texts: Switch high voltage with triggered spark gap

texts:
I want to switch a high current/voltage pulse (up to few 10kV, <1kA) from a capacitor as supply. It needs to be cheap and I don't care about efficiency too much yet.

I took a look at using thyristors in series but I think it'll cost too much and could possibly be dangerous as without the correct balancing the thyristors break. I found old Thyratron tubes that I think would work, however I couldn't find them to buy (let alone buying newly made ones that are made for power electronics).

From the search of the vacuum tubes and getting to know all available tech I decided it would be cheapest to use a triggered spark gap.

Do gas discharge tubes (i.e. https://www.littelfuse.com/products/gas-discharge-tubes/high-voltage-gdt/cg3.aspx) work like a spark gap? My idea is to have a high voltage GDT in series with a smaller voltage triggered spark gap (i.e. https://uk.rs-online.com/web/p/gas-discharge-tubes/7606807/ / or homemade). I would then balance the voltage with resistors in parallel. I imagined to have it like this:

(I used a thyristor symbol as I couldn't find any triggered spark gap symbol.)

My thought is that by this arrangement the voltage supplied would divide to ~9 parts over the spark gap and ~1 part to the switch (when it is off). When the switch opens the resistance drops and the voltage over the spark gap rises creating an arc (when the voltage is sufficient). I know the resistance values are too low for above specs but this circuit is only for reference.

Would such approach work for switching an energy pulse of above specs?
(I didn't calculate the duration of the pulse yet, but I'd be surprised if the cap held for long as the spark gap would no longer arc at some point.)
If not please point out why and maybe guide me in a direction how I could realize this with cheap parts.


texts:
I would like to build a sinus frequency generator that can be controlled via an Arduino. Sinus frequency would be in the low frequency regime (below 100 Hz) with a voltage around 2.5 Volts peak to peak.

I will have to use the SPI interface SPI tutorial for other purposes at my Arduino. Therefore an external IC that can be controlled via SPI is not feasible.

Additionally I would like to avoid the DDS (Digital Direct Synthesis) possibility as I would like to externalize the frequency generation.

So perhaps the sinus generation should be made with some of the standard oscillators like Wien bridge etc.

Can somebody give me a link for a circuit that fulfills my requirements and that can be controlled with an Arduino Uno?

With control I mean:

On/off
Frequency (this is not a must but a nice to have)
Amplitude

With "I would like to externalize the frequency generation" I mean:
keep the programming logic inside Arduino clean of too much things, that a dedicated device can do better.
If I use hardware instead of software, I expect to have a less fragile setup regarding timing. If other time critical extensions come up, I have more "headroom" for them.


texts: ADS4249 from Texas Instruments output clock

texts:
The ADS4249 supports both LVDS and LVCMOS outputs. It has an input clock (CLKP) and an output clock (CLKOUTP). The input clock can be a LVCMOS or LVDS signal. My question is does the output clock depend on the input clocks signal type?
Lets say my input clock is LVCMOS can I still choose LVDS for the output clock?
datasheet: https://www.ti.com/lit/ds/symlink/ads4249.pdf?HQS=TI-null-null-mousermode-df-pf-null-wwe&ts=1602449719072&ref_url=https%253A%252F%252Fwww.mouser.de%252F


texts: Impedance Expression for a Transmission Line

texts:
I'm studying transmission line theory and this is the expression I derived for the input impedance for a lossless transmission line:

$$
Z(\omega) = Z_{\inf} \frac{1+e^{i\frac{\pi\omega}{\omega_{0}}}}{1-e^{i\frac{\pi\omega}{\omega_{0}}}}
$$

where
$$
Z_{\inf}=\sqrt{L/C}
$$
is the wave impedance and
$$
\omega_0=\frac{\pi/2}{\sqrt{LC}}
$$
is the quarter-wavelength resonance frequency.

Now, I found this other expression very similar to mine but I'm not able to figure out if they are the same or not and eventually which one is correct

$$
Z(\omega) = Z_{\inf} \frac{e^{i\frac{\pi\omega}{\omega_{0}}}-1}{e^{i\frac{\pi\omega}{\omega_{0}}}+1}
$$


texts: Why to calculate base voltage in given example differently?

texts:
In this problem as we can see base voltage is 3 V (simple voltage divider)

But in other problem but goes under saturation, but here in solution they didn't use voltage divider and use other approach
Taking base voltage as Vb and then emitter voltage Vb+0.7 and collector voltage as Vb+0.7
Here answer comes is different then previous case Vb.
So here my question is why can't we can't attack this question with voltage divider? Why have to take different approach? Why answer is different than previous one?


texts: How to calculate the maximum Torque for a PMSM Motor?

texts:
I have a cheap BLDC/PMSM Motor from Ebay. I don't have any further Information, only a sticker: "A2212/10T 1400KV".
I connected my oscilloscope to 2 phases of the motor and I have seen that the Back EMF is sinusoidal, so I think its a PMSM.
Then I made the following measurement, for 10 Hz rotation speed the Back EMF was 800 mV Pk-Pk and 71 Hz Freq.
So I calculated \$Kq = \frac{Vpk-pk}{4\times π \times \sqrt 3 \times Freqbemf}  = 5.228\times 10^{-4}\$
and
\$pole pairs = \frac{(60 \times Freqbemf )}{RPM} = \frac{71}{10} = 7.1 ~= 7\$
Is this correct?
How can I calculate max torque, psim?


texts: NOR Flash Memory Full chip vs Block vs Sector Erase

texts:
I am trying to use a NOR flash memory device: SST25VF016B (with STM32 discoveryboard F407VG). However, I am confused on some terms on their datasheet. You can find the datasheet here: https://www.elfa.se/Web/Downloads/_t/ds/SST25VF016Bx_eng_tds.pdf

In the datasheet, it is mentioned that this device have 16Mega bits of memory. However, in the erase section, it state that it has:
1. Full Chip Erase
2. 4KByte sector erase
3. 32 Kbyte block erase
4. 64 Kbyte block erase

What I understand after looking some references is that sector is the smallest section in a memory device, and then we have blocks. But, in that case, 4KByte sector means that it will erase from address 0 for example, until address 4000?

And one more question, when I tried to program this device, it said that we need to erase the chip first before programming. Will it be the same if I use the full chip erase, or should I erase it block by block (or sector by sector)

Can someone help me try to understand this? Thanks a lot!!

Cheers


texts: Arduino Uno to ATtiny44A I2C communication

texts:
I tried to make I2C communication from Arduino Uno to ATtiny44A.

Uno as Master and Transmitter code:

#include <Wire.h>

#define LED_PIN 13
byte x = 0;

void setup()
{
  Wire.begin(); // Start I2C Bus as Master
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

}
void loop()
{

  Wire.beginTransmission(0x26); // transmit to device #9
  Wire.write(x);              // sends x
  Wire.endTransmission();    // stop transmitting
  x++;
  if (x > 5) x=0;
  delay(450);
}

ATtiny44A Slave/Receiver code:

#include "TinyWireS.h"                  // wrapper class for I2C slave routines

#define I2C_SLAVE_ADDR  0x26            // i2c slave address (38)
#define LED1_PIN         10

void setup(){
  pinMode(LED1_PIN,OUTPUT);             // for general DEBUG use

  TinyWireS.begin(I2C_SLAVE_ADDR);      // init I2C Slave mode
}

void loop(){
  byte byteRcvd = 0;
  if (TinyWireS.available()){           // got I2C input!
    byteRcvd = TinyWireS.receive();     // get the byte from master

            if(byteRcvd == 5){
              digitalWrite(LED1_PIN,HIGH);
              delay(1000);
            }
            else{
              digitalWrite(LED1_PIN,LOW);
            }
  }
}

Am I doing something wrong? The LED does not blink. What are the other ways to debug ATtiny?


texts: Are there any instruments that can be used to measure the stored energy across a capacitor?

texts: Apologies if this a noob question but I was wondering if there was a way I could directly measure the energy across a capacitor in Multisim so that I can compare it with my analytical result.


texts: Frequency design parameter for DC signals

texts:
I have been using some online tools to design a circuit to amplify photo-diode current. I have understood that all such tools needs a frequency/bandwidth to drive the calculations.

For example, a Low Pass circuit has a "frequency" parameter in it. OP Amps describe there performance for different frequencies but I am interested in a DC voltage. The tools forces to choose frequency greater than 0. Why is this?

Example of tools:

http://www.analog.com/designtools/en/filterwizard/

http://sim.okawa-denshi.jp/en/CRlowkeisan.htm


texts:
Is it possible to make bi-polar square signal from PWM signal?

Im talking about 40 kHz frequency and 0.5v /-0.5v peak to peak signal.

The PWM dose is %50. And the PWM frequency is 40 kHz too. The PWM is generated with an Atmel MCU with no extra parts. The MCU digital pins are rated at 5V.


texts: Why is the reason of using BJTs instead of diodes in Bandgap references?

texts: I'm just asking what is the main reason to use BJT transistors as pn or np junctions for bandgap voltage reference instead of using just pn or np diodes also available on CMOS technologies.


texts:
I'm preparing for a test and I currently stuck with the following question.

