this circuit – Schematic created using CircuitLab

I've built this Voltage amp a few times for a couple of low-frequency opamps, and it never let me down. I now need to amplify a high-frequency signal for the first time, however, so I switched to the OPA699 in the hope of amplifying a ±10 MHz signal.

The above image shows the exact circuit I built. I built it "dead bug style", meaning the opamp has been glued upside down onto a copper plate, and all resistors have been soldered together mid-air. The copper plate functions as a ground plane. The opamp is directly connected to a power supply, which is specifically designed to supply an extremely stable (there's some huge capacitors in there) ±5V voltage. The input signal is a 100 Hz sine, supplied by a TABOR 8020 function generator through a small cable, while the output is readout using a BNC bus connected to my oscilloscope.

Now my problem: when I build this circuit with my low-frequency opamps, both on a breadboard and dead bug style, all is well. But with this high-frequency opamp, the circuit doesn't work. When I don't apply any voltage to the input whatsoever, the opamp still clips. Applying a small DC input voltage doesn't change a thing.

All that appears to generate any output whatsoever is applying a signal that is sure to overload; a 5Vpp sine wave for instance gives a very noisy clipped sine wave as output. The output is then riddled with 12 MHz noise.

When I attempt to apply an offset to the opamp, I again get MHz-range noise.

I'm starting to believe that either the OPA699 isn't built for such a voltage-amplifier circuit, or that I'm making a huge mistake in my circuit. I know that at high frequencies, opamps can start oscillating (which is why I opted for dead-bug-style), which might invalidate my circuit. Is there any way I can get this to work?

TL;DR: I built the above circuit. When I give a sine input, the output either clips completely or consists mostly of MHz-range noise. I'm thinking that either I'm misusing the OPA699, or perhaps my circuit is not meant to be used in high-frequency applications.

OPA699 datasheet: http://www.ti.com/cn/lit/ds/symlink/opa699.pdf


texts:
I want to parallel connect 4 x AA NiMH batteries rated each at 1.2V, along with 4 x 1N4001 simple diodes to prevent unwanted current flow (recharging) between batteries. The electric circuit is:

simulate this circuit – Schematic created using CircuitLab

I get an estimated output voltage of 0.7V (because of 0.5V voltage drop for the diode).

How can I rise up the voltage from 0.7V to 5V and also have the possibility of a minimum current of 1A for the load resistance? If wiring restructuring is needed, then please offer parallel design solutions, because I need as much as possible amp capacity (2700 mAh * 4).

I tried this U1V10F5 step-up voltage regulator from Pololu (https://www.pololu.com/product/2564) and it gives me 5V, but somewhere in this circuit I think there is a high resistance (possible some current blocking from the diodes?), because the output current can't power up even a regular LED, when it's put in place of a resistance load (with some adequate resistance for the LED of course).

Thank you so much!


texts: Why does my non latching relay design not switch back to original state as I expect?

texts:
I am using the EE2-12NUL relay and the LL4148 flyback diode. I am controlling the relay with a GPIO pin from an MCU connect to some mosfets. The coil current is 11.7mA for this relay. When not energized the relay should switch back to Pin 3 but I am running into the issue where when I pull the 12V power supply jack while Pin 4 is connected to Pin 5 (by writing a 1 to GPIO_WRITE), the relay output, Pin 4, stays with Pin 5 and does not switch back to Pin 3. This does not always happen, I get into this state about 1 out of every 5 times I try this.

When I put the 12V power supply jack back in after this has happened (Pin 4 is still connected to Pin 5), I measure Pin 1 of the relay and voltage is 0V (as expected since my GPIO_WRITE =0 at the start) but the output of the relay is still connected with Pin 5 so it seems like MCU has no control over it. The only way to get it back to pin 3 is to write a 1 then write a 0 from my MCU. If I just write a 0, it will not go back to original state. When I write a 1, I expect the relay not to click since it is already connected to Pin 5. But I still hear a click.

I read that flyback diodes alone may not always be sufficient, and to install a cap between the coil supply and ground to act as a back-up power source allowing the relay to toggle properly. I added a 10uF cap to Pin 1 and GND but then my relay seems to never switch back to it's original state of Pin 3 regardless of what I do.

I have attached the portion of my design and help would be much appreciated!


texts: How do PCI Express Graphics Cards pull power from both the slot and the external 6-pin connector?

texts:
A x16 PCI Express slot can deliver 75W for PCI Express Graphics Card. Some graphics card today also use external PCI Express power to increase above this limit, the most basic of these is the 6-pin PCI Express graphics power connector. This is specified to deliver 75W, bringing the total allowable power of the graphics card to 150W.

What I am unsure of is how does the graphics card balance it's load from these two sources of 12V power? Does it use a current-limiter on both sources or is the set up more complicated than that?


texts: How to convert lumped components to TL segments?

texts:
I have the following circuit:

which I need to implement in Microstrip. For now in order to get the correct results I was using lumped capacitors. But I will need to use Microstrip stubs when fabricating the board. How can I convert the circuit into one using stubs instead of these lumped elements.

Looking forwards to your suggestions.


texts: Step Response RC Circuit: Current at Capacitor

texts:
I have a problem understanding why is that ic=0 at t<0 if the switch is closed for a long and only opened for t=0?

My friend told me that at t<0, the ic will always be 0A regardless whether the switch is open or closed. Is this true?


texts:
I recently started using circuit simulation software that is warning me that I have a "capacitor loop with no resistance" and then refuses to run any simulations until I correct the problem.  I can trigger this warning simply by creating a circuit with a battery and a capacitor tied together.  I don't understand the prohibition of connecting a circuit this way as it does produce measurable effects in the capacitor.

Can anyone help me to understand what this warning may mean and why I should avoid circuits that are connected this way?


texts: Common-collector output resistance and common-base input resistance

texts:
A circuit analysis shows that the small-signal output resistance of the common-collector circuit (without consideration of the emitter resistance RE) is different from the small-signal input resistance of the common-base circuit (identical DC operating point assumed). In both cases, the test signal is applied as a voltage to the emitter terminal.

What is the clear and descriptive explanation for this (without formulas) ?


texts: Calculating thevenin equivalent for a circuit with resistors in a configuration I don't understand

texts:
Having a hard time working out Thevenin equivalents when I see circuits like this:

Vs - 30V,
R1 - 100 ohms,
R2 - 1000 ohms,
R3 - 1500 ohms,
R4 - 900 ohms

So, right off that bat, I'm not sure I understand which resistors are in series or parallel.  I thought that R3 and R4 are in series, and (R3 + R4) is in parallel with R2, and all of that is in series with R1.  It doesn't seem correct, as I end up with the wrong answer.

If I was right, that would make it look like a voltage divider.

So, I come up with:

$$(R3 + R4) || R2 = \frac{1}{\frac{1}{1500\Omega + 900\Omega} + \frac{1}{1000\Omega}} = 705.88 \Omega $$

And then to figure out the Vth, I do:

$$V_{th} = 30V * \frac{705.88}{705.88 + 100} = 26.28V$$

I know that's wrong (I have the solution to this problem), but how do I really figure it out?

For Rth, I shorted out Vs, and figured out that ((R1 || R2) + R3) || R4.

That gives me...

$$((R1 || R2) + R3) || R4) = \frac{1}{\frac{1}{((\frac{1}{\frac{1}{100\Omega} + \frac{1}{1000\Omega}}) + 1500\Omega)} + \frac{1}{900\Omega}}  = 574.8 \Omega $$

which actually comes out correctly!

Thanks in advance


texts: Finding the voltage across a inductor in a charged RLC-circuit

texts:
Well, I've the following circuit:

simulate this circuit – Schematic created using CircuitLab

  In the circuit I want to find the voltage \$\text{V}_{\text{Y}_1}\left(t\right)\$ as a function of time, after I open the switch (this switch was closed 'forever' theoretically seen). And the question is: is my derivation for the voltage across the inductor correctly?

