texts: Power servo with lipo battery with XL6009

texts:
I'm trying to make a uselessbox, so I have:

An Arduino Nano (Chinese model with CH340 driver)
2 SG90 9g servos
1 switch

Everything works fine when the Arduino is plugged in to USB, but when I'm trying to use an 18650 battery (2200mAh) the servo doesn't want to move, or just make weird moves.
My battery (taken from an old laptop) is wired to a TP4056 module, and to a boost converter (XL6009 4A maximum.)

I tried to wire the battery without the TP4056 module, but it is the same result.
After many tests, it seems the problem comes from the boost-converter.
When I power the boost-converter from a power bench supply, (3.7V, 5A max),
no matter how I set the output (from 5V to 9V), each time the servo moves, I have a current drop, and sometimes can even reboot the Arduino.
My boost-converter is a XL6009, and should handle 4A maximum.
Maybe should I add a capacitor? I only have 100µF, is this enough?


texts:
A circuit that has 3 power sources connected in series, where

V1 = 0.2A at 20V

V2 = 0.05A at 5V

V3 = 0.2A at 20V

Diagram:

simulate this circuit – Schematic created using CircuitLab

V1 & V2 are in opposition to V3, problem here is that V2 has higher current. I could not predict the outcome correctly(probably catastrophic). However, considering that V3 is connected in series and opposing V1&V2, maybe it could cancel out with V1, leaving V2's current flow of 3A at 5V at point "A"?


texts: Can I do this tutorial without a potentiometer?

texts:
I am trying out online tutorial to practice python and Raspberry Pi.
I am currently following this tutorial.

It says a potentiometer is needed, but I don't have one. The lcd I have is JHD162A

What will happen if I connect the circuit exactly the same but without a potentiometer?
Will it destroy my Pi or will it not work?


texts: How can I handle a low power condition with PIC?

texts:
I am working on a project that uses a PIC24F mcu.
The power to my pic is backed by a very large capacitor (1F).
When there is a main power loss, I can sense that immediately via a port pin but the PIC itself stays powered for several minutes via the capacitor as the charge in the cap slowly dissipates.

Once I detect that the main power is cut, I want to perform some actions (several micro seconds only) and then stop the PIC from doing anything else (sleep or hibernate i guess). But as the caps charge slowly dissipates the power to the pic will VERY slowly decrease below 3.3V down to zero.  At any point, if the main power is re-applied, the pic should detect it at the Port Pin, and restart normal operation. I am wondering what would be the best way to handle this in software? I know that the PIC has  Brownout detection and some kind of Low Voltage Tracking but I don't quite understand how to use them.


texts: I'm trying to identify the manufacturer of this chip

texts:
Does anyone recognize this logo?  Just trying to find out who made it.
Thanks


texts: 2nd order differential circuit, converting to S

texts:
when converting to S domain, the general rule (1/LC)i = 2*t*
how come this does not equal to 2*i* just like (1/LC)iL = 2*i*L?

thanks in advance for any help


texts:
Before I start: I do not have a lot of experience in electrical engineering so I would appreciate clear statements and extensive explanations to be able to follow your ideas.

I am currently trying to build my own light bulb. The idea is to have a thin Pt wire that I bend such that it shows some letters. The wire shall than be placed in a sealed glas filled with argon and heated by current such that it glows with a red color. The power supply should come from the wall socket (230 V). The problem is, that the wire is much to short because it is not coiled as in conventional light bulbs. Consequently, the resistance is to low and I get a short.

The length of the Pt wire is approx. \$1\$ m, the temperature I want to achieve is \$800-1000\$ °C, the diameter of the wire is \$1\$ mm, the resistivity of Pt is \$\rho = 10.6 \cdot 10^{-8}\$ \$\Omega \cdot\$m and the temperature coefficient is \$ \alpha = 0.003927\$ °C\$^{-1}\$.

Thus I get a resistance at \$1000\$ °C of

\$ R = R_0 \cdot [1+\alpha(T-T_0)]\$ with \$ R_0 = \rho \frac{l}{A}\$; \$A = 7.85 \cdot 10^-7\$ m\$^2\$; \$T_0 = 23\$ °C

\$ R_0 = 0.134 \$ \$\Omega\$

\$ R(1000°C) = 0.652\$ \$\Omega\$

Do you have a cheap solution how to get the wire glowing without getting a short?

I thought of using a large number of resistors (100-1000) with low resistance  in parallel after the wire. This will decrease the current and the resistors won`t heat to much. What do you think of this idea. Is there a practical way to this?


texts: Finding the average and RMS value of this signal

texts:
How can I find the RMS and the average voltage of the following diagram?:

My work:

The RMS:
$$\sqrt{\left(\sqrt{\frac{1}{3\times10^{-3}}\int_0^{3\times10^{-3}}\left(\frac{5000}{3}\cdot t\right)^2\space\text{d}t}\right)^2+\left(\sqrt{\frac{1}{10^{-3}}\int_0^{10^{-3}}5^2\space\text{d}t}\right)^2+\dots}\tag1$$
The average:
$$\frac{1}{10\times10^{-3}-0}\cdot\left\{\int_0^{3\times10^{-3}}\frac{5000}{3}\cdot t\space\text{d}t+\int_0^{10^{-3}}5\space\text{d}t+\dots\right\}\tag2$$

  Am I right about my work?


texts: Why would I run a rail-to-rail input opamp with its inputs at the rail even if higher voltage supplies are available

texts:
Recenetly I was looking over the datasheet of an Analog Devices AD5547 DAC, and noticed the following in the application schematics (page 15):

Now what interests me here is U2. The purpose of U2 is to provide a negative reference voltage. As R1A and RcomA should be equal, and the positive terminal of U2 is at ground, in order to cancel out the currents it must supply -2.5 V at the output.

However, the positive supply of U2 is connected to ground. This is a rail-to-rail input amplifier, so this is within specifications. However, we can also see on the left that a +5 V positive supply availabe.

Apart from power consumption (it is likely the opamp will draw more current when it has a larger supply voltage), is there any reason why we would want to have the inputs sit against the rails? (perhaps so we are only using one of the two input pairs internally or such?)


texts: Driving MOSFETs with Bootstrap connections

texts:
I'm designing a type of a buck converter which has the following circuitry.

Simulation runs fine on PLECS and I've added three bootstrap connections to drive these high-side MOSFETs (All top three except FETD2). Simulation results to capture voltages across those capacitors is as follows;

I have following questions to clarify before I build this circuit on a PCB.

Is the voltage between each gate to source is enough to drive each MOSFET (Probably a Logic type MOSFET)?
In simulation, when I use the same 12V source to bootstrap circuit, it throws an error "Cyclic behavior during switching". But when I use a separate source as in the schematic, it works fine. Can't I really use the same source for all bootstrap connections?

Also the PWM frequency needs to be at 1 MHz. Has anyone used a driver circuit which can work at such high frequencies and got good results?

Thanks in advance :)


texts: Mesh Current Method.(Current assignment)

texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to solve this using the mesh current method. I assigned the current direction as follows

From this I used KVL for each loop and had the following:

loop (a):
$$1000(I_b-I_a)+5000I_a-12=0$$
loop (b):
$$-1000I_b+3-1000(I_b-I_a)=0$$

so from this I obtained:

$$I_b= \frac{1}{375} A
$$
and,
$$ I_a=\frac{7}{3000}A$$

which I know is incorrect since it is inconsistent with the circuit simulation.

Could someone point out where the error is? Is this a case where mesh current method doesn't work!?


texts: Does Arduino need the bootloader if programmed with programmer?

texts:
I am trying to program a few Atmega328 (not Atmega328p) with an ICSP.  These are TQFP.

What I am trying to do is to upload the program to a fresh chip without having to first load the bootloader.  I use a command like this

avrdude -v -p m328 -c usbtiny -U flash:w:blink.cpp.hex:i

avrdude says it is uploaded successfully, but the program does not actually run.

However, when I first burn the bootloader, using the Arduino GUI, then use the command line and programmer to upload the program, the program does run.  I am confused about why this is because my understanding was that the bootloader was not needed if the programming was done using the programmer.

Why is the bootloader needed?

Secondly, if the bootloader is needed, is there a way to make avrdude do everything to load the bootloader and the program in one line?


texts:
I want to build a circuit similar to this one:

I read that using push pull without per-pulse current limit or series with trafo cap can cause core to saturate because two pulses aren't perfectly symmetric.

But there is hundreds of circuits without any limit or cap and they work ok. When does this saturation process starts being noticeable? Should I care about it when making 35Watts dc-dc or it's noticeable only when power is big?


texts: How to calculate the emf with flux density given instead of flux

texts:
So I have the following question

What is the emf in a  coil of 2000 turns and c-s area 10cm2 when a flux density of 0.4T density in it is reversed, i.e.  in a time of 20ms. Also what would be the the direction of the induced emf.

What I have so far is

.4 x 10
= 4w (flux)

then -2000x (.4/20x10-3)

Would this be correct?


texts: Atmega328 is available in market in two versions - With and without bootloader. All prefer the one with bootloader. What will be the advantages/disadvantages of Atmega328 without bootloader ? I read that bootloader should be present in a controller for ease of programming. But I am not sure how it eases programming.


texts: What is the main difference between and potentiometer, rheostat and a varistor?  And how do the application of the three in a circuit differ? Or to be more concise, in a variable power supply why would you want to use each one rather than the others, or what benefits would one give over another in a variable power supply circuit.


texts:
I am trying to find an equation for the feedback factor of an Armstrong oscillator in terms of the transformer inductances and I can't find one in books.

Am I correct if I say that the feedback fraction of the oscillator is the ratio of turns of the tickler coil to the primary coil? If so, according to this equation,

and assuming other inductance dimensions to be equal for the primary and secondary, is the feedback fraction equal to the square root of the ratio of the tickler inductance to the primary inductance?


texts: Whats the difference between amplification and gain in a BJT?

texts:
Considering the 3 basic BJT amplifier configurations

For example

consider CB config,

we have a high Voltage gain but the input resistance is low, so there is no effective transfer of voltage Vsupply to BJT.

If we needed to amplify the current, since CB config has low input resistance, we have an ideal transfer of input current but the current gain is terrible (~1)

How do we qualify amplification then?i mean what is it that the CB amplifier amplifying here.please help me understand the difference between gain and amplification.


texts: 12v (ish) measured by a 0-3.3v input pin

texts:
firstly apologies I'm a newbie at practical electronics!

I have a sensitive little thing which can measure 0-3.3v DC in steps of 0-1023. I'd like to use it to measure the voltage on a "12v" vehicle battery - which as I'm sure you know can go significantly higher when being charged through an alternator so really I need to figure out the following:

What circuit can I design to take a DC input of between... 10v and 15v... DC and bring it down to <3.3v in such a way that I can still measure the difference?

I have seen some similarish posts but all have been (a) relatively specific and  (b) not explained in laymans terms that I could understand.

thanks


texts:
I have not yet build following circuit:

Circuit in high performance needs 5V 1.7A (measured). I have source which is powerbank with 16 000 mAh. Outputting via ports: USB-C 5V/3A, USB-A 5V/3A, Micro-USB 5V/2A. Also it is important to notice that powersource which is powerbank is 1 meter away from circuit board (image above). I will connect circuit board to powerbank via USB-C connector (U1).