We have a 6502 microprocessor. For the execution of an absolute jump the jump address with the address high byte (ADH) and the address low byte (ADL) are loaded into the program counter (PCH,PCL).
The question is now, why cannot both address bytes be loaded into the PC, but instead the ADL has to be stored first in the data buffer?


texts: How to generate UART interrupt for GPIOs?

texts:
I am using PIC32 and I have few inputs. I want a UART Tx Interrupt to fire whenever any input becomes HIGH. I have somehow manged to write  code for UART tx and rx interrupt and its working but I don't have an idea how to implement it for my application.

int main()
{
  //configure UART
UARTConfigure(UART1, UART_ENABLE_PINS_TX_RX_ONLY);
UARTSetFifoMode(UART1, UART_INTERRUPT_ON_TX_NOT_FULL | UART_INTERRUPT_ON_RX_NOT_EMPTY);
UARTSetLineControl(UART1, UART_DATA_SIZE_8_BITS | UART_PARITY_NONE | UART_STOP_BITS_1);
UARTSetDataRate(UART1, FPB, 115200);
UARTEnable(UART1, UART_ENABLE_FLAGS(UART_PERIPHERAL | UART_RX | UART_TX));

// Configure UART  Interrupt
INTEnable(INT_SOURCE_UART_RX(UART1), INT_ENABLED);
INTSetVectorPriority(INT_VECTOR_UART(UART1), INT_PRIORITY_LEVEL_2);
INTSetVectorSubPriority(INT_VECTOR_UART(UART1), INT_SUB_PRIORITY_LEVEL_0);

// Enable multi-vector interrupts
INTConfigureSystem(INT_SYSTEM_CONFIG_MULT_VECTOR);
INTEnableInterrupts();

 while(1)
{
  //main code
}

}

void __ISR(_UART1_VECTOR, ipl2) IntUart1Handler(void)
{
// RX interrupt
if(INTGetFlag(INT_SOURCE_UART_RX(UART1)))
{
        // Clear the RX interrupt Flag
    INTClearFlag(INT_SOURCE_UART_RX(UART1));

        // Echo what we just received.
    char RxBuffer[5];
    if((U1STAbits.URXDA)!=0)
    {
        getsUART1(5,RxBuffer , 123);
        U1STAbits.URXDA = 0;
        U1STAbits.OERR = 0;
        putsUART1(RxBuffer);
        putsUART1("\n");
        memset(RxBuffer,0,5*sizeof(char));

    }

}

// TX interrupt
if ( INTGetFlag(INT_SOURCE_UART_TX(UART1)) )
{
        INTClearFlag(INT_SOURCE_UART_TX(UART1));

}
}

I don't know what logic should I made so that if any inputs become HIGH, lets say

if(INPUT1 == HIGH)
{
  //generate UART tx interrupt
}

Please help. Thanks!


texts: What battery should I use in a remote control for a score marker?

texts:
I need help in choosing the right battery for my project.
I built a ping pong score marker for my school two years ago.
It is separated in two parts:

The score marker. It has the displays, an Arduino Mega and the drivers for the displays.
The control. It has the buttons to reset, go to the next set, and add or deduct a point to each player.

The control is connected to the score marker with a Ethernet cable.

Now I want to improve it by making the control wireless.

I need a battery that hold the charge for long periods of time.
The batteries only need to provide 45 mA at most.

I'm thinking to choose the 18650. Is it the right choice, or should I go for a LiPo, those that are commonly used in RC airplanes?


texts: Mechanically damaged capacitor leaked liquid - is it toxic?

texts:
I have mechanically damaged a capacitor on an old motherboard and it made a PFFFT sound like some gas went out of it and then some liquid leaked. What is that? Is it toxic? I hope that it was not mercury!

The capacitor is of a cylindric shape with two wires at bottom, about 7mm in diameter.


texts: Emulating an SD-Card with a microcontroller (or Raspberry Pi)

texts:
I'm thinking how I could emulate an SD card with a microcontroller or RaspberryPi and dynamically change the contents of the "SD" on the go. The microcontroller would be connected to the SD reader and it would be recognised as a card. The idea then is to stream data to a media file (mp3 for example) just like online streaming where the file is appended while being played.
Is something like that possible? How could I emulate an SD?


texts:
Last few months I am working on personal project -- I want to measure weight of beehive during the year and then save the results. Beehives has usually from 100 to 200 kg and during one day, the weight can change from -5 to +5 kg. The ideal precision should be 100 g.

I have working prototype with MCU, amplifier and one 20 kg load cell. I put beehive on mechanical platform and weight is scaled down in 1:10 ratio -- thus I can measure 200 kg weight. The precision has to be 10 g.

The results from my prototype are:

My cheap load cell changes its output with temperature (I expected this, I can correct the results when I save temperature together with weight).
The output of load cell drifts with time. I put 3 kg weight directly on load cell and after few days, the output was much lower than first day. I think this is called creep?

The second issue is problem, because load cell has to measure weight during whole year so it will be under permanent pressure.

Should I buy more expensive load cell? Are load cells designed for permanent load? Or should I look for another method how to measure weight?

I was thinking about precision multi turn potentiometer. I am not mechanical engineer, but if I can easily change weight into movement, I may be able to use potentiometer as weight sensor.

Or maybe use spring instead of load cell. But how can I convert spring deformation into electrical signal? Spring compress with more weight, so maybe some kind of distance sensor?


texts: Reversing a DC motor with an on-off switch, relays, and limit switches

texts:
First post here, please excuse my electronic ignorance.

I am trying to design a 12V circuit to open and close the nitrous bottle on my race car. Here are the specifics of the design: It needs to

open the bottle (CW motor) when the SPST switch is in the on position, stopping when it reaches a limit switch to prevent the motor from burning up.
close the bottle (CCW motor) when switched to "off", again stopping on a limit switch.

The reason for the SPST switch is that the rest of the nitrous controls on the panel are the same type of switch and I don't want to have one oddball switch that doesn't match. I would prefer to use relays to prevent running the motor current through the switch(es), and have obtained 2 automotive grade SPDT relays for this purpose. I found circuits for a SPDT activation switch, and another for continuous automatic reversing, but I need it to stop when the bottle is open, and not reverse until the switch is turned off. I don't mind adding components as long as they are automotive-rated. The no-load current for the gear-driven motor is 230 mA.
Am I overbuilding it to use relays?


texts:
I would like help figuring out what type of cable and connector are shown in the images.  I have a robotic cd autoloader and the arm stopped working properly and this cable shows signs of wear.  Any help is appreciated.  I know this is a 10 pin cable but I'm not sure what it's actually called.  Is this a standard cable with connectors?  Mine is about 18" long.  If it's not a standard cable is there a person who can make this for me?

Thanks,

Daniel


texts: generate high voltage using LM555 with a transformer

texts:
I'm a French student (please forgive my bad English spelling) who works on a system of portable echograph (you can find the information of the project on the wiki of echopen). Could you help me please?

I would like to generate a tension of 100V. First, I took a transformer from a system which is used to transform 230v to 12v. I tested it with a frequency generator to determine the inductance of the coil and the transformation coefficient:

L1 = 11.13mH
L2 = 31.89 mH

I saw that at 13kHz the voltage was higher.
I transformed 15Vpp to 110V and I wanted to integrate it into a system which used 10v.
So, I used a LM555 component to have a oscillating circuit.

The circuit I used:

My observation and problem:

I want to use a MOSFET to control the 10v but the voltage is dropping
The generating voltage from the transformer is not enough maybe I
need two elevation stages
When I plug the transformer, the square wave signal is distorted
I can't have more than 50V from the transformer (I have more using
the frequency generator)

You can find my work on this page

Edit: I forgot to tell, I can't have more than 50V from the transformer using the oscillating circuit, with the frequency generator I have 100V from 15Vpp (the problem is the tension dropping with a load resistance I suppose the frequency generator don't have power enough)

Edit 2 (02/31/2015) : this circuit works thanks a lot to everybody and especially "jp314", I have 130V from 12v!


texts:
I am having a hard time understanding how a JK latch turns on for the first time. For example, if we use a JK latch with NOR gates. We have something like this:

Let's suppose that \$Q\$ and \$J\$ is initially 1. Since \$\bar{Q}\$ is 0 and feeds back into \$J\$, wouldn't the 3-input \$J\$-AND gate immediately go back to 0, or toggle between 0/1 indefinitely? What prevents that? Or does that not matter because the NOR gate is already set and feeding back unto itself?


texts: Why does Xilinx Translate for Virtex-6 not know IOSTANDARD LVDS?

texts:
I'm using several Xilinx FPGAs and boards from Spartan3E up to KC705/VC707 and I'm very familiar with UCF files, but there is one question that bothers me...

Why does translate for Virtex-6 not know IOSTANDARD LVDS, but translate for Series7 does?

or

Should I use IOSTANDARD LVDS_15 on KC705 for sysclk instead of LVDS?

Here is the correct UCF snippet for a KC705 board's SystemClock:

##  Bank:           33 - VCC=1.5V (VCC1V5_FPGA)
##  Location:       U6 (SIT9102)
##      Vendor:     SiTime
##      Device:     SIT9102AI-243N25E200.0000 - 1 to 220 MHz High Performance Oscillator
##      Frequency:  200 MHz, 50ppm
NET "KC705_SystemClock_200MHz_n"    LOC = "AD11";               ## {IN} U6.5
NET "KC705_SystemClock_200MHz_p"    LOC = "AD12";               ## {IN} U6.4
NET "KC705_SystemClock_200MHz_?"    IOSTANDARD = LVDS;
NET "KC705_SystemClock_200MHz_p"    TNM_NET = "NET_SystemClock_200MHz";

And here is an accepted UCF snippet for a ML605 board's SystemClock:

##  Bank:           34 - VCCO=2.5V (VCC2V5)
##  Location:       U11 (SIT9102)
##      Vendor:     SiTime
##      Device:     SiT9102 - 1 to 220 MHz High Performance Oscillator
##      Frequency:  200 MHz, 50ppm
NET "ML605_SystemClock_200MHz_n"    LOC = "H9";                 ## {IN} U11.5
NET "ML605_SystemClock_200MHz_p"    LOC = "J9";                 ## {IN} U11.4
NET "ML605_SystemClock_200MHz_?"    IOSTANDARD = LVDS_25;
NET "ML605_SystemClock_200MHz_p"    TNM_NET = "NET_SystemClock_200MHz";

Normally, an I/O standard is associated with a voltage so STA can calculate the correct timings. Further more I saw many differential clocks feed into FPGAs with AC-coupling (e.g. from ICS844021I for SGMII).

But when we look into both schematics, we can't find an AC-coupling for sysclk:
- ML605 Schematic
- KC705 Schematic

Normally, I would say LVDS should be used if AC-coupled and LVDS_xx should be used if DC-coupled. But the KC705's UCF says the contrary.

Can anyone explain when LVDS should be used?

P.S.
1. The KC705 snippet is from KC705 master-XDC incl. IO standards
2. The ML605 master-UCF is shipped without IO standards


texts:
I am trying to use the bus pirate to read the ESMT F25L004A flash chip, looking at the datasheet here. http://www.esmt.com.tw/db/manager/upload/f25l004.pdf I see that the documentation says the opt code to read from the device is 0x03 000000 where 000000 is the beginning address. However the data sheet also describes some sort of Block addressing that I am not sure how to account for.

M5
App defaults except for Normal (H=3.3V, L=GND)

Is the correct syntax? I want to read one byte,

  [ 0x03 000000 r:1 ]


texts:
In various circuits intended for use with 230-250 V AC I've seen capacitors labelled as "400V"
(Examples: 1, 2)

When I look at Capacitor specifications, they often give separate AC and DC ratings. For example:

X1 440 VAC 1000 VDC
X2 350 VAC
Y2 400V
(but package confusingly marked "Y2 (330V~) X1 (440 V~) .. (250 V~)")

(I believe an X-rated cap is designed for use across AC supply live-neutral)

Should I take the "400V" on the diagram as a DC or AC indication?