My work:

When the switch opens, the direction of the current in the inductor does not change, so the current will go in the direction of the red arrow in the circuit I've drawn down here:

simulate this circuit

When the switch is open we can find the current in the circuit using Faraday's law:

$$\text{V}_{\text{R}_1}\left(t\right)+\text{V}_{\text{R}_2}\left(t\right)+\text{V}_\text{C}\left(t\right)=-\text{V}_\text{L}\left(t\right)\tag1$$

Using the voltage and current relations in a resistor, inductor and capacitor we can write equation \$(1)\$ in terms of the current, \$\text{I}\left(t\right)\$, that will run trough the circuit when the switch is open (this current is the same trough all the components because it is a series circuit):

$$\text{I}'\left(t\right)\cdot\text{R}_1+\text{I}'\left(t\right)\cdot\text{R}_2+\text{I}\left(t\right)\cdot\frac{1}{\text{C}}=-\text{I}''\left(t\right)\cdot\text{L}\tag2$$

In order to solve this DE, we need two initial conditions:

The first one is pretty simple, when the switch is closed the maximum current that will run trough the coil is equal to \$\text{V}/\text{R}_1\$. So when I open the switch at \$t=0\$ that current will be running trough the inductor:
$$\text{I}\left(0\right)=\frac{\text{V}}{\text{R}_1}\tag3$$
At the point \$\text{I}'\left(0\right)\$ we get that:
$$\text{I}'\left(0\right)=0\tag4$$

  So, now we are able to solve that DE that is written in equation \$(2)\$. I solve it using Mathematica.

Now, in order to find the voltage across the coil we can use the voltage current relation in an inductor:

$$\text{V}_\text{L}\left(t\right)=\text{L}\cdot\text{I}_\text{L}'\left(t\right)\tag5$$

So, in the end we get that the voltage at the node \$\text{Y}_1\$ is given by:

$$\text{V}_{\text{Y}_1}\left(t\right)=\text{L}\cdot\text{I}'\left(t\right)\tag6$$

Where \$\text{I}'\left(t\right)\$ is the derivative of the solution to our DE out of equation \$(2)\$.

If I plot my solution, using the values that are given in the circuit I get the following graph:

  QUESTION: is my method of derivation right or did I make a mistake?


texts: Voltage and current don't seem to match up

texts:
Between two pins I'm measuring 2.1V but 0.04 mA. What does this mean?

I'm trying to light up an LED on an LPC2148. I set pin 2 to high and connected my LED to it and pin 14. It doesn't light up. When I use a multimeter to measure the voltage between these two pins, I measure enough voltage, but when I switch the multimeter to measure current, I read almost no current.

So what's up?


texts:
Logic gates like AND, OR, NOT etc. often come packed as arrays in ICs.
Sometimes not all gates are used in a project.  I would like to know how the remaining unused gates should be connected to achieve minimal influence on the system (energy consumption, interference) based on which technology (CMOS, TTL,...) is used.

My application uses a CMOS based hex inverter (CD4069) and the documentation doesnt provide this information.

Note: This is not about several inputs to a single logic gate. In this case connection of the unused pins would be the consequence of keeping the gate functional.


texts: I used the component wizard in Altium to automatically create a footprint but it decided to overlap the solder mask expansion with neighboring pads. Is this ok or should I change it such that there is a gap between each pad.


texts:
Reference https://www.pcbway.com/orderonline.aspx.

This is from a Chinese PCB fab. You can see that they offer copper traces up to 13 oz.  That seems thick, and according to my KiCad calculator, it's 0.45 mm thickness of copper carrying 23 A/mm width (25 deg. rise) .
I would have thought that with so much side material and a minimum 8 mil width, the etchant would simply undercut the tracks. That's a maximum ratio of \$1:2\frac{1}{4}\$ width to height.
What are such thick PCBs possibly for, and what would you mount on them? And would you have several layers?


texts:
I'm working on an electronics project and decided I need (among other things) an ESD diode to protect my inputs. I selected a diode which should do the trick:
https://www.digikey.ca/product-detail/en/vishay-semiconductor-diodes-division/GSOT05C-E3-08/GSOT05C-E3-08CT-ND/1680616

I was going to use this for everything: signal input, Vcc, etc. Looking farther down the Digi-Key page, though, it says:
Power Line Protection: No.

The data sheet says the diode can protect "two signal or data lines," and does not claim it will not work on a supply. I see no reason why I can't use the same diode on a 5V Vcc net if I'd use it on a 5V logic net, so what's up with this bizarre "power line protection" stuff? I searched high and low for app notes, etc., but didn't come up with anything.

Any insight into this will be appreciated. If there isn't a satisfactory answer, I'll go ahead and use this "signal/data" diode on my power nets!


texts: Naming 6000 counts multimeter in digit format

texts:
A 4-digit multimeter is also called 9999 counts; and it is called 4-digit because all four digits can display numbers from 0 to 9.

A 3½ digit multimeter is called 1999 counts; and it is called 3½ digit because three digits can display numbers from 0 to 9 and the most significant digit can display only 0 or 1.

This multimeter on the other hand is described in its specs as 6000 counts. I guess this means the most significant digit can display a number from zero to 6 or to -6 (?). But in this case we cannot call it 4-digit because its most significant digit cannot display numbers 7, 8 or 9. We cannot call it 3½ digit because its most significant digit can display numbers 2, 3, 4, 5 and 6. Does that mean this multimeter cannot be named as "... digits"?


texts: Solar powered charger circuit for a single LiFe cell

texts:
I'm looking for a solar powered charger circuit for a single LiFePo cell. The load is a low power MCU with some sensors attached, and when sufficient solar power is available, it should be used to charge the battery and supply the circuit. I had a look at some ideas that quickly show up when searching, and am now considering something like this:

The solar panel voltage is regulated to 5V using a switch mode regulator and fed into the charger and load sharing circuits. The resulting output is regulated to 3.3V for the application. There are two extra optional paths from the battery to the application for battery monitoring and to control the charger. I'm not really sure if I need those, though. This question is very similar, but uses a LiPo cell.

First of all: is that overkill? average current drawn by the MCU is less than one mA, with about 300mA peaks.
The 5V regulator should be able to handle \$V_{SP} < V_{5}\$ (index SP: solar panel) and I migh need a "power good" indicator.
MPPT: Do I need that? I've read that low-power applications don't really benefit from MPPT, but that probably depends on the ratio of charging power/available power. What happens when the required power is less than what is available (high solar radiation, battery fully charged, application in standby)? There's this microchip appnote on MPPT, but it doesn't address that question (if I have understood it sufficiently).
charging algorithm: There seems to be some confusion about which algorithm is "correct" for charging LiFePos, as in this question. Whether or not I go for a specific charger IC, it's important which algorithm I should use. Handling the charging in software is probably not that hard, but I'm not sure about the hardware side of things.
The charger circuit can be a bit "sloppier" than the application circuit, because it will not run off the battery. When solar power is available, I can use it for additional circuitry. This question is related somehow, as it is about implementing MPPT and charging algorithms in S/W.

I'm really not sure if I should pick an available switch mode regulator and charger IC and cobble something together, or if I should try to roll my own circuit. That would certainly be hard, I guess.


texts: How can I evaluate a potentiometer susceptibility to change?

texts:
I have a usage case where I would like a potentiometer for controlling the charge going to a lead-acid battery via a IC. It would be susceptible to some (although not extreme) vibration, such people carrying it around and various bumps.

It would for most part be a set-and-forget thing hidden in a case that nobody will think of, unless the battery type was changed. I don't want the resistance to go shifting over time, it should ideally remain reasonably stable within a few percent.