Circuit description:
LED: 5V/1.6A powering APA102 85 led strips
C6: 100nF
P5: green LED
R13: 1k ohm
C5: 10uF
D2: 1N4007G
U2: ESP32

What I am asking is how to make ESP32 (U2) uninterrupted from power. If it does then controller will not send data to LED strips.

Operating temperature in cold outdoor environment - mountains.

My previous version had 1.5mm copper wire to power circuit via DC jack with issue while rotating DC jack power is lost for few ms (my eye couldn't notice but data sending stoped immediately) which make ESP32 freeze.
USB-C should be able to deliver enough power via 4 pins.

Question is that: Does circuit contains everything? Do you suggest to add something? I don't understand very much how to make circuit stable.


texts: How might we control a 2" valve >2000ft away in a remote village.  We're thinking that we power the system with a 12 v or 24 v solar powered/ battery backup.  The spot in the village with line of sight to the proposed location of the array is 2000 ft.  The valve is another 230 ft beyond the array and not visible from the village.  The valve will divert monsoon contaminated water from the solar powered system that brings water to the village from 900 ft below.  Since the valve will block the flow from the seep/ spring entering the system, there is space for the diverted stream to runoff.


texts:
I am designing a circuit with a piezo buzzer. I want to use one that I can attach directly to my uC output pin (no transistor).

The question is, can I do it with this one? (PS1240P02AT) http://www.farnell.com/datasheets/84905.pdf

It says 4khz rectangular wave and 3V. But what about current consuption? Can I just add a series resistance around 200 ohm in order to limit the output current to a safe value?

Actually I am a little bit confused. I thought piezo buzzers do not need a PWM wave, only a "high" logic level and they sound, whereas piezo transducers do need the square signal. However, this one says piezo buzzer (without circuit) so I assume it is a piezo transducer. Is it right?

Thank you.


texts: Designing a good RF Transmission/Reception system for Embedded System

texts:
I want to have 4 sensors transmitting information to a microcontroller ie

4-bit Encoder -> Transmitter >>>>>>>>>>>> Receiver - > Decoder -> MCU

The problem I have is that if I use 4 transmitters and one receiver it will not be possible to alternatively get data from each sensor because there will be no easy way ( or at least it seems ) to make the transmitters transmit in turns.On the other hand if I use 4 transmitters and 4 receivers the 4 transmitter/receivers will interfere because they will be trying to transmit on at the same frequency and I would also have the problem of having to use 16 I/O ports on just getting sensor data into the MCU.Does anyone have an idea on the best/easiest way to solve this problem?

The problem is similar to this one, except that I want to transmit data from 4 different locations and not only one.


texts: Input impedance of differential amplifier

texts:
Can someone please explain to me, how I should look at the input impedance of the opamps, seen through the voltage \$V_1 V_2\$?

I have two questions on the differential amplifier:

Why doesn't the input impedance depend on the feedback resistor \$R_2\$ of the first circuit seen by the voltage \$V_1\$?
Why is the input impedance of the second circuit \$2*R_1\$ when you put a single source on both terminal and why doesn't it depend on the \$R_2\$ that is connected to the ground?


texts: STM32 ADC sampling with timer and DMA and send data to computer with USB

texts:
I want to sample a 4kHz signal that is produced by a signal generator.
I read 2000 samples in a row and then I send it to computer via virtual serial that is provided by USB of STM32F103C8T6. I set timer 3 in order to trigger the ADC and then I set up a 2000 length buffer for DMA.
When I plot signal on the computer the data is not continuous and there is a problem between the signal.
I also stop ADC at the beginning of  the PeriodElapsedCallback and start it again at the end of it.
Here is the image of my signal:

The ADC clock is 12MHz. The cycles is set to 28.5 and I use a 12bit ADC. My timer clock is 48MHZ and it counts 30 clocks to trigger the ADC. DMA is set to circular mode. I do not expect these disruptions in my signal because I am taking 2000 samples without any stop.
EDIT:
This is my code. As I mentioned before I stop the DMA in the beginning of the interrupt and start it again at the end.
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
  HAL_ADC_Stop_DMA(&hadc1);
  HAL_TIM_Base_Stop(&htim3);

  usb_put_arr_int(arr,ARRAY_LENGTH);
  HAL_GPIO_TogglePin(GPIOC, 1<<13);

  HAL_TIM_Base_Start(&htim3);
  HAL_ADC_Start_DMA(&hadc1, arr , ARRAY_LENGTH);

}

I also change the timer period from 30 to 400 and I got a better result but the problem still occurs. I am suspicious about DMA speed.

Based on my calculation, the timer triggers the interrupt every:
400/48000000 = 8.33us
and the speed of my ADC is about
(28.5+12.5+2.5)/12000000 = 3.62us
So the ADC speed is faster than the timer. Thus, I expect the timer cannot trigger the ADC before the last sampling had completed.

I changed the CDC function according to what @JiříMaier said (I did not change my interrupt code.)
uint8_t CDC_Transmit_FS(uint8_t* Buf, uint16_t Len)
{
  uint8_t result = USBD_OK;
  /* USER CODE BEGIN 7 */
  USBD_CDC_HandleTypeDef *hcdc = (USBD_CDC_HandleTypeDef*)hUsbDeviceFS.pClassData;
  if (hcdc->TxState != 0){
    return USBD_BUSY;
  }
  USBD_CDC_SetTxBuffer(&hUsbDeviceFS, Buf, Len);
  result = USBD_CDC_TransmitPacket(&hUsbDeviceFS);

  for (uint32_t usbTimeout = 100000; usbTimeout > 0; usbTimeout--) {
    if (hcdc->TxState == 0)
      break;
  }

  /* USER CODE END 7 */
  return result;
}

I also changed my code structure and changed my interrupt code according to  @JiříMaier advice and I got the following result. The problem is that if I do not open the serial plotter on the computer in the beginning of the microcontroller start, microcontroller gets stuck if I open the serial plotter later.

When I change the buffer size from 2000 to 1000 everything is OK but I do not know why it has problem with the size of 2000.
In order to complete the documentation, this is put_arr_int function:
void usb_put_arr_int(uint16_t * number,int len)
{
    #define batch_size 50

        for (int j=0; j < (len/batch_size) ; j++)
        {
            count += j*batch_size;
            char f[batch_size*7];
            sprintf(f,"%hu\n",number[0 + j*batch_size]);
            for(int i=1;i<(batch_size);i++)
            {
                sprintf(f,"%s%hu\n",f,number[i + j*batch_size]);
                count+=i;
            }
            CDC_Transmit_FS(f,strlen(f));
}

len is always bigger than batch size.


texts: Getting transfer function from block diagram

texts:
I am having trouble figuring out this step in an example question I've been given.
I'm supposed to be finding the 'transfer function in the forward path'.

This image shows the block diagram (top) and what I have been told is the correct forward path transfer function (circled with red).

But based off of my understanding of that a forward path transfer function is, I would have said Gfp = 5 * s+4/(s+5)(s+8)

Where am I going wrong?


texts: TL072 Op-Amp Phase Shift, Differences Between Manufacturer Specification

texts:
I have been working on an Active Low-Pass filter (2-pole Sallen-Key configuration) for a Low Frequency Oscillator (LFO) on a synthesizer project. I had a problem with a recent build that I have managed to trace to a change in the Op-Amp manufacturer. The original TL072CD (Texas Instruments) has been replaced by a TL072IDT (STMicro) and resulted in a misshapen LFO waveform, post-filtering.

Looking through the datasheets, the only significant difference that I can see between the two parts is the phase shift:

TL072CD - Texas Instruments:

TL072IDT - STMicro:

It appears that there is a 180 degree phase shift difference between the two TL07x's at low frequencies. I would expect this amount of shift to drastically alter the performance of my filter, especially at very low frequencies (The LFO will operate @ < 1Hz). However, the inconsistencies between phase-shift diagrams could be misleading me. Could anyone clarify this for me? Has anyone encountered a similar problem with differences between op-amp manufacturers?


texts: What does a LC circuit in parallel to a speaker do?

texts:
I'm designing crossovers for my rear channels; a 2500 Hz 3rd order butterworth between an 8 ohm ribbon tweeter and two 4 ohm woofers in series (8 ohm load).

While my original plan was to use two DPDT switches for L-Pad attenuation circuits; in one position there would be no attenuation, in another there would be a ~2dB attenuation. However, I found On-Off-On DPDT switches that would enable me to 'remove' the tweeter, woofers, or both from the circuit and this intrigues me.

However, there will be an inductor and a capacitor in series remaining on each channel when in the 'off' configuration.

I'm wondering:

When the drivers are removed from the circuit, will the remaining LC/CL circuit be forced to dissipate the power (up to 175W)?
When both drivers are removed from the circuit, what 'load' would be 'seen' by the amp?
If only one of the drivers are removed, how will the LC/CL circuit affect the remaining driver?

Here's the circuit:


texts: How can I find an OPamp, or any other component, that has the required properties when using simulation software like multisim

texts: Hi I am require an OPamp that has a slew rate of 1Meg a open loop gain of 100k and a GBW of 1 Meg for a circuit simulation on multisim. I was wondering if there was a way to search for a component by its properties so I can find an OPamp that fits my needs, I am quite new to circuit design and googling hasn't turned up much. Thanks!


texts: How to arrange resistors for certain resistance

texts: This question is like this one. I have two 1 ohm resistors, six 2 ohm resistors, and want 2 ohms total. All resistors must be powered (since they are actually speakers.) How do I do this? Ideally, a systematic way, or a computer algorithm should be presented to do this, but I am mostly concerned with the above problem.


texts:
I'm looking to determine the electrical power input to a 3-phase BLDC motor, driven by TI's DRV8305 motor controller. I can't use the DC power flowing into the system because I'm trying to capture the efficiency loss of the uC, gate driver, and switching MOSFETS. There are sensors on the phase voltage and phase current. For the controller, it uses a power VARIANT Clarke transform, as shown here, for BOTH the voltage and current:

Then it uses a standard Park transform to get to the DQ0 reference frame:

From my understanding, Theta is chosen such that my current and voltage will align with my D axis only, and presto, I have a DC Current and DC Voltage. However, because my Clarke Transform was power variant, I must scale my P=I*V by some factor in order to get the correct answer?

From my understanding, a solution would look like:

$$P_{ABC} = I_{DQO-INVAR}(t)*V_{DQO-INVAR}(t)$$
$$P_{ABC} = P_{\theta}I_{\alpha\beta\gamma-INVAR}(t)*P_{\theta}V_{\alpha\beta\gamma-INVAR}(t)$$
$$P_{ABC} = P_{\theta}T_{INVAR}I_{ABC}(t)*P_{\theta}T_{INVAR}V_{ABC}(t)$$
$$P_{ABC} = P_{\theta}*sqrt(3/2)*T_{VAR}I_{ABC}(t)*P_{\theta}*sqrt(3/2)*T_{VAR}V_{ABC}(t)$$
$$P_{ABC} = 3/2*P_{\theta}T_{VAR}I_{ABC}(t)*P_{\theta}*T_{VAR}V_{ABC}(t)$$

Where \$P_{\theta}\$ is the Park Matrix, \$T_{INVAR}\$ is the power invariant Clarke Matrix, and \$T_{VAR}\$ is the power variant Clarke Matrix.