Am I right in thinking a 350 VAC rated X2 cap is perfectly suitable for 50Hz 240 VAC at say 10 mA?


texts:
I seem to be getting a problem with some coax cables I am using. I suspect that the rotatable ring that connects to shield is not making good contact. I am using it to carry a 120kHz sine wave signal, and I see dropouts when the ring is rotated slightly. Voltage is typically in the high tens of mV.

Is this typical or have I just got some bad cables?


texts: Bypass capacitors needed in low-frequency digital logic systems?

texts:
I know it's good practice to use bypass capacitors near the power pins of your ICs, but I'm now moving on from the breadboarding stage to the PCB-design stage, and I'd like to know if there are any good rules of thumb for when the caps are actually needed (I don't want to waste any PCB real-estate).

For example, what if I have a simple counter IC fed by a 250KHz clock signal?  31.25 kHz?  If all input and output signals of an IC are changing at sufficiently low frequencies and if the IC doesn't draw much current, can I leave off the bypass caps?

Edit: inserted text in italic.


texts: ESP-12 (ESP8266) without the Metal Cover

texts: What is the effect of using the ESP12 WiFi module without the metal cover?


texts:
I've got a few of IRF610 power MOSFETs.
I've got a 12 V circuit which draws 1.90 A when running at max.
I was thinking I could move the current circuits GND line to the drain of the IRF610, connect the Source to the GND of the power supply, then connect +12 V though a 4N25 to the Gate. (Then controlling the 4N25 from a separate 5 V circuit to control if the 12 V circuit is on or off.)
What I'm wondering about is using +12 V for the gate, when it needs +10 V, is this doable or should I find something else?


texts: How to use more CPU power in Proteus simulations

texts:
Labcenter's people wrote in the help of proteus that for increasing the time speed on real time simulations usually we need to reduce the frequency of clocks or the frequency of peripherals in case of microcontrollers because of the mixed simulation, including in the cases where are possible change the property of analog components from analog to digital, specifically the mixed simulation problem comes because normally the microcontroller simulations has some signal conditioning which involves analog simulation.

What if instead of that I simply increase the quantity of available cores to Proteus of the computer's CPU?

I don't know if that is possible or it has been done previously por Labcenter's team but the help doesn'r mention any of that matter as far as I've read.

Is there any hidden or unhidden (what I didn't see) setting for making available more CPU power or cores to Proteus?

I've ran it an example project which shows the warning of simulation is not running in real time because of high CPU load but when I go to the performance window of Windows 10 the the CPU is loaded to an average of 26% aproximatelly like shown in the attached image.


texts:
I am involved in a project where we will be doing a run of about 200 products. We do not know where in the world our client will be sending these products.
Each product uses mostly off the shelf electronics:
orange pi
12V power supply (taking mains power)
touch screen
DC-DC converter
Arcade buttons
The only piece of custom hardware is a simple transistor circuit for each arcade button to turn on the LED.
My concern for the project, is the red tape when taking the project to different countries. What kind of certification would I need?


texts: On bus Ethernet, how a connected station detect link connectivity?

texts:
On point to point Ethernet, link pulse is used between 2 connected devices to detect link connectivity.

Reference

On bus Ethernet, how a station connected to Ethernet bus detect link connectivity?


texts: I'm an electronic eng student and for a design project I need to design a switch mode power supply. Catch is I can't use any off the shelf SMPS ICs, only opamps and logic. Rough specifications are 0-5v adjustable output, +-5% regulation, 20-30VDC input, 250mA constant current/protection. Can anyone point me in the direction of some resources for discrete SMPS design?


texts: How to get started with microcontrollers?

texts:
My point is not to start a flame war, or have an opinion based fight. I really just need advice based off of my experience.

I am pretty experienced with using an arduino, I understand C, & C++ fluently. What is a 8 bit microcontroller I could start with that would give me a solid foundation and understanding? I understand the programming and theory, but I am lacking practical experience. Besides the chip, do I need an IDE? or an IDE & a compiler?


texts:
I have an Ardunio controlling two CD74HC4051 muxes. The com terminals of both are connected, so I'm basically using the first mux to select a input, and passing the input to the next which selects the output. (I believe this is called demuxing?)

I am using an OSEPP Mega (Ardunio off brand) to provide the power, with the ports 53,52,51,50,49,48 connected to S2,S1,S0 (of the first mux) and S2,S1,S0(of the second mux) respectively.

I am having problems with it not sending signals through, or sending them through when it isn't supposed to. I am wondering if I am making any simple mistakes?

Here is a photo of the setup:

Here is my code:

void setup() {
  Serial.begin(9600);
  pinMode(53, OUTPUT);// 1S2
  pinMode(52, OUTPUT);// 1S1
  pinMode(51, OUTPUT);// 1S0
  pinMode(50, OUTPUT);// 2S2
  pinMode(49, OUTPUT);// 2S1
  pinMode(48, OUTPUT);// 2S0
}

void loop() {
  digitalWrite(53,LOW);//1s2
  digitalWrite(52,LOW);//1s1
  digitalWrite(51,LOW);//1s0
  digitalWrite(50,LOW);//2s2
  digitalWrite(49,LOW);//2s1
  digitalWrite(48,LOW);//2s0
}


texts: Why does a brushed DC motor current draw differ with direction of rotation?

texts:
I was trying to test the capacity of a battery pack I'm building and was trying to measure the current draw using a 35 turn 540 brushed DC motor (the website I had purchased from said something about it being sensored, but I couldn't find any sort of sensor inside.)  I read somewhere that the cuts/notched are related to some sensor.
I connected the DC 540 motor to a 1.2V 7000mAh NiCd battery and measured the current. In one direction it spins a bit faster and reads 1.58A and in other direction it spins a bit slower and draws 1.89A. Any idea what could be causing this?
Both the carbon brushes seem so have even wear on them, too.


texts: I have two components on a power supply board labelled GR1 and GR2 each having 4 pins. Are these opto isolators?


texts:
Why do we need isolated wires to get litz wire?

Doesn't usual multi-wire cable have same effect (probably less effective) due to air gaps between non-isolated individual wires?

I.e. shouldn't current concentrate on both copper<>air and copper<>insulation layers instead of just outer copper<>insulation layer?


texts: Will inverting amplifier's input impedance change if its output is saturated?

texts:
I found that when my inverting amplifier's output saturates, its input impedance becomes larger.
This is my schematic. As you can see on the left, when the inverting amplifier's gain is 10, with an input 1 volt 1kHz sine wave, the op-amp's output(not out1) will saturates(3.3V power supply), which I think will enlarge the inverting amplifier's input impedance, which is 10k(R1) if not saturates. I think so because the high pass filter created by C1 and Rin of inverting amplifier's cutoff frequency is not the same(lower) as C2 and R3, which on the right, without output saturates. You can see this for Vout1 and Vout2.

So am I right?


texts:
I'm trying to replicate the Nixie clock designed by Kevin Lee (https://0x7d.com/2017/nixie-tube-clock/). It uses a NXP PCA9685 PWM controller and a MSD42WT1G BJT to drive each tube cathode separately.

Here an extract of the scheme

The PWM signal is 5V and the voltage drop on the tube (when a cathode is conducting) should be around 133V. I don't know the "HV DC" anode voltage.

My questions are:
 1) When PWM out is high, the BJT is in forward active or in saturation mode?
 2) If it's in saturation (as I think), why R1 is placed between emitter and GND, and not between tube and collector?
 3) Here the author says

  For example, a 1K ohm resistor and Vb = 5V will result in Ve = ~4.4V and Ic = ~4.4mA regardless of Vc

but this should be possible only if in active mode, right? So the BJT is in active mode? If yes, why?
 4) Assuming Vce negligible, the collector current is (HV DC - 133)/1000?
 5) Is this the best way to arrange the circuit?
 6) If the transistor is used only as high voltage switch, is it better a BJT or a MOSFET?

Thank you for your help!


texts: Two questions about charge between capacitor plates

texts:
Let's say that we have capacitor with two identical plates - but one of them (let's call it plate A) is 50% of the size. Let's put a current through this capacitor so that there is some voltage V.

Questions:

Will the electrical charge between those two plates be the same?
Will electromagnetic current between those two plates be the same?


texts: What design considerations determine what kind of power supply I should use for a high-side FET?

texts:
I'm presently considering building a half-bridge converter, which means I have a transistor that's not tied to circuit common. To drive it, I'll need some voltage supply referenced to its source. This is a common problem with many switching topologies.

I'm aware of two general ways to power such a driver: a magnetically isolated DC/DC converter, or a bootstrap. But magnetic isolators still see some capacitive coupling across the isolation barrier, which can cause problems in the control circuit. And bootstrap converters can have EMI issues and only work if you switch a lower transistor often enough to recharge them.

All this is very vague in my head. Are there other ways of powering a high-side transistor drive? Are there other design considerations between the means I've mentioned?


texts: How can I reshape this PCB antenna so that I can still use it with the given circuit?

texts:
I'm borrowing the RF design from the MICRF114 Development Kit.

Here's user guide- http://ww1.microchip.com/downloads/en/DeviceDoc/50002433A.pdf

The circuit I'm using is on p. 35 and the antenna layout is on p. 21.

The issue I'm facing is that my board can only be 0.8" wide, but the antenna is 25mm (0.98") wide. I don't know enough about antenna theory to know what changes I can make to the antenna dimensions to shrink the width down, but still maintain the correct impedance.

Correct me if I'm wrong, but I think the primary consideration for resizing the antenna should be ensuring that the matching network is dimensioned properly to prevent reflections/losses in power transmission via the antenna.


texts: Which is the most accurate method to calculate the solenoid coil inductance?

texts: I generally use the Wheeler formula to calculate it. However, the accuracy is getting lower when I calculate bigger size coils. I am looking for a method that includes the pitch of the turns, and a more accurate calculation method for the bigger size coils.


texts:
I'd like to import a component library that I downloaded into my Kicad. I am running the latest Kicad for Windows as shown below. I have added the directory containing the library into the library search path. I even copied the library in to the global library directory within the installation location. And the component does not show up in my library browser!!

The answer on a similar question does not seem to work with this version of Kicad.