How can I evaluate if a potentiometer is stable enough to use for this purpose?


texts: Why most appliances in US don't have third prong

texts:
Most other plugs I encountered have three prongs - hot, neutral and ground I assume. For example all BS 1363 plugs have one. Also CEE 7/7 have ground connections and while CEE 7/16 exists it is not used for high-power appliances such as computers.

On the other hand I might have seen once grounded NEMA plug even for computers etc. What reasons are there for those differences (is it due to 120 V vs. 240V)?


texts: It is possible to replay CAN bus messages for building intercom system?

texts:
I would like to automate my apartment's intercom unit to unlock the building door remotely. I am able to press the door unlock button at any time and this unlocks the door in the lobby. I scoured the internet and was able to find the unit as a wholesale in China and the documentation mentions the communication protocol is CANbus.

I took the cover off my video intercom unit and found that there is a single DATA pin which I presume is transmit or maybe a single wire implementation of CAN? Impossible to tell.

I measured the voltage by connecting a multimeter to ground and to the DATA pin. It was 14.5v which seems rather strange. When I press a button I can see the voltage drop slightly.

Are there any tools I could use to see the messages being generated by the intercom unit? Ideally I would like to reverse engineer the CAN messages and then replay them from a WiFi enabled micro controller so I can remotely operate.


texts: Given the fact that the clock frequency is about one GHz and the corresponding wavelength is about the same order of magnitude (velocity of propagation is lower than 3 * 10^8 m/s inside the chip) with chip dimensions, is care taken care of to suppress signal reflections inside the chip?


texts: Why would plugging in a logic probe change values in a digital circuit?

texts:
I teach a digital logic course, in which the students used TTL chips and LEDs on digital trainers (including the Global Specialties PB-503C).  With one student's PB-503C, the values on the lights (both discrete LEDs and the ones built into the kit) change their values when I connect the appropriate wires of a logic probe to its power and ground (without touching the tip to anything).  This happens with multiple logic probes (and a voltmeter, iirc) but not on other students' kits.  Why might this happen?

FWIW, the power supply on the PB-503C seems wonky.  I measured the 5V rail with a voltmeter and got over 6V.  I had the student use an adjustable rail instead.

Updates:

It is a hand-held digital multimeter, not a voltmeter.  I can try an analog one in the future.
The logic probe is not externally powered.  It draws power from the kit.
I could probably get hold of an oscilloscope but am not sure how much I could do with it, since my knowledge is limited to digital electronics.
The power supply is not under much load, just a few dozen TTL chips.
The change to the LEDs is that some that are off go on, and vice versa.  The LEDs have integrated resistors and are connected to the outputs of a pair of LS163 synchronous counters.  The changes to the lights are not regular, as they would be if the clock input were changing.  (The clock is a pushbutton.)
I used a knob-adjustable rail to get 5V (at zero load), but that tended to drift off too and need readjusting.


texts: Safety shields for power supply DC output bus bars

texts: I have seen a variety of optional or included features with power supplies that the manufacturer calls a safety shield. In some cases it is just a 3 sided piece of metal - the back and bottom remain open, such that someone reaching around the back could contact the bus bars. I see how it protects from a short due to a dropped tool, but do not see how that can be considered a safety shield for personnel - perhaps when operated in a rack, but not when operated on a bench top. What criteria would the UL or CSA standards impose for a manufacturer to legitimately call something a safety shield?


texts: mbed LPC1768 with optocoupler for 5 V output

texts:
I am generating a PWM at 20kHz to drive a motor. The signal goes into a motor controller which range is from 0 to 5 volts.

Since the PWM output is 3.2 volts I need to amplify it. For that I am using this optocoupler:

This is the electronic circuit I am using:

The optocouplers are inverted, pin 1 is down-right. The capacitors are 0.1uf as specified in the datasheet and the resistors are 330 ohms.

The optocoupler output is not working, it gives me less than one volt.

I already try supplying the optocouplers Vcc with an external power source, but the result is the same.

simulate this circuit – Schematic created using CircuitLab


texts: direction of current densities for electrons and holes?

texts:
Let's say we have:

\$ J_n = 3 \frac{A}{m^2} \$ and \$ J_p = 2 \frac{A}{m^2} \$

and let's define the direction of positive current (flow of positive charges) to be moving from left to right. Then, would \$ J_n = 3 \frac{A}{m^2} \$ mean that electrons are moving from right to left and \$ J_p = 2 \frac{A}{m^2} \$ mean that holes are moving from left to right?

I just want to make sure if I am understanding the convention right. I hope my question makes sense.


texts: Why would a rotor get stuck on the side of the stator when the induction motor is turned on, and how to fix it?

texts:
My big fan stopped working, so I decided to dismantle it and check what's wrong with it. The problem lies in a faulty induction motor.

I opened it and found out that I can easily turn the rotor inside the stator when the motor is powered off.

Now, as soon as I turn the power on, the rotor get magnetically stuck on one side of the stator. I'm not exactly sure it's always on the same side (I've tried many times).

I checked if one of the 4 coils was not functional using a dangling screwdriver, and it appears all the sides of the rotor get magnetized when powered on.

Would you have an idea of what's going on (and how to fix it)?


texts:
I am trying to build simple voltage monitoring relay.I have ckt that goes to micro-controller pin. can some one suggest me ckt where i can power MC with isolated gnd. i would like to add L78M05 regulator drive from any one of phase.
weather it safe?
i dont prefer to use transformer based power supply.
I have seen some of design using capacitor and Resistor Network weather it has protection???

simulate this circuit – Schematic created using CircuitLab


texts: I lost the power supply for my drumbrute, the manual doesn't have clear specifications of what the DC power supply is. But the back of my device says it takes a 12v 1a DC adapter. Would any 12v 1a DC adapter work for this device or is there some sort of hidden caveat? Does the mA of a power supply affect how it can work with my device?


texts:
I have an electrical engineering academic background, but since graduation, I have worked exclusively in software and my EE skills are admittedly getting very rusty. Something I never fully understood was circuit analysis with transformers.

I understand, at the simplest level and with an ideal transformer, that the V/I ratio changes such that V1/V2 = I2/I1 and power of the primary should equal power of the secondary.

What I don't understand is that this can happen without violating Ohm's Law.

For example, what happens in this case:
I have a transformer that has 10 A running through the primary with 200 V across it.  On the secondary, I connect a 10kOhm load.

If the secondary has double the windings of the primary, then I should have 400V and 5 A on the secondary.. but how is this possible considering I have a 10kOhm load on the secondary? It seems as though I should be able to calculate the load from my Vs and Is, despite the fact that I could attach any arbitrary load there.
How is this accounted for by equation (6) on Wikipedia (http://en.wikipedia.org/wiki/Transformer)

The second part of this question: What is a reasonable circuit model of a "real" transformer, and would circuit analysis (solving for currents and voltages) using the model answer the question I have above (about violating Ohm's Law)?
I do see a circuit model on the Wikipedia article, but it doesn't appear to answer my question at all. The secondary is just an open circuit with a calculated potential across its terminals and the transformer itself.


texts: BJT Mode of operation when VBE = VBE(ON)

texts: I know that, for a BJT, when VBE < VBE(ON) the transistor is in cut-off, and when VBE > VBE(ON) the transistor is either in linear of forward active depending on VCE, but what about when VBE = VBE(ON)?


texts: What is being depicted in these piezoelectricity circuit diagrams?

texts:
I am currently studying Ultrasonic transducers – Materials and design for sensors, actuators and medical applications by Kentaro Nakamura. Chapter 1.2.2 Piezoelectricity says the following:

Piezoelectricity means electricity derived from pressure (Moulson and Herbert, 2003: 339-410). Thus, the direct piezoelectric effect, defined by the Curie brothers and illustrated in Fig. 1.4(a), is the generation of electricity from pressure, and the converse piezoelectric effect is the generation of pressure from electricity, shown in Fig. 1.4(b).