This would lead me to believe that I need to scale my power variant DQ0 output by 3/2 in order to get the actual power draw? Please confirm or deny.

I've looked for a solution, but it does not seem to be a common question. I'm forced to use the power variant Clarke transformation because TI's Instaspin Library is built on it. I'm rather unfamiliar with three-phase power. If there's any other information relevant to the problem, I'll be able to provide it. A good reference would be much appreciated.


texts: How to calibrate an ammeter and voltmeter?

texts:
How can I calibrate  an ammeter and a voltmeter.

I just want to know about it. Because it might be helpful and I think it is a vital thing to know. So how can I do this?


texts: Need help connect relay to surveillance camera

texts:
I am seeking help.  I am NOT an electrical engineer!

I have a D-Link DCS-5222 camera that I am using for security.  I have made an IR LED array to provide illumination when the camera is in IR mode.  I am trying to connect a relay between the camera DO and the light source so that the light will turn on when triggered by motion.

The LED array uses a 12VDC power supply and draws approximately 960mA.

The only documentation I have for the camera's DI/DO is below.

I have a 5VDC,1 CHANNEL HIGH/LOW LEVEL INPUT, photo and specs below.  I do not have any datasheet for the relay.

--Relay specs--

Module description:
1. MAXIMUM LOAD RATINGS : AC 250V/10A, DC 30V/10A;
2. using SMD optocoupler isolation, driving ability, stable performance; trigger current 5mA;
3. 12VDC Operating voltage
4. the module can be set for a high or a low level input by a jumper setting for each channel
5. Relay is rated at 12VDC Coil , OUTPUT CLOSURE CONTACTS @ 10 AMPS 250VAC/30VDC
6. BOARD POWER INDICATOR IS GREEN LED AND THE RELAY STATUS INDICATORS ARE RED
7. ALL TERMINAL CONNECTIONS FOR THE I/O CONNECTIONS
8. MODULE DIMENSIONS EACH BOARD; 1 15/16"D X 1"W X 3/4"T

Module interface:
1. DC+: positive power supply (VCC)
2. DC-: negative power supply (GND)
3. IN: can be high or low level control relay

Relay outputs:
1. NO: normally open relay interface
2. COM: Common Interface Relays
3. NC: normally closed relay interface

High and low level trigger options:
It is low level trigger when jumper connect to LOW pin
It is high level trigger when jumper connect to HIGH pin

--END OF SPECS--

Can anyone help me figure out how to connect between the camera and the relay? I am trying to power the low side of the relay from the camera.

Any help will be greatly appreciated!


texts: 2 Layer PCB Copper Pour on the bottom layer

texts: I am an amateur PCB designer. Trying to design my first PCB. It's a two layer board with ESP8266 module. I have read lot about ground plane and copper pour at the bottom layer. I have tried to use all those knowledge while designing this PCB. Can someone please tell me if I made any BIG mistake here? Here is an image of the bottom layer..


texts: Soldering USB cable to the bottom of USB connector

texts:
I have a USB device with a type A jack connector (see photo). I am integrating this device as a part of another device and due to requirements for ruggedness I would like to have a fully soldered USB wired connection from the CPU module to this device.

As I want to avoid desoldering the type A jack is it possible to just leave it in place and solder my USB cable directly to the USB data/power pins that can be seen on the bottom of PCB?

Will USB 3.0 or at leas 2.0 connection work like this? I wonder whether the bypassed connector will not make any troubles with the USB connection as it is a piece of conductor just left in place.

I have one more USB 2.0 device to integrate yet which has a vertical through-hole micro USB connector where I would like to do the same.

Device #1:

Device #2:


texts: Using switches installed across pins on AVR

texts:
I have the following layout, the switches are part of an existing hardware piece I'd like to reuse.

I'd like to be able to detect button presses on the vol+ and vol- buttons. The plan was to actively monitor their states by using internal pull ups and changing individual pin states.
For example, to poll vol-, I'd set PB0 as an output, low state, and PB4 as input with active pull up, I expected to read a 0 when the switch is pressed.

I'd like to know if this is the correct approach. So far I've been struggling with this and it doesn't work.

This is the polling function I wrote:

uint8_t  read_button_volm(){
//VOLM
DDRB |=_BV(PB0);
PORTB &=~_BV(PB0);
DDRB &=~_BV(PB4);
PORTB |=_BV(PB4);
return ((PINB & (1<<PB4)) == 0);}

For comparison, I get a perfect behavior with the mute button, using the following method:

uint8_t read_button_mute(){
DDRB &=~_BV(PB2);
PORTB |=_BV(PB2);
return ( (PINB & _BV(PB2)) == 0 );}

As an added consideration, the switches have a really high resistance when pushed but it doesn't seem to be a problem with the mute button.


texts:
I've just gotten through replacing capacitors on a trio of dead LCD screens (nothing's blown up yet, so far) - they either had one or two capacitors on their inverter circuit SLIGHTLY bloated, and not quite leaky. I ended up replacing all capacitors of the same brand/'colour', even the ones that looked fine, in case.

Now, checking a bad resistor is simple - i can use a standard multimeter to test it, and i tend to check my solders with the continuity testing option of the multimeter.

How would i test a capacitor ? Is there some standard, common way to test one?


texts: Verilog router design and best way to handle variable size packets in verilog?

texts:
I have a synthesizable Verilog/logical design question. My question is more logical than syntax.

I wish to implement some sort of router that has three input/output ports of full-duplex UART RS232, that are sending packets to each other.

Main points of design:

The packets are with variable size and they contain the following fields: source(1 byte), destination(1 byte), payload length(2 bytes), payload.
payload length is variable between 4-2000 bytes.
I want to have some sort of routing table "what destination will be routed to which of the UART ports", and some sort of firewall(not sure the proper name) something like "which sources allowed to send packets to which UART ports".
loopback is allowed (the packet that is received and sent through the same port)
broadcasting is allowed (maybe destination address that routed to more than one UART port)
the module needs to be generic so I could expand it to more than 4 ports.

For me, I think the hardest part to start with - is how to handle variable size packets? If the packets were fixed size, and not too big, I would have had an input FIFO and an output FIFO for each UART port:

reg [packet_size-1:0] fifo[num_of_packets]

each input FIFO would have stored in each fifo[I] a whole packet that was received from the uart, and a module that reads whole packets from each input FIFO, checks for source the dest of each packet and using that routes the packet to the wanted output FIFO,and from there a UART transmitter that takes a packet and sends it byte after byte.
Problem is that a packet can be really really big, so I don't want to hold a fifo that has 2000 bytes in each cell...

That also brings the question of how to transfer the packets between the internal modules?
As said, a packet can get really big.

I realize there are a lot of questions in my post, but I will much appreciate any help. Also, if there are some reference designs or something similar that can help me, I will happily review it.

Thanks for the help.


texts:
I appreciate any help as I try to figure this lightbox project. I need to wire up to 144 3V (built-in resistor) LEDs from flickering tea lights (normally battery powered).

Not sure how many to wire in parallel for a 120V outlet, and what power adapter to get. Suggestions welcome.


texts: STM32 Nucleo L432KC + RFID Antenna + OLED power troubleshooting

texts:
I am trying to make a simple Low Frequency (125kHz) RFID detector using:

STM32 Nucleo L432KC
Parallax RFID R/W module
Simple I2C OLED 128 x 64 (OLED is normal, it's not drawing high current or anything)

Configuration #1:
When I have all the components connected properly and powered/debugged through PC->USB->L432KC, the RFID (uses 5V pin provided from L432KC) read range is low. If I unplug the OLED (uses 3.3V power provided from L432KC) the RFID range is back to normal, about 10cm.
This made me guess that the board is not able to provide enough power to components (5V for RFID Antenna and 3.3V to the OLED).
Configuration #2: 5V external USB/bench power supply
There are couple ways to power the L432KC externally, so I got a 5V/1A power supply (typical USB charger, confirmed output) and routed the wires so that it's providing power to the L432KC's "VIN" pin and "5V" pin (usually the "5V" pin is an output but if the power source is 5 volts, it can be connected here, also the "VIN" needs to be powered to "activate" and run the flashed program). This still had the problem of Antenna having a low read range, unless the OLED was plugged. (The whole system used about 4.75V/200mA ~ 300mA when measured) I changed the power supply to a desktop digital DC power supply and provided 5V, still had the low RFID problem.
Configuration #3: Two separate power sources
Powering L432KC+RFID Antenna through one 5V power source and another 3.3V just for the OLED seems to work fine, but I cannot understand why it was not working on config #1 / #2 since the power supply was solid.
Question:
Can I have any guidance or insights regarding what's happening here and if it's just the nature of L432KC being a microcontroller aimed at low power projects? (I tried changing to F401RE and trying config#1, but still had low RFID read range.)


texts:
simulate this circuit – Schematic created using CircuitLab

How to get the Thevenin voltage if i remove the 10 ohm resistor?


texts: What free software can be used to simulate transmission lines and other RF circuits?

texts:
Technically, one can use LTSpice as it features a transmission line model, but obviously it doesn't like dangling nodes (ie. open lines) and isn't really suited for that purpose anyway due to lack of RF-related measurements.

What other software can be used to do a schematic-level simulation of RF circuits with transmission lines and lumped elements? I want to model distributed filters (like made from coax), matching circuits (tuners or baluns) etc. Amplifiers would be nice, but not necessary.


texts: Is using a high sample rate on an oscilloscope ever a bad thing?

texts:
A while back i was gathering some ECG data for a colleague at a reasonably high sample rate (around 20kHz - 100Hz is enough for ECG). She came back to me and asked me to regather the data at a lower sample rate - claiming that the high sample rate was introducing extra noise.

Is this plausible, realistic, or based in truth? I can't see how a higher sample rate would make a signal worse - especially considering the data was gathered on an expensive hi-spec oscilloscope


texts: Communication between modules over USB using a uC

texts:
I have a module (say A) which sends data serially to me at 5 Mbps. I want to transfer this data to another module (say B). For B, I have a few choices for links: USB, UART, PCI/E, etc. I am not sure but I think USB would be the best choice at such a high data rate. I already have a uC in addition to modules A and B (used to send some control signals to these modules). Can I use a uC for interfacing between A and B?

Note that the output of A is analog data. So, I need to pass it through an ADC before sending it to module B. The uC shall be incorporated somewhere in between (either between A and the ADC or ADC and B).

If a uC is not the correct choice, then what should I use? I need to make it as low power as possible as its battery operated.

Clarifications (Edit-1):

5 Mbps is the data rate after 10-bit ADC
Battery is roughly around 400mAh
Data flow: Module A -> Analog Data -> ADC (10-bit) -> uC -> USB cable -> Module B


texts: Techniques for building 'Bed of Nails' testing board

texts:
When testing a complete circuit board a 'Bed of Nails' can significantly reduce time and errors.