Application: kicad Version: (2015-01-16 BZR 5376)-product Release build wxWidgets: Version 3.0.0 (debug,wchar_t,compiler with C++ ABI 1002,GCC 4.8.2,wx containers,compatible with 2.8) Platform: Windows 7 (build 7601, Service Pack 1), 64-bit edition, 64 bit, Little endian, wxMSW Boost version: 1.54.0
         USE_WX_GRAPHICS_CONTEXT=OFF
         USE_WX_OVERLAY=OFF
         KICAD_SCRIPTING=ON
         KICAD_SCRIPTING_MODULES=ON
         KICAD_SCRIPTING_WXPYTHON=ON
         USE_FP_LIB_TABLE=HARD_CODED_ON
         BUILD_GITHUB_PLUGIN=ON
         KICAD_USE_WEBKIT=OFF


texts: What is a 'current filament' in a Gate Turn-Off Thyristor?

texts:
I’m reading a GTO document and I’m not able to understand this part:

"The anode current is crowded into higher and higher density filaments in most remote areas from the gate contact. This is the most critical phase in the GTO turn off process since highly localized high temperature regions can cause device failure unless these current filaments are quickly extinguished."


texts:
<img src="https://i.stack.imgur.com/thIbG.jpg" alt="side
" />I'm trying to identify a component marked simply as "R". There are two of these on a graphics card I am trying to fix that has a power issue. Thanks for any help...


texts: What does this symbol mean? It was found on a circuit board of an old projection tv

texts:
Two horizontal lines with three slashes in between.

_______
__\\\__

The bottom line is solid, I just couldn't find a way to draw it that way.


texts: How can we identify the type of sampling and mixing in any transistor circuit with feedback ? I have tried to do that but I couldn't. Please help me with the type of feedback in the image I post. If I am right that must be voltage sampling with current feedback


texts: Feedback schematic/pcb 16 channel relay wifi module

texts:
I have a few questions about a 16 channel relay module I designed, maybe someone can help me. Generally this consists of a ESP-12F, two I2C IO Expander, two darlington array ICs to drive 16x 5V relays.
Here is the whole project page.

Channel 9-16 is equivalente to 1-8. The whole mapping IO expander -> darlington array -> relay makes maybe no sense but this was the most convient for me and will be fixed in software.
Toplayer:

Bottomlayer:

Now my questions:

Will this thing work ? (I am sorry)
How do I calculate the power consumation of a single relay ? The datasheet states that the coil resistance would be 70Ohm. So at 5V this would be 357 mW, is there more to consider ?
How about the decoupling capacitors for both IO expander and the darltingon array ICs ? I just picked 0.1uF because I alreay had one in design and it can't harm but I am not sure if I need them and what size.
I am planning to use a 5V/3A power supply. Since the ESP-12F will use ~500mA worst case, all relays together ~1.1A if turned on and I am not sure about the rest. Does that sound sufficient ?
I used a 1000uF capacitor at the DC plug. I was worried how the timings are with the IO expander and the darlington array. I assumed the worst case where 8 relays turn on at the same time and maybe the power supply is too slow. Does that make sense ?
The ULN2803ADWR datasheet never shows a example where a single relay is driven by one IO. Did I even use the IC correctly ?

Datasheets:

LD1117/A
ESP-12F
ULN2803ADWR
PCF8574T
Relay (5V)


texts: Need To Understand Transistor Based Led Circuit

texts:
Which Transistor Topology Is Used in the Below Circuit & Why?
Need to understand the purpose of zener diode (ZD2) with 12.5 Vz and R1 with 2k value?
Why C1 & R2 is used for Q1 transistor?


texts: How can there be a non-zero voltage difference between Phase A on the left and Phase A on the right when they come from the same power source?

texts:
Hi StackExchange community,

Here I have a wiring diagram that represents a portion of a circuit found in a hospital.

The voltage difference was measured between phase A on the left and the phase A on the right and the voltage difference was found to be 120 V. The voltage difference between phase A on the left and phase A on the right should be 0 V.

Can anyone suggest possible reasons for this malfunction? A theory of mine was that the connections between phases may have been flipped somewhere along the way but I would appreciate some input.

Thank you.


texts: Designing small size AC/DC to provide 3.3 V for MCU

texts:
I have designed ESP8266 based light switch, that is controllable via web page or a push button. Light is being switched with use of Triac (TIC206) through optocoupler (MOC3041). Prototype works as intended. This is the concept:

simulate this circuit – Schematic created using CircuitLab

Now I need the advice on the power supply design. As it needs to fit into a quite a small case, the whole circuit needs to be small. I was considering the transformerless design, but it seems that most of designs are for lower currents.

MCU can draw around 200 mA. MOC3041 seems to require up to additional 60 mA.

I found some full bridge designs that claim to provide around 200mA but I am not sure if they are suitable for this purpose.

So basically I need 220V AC to 3.3V DC ~200 mA power supply, that is:

small
not dissipating a lot of heat (small case)
stable in 24/7 operation
not very expensive

What would you recommend?


texts: How efficient is a Peltier TEC1-12706 and TEC1-12715

texts:
I need to know some details about Peltier coolers before moving into making an air-conditioner.

I have watched several videos on YouTube that demonstrate making air-conditioners with Peltier thermo-electric coolers. They show that there is a decrease in temperature, on the cool side, which is about -10 °C to -20  °C.

We also know that Peltier coolers have an avg delta Tmax of ~65 °C.

But I am a bit confused about this Tmax. I think it is generally about 30-40 °C because in practice absolute conditions can't be maintained.

So, does the hot side temperature depend on the surrounding temperature?How much temperature decrease, would I get if the surrounding temperature is 40 °C with 12 Volts?

I also want to know if it is efficient for cooling a 10 ft x 10 ft room. I think using 5/6 Peltier cooler can handle that, but is it efficient? Or should I use a compressor?

And should I use only a heatsink with a fan, or a heatsink + fan + watercooler, for cooling the hot side?


texts: What's the point of board-internal differential pairs?

texts:
Sorry if this is an ignorant question.
But I just can't fathom what the advantages are of using a differential
pair for signals not leaving the PCB.
I mean, the usual argument for using a differential pair is to increase common mode noise immunity, which makes a lot of sense in cables and connections off the board due to all kinds of common mode noise that can exist in such environments. I just don't see the big advantage if the signal begins and ends on the same board. For instance, noise from adjacent traces couples asymmetrically to the pair, and one can probably say the same for broadside coupled traces. This obviously introduces noise in the differential signal. So why not just use a single ended signal and then increase the minimum distance to other traces if one wants less crosstalk?


texts: How best to interface with this bus switch from an ESP32

texts:
I am wondering how to interface with this bus switch from a ESP32. I need to drive OE1 and OE2 LOW at 5v , see datasheet

I know that I can only drive up to 3.3v from the ESP32 directly, so is there something I need in the middle here?

Also - Is it possible to drive both OE1 and OE2 pins low from one GPIO on the ESP32? It would be great to get a schematic for any suggested solutions.


texts:
I shorted by accident a circuit creating large voltage to my computer, luckily MBA has some sort of shorting protections -- yet this kind of thing should not happen. I would like to have a fuse between my microprocessor and my computer.

What are this kind of protection mechanisms called? USB fuse did not return anything in eBay so I am thinking I am trying to find things with wrong word.


texts: Byte-addressable RAM as opposed to word-addressable RAM

texts:
A couple of months ago I started working on developing my own computer to learn more about its low-level functionality, the design process and the architecture behind it. Although I look at real-world examples of other computers I try not to just copy, but use those as inspiration to develop the architecture of my computer myself.

Besides 555 CMOS timers, some EEPROMs and HM62256 SRAM everything else is supposed to be built discretely with 74 series ICs.

I planned it to have a 16 bit word length, but didn't think about the implications this would have for the RAM as opposed to all the 8 bit computer examples I've read about.

My first approach was to make the RAM word-addressable, so I hooked up the address lines of two HM62256s and effectively had 16 bits stored in every address. This would be easy to output to the bus and work with, so I developed an instruction set around it, with a 5 bit opcode and the remaining 11 bits depending on the type of the instruction left for registers or immediate values.

While doing more and more research however I realized that word-addressable RAM doesn't seem to be common in real world computers. They all seem to be addressable by byte. This wouldn't be a problem for 8-bit computers, but if I plan on fetching my instructions in just one cycle doing it this way would be a problem.

Especially looking at ASCII it seems important to have a way to store single bytes in RAM, not just whole words. If I were to store ASCII characters in 2-byte RAM addresses, there'd be 50% wasted storage. I could just ignore this and carry on with my plans, but I'm also really intrigued by how this is solved.

How am I able to fetch multiple bytes from a byte-addressable RAM simultaneously to use them in my instruction register? Would I have to read two bytes in sequence and re-assemble them into a single 16-bit instruction before storing it in the register? What about other kind of data, does reading a 2-byte value require me to load two bytes from RAM manually into registers and re-assemble them?
Is there a more useful (or simpler) way I just can't think of?

Sorry for the long read for that short question, but thanks for any replies.


texts:
Can anyone explain why do we have that negative voltage VEE?
I know that it's a DC voltage, from its name, but I can't find the explanation for why is it negative. Also, Vi1 and Vi2, from that symbol I know they are DC but shouldn't we have AC as well?


texts: What external power supply should I use for Arduino modules?

texts:
I build a data logger with Arduino MEGA, SD, Ethernet, RTC, GSM, display module, and thermal printer. I am facing problem with unregulated power supplies. I have tried many power adapters, phone chargers, led strip power supplies and noone is 5±0.2V regulated. All power supplies are over 5V and are drifting overtime. I tried led power supply with buck converter 5V and the output was 5.4V. The only good power supply was ATX PSU but it is waste of money.

I need a 5V 2.5-3A regulated power supply, how can I find or build one?

Note: The device is going to work continuously over 5 years


texts: How to eliminate the forbidden state in an SR latch?

texts:
I'd like a latch where the output only changes when both inputs have changed.  If only one input has changed, the latch output should stay constant.

Here's the state table I want:

S R | Qnext
----+------
0 0 |   Q
0 1 |   0
1 0 |   1
1 1 |   Q

The above looks just like a standard SR latch, except that the (1, 1) forbidden state is replaced with a hold state.

How can I design the above latch?  I could add some logic to convert the (1, 1) inputs to (0, 0) (e.g., S' = S(~R), R' = R(~S)), but I'm worried about glitches.

Background/motivation:

I have a double pole single throw (DPST) switch (one normally open, one normally closed).  I assumed that when the switch is toggled, the pole that is closing would bounce while the pole that is opening would not.  If this assumption had been correct, I would have been able to debounce the switch with the above latch.