I'm a novice to electronics, so I'm not totally sure what's being depicted in these circuit diagrams of figure 1.4. I know that the circles with the positive and negative ends are voltage sources, and I know that \$P\$ is the polarisation. So what is being depicted in these circuit diagrams of figure 1.4


texts:
The question in my textbook was:

Design and implement a Serial 2’s Complementer with a Shift Register and
a flip–flop. The binary number is shifted out from one side and it’s
2’s complement shifted into the other side of the shift register.

I got the solution but I was curious to know the Verilog implementation of it. How do I do that?

This is the solution.
EDIT: my actual circuit diagram.


texts: What scheme would you indicate for a nobreak system with variable frequency output?

texts:
I'm pretending to make a system that charge batteries (or a single battery) and then produces 3 independent AC outputs (all having the same common, in a star connection).
But I want to have independent control of the frequency, (relative) phase angle and voltage of each output, as the intention isn't necessarily to feed a 3-phase motor. For instance, I wish to be able to completely turn off one of the outputs and produce just 2 phases in 90 º if I want.
Or put all the outputs in phase and parallel them to have a higher current single-phase output.
I guess that the outputs will be driven by 3 independent PWM circuits which I'll control with a micro-controller, but that isn't my question right now.
My question is what is the best scheme for the conversions needed, from the AC network to the AC outputs.
I guess that the cheapest and most practical solution for the battery side is using a 24 V 20 A power source with a current regulation circuit to charge a car battery.
The problem is what I do after that. Should I use an inverter to step up those 12 V to 300 V (for example), rectify and filter that to 300 V DC and then use the PWM circuits with those 300 V (with their output directly feeding the loads)?
Is there another better scheme for all of that?
Thanks!


texts: Are bypass caps reason why uC don't have flyback diode across ferrite bead in the sample schematics?

texts:
Often the IC datasheet recommends putting a ferrite bead before AVCC pin. First I started wondering if I don't need a flyback diode but than I realized that capacitor is probably able to absorb the excess current.

For back of the napkin calculations I assumed that ferrite bead is an inductor so total energy stored before switching off is \$ CV_0^2 + LI^2 \$.

When the power is cut off all energy needs to be stored in capacitor so energy now is \$ CV_1^2 \$.

So if I want the voltage not to be above some \$V_t\$ I need to have capacitance of:

$$ C_{min} = \frac{LI^2}{V_t^2 - V_0^2} $$

So assuming \$L = \frac{X}{2 \pi f}\$, \$300\,\Omega\ @\ 100\,\mathrm{MHz}\$ ferrite bead, \$I = 20\,\mathrm{mA}\$, \$ V_t = 5\,\mathrm{V}\$, \$ V_0 = 3.3\, \mathrm{V}\$ it gives \$C_{min} \approx 14\,pF\$. Other way round standard \$ C = 0.1\ \mu\mathrm{F}\$ capacitor gives swing of \$0.3\,\mathrm{mV}\$.

Is this reasoning correct? I've made a few spherical cow assumptions and I'm just a beginner.


texts: What is the difference between Codevision AVR C and Atmel AVR C compiler?


texts: How to know the speed and energy of a particular Digital Design in Quartus-II and DE1-SOC FPGA (Altera)

texts:
I did a digital design in Quartus II and my board DE1-SOC FPGA, now I want to read 3 factors: general speed that digital design takes to finish the application, area of the design if it would be a real chip, or at least the area taken in the FPGA, and lastly Power, I wish to have a estimation of the power utilized by my design.

This is to compare with another design made by a schoolmate.

How can I achieve this EASILY by using tools in Quartus.

Power Estimator is available in Quartus 2, but what about SPEED?

PD: As a homework, my design pick up a list of 57.600 8 bits binary numbers (.mif), one by one, pass it through some arithmetic and output 3 sets of 57.600 8 bits binary numbers in ON-Chip RAM. Actually I don't have any proposed constraints, or frequency to achieve, I only expect it to be "standard".

I wish to read any kind of simple estimation of power, area and speed.


texts: Does current in neutral wire flow like this?

texts:
I've read neutral wire in 1 phase AC at home has almost 0V at both ends. But still current flows through it. So I've assumed 0.1V potential at the other end near a resistance (bulb). Now there's a potential difference (110V - 0.1V) so current will flow, bulb will be lit, current will return from 0.1V to 0V of Earth (the end inside Earth surface like soil, highlighted by arrow).

And in case the voltage becomes negative, I. E.,  - 110V, the voltage of end inside Earth still has 0V, but the other end will have -0.1V So current will reverse the direction from 0V to - 0.1V to - 110V.

In both cases, neutral wire has very less potential difference.

Is it somewhat like this or I am misunderstanding something?

The question that claims here to be original of this question, isn't actually original of this. The answers there focus mainly on difference between Wire 3 (Earthing) and wire 2 (Neutral). I haven't asked anything about wire 3 so far and it is not related to my question so far. My question is to understand the working of neutral wire in 1 phase AC and direction of flow of current from red to blue and blue to red wire.


texts: Microcontroller/cpu for fast trigonometry in robot?

texts:
This concerns hardware that does weighs little, because a (fat cat sized, 6 legs with 3 DOF) walking robot should carry it around. Because of that walking it'll need to do a lot of trigonometry (using matrix math or not i'm not sure yet) and this is where this question comes from.

PIC, Arduino or cheap AVR is not fast enough to calculate everything 100/second and keep things like inertia and obstacle avoidance in mind, or even bruteforce paths/gaits.

Plan A is to carry the brain on the robot.
Be it microprocessor, micro ITX, nettop or other; what is efficient hardware to do trigonometry / matrix math fast?

I searched online and expected to find out about AVR, x86, or ARM
microcontrollers specialized in this but no luck there.
Plan B is to have a x86 machine connected via WiFi to do the heavy
lifting. Great for prototyping also, but i'd like this to migrate to
plan A eventually when the hardware miniaturizes. But even then, what
desktop CPU can do trigonometry the fastest?
Plan C is to distribute the load and have one power efficient microcontroller/core for each leg, although that is not the best solution for many reasons i like the extend-ability of it.

I have not decided on the language and/or library used yet, but prefer Pascal and C++.

(suggestions for more suitable tags welcome, i am new here)


texts: Protecting circuit input against lightning - how to put all the pieces together?

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I am designing a single wire (ground return) telephone for use in our hobby caving expeditions, starting out from  a well known and successful design called Michiephone (http://speleonics.com.au/business/michiephones/images/mph_schem2.jpg).
Here is my input stage:

It is essentially a high input impedance voltage follower with an extra passband active filter. The telephones are powered from a single lithium ion cell, so in normal circumstances we expect not much more than 4.2 Vpp on the line...
Now very often the comm line would run from a tent camp on the surface to an underground camp in the cave - meaning that some few hundred meters of wire are in fact over the ground and exposed to elements. So I thought it would be great to add some basic surge/lightning protection to the circuit, since otherwise it might not survive even the mildest thunderstorm (... and we are exploring caves in the Alps, which means thunderstorms are frequent).
There is already some good material on the subject here on Stack Exchange. I read this and this and already know the building blocks of a lightning protection circuit: gas discharge tubes, varistors, TVS diodes, trisils, integrated TBUs. However it seems to me it is imperative that they are used together in a proper combination. And designing a good suppression network is where the challenge starts, especially for a designer like me (rated for 5V/100 mA).
Here is what I came with so far:

I selected the components reasoning as follows:

The main energy absorbing element would be the GDT. The lowest sparkover voltage available seems to be 75 V (looking for example at this Bourns datasheet)
The GDT takes time to switch on. Both this time and the voltage at which it switches on really depend on the surge profile. So I add a Trisil triac to clamp the surge voltage before the GDT turns on - or in case the GDT thing does not turn at all. I reckon the Trisil should be rated for a voltage exceeding the GDT sparkover voltage, say 120V (or is that too low?).
Now, 120V is still a bit high. So I add a TVS diode array with a breakdown voltage of 6 V and a clamping voltage of some 18 V. And I just hope the input capacitor of the input stage holds. For a brief while these 18 V might be fine for the rest of the circuit - it takes a while to charge capacitors in the input stage through a 47k resistor, so I might hope these 18 V do not reach the IC at all.
If I clamp the GDT/Trisil voltage to 18 V, it will prevent these parts from tripping. And that could quickly fry the diode array. So I add some reasonable amount of inductance between the diode and the GDT. And a wire-wound resistor to limit the current through the diode.