What are some techniques for making a DIY Bed of Nails?

Specifically, looking for what kinds of materials work best, how to trace the board properly to make the holes in the right place, in other words, it's the little things that experienced people know but for a beginner would be a lifesaver.


texts: Controlling multiple motor drivers with one Arduino

texts:
I have one Arduino and I need to be able to control five to seven 12V motors that each draw about 4 amps.

Would I be able to use four Sabertooth 2X5 Regenerative Motor Drivers for this? Each driver controls two motors and takes a 0-5V analog input. Would I be able to connect the input ground (for analog input) all to the same GND on the Arduino, and then individually connect each drivers' analog input to a PWM-capable Arduino output pin? Would that work? I'm a bit new to electronics, specifically linking multiple circuits like this.

Thanks for your help!


texts: Analog switch with a fixed state when not powered?

texts:
I am looking for a chip that could handle DPDT (or SPDT, or ultimately SPST) analog switch for audio routing (in the mOhm range resistance) and can guarantee one state when there is no power supply.

I have been looking around in manufacturer portfolios and results were those two cases :

Either High-impedance is guaranteed on power-off (between both NC/COM and NO/COM)
Or the state of the switch can't be predicted in no supply mode

So both of those cases don't guarantee one specific state in no supply mode.

Do you know any component that could suit my needs ? Thanks in advance


texts: What is the maximum power an inductor can transfer in a SMPS?

texts:
I'm trying to analyze a boost converter circuit.  I have all the specs for the inductor used, including inductance (6.8uH) and saturation current (1A).  This runs from a 3V supply.  I'm wondering if there is a formula for the maximum power than an inductor with a certain inductance and saturation current can transfer when operated from a fixed supply voltage, regardless of at what frequency/duty cycle it is being driven? In other words, what is the theoretical maximum power of a boost converter using that particular inductor and running off of 3V?

The boost converter in this case is usually operating in discontinuous mode, but apparently may switch to continuous mode some of the time.


texts: Interfacing 16C554 UART to ARM based CPU

texts:
Due to deficit of UART's on my board (LPC3141 based) I have the idea to add external multi-channel UART.
It has data and address lines, which I'm pretty sure needs to be connected to EBI. Unfortunately surfing the web for several hours didn't made me happy.

Any links, hints or other info will be highly appreciated :-)

Parts to be used:

LPC3141 ARM CPU
SC16C554 Quad UART


texts: Upper 3-dB frequency of differential amplifier with current mirror load vs with resistive load

texts: In the BJT case, why is it that the upper 3-dB frequency of a differential amplifier with a current-mirror load (1st picture) is lower than that of a differential amplifier with a purely resistive load (2nd picture)?


texts: Besides over voltage protection, what other purposes are served by the shrink-wrapped (in yellow) components seen here? Do they have any effect on discharge, and will they discharge the battery other than parasitically in normal discharge use?


texts: Electric Motor-drive type/setup recommendations needed. I need 90,000 rpm at the output shaft @ a power of 30kW.?

texts: I am repurposing a car turbocharger to be driven by electric motor. It requires around 30kW, @90,000 rpm to function in the desired range. Which type of motor should I use? I'd probably have to use a gearbox/belts, but is there any way to avoid them, I would much prefer a direct drive system. I need control over RPM as well.


texts:
I have only six GPIO to control a piezo buzzer and 6 LEDs and read 6 buttons...
Would multiplexing the 6 LEDs/buttons in a 2x3 matrix work like this (i.e. 5 pins for the 6 LEDs and buttons, one dedicated pin for the buzzer):

simulate this circuit – Schematic created using CircuitLab

Driving the LEDs with "regular" multiplexing, i.e. row as output high, column as output low.
Scanning the buttons by setting row as output high and column to input with pull-down.

Drawback: pushing the button causes the LED to go off, increasing current - not be a problem with low-current LEDs.

Am I missing something? Could it be improved? Are there any implementations "out there"?


texts:
Suppose I know nothing about my load, only the voltage and current waveforms.

With this I can calculate apparent power (S), and real power (P) and use P and S to determine my reactive power (Q) for a cycle.  However, the Q that is calculated could be positive (implying inductive load) or negative (implying capacitive load) for any given P and S.

Are there any simple tricks I could do with the voltage and current waveforms to determine whether Q is positive or negative?

I know I could see which peaks first, voltage or current, and that would tell me if the current is leading or lagging the voltage but that would involve keeping track of the max/min and just gets complicated.  I'm wondering if there is an easier way to do this.  I have available to me only the samples in a 60Hz cycle of the voltage and current.  I also have sine/cosine vectors available, of which the sine vector is phase-locked with the voltage.


texts: LM317 - Calculate dissipation due to voltage drop

texts:
If I use a linear voltage regulator as LM317:

Input voltage = 24 V
Output voltage = 5 V (so a voltage drop of 19 V)
Mean load = 480 mA (peak load = 700 mA)

From the datasheet, I read that maximum operating temperature = 125°C, junction = 150°C

How I can calculate if this component is thermally suitable, instead of a switching regulator?


texts: 2 Transistor XOR Cell Floating Output Problem

texts:
I designed the following 2T XOR cell for my full adder purpose:

Theoretically it gives correct output for all input combinations. But on Tanner Eda using 180nm technology 5V supply, it gives logic 1 for input combination a = 1, b = 1 but theoretically it is incorrect. Because PMOS OFF for input logic 1 so output must be zero.

How can I make my 2T XOR cell fully functional for all input combinations?


texts: Question about the operation of a zener for a rapid relay release

texts:
This is a follow up question to Zener voltage selection for relay?.

The following image was taken from the previous question

I'm trying to grasp exactly what is happening in this circuit.

My understanding is as follows.

When the switch turns on, current flows from the supply into to the coil and down to ground.

When the switch turns off, the coil is going to resist change in current, and will increase the voltage to fight against the change in current. The zener will begin go into zener breakdown when the current exceeds its knee current, and will help dissipate some the energy and collapse the coil faster by providing a relatively constant current discharge rate (zener current to maintain zener breakdown).

When the zener current current cannot be maintained any furthur, the zener goes into reverse breakdown and the catch diode begins to conduct and the remaining energy is dissipated back into the coil for a exponential decay..

If the above description is true...then what happens in the following situation -

If we assume that the coil current is 10mA, and the zener knee current is 15mA. In this case, the current is not enough to cause the zener to go into zener breakdown, and so only the catch diode is helping to collapse the coil. Is the above statement true ?

Or instead, would the field convert its energy to a current so that the zener goes into breakdown and only when there is not enough energy left does the catch diode come into play ?


texts: Power adapter outputting incorrect voltage

texts:
I have a power adapter that, according to the label, is rated for...

Input : AC 220v
Output : DC 10-12v 2000MA

It has dual outputs allowing me to power two devices at once.  I am plugging it into a UK mains outlet and on measuring the power tips they both read 20v.

I have opened the unit up and the only components inside are a transformer, 4 rectifier diodes and a capacitor.

With such a small component count, which of these components could be causing the incorrect voltage to be output?


texts: What are differences between neodym motor wheels and copper motors?

texts:
I want to learn about electrical wheels, typically used in electric bicycles. But most of information I could find is related to marketing, and nothing on theory. This is probably due to "relative novelty of this field", and each manufacturer want to keep its secret. But to become one - one should learn motor construction theory at first.

Afaik, design of the vast majority of these wheels implies multiple coils on the inner stator, which (when fed by AC of rectangular form) forms magnetic fields, that pushes neodym magnets on the rotor, thus creating motion:

But also I heard about (magnetless) squirrel cage rotor, with construction principle, illustrated by following image. Despite it is not a actual motor rotor, it has some similarities in its construction (bars, short circuiting rings) :

Image from: pnpntransistor.com

So I have a question - why even bother with rare and expensive neodym magnets (that could easily break on the road), while always can use latter variant? I dont understand well, how latter works, so it would be nice, if you could compare and explain operating modes of these two types of motors, "side by side" (to show difficulty or impossibility of creating latter variant). Thanks.


texts: What should be the polarities of the op amp input terminals such that the system is stable?

texts:
simulate this circuit – Schematic created using CircuitLab

Ignore the - and + signs on the opamp (I couldn't erase it using the schematic), is it possible to determine the polarity of the op amp input terminals, using just the information of the resistors in this circuit, such that the System is stable?

By stability I am referring to a state where it doesn't oscillate.


texts: How can I stop MPLAB X from hanging between build and program?

texts:
I've been using MPLAB X and XC16 to build and program projects for a dsPIC 33EP128MC506 for about a year now. For the last two months, I've seen some new and unusual behavior on two separate machines. Both are running the latest MPLAB X and XC16. One PC is Windows 7, the other is Windows 8.

When I press "build and program" the project builds properly, then hangs. I sit there with a "Build successful message" and I can operate the IDE as normal, but it never proceeds to the program stage. The only way I can get the IDE to program my chip is to open the Windows task manager, kill the javaw.exe process, and reopen MPLAB X. I then get one good program before it starts exhibiting the same behavior.

In other words, every time I program a chip, I have to kill MPLAB and reopen it. That gets kind of old. The IDE is also constantly "Scanning projects", but I can't tell if that's related, because I can't make it stop.

I've opened a ticket with Microchip, but no response. I've recreated the project from scratch, no luck. I don't have this problem with dsPIC 30F6012a projects. Has anyone seen this? Is there a known solution?


texts: how to send inter-operator sms via GSM/LTE module

texts:
I am using a GSM/LTE module (EC21 Quectel) to send and recieve sms with  HyperTerminal application on computer by at-commands. I can send sms to devices with the same operator (intra-operator), but not to any other operator (inter-operator).
I can even recieve sms from other operators on my module, but when i try sending to them i get error.

so does anybody know how to send an inter-operator sms?
i would really appreciate it if anyone could help.


texts:
I there,
I've got this code running on an ESP8266
#include <Arduino.h>

//Pins connected to the relays
int relay1 = 12;
int relay2 = 14;
int relay3 = 5;
int relay4 = 16;

void forward();
void reverse();
void stop();

void setup() {
    //Set the relay pins as output
    pinMode(relay1, OUTPUT);
    pinMode(relay2, OUTPUT);
    pinMode(relay3, OUTPUT);
    pinMode(relay4, OUTPUT);

    //Motors off
    digitalWrite(relay1, HIGH);
    digitalWrite(relay2, HIGH);
    digitalWrite(relay3, HIGH);
    digitalWrite(relay4, HIGH);

    //Initialize serial monitor with 9600 baud
    Serial.begin(9600);
    delay(2000);
}

void loop() {
    forward();
    delay(2000);
    reverse();
    delay(2000);
}

void forward() {
    stop();
    delay(20);
    digitalWrite(relay1, HIGH);
    digitalWrite(relay2, LOW);
    digitalWrite(relay3, LOW);
    digitalWrite(relay4, HIGH);
}

void reverse() {
    stop();
    delay(20);
    digitalWrite(relay1, LOW);
    digitalWrite(relay2, HIGH);
    digitalWrite(relay3, HIGH);
    digitalWrite(relay4, LOW);
}

void stop()
{
    digitalWrite(relay1, HIGH);
    digitalWrite(relay2, HIGH);
    digitalWrite(relay3, HIGH);
    digitalWrite(relay4, HIGH);
}

And this is my wiring
I noticed that one of my motors wasn't working properly when I checked with a Multimeter the middle terminal on the 1st and 2nd relay (counting right to left) the Multimeter only registered +9V or 0V.
When I tried on the other 2 relays I got +9V and -9V
Am I doing something wrong? Is the module dead in anyway?


texts: Do wireless amplifiers work in both directions?

texts:
I'm especially wondering about wifi aplifiers (2.4GHz and 5GHz).
I have a couple of very basic questions about them. (I hope this is not too much for a single question):

Are there special signal amplifiers for routers and for client machines or would the same amplifier work on both? (I'm wondering because this one says "don't connect with network card".)
Does a signal amplifier work in both directions (upload and download) even if only one of the two parities is using such a device? (The one linked above says "bi-directional", has this anything to do with this?)
If it would actually work for both (sending data and receiving data): how does this work? I get that you can use an amplifier to make your sending signals stronger, but are the amplifiers also be able to better pick up weak signals?

