texts:
I know very little about electronics so I was hoping to get some advise on a small project I want to do at home.

My home treadmill already has the standard dashboard that tells me the mph I'm going, time and so on, however it doesn't offer any way to get at that information - as you'd expect no dev kits, ways of accessing the data via bluetooth etc. etc.

So my plan is to build a cheap sensor that would measure the speed of the belt. For this I've got the following in mind:

A small square with some kind of high visibility sticker/paint on the belt.
A way of tracking the belt paint passing the camera lens, or preferably something cheaper than a camera lens. (This would be calibrated to know how far a second represents on my treadmill).
Battery-powered by AA/AAA batteries.
A wifi chip that broadcasts the information it gets from the sensor. I haven't figured out how this will be configured to join my wifi network.

Now the question - is there some kind of cheap sensor that could do the tracking? And is my sketchy idea feasible?

I don't want to have to open up the engine or attach wires to the existing sensors, I'm hoping to build something that's entirely independent.


texts:
I got to know 4 circuits used for Precharging in SRAM. I have few questions regarding circuits explanation:

Diagram (a):

Q1: It mentions it as diode-connected NMOS pair. Why?

Q2: This burns more power during write operations where one of the bitlines is pulled low by the write amp, again fighting this constant pullup.

Diagram (c) and (d):

Q1: What is advantage of (d) over (c)? The book mentions the following for (c):

  This kind of configuration was typical for moderate supply voltages (e.g., 3.3 V) or when the sense amplifiers used for amplification performed more optimally only at common-mode voltage levels below the supply voltage. But as supply voltages go down, and Vt differences due to process variations may significantly affect the performance, this configuration becomes impractical.


texts: Conductor interaction with single battery terminal

texts:
What really is happening inside a wire and inside battery when I connect one end of wire to the one terminal of battery but not the other (open circuit )?

Questions:

If I connect to the '+' terminal does any electron (even one ) get sucked inside battery terminal or not? If not why so?
If now, I connect wire's other distant end to another terminal (closed circuit ), what happens at starting? Which terminal will act first in drawing or supplying electrons. (I mean process of starting current).


texts: what is a bus (physically) in digital design?

texts:
Is bus a bunch of wires connected between functional blocks? or does it have any other functional importance?

if possible, someone please provide some material to get some clear understanding.


texts: Ground vias use on no-trace areas at a 4-layer PCB

texts:
Background info:
I am using a 4 layer PCB stack: Signal, Gnd, Signal+Power, Signal (mostly ground). To avoid out of question issues, I use this set-up due to a reference design on Texas Instruments as they use the stack-up in the same format.

All the unused areas are ground on this PCB, I also use via stitching on the edges and on the signal traces.

My question is that, is it better to be generous on the ground vias where no signal or power traces are used or is it better to keep them as solid as possible? (please note that un-used areas are ground only on all layers).

I read some articles as ground via can be a noise source, some articles says it is good to use for EMC/EMI. Can anyone please explain what are the general good practice to use the ground vias for the un-used areas? It'd be also interesting to learn how to use the un-used ground areas on 2 layer PCB (ground vias or solid area)?

I am sharing a part of the PCB (no ground pour on the picture to see the vias better)


texts: Why are the collector and emitter on this TO-92 transistor reversed?

texts:
Every TO-92 BJT I've ever seen reads collector-base-emitter when read left-to-right facing the flat side. Then I found this lovely part, BC517. It reads emitter-base-collector.

Have I only been exposed to a strangely homogeneous subset of TO-92 transistors, or is this one really an exception? If it's really a weird transistor, what possible technical reason is there for defying what I understood to be a universal standard?


texts: Is there a formula to determine the size of decoupling capacitors?

texts:
I have used many decoupling capacitors in circuits and have seen them in many textbooks, but they never give an explanation about why they picked a certain size of capacitor.  Everyone seems to have a "rule" about the size that they picked up along the way.

But is there an actual formula that dictates what size of decoupling capacitor to use?  If not, are there some mathematics and physics that I could be pointed to to develop something more rigorous than a rule of thumb?

Many people have said that the size is not always critical, but I imagine there is a point at which changing the size would cause the circuit to fail or at least degrade.  I would like to know what this critical point is, determining the bare minimum case, etc.


texts: How can I simulate a 150MHz crystal oscillator in LTspice

texts: I am trying to simulate a 150MHz crystal in LTspice, but I don't get any oscillation out of it. I have an equivalent circuit of a 32MHz crystal, even with that I don't get anything out of it. What am I doing wrong?


texts:
Story
Received a Philips HTS6520 for free however the subwoofer (and remote) is missing, no cables at all, so unable to use it because the sub also provides the power (read on to see what I have done).

fig 1: the unit

I think it very sad to throw such well made device (really, construction is beautiful) away, that is why I start to investigate the device if it is possible to create a new power supply for it. The connector is a weird one, never seen before, 13 PIN SQUARE DIN connector. Cannot find any info about this connector however it seems be used at car systems, for example to interconnect a bluetooth device. Anyone know the exact name of this connector?

fig 2. the connector

I found the service manual of the Philips HTS6520 and figure out the connection to the motherboard (not the pinout of the connector because there are no pin numbers on the connector itself specified) and the connector PCB itself can be removed. Really nice. After removing the connector, a 12 pin female header can be found on the motherboard that can be easily used to poke some cables in it and implement my own cable for it.

fig 3. the header on the motherboard

Done this by following this created pinout/schematic (using the service manual):

fig 4. created pinout schematic - version 2

The +5V and +12v rails obtained from an old PSU (of another DVD player) lying around and that is working great! The unit is fully functional and can play CD's and DVD's. Used another Philips DVD player remote (found at a drift-store) and works fine however not all functions are available on the remote.

fig 5. Unit working (with two PSU's)

Question
The -30V power is a problem, I used another power supply for it to create the -30V rail. The -30V rail is used to power the VFD display. It is 'working' however the display is very very dim.

fig 6. display works however very dim

What could be the reason? Do I missed something? Has it something to do with my PSU configuration? Current cannot be a problem, the adapter is rated 3A. The whole unit only consumes 14W, about 470mA max. Check the voltage, no voltage drop, stable 30V.
So what could be the problem, any ideas?
Service manual and other documentation can be found in this zip (46,8 MB)


texts: How to conclude the necessity for unbalanced to balanced signal conversion for this scenario?

texts:
This is a bit specific system related question about simultaneous data-acquisition for several transducers. Therefore hope you don’t mind for the long intro and the question. It would be too implicit if I wouldn’t write in detail.

In an indoors environment I have been encountering issues due to using a single ended system. Basically 14 voltage inputs from various transducers were coupled to a single-ended input data-acquisition board. The transducers are all DC like outputs and here some examples data for humidity, temperature, load cell amplifier ect. Some of the transducers have been used for many years and calibrated each year at calibration institutes.

So the system was such that the transducers are single ended and the DAQ was also single ended. Since the system was single ended, all transducer grounds were grounded together and this was causing impedance coupling and ground loops. Since the cable length are around 15 meters.

Now the system will be replaced such that this new data-acquisition board will be used with these isolated differential inputs input modules. So this new board will have isolated voltage input modules which will provide such main benefits:  differential inputs, channel to channel isolation, low-pass filtering. So this seems fine for the input/daq side.

For clarity, below at Figure 1 I tried to draw the single-ended system used currently, and at Figure 2 the planned differential ended input system. In the diagrams below Trans represents a voltage transducer, coax cable the typical 50 Ohm coaxial BNC cable, and m depicts an isolated differential input module.

Here is my question:

My confusion here is that the transducer outputs(as you see in the datasheets) are not balanced and I don’t know how big are their output impedance. And since they are calibrated and almost all the transducers used are single ended outputs I’m stuck with the issue of not-entirely balanced system for this specific system.

If I use single-ended to diff-ended converters at the transducer outputs this might balance the system. But besides being costly to do it for each channel, my fear is to introduce offset or electronics noise by using such extra converters in the signal chain. And I checked such 0-10V transducers in the market such as temperature, humidity, barometric pressure transducers or load cell amplifiers in the market and they are almost always single ended output. It means their outputs are not balanced and the output impedance is most of time not given.

So I have three options:

Not using any single-ended to diff-ended converters
Using converters for each channel where I have no idea if I would introduce other problems
Throwing out all the transducers and try to find new balanced output transducers which would be extremely difficult for each new device.

How should I approach this problem and do I really worry a lot about this? Does anybody have practical experience with such scenario?

Edit regarding a comment:

Here is my concern:

Will the module prevent the issue due to the source output impedance above?

EDIT 2:

***Will the isolation by the modules cause the input signal floating with respect to AGND of the DAQ? I thought in that case it is equivalent to buffering.


texts: How can I go about obfuscating the design of my circuits and embedded controls?

texts: I am working on a new power converter, which will likely see significant sales into China. Similar designs by my company have a history of being cloned by entities in that region. To mitigate this, I'm considering ways of obfuscating my design. Code protection on my microprocessor, outer-layer power planes, and blind vias all come to mind as possibilities. Are these reasonable means to my end? Are there others I should consider?


texts: On using an electromagnet in a magnetic stirrer

texts:
What's the simplest and cheapest way to use one or more electromagnet to to stir a stir bar ?  That is, how to control the speed at which the polarities are reversed.
I don't want any mechanical part (no motor) or software (no PIC microcontroller) and the speed must be controllable by hand.

I could use a fan with a magnet but I'm curious to see an e-magnet at work.
I can figure out the rest of the circuit.


texts:
I want to control the output of a transformer. So the input is 220V, 50 Hz. I am stepping it down to 24V. Now I want a switch that can vary the output between 0-24v. How do I make such a switch? If I put a resistance for dropping the voltage, I am afraid it might get heated or it might result in some noise. What do I do? Any suggestions?