If my assumption had been correct, then the main challenge would have been the fact that the two poles are racy:  pole #1 might change before or after pole #2 changes.  This would mean that during a transition the poles could be in any state:  (0,0), (0,1), (1,0), or (1,1).  But, there would be a property I could rely on:  Once the switch went from (0,1) to (1,0) (or vice-versa), it wouldn't bounce back.  This property would have allowed the above latch to debounce the switch.


texts: RF Antenna design for 2 different operating frequencies

texts:
I have noticed that my mobile phone sometimes shows it is using the 3G and then other times the 4G.

How is that possible if they are using the same antenna?

I assume it would use a microcontroller to switch the path going to the antenna to have the correct impedance (50 ohm). Or perhaps a Balun that can manage the different frequencies?

3G - 1.8 GHz

4G - 2.6 GHz


texts:
I am trying to connect my apartment door bell system to my raspberry pi; I am not too good with the wiring, and hope someone can help.

What I have:

3 wires from the door bell system: red wire, black wire, white wire.
1 digital multimeter
1 AC/DC to DC Power Supply Converter Step Down

The AC/DC to DC Power Supply has the following specs listed:

Input: DC 0V ~ 30V or AC 0V ~ 20V
Output: DC 1.25V ~ 28V (continuously adjustable)
Output current: 2A Max.

What I am trying to do: connect the wires from door bell system to the power supply, then output a 3.3v DC logic input to the raspberry pi.

What I need: the transformer needs a ground and a live wire, I need to find out from that three colored wires from the apt door bell system

what's my problem: my multimeter showed me some frustrated digits, I'm out of clues to define the correct wires, and here I am...

My multimeter result with the button not pushed:

black and red: 10v AC;
white and red: 12v AC;
black and white: 1.5v AC;

If I press the door bell button outside

black and red = 0v AC;
white and red = 12v AC;
white and black = 0v AC;

So how do I connect wires to the power supply?


texts: Excessively high temperature reading with LM35

texts:
I am really new to electronics and I am just experimenting at the moment with a breadboard.

My question here is related to the LM35 temperature sensor and Arduino micro controller. I am getting a very high reading through the sensor of 448 degrees Celsius. Obviously this is way off. The conversion formula I am using is:

inputvoltage = (5.0*inputvoltage*100.0)/1024.0;

I am feeding 5V into the sensor from the Arduino and I am getting a 0.50 voltage reading on my multimeter between 5V in and output. Do you think the sensor might be faulty? Any help on this issue would be great!

EDIT: Some people have asked for my code from the arduino so here it is:

int tempPin = 0;

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

void loop() {
  float temp = (5.0 * analogRead(tempPin) * 100.0) / 1024;
  Serial.print(temp,1);
  Serial.println(" degrees C   ");
  delay(1000);
  }

 This schematic shows the really simple configuration I have.

I have added a picture of my setup if anybody can spot something I can't.


texts: Selection of ferrite bead for analog and digital supply isolation

texts:
In many circuits I see the analog supply and the digital supply separated by a ferrite bead.
I am aware that it is done because the devices that are connected to the digital supply create noise and hence the ferrite bead blocks the noise entering into the analog part which is noise sensitive.
How do we calculate the value of the ferrite bead and what are the considerations involved? Instead what if we connect 0hm resistor thereby connecting the analog and digital supply over a single point such that the amount of noise entering the analog side is considerably less?


texts: Why is CMOS fall time faster than rise time?

texts: I've just started a computer architecture class, and the slides from a lecture says that the reason why fall time is faster than rise time is that the NMOS electrons have more mobility than PMOS which has holes. Does anyone know how to explain this in simple terms?


texts:
So I have been researching about protecting a MOSFET. I have used MOSFETs for basic on/off switches but never really thought about fully protecting them. I have used them for on/off switches to engage relay coils. The only thing I did was place a fly back diode across the the inductive load.

Then I came across Self Protected MOSFETs. Here is a link to a diagram:
https://www.google.com/search?q=self+protected+mosfet&espv=2&biw=1920&bih=955&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiY7M3j0MrKAhVIVT4KHWQvD_kQ_AUIBigB#imgrc=uUMrOVnQMAn6oM%3A

I am only really interested in the ESD and Over Voltage protection sections to implement in my own designs. If I were to make a robust design to drive, say, a DC motor, here are my thoughts:

Protect The Gate:
I would place a series resistor of about 100 ohms to prevent too much charge the gate layer to puncture.

Ensure MOSFET Turns Off:
I would place a 100k ohm resistor between the gate and source (assuming source is tied to circuit ground or battery negative) to ensure the MOSFETs gate capacitor like behavior discharges so that if the input floats, the MOSFET turns off.

Vgs Protection:
I would place a TVS diode before the 100 ohm resistor so I could catch transients. Whether it is uni or bi directional I think depends on the gates tolerance for these voltages. I am going to assume that Vgs should only be positive and thus use a unidirectional TVS. And pick it so that the clamping voltage is not beyond the absolute maximum of Vgs for the MOSFET. Reverse voltage should clamp right away.

>>>Vds Protection:<<<
This is where my confusion arises. Do I need this? Most MOSFETs have a body diode and should protect from voltages due to inductors being switched off quickly. I don't like taking risks so I would use a faster diode or maybe even a TVS across drain and source and place a flyback diode on the inductor. But in the diagram I linked to, the TVS is across drain and gate. Why?

If I assume a large voltage builds up on the drain, the TVS would conduct (before max Vds I assume of the transistor), go through the gate resistor, and go to both the postive rail driving the gate and through the 100k ohm bleed resistor to ground? But doesn't this also turn on the MOSFET? This is where things get murky and despite researching the answer on the internet, I couldn't find a clear answer.

Update:
Here is a circuit diagram of what is in my head per request from user.


texts: How to calculate air gap in flyback transformer?

texts:
I’m designing (or at least trying) flyback converter on LM3478. I choose EFD20/10/7-3F3 core [1]. Using pdf from Infineon [2] I calculated that I need inductance of primary winding about 56µH and turn ratio of 1:22.125. I have problem with air gap: I know that I need one, but I have no clue how much gap I need. How to calculate it?

Input: 12-24V
Output: 265V 5mA
fosc: 500kHz

[1] https://ferroxcube.home.pl/prod/assets/efd20.pdf
[2] https://www.mouser.com/pdfdocs/2-8.pdf


texts:
I'm trying to teach myself electronics from an old textbook, "Fundamentals of Electric Circuits", \$4\$th Edition, by Alexander and Sadiku.  On page \$41\$, I can't figure out how they did example \$2.6.\$  See this diagram:

So I'm applying KVL around the loop.  I get:$$-12 + 4i + 2v_0  - 4 - 6i = 0$$

But the book says it's \${+6i}\$.  The current is flowing to the negative pole of the resistor, so it should be negative, right?  Is the book wrong, or am I misunderstanding something?

Edit:

The book text for the problem reads:

  Determine \$v_0\$ and \$i\$ in the circuit.
  Solution:
  We apply KVL around the loop as shown in the figure.  The result is:\$-12 + 4i + 2v_0  - 4 + 6i = 0\$

  Applying Ohm's Law to the 6 Ohm resistor gives:
  \$v_0  = -6i\$

  Substituting the previous equation into the first one yields: \$i = -8 A\$ and \$v_0 = 48 V\$

The way the book described to do this was to follow the current, and the sign of each voltage element is determined by the polarity.  So \$-12 V, 4i\$, and so on.  But continuing that pattern, we get to the \$-\$ pole of the \$6\$ Ohms resister before we get to the positive pole, so \$v_0\$ equals \$-6i V\$.

I'm not understanding something.


texts: Why do N-channel MOSFETs have a voltage drop when load is connected on source side?

texts:
I read how MOSFETs work, although there is this thing I can't understand. To make things simpler let's take only n-channel MOSFETs into account. Normally, the load is connected on the drain side, like this:

When \$V_{GS}\$ is above \$V_{thres}\$ and high enough for the desired current to conduct, the MOSFET is in full saturation, and the effective resistance is low, making the \$V_{DS}\$ very small. This happens even if \$V_{DS}\$ is higher or lower than \$V_{GS}\$.

However, if you connect the load on the source side, like this:

In order for the MOSFET to go into full saturation, it's required that \$V_{GS} > V_{DS} + V_{thres}\$. Why is that? The load is still in the same current path; does it somehow lower the effective voltage at the drain (in the first case) so that \$V_{DS} < V_{GS}\$ before current flows?


texts:
Will spinning a small DC motor work effectively as a rotational speed sensor (by producing voltage)?

I'm trying to measure the rotation of a shaft (driven by a trackball) on a shoestring budget. I came up with the idea of using a small DC motor I have on hand to generate a rotational speed based voltage. I came across information on resolvers, however I don't particularly care about the position of the shaft, just the speed and direction.

I'm planning on placing diodes on each terminal of the DC motor to direct the output to 2 different input pins on an ADC (depending on spin direction) and connect the correct terminal to ground.

Depending on the output voltage, I'll also plan on either putting in place a voltage divider or do some zenier diode clipping to prevent voltage spikes.

Is there anything I'm overlooking? It all sounds correct in theory to me, but damnit Jim, I'm a programmer, not an electrical engineer!

I'd rather not fry a microcontroller.


texts: How I can test the power supply across the load?

texts: I want to test my power supply at the 12 V 10 A specification. I had tried with connect a 100-watt 0.7-ohm load resistor across it, but by that time the voltage went down to 3 to 4 volt. How does it happen? And how can I test this power supply?


texts: Analog mixer design help choosing between 2 states

texts:
I have designed 2 types of mixer an additive and a substractive one:
The additive one is a practical application of Millman's theorem connected to an opamp:

simulate this circuit – Schematic created using CircuitLab
And the substractive is a voltage substractor:

simulate this circuit
I want to have a mechanical switch which will choose which type i will use every time.How to do that?
I want to drive loads of feedback(which will go to the input of the transistor).
I am recently interested in circuits with feedback and I run this circuit on LTSpice:

simulate this circuit
that is why I am asking this.


texts: Suitable NMOS with 3.3V gate voltage to switch 12V 500mA

texts:
I've got a circuit board with a D2PAK NMOS pad that I need to find a mosfet that will work with a raspberry pi's 3.3V GPIO. This is the current one I'm using and it isn't working well. https://www.digikey.ca/product-detail/en/infineon-technologies/IRLZ34NSTRLPBF/IRLZ34NSTRLPBFCT-ND/2441092

Trying to find one on digikey with a drive voltage of 2.5V is almost impossible (unless I'm doing something wrong)


texts:
I am trying to trigger an scr/thyristor from a 0-5V TTL pulse (channel 1 on the oscilloscope output).  The schematic can be viewed below.  I am using the TTL to pull the 2n2222 transistor 'on' which than triggers the p-chan. mosfet allowing current to flow to the gate of the scr.  Both the mosfet and transistor are biased by a floating 5 volts power supply from the 'wall'.  To test that the scr is open, I have added another floating 16 volt power supply with resistor to measure a voltage drop across.  The problem is that when I have the two grounds of the power supply's isolated I get ringing and wild oscillations (seen in figure 1).  When the two grounds are reference to each other (seen in figure 2) the output of the scr than goes from low to high, and I would expect the voltage to go high to low.