(I am well aware of the strict laws related to transmit power limits etc.)


texts: 10 Lamps setup 220v ac, would it be safe?

texts:
I am not an electrical engineering or anything, I am just a curious person trying things at my home for fun.

I want to setup a lamp system for my sister's mirror where I would need to use 10 lamps from just one socket.

I made a diagram of what I mean, all 10 lamps in parallel with an interrupter in between the plug.

My biggest question is, would it be safe to do this connection? Is there a better way of doing it? I am scared of it not being safe since it's a lot of things on just one 220v ac plug.

Each lamp is 3W A5 using the socket E24.


texts: how to calculate the current in this circuit ( opamp)

texts:
how to calculate the current in this circuit (show with the green arrow)
Can someone explain with a bit of details.
In the books i got from school, they dont come close to what this looks like.


texts: Making 2-input AND gate, 2-input OR gate and NOT gate using only the "SAND" gate

texts:
Suppose there is a special gate called a SAND gate (Single-inversion AND) that looks like this:

How can I make 2-input AND gate, 2-input OR gate and NOT gate using only the SAND gate?

The truth table for this gate is:

$$\begin{array}{|c|c|c|}
\hline
A & B & \overline{A}\ {B} \\
\hline
0 & 0 & 0\\
\hline
0 & 1 & 1\\
\hline
1 & 0 & 0\\
\hline
1 & 1 & 0\\
\hline
\end{array}$$

To make a 2-input AND gate using only SAND gates, I would have to put 2 SAND gates in a row. Is this correct?

I don't know how to make 2-input OR gate and NOT gate using SAND gates. Can you give me a hint please?

Edit: I am only allowed to use SAND gates.


texts: Synchronous Generators: Full load and No load

texts: When referring to synchronous generators, what do they mean by "operating at no load or at full load"? Can I connect a load that is larger than full load?


texts:
I am currently trying to learn more about watches and what it takes to build them. I currently own a watch called the G-Shock 7900b and was wondering what runs it inside. Here is a link to the watch:

http://www.gshock.com/watches/Classic/GW7900B-1#

I am wondering if this uses an ASIC or a FPGA? I looked all over the internet but have had no luck finding an answer. Some of the features include receiving radio signals and having preset dates coded into the watch until 2099. Does this mean that this watch has memory? I always assumed that watches did not have a processor or memory.

Any suggests to these questions?


texts: Bulb not lighting up if resistor is used

texts:
I have a 12v adapter and small bulb of about 3.8v. If i give power to bulb with 12 volt adapter and with 100ohm to 10k ohm it doesn't light up and if i directly give it power without the resistor it fuses.

This is the bulb i have

When i give power to bulb with 9v battery without resistors it light up perfectly fine.

Adapter gives 1.5amp (mentioned on sticker)

How can i light up this bulb with 12volt adapter without blowing(fuse) it up?. I am not much experienced with electronics.


texts: What is the difference in the terms "signal return", "signal reference", and "signal ground"?

texts:
Are there common interpretations for each of these or are they all used interchangeably?

For example, node names in a circuit schematic with a earth ground, power lines, and signals lines should use names appropiate for each. Thats my goal - to clearly communicate this.

I should also mention that due to isolation there could me many of these - signal ground, reference, or return. Thats why they need a distinguishable name.


texts:
Simplify the following expression using Boolean Algebra:
$$ x = \bar{A} \bar{B} \bar{C} +  \bar{A}BC + ABC + A \bar{B} \bar{C} + A \bar{B} C $$
Answer:
\begin{align*}
x &= \bar{A} \bar{B} \bar{C} +  \bar{A}BC + ABC + A \bar{B} ( \bar{C} +  C ) \\
x &= \bar{A} \bar{B} \bar{C} +  \bar{A}BC + ABC + A \bar{B} \\
x &= \bar{A} \bar{B} \bar{C} +  \bar{A}BC + A( BC + \bar{B} ) \\
x &= \bar{A} \bar{B} \bar{C} +  \bar{A}BC + A( \bar{B} + C ) \\
x &= \bar{A} ( \bar{B} \bar{C} + BC ) + A( \bar{B} + C ) \\
\end{align*}
Now, I feel I am stuck. The book's answer is:
$$ x = BC + \bar{B}(\bar{C} + A) $$.

Based upon @StainlessSteelRat comments I tired this:
\begin{align*}
x &= \bar{A} \bar{B} \bar{C} + \bar{A} B C + ABC + A \bar{B}\bar{C} + A \bar{B}C \\
x &= \bar{A} \bar{B} \bar{C} + A \bar{B}\bar{C} + \bar{A} B C + ABC + A\bar{B}C + ABC \\
x &= \bar{B} \bar{C} ( \bar{A} + A) + BC(\bar{A} + A)  + AC(\bar{B} + B) \\
x &= \bar{B} \bar{C} + BC + AC \\
x &= \bar{B} \bar{C} + C(A + B )  \\
\end{align*}
However, I still get the wrong answer.


texts: How does programming FPGAs and CPLDs differ?

texts: I am learning to program programmable devices using a XC9572XL CPLD. I would like to know how much knowledge from programming CPLDs (in Verilog, VHDL) will be transferable to programming FPGAs (not necessarily Xilinx FPGAs).


texts: Need help determining why my voltage level drops

texts: Hi everyone.  I'm having troubles with this circuit.  I need the 7404 VCC pin to be at about 5V.  With the 7404 chip in the circuit physically the voltage at that pin is about 1.36V.  When I remove the chip it goes back up to 5V.  I'm not sure why this is happening.


texts: Where do mobile electrons come from to form an Inversion Layer in an N-MOSFET?

texts:
I am trying to understand the concept behind the threshold voltage in a N-MOSFET. Upon reviewing various books and the band diagrams, I analyzed the following but still could not understand where do the mobile electrons come from.

I broke up the inversion layer creation to two steps:

Step -1 Gate voltage Vg
Step -2 Gate voltage Vg>=Vth

In a basic MOS structure, I see the following:

Step -1:

As per KVL, the following relation is valid:

Also the following relation:

Where QB is the bulk charge formed due to the application of gate voltage (less than threshold voltage). Hence a depletion region is formed because the holes in the p-substrate are depleted by the negative charge created at the Gate oxide interface (not sure about this). Here there are electrons created but they are immobile because they have recombined with the holes in the p-substrate.

Step -2
Now, when we increase the Gate voltage equal to Threshold voltage (Vth), still more electrons are created beneath the oxide which cannot have no holes to recombine since there is a depletion region barrier (created by step 1) to reach the next hole. Therefore these electrons are mobile at the interface between the substrate and the oxide. This is a layer of mobile electrons - forming an Inversion layer.

Is the above analysis valid?

Also, are the following assumptions true?

Applying a positive potential at the Gate terminal creates free
electrons at the interface between the substrate and oxide.
The inversion layer is created only due to M-O-S- structure (no
influence of source or drain regions).


texts: One GPIO pin for LED, Pushbutton and Buzzer via high-pass filter?

texts:
There's Pin as both input (for a switch) and output (for LED) with ATmega32U4? but I also need one of six such pins to drive a piezo buzzer.
Due to its capacitive nature, I figured it could be connected to the GPIO as well (has no effect on DC signals):

simulate this circuit – Schematic created using CircuitLab

The idea was to suppress the noise, that would likely originate from switching the GPIO from output-low (to drive the LED) to input-pull-up (for sampling the pushbutton), using a high pass filter with an "odd" 1.5 kHz or so, so sampling at 100 Hz or so does not affect the 4 kHz piezo as much.

Drawbacks (both are acceptable):

pushing the button lights the LED (and dumps C1's charge to ground; maybe add a series resistor?)
driving the piezo with a 4 kHz square wave lights the LED at 50 % (maybe this can be a lower duty-cycle due to the filter?)

Does this work and can it be improved?


texts:
I am using FEMM to design a dc permanent magnet rotor.

I am trying to calculate the EMF that is induced to the rotor. Since each coil has a different position, the induced emf will be different.

In the following figure, you can see the parameters that are known for each coil.
Is it possible to calculate the induced emf by using these parameters?

If no, how can I calculate the induced emf in FEMM?


texts: MOSFET gate protection zener diode math .please help

texts:
My circuit's voltage input can range from 6V to 12.6V.  I want to use a p-ch mosfet for reverse bias protection.  However, the FET I want to use has a maximum VGS of +/- 8V, so I have to protect it in case the input voltage is on the high side.  Am I correct that I should choose a zener diode voltage lower than 6V but higher than gate threshold?  Any gotchas with the zener to be sure it works with the full range of voltage input I'm working with?  I'm not too familiar with the ins and outs of zeners.  Specifically, is there any harm in using TOO LOW voltage zener here (so long as the gate threshold is below the zener voltage).  Reason is economies of scale as I have 3V zener used on the board elsewhere.

Also: Would a simple potential divider do the job?  Or is a zener better?

Thank you.


texts:
I'm assembling a bluetooth speaker as DIY project. i'm stuck with bluetooth receiver module which have inbuilt push button (hold for 5 sec) to start/stop the bluetooth receiver. I want to ignore that switch and want to start the device directly when connecting the module to the battery. I looking for only one switch to power on everything. Please guide me.

Note: This is my first DIY electronics project and I'm new to electronics.


texts: LEDs can be, have been and are used as voltage references. Standard LEDs in various colors are cheap and hence sensible when wanting a low accuracy low voltage reference. Remember that low voltage Zeners have bad knee characteristics and poor tolerances. Zener diodes do make noise when in the breakdown region. In fact, there are noise generators based on this known principle in antique ARRL handbooks. However, is the LED less noisy than the Zener?


texts: Is it illegal to transmit in the FM range for personal use

texts:
I am building an FM transmitter. It is going to be designed to transmit only for a short range of around 50 to 100 meters. My question is whether it is illegal to transmit signals in the FM band over this short range without owning a license? If yes, what should I do to test it?

P.S. I live in India.


texts: Would a long chain of inverters induce jitter?

texts:
I've recently designed a high-speed driver with the clock working at a highest frequency of 10GHz.But as the clock period becomes shorter,I've found that jitter situation too serious to be ignored.