Update:

Just for clarification: I want Ac ranging from 0-24, so the user can control the output like 0-5v ac, 0-15v ac , 0-24v ac.. and so on. Sorry for not giving this detail in my question.


texts: Analog circuit design/building resources for complete beginner

texts: I'm a 1st year mechatronic engineering student and am just starting out with analog electronics.  I have some projects coming up which will involve designing and drawing circuit diagrams to address particular problems and then building the circuits (e.g. a circuit for testing electronic components). Can you recommend some good books/web tutorials that would give an easy to follow, step by step guide to the process?


texts:
In Square D's marketing copy for their plug on neutral load centers, they have a photo for demonstrating "cleaner wiring" in which the hot and neutral wires are twisted inside the panel before reaching the breaker. I agree it looks neater, but it got me thinking and I know just enough about electricity to be confused. I assume the practical answer is that a slow (~1 turn per inch) human-made twist in the last couple feet of a cable that runs 30-40 feet will have no real impact, but I'm curious.
In low-voltage DC data wires, twist is used to reduce emitted EMI and reject received EMI. In a typical home I doubt contractors care about the noise on the voltage line, but as someone with a lot of sensitive electronics it interests me. But I've also seen it suggested that the increased capacitance between the twisted wires could increase current drain, which in turn could cause nuisance trips of AFCI breakers.
And I pretty much only understand electricity at all in DC. I don't know or understand what impacts AC may have on this.
So what kind of impacts, if any, could we expect to see from twisting a previously parallel load/neutral pair, carrying 120V AC?


texts: Error reading data through UART using peripheral library in PIC32?

texts:
I am trying to receive data using UART. I am using PIC32MX795F512L Micro Controller and using 32 bit peripheral library, so I using functions like putsUART or ReadUART1
Now in the code :

int main()
{
 OpenUART1( UART_EN | UART_NO_PAR_8BIT | UART_1STOPBIT  , UART_RX_ENABLE | UART_TX_ENABLE, (FPB/16/BAUDRATE)-1 );
 TRISDbits.TRISD5 = 0;
  while(1)
  {
    char RX_data;
    RX_data = ReadUART1();
    if(RX_data == '1')
    {
      LATDbits.LATD5 = 1;
      putsUART1("LED ON");
     }

     elseif(RX_data == 'q')
     {
       LATDbits.LATD5 = 0;
       putsUART1("LED OFF");
      }
   }
}

Now whenever I type 1 in the terminal led turns on but when I type q then led doesnt turns off. It works with digits but not with letters. Like if I do

elseif(Rx_data == '2')

Then it will work but not with

elseif(RX_data == 'q')

I don't know where I am missing the point. Please help.


texts:
I need to design a circuit that implements an SPDT switch using Triacs and Optoisolators. Currently I am implementing this with two pairs of Optoisolated Triacs with one having inverted signal from the uC. Hence at all times, 1 of the Optoisolated Triacs is "ON" and the other is "OFF". However, under no power condition, both the pairs the act as NO circuits.

I need to Switch 220V AC with 3.3V DC current.

Kindly help me build a circuit where even under no power conditions, I have 1 NO and 1 NC path available.


texts:
I am learning voltage dividing and created an array of different values to get a broader perspective and found this repeating sequence. Can anyone explain why the combo of r1 as 6000 ohm and r2 of 1500 ohm will always result with

voltage in x 2 / 10?

python to support

r1 = 6000
r2 = 1500

digits = [96, 48, 24, 12, 9, 5, 3, 2, 1]

def voltdivide(voltagein):
    dividby = r1 + r2
    LaResistawnce = r2 / dividby
    sum = voltagein * LaResistawnce
    return(round(sum, 2))

for n in digits:
    print(voltdivide(n))

print('\n\r ▲ voltage divide '
      '\n\r ▼ double divided by 10'
      '\n\r')

for n in digits:
    nn = n * 2
    movedeci = nn / 10
    print(round(movedeci, 2))

19.2
9.6
4.8
2.4
1.8
1.0
0.6
0.4
0.2

 ▲ voltage divide
 ▼ double divided by 10

19.2
9.6
4.8
2.4
1.8
1.0
0.6
0.4
0.2


texts: How to detect square wave using GPIO port of PIC12f675?

texts: Actually I am generating square wave using PIC12f675 from one GPIO port, but want to detect that square wave using other pin on GPIO port, how can we do that? I have succeeded by using TMR0 to use as a counter. My application is to develop water level controller so generating square wave to avoid corrosion of sensors.


texts: Precise Current Limiting for Variable 0–300VDC Supply

texts:
I wish to use this circuit

to achieve a variable 0–300V DC supply. However, I'm interested in keeping the current below 50 mA, with as little variance from that value as I can achieve without doing anything incredibly expensive.

According to the circuit's designer, maximum current is determined by the resistor R2 and the transistor Q2:

  The transistor Q2-BC337 and the shunt resistor R2 – 3.3ohm are added for as a current limiter. When the current output is too increased, the Q2 will stop the gate pin of the Q1 immediately, which will be guard the higher current output

But it was made clear to me in a previous question that this does not produce an exact cap on the maximum current, instead constraining it to more of a "ball park".

My question, then, is (adding a hard value): how to precisely limit the current output of this supply, within a 5mA maximum deviation from the desired maximum value, for as cheaply as possible.

I would want the circuit to cease supplying power if the current fluctuates above the maximum tolerance.


texts: estimating battery discharge current approximately from ac load current

texts:
I would like to know that if we have a data logger installed at a site and the logger measured the constant load current of 10 A from the Grid(Single phase@ 230 v) during a certain time say 10 am.

  Now my question is if i replaced the grid with a battery back up s/m
  (for eg: say 48 v 150 AH Battery and a DC to AC converter System) what
  would be the battery discharge current from the battery for the time
  10 am.?

Considering the absence of grid here what will be the approximate current drawn from the battery to match the out put current of 10A @ 230V for the DC-AC converter.
And what all factors should we consider before approximating the battery discharge current

I would appreciate your valuable inputs


texts: Piezo element lifespan in vibration environment

texts: Can anybody guess or does anyone know what lifespan can be expected of this piezoelectric sensor - https://www.sparkfun.com/products/10293 - with a weight glued to it and used inside a passenger vehicle ?


texts: LM317 Constant Current vs Transistor Current Limiter

texts:
LM317 with Current Limiter configuration:

Current limiter circuit with transistors:

I am used to drive LEDs in my PCBs with LM317. However I recently came across this circuit which will cost less.

Questions:

Is the transistor circuit a good choice for an application with potential voltage spikes? If not, can you tell me what extra measures are taken in LM317 for better stability?
What can I do to increase current stability in transistor circuit?


texts: STM32F103 - Starting timers at the same time

texts:
I am using an STM32F103 board (Blue Pill), and I have a simple application where I need to have two pulses on different pins.

I achieve this using Timer3 and Timer4 configured with PWM output on two channels (one each). The problem is that the timers do not start at the same time, and they have an offset of about 3 µs. The main clock is running at 28 MHz.

In the code, changing the order of these two lines will determine what timer starts first (which one is ahead with 3 µs of the other):

  HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_2);
  HAL_TIM_PWM_Start(&htim4, TIM_CHANNEL_2);

Is there something I can do? To be noted that in the same program I have Timer1 set up as Capture Compare No Output, and Timer2 to generate a 1.4 MHz clock in the same manner as Timer3 and Timer4.

Later Edit. The called function in the HAL driver:

HAL_StatusTypeDef HAL_TIM_PWM_Start(TIM_HandleTypeDef *htim, uint32_t Channel)
{
  /* Check the parameters */
  assert_param(IS_TIM_CCX_INSTANCE(htim->Instance, Channel));

  /* Enable the Capture compare channel */
  TIM_CCxChannelCmd(htim->Instance, Channel, TIM_CCx_ENABLE);

  if(IS_TIM_BREAK_INSTANCE(htim->Instance) != RESET)
  {
    /* Enable the main output */
    __HAL_TIM_MOE_ENABLE(htim);
  }

  /* Enable the Peripheral */
  __HAL_TIM_ENABLE(htim);

  /* Return function status */
  return HAL_OK;
}


texts: STM32 USART synchronous mode receive does not work

texts:
I am using a STM32L052K6U6 to communicate with an SPI slave using the UART1 synchronous mode (configured with CubeMX, using the LL library).

Setup code generated by CubeMX (I left out the Tx and Clk pin config as those pins do what they should):

  GPIO_InitStruct.Pin = USART1_RX_ECG_Pin;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_MEDIUM;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_OPENDRAIN;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_4;
  LL_GPIO_Init(USART1_RX_ECG_GPIO_Port, &GPIO_InitStruct);

  USART_InitStruct.BaudRate = 2000000;
  USART_InitStruct.DataWidth = LL_USART_DATAWIDTH_8B;
  USART_InitStruct.StopBits = LL_USART_STOPBITS_0_5;
  USART_InitStruct.Parity = LL_USART_PARITY_NONE;
  USART_InitStruct.TransferDirection = LL_USART_DIRECTION_TX_RX;
  USART_InitStruct.OverSampling = LL_USART_OVERSAMPLING_8;

  LL_USART_Init(USART1, &USART_InitStruct);

  USART_ClockInitStruct.ClockPolarity = LL_USART_POLARITY_LOW;
  USART_ClockInitStruct.ClockPhase = LL_USART_PHASE_1EDGE;
  USART_ClockInitStruct.LastBitClockPulse = LL_USART_LASTCLKPULSE_OUTPUT;
  LL_USART_ClockInit(USART1, &USART_ClockInitStruct);

  LL_USART_EnableDEMode(USART1);

  LL_USART_DisableDEMode(USART1);

  LL_USART_DisableDMADeactOnRxErr(USART1);

  LL_USART_Enable(USART1);

  LL_USART_ConfigSyncMode(USART1);

  LL_USART_Enable(USART1);

Init code written by me, executed after the code above (the EnableDirection calls are not actually needed, Tx and RX is already enabled in the code above):

LL_USART_Disable(USART1);

LL_USART_SetTransferBitOrder(USART1, LL_USART_BITORDER_MSBFIRST);

LL_USART_EnableDirectionTx(USART1);
LL_USART_EnableDirectionRx(USART1);

LL_USART_Enable(USART1);

This is part of the code that receives data:

LL_USART_TransmitData8(USART1, 0);
while(!LL_USART_IsActiveFlag_BUSY(USART1));
while(LL_USART_IsActiveFlag_BUSY(USART1));
uint8_t data_1 = LL_USART_ReceiveData8(USART1);

Probing the bus reveals that the clock generation and data sending works fine and the slave responds with the expected data. The receiver is enabled, but the data is not received by the microcontroller. The receive data register and the RXNE flag stay zero.
What could cause this?


texts: Does transformer line side voltage varies with backup generator on load side running at from 0 to 100%?

texts:
We have a transformer of 750 KVA with 5.75% impedance. On the load side we have loads and a back-up emergency generator. This emergency generator is capable of supplying the loads and still export some energy to the utility. Today a senior engineer in a meeting said:

Going from 0% load to 100% load on this transformer will result in a
5.75% drop in voltage. Going from 0% load to 50% load on this transformer will result in a 2.875% drop in voltage.

I totally understand this since in this case the backup generator is not running and the voltage supplied to the load has a loss when passing through the transformer winding

However he also said:

Going from 0% load to 100% generator output (100% of transformer rating would be 750 KVA or approx 750 Amps) will result in a 5.75% increase in voltage.So if the voltage in the plant is approx 620V at 0% load, it will increase to 656V at 750KVA generator output.

I don't understand this part. The generator is set to synchronize to the grid at whatever voltage it is operating. After this it gradually starts to increase kW output while maintaining the voltage.

Why would there be a voltage increase on the load if the generator control loop is keeping it at whatever voltage the grid has?
What would happen to the voltage on the line side of the transformer? Isn't there also a loss from the voltage the generator is outputting as it tries to get across the transformer impedance and get to the grid?


texts:
I am interested in using the greyscale version (VM-010-BW-LVDS) of this camera module:

VM-010: phyCAM-S camera module, WVGA monochrome

I want to use the camera with external trigger (in snapshot mode) and use a very low resolution. I need to acquire images from the camera in my C++ computer vision code in Debian Linux. I need to connect the camera to a specific ARM mainboard which has various IOs (I2C, UART, SPI) but unfortunately no dedicated LVDS port, so I think of using board's GPIO pins instead. The mainboard is available in two revisions - 1 and 4 core CPU ranging from 700-900 MHz. The GPIO has been speed-tested to be able to generate a 14 MHz (or 22 MHz in with -O3 compiler optimization flag) square wave in C. The GPIO provides either zero or 3.3V.