The question is: does this reasoning and the design make any sense?
There is a lot of information available online on many different transient/surge/lightning protection devices. But how do you - in general - connect all the building blocks?
I already ruled out MOVs in my application. Adding some 10 nF of capacitance to the circuit input kills its high impedance - which is the very idea of a single wire (earth return) telephone. Also the TBUs from Bourns may be a nice, integrated solution, however they come in DFN packages, which are rather difficult to solder in hobby designs.


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I'm experimenting with HID lately. And I need to know more about the physical output signal of a USB keyboard. My goal in the end is to put a small data logger in between the USB-keyboard an a computer and capture all the signals which come through. Afterwards I want to try to decode the records again.
Once I accomplished this (if it is even possible) I want to do this with other USB Devices, such like web cam, mouse, maybe even printer... I know that it isn't easy with USB and I'm also a complete newbie to this topic. But I want to give it a try.

So in my first step I want to 'record' the physical signals with a logic analyzer and afterwards i want to replay the signal back to the host.
Do you think this is possible?


texts: VHDL: Port mapping to physical pins when you have "subcomponents" inside a component

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Let's say you have a project in VHDL that looks something like this:

Generally it's pretty easy to map the ports together between Component 1 and Component 2. However, what if Component 1 is code from another VHDL project that you created earlier, such as a binary to seven segment decoder, which also contains components inside it that has been port mapped together as well. Then how do you Integrate Component 1 into the final project (the Top Module) and map it together with Component 2, when Component 1 already contains components that has been mapped together?

Could someone provide an example?


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I need your help because I do not know much about electromagnetics.

I use Arduino UNO for control blinking LED(Cree CXA 1512 18v) fast(< 100KHz).
Until now, i have used following circuit.

simulate this circuit – Schematic created using CircuitLab

My project is changing micro controller Uno to RPI 3.
However, If i just change it, circuit doesn't work.
I think that the reason is RPi's GPIO output voltage is 3.3v.
(And Arduino Uno is 5v, right?)

Why this circuit doesn't work?
So what should I do to make the circuit work with the RPI?
I think i should change the MOSFET, do you have any product to recommend?
And there are any other problems? (such as safety? I always afraid about electric shock....)


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Let me start by stating that I am a student with very little experience so I am starting at square one, so please bear with me.

Requirements

I am looking to create a local positioning system between 1 transmitters and N receivers (3-6 most likely). This is in a outdoor space about 10m x 10m and I only care about 2D location. I would like accuracy to be within 0.2m or so. The area will be very flat and open and the only disturbance will be the sound of a small engine. The transmitter will be moving with the receivers remaining stationary (that's how I imagine it anyways). The inherent design of the systems requires the transmitter to be moving very slowly, roughly walking speed or slower.

Current Idea

Given my accuracy limitations GPS is out of the question, and given the idea of a moving transmitter I decided an IR sensor would not give me the multiple directions for multiple receivers I require. After all this I decided an ultrasonic sensor would most likely give me the result I require. As you can probably tell I'm still stuck in the design phase and want to solidify an idea that would give me closet to the desired results.

Question

Am I correct in thinking that I can use a combination of ultrasonic transmitters/receivers to triangulate the location of the moving transmitter? Is there possibly a better system for what I'm trying to do?

I wish I could bring more technical questions to the table, but the more technical information I look up the more I realize I need to understand the fundamentals of what I am trying to accomplish first.  I have very little practical information, so even links to readings or videos would be greatly appreciated.


texts: How exactly are radio waves produced from a current in a circuit itself?

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I am 17, and I am new to electronics, and I've learned everything online and expect to continue to do so with all the resources. I have dug around and can't find concise answers on this question ...

How exactly are radio waves propagated, and how can I build a simple circuit pair from which one can send the radio waves and the other can intercept them?

I have read different things in different sources, and I'll link them all here:

1.http://www.nrao.edu/index.php/learn/radioastronomy/radiowaves

The aforementioned site claims that radio waves are essentially EM (knew that), but mentions photons. Photons are the essence of all EM, but in a simple circuit there is just current flows by the battery. How would I produce photons from a one-way current?

2.http://www.qrg.northwestern.edu/projects/vss/docs%20/Communications/3-how-do-you-make-a-radio-wave.html

That site above claims that you can "make a radio wave" simply by having an electric field, which is an electric circuit. So, by that logic, any electric circuit is producing radio waves as is? In that case, a homopolar motor would technically produce radio waves as well(it is a complete circuit, yes)? So then the radio waves will propagate in a pattern depending on how many times the circuit goes on and off, so I could encode data by patterns just by removing and placing the battery back to the circuit? I don't get it. Can anyone clarify that article more?

What I wanna do is make two simple circuits out of copper, and produce a radio wave that the other circuit will intercept and use an AND-gate to turn on an LED wirelessly.

However, I do not understand exactly how radio waves are propagated!


texts: What is the difference between an analogue multiplexer and digital multiplexer?

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As far as I know, analogue multiplexing is used to take voltage samples from many channels in a short time. It passes the voltages from an input to the ADC without amplifying them. I guess buffer them?

But is that called analogue because of the inner circuitry or because of its operation? And what is a digital multiplexer used for?


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[Edit: revised my complete post]

I have a problem with a project I'm currently working on, and I would really appreciate some help.

I created 10pcs of 100W RGB LED modules that are communicating via DMX512. Already two times now, my MAX485 transceiver IC's have blown out on several different units. It happens on either power on, or power off (can't tell the difference), but never DURING operation. Most MAX485's blown end up with their A or B input connected to GND or VCC. Some don't short out, but simply stop receiving. Anyway, the problem seems to be coming from the RS485 side of the chip (although I'm not 100% sure).

Now I've optained the MAX485 cheap on Ebay, and I'm starting to think they might be fake or flawed. But I'm not sure about that. My plan is to replace them with real SN75176AP transceivers, that I can order from a reputable company. (The SN75176AP is more cheap than the MAX485, and I heard also more rugged). But before I do, I wonder if I've overlooked some error in my schematic that causes them to blow. Hence my first question here on the forum :-). Below is the schematic: (part numbers might be different from the ones mentioned in the comments)

All 10 units are powered by the same transformer, with soft-start relay that closes automatically after 10 seconds.
The transformer is a 28-29VAC, 40A (heavy) 'old-fashioned' transformer. This leads to about 40VDC after rectification.

Then the schematic of one unit. There are ten of these in total, all connected to the same transformer.

Power: LM2596 is a switching regulator that can handle 40V on the input

Logic:

LED drivers an FAN:

Old situation with R18 still in, and unidirectional D10&D11 (7V working voltage suppressor diodes). R18 was based upon this article Page 19 - 4.5.2.

New desired situation with R18 taken out and 12V bidirectional suppressor diodes (untested).