In order to help high-frequency clock to work,I adjust the buffer fanout to be 2:3,so that means adding lots of buffers(CMOS inverters) to form a GHz clock chain(over 20x stages),(it surely seems abnormal to me at the beginning,but I just think there is no better choice),will that possibly responsible for the jitter?

The following pic shows the clock at 7GHz.


texts: Is there a way to extend the length of wires for I2C connection?

texts:
I would like to connect a BME280 sensor to an Arduino board through the i2c bus connection. I read that i2c was not meant to be used over long wires and will not work properly over 50cm. I want to get it to work within 5-15m. Is there some sort of chip or device I can to attach to one or both sides of an i2c connection to extend the wire length? I would like to use only one power source, not two, and have the wire carry the power over those 5-15 meter as well, if that is possible.

P.S. Pardon my drawing. My electronics skills aren't up to the level of making a schematic


texts: Why a diode to GND in 0-30V LM317 circuit?

texts:
I'm looking at reference design 9.3.1 from http://www.ti.com/lit/ds/symlink/lm317.pdf where a LM317 is used between 35V and -10V to obtain a 0-30V regulation.

What is the purpose of the diode? would the circuit work without it without connection of the ADJ to GND?

simulate this circuit – Schematic created using CircuitLab


texts: Flowing back of current from capacitor filter to full bridge rectifier

texts:
Context:

Pg-485 of this pdf
Now we shall discuss the role of
capacitor in filtering. When the voltage
across the capacitor is rising, it gets
charged. If there is no external load, it remains charged to the peak voltage
of the rectified output. When there is a load, it gets discharged through
the load and the voltage across it begins to fall. In the next half-cycle of
rectified output it again gets charged to the peak value (Fig. 14.20). The
rate of fall of the voltage across the capacitor depends upon the inverse
product of capacitor C and the effective resistance RL
used in the circuit
and is called the time constant. To make the time constant large value of
C should be large. So capacitor input filters use large capacitors. The
output voltage obtained by using a capacitor input filter is nearer to the
peak voltage of the rectified voltage. This type of filter is most widely
used in power supplies.

So, as said in the above paragraph, the capacitor after being raised to the peak voltage, discharges to load as rectified voltage supply starts to decrease. The point I am being confused is, if the rectifier's voltage output voltage drops below the capacitor, then wouldn't the capacitor push back current into the rectifier as well? What effect would this have on the rectifier?
Edit: Thank you everyone for the help!


texts: UPS battery as auxiliary power supply for car - charging and detecting car on

texts:
I'm designing a arduino-based car system that I would like to have running even when the car is off and parked. Though the system is designed to be very energy efficient, I don't want it to run down my car's main battery.  I have a 12v to 5v converter already working (Tobsun EA15-5v DC12v to DC5v 3a converter)

I would like to use a small lead acid battery (a 12v 7200mAh battery for an APC UPS) as a power supply for the project, having it charge off my car's cigarette lighter port (which only supplies power when the car is on), and when the car is off the UPS battery runs the arduino system.

Additionally, I would like to know whether the car is on or the backup battery is being used, so I intend to build this circuit using a 4n25 optoisolator so the arduino can detect if the car is on.

My question really centers around:

1) Does this arrangement, without further circuitry, safely charge the 12v UPS battery when the car runs?  If I need further circuitry to manage charging, any recommendations for a module that would fit?

2)  In this arrangement, especially given the D1 diode, is the 4n25 circuit in the right place to detect a signal when the car power is on, but not when running off the UPS battery?

Any other advice?

simulate this circuit – Schematic created using CircuitLab


texts: How do I switch small AC signal on/off electrically?

texts:
Suppose I have an audio signal source.

I want to connect and disconnect it to amplifier electrically (for example controlled by another source, like microcontroller, sensor, 555, etc). I don't want to turn the signal source on or off itself, as it takes some time to start, I just want to connect/disconnect its output. How can I do that?


texts: Length of primary polynomial for scrambler

texts:
I need to scramble some data in FPGA before transmitting in to another FPGA in order to allow for clock recovery and maintain DC balance. I have implemented synchronous parallel scrambler for 119 bit long data block but I can't find any information if there are restrictions on primary polynomial length.

I have realized that using shorter polynomials consumes less resources after synthesis, for example x^9 + x^4 + 1 consumes 131 slice LUTs while x^93 + x^2 + 1 consumes 262 slice LUTs.

I would like my component to consume as little as possible but I am not sure if using too short polynomial leads to "worse" pseudo randomness?

EDIT:

Implementation on github: sync_scrambler


texts:
I would like to send pixel data from a MCU (PIC24 or PIC32) to a LCD computer monitor via HDMI.

Ideally, I would only update frames as needed and not have to transmit them continually.

Can it be done easily enough? What are my options?


texts: What component can transfer heat from cold to hot?

texts:
I'm sure I've read about this somewhere but I can't remember where and my Google search all seems to be too genetic to find what I'm looking for.

I'm looking for a component that uses electricity to move heat from one face to another (with the possibility of cold face to hot). I have a feeling it's piezo electric in nature but I'm not sure. I don't think it has any moving parts (ie. Not a fan), it's also not a heat pipe. Just a generic name for the type of device would be great. Thanks!


texts: How to find out how much voltage and current a soldering agent can handle

texts:
Is there any way to find out the maximum voltage and current that a soldering agent can handle based on the material and/or the information that I find on the package?
For example, I have this soldering agent at home:
S-Sn60Pb40
DIN EN ISO 9453
DIN EN 29454
60% Sn
6g
1,0 mm ø


texts:
I noticed this tester had precise length readings of short cables.
I decided to plug a very long cable (almost a full pack) and was surprised to see it still gives a reading. 232 meters:

Adding the cap to the end of the cable, corrected the length shown by 2 meters:

How does it do that?
How reliable is it?


texts:
I'm working on a project where I have to make a powerfull battery charger. And someone I'm working with told me that it is a good idea to have mains voltage connected to a full bridge rectifier and after that something like a Sallen-Key filter. But is there a reason for that? I do not get why it is an important feature.

Thanks a lot


texts: Current Source - MOSFET vs Bipolar NPN/PNP for stability

texts:
Consider the schematic below.

There are several pro an con for each, I would like to focus here solely on regulation stability. (Not voltage drop or opamp current as this is already answered).

I currently use the MOSFET version on a project and works pretty fine, after tuning several filters to improve stability it can reach about 0.1% stability.

However, I was wondering, given Bipolar have a "flatter" response, if using a bipolar would have a more stable output as it would swing less as it doesn't have gate capacitance and has a wider control region.


texts: What is the least number of 8 Ω resistors you can arrange to have a total resistance of 5 Ω and how do you do it?

texts: Is there a mathematical way to know the answer? (or you can do it only by trial and error). Could you prove that it is possible or impossible mathematically?


texts: How large can the working die size in a wide PDIP package be?

texts: What is the maximum die size for a 0.6" wide Plastic DIP package?


texts:
I have this little project that requires exact clock so I'm using 32768 Hz quartz on RB6 & RB7 on my PIC16F628. Both pins are grounded using 33 pF capacitors.

My code that configures the timer1 is as follows (HI-TECH C compiler):

TRISA = 0b11100011; //x3F;      // bit=0 - output; bit=1 - input
TRISB = 0b11110000; //x3F;      // bit=0 - output; bit=1 - input
nRBPU = 1; //affects inputs only
TMR1ON = 0;     // Disable Timer 1
T1CKPS1 = T1CKPS0 = 0;   // 1:1 Prescale value
T1OSCEN = 1; //start tmr1 oscillator
TMR1CS = 1;  //0: internal clock; 1: wait external clock
nT1SYNC = 0; //sync by external clock
TMR1 = 0x8000;
PEIE = 1;
TMR1IE = 1;
ei(); //sets GIE
//T1CON = 0b00001111;
TMR1ON = 1;     // Enable Timer 1

The config bits:

__CONFIG(WDTE_OFF & MCLRE_ON & PWRTE_ON & BOREN_OFF & LVP_ON & FOSC_INTOSCIO & CP_OFF & CPD_OFF);

The problem - it never runs. I have an LED in the ISR that should be lighted up. Also I used an oscilloscope to investigate. Changed the capacitors. Tried another crystal. Tried all possible approaches. Nothing helped.


texts: Is it possible to send characters through serial to go up a line on the console window?

texts:
I think it is possible due to how I can run vi straight from my serial port looking via TeraTerm. There, I can edit some text, go to the next line, then come back and edit the first line! How do they do this?

What character over UART could I send through to go "up a line"?

EDIT: Apparently line feed works. "\f" to clear the screen. However, this only works for Hyperterminal on my machine and not Teraterm. Anyone know why?


texts: Use two ADC channels to increase resolution

texts:
I need to capture the waveform of a low-amplitude signal that sits on top of a slow-varying, higher-amplitude component. I'm thinking of using an ADC with two channels, and feed one of them with a low-pass filtered version of the signal and the other one with an amplified, high-pass filtered version of the signal. That would increase the apparent resolution of my ADC. Am I wrong? Can you foresee any problems with this?

I forgot to say I have to capture the low-frequency component as well (the algorithm needs the average value of the signal).

The "high"-frequency component goes from 0.01 hertz to 10 hertz. The low-frequency component is mainly the average value of the signal, but it may change, slowly. The faster-changing component may have an amplitude 100 times smaller than the maximum average value. The microcontroller we will use has a 12-bit ADC (I cannot change that), but with many channels.


texts: Getting parameter from hierarchical block LTSpice

texts:
I know how to pass parameters into a block, but I can't figure out how to get parameters back out.
For example, I'm passing params into a block with:

Within the block, these parameters are used to calculate a parameter that is used by both the hierarchal block and the main schematic. I tried accessing this parameter with {x1.param} to no avail, and haven't been able to find a method to do this.
Is there a way to access a parameter from a sub-block, or do I need to define the equation set on both schematics?

Edit: Thanks for the answers guys. It looks like this is not possible.
From a concerned citizen:
Hierarchical blocks are local scopes, that is, variables and functions that are defined inside the block/subcircuit are not visible to the outside world. Think of it as a black box: what happens inside, stays inside, unless you provide a way from inside to outside -- and the only way you can do that is with a pin.


texts: MOSFET transistor with coupled drain and gate

texts:
The below circuit is part of a КР580ВM80A, a clone of an Intel 8080 by Vslav.
I'm trying to understand the purpose of coupled transistors T1 and T2. Vc is 12 V.

What will be "state" or voltage of point X for HI/LOW inputs at A and B. My guess is that for A = "HI" or B = "HI", output will be "LOW" and T1 and T2 will be "OFF".
For both A="LOW" and B="LOW", T3 and T4 are off and likely output will have high impedance.
Sorry if I my assumptions are wrong. I was learning digital electronic almost 20 years ago. Since then, I've been involved in software development. Thank you for any support.
Update:
Emulated the circuit (basically, this is a 3-state pin of the address bar controlled by internal state of the bit of address and inverted address bus enable signal). The simulation showed that voltage Vds = 0 of the FET with coupled drain and source.
Still, don't understand what is the actual purpose of it - what will happen if the gate of the next FET is directly connected to Vc (can't check it in simulator as had to tweak Vt to really high value +3.5V in order to make the circuit work as expected).