There is a camera datasheet available. For LVDS it specifies the data bitstream (8+2 bits) and data frequency the board accepts (13-27 MHz).

Things I do not understand:

Is the ARM mainboard fast enough to be able to read the data bitstream from the camera on its GPIO besides to generating the clock signal? I can dedicate the whole mainboard only to the camera task and use Linux real-time kernel.
I probably need at least some minimal circuity to convert the 0/3.3V GPIO voltage to the LVDS 1.2V+-0.2V differential. Any suggestions here?
The datasheet talks about LVDS deserialization. Can I do everything in C++ or do I need additional circuit for this (LVDS deserializer, driver etc.)?
The datasheet also says: "Pixel clock is transferred as an embedded signal in the LVDS
stream. It is recovered by the LVDS deserializer." I do not understand this too but it probably is related to the previous point.
Camera configuration is done over I2C, but detailed info seems to be missing in the datasheet (modifying the registers etc.).

The company offers its own Linux ARM mainboards with dedicated LVDS ports to connect the camera. It may help to get one of those mainboards and try to reverse-engineer some stuff or maybe even use their binaries if they are compatible. Thanks for any help in advance - it is highly appreciated!


texts: Sources of online broadband RF energy data stream?

texts: I am interested in finding recordings of broadband FM radio emissions, ideally in the marine VHF frequencies (156.0 and 162.025), in order to understand carrier artifacts and distortions that could affect communications. I need the raw broadband data (from an SDR), not the demodulated audio. Are there any archives of such data or live data streams?


texts: Whats the most effective int on a 8-Bit Microcontroller?

texts:
The size of an int is defined by the compiler, not by the processor. Thats why e.g. int_8 exist. However, I was thought that usually int is the most effective datatype. Is this still true when e.g. working on a Atmega8?

Atmega8 uses 16bit as many smaller system do. But using a 8bit int would save me one fetch and execution wouldn't it?


texts: Can you please help identify this circular part with 2 black wires and 2 red wires?

texts: I found this part in an old auction lot I bought.  Could you please help identify what this part is?


texts: Connecting lithium ion batteries in parallel

texts:
I have 6 lithium ion batteries that are from some Android tablets that I've recycled, they are rated as 5000 mAh, 3.8 V
and have their own protection PCBs soldered to them. The tablets they came from are from hotel rooms so they hardly get used and spent their days plugged into a charger, they are all less than a year old and are identical.
I bought a IP5328P power bank board and plan on connecting them all in parallel to the board. I wanted to see if the batteries are the same capacity so I connected each one by themselves to the powerbank board to charge them up until they were all the same fully charged voltage, then connected all of them in parallel to the powerbank board and plugged my phone in to discharge all the batteries all at once. When it was almost dead, I unplugged my phone and unsoldered all the batteries and noticed that they all had different voltages, one was 3.42V another was 3.60V and another was 3.66V.
My question is, would it be alright to charge them all up in parallel, will they balance themselves to the same voltage again? They each have their own protection board so I'd assume they would stop charging once they are charged?
Thanks for the help.


texts: Finding Equivalent Transistors (BC178 and 2N2646)

texts:
I have an old schematic which uses two obsolete transistors, the BC178 and the 2N2646.

By searching I was able to find that the BC178 can be replaced by the BC177 as written on this page: http://www.el-component.com/bipolar-transistors/bc178

I haven't been able to find an equivalent for the 2N2646. I did find a page that appears to let you enter in the specs of the transistor and it will list equivalents, but I am not well versed in transistors to understand how to use the cross-reference calculator which is available here: https://alltransistors.com

I was expecting it to be easier to find equivalent replacements for these older obsolete devices, but it seems to be difficult.

Can anyone please provide me information as to how I can find replacement parts for these two transistors, and guide me towards resources to make it easier to find equivalents in the future?

I exhausted my search capabilities on google searching for "replacement" and "equivalents" of those two devices. It is overwhelming to me the numerous number of transistors and I am struggling to understand the very small differences in spec.

Thank you in advance for your wisdom!


texts: Monitoring serial communication and problems with my RS232 listening device

texts:
Currently I'm working on a little reverse-engineering project, where I want to understand the communication between the controlling software and a modem/DCE via serial port (RS232C).

EDIT: both the controlling software and the modem are from the early 90s, the software only runs on MS DOS. My laptop, which is supposed to do the work of understanding the communication, runs on Windows 10 and will be connected through a Serial to USB Adapter. (end of edited part)

For this purpose I already build a little listening device which mostly works fine.  It looks like this:

I've drawn the circuit diagram but I got the 'blueprints' from http://airborn.com.au/serial/rs232.html, however, no description or explanation is provided there. I just build it and got lucky. Unfortunately I'm not as good in electronics as in the software-part of my project. I've got some simple questions first I hope someone can answer:

I think I kind of get why there needs to be a diode at line 2 ('Transmit Data' from a female point of view). To keep it one way? Is that correct? Or am I thinking too simple?
I am nowhere near an understanding of why line 3 ('Receive Data' from a female point of view) needs a resistor, instead of a diode. Why is that? And why the specific resistance of 2.2kOhm?

Now for the not so simple question (I think). I don't expect answers, maybe some tips or hints:

The software does an initialization sequence in order to see if the modem works and is connected. This initialization fails if I start the controlling PC and the modem while I am connected thorough my device. I am only able to get a successful initialization and to the actual main menu of the software if I disconnect one of the cables going to my listening computer (either the one with the diode or the one with the resistor). However, if I plug it back in after the initialization everything works fine, I can listen both ways again and the communication between controlling software and the modem is not impeded at all.

Why does this 'work around the initialization by unplugging one cable' approach work for either line, the diode- and the resistor-cable? I thought it would either matter which one to disconnect or I would have to disconnect both.

Thanks in advance!


texts: Lumped parameter vs transmission line model for a piece of cable

texts:
I would like to model a piece of cable (less than 5m) over a frequency range of DC to \$1\mathrm{MHz}\$. I am however doubting if I can approximate it by a lumped parameter model (mainly at \$1\mathrm{MHz}\$) or if I need to model it as a continuous transmission line. If I am correct, lumped parameters can be used as long as the physical dimensions of the system (here: cable length) are sufficiently below the wavelength lambda. Since lambda (in free space) can be calculated using the speed of light \$c\$ and \$f\$, for \$1\mathrm{MHz}\$ I get:
$$\lambda = \frac{300000000\text{ km/s}}{1000000\text{ Hz}} = 300\mathrm{ m}\text{ (approximately)}.
$$ Since my physical system is much smaller, I suppose a lumped parameter representation is sufficiently accurate. However, in transmission line theory, the wavelength is derived through the propagation constant
$$
\gamma = \alpha + j\cdot\beta.
$$
\$\gamma\$ is calculated through the cable's impedance and admittance and the corresponding wavelength can be calculated as
$$
\lambda = 2\cdot\frac{\pi}{\beta}.
$$ That would thus mean that the physical properties (\$R,L,C\$) of my cable will determine the wavelength. Does that also mean that two different cables of the same length would possibly need to be modeled as a continuous or a lumped parameter model, just because we would choose thicker wires or have more spacing between the wires? I am a bit confused on the approach that should be followed and I am happy to receive your input.


texts: How to stop a switched current affecting an IC?

texts:
I have 10 circuits each consisting of a Touch IC (Atmel at42qt1010) and electrode, and 2 x 350mA Constant current regulators (NSI50350AST3G) and LED's. All connected to a Arduino Mega, by ~1 meter cables.

The header pin is as follows:

+5v (for Touch IC)
LED2 (HIGH switches circuit on)
TOUCH OUT (When touch is detect this is HIGH)
LED1 (HIGH switches circuit on)
+7.5v (for Constant current regulators)
GND

So on all circuits 1,5,6 are commonly connected.
2,3,4 are isolated and connected to the MCU.

The problem occurs when switching pins 2 & 4, doing so seemingly causes random circuits to output 3 as HIGH. Even if I switch the LED'S on say circuit 1, circuit 5 may falsely start detecting a touch.

The only way I have found to remedy this is two always maintain the same loading, for example on circuit 1 if LED1 is ON & LED2 is OFF, if I toggle there states at the same time, everything is OK. However if there is a delay say 20ms, it will cause the problem. Or if I want them both off, the major problem I have now...

This behavior can also be seen (not to the same extent) when +7.5v, is not even connected.

Attached is my schematic. I have 10 of these, connected to an Arduino Mega.
+5v is provided by the Arduino and USB
+7.5 is provided by an external supply.
GND's are connected.

I am not using PWM, just HIGH and LOW to control the LED's

Please help! I thought I had this sorted but a couple of days before the project goes out I find this bug.

UPDATE

After following the advice given here, and reading these further application notes, I have revised my schematic and also incorporated a three channel LED, rather than the two previous LED's. I will also plan to run these with a PWM signal now.

The Application note 'Secrets of a Successful QTouch Design - Atmel Corporation'

The Application note 'Power Supply Considerations for Atmel Capacitive -touch IC's'
Shows a LM78L05 regulator

Schematic 2.0

PCB Layout 3.0 - Routing and trace widths still need to be optimised.

Questions

1.Should I use the LDO regulator mentioned in the above application note instead?

2.Will I be OK using this 7.5V - 10V across 10 of these circuits, therefore having 30 PWM high current circuits impacting on each other?
It will be provided by a switched mode psu such as http://uk.farnell.com/xp-power/jpm80ps07/psu-80w-7-5v-10-7a/dp/1109830

3.Have I gone overboard with the 3x 100uF electrolytic caps?

4.Anything else I should do? I will then re-design the PCB.


texts:
I would definitively like to know how a catastrophic failure of a MOSFET may be evoked considering its factuall that, overvoltage is imperative to destruction. We also know the technology is also important to consider, but for this post I would like to emphasize planar and trench. If however, people would like other techs I may update this post to accommodate them too.

I do not disclude radioactivity methods but rather more interested in "leads" of device attached to juice.

Now then, what methods and combinations do mayhem.

EDIT: The worst catastrophic failure possible is all I am asking.

EDIT#2: MOS transistor is to be vaporized with no remains but a brief audible tone.


texts: Connect different devices (Ground/Voltage mismatch)

texts:
To begin with, I realize that voltage is relative but I do not understand how to get a common ground so that everything is relatively correct to go in and out of the various chips.

The picture summarizes the setup:

Xbox plugged into the wall -> Wired USB Xbox controller which the input runs at 1.8v. Streaming the controller button input through a level shifter (SN74LVC245A) which shifts the logic to 3.3v -> SPI chip (MCP23S17) -> FPGA (Basys 2). The FPGA is connected to the computer via USB which is plugged in to the wall.