The DMX controller looks like this: (Vcc comes straight from a 5V, 1A wall-wart SMPS)

My main concerns are:

C1-C9 are 9x 1mF capacitors. Because there are 9 of them, they have a very low ESR. Combined with 20m of wiring going to these modules, what about inductance. Could that create a pulse destroying my MAX485's? Even with D1 and soft start in place?
My theory at the moment is that the (fake?) Ebay MAX485's can't handle RS485 signal being present on the line while not being powered. Sometimes my DMX controller is on, and the transformer is off. This should not be a problem according to the datasheet, but if they are fake, it might be?
If I omit R18 (previously R2,R3 - sorry about the different numbering), what about large currents through my DMX GND line, as there are 10 of these units with the GND's connected to each other in this situation. Maybe I need just ONE bridge rectifier near my transformer, and take out the ones in the units? But I'd need a 40A bridge - if it's not nessecary I'd rather keep things as they are.
AND MOSTLY: Do you see any reason why the MAX485 could blow out?

(This is a working prototype. So apart from the MAX485 blowing out every now and then, everything works. Also the DMX communication. My question is really focused on why does the MAX485 blow out. If there's no real reason, I'd like to think it's because they are fake Ebay ones, and try real SN75176AP's. Making big changes at this stage of development will involve lots of work as the modules are already finished and ready to be used. So I'd like to prevent big changes as much as possible.)

Thank you so much for your help. Also to the ones already commenting and answering. Great!


texts: How much variability is there in a solar panel?

texts: If I have two solar panels with identical specifications and they are working under the same condition, how much difference in power output would usually be observed?


texts: A circuit to convert some resistance values to others

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I'm looking to build a circuit to convert an old steering wheel remote to a newer head unit. Both work with resistances, but have different values each.

So, what I would need to build is a circuit that, given an input resistance value, outputs another resistance value.

I don't have much experience with advanced electronics, so what I'm looking to know is whether and how this could be made with more simple electronics (resistors, transistors and so on) or if I'd need to use things like micro-controllers (for which I don't have any experience at all).

Could you give me some orientation in this matter? Thanks!

Edit: The steering wheel provides input with 2 wires. Pressing a switch closes the circuit with a determined resistance value. The head unit / output circuit expects this kind of behaviour, albeit with different values. There are adapters, but not for my specific remote.


texts: Why does Miller approximation method give the wrong result here?

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Does anyone know why using Miller approximation method to calculate the input impedance gives the wrong result here?
The right answer is 1/gm.
I know how to use small signal model and calculate input impedance from that. However, for this question I'm trying to use Miller approximation method convert the feedback resistor Zf into two grounded resistors Z1 and Z2.


texts: Location of boot button in PIC microcontroller board

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I am learning about microcontrollers in school now and I was looking at the schematics of the microcontroller board that we use in the lab and came across the boot switch and the reset switch. The positioning of the reset switch and the boot swicth can be found in the schematic below.

My question is why is the boot switch located at Pin 37 instead of being located at say Vdd? [pin diagram below]

And, if I am looking to add a boot switch to other PICs (maybe PIC10F200), where do I add it?


texts: Question about the Texas Instruments LMH6881 programmable gain amplifier

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I want to use a PGA (programmable gain amplifier). I found the LMH6881 which I will be probably using.
On page 5 of the datasheet you can see that the analog input voltage range should be between 0V and VCC (which is 5V). On page 6 of the datasheet it is stated that the input common mode voltage is 2.5V (self-biased).
So why isn't it possible to apply a single-ended -2.5V signal to the analog input. If it is self-biased then it should still be in the range of 0V to 5V, right?


texts: Different antenna lengths for different frequencies?

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I just want to understand a few things which I couldn't get clarity from a lot of websites searched through google as I could see differing information.

My questions :

How does a single FM antenna length works in the entire FM frequency band range, when there are theories which state that the antenna size should always be close to wavelength/4 for proper reception & transmission?

For example :
The FM frequency band ranges from 88MHz to 108MHz. How will an FM antenna length will match all the frequencies from 88MHz to 108MHz? Does the antenna length scale itself within that range or how does it work?

Why does low frequency signal have high range but high frequency does not?


texts:
simulate this circuit – Schematic created using CircuitLab

original schematic

I tried to give my lcd screen 12v in arduino but this connection burned the arduino. Is there anything wrong with connections?


texts: Through Hole Soldering- Minimum lead protrusion

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I am working on a bit of a strange design: all components, SMD and Through-Hole, are mounted on the top side of the PCB, except for some really beefy MOSFETs, which are mounted to the bottom side of the board. The idea is to have a flat heatsink (like the ones meant for BGAs, with push pins) cover the whole bottom of the board, making as direct a contact to the MOSFETS as possible. The MOSFETs use IR's DirectFET packaging, which is about 0.5mm thick, so the heatsink will sit quite close to the surface of the board.
This leads to my problem: For obvious reasons I do not want leads from my through-hole components shorting to the metal surface of the heatsink, and I don't want to be drilling clearance holes in it. Is there anything preventing me from just cutting the leads flush before soldering?
I notice NASA's guidelines require at least 0.5mm of protrusion, and from what I've heard IPC requires leads to be "visible". I imagine this makes wave soldering more reliable, but assuming I am hand soldering the components and am careful to allow the solder to wick all the way through the PTH, are there any other disadvantages to cutting the leads flush (things like reduced mechanical strength, etc)?
EDIT: the thru-hole components are "can"-style caps, and terminal blocks, so they'll need to be soldered from the bottom.
(Probably unimportant) details: The MOSFETs should only put out 15-20 watts of heat combined, at absolute most, plus a watt or two from some large thermal pads. So I want to leave it an option for the user to remove the heatsink and mount the board directly to a metal chassis, with some sort of thin thermal pad to avoid shorting. So that's another reason why I don't want to drill clearance holes in the heatsink, for user convenience.
EDIT: board pics for clarity:

(If you're wondering about missing traces, it's a 4-layer board)


texts: How to Remove Ghost Duplicate Pins in Circuit Appearance

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One of my subcircuits I designed for some reason has more pins in the circuit appearance than it has in the circuit itself. In the actual subcircuit, there are 47 pins, which is the correct amount. I took the picture while moving all the pins to show that none are unselected
Now when I go to modify the circuit appearance, it shows that I have 51 pins. 4 more than I actually have.

Some of my pins are for some reason duplicated. At least I assume so. I found 2 pins that are leading to almost the same exact spot. One leads to the actual pin:, and one that leads to where the pin used to be located a while ago:
This is the view from inside the circuit:  As you can tell, there isn't a pin where it says there is. And when I'm using the subcircuit, either both of them have the same label, or neither of them have a label. Putting an input onto the pins does nothing. The pins are progressively duplicating. At one point, I only had one duplicate. Now, I have 4. I have no idea what's creating these, where they're leading to, or how to delete them. I could likely use the circuit just find by storing them all in one spot that won't be used, but I'd rather just delete them. How can I get rid of these, or am I going to have to just have them exist?


texts: Level shifting 3.3V to 5V for PWM output to servo

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I am currently trying to control a simple servo motor using PWM generated by a MCU with a 3.3V output voltage.
However, this servo works with 5V, so I need an IC capable of "converting a 3.3V PWM to 5V". My question is: What are the pros/cons of level shifting an ouput between the 3 methods:

using a MOSFET
using an optocoupler
using a simple 4.7k pull-up to 5V with output of the MCU being open drain.

Many thanks,
Duarte


texts: What is the difference between an alternator and a generator?

texts: What is the difference between an alternator and a generator ?


texts: Single-package DC/DC converters for PoE -- good idea?

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I'm planning a design where we'll use PoE to power a data acquisition board (essentially, an ADC + microcontroller + ethernet PHY and interface).