The free online app used to for simulation can be found here
$ 1 0.000005 10.20027730826997 50 5 50 5e-11
f 160 96 224 96 32 3.7 0.02
f 240 176 304 176 32 3.7 0.02
w 224 112 224 176 0
w 224 176 240 176 0
w 224 80 224 48 0
w 160 96 160 48 0
w 304 160 304 48 0
f 256 304 304 304 32 3.7 0.02
f 144 304 192 304 32 3.7 0.02
w 192 288 192 256 0
w 192 256 304 256 0
w 256 304 256 368 0
w 256 368 80 368 0
w 144 304 112 304 0
w 96 96 96 304 0
w 96 304 112 304 0
f 336 208 384 208 32 3.7 0.02
w 304 208 336 208 0
w 384 192 384 48 0
w 256 368 336 368 0
f 336 368 384 368 32 3.7 0.02
w 96 96 96 16 0
w 64 16 96 16 0
w 96 16 448 16 0
g 192 320 192 336 0 0
g 304 320 304 336 0 0
f 448 144 512 144 32 3.7 0.02
g 512 128 512 80 0 0
w 512 160 512 192 0
f 560 112 624 112 32 3.7 0.02
w 560 112 560 48 0
w 624 96 624 48 0
w 624 128 624 272 0
f 448 320 512 320 32 3.7 0.02
w 512 304 512 272 0
g 512 336 512 432 0 0
f 672 112 720 112 32 3.7 0.02
w 672 112 672 48 0
w 720 96 720 48 0
w 512 192 656 192 0
f 672 272 720 272 32 3.7 0.02
w 624 272 672 272 0
w 656 192 720 192 0
g 720 288 720 320 0 0
f 768 192 816 192 32 3.7 0.02
f 784 368 816 368 32 3.7 0.02
g 816 384 816 432 0 0
w 624 272 624 368 0
w 624 368 784 368 0
w 816 176 816 96 0
g 384 384 384 432 0 0
w 816 272 864 272 0
v 784 112 784 48 0 0 40 10 0 0 0.5
g 784 112 784 128 0 0
w 816 96 896 96 0
v 896 160 896 96 0 0 40 5 0 0 0.5
g 896 160 896 192 0 0
v 64 112 64 16 0 2 80 2.5 2.5 0 0.5
v 80 432 80 368 0 2 40 2.5 2.5 0 0.5
g 64 112 64 144 0 0
g 80 432 80 464 0 0
w 784 48 720 48 0
w 720 48 672 48 0
w 672 48 624 48 0
w 624 48 560 48 0
w 560 48 384 48 0
w 384 48 304 48 0
w 304 48 224 48 0
w 224 48 160 48 0
w 304 192 304 208 0
w 304 208 304 256 0
w 304 256 304 288 0
w 384 224 384 272 0
w 448 16 448 144 0
w 448 144 448 320 0
w 384 272 512 272 0
w 512 272 624 272 0
w 816 208 816 272 0
w 816 352 816 272 0
w 384 272 384 352 0
w 720 128 720 192 0
w 720 192 720 256 0
w 720 192 768 192 0
o 47 64 0 4099 20 0.00009765625 0 6 47 3 57 0 57 3 58 0 58 3


texts:
I would like to transform a signal that has fluctuations between 1.8-1.9V (for example) to be in the range of -1V to 1V. Essentially, run it through a linear transformation [ \$y'= (y-a) \cdot b\$ ]
What is the easiest way to accomplish this with standard op amps, such that a and b are tunable (say, with a potentiometer)?


texts: Testing a diode's electrical characteristics with temperature control

texts:
I would like to test a few diodes electrical characteristics at their device low limit, ambient, and device high limit temperatures.

I was thinking of using a Peltier element with a heat sink, but I'm not too sure how this would look like with sending current pulses.

The Peltier element could be put in a thermal chamber, but wouldn't the length of test leads cause interference with impedance and such?

The diodes of test are listed here:

MBRS340T3G
MBRS360T3G
BSS123
MBRS130LT3G
MBRS3200T3G


texts:
I am designing a power supply based on ST Viper 37. The supply is isolated and outputs 17V with CT transformer.

I got the transformer designed from the design center. One with Centre tap and another without center tap.

But upon using CT transformer, the output of the power supply is 17V.(As needed)

Using NON CT transformer, the output of the supply is 7~9v, it keeps changing.

Here is the schematic:

Here is the drawing pattern with center tap :-

Without Center tap :-

Transformer specs :

The PCB is same for the both transformer. The schematic suggest that CT is not needed. So, I was confused and thought of disassembling the transformer.

Upon disassembling, I found non-similarity in the design.

Flow of winding of CT Transformer:-

Primary Winding with 55 turns
Taping
Secondary Winding with 22 turns
Taping
Auxiliary Winding with 16 turns
Taping
Primary Winding with 50 turns

Flow of winding of Non CT Transformer :-

Primary Winding with 105 turns
Taping
Auxiliary Winding with 16 turns
Taping
Secondary Winding with 22 turns

The Auxiliary Winding is before the secondary winding in Non CT transformer and in CT Transformer the secondary winding is before auxiliary winding.

Where is issue? Why I am not getting same output with the Non CT transformer?

EDIT

This question is not duplicate but inspired from that question and it is result of that question, I faced this issue.


texts: How to connect a bulb and buzzer to be operated by one switch?

texts: I want to make a simple circuit. I want to connect a bulb, buzzer and switch to a battery. About the size we all used in science at school. When the switch is on, I want the buzzer and bulb to work together. Do I need to use resistors and transistors? I have no idea. Help!


texts: wire accidentally pulled out of "pilot light" can I by-pass pilot light?

texts:
I have an old egg incubator which I was given and it has a circuit board thermostat.. (most are '"wafer" systems or digital..)
The circuit board was 'burnt" and being older it is difficult to find parts, but I managed to find a circuit board, and being extremely "green" in the electronics field, I took one wire off at a time to make sure I didn't mix anything up. I had almost everything together and one wire the bare part was a bit short, so a family member attempted to strip the wire a bit more and accidently pulled the wire out of the "pilot light" ( the pilot light  shows you that the electronics are working.)
The  wire goes from the circuit board --and joins to a wire that goes down into the pilot light and then those 2 wires join a wire to the heating element.. in 2 different "circuits"
--We attempted to soder the wire, but it did not work...Does anyone have any idea if the "pilot light can be by-passed straight to the heating element, as I have not been able so far to find a proper replacement "pilot light".. -(I taped the wire together in the picture )--any help would be appreciated..
thanks head of time..]1]1


texts: Art Of Electronics - RC Differenciator Circuits and High Pass Filters

texts:
In the above image, take note of the line

dV/dt being much less than dVin/dt as a condition.  I once asked a question about Integrators. I understand both the above image and my earlier question on integrators well enough (I think).

A later section of the book in the frequency domain (above) references image 1.14 when it says "we can restate the earlier time domain condition for its proper operation (Vout being much less than Vin).  I understand what follows when it mentions the 3dB point.  My question specifically relates to finding the condition ....

Vout being much less than Vin

I do not see this in the section on differentiators.  If anything, I see the condition of dV/dt being much less than dVin/dt in section 1.14.  Vout as a condition, being much less than Vin was in an earlier section on integerators, not differentiators, which states their rates of change.

Can someone point out where the book finds the required conditon Vout being much less than Vin in section 1.14?  I suppose that if the condition on their  derivatives...dV/dt being much less than dVin/dt is met then  necessarily, Vout being much less than Vin is also met, though in a differentiator, Vout can go negative while Vin remains positive.  (high to low transition).  Is this statement referencing magnitudes?  Basically, I am trying to find how the above line on the condition for a high pass filter, which basically is an RC differentiator, is referenced in section 1.14.  I am not able to find the exact wording or convert the meanings/statements properly.  Can one necessarily state that a relation on the derivatives of V and Vin transfers to their functions?Thanks.


texts: Is this inductor and caps a good choice for a buck converter?

texts:
I wanted to get together a simple and efficient 12V to 5V switching power regulator using only through-hole components that can be soldered to a nice protoboard. For my purposes, I need to provide 0.25A - 0.5A. Maybe 0.75A max but I doubt it. I started with the LM2675. Without making one before and only having the datasheet and google, I wanted to know if I selected proper components before I pull trigger. I will follow the manufacturers typical application schematic.

L1: 2100HT-680-V-RC -  68uH, 5.1A, 44 mOhm DCR, 5.1 Idc

Cout: RR71C680MDN1  -  68uF, 16V, 7mOhm ESR

Cin: ESY107M025AE3AA  -  100uF, 25V, 130mOhm ESR

I've read a lot of recommendations to use ceramic caps for their low ESR but almost always find aluminum electrolytic caps used elsewhere. Cout was chosen for its very low ESR, but is the ESR value of Cout low enough? Are there other specifications of the capacitors I am not considering? Correct me if I'm wrong but I think the inductor should be more than good for my use. Any input would be greatly appreciated!


texts: I am planning to fix my broken headphones. They don´t really work in my laptop unless I twist the plug-in wire to a certain position and hold them there. I think it´s just a broken wire somewhere close to the plug-in? I was thinking of cutting the wire close to the plug-in and solder the wires to a new plug-in. Do you think my assumptions are correct? What are the best tools to use for this task?


texts: Complete summary of all protection in a circuit?

texts:
this is what I have learned and I wanted to know if you can add more to my current understanding in protection.

For short circuit (which applies both to overvoltage and overcurrent): Use a fuse first and then a tvs diode.

For reverse protection: a diode will suffice

Is there any other protection that can be added to a circuitry?
This is a general question.


texts:
I've been using a Motoman and I'm wondering what is the best way to recover when the encoder position has been lost.

I've tried lining up all the reference marks on the joins but this can be a bit dodgy.


texts: Does a Lyapunov Function derivative necessarily vanish at each equilibrium point of the system?

texts:
From Jean-Jacques E Slotine's book "APPLIED NONLINEAR CONTROL"
"several Lyapunov functions may exist for a given system, and therefore several associated invariant sets may be derived. The system then converges to the (necessarily non-empty) intersection of the invariant sets M, which may give a more precise result than that obtained from any of the Lyapunov functions taken separately. "
I understand that invariant sets can vary from a Lyapunov function to another, but does a Lyapunov function necessarily show a maximum or minimum at every equilibrium points of the system?


texts: Three-way AC switch indicator without adding a wire

texts:
I am dealing with some three-way light switches that people are always forgetting to turn off.

Any suggestions/schematics for making a simple LED indicator at each switch to indicate if the circuit is on or off, which doesn't require an extra wire for the indicator?  (The wiring is already installed and covered, so adding wires is not feasible.)

I would prefer mains-powered solutions (no batteries).

Update:
Here's how it's currently wired.  We use 14/3 with ground (4 conductors in the cable, not allowed to use the earth ground as a neutral).  In the US we're required to have a neutral in all switch boxes, and are required to break the hot wire with all switches.

simulate this circuit – Schematic created using CircuitLab

These circuits are switching 120VAC 60HZ USA electrical mains.