I would expect the multimeter would read 1.8v because of the assumed common ground. But I guess this is not the case because of what the value suggests. Right now both the laptop and Xbox are plugged into the same power strip but I could see how there might be further mismatch if they were on separate rails.

How do I work around this issue? Have I overlooked something simple or is it a flaw in design?

I realize that 4 buttons would be easier to go straight into the FPGA after coming out of the level shifter but I plan to add a lot more of the controllers input which I do not have enough pins for.


texts: How to determine the steady state voltage across two capacitors in parallel

texts: Say we have two capacitors C1 and C2, initially isolated from each other and each having an initial voltage Vc1 and Vc2 respectively, where Vc1>Vc2. When suddenly connected to each other in parallel, obviously C1 will discharge to C2 until their voltages meet at a steady state value. Assuming zero resistance between the two capacitors, what is the expression for this steady state voltage Vc in terms of Vc1 and Vc2? Is it just the average of Vc1 and Vc2?


texts: DC motor fails to operate at solar panel even though the voltage is correct

texts: I have several small (1.5 - 6V) DC motors. If I hook up one or two 1.5V batteries in series to any of the motors, the motor runs. I also have several small solar panels that produce from 2 to 6 Volts maximum. When I hook any of the panels to a motor, the motor does not run. Why is that?


texts: Is using a 12.5V PSU ok for a 12V LED? Also would this wiring work?

texts:
I am looking to make a small central box to control my LED strips from. However, the switches I've bought are 12V, I only have a 12.5V plug power supply and the LED strips are 5V.

I was told a 1000Ω resistor would take 12V down to 5V. (I'm not accounting for any current difference or wattage, I'm new to electronics.)

Would this work? What issues might I run into?

This is the switches schematic:

https://www.seebay.co.uk/media/catalog/product/h/a/halo-wiring_3.jpg

simulate this circuit – Schematic created using CircuitLab

Thanks for all the advice and the explanation. However for my instance it was me being stupid, I thought the switch LED required 12V as it only lit up when I tried it with 12V and not when I tryed it with 5V. This was because I wasn't linking the - and C to allow it to light up when powered. Sorry


texts: If I use a 19V 4.7A supply to a MAX 250W ATX power supply am I an idiot or should it be safe enough?

texts:
I can do the maths, I get near 90W, but I'm only planning to draw under a quarter of the power supplies (ebay link) rated max of 5V/12V combo (estimated load 30W). I therefore consider my 19V old laptop supply adequate plus a little overhead. Reading the listing I see a power rating of 150-250W, I expect that translates to 150W continuous and 250W peak, but who knows right now. I did debate splicing two old laptop chargers together, but worry although it would work I probably should have some protection circuitry to stop them fighting each other.

Am I an idiot? (I accept that I am idiotically frugal to attempt to use old laptop chargers instead of a dedicated high load supply but the cost to recycling ratio doesn't add up)

I understand to a level of intermediate electronics but always considered that an underpowered supply was only a problem if it was truly unmatched. i.e. you were expecting the device to draw the full load or have a relatively high startup(or intermittent) draw then your supply should match otherwise load dependent. Reading Voltage at what Amperage made me question my sanity and proneness to unnecessary fire risk.

Don't get me wrong, I've always advised to have a suitably matched rating on supply and device or ideally over-rated supply to avoid running hot.

End use devices are various voltage hobby microcontrollers and SATA drives via https://www.amazon.co.uk/gp/aw/d/B07R8S8VTT


texts:
Tutorials like this one recommend using a separate board in order to control a stepper motor. However, I don't really want to go and buy one (even though they are cheap).

My question is, why can't the stepper motor be controlled directly with a Raspberry Pi? If the problem is voltage or current, what stops me from just using a transistor?


texts: What kind of relay should be used to control a thermostat terminal?

texts:
I'm building a remote controller for my thermostat, and the only step I have remaining is the connection between the Raspberry Pi and the thermostat terminal. Essentially, the Rpi will be replacing my current Honeywell interface.

What types of relays/switches send power to a thermostat's wires, and which are the safest to use?

Here's there terminal I'm referring, to, it looks just like this:


texts: Optimum physical arrangement for series connection of high-current batteries

texts:
simulate this circuit – Schematic created using CircuitLab

I noticed when connecting multiple big batteries in series some people use zig zag configuration (right) instead of the one on the left, what would be the potential reason for that? If the current is very big, what is the downside for huge current (500A) circling?


texts: I wonder if it is possible at run time to detect that an external Oscillator has gone bad and the application now falls back to internal Oscillator.. specially for the case of STM32F407 MCU?


texts: High Voltage Power supply with current limiting output

texts: I found this simple PSU design on the web. I tried to use it but already 5 MOSFETs and 2 npn transistors are blown. I use IRF840 and BC546 or KSD1616AGBU transistors and fixed value resistors in place of VR1. The load is about a 60 Ohm resistance wire and i mesaured the current which is 4 Amps so it's not limited. The voltage is somewhere between 250 and 300 Volts. When the current rises on R2 it's supposed open Q2 transistor that would set the gate and source of the mosfet equal hence it would close it down but it doesn't happen. After the failure i measured the mosfet and the source drain is shorted (I assume the diode is gone) but i'm no sure what's going on. Can anyone help me what may possibly go wrong or just recommend a proper circuit that does the job? I searched through the web and found some circuits but they seem to be just a more complex variation of this one using the same current sensing techinque so i'm a little uncertain. Thank you


texts: Multimeter temperature coefficient - Specified accuracy

texts:
I want to calculate the temperature coefficient for a digital multimeter.
The datasheet I read it is calculated as:

0.1*(specified accuracy)/°C (<18°C or >28°C)

Do you know what specified accuracy stands for?

I mean, can I consider specified accuracy as the composition of multimeter accuracy and resolution?

Thank you in advance.


texts: How do I apply Ampere's law for a solenoid with a core?

texts:
I have a solenoid with a ferromagnetic core (like a transformer). Now we know that the magnetic field H, is fully restricted inside the ferromagnetic core. My problem is with the application of Ampere's law. The configuration is as below:

The black box is the ferromagnetic core. Let the red lines be the (closed) paths over which I compute the integral:
\$\oint H \cdot dl=Ni \$
Now, if I select the paths: \$a\to b\to f\to e\to a\$, \$a\to c\to g\to e\to a\$ and finally \$a\to d\to h\to e\to a\$, I get the conflicting equations: \$HA=Ni\$, \$HB=Ni\$ and \$HC=Ni\$ respectively, where:
\$ab+fe+ea=A\$
\$ac+ge+ea=B\$
\$ad+dh+he+ea=C\$
I know I am making a stupid mistake somewhere. Please help...


texts: Accidentally used plumbing flux on a PCB; How do I remove it to reuse the board?

texts:
Two weeks ago, I picked the wrong tub of flux from my toolbox and used it for making a 9VAC -> 5VDC adapter. I fluxed all the components and soldered it down before realising I was using PLUMBING flux!

The solder pads are all still intact and I've tested the conductivity of the leads of all my parts; they are all intact.

So to summarize,

How should I remove the flux after desoldering in such a way that I can reuse the PCB?

and

I may have used small amounts on other repairs in the past (all of them my own personal projects, none for others). Will I have to worry too much about these?

The flux is labeled as  "alpha metals" brand "soldering paste flux".


texts: Would crosstalk be an effect at < 1 kHz signals up to 2.2A?

texts:
I'm planning on the use of a current transducer to monitor the current of an induction motor (full load amperage = 2.2A @ 60 Hz).
(Link of current transducer, model: LTS 6-NP)

If I connect the input of the transducer to two parallel 20 AWG wire connections (to allow up to 3A to pass), with a wire length of approximately 10 cm.,
would cross-talk influence the current passing through the wires?

The frequency components of the current being monitored are also of interest, up to 1 kHz.

EDIT: FYI, I have the input / output wires connected in a twisted-pair manner.


texts:
I've been looking around at the different battery options for storing mains power but have found there don't seem to be a lot of offerings. Uninterruptible power supplies geared towards computer equipment seems to be the closest main stream product. Is it a big challenge to store a large amount of mains power, say 24 hours of a typical household's consumption, in a battery?

One of the reasons I ask is that where I live there are off peak electricity tariffs that are up up to 50% less than the cost of peak tariffs. If a battery could be used to store power in off peak periods for consumption in peak periods the savings could be significant even if the battery efficiency was as low as 80%.


texts: My textbook says that this figure requires twelve pins. Can anyone explain why this combination of gates requires twelve pins?


texts: Monte Carlo Simulation In Python instead of HSPICE

texts:
Suppose I have a resistor and I want to simulate process variation on it.
When I was reading online, I noticed that Monte Carlo simulation is used for this purpose. I also noticed that HSPICE has this option.
However, I like to use Python for this purpose. I wanted to generated different resistance using Python random number generator (such as Gaussian distribution). I was wondering if these two methods (HSPICE or Python) are conceptually the same procedure.


texts:
I need to create a circuit specifically for powering two devices.
These devices include a device, which has to be powered via 5V USB and another device which has to be powered with at least 6V (all DC).

Now, 12V power supplies are quite cheap.

Can i simply use a 7805 regulator to power the 5V device? Does it support 12V as an input?
What about the other device? I thought about using a simple resistor for this one, as current drain (should) remain constant over time.
Is that feasible? How would you implement such circuit?

Thanks in advance.


texts: Dependence of transistor current gain on operating conditions

texts:
According to "Gray & Meyer: Analysis and Design of Analog integrated circuits" transistor current gain Beta (in forward-active region) depend on operating conditions of the transistor.

Region 1 is the low-current region, where β decreases as Ic decreases,
Region 2 is the midcurrent region, where β is approximately constant,
Region 3 is the high-current region, where β decreases as Ic increases.

While ideally β is always constant.

My questions:

Why does this "effect" occurs?
If collector current increases/decreases then base current also increases/decreases for proportional amount, right? Then β should be always constant
Is this β dependence on operating conditions significant when talking about small or large signal model?


texts: Maximizing life-span when running MCU from a single battery using DC-DC converter?

texts:
I'm designing a device which will be off more than 99% of the time. The device is powered from a single AA battery through a DC-DC converter (has enable pin) and comes to life when a button is pressed. The device executed a routine and turns off.

In order to start working I'm thinking of enabling power to the MCU using the button that will latch the DC-DC converter enable pin high and after the MCU is done it will release the latch so the DC-DC enable will go low and the system will turn off. This will enable me to save the maximal battery life.

Anything wrong with this approach?

Update

Here is a latching circuit I've thought about. The user presses SW1, which is momentary, and that pulls the enable pin high. The DC-DC converter powers up and outputs 3.3V which is fed back to the enable pin and keep it high.