I look at DC/DC isolated converters to get the 5V or 3.3V from the, say 48V from the PoE wires, and I get a headache!  I look at two reference designs (from TI and from Analog Devices / LT), and they have a components count of about 50 parts !!!!   The Art of Electronics (3rd Edition), on Figure 9.83 show a "real world" example of a switching converter (in that case, it is AC/DC, but same principle), with approx. 40 parts, and they say that that is a "relatively uncomplicated" circuit .....

On the other hand, I see single-package DC/DC converters such as the CUI PDQ10-Q48-S_X_ — 1-inch by 1-inch by 10mm height, 10W, input DC between 18V and 75V.  I don't see why something like this would not work.  Any comments?

As a secondary question:  I guess I will at least want to put the recommended EMI input filter (C-L-C, as per datasheet suggested circuit), and some TVS (say, a 60V or 70V Zener TVS?) just after the output of the rectifier bridge from the ethernet isolation transformers?   Any other aspects I need to pay attention to?


texts: Appropriate base resistor for BJT switch driving a motor

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In the following circuit, the BJT is used as a switch, controlled by in. The load is a motor. I've added a few diodes for safety, as recommended here; you can safely ignore them.

simulate this circuit – Schematic created using CircuitLab

in is connected to a digital pin of Arduino, so the voltage is 5V when high, and the current should not exceed 40mA.

My motor's input voltage is 12V, and its rated current is 0.45A. I think it yields a maximum resistance of 26.67Ω. I'm using this figure to model the load resistance.

Based on these, I'm explaining my approach, to show what have and haven't I considered. When in is high as 5V, the BJT should be saturated. The spec. of 2N2222 says \$\rm V_{be(sat)}\$ is:

1.3V at \$\rm I_C\$=150 mA, \$\rm I_B\$=15 mA
2.6V at \$\rm I_C\$=500 mA, \$\rm I_B\$=50 mA

Since I'm looking for about 450mA, I'll just take \$\rm V_B\$=2.6V. Now the volt. diff. across the base resistor becomes 2.4V. By Arduino's 40 mA limit, I see the resistance must be ≥ 60Ω.

By deciding \$\rm I_B\$, I would be able to decide the appropriate resistance. But I'm perfectly stuck here. I've seen some articles saying "take β≒10 for saturation", but I'm confused since \$\rm I_C\$ does not increase while \$\rm I_B\$ increase there, so doesn't β vary?

As Vcc is fixed to 12V, the equation \$\rm V_C+I_C \cdot R_{load} = 12\:V\$ draws a line in Ic vs. Vce plot. Does it help?


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I'm trying to simulate an hysteresis on LTspice. The goal is just to see how evolve the output voltage in function of the value of the thermistor. For this, I have done a simulation with several steps. Each step corresponds to a temperature and as the thermistor evolves in function of the temperature, the non inverting input voltage of the op amp varies in function of the actual step.
Here is the simulation :

My problem is that I am not able to see the hysteresis as the output voltage does not depend on the previous step. So I am always beginning the hysteresis in the same way. The ouput voltage is always the same at the beginning of a step. I would like to define the output voltage in function if the temperature goes up or if the temperature goes down. In other word if the non inverting input voltage goes up or goes down.
Thank you very much and have a nice day.


texts: Li-ion swappable 18650 in parallel - preventing mixing charged&discharged cells

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I'm designing a device that has 6 18650 elements (all parallel) in holders, made so that the end user will be able to pop out the batteries when they're discharged and plug in a set of new batteries. It's possible to put in 4 charged batteries when 2 discharged remain inside (the device is like 2-layer box with lids at top and bottom, having 4 cells in the top compartment and 2 cells + electronics in the bottom one, so the user has to open both to change the batteries), therefore allowing the charged batteries to charge the discharged ones, which AFAIK is a disaster because of high currents.

To protect the device (and the user) against this, can I just put a resettable PTC fuse between the 4-cell compartment negative terminal wire and 2-cell compartment negative wire? I'm not thinking about the scenario where the user mixes charged and non-charged batteries in the same compartment.
Also, if the fuse approach is conceptually right, will there be any drawback to using the resettable fuse, t.i. would a regular non-resettable fuse perform substantially better in terms of safety?


texts: My question is rather simple, when and why do one use a 1-pole or 2-pole circuit breaker in DC (+24VDC and GND)?


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Is there any efficient way to make an antenna radiate to the outside from inside a close metalic enclosure?
I cannot drill any holes in it, nor place the antenna on the outside, nor change the material type.

I know that the metal acts as a shield and reflector for the radio waves. I was thinking on using a directive antenna and hope that the radio waves find their way out/in somehow, maybe through some open edges.
This seems like some sort of impossible task, you have any alternatives to it?

I'm working over the GSM band.

Regards


texts: How to wire multiple 2 volt flickering LEDs to work on 12V auto system

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I have tried to use the site to find an answer to this, but it seems everyone that has asked questions have different variables than I am dealing with, and I can't ever seem to grasp electrical concepts or formulas.  I even tried the automatic calculators, but they show only one resistor, and the articles I find here say one is required for each LED.

I wish to make two flickering LED lit panels to simulate a wood or coal burning type display that will be used in a 12 volt motorcycle system.  Each panel will have five individual orange LEDs and five individual yellow LEDs, shining against a small white plastic panel.  There will be two panels on one switched circuit.

The LED specs are:

Size: 5mm
Animation:  Flickering (irregular) like artificial candles
Source voltage (motorcycle battery): 12V
LED Forward Voltage (Orange):   1.9V to 2.1V
LED Forward Voltage (Yellow):   1.8v to 2.2v
Current per LED (both colors):  20mA

I need to know the best way to wire these, (series or parallel) or and what value of resistor to use, and how many.


texts: Given a load, how do you calculate whether it is capacitive or inductive?

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If the impedance at the load has the form of \$Z = R + jX\$, where \$R\$ and \$X\$ are positive real numbers, then then network is called inductive. If \$Z = R - jX\$, then the network is called capacitive.

Why is this the case and what do we do when there is both capacitance and inductance present at the load (i.e. \$RLC\$ network)?


texts: Understanding thermocouple transmitter wiring

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I'm trying to use the RMTJ40BD thermocouple (page 12) and I'm having trouble understanding the wiring diagram for the output.

The manual says that Vo and OPG are the outputs but what is OPG, what does the line through Vo and OPG mean and what does the circle with an attachment to ground mean?


texts: How much current used in 20 LEDs circuit?

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If I have 20 LEDs (red) and I want to connect it in parallel and series.
Which circuit need more current? and how much?

*And what happen if I use a source that can provide current both less than and more than the circuit need?
Thank you ^^


texts: Whether a battery is a constant voltage source or current source

texts: is battery is a constant voltage source or constant current source?if it is a voltage source then why the voltage gets dropped?if it is a current source?is really the battery is providing electrons to the conductor?


texts: Are there electronic devices that can be used to replace hydraulic cylinders with short strokes

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We use hydraulic cylinders in many applications to release brakes and clamp things. The choice of hydraulics is based on them being strong relative to their size. There are a couple of downsides with hydraulics though:

Expensive cumbersome installation, sealings, long (expensive) holes as channels, hoses.
Expensive drive unit that requires maintenance

I was inspired by this thread, where a solenoid was suggested. The problem is that my knowledge about electronics is very limited so I thought I should ask for suggestions here first.

Example of hydraulic cylinder

Ø22 mm (outer), length 38 mm
Force ~3 kN at 250 bar
For stroke ~1 mm will often be sufficient

Operation
We have tow scenarios where we use hydraulics:

For releasing brakes. The breaks are used for security when we have vertical loads. The brake is actuated by spring force but when the drive is powered up the brake is released by applying the force from the hydraulic cylinders.
For clamping tools. Normally the tools are clamped by spring force and released with force from the hydraulic cylinder when a new tool is mounted.