Note that the channels 1,2,3 correspond to the measurement points 1,2,3 in the schematic and ground#1,2 refer to the different grounds of the power supplys.  Any advice would be awesome thanks!

simulate this circuit – Schematic created using CircuitLab


texts:
First of all I am most definitely not an expert but I still wanted to try repairing my Razer Kraken headset and cut of the cable to re-solder them onto the small "regulator pcb" (because one had been torn off) (it's that little thing that has a toggle-mute button and a wheel to adjust the volume). When opening the casing of said thing I saw that there where 4 small wires inside the cable going from the pcb to the plug but 6 going from the pcb to the headset. I then opened up the headset and found that two of them were labeled SPR, one was labeled MIC- and a fourth one MIC. The remaining two weren't labeled. My Question is: Why are there these 2 extra cables? Or if SPR is speaker right then why are there two cables for speaker right?
[One answer I came up with is that these are the ground for the respective Speaker and that in the small pcb these are all combined into one - is this correct?]

SOLUTION: The answer provided below solves my question however there was still another problem I had to solve: there were not only 4 but 5 connections going from the pcb to the plug (2 of them being ground). BUT the one for the mic was actually "hidden inside" the ground cable [one of the ground connections was weapped around the mic cable which made it look like one bigger copper wire]


texts:
This is part of an iPhone 7 schematic. The VDD line is the main voltage rail for the phone.

I noticed this AC coupling tied to the LCM (display ground) I'm not familiar with MIPI but assume it has to do with connecting an external monitor to view display on the iPhone.

My understanding is that AC coupling caps is to allow ac to pass but block DC so, how would there be any AC on the main VDD line for implanting AC coupling caps? And what's the purpose?


texts:
I have the circuit shown in the image. According to the the book I am reading when the opamp is in common mode Vout is always 0.

That means that also the gain is 0 because G=Vout/Vin.

Is this happening cause the circuit is completely symmetric?


texts: Are mechanical relay signal pins isolated from the output?

texts:
I am going to use a magnetic mechanical relay to switch 240v AC.

I am using MPC250D6Z05APT, in its specification it did not say that the 5V signal is isolated from its output upon failure of the product.

My question is by nature of mechanical relays are the signal pins/ coil pins isolated from its output terminal?

If not, how would you create a protection circuit, without having external power supplies?

Here is what I though up with using traditional opto isolator, but I am not confident since the 5V supply is still coming from the same board.


texts: 3-phase Brushless Motor - Are Volts and Amps at (X)RPM equal/similar when used as Generator?

texts:
If I have a Brushless 3-phase motor that spins at 3000rpm when given 6.0A @ 20v (no load) will it produce 6.0A and 20v (or anywhere close) when used as a generator and spun at 3000rpm??

And i suppose this comes into it too... Will a 3-phase bridge rectifier make DC more or less as efficiently as an ESC turns DC into a 3-phase signal??

....UPDATE:  So this is the motor I am thinking of using now:

MOTOR: 5065
KV: 270
MAX POWER: 2200W
WIRE WINDS: 9
MAX AMP: 60A
ESC: 80/120A
MAX VOLT: 8S
RESISTANCE (Ohm): .42
NO LOAD CURRENT: 1,5
SIZE: 50 x 65 ( without shaft )
WEIGHT (g): 0,380
SHAFT: 8mm with 3mm keyway

I will use a pulley to spin it at 18000rpm hopefully resulting in about 60v..

Does anyone know what current I can expect?

And being a 2200w motor (more than the engine that is powering it (700w)) ,when i connect it to the mppt charge controller will the engine struggle to turn as the load creates effort? Or can I expect that it will be creating far fewer amps than it draws when used as a motor at this voltage and under load?...


texts: Reading an optocoupler datasheet and calculating the resistors for its input/output

texts:
This is a continuation from this question (sort of)

I want to replace the relays from an existing circuit with optocouplers and had trouble how to read the optocoupler datasheets as well as understanding how they operate. I think I understand a little now, but still consider myself quite newbish in the topic.

I changed the optocoupler from the previous question, since I've found that it's probably easier to start with a more widespread component (4N25 or 4N27).

If I understand opto-couplers a bit better I might switch to a more fitting opto-coupler for my appliance.

So, to start, here is the schematic with relays:

simulate this circuit – Schematic created using CircuitLab

Since optocouplers consist of LEDs an input protection resistor is necessary. Also there's a voltage drop from the transistor on the output.

For the Input Module the schematic is almost identical, since the voltage drop of the transistor is neglect-able on the module side.
But for the Output Module I have trouble finding the right resistor so that the Passive (\$ I_{passive} = 10mA \$) / Active state (\$ I_{active} = 20-30mA \$) for the monitored output are still correct.

The output module has an internal resistor of 26K7 ohm and a MOSFET bypassing that resistor when active.

Here are my schematics with optocouplers:

simulate this circuit

I also don't really know how to calculate the resistor for the LED.

It seems to me like the output module can't be used with optocouplers, as the passive state is enough to activate the led / saturate the transistor.

Reading the datasheet, there's this figure, which tells me the 4N25 would become active from the passive state of the output module.

EDIT:

R2 on the output module is mandatory because it's a monitored output.

When the output is inactive, the internal 26K7 ohm resistors will limit the current to around 10mA (in series with 800 ohm).
This 10mA basically tells the circuit that there's no wire-break.

Now, when the output is active, the internal resistor gets bypassed. With the bypass all I have is the 800 ohms, which needs a parallel resistor to limit the current on the LED.

But that's where I fail, since I don't know how to size R3 properly.

I feel like I'm getting this wrong.


texts: How does one display part names in the board layout view of Eagle?

texts:
How does one show the part name for a part in the board layout of EAGLE?
In the attached picture I would like to see E2 next to the LED named E2. There are quite a few LEDs on this board and this would be very helpful in laying the board out correctly. This is different from displaying pin names.

Thank you for you help =)


texts: How the low inductance of short ground clip probes prevents interference?

texts:
Below are photos of two scope probes with different ground clip lengths:

I have read that the shorter ground is used to minimize the inductance of the probe ground lead.

But what does that help for? What happens when the inductance of the ground lead is low? What kind of interference it prevents?


texts: How to increase number of micro-controller inputs?

texts:
I have relatively little experience with electronics, but do have a basic understanding. I am attempting to build a measuring device, which will measure 100 points in 0.1 seconds. These will all produce a digital number which will need to be stored on a micro controller.

If I were to use the raspberry pi model b, it only has 17 input GPIO pins. My question is that is there a relatively simple way of taking more inputs than the micro controller has pins?

Currently the way I am looking at doing it is having an output which sends a number to choose which input to read, that sensor would then send its current value back to the micro controller. The disadvantage of this method is obviously that it takes up time. I want 100 inputs in the order of 10^-3 seconds and I assume that this has to be a fairly common feature of circuit design given most systems have a large numbers of sensors.

So, is there an easy way of doing it? Is the way I have detailed above at all sensible? Is this a common problem, if so how is it normally overcome?


texts: Why am I losing the signal when I attach this RF amp circuit and how can I correct it?

texts:
I am trying to follow this circuit diagram:

Taken from (http://www.techlib.com/electronics/crystal.html)

Using two oscilloscopes I am watching the signal on the tuner circuit and the voltage created by the amplifier. First, before connecting the RF amp circuit, I adjust the tuner to ensure I am getting a good signal, then when I connect the positive terminal from the capacitor to the tuner circuit, the amplified signal does not appear to be modulating--I'm pretty sure it's not the proper signal.

My configuration is very slightly different:

simulate this circuit – Schematic created using CircuitLab

I suspect that the RF amp circuit is affecting my tuning, but I don't know why and I don't know how to fix or compensate for this.


texts: TPS61090 used for 5V from LiPo, not turning on with USB input

texts:
I inherited a circuit design with MCP78371 (U1) and TPS61090 (U2).
When USB is applied, U1 outputs V-USB to U2 for boost to 5V (to power a very small motor (180mA) and LED backlight (90mA) on a LCD display), and it charges a LiPo battery (Vlipo).
When USB is not present, U1 accepts Vlipo and passes it to U2 for boosting to 5V.
U1 output (V-USB or Vlipo) also powers a fixed 3.3V regulator to power an ESP32-WROOM-32D.
U2 has a 5V Enable line that is controlled by the ESP32.
I am seeing odd behavior when USB power is used. When U2 Vbat is 5V and the U2 enable line goes to 3.3V from the ESP32, the output won't turn on. I see no switching activity at all with a 'scope.
When U2 Vbat is 4V from the Lipo and enable goes to 3.3V, the output turns on and 5V is created just fine.
What am I missing? Is the enable line just too low when 5V is used?


texts: How can I integrate microphone and speaker into my microcontroller project?

texts:
Having never worked with mic and speakers in the past, I am experimenting with these. I already made a simple circuit with a mic (electret condenser microphone) and speaker. I used the above mic with simple amplifier stage and then computer speaker. It works well.

Now, I am thinking of building a simple microphone, speaker and microcontroller circuit. The idea is basically to feed in the input from mic to microcontroller and then output the audio signal to the speaker.

For that I think I need to first convert the analog signal from the mic to digital values using AVR's ADC.  After that I need to output the analog values to the speaker. Since this is my first time, I need advice on how to build a working circuit. What should be the sampling and playback rate? Do I have to worry about codecs, etc? (I don't know how large raw audio data can be.)

I am planning on using Arduino first since it's easy and quick for prototyping.

Any help is appreciated as always! :)


texts:
I'm experimenting with PIC microcontrollers and various related circuits both on plugboards and simple homemade PCBS.

I'd like to use various old AC power adaptors I have lying around to power my circuits instead of relying on batteries all the time. I have several old mobile phone chargers for example that give out 5v with 500-1000mA of available power.  ( I realise they are likely unregulated and I'd need a regulator circuit or similar).

My worry is that that they are very cheaply made so what happens if I accidentally short circuit one or try to draw 1000mA from a 500mA supply.

Are they likely protected against such abuse in any way even if only by an internal fuse? Or are they likely to be severely damaged or worse overheat and catch fire or something? Or will they simply deliver their maximum current and continue working?