An N-channel mosfet is kept open using a resistor from gate to GND. This could be 200k - 500k range. When it is time to shut down the gate which is connected to an MCU pin is pulled high and that drops the voltage at the enable pin.

simulate this circuit – Schematic created using CircuitLab

Update 2
So it seems this DC-DC is a bit strange due to the diode being forward biased all the time. I've picked another device: XT1861. This has the enable switch setup a bit differently so here is an idea how to implement a latching circuit using the new DC-DC (I don't know if this actually works). The idea here is to use the switch to open the pass FET which will start the converter and that voltage will keep Q1 conducting which in turns keeps the FET conducting. Pulling the MCU's pin to ground will close Q1. That's the idea anyway...

simulate this circuit


texts: AWG 30 cable distance for 3.3V from ESP32

texts:
I'm planing to put some magnetic switches on my windows and pulling the wires up to the attic and use an ESP32 to notify via MQTT when they are opened/closed. I went to my local electronics store and bought a 250m roll of wire which I assumed was AWG 24 at least but turned out to be only AWG 30. My question is will I be able use AWG 30 cable from the ESP32 down to the magnet switch in the window which is roughly 5 meters?

Or is this wire to thin?
What size would you recommend?


texts:
Variety of IC engine manufacturers have eliminated acoustic knock sensors from recent designs. Those got replaced with Ion current sensing circuitry (feedback from the spark-plug).

In parallel, SMART Ignition Coils (those directly mounted on a smart-plug) are becoming a commodity.

Such coils normally have 3 pins:

+12V for the primary coil
Ground
+5V TTL for the control signal

The question I have is - how can Ion-current be sensed on the same control pin?


texts: Understanding how this bi-directional logic level shift works

texts:
I'm having a bit of trouble understanding how this logic level shift circuit works exactly. The design is from Sparkfun.
Hhere is the schematic:

For my application, the LV and HV are the 3.3V and 5V bus respectively. The LV1 and HV1 are the respective logic pins. I have a confident idea on how it works when LV1 is the input and HV1 is the output. However I can't seem to figure out how it works the other way around when HV1 is the input and LV1 is the output.
Here is what I know so far on how the circuit works. If LV1 is high, the voltage potential between LV1 and LV (gate of the N-MOSFET) aka Vgs is zero. Thus the MOSFET is off (open circuit) and HV1 only gets the 5V signal from HV through R4. When LV1 is low, there is a Vgs of 3.3V and the MOSFET turns on. From it, HV1 is at the same voltage potential as LV1 thus it's low.
Is my explanation correct on how the LV1 being the input works? How does the circuit work the other way around when HV1 is the input?


texts: How can I prevent microwave radiation absorption by a camera lens/electronics inside the microwave (behind the shield)?

texts:
Let's say I put in an endoscope like camera with the lens at the inside edge of the box and the wire behind metal sheet. Here's a mockup:

Possible idea: The lens is behind a holes but the hole is directly in front of lens. The lens would be facing inwards to the center from the edge of the cube. This does not seem sufficient as the radiation is being reflected off the walls so it's fairly random. Is there anyway to make it microwave safe for recording while microwave operates?
I watched some microwave tear down videos and it seems like (on a surface level view) most of the electronics are safely just hidden behind a wall. That to me suggests the heat build up isn't too high or the electronics are designed to be heat resistant. In this case the lens/camera is exposed to the radiation..
If you have any ideas/thoughts on how the lens/electronics of the camera can be protected from microwave radiation while having full view of the plate, I would appreciate hearing them.
The thought driving the question is: Would an endoscope like camera be safe from microwave radiation/energy behind the inside microwave box?


texts: Why do SparkFun make breakouts for circuit multiplexers?

texts:
I found this product on SparkFun. My first thought was "why do they need to make breakout boards for multiplexers, aren't there ready-to-roll muxes that do this kind of thing that already come in a DIP configuration"? And sure enough, there are and naturally they're cheaper than buying whole PCB (obviously that link's not from SparkFun so it's gona be cheaper, but even with SparkFun's markup the solo IC is gonna be cheaper than a PCB).

So is the breakout board just to save people from having to worry about the pull-up resistor and decoupling capacitor that it includes?


texts:
I need to design a project that it will conects to usb port, to send a digital output from the computer to other device.

I need it work in windows and mac without complex host side driver or just using a pnp generic driver.

I am reading about LUFA library
http://www.fourwalledcubicle.com/LUFA.php

I've found some references but no especific about the behavior on Mac OS X environment, just windows.

How will work a AT90USBxxxx + Lufa device on Mac respecting to drivers?


texts:
I am reading temperature from a K thermocouple on a PLC which is then forwarded to a trending software to see the data on a graph. The thermocouple is in a water trough/reservoir. In fact, there are 3 thermocouples in the trough located at 3 corners. One of them is giving erratic data as shown in the attached snapshots (blue trend) .

To check if the problem lies in the thermocouple or on the PLC connector, I disconnected the probe from the PLC and connected it to a portable datalogger. The datalogger showed consistent data (no random drops) so I am wondering if the connector is faulty. But then again is the connector really faulty if two other probes hooked to it are showing consistent data. Has anyone ever come across something like this?

Not sure if this helps but there is a water pipe pushing relatively colder water into the trough where the probe in question is located (but then again I can see this water pipe affecting the temp by 5-6 degrees C but not by a whopping 20 degrees C)


texts: Help with this Sinsusoidal steady state problem?

texts:
The question is to find the values of \$v_1\$ and \$v_2\$:

I got the following matrix:

\begin{bmatrix} 0.64 < 38.66^{\circ}  & 0.4 < -90^{\circ}\\
0.85 < 28.07^{\circ}& 0.29<210.96^{\circ}\end{bmatrix}
\begin{bmatrix} v_1  \\
v_2\end{bmatrix}
$$=$$
\begin{bmatrix} 30<-90^{\circ}  \\
0\end{bmatrix}

Which gave me the answer:
$$v_1=33.46 \cos(2t-211.49^{\circ})$$

Which is off from what the answer gives by .5 in the coefficient. Where did I go wrong?


texts: Good practice when designing a PCB and stencil?

texts:
While I generally use nothing smaller that SOIC chips or 0603 passive components, I have to design a PCB with a WSON-14 IC with tiny 0.5mm pin spacing and with an exposed pad.

While I generally use a syringe to apply solder paste I thought that, for such a small beast, I should better order a stencil with the PCBs.

Since this will be the first time I order and use a stencil, I wonder if there is any good practice to ease the alignment of the stencil and the application of the solder paste.

For what it’s worth, I’m using Kicad to design the PCB. The PCB is tiny (0.4"×0.7"), and I consider ordering to a low-cost Chinese factory (~$10 for 10 PCBs, ~$15 for a stencil).

Any advice is welcome.


texts: I have it only tied to switch via a pull-up resistor on a pic.  I'd like to not perform any hardware debouncing to save on costs, but I'm wondering if this could lead to a higher fail rate of something internal to the MCU of which I'm unaware, like how the power-on-reset circuit works.


texts: Biasing Class AB power amplifier with MOSFETs

texts:
I am having trouble getting the resistor biasing to meet a minimum 1.25W at the output:

Note, the distortion and watt meter. I was told the SPICE parameters for the FETs didn't really matter. (Although, I would like to know want to populate some values.)

Anyway, here are my calculations...probably riddled with misconceptions:

\$(P_L = 0.5V_P^2/R_L) → V_P = \sqrt{2R_LP_L}\$

\$\sqrt{2*10*2}  = 6.324 V\$ // I picked an output power of 2W.

\$V_{DD} = V_P/0.8 = 7.9 V\$

From the TC6215 complementary pair MOSFET datasheet, N-Channel Output Characteristics:

\$2.5 = K_N(5 - V_{GS(th)})^2\$

\$1.5 = K_N(4 - V_{GS(th)})^2\$

Solving for the two equations:

\$K_N = 7.78 A/V^2\$

and \$ V_{GS(th)} = 4.44 V\$ (Edited because 0.534 V is not the right one.)

_________________________________________________________

From SPICE diode because I couldn't find it on the diode datasheet: \$I_s = 2.55*10^{-9}\$

Then, the combined diode voltage:

\$ V_{BB} = (amtOfDiodes)*V_T*ln(I_{Bias}/I_{s})\$

\$ V_{BB} = ? = (3)*0.026*ln(I_{Bias}/2.55*10^{-9})\$

How do I find V_BB to solve for the bias current, to solve for the bias resistors?

I don't know what to put for \$V_{BB}\$ in this schematic:

→ \$ I_{Bias} = 4.77mA\$ (INCORRECT)

_________________________________________________________

KVL loop from top left down to load:

\$ V_{DD} = RI_{Bias} + V_{GS} + Vo\$

\$ 7.9 = R*4.77m + 0.564 + 4.47\$

→ R = 600 Ω (NOT RIGHT)

Only design specifications

\$P_L\$ > 1.25 W  (Major problem.)
Efficiency > 60%
THD < 1.5%
\$R_L\$ = 10 Ω
3dB lower frequency < 500 Hz
Supply voltages ±15 V (maximum)

Minor Question

Should an input buffer stage be added to minimize distortion:

  The voltage drop across resistor R2 provides the bias to Mn and Mp so
  that crossover distortion is minimized.

Microelectronics 4e Neamen

EDIT1

I never did figure out how to calculate V_BB (technically V_GG).

Related

Class AB amplifier Design


texts: Making a battery last a long time in a microcontroller circuit

texts:
I'm hoping to power an ATtiny85V for a nice long time on some small battery, probably a coin cell.

I've looked into the software side, and my code is watchdog timer driven, has unused analog and digital converters turned off, the chip is running at 1MHz etc.  Of course being both busy and new at this, I'm not sure exactly how much current it is drawing, but I'm hoping I have basically minimized it.

Every few seconds it wakes up, does its voltage level checks on the ADCs, records it to ram, and goes back to sleep.  If it detects a serial line is connected, it spews the data out.

However, now I'm looking at the circuit as a whole and wondering if there are things I should do to make the circuit as a whole more battery friendly?

  What are the basic dos and don'ts when it comes to designing a long lasting (simple) circuit where one component (the microcontroller) has a repetitive but variable current draw?

For instance:

Is an indicator LED a big deal?  Is it using up the battery when it is bright?  Should I put a giant resistor on it to make it dim, or does that just make the resistor use the battery?
Should I use bypass/decoupling capacitors to even out the current draw from the battery, or will the capacitor just waste the battery's power?
The microcontroller only needs 1.8V, but I don't have any 1.8V batteries.  Should I use two 1.x batteries and send it too much voltage?  Can I prolong the battery life by "not using as many volts"?  How do I do that?
Does it take extra power to check if a pin is HIGH or LOW?  Like compared to a no-op or some arithmetic, is there much additional power usage in checking one of the GP I/O pins for its state?

I vaguely know how to compute (and more vaguely how to measure) current, voltage, power, but I'm not really sure which of those things equates to battery life.  Is the important measurement of battery life in Coulombs?

I have this vague idea that batteries are full of stuff like:

charge, as in amp-hours
energy, as in watt-hours
power, as in watts

but I am not really clear on what my circuit "eats" when it runs.  I've read a fair amount of EE101 and physics textbooks, but I don't really have any lab experience.  In other words, I've read a ton about batteries, but I'm not really sure what most of it means in practice.