Both applications are very similar to the clutch in a car.

Normally there will be only a couple of actuations per hour
It is a simple motion no need for controlled acceleration/deceleration. Being able to limit the speed would be good for soft operation.
I'm not even sure there is a need for a sensing feedback mechanism
Regarding operation lifetime it is similar to the clutch in a car, it would be ideal to get 15 years of maintenance free operation

I struggled with trying to write this in English, please don't hesitate to as for clarification if something is missing or just strange/wrong.


texts: how do I control duty cycle of a MOSFET using PI controller

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I have designed a buck boost converter, how can I use a PI controller which will automatically change the duty cycle of the mosfet as per my desired output voltage or current?
I have been fidgeting with the PID controller in simulink and have found a way to get my desired load current.I have used a signal generator to produce a square wave which is compared with the actual load current(which is negative and I'm using a negative feedback so it becomes positive, what?) and a Proportional controller of gain=5,I=D=0, the output of which is given to gate. I came to the conclusion that the load current is always equal to the amplitude of the square wave so can we can control it by changing amplitude of the square wave. Is this method credible? Honestly I don't really understand what's going on. Please take a look at the second picture


texts: Protecting handmade electronics from accidental water spillings

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Keep in mind that I dont know the least about electronics. I have soldered and used some arduinos before, but that is it.

I am preparing to make a mechanical keyboard (or handwire like they say on /r/mk) and the common solution for registering keys is a diode matrix, which will be connected to a teensy board, under a custom-designed aluminum case.

But how can one protect this kind of structure from spillings ?
What component, precisely, is vulnerable to water ? Pcbs are is'nt it ? so this mainly applies to the teensy ?

If that is true, would encasing the teensy solve the problem ?

Maybe water would make some component rust, like the case, or the diodes' anodes and cathodes.(Though aluminum should not be damaged by some water i guess)

That makes me realise there should be plural types of damages occasioned, so what other damages would a water or a coffee spilling do on my keyboard, and how can i protect it ? and of course, how much would it cost ?


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I am trying to understand the difference between MOSFET and BJT's.
In particular I am considering the following switch circuit:

My understanding is as following : The \$V_{\text{Th}} = 2.2V\$ for the MOSFET. Since we apply a voltage of 3V we have \$V_{GS} > V_{\text{Th}}\$. However current in the drain is (at most) 5mA (since we can't pull the voltage of drain source below ground), so this means that \$V_{DS}\$ cannot be greater than \$V_{GS} - V_{\text{Th}}\$ as otherwise the drain current would have to be larger than 5mA (something proportional to \$C (V_{\text{GS}} - V_{\text{Th}})^2\$ with a large \$C\$).  So this means that \$V_{DS}\$ is small, and looking at the precise equation we can figure out \$V_{DS}\$ from

with \$I_{D} = 5\text{mA}\$.
Is my reasoning correct? If it is then I understand that in this regime of operation the MOSFET is quite similar to the BJT with the main difference that the base doesn't source current and moreover that the drain and the source can swap roles (if drain is more negative than the source for instance).


texts:
Please help identify this component. It is cylindrical, with an axial configuration, and no obvious indication of which end is which. The writing on it is:
K25U
104M
50V
8502

The 104M makes me think it is a 0.1 uF capacitor, but, in my extremely limited experience, this is an unusual form factor for a capacitor. My googling for images of similar looking capacitors has turned up nothing.


texts: Unstable voltage output for strain gauge application

texts:
I am doing a half bridge strain gauge application and it is connect to INA125P and with gain about 185 with Rg 330 ohm.below is my theoretical circuit diagram, my circuit is base on this picture to connect.

This circuit will connect to arduino uno for take the result.
below is the result from the adruino.

base on the graph above above to saw that the voltage output is very unstable, this cause my unable to take accurate result.

My question is:
-the output voltage will fluctuate like this is that because of the unstable Wheatstone bridge? i am using 120 ohm resistor and with 5% tolerance.
-is that any way to let the output voltage more stable?
-i using this application for measuring low weight object (0 - 10g)
-is that anyway to increase the sensitivity of the application to able to measure object with 10mg.

Thank you


texts:
Let's suppose we have a three phase rectifier like here:

https://www.youtube.com/watch?v=V6ZWYFTELQA

Now lets suppose we change diodes with transistors. Let's also put current probes on each of the three phases. Now we know exactly in which direction the current is flowing in each of the phases. Knowing this, what is the algorithm for opening/closing transistors, to keep the same operation as before with diodes?


texts: Why did this very simple external power source switch circuit fry my ESP32/Arduino board?

texts:
So all i wanted to do was to control a 12V motor through a big spare transistor i had lying around. So i thought it may work and tested the transistor, and indeed it worked as a switch, when feeding a small voltage into the base, the switch activated with the power of 12V... Awesome!
So i thought heck let's skip the breadboard and actually create a real pcb circuit. So i powered all with 12V powersupply. Used a voltage divider with resistors to use same 12V powersupply to also power the ESP32 board(5V) itself. And then come the time where i placed the GPIO pin to the base of transistor to activate the switch... And just like that the board was FRIED. Foolish enough i grabbed another ESP32, tried again and you guessed it fried that one also XD.
So what went wrong here? How did the 12V external power supply manage to get inside the board and wreak havoc? Do i maybe need some diodes or something else that i am missing here :/

Thanks before hand if you can be of any help to make my brain understand a little bit more about electronics :D
-Update! Burned a third ESP32(this time i was clumpsy, accidently fell over the powersupply and shorted it XD)... But my transistor was a PNP transistor and the powersupply in the sketch i drew was drawn in opposite direction!


texts: Sharing data in two different always @(posedge ...) blocks

texts:
I have the following two signals A and B

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|  |_________________|  |__|  |__|  |__|  |__|  |__|  |________________|

Note that:

There is no common clock between them available
Signal B always changes when A is low and A always changes when B is low

I would like to create a 6-bit counter that increments its value every negative edge of signal A and then outputs its value bitwise in between, exactly at the positive edges of signal B.

The problem is I have to share a state between these two, for example:

wire bit_output;
reg [5:0] counter;
reg [5:0] current_value;
always @(posedge signalA) begin
  counter <= counter + 1;
  current_value <= counter;
end

always @(posedge signalB) begin
  current_value <= { current_value[4:0], 1'b0 };
end

assign bit_value = current_value[5];

Now this is unfortunately not a valid Verilog code, for example in Xilinx ISE I get:

Signal current_value[5] in unit test is connected to following multiple drivers:

I tried placing them into one always statement but this is not possible either:

Assignment under multiple single edges is not supported for synthesis

If I had a common clock I could use a conventional state machine but in this case I only have these two independent signals.

No matter with which solution I come up, I always need to share data somehow.

I do not want to run both paths independently; for example having a counter for SignalB and if it is zero, initialize with data from A because the initial condition would be undefined. I would like to ensure that the data that is spit out on the positive edges of signal B are always properly initialized at the falling edge of signal A even if, for example, only 3 positive signal B edges occur.

What is the easiest way to implement this?

(this is just a simplified example to keep things compact; the actual task is more complicated)


texts:
I'm selecting parts for this boost converter circuit:

The BOM lists these devices:

I'm at a hobbyist level with electronics so I can't tell when design decisions are arbitrary and when they're deliberate.

The first capacitor is a 0402 package, but I can't solder that.  Can I replace that with a similarly specified 0805?

The second capacitor is a 1206 package.  Does that package size matter?  Would a 0805 suffice (just out of curiosity)?

Here's what I'm looking at purchasing.  Do these parts look interchangeable with the ones from the TI Workbench?