None of this is likely to happen, but I want to be safe?

I doubt this affects the answer but this is the UK with a 240v mains supply.


texts: How to interpret the S21 phase measured by LCA or VNA?

texts: I have measured the S21 phase of my device, which came as below. I would like to know if this phase is with reference to the input or with reference to the DC?


texts: Difference: Low Pass Filter and Large Capacitor?

texts:
When working with microcontrollers it is recommended to place filter/decoupling capacitors between a supply pin and ground. I understand the purpose of this implementation, namely that voltage across a capacitor cannot instantaneously change, but what are the outstanding differences between a singular capacitor and a low-pass filter?

These are not calculated values; I inserted this just as an illustration.

simulate this circuit – Schematic created using CircuitLab

For example, if I were wanting to provide my ADC reference voltage a clean supply to compare input voltages against, I could either realize a low-pass filter to reject the high-frequency fluctuations or simply insert a adequately sized capacitor.

My immediate thought is that the initial current demand of a singular capacitor could momentarily exceed the maximum rating of the MCU, but with a resistor this current would be limited. Would it not be that with a LPF (with a resistor) that one could potentially design such that the output impedance of the filter is infinite as to not load the ADC? Similarly, a capacitor alone would provide sufficient voltage filtering but would it not result in a low output impedance?

What are the pros and cons of each realization of filtering, and when should a designer use one or the other?

Any other thoughts ?


texts: what is the frequency required to have all harmonics which have more than 10% DC value when we have 250 MHz clock?

texts:
A Digital board has a Unipolar square clock of 250 MHz. If the clock on the board at all places should have all the harmonic components which have more than 10% of DC value, the board has to be designed of atleast-

A)250 MHz
B)750 MHz
C)1250 MHz
D)2500 MHz

The answer given is 1250 MHz.
Can you explain how to solve this problem?


texts: Why don't electrons take the shorter path in coils?

texts:
Below is a copper coil, presumably forming an electromagnet. From my understanding the electrons travel around the coil to produce a magnetic field. But why don't the electrons jump the wires and take the shortest path?

Below I tried to draw the path that would make sense (for me) for the electrons to take:


texts:
What diode modifiers are used in practice to model LEDs with SPICE (Berkeley v.3f5)? These are available to me:

#       Name    Parameter                    Units      Default Example  Area
1       IS      Saturation current             A         1e-14   1e-14    *
2       RS      Ohmic resistance               Ω         0       10       *
3       N       Emission coefficient           -         1       1.0
4       TT      Transit-time                   s         0       0.1ns
5       CJO     Zero-bias junction capacitance F         0       2pF      *
6       VJ      Junction potential             V         1       0.6
7       M       Grading coefficient            -         0.5     0.5
8       EG      Activation energy              eV        1.11    1.11 Si
                                                                 0.69 Sbd
                                                                 0.67 Ge
9       XTI     Saturation-current temperature exponent  3.0     3.0 jn
                                                                 2.0 Sbd
10      KF      Flicker noise coefficient      -         0
11    AF      Flicker noise exponent         -         1
12    FC      Coeff. for for.-bias dep. cap. formula   0.5
13    BV      Reverse breakdown voltage      V         ∞       40.0
14    IBV     Current at breakdown voltage   A         1.0e-3
15    TNOM    Parameter measurement temp.    °C        27      50

  3.4.2 Diode Model (D)
  The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. The nominal temperature at which these parameters were measured is TNOM, which defaults to the circuit-wide value specified on the .OPTIONS control line. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers).

For example, using this basic, cheap red:

I don't care much about high-frequency characteristics -- just would like to be able to match it's IV-curve within its operating specs (-10uA/-5V leakage to +100mA/+2.2'ishV forward):


texts: Does an ATX PSU's PS_ON Signal Require Resistance

texts:
As the title suggests; when connecting the PS_On signal directly to ground in order to switch on an ATX PSU, is there a required amount of resistance?

-

To try to clarify my particular problem; I have a fully modular ATX PSU (a Seasonic Platinum Series) but am not using it to connect a motherboard, so have no need of the bulky motherboard cable. I decided to order a custom-made cable compatible with the modular connectors on the PSU itself, with a wire connecting PS_On to ground (via a 2-pin header so I can connect a suitable switch or LED if I want). However, when I connect the pin directly, although the PSU switches on, it almost immediately switches off again.

The PSU is not at fault, as connecting the regular motherboard cable using the paper-clip trick works just fine and the PSU starts providing power normally. The only difference I can see between the working and non-working cables is that the non-working cable uses much shorter wires and of a finer gauge (AWG22 at about 5-6cm as opposed to AWG18 at around 60cm). So I'm wondering; is my cable failing to work because of a lack of resistance?

If so, I'd appreciate anyone that can also clarify how I would work out what type of resistor I would need to add to correctly complete the circuit.


texts:
In Eagle CAD software (ver. 5.12), how do I get the file name of the User Language Program (ULP) from inside this program (programmatically)?

I only know how to get the name of the schematic, board or library. For example, to get the board name:

board(B) printf(B.name);


texts: Why are the dimensions of a floating gate layer in a MOSFET so thick?

texts:
For a floating gate MOSFET, in order to make the control gate work you have to(generally speaking) make the oxide layer thin(~100 Angstroms) as well as the ONO(Oxygen nitride, acts as an insulator) layer(~200 Angstroms). However, making it too thin causes electric leakage. What I want to know is, why does it seem like none of these limitations apply to the floating gate layer?
In a lot of schematics for FG-MOSFETS, the floating gate layer is always much bigger (~1500 Angstroms) than the Oxide and ONO layers. But making the FG thick only puts the control gate farther away, so it seems like it doesn't really matter how thick you make the FG, the same amount of charge passes through anyway, why is this? I know that you don't need a large threshold voltage since a charged floating gate interference between the CG and the semiconductor will increase the voltage differential in a cell that's been programmed. I'm guessing that it has something to do with conductivity, but I don't know enough about electrical engineering to be sure.

Sorry for the confusing post, but electronics isn't my major, so I don't know if I have all the terms correctly. Any help would be greatly appreciated.


texts: Designing a DC 12V 80A Power Distribution PCB panel and heat sinking

texts:
Background

I'm trying to build a small hobby grade ROV for an underwater robotics competition held at the university I'm studying. And I have used eight brushed dc motors each of which consumes 8A on full load.

The whole system might consume about 75-80A at maximum usage. But we are pretty sure that we are not running all motors at the same time at full load and hence average current usage would be around 50-65A.

I have included eight 12V 8Ah SLA batteries inside our ROV and hope it might run for like one and a half hour at most on average.

Problem

One of the issues I'm having right now is with designing a PCB layout where wires from eight batteries are merged onto the PCB Board.

Please note that I'm not an electronics/electrical engineering student that I do not have proper and solid knowledge on power circuits and calculating thermal dissipation.

I just don't want to be a dumbass letting the PCB burns into smoke and flame from overheating. I am afraid that might happen when the amount of current stated above have to be passed through the plate.

I have space limitation and maximum dimension of the PCB for the distribution panel should not exceed 6"x6" dimension.

Above is the overview of the power supply and distribution concept for the ROV. After the summation of total current usage and wattage, to a shocking moment, it's around 1kW and 80A of DC 12V. Is it such a high usage of power in sense of power circuits? I never had an experience with circuits that use over 12V 35A. I'm afraid that I might be wasting a lot of power. But my ROV is a bit big in size, about 3'x2'x1.5' dimension of steel structure. But I'm pretty sure we are going to operate only four motors at the same instance and at 70% of full load at max. So I guess 50A is maximum for normal operation conditions.

My Questions

How should I design my PCB for power distribution purpose only?
Shall I use a typical thick PCB or a copper block with heat sink?
Is the total overall power usage huge and not suitable?
Your advice on making things better.


texts: Identify this 2-pin component - markings include AUPO A4-F

texts:
This part went bad, I have no idea what it is to order it on Mueller site, can you identify it for me?

Thanks to anyone that does.

.


texts: designing a "quite universal" half bridge?

texts:
A lot of power stuff run on H-bridges controlled by a MCU, would it be possible to design a half bridge and its integrated driver that would work on a very wide range of tension, like 10V to 250V on the power side, 3.3V or 5V on the logic side, probably with integrated dead-time? And creating various ones for various max current (where we can oversize without problem).

I was thinking about only a half bridge so that the user assembles them depending on the situation (biploar motor up to BLDCs to strange steppers). And it would be some kind of lego for power, but with the messy problem of the driver already taken care of. For home fiddling it would be really good, you'd only have the current rating to take care of (and probably thermal dissipation) and you can just over-rate it. Dead-time integration would probably be good to simplify the fiddling too.


texts:
When using NodeMCU, I want to toggle the state of GPIO pin, using a physical switch. When the switch is pressed, the switch state should toggle from low to high, or high to low.

I know I need to use interrupts here, however I am unable to find relevant information online. I need help with circuit to implement a switch for GPIO interrupt. What would be ideal resistor value etc.

I forgot to mention, i am using Tasmota firmware on NodeMCU.

Thanks.


texts: Problem in understanding bridge rectifier

texts:
In a bridge rectifier (full wave) why do the electrons not flow from the other two diodes during a half cycle?
Pls help me in understanding the concept.


texts: Gettting hand movements registered and sent to an arduino

texts: I want to control a servo motor attached to an arduino through hand movements. I am just beginning the project and my idea is to attach a couple of accelorometers to each finger and then send that data to the arduino through Xbee . Firstly is this the right approach to doing this , or are there ready made sensors which I can wrap around my hand and send data to the arduino. Secondly I am stumped as to how to attach a Xbee sender to each accelerometer on my hand. Is this how its generally done? Does kinect even use accelerometers. Or is it some other kind of sensor. What would be the right approach to this project?


texts:
I have a DS1307 RTC chip that I want to interface with multiple masters.
One, an ATMega chip, will only ever really need to pull time data from the chip and the other (probably just an ATTiny) will be there solely for the purpose of receiving wireless time updates and updating the time on the RTC. I realize that I could just build in this wireless update functionality to the ATMega chip, but I'm trying to work on a modular RTC board that, as far as the ATMega is concerned, is exactly the same as any other similar RTC like the DS1307 or the DS3231 (Chronodot).

Question is, can I just wire it all to the same two i2c bus lines and communicate with the RTC from BOTH chips? If so, do I need to do anything to ensure that both are not trying at the same time? I assume that, since i2c already supports multiple slave devices that this should generally be handled for me. But, in general, should this work. I'm ok with the ATMega trying to get the time and having to wait if the RTC is being updated. Which would be rare anyways, maybe every hour at most.