Do resistors use up battery life?  Do capacitors? Do diodes?  I suspect they all do, but which of the numbers are the ones that matter?  Impedance? Power dissipation? Current?  Voltage?

Is there a way to lower voltage without wasting battery?  Is there a way to lower voltage while increasing battery life?


texts: Creating big MUXes and shift registers on FPGA

texts:
I'm working on a guitar tuner project on FPGA. For this I have to pass the sound signal (16bit/1024Hz sampling) from the ADC to a FFT block but I want the FFT block to be clocked with much higher frequency than the sampling of the sound, and also I want to so some FFT overlapping. The FFT block performs the transform on 1024 samples, 16 bits for each sample.

So I want to store the sound samples in a big SIPO shift register (1024 samples, 16 bits each, which corresponds to 1 second of sound) and I want to pass it to FFT block every 1/8 of a second (every 128 samples) using a big MUX (1024 of 16bit-width buses, so over 16k connections between SIPO and MUX). Every 1/8 of a second the ADDR bus would scan through a MUX (and pass the whole shift register data to FFT block) with a frequency much higher than the clock of the SIPO block.
See the picture.

Is this way of making it viable?
Is there any example of implementation of such blocks (preferably in Verilog)?
Would it fit in my already heavily utilized Cyclone II EP2C35F672C6N? I've already implemented most of the project (including FFT block), see the compilation report below.
Is there any better way of doing it?


texts: Determining which pulse came first on an FPGA

texts:
I try to determine which of two asynchronous pulses came first (after a synchronous reset) using an FPGA. The pulses are asynchronous because they are generated from ring oscillators (running on the FPGA and not synchronized with the system clock).

I want to use as few resources as possible. Should I use a latch or some flip-flops like below?

 source

I am looking for a solution where the output stay stable even if subsequent pulses are generated.


texts: STM32F4 output on PD15 creating an unwanted PWM signal on PD9

texts:
#include "stm32f4xx.h"
        #include "stm32f4xx_hal_def.h"
        #include "stm32f4xx_hal_rcc.h"
        #include "stm32f4xx_hal_gpio.h"

        int main(void) {
        uint32_t  S1S2, S11S12,S21S22,S31S32,S41S42,S51S52,S61S62;
        uint32_t  comp1,notComp1, comp2,notComp2,comp3,notComp3,inj,notInj,ssgn,notSsgn;

          //Define the structure
         GPIO_InitTypeDef GPIO_InitStruct;

//Start the clock on port D
RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN;

//Configure the GPIOD OUTPUT pin registers
// port D OUTPUT PIN
GPIO_InitStruct.Pin =
        GPIO_PIN_15  //s1 s2
        | GPIO_PIN_14 //s61 s62
        |GPIO_PIN_13 //s51 s52
        |GPIO_PIN_12  //s41 s42
        |GPIO_PIN_11 //s31 s32
        |GPIO_PIN_10 //s21 s22
        |GPIO_PIN_9; //s11 s12
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
GPIO_InitStruct.Pull = GPIO_PULLUP;

HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;

    //Configure the GPIOD INPUT pin registers
    // Port A INPUT PINs
GPIO_InitStruct.Pin =
GPIO_PIN_15   //COMP 1
|GPIO_PIN_14  //COMP 2
|GPIO_PIN_13; //COMP 3
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
GPIO_InitStruct.Pull = GPIO_PULLDOWN;

HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;

    //Configure the GPIOD INPUT pin registers
    // port B INPUT PIN
GPIO_InitStruct.Pin =
GPIO_PIN_15 //Ssgn
|GPIO_PIN_14  //Sinj
|GPIO_PIN_13; //Sinj-
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
GPIO_InitStruct.Pull = GPIO_PULLDOWN;

HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

while (1)
    {
                notInj = ~GPIOB->IDR&GPIO_PIN_14;
                notInj = notInj << 1;
                comp1 = GPIOA->IDR&GPIO_PIN_15;
                notComp1 = ~GPIOA->IDR&GPIO_PIN_15;
                ssgn = GPIOB->IDR&GPIO_PIN_15;
                notSsgn = ~GPIOB->IDR&GPIO_PIN_15;
                comp3 = GPIOA->IDR&GPIO_PIN_13;
                comp3 = comp3 << 2;
                notComp3 = ~GPIOA->IDR&GPIO_PIN_13;
                notComp3 = notComp3 << 2;
                inj =  GPIOB->IDR&GPIO_PIN_14;
                inj = inj << 1;
                comp2 = GPIOA->IDR&GPIO_PIN_14;
                comp2 = comp2 << 1;
                notComp2 = ~GPIOA->IDR&GPIO_PIN_14;
                notComp2 = notComp2 << 1;

 ///////////////S1S2//////////////////////////////////////////////////////////////////////

        S1S2 = notInj;
        GPIOD->ODR = S1S2; //output is now on pin 15
  /////////////////////S11S12////////////////////////////////////////////////////////

        S11S12 = ((comp1&notComp3)&(ssgn&inj)) | ((notComp1&comp3)&(notSsgn&inj));
        S11S12 = S11S12 >> 6;
        GPIOD->ODR = S11S12; //output on pin 9
   }
}

When i flash this code to the board and connect the oscilloscope to Pin 9 i get a PWM signal when i should be getting a straight line for DC voltage if i however comment out  //GPIOD->ODR = S1S2 i get a straight line in the oscilloscope as i should.

inputs PA15 HIGH, PB15 HIGH and PA13 HIGH everything else low.

If anyone understands what im doing wrong id appreciate an answer thanks in advance.

should be getting a straight line not this.
http://imgur.com/gallery/YBWom


texts: Why don't these even/odd mode transmission line results math up?

texts:
In Pozar's Microwave Engineering, he analyzes the Wilkinson power divider using even-odd mode analysis. His results match the expected values and power conservation is satisfied. Similar derivations can be found online. Here's where I'm losing the analysis.

Consider a line of 1 ohm feeding a quarter-wave transformer of impedance sqrt(2) ohms, leading to a load of 2 ohms. This results in a matched input,
$$ \Gamma_{in} = 0 $$
The transmission coefficient for the transmission line, confirmed by simple algebra as well as simulation, is
$$ T_{load} = -j $$
Where the subscript load indicates that this is the output transmission coefficient, S21. Using this result, we would expect to be able to write
$$ V_{load} = TV_{inc} $$
Or, for a coordinate system in x from the input port x=-lambda/2 to the load at x=0,
$$ V(0) = TV(-\lambda/4) = -jV_0$$
for amplitude V_0 i.e. the output voltage is a phase-shift input voltage.

This result in incorrect, however. The transmission coefficient is correct, but the output voltage is not found by it. The output voltage, V(0), can be shown to be
$$ V(0) = -j V_0 \sqrt 2 $$
Which is scaled up slightly from the incident voltage. The reason, in short, is that by assuming:
$$ V(x) = V^+ (e^{-j\beta x}+e^{j\beta x}\Gamma) $$
We use V(lambda/4),
$$ V(\lambda/4) = j(1 - \Gamma) = V_0 $$
And V(0),
$$ V(0) = V^+ (1 + \Gamma)$$
And we find
$$ \frac{V(0)}{V(-\lambda/4)} = -j \frac{1+\Gamma}{1-\Gamma}$$
Where Gamma is the reflection coefficient at the load. Then we arrive at
$$ \frac{V(0)}{V(-\lambda/4)} = -j \sqrt 2$$

So what happened? Where is the problem with the first derivation, and why in the second are we allowed to assume a matched input but that the load voltage will depend on the load reflection coefficient, when any analysis of a quarter-wave transformer is in some way based on multiple reflections, which makes this a strange idea?


texts:
$$R_1=27kOhms ,R_2=56kOhms,R_3=50kOhms,V_s=5V$$
I'm trying to find the current thats flowing through R3, what i did was to convert the voltage source and resistors R1+R2 into a current source and then i use current divider formula to solve R3: I3=Is((R1+R2)/(R1+R2)+R3. Is that correct?


texts: Required Emitter Resistance \$R_E\$ for the Maximum Emitter Current for a BJT

texts:
I need some help. This can be a dumb question as I am not an electrical engineer nor an electronics engineer, but need to solve a problem as given below. I tried to solve it but not sure if it is true because spice simulations give different result.

Where is my mistake?

Problem

Choose Emitter Resistance \$R_E\$ for the given problem for the max Emitter Current \$I_E\$ that is possible. Take \$\beta=100\$.

My solution approach

\$I_C=\frac{V_+-V_{out}}{R_c}\Rightarrow V_c=R_cI_c+V_0\\
I_E=I_B+I_C=(\beta+1)I_B\\
\\
\frac{V_{out}-V_{CE}+V_+}{R_E}=I_E\\
\\
\frac{R_CI_C+V_+-V_{CE}+V_+}{R_E}=I_E\\
\\
I_C=\left( \frac{\beta}{1+\beta}\right)I_E\\
\\
\frac{R_C\left( \frac{\beta}{1+\beta}\right)I_E+V_+-V_{CE}+V_+}{R_E}=I_E\\
\$

which gives

\$
I_E=\cfrac{2V_+ -V_{CE}}{R_E-R_C \cfrac{\beta}{\beta+1}}
\$

for the maximum current \${R_E-R_C \cfrac{\beta}{\beta+1}}\$ should be zero, thus,

\${R_E=R_C \cfrac{\beta}{\beta+1}}\$


texts:
I build according to the block diagram, where I am only allowed to use integrator,  summing amplifier and inverting-buffer. I build accordingly with the block diagram that I got but *I am not sure what did I do wrong and why it did not come out with the expected result below I check all my calculation multiple times which I am pretty sure it is correct, so now I am not sure what's wrong with the circuit design and how do I solve this.

Original Transfer Fucntion

Expecting Result

Block Diagram

Design Circuitry In LTSPICE

LTSPICE Simulation Result


texts: How do I find Vs in this circuit with a 2:1 ideal transformer?

texts:
How do I find Vs given that V0(to the left) is 10L30degrees? I started by finding that the current on the 10 ohm resistor is 1L30 degrees, and then using kirchoff's law, the current on the tranformer is 4,2L-82 degrees, satisfying:
I = 1 L 30
V0 = I * (j4) + (I - cap_I) * (-5j)
I_on_trans = - I_on_cap + I
I think I messed up at some point.


texts: Can I resolve a spice netlist to determine what parts I need?

texts:
I have used hierarchical schematics in my design, so I can't really "see" anymore what's going on behind the scenes. I want to figure out how many of which parts I need...

I figured that perhaps the easiest way to do this was by looking at the netlist. However, the netlist includes subcircuit definitions, so if I do a search in a text editor for the model name, it doesn't come up with the right number.