Thank you!


texts: What is the exact difference between synchronous and asynchronous serial transmission?

texts:
I'm having a hard time understanding the exact distinction between synchronous and asynchronous serial because different sources have confusing description.

For example, some source say a separate clock wire is required in synchronous, some do not mention a separate clock but a SYN character instead. Some source say asynchronous requires start and stop bits, some say not necessarily as long as there is only a pair of wire.

So my question:

1) Is clock wire always needed in synchronous serial? If not, how do we synchronize?

2) When we say asynchronous, does it always mean we use start and stop bits? If not, how do we synchronize?


texts: I have 2 Trojan T105 6 volt batteries that are 3 months old connected in series for 12 volts. I inadvertently discharged them to 4 volts(!) by leaving an inverter turned on without anything drawing off it,(it takes .26 amps just on) and not having my battery charger turned on. When I went to the boat and discovered they were at 4 volts, I turned the charger on, and they took a charge. They seem to be holding it, but I'm concerned. What damage might I have done to the batteries? Any thoughts???


texts:
The beauty of transistor structure lies in its different areas of each of the layers. Also, the base layer is kept between collector and emitter. We can say that the base acts just like a ‘door’ for the transfer of electrons from emitter to collector through it. When base voltage increases, this ‘door’ opens wider and more number of electrons are allowed to flow through it.
  The area of base layer is deliberately kept small because of two reasons. First, it creates strong repulsive forces among the crowded electrons in base layer. When electrons from emitter layer come into base layer, they get trapped, as they cannot go back, due to repulsive force of negative ions of base layer near B-E junction. In base layer they find very small number of holes to recombine. The base voltage is also small. So very small number of electrons are attracted towards positive terminal of Vbe battery.
  Eventually, all these electrons crowded in base layer have but one option, to surmount the ‘gap’ of C-B junction and enter into collector layer. But this junction is already reverse biased (note the polarity connections of Vcb battery). Now how they will jump over this ‘large gap’ of C-B junction? They will jump this gap because, the strong positive electric field of collector layer is ‘inviting’ them or attracting them. So with two forces: one is mutual repulsive force among them in base layer and one is the strong attractive force from collector layer, they succeed to surmount this large gap of C-B junction and enter into collector layer.

(Original source for diagram and text above)

I am just a beginner in Semiconductors so I just had some doubts when I read the above statement, which include:

1) What the base voltage really is Vcb or Vbe and also base current?
2) Why does increasing base voltage increase the number of electrons?
3) What really happens in collector region? I am confused about how they explained above.

This is a common base configuration


texts:
I have a atmega32u4 from factory with dfu inside. The HWB is pull down, and RESET pin is pull up.

The first USB plug, dfu programmer appears on my Linux box. I upload the firmware without problem. Now, every time I plug my atmega to USB the application runs first, instead of dfu. But, when reset mcu by software, the bootloader code runs.

According to datasheet, default fuses are : BOOTRST = 1 and HWBE = 0. With this fuses and signals, the expected behaviour should be always the first one as the image show.

I don't know why reset by software, the bootloader runs.


texts: Why I do not need to ensure I have no latches in sequential process [VHDL]

texts: As far as I know, it is a bad practice in combination processes to use latches, and that I should assign value to every signal in any case. Why the same rule doesn't stand for sequential processes (by these i mean clock processes) and why I am not warned that for certain signals I don't assign values for?


texts:
I'm writing some code for a Texas Instruments Stellaris Launchpad board (a Cortex-M4F, the chip is a LM4F120H5QR). I'm using the IRMP library for infrared decoding, which works fine, as long as I don't use any floating point math outside of its ISR. Just a single operation such as in

MAP_SysCtlDelay((MAP_SysCtlClockGet())/ 30.0);

breaks the IRMP library. The chip still runs, IRMP calls all its required functions, UART transmissions work, but IRMP can't decode any infrared reception anymore.

At the very top of my main function I've got:

  // Enable FPU
  MAP_FPULazyStackingEnable();
  MAP_FPUEnable ();

In fact, if I comment out those lines, the software just hangs during intialization.

I've tried several flavours of those FPU enabling functions (ROM_, MAP_, FPUStackingEnable, FPULazyEnable), but nothing seems to fix the problem.

The past 4 hours of Googling have proven useless, so I was hoping to find an answer here.

Edit: More weirdness: if I compile with -O0, IRMP doesn't decode anything either. As soon as I set optimizations to O1 or higher, it starts working again (provided no floating point arithmetic takes place outside of the timer ISR routine and the functions it calls).

Oh, and in case it helps, arm-none-eabi-gcc --version gives:

arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 4.7.3 20121207 (release) [ARM/embedded-4_7-branch revision 194305]

I'm compiling with the following options:

-DPART_LM4F120H5QR -DARM_MATH_CM4 -DTARGET_IS_BLIZZARD_RA1 -I$SOMEDIR/stellarisware
-Os -Wall -std=gnu99 -c -fmessage-length=0 -fsingle-precision-constant -mcpu=cortex-m4
-mfpu=fpv4-sp-d16 -mthumb -mfloat-abi=softfp -ffunction-sections -fdata-sections

Edit 2: I should add that no actual floating point calculations happen in the IRMP code. That is to say: all variables are integers. However, there are a lot of defines which are intermediate floats, e.g.:

#define IRMP_KEY_REPETITION_LEN (uint16_t)(F_INTERRUPTS * 150.0e-3 + 0.5)

These constants are compared with other uint16_t types in the actual code. I'm not quite sure why this requires FP arithmetic in the run-time code, it's all fixed values which can be folded into integers.


texts: How can we prove that collector current in active region is higher than the saturation region?

texts:
In the VI characteristics of BJT transistor its showing that the collector current in saturation region is less than the collector current in active region.

How can we prove it with a BJT circuit?


texts:
I need to design a step-up converter with following specs:

vin = 12V +/- 10%
vout = 110V
iout = 0.11A
non-isolated

The most problematic constraint is that the converter must be very compact. Component height is limited to 10mm or thereabouts and PCB space roughly 25mm x 45mm.

Designing such a converter would otherwise be a moderately complex task, but I'm wondering how to reduce the physical size. Multiplied boost and full-bridge forward come to mind.


texts:
What do the symbols for components L1 (FB) and MV1 mean in the schematics below?

What does MV and FB mean?


texts: Does leakage reactance of transformer depend on quantum of load?

texts:
In a single phase transformer, considering copper losses and core losses, I want to find whether the leakage reactance is affected by change in load on the secondary?

I was unable to find an answer on the Internet.


texts:
Please bear with me as this is my first time working with filters.

I am trying to scale down the voltage from my piezo to a voltage which my ADC can read (from >100V on the piezo to 0-5V on the ADC inputs). Reading older threads on voltage dividers and ADC inputs, it was suggested that I use a buffer after my voltage divider in order to create a low impedance output for the ADC.

EDIT: The two resistors should be swapped, did not notice it until it was pointed out to me.

(I used a capacitor to represent the piezoelectric because I couldn't find a piezo symbol in Tina)

I have been testing my circuit with a much smaller impact that produces voltages of ~1V on the piezo, and have noticed that there is a huge amount of noise on the output of the buffer.

Orange in the above picture is the original signal, measuring directly across the piezo

Green in the above picture is the signal after it leaves the buffer

Figuring that it was an issue of high frequency noise, I attempted to filter the data in Python, using a 1st order butterworth filter with a cutoff of 10kHz and a sampling frequency of 50MHz (The sampling frequency of the oscilloscope)

Red is the original signal, blue is the buffer output after going through a lowpass filter (This was a seperate hit on the piezo, so it doesn't match the previous picture)

Considering that I need the ability to do this in real time, I needed to build an analog low pass filter. From my understanding, the calculation is that

$$
F_c = \frac 1 {2\pi RC}
$$

So I used \$ F_c = 10kHz \$ , C = 0.1uF and R = 150\$\Omega\$ in order to get an actual \$ F_c \$ of 10.6Khz.

However, instead of getting a nice, smoothed out signal like in Python, I get this:

The orange is the signal from the piezo and the green is the output of the buffer. As you can see, the low pass filter seems to have had smoothed out the actual signal while leaving the noise behind!

Now what I want is the following:

What am I doing wrong that is causing the low pass filter to filter out the signal?
Why is the buffer output so noisy? I chose this buffer because it is supposed to be unity gain stable.
What could I do to alleviate the noise and keep the signal? Would using an active filter instead help?

Thank you, and sorry for the wall of text.


texts:
Okay really need help on constructing a MOSFET based H-bridge circuit with a switch.
I've got two p type and two n type mosfets.

I understand you have to apply voltage to the gates to turn the transistors on but I'm not sure how you turn certain transistors ON while leaving others OFF.

Also wiring and connecting the circuit up on a breadboard, I get you should have a resistor before the gate to protect the transistors? And I believe the source pin of the MOSFET just connects to ground? Does the drain just connect to the motor? Having trouble understand how and where to connect the components.
Also need to incorporate a switch that allows the direction of the motor to be selected.
Please I need some help, backed into a corner here!


texts: Sending simple video feed over wifi with ESP32 dev board and fpv camera

texts:
Im wondering if its possible for an ESP-WROOM-32 dev board to take ntsc video as an input and then stream it over wifi to a seperate server on the network. The video would be in ntsc format over a single wire from an fpv drone camera.
My main specific uncertainties/questions are:

A. Wether or not the ESP32 can take a video input from a camera like that.
B. What video processing would be necessary to make that signal good to send over wifi and then be saved to an hdd in the server.
C. Would that processing need to be on the server side or the ESP32. I have access to more hardware like fpga's and arduinos if those are more applicable to the task. I also have a raspberry pi but im hoping for these esp32/cam packages to be smaller/more inexpensive than that would be.

Notes;

my esp32 board
similar cam to the ones i have

VGA: 720 *480 - Horizontal resolution: 600TVL

Im coming here after not finding anything conclusive in searches besides information on the ESP32-CAM module and some other projects, which is an option but i would prefer to do this project with parts i already have on hand. Sorry if this question has an obvious answer, im still new to this side of things.


texts: DRAM -> However all I want is the capacitor array, (or does a circuit like this even exist)?

texts:
Sorry, this is a very odd question, I've however exhausted my google-fu and I don't even know what question to ask to get the information that I'm looking for. (I'm a programmer so pardon the lack of electronics lingo, as this isn't my specialization).

I'm looking for a component that has the same setup as a dram chip (specifically the capacitor array and if possible the row/column decoder for addressing). I need to store a series of analog low voltage values for a very brief period of time (and signal loss as the capacitor 'bleeds' is acceptable).

Does a circuit like this exist? If so what's it called?

Ps. I'm asking from a programmer perspective, however I need something like this for a project I'm working on. Any help with a starting block would be huge, even a name of a component that has that setup.


texts: The resistance and magnetising reactance of the core

texts:
I did an experiment where I varied the test voltage and determine the values of the  resistance and magnetising reactance of the core. What I noticed is that their values actually vary (not constant).
Ideally speaking, shouldn't their values be constant regardless of the test voltage (while they vary in practice)?