Thoughts?


texts: Altera MAX10 CPLD initialization IO state

texts:
I'm designing a pcb with an Altera MAX10 (10M02) CPLD used to do, amongst other things, bus arbitration between several memory chips (one /CS per chip).
All the memory chip are on same bus so only one /CS (and /OE) shall be toggled low at same time to avoid bus conflict.

To my understanding, the MAX10 CPLD can initialize itself within 2ms at power on (based on uncompressed, un-encrypted binary, numbers I found in a datasheet).

I wanted to know what is the state of the I/O when CPLD is initializing. Are they HighZ? Low? High? Or is the state unpredictable? Some more notes:

I use verilog "assign" to set all the critical I/O's to 1 by default (assuming registers are 0 after initialisation). Eg: "assign outputname= registername?1'b0 : 1'b1;"
I've set all the I/O's to 3.3LVCMOS because everything is interfaced with 3.3V devices.
The rise/fall timing requires to be less than 10ns.

Also, can someone confirm the MAX10 (10M02) CPLD has all registers cleared after initialisation? (I don't use any reset pin). I can't find any details about that on the datasheets.

Thanks for your answer / suggestions.

Best Regards,


texts: Operating Point Parameters for Stacked Transistor

texts:
I've just recently started working with FinFETs for the first time. One of the Pcells included in the PDK is a stackSeries device. This allows you to choose one of the transistors in the PDK and then choose the number to place in series, the minimum being 2 devices. This appears to be done as the maximum length of any single device is quite limited so by stacking the devices you can achieve what is essentially a single transistor with your desired length.
The following diagram shows a single device being expanded into its stacked equivalent. I only show 3 transistors in the stack but this could be whatever really. Also typically the length for FinFETs is somewhat discretised, in that only certain lengths are allowed, but this shouldn't matter for this question.

So now comes my question, given a stacked device, such as the one in the image above, how might we go about finding the operating point parameters for the top level transistor? (Apologies if the wording is confusing here...!) For example, I would like to see if my transistor is in saturation or not. However the simulator will only report the threshold voltage and Vdsat for each individual transistor in the stack, not the overall device.
Is there a straightforward way to use the operating point parameters of the individual transistors in the stack to inform you of the operating point parameters of the overall equivalent transistor?
Some thoughts about this:

A quick method that would work for checking saturation could be to just check V_GS > Vth and V_GD < Vth, however which value of Vth would you use? Each individual transistor in the stack has a slightly different threshold voltage. This is also really just a hand calculation and it would be nicer to use a more accurate metric, such as Vdsat for the transistor.
There appears to be a built in method for finding operating point parameters for a stacked transistor within Cadence Virtuoso however the values it's returning me seem to be rubbish. I've posted on the Cadence forums to follow up on that.

I hope that's clear, let me know if you'd like anymore detail.


texts: d-q-frame-currents. What and where are they in PMSM?

texts:
I am doing a course in power electronics. We discuss a lot about Iq and Id, when we are talking about a three phase system and electric motors.
I like to visualize things to make them more understandable.

Question: Regarding PMSM (Permanent-Magnetic Synchronous Machine):
What is the Iq/Id-current? where is it in the machine?


texts: What is the pad-etching process in standard CMOS fabrication process

texts:
What is the pad etching process?
Is it possible to etch to the bottom metal layers or vias in standard CMOS fabrication?


texts: How will the ceiling fan behave if I put unequal turns on different slots of same coil?

texts:
Recently I opened a ceiling fan in my home trying to understand its basic operating principle.While i was through it a few questions popped up in my mind, which are as follows:-

1.What will happen if we give different no of turns in different slots of the Running coil?

On what factors we decide the no of turns of running and starting coil?

As far as my speculation tells me giving different turns would create poles of different magnetic strengths that would lead to its abnormal behavior.But i dont have a clear idea of how things will proceed in such a scenerio.

Any suggestions would be much helpful.


texts: How to get 5 volts from Lightning pinout?

texts: How to make the Lightning port of iPhone output 5V power?


texts:
I have a circuit to generate simple sound with astable multivibrator and enable/disable it with j-k flip flop with reset pin, something like this pic:

i have a problem with logic 0, when it occurs the output is 10mv instead of 0, this 10mv send to my amp and occurred noisy voice.
how can i fix it?


texts:
Ok, so I am constructing a DIY guitar pedal and I have a couple of modifications that I'm planning on adding (LED, Bass Cut/Treble Cut, etc.) But are there any mods I can make to this circuit to make it more overdriven?

Here's my circuit:

Thanks for any help that you can offer!


texts: I have just created a whole load of new component definition and saved under USERDVC in a library. Where is this located so I can back it up?


texts:
I have 4 common-anode RGB LEDs in a 4x3 matrix. I have a BSS138 on each of the red, green and blue cathode lines and a BSS84 on each of the anode pins. The power supply is 3.3v, which is close enough to Vf for each LED (red is slightly lower, and there is a 5Ω series resistor just before the red MOSFET drain to compensate).

When the matrix is not being driven at all, all the LEDs are dark. When I perform rastering, I get ghosting. The ghosting is quite low, so I could probably live with it, but I'd like to know what's causing it.

The gates are driven by a microcontroller and the gate waveforms are clean and square. When I look at the drains of the MOSFETs, their on-state is correct (either 0v for the cathode lines or 3.3v for the anodes), but the off-state voltage of the anode MOSFETs is like a downward ramp - like discharging a capacitor.

If I add a ~50k or so pull-down resistor to the anode MOSFET drain the problem goes away and the on-state drain waveform becomes square, like you'd expect.

The rastering duty cycle is 25% - that is, I actually have a huge dead-band between each anode activation period. The raster rate is one period every 125 microseconds. So the full raster is 16 periods - LED 1, then 3 off, LED 2, then 3 off etc (they're very bright LEDs).

Is a pull-down on the drain something to be expected to be necessary in this situation?

EDIT: Complete schematic is at https://hackaday.io/project/166766-Симон in the Files section.


texts:
I want to add mounting holes to a PCB. The PCB is not of my design so I can't change it. There appears to be a large ground plane in the locations that are good candidates for drilling the holes.

Is it okay to drill the holes through the ground plane?

Once drilled, the holes will be fitted with metal screws and standoffs.
The circuit on the PCB does not operate at high frequencies. The PCB has two layers.


texts: How does DC transmission require several times less wire than AC?

texts:
In this YouTube video (scrolled to 5:55) there's a claim that replacing an AC high voltage transmission line with a high voltage DC transmission line allows for having seven times fewer powerlines (the video shows how seven lines evaporate, then one line appears and the cutting in the forest gets narrower).

How is that possible? I've read the Wikipedia article and it claims that

  The power delivered in an AC system is defined by the root mean square (RMS) of an AC voltage, but RMS is only about 71% of the peak voltage. The peak voltage of AC determines the actual insulation thickness and conductor spacing.

but that doesn't explain seven times less power lines.

How is such massive (seven times) saving possible when switching from AC to DC transmission?


texts: I'm organising some components to get back into making (mostly blinking LEDs) exciting electronics, the usual BC547 etc are easy to google but I can't see anything on this .. What does it do?


texts: is it safe to drive 8 ws2812b's from an arduino's 5v pin

texts:
I am doing some light testing with a small 8 pixel ws2812b strip. I'm wondering if there is any risk of damaging the arduino (nano) by driving the 8 pixels directly off the 5v pin (rather than an external power source). I'm using this pin to simplify the test environment. Eventually more pixels would be driven by a USB battery bank (which would also power the arduino).

Using my DMM, I'm only seeing about 90 mA draw for the 8 pixels. I think that should be fine, but I'm still new to this device and don't want to do something dumb that would burn it out needlessly.

Everything else is as per the recommended layout


texts: Calculating power absorbed by time varying unit step souce in pspice

texts: I am new to Pspice and I am encountering a problem. I want to find the power absorbed at  specific given time lets say t = 0.1s using pspice. I have the following circuit with a time varying source. I think I have to use a IPULSE source but I am still unsure of the parameters to use and how to find power directly. The circuit is given below


texts: What size/shape window for a WiFi board inside a metal box?

texts:
I'm building a temperature controller comprising a WiFi transceiver, AVR, and two relays, switching 240V (single phase -- I'm in Australia).

Because I'll have mains power in the box I want to use an earthed metal enclosure, but my 2.4GHz wifi board, a seeedstudio Wifi Bee has an on-board antenna made from a PCB trace.

I intend to cut a window in the metal enclosure and cover it with plastic.

How large does it need to be, and where should I put it in relation to the WiFi Bee's antenna trace?


texts: What does it mean when a charger has 5V 0.7A?

texts:
For my phone (Samsung Galaxy Note 2) I have several chargers. I noticed that with some of them it takes much longer to charge the phone, to the point that a whole night is not enough to charge it. So I did some measuring.

Lab power supply   421 mA   4.8 V
Charger 1           92 mA   4.7 V
Charger 2          152 mA   4.7 V
Charger 3          421 mA   4.8 V

From these figures I guess the phone needs at least 4.7 V to charge and it regulates the current intake accordingly.

All three chargers look identical and are marked  (click for full view).

Do I have faulty chargers or does 5.0V 0.7A actually mean "can output 700 mA with whatever voltage drop is necessary"?


texts:
how can i read a negative voltage by the mcp3008 ?
, i tried to do that with this code but i I could not read
it , i see that the most readings are 0.00 ,
this is my code :
import RPi.GPIO as GPIO
import pigpio
import time
import spidev

GPIO.setwarnings(False)

spi = spidev.SpiDev()
spi.open(0,0)
pi=pigpio.pi()
if not pi.connected:
exit()

def analogInput(channel):
 spi.max_speed_hz =  1442      #f_cpu/frequency 1442
 adc=spi.xfer2([1,(8+channel)<<4,0])
 data = ((adc[1]&3)<<8) + adc[2]
 return data

def Volts(data):
 volts=(data*3.3)/float(1023)      #1024
 volts=round(volts,2)
 return volts

dc=718000
pi.hardware_PWM(18, 70000, dc)
while True:
    out=analogInput(0)
    out1=Volts(out)
    print(out1)
    time.sleep(3)


texts:
I am finding an answer  to below electronic puzzle.

I simulated  both circuits with Ltspice and find  that circuit "a" peak input current from the supply is double  than that  of circuit "b".

What  could possibly  be the reason  ?

And which option is better to be used ?

Thanks in advance.


texts:
How do