Is there a way to resolve a netlist to get rid of the subcircuits? For example, if this is my netlist:

V1 N001 0 12
XX1 N001 N002 CIRC1
XX2 N002 0 CIRC2
.SUBCKT CIRC1 A B
R1 A P001 10k
R2 P001 P002 100k
R3 P002 B 10k
.ENDS CIRC1
.SUBCKT CIRC2 A B
R1 A P001 10k
R2 P001 P002 50k
R3 P002 B 10k
.ENDS CIRC2
.END

Can I resolve that into:

V1 N001 0 12
R1 N001 P001 10k
R2 P001 P002 100k
R3 P002 N002 10k
R4 N002 P003 10k
R5 P003 P004 50k
R6 P004 0 10k
.END

Or am I daft, and there is an even easier way to do this?!

Thanks for your help!


texts: Basic Circuit Question: Understanding the area under the v(t) curve?

texts:
Basic EE/Circuit Question: Does the area under the V(t) curve = total joules (expended energy)?
Lag


texts: How does an op-amp work without proper power supply?

texts:
I have built a chua's circuit following this diagram:

Source: Kennedy 92(pdf). The rectangle inside NR is and eight pin dual opamp.

Then, I remove the 9V battery on the right. It is replaced by a break. As a result, the negative power supply of the opamp (V- on diagram) is not connected to anything else.

I then use an oscilloscope to measure the voltage across C1. The scope shows an almost perfect sine wave.

Question: how can a opamp supply power to the rest of the circuit if itself is not properly supplied by batteries? Why is it a sine wave?

To be a sine wave, the components should be linear. So what's the voltage-current characteristics of NR after removing the battery?

PS: I use TL082 opamps.


texts: very low stall current in geared 12V DC motor

texts:
I bought a small brushed (my guess) DC motor with integrated reduction gears off Banggood: here's the link to the product page:
https://www.banggood.com/12V-DC-3RPM-High-Torque-Electric-Geared-Box-Motor-p-989186.html

Since it comes with no sort of technical data, aside from the rated rotational speed and voltage (3rpm at 12V with no load), I wanted to investigate more on it, so I measured the running current draw with no load, and the stall current by mechanically blocking the shaft and using a multimeter in "Amp mode". I'm a complete noob so I just followed this guy's tutorial:
https://www.youtube.com/watch?v=gwFE-NkzR-k

Although I haven't really measured the rpm to check if they match the rated value (speed is not a concern), the motor works just fine, but what I got was:

a no-load current so low it could not be detected by the multimeter (below 10mA)
a stall current of approximately 40mA.

It would have seemed fair enough to my inexperienced eyes, since 12V*40mA=0.48W, it kind of made sense to me! But in that same tutorial I mentioned, as well as on a handful of other internet sources, I saw the value of the stall current ranging around 500mA for similar motors. Now I understand that "similar motors" is not really a valid definition, nor a good means of comparison, given that they can vary a lot in behavior even if they have, say, the same rated voltage, and also when I don't really have a datasheet as a reference to make such comparisons in the first place.

I just wanted to know if those numbers, especially the 40mA stall current, are plausible even to more expert eyes than mine. I also hope I was clear enough for you to express a judgement.

This is really all I have to give you, and I do not have any other multimeter to double-check these figures I am getting. Thanks everybody!


texts: Question about RC charge-discharge curve

texts:
I found the following image on electronics-tutorials.ws:

Isn't this wrong? Shouldn't the voltage rise faster during the first 2T than that it decreases during the next half period? I think so because the voltage difference at t=0 is Vc, which is higher than the voltage difference at t=2T. Shouldn't the triangle wave ultimately go halfway Vc(max), with difference distributed evenly below and above the curve?
(I hope I make myself clear.)


texts: Can you get values of the components in the circuit?

texts: I have a mosquito repellent circuit diagram (voltage doubler) with printed values. Can anybody find the actual component value of the capacitors?


texts: Could a barcode scanner be used to get surface depth information?

texts:
(if tl;dr, go to the part where it says "actual question")

this is probably a very obscure question, but: I'm working on a rather complex art installation with computer-generated sculptures, and I'm looking for a way to extract the "depth" information of their surfaces, in other words, how "jagged" is the surface at any given point. Surface deviation would be in the range of millimetres, up to a couple of cm.

I'm considering IR-based distance sensors such as Sharp GP2Y0A60SZLF, but I see two main issues with these:

I can't tell exactly which point, or series of points, is currently being scanned.
I can only get one value at a time, while being able to extract a sequence, or a "buffer" for a chosen line on the surface, would help me a lot.

The actual question:
Could I in theory use a barcode scanner (either CCD or laser) to obtain a sequence of depth values for a particular part of the surface? The idea being, if the scanner measures the intensity of reflected rays, wouldn't that also tell me how far they must have travelled?

FYI, it's acceptable for me to hack the reader and bypass the MCU to simply obtain the raw data from the sensor.

Thanks a lot for any help!!


texts:
How to choose TVS diode?
What's clamping voltage?
If in case TVS diodes clamping voltage 57V if anything more than 57V what will happen to diode and circuit?
Would it break? Or pass the voltage?


texts: Texas Instruments Step-Down DC-DC Converter orientation

texts:
I have a Step Down DC-DC Converter IC, purchased from Texas Instruments.
Part number: TPS54331
Datasheet: www.ti.com/lit/ds/symlink/tps54331.pdf?ts=1599690098737&ref_url=https%253A%252F%252Fwww.google.com%252F
IRL Image:

PCB Footprint -

Does the line signify the pin 1 ident?
All my other components have an ident. I am sure this information would be somewhere but I just don't know the words to use. Thanks!


texts: Distribution of Current in Kirchoff's Junction Law

texts:
I know that Kirchoff's law says that the incoming current is equal to outgoing current.

But I want to understand his: suppose we have 4 wires like the one in diagram.

So let us consider current i1, comes to the junction and gets split into three direction towards i2, i3, i4 and similar is the case with current i2 but then why we imagine only the current i3 and i4 as outgoing current whereas current is also going to i1 and i2.

May be I am missing something but I am stuck on this problem for very long.


texts: How can I tune an antenna for receiving (VHF)?

texts:
I have a number of books on antennas and without exception they all describe balancing antennas only for transmission. Since I do not even own any transmitters these guides are useless.

I have only receivers. How do I tune an antenna for receiving? Mostly I am interested in the VHF frequencies, but also UHF sometimes.


texts: How many ALUs (and threads) are in a Pentium CPU?

texts:
I'm reading a book bottom up where it said:

  The Arithmetic Logic Unit (ALU) is the heart of the CPU operation. It
  takes values in registers and performs any of the multitude of
  operations the CPU is capable of. All modern processors have a number
  of ALUs so each can be working independently. In fact, processors such
  as the Pentium (*emphasis by me)  have both fast and slow ALUs; the fast ones are smaller
  (so you can fit more on the CPU) but can do only the most common
  operations, slow ALUs can do all operations but are bigger.

I started to find out how many and found that question https://stackoverflow.com/questions/29056968/how-many-alus-are-in-a-cpu where as far as understood many ALU referred to multi-threading, but Pentium is single threaded.

Here I've found Are 32-bit ALUs really just 32 1-bit ALUs in parallell?. So I guess what was meant in the book is kind of many parallel "small" ALUs - am I right?


texts: Charging batteries in parallel when they are connected in series in the circuit

texts:
I've got two LIR2450 rechargeable 3.6v coin cells. These need to be connected in series to form a 7.2 volts which is being regulated down to 5v to power an ATMEGA328P. I need to charge the two batteries using a USB power supply. As USB can only supply 5v, I can't use this to recharge the two batteries when they are connected in series, as this would require a 7.2v source.

I've found a charging circuit which works well on the LIR2450. If I can have the two batteries connected to this in parallel, it should work, but I can't figure out how to change the connection from series to parallel when the USB is plugged in.

Here's a picture of what I've got so far:

Basically, when the switch is off, and the USB is plugged in, the connection between the batteries needs to become parallel, and remain this way until the USB is unplugged. Any suggestions?


texts: How do I reset a capacitor once I have a signal rise?

texts:
Once the signal rises to a certain level, my capacitor starts getting charged.

Once the signal falls back down to that same level, my capacitor stops charging.

This way, I am using the voltage of my capacitor as an indication of how long the signal stays above that level. I call this time duration as "hump duration".

My problem is, I have a train of such pulses. That means, after the 1st hump comes the 2nd hump and so on. In order to also get the "hump duration" of my 2nd hump, I believe I will have to reset that capacitor.

So how can I reset my capacitor when my signal rises above a certain level (i.e., right before next hump comes)?


texts: Current limiting; super cap charging a lithium ion battery

texts:
Please advise me as to whether or not a current limiting circuit such as this one :

http://www.next.gr/circuits/Variable-Adjustable-Current-Limiter-Circuit-l23013.html

would be the ideal choice for my goal of charging 2 parallel lithium ion batteries with a string of super caps.

My circuit :

1). 7.2 vmax, 210 F super cap string  >>

2). Boost convert to 8.4 volts output with a max of 5 A ouput when lithium ion batteries are at a minimum charge of 6.5 volts(i measures the output current with the battery load at 6.5 volt charge level >>

3) current limiter, limit current tfrom 5 A to maximum battery charge rate of 2.4 A ( one battery max charge rate is 1.2 A but I have two in parallel for a 2.4 A charge rate)

4). Load: (2) 8.4 Vmax lithium ion batteries in parallel.

Any advice would be appreciated. I would like to do this efficiently and without the use of resistive current limiting.

Thank you,

Tom


texts: Voltage difference between two individual voltage sources

texts:
I have two voltage sources. The first one is 230VAC to 5VDC cell phone battery charger while the another is output from Raspberry Pi's Ground and 3V3 pins.
I feed the 5VDC output for an Arduino. What I am planning to do is to connect RPI's Ground pin to the corresponding pin of the 5VDC's Ground pin. That's how I would make a reference 0V voltage for data connection between RPI and Arduino. I don't have a voltage level shifter (these allow two different Ground references to be used) to do that easily.

However, I measured a voltage difference of 0.06 Volts between the Ground pins. I think it's little, but where does it come from and is it safe to connect the ground pins?
I measured voltages between RPI's 3V3 pin and 5VDC's Ground pin, and vice versa and results were similar in these situations as well.


texts: How does a Dual-Port Wall Charger distribute Amperage output?

texts:
I recently bought a Dual-Port Wall Charger that has a '3.4A total output'. Assuming the device(s) plugged in are individually capable of charging at 3.4A, is this specifying that a single device plugged in can charge at a maximum of 3.4A, while two devices plugged in will charge at 1.7A each? Or will each port always charge at 1.7A? Or will each port always charge at 3.4A?

Does 'total output' in the way described vary between manufacturer/device, or is 'total output' an industry standard?


texts: A question on using potentiometer as a variable resistor

texts:
I have a 10k poti. I use it as a variable resistor by soldering two of the three terminals. It is connected to a 1/4 watt 220 ohm resistor in series(this is the load). The voltage across this circuit is 12V DC.

Is the poti safe even it is set to zero ohm?
Would 220 ohm prevent it to burn  in this case?
If so, what should be the quantative method to calculate the minimum value of series resistor which would prevent this poti?


texts:
So you know how you can create an electromagnet by winding copper into a solenoid around a metal nail and sending current through it?

Is it possible to do this with conductive thread instead of copper?


texts: How to tell if frequency or the radian frequency

texts:
The question is as shown below:

My question is about Problem 7.2 d) The frequency at which maximum current occurs in problem 7.2 c) is as shown in the figure below:

However, the answer of the book is

My question is how do I know if he is asking for the frequency or the radian frequency (i.e. angular frequency).


texts:
What is the need for Buffering signals ? Is it to provide the ability for the source or circuit to be able to provide high current amount ?
The buffer I was reading was the Op Amp unity gain amplifier.


texts: How do I make an edge triggered T flip flop using integrated injection logic (I2L)?

texts:
I have been searching everywhere online on how to make this circuit. I found out I can make NAND gates using I2L and connect them together to make a T flip flop , but this is very impractical since I will end up using 48 transistors.
I found a circuit for a negative edge triggered T flip flop using Bistable multivibrators .

I connected the circuit in Multisim and tested it , and it gave me the correct output for a T flip flop.

I figured that in order to make it I2L I have to replace every resistor in the circuit with a pnp bjt transistor ( 2n3906) as a current source and it should work, but it ended up giving me a really weird output.

I also came across a different circuit from 1980 of a "Triggerable flip flop" using I2L , but it used multi-collector npn bjt transistors and I don't know to make these. (https://patents.google.com/patent/EP0032154A1/en)

Please help me either fix the circuit I made so it works and tell me how to make a multi-collector npn bjt.
Thank you


texts: Connecting two similar, equal voltage batteries in parallel

texts:
I am trying to increase the range of my son's child electrical vehicle.
It came with a 12V 10Ah battery.
I bought a second one, which is 12V but 12Ah. It may have other differences too, but it looks very similar, has the exact same size, etc.
Can I put these two in parallel? Some sources say that the voltage has to be the same other sources say everything must be exactly the same.
Furthermore, can I also use the built-in charger to charge both at the same time or do I have to modify it somehow? Again I read different opinions about this. Some say it will just take twice as long to charge others say this charger is too basic and it won't work in parallel for charging.
Do I need to put fuses between the batteries?
Here are some photos:
Original battery in the car:

New Battery:

Charging:


texts:
I'm trying to make a line following robot using Arduino. I have searched the Internet for information on how to build it, but a few questions remain:

How does an IR sensor detect colors?
What voltage range do those sensors output when detecting these colors (especially black and white)?


texts:
I'm new to electronics, and I'm currently building my electronics area. Let's say that I have an ESD bench mount drilled into my wooden workbench, and this ESD bench mount is then connected to the "ring" of the power outlet. Prior to attaching anything to the power outlet, I used one of those power outlet voltage testers, which indicated that it was functioning correctly. I then have my wrist strap connected to the ESD bench mount.
Now let's say that there is a lightning storm. In such a situation, are there any additional risks to human or electronics safety? Is there anything that I need to be mindful of in such a situation? Should I behave differently in such a situation?


texts: I'm fairly new to PCB design and I was wondering what the best step-by-step selection process is for component selection. I'm trying to create a battery-powered sensor with humidity, temperature and movement sensors. What steps can I undergo to find the best and most efficient components?


texts: How does vacuum tube heating (heater voltage) affect tube performance/sound?

texts:
I have replaced a 12AX7 tube with ECC85 in my guitar amp.  Seems to work great and sound great.  The part that is questioning me is whether the sound is being at its best because it takes a good 20-30 seconds before the volume reaches a good level.  This is probably because original heating gives 6.3v at only 300ma and the tube needs about 400ma.  It works but the question... will it sound any different? better? How will it affect the tone of the vacuum tube?

In other words.  Having lower voltage than recommenden on heaters - good or bad?


texts: How to simulate platformIO project in Proteus

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My project in PlatformIO is composed of folders. Proteus simulation code structure is flat single folder for code and another folder for headers.
How can i move .cpp and .h folders to proteus for editing and simulation?


texts: Array of 4x7 Segment displays using demultiplexer. Need PNP transistors!

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My first post here! I'm that most dangerous of EE-wannabes—a software guy with theoretical knowledge: V=IR, and transistors come in two flavours: "NPN" (1=On) and "PNP" (1=Off)

Introduction

@stevenvh almost answered my question in this beautiful answer, except that I want to gang up four 4x7 segent displays - and use two demultiplexers rather than discrete selection pins. I've repeated his diagram here:

My basic values

5V supply
Common cathode displays
Blue LEDs with 3.0V drop @ 20mA

My problem

My problem is that I can't get hold of 74LS238 (3-to-8 demultiplexers, decodes High), I can only get 74LS138 (3-to-8 demultiplexers, decodes Low). That is, all outputs except the decoded one are High.

That means that I need to use PNP transistors rather than NPN in his diagram, and put them in "upside down" (collector to ground).

My questions

Is that all I need to change?
Which PNP transistor would you recommend?


texts: op-amp differential amplifier - output is the same with Vcc

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I'm tring to use a OP-AMP LM358P as a differential amplifier.
The circuit I'm using is like below;

According to what I've study and expectations of SPICS, the out-put should be about 2.5(V1-V2). To be specific, I would V1, v2 will be 0~3.3V and the expected output is proportional -8V~+8V. However, the actual circuit provides constant V which is the same with Vcc voltage; actually bit less than the Vcc when I tried with 12V and 24V as Vcc.
So, what could be the possible cause that makes the circuit does not work as expected?


texts: Time constant for RC common emitter circruit

texts: Here is a simple circuit for common emitter. Is the time constant for charging  \$C_1\$ equal to \$C_1R_2\$? It doesn't seem logical that \$R_1\$ would influence the charging of \$C_1\$, since it's connected to ground.


texts: How does voltage progress during discharge of a battery?

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The build:

I'm building a portable bluetooth boombox.
It's a very simple build. The components I'm using are:

Bluetooth amplifier board (TDA7492P)
2x50W speakers
Rechargeable battery

The amplifier needs to receive 12V. So the battery I will get will be able to deliver this voltage.

My questions:

Now before I buy the battery I have 2 questions that come to my mind.

Will the voltage at the terminals of the Amp be 12V for the entire discharge of the battery or do I need some kind of a voltage regulator?

My other concern is the autonomy of the boombox. I want to be able to combine 2 batteries to double the battery life of the device.

Is there a way I can put together 2x12V batteries and obtain double the autonomy? But keep the voltage to 12V. Do I need to connect them in series or in parallel?

As you can guess i'm new to electronics, and any help would be very much appreciated.


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I am trying to control the force of a solenoid. My current system has a bank of capacitors connected to a relay. In order to control the force (how hard I am trying to hit the object) I am increasing or decreasing the the time the relay is on. The problem is this works but it either hits with too much force or way too much force. I can turn the relay on for 5 ms or more. If I try to turn it on for 1 ms it does not even respond. (I am using a mechanical relay.)

I would like to have more control on how much of the energy I discharge so I can control how hard/soft the solenoid moves (say discharge only 10 percent of the total energy stored so it hits slower). While searching I found out about Solid State Relays which according to wikipedia can be switched on an off way faster that mechanical relay (of the order of microseconds to milliseconds).

So my question is am I on the right track? or is there something better to achieve what I am trying to achieve?


texts: Can the transient response of a system be calculated using FFT and inverse FFT?

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I have a system, its input and output has the following relationship.

I want to know the transient response of the system with respect to a ramping input Xi=t,
by solving the differential equation,
the response I obtained is

Xo= t-sin(t);

Now I want to obtain the transient response using another method,

i.e. first decompose the input signal into a series of sinusoidal signal

then calculate the system response of each sinusoidal signal

at last sum up all the responses of sinusoidal signal.

This method involves using FFT and inverse FFT. The detailed steps are

Calculate the transfer function of the system G(s). Substitute s=jw, this way I can get the complex number G(jw) with respect to each frequency w.
Process input signal using FFT to obtain the complex number with respect to each frequency component.
multiply the complex number in step 1 and 2 for the same frequencies.
using  Inverse FFT to process the results obtained in step 3 to recover the signal in time domain.

I expected I could obtain the transient response using this method and the result should be same as the one I calculated by solving differential equation in time domain. But in reality, I was stuck at step 1. Because the transfer function of the system is

I found that at w=1 rad/s, this G(jw) is infinite. This means that if the input has a frequency component of 1 rad/s, going through the system (step 3), the amplitude of this frequency component will be amplified to infinite. Obviously this will lead to a transient output different from the one I got earlier.

Can anyone point out where I did wrong? If everything I did is correct, does that mean we can't obtain transient response by using this frequency analysis method?


texts: What is the difference between a zener diode and a precision voltage shunt? From the name I am guessing that the precision voltage shunt is more precise. I am using the shunts to limit the output of a sine wave generator.


texts: I2C signal and power over long range (10meter cable)

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After some reading/testing I managed to make stable communication between 2 devices using  I2C with FTP CAT5 copper twisted pair cable.

Green wire - SCL
White/green wire - GND
Blue wire - SDA
White/blue wire - GND

GND is connected only at one cable end, I2C bus clock is at 10Khz and I have used 10Kom pullup resistors to VCC

It works well and stable. When I decided to use other 2 pairs of the cable for power (+12V), it stopped working. I tested +12V on one pair GND on the other pair, also +12V/GND on same pair: same result, it stopped working. Whole I2C bus stopped working, other devices attached to it too.

Wonder if I can use same cable or go to safest choice - another cable for power.


texts: Can I use a MOSFET switching circuit to trigger a digital input (that reads +24 V as high) with an Arduino Mega 2560 R3?

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Its my first time posting.
I need to trigger a digital input pin on an industrial KUKA robot with an arduino. The pin reads +24 V as high. I'm using the circuit below. It consists of an IRL520 N-channel MOSFET and a 1K resistor. I'm using an Arduino Mega 2560 R3, however I'm aware the arduino digital pins output max 40 mA and +5 V. So my idea was to use the +24 V power supply (located in the electrical cabinet of the KUKA robot controller) and connect that to the drain of the MOSFET, then use my arduino's 0-5 V digital signal (from pin D11) to "switch" the MOSFET on/off and, subsequently, "switch" the digital input on/off on the robots IO module. So technically, I'm using the robots own power to trigger its own input. My questions are: 1. Is this a viable way to do it? 2. Is the resistor necessary to draw the current towards the pin? 3. Besides a relay is there any other way to do it with a MOSFET, specifically?
Thanks


texts: Micro controllers with high speed switching capabilities

texts: I am planning a ESC for use with a 5500KV brushless motor, running on duel 4 cell Lithium Polymer batteries, I have noticed that in most speed controllers they use an Atmega to control the switching of the Mosfets, Is this a good controller to use for this purpose or should one use a better more suited controller, thats designed for high speed switching?


texts: Quantization noise and Quantization error

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What is the difference between the quantization noise and quantization error in ADC?

I understood that the quantization error you get when you convert analog to digital and quantization noise when you convert from digital to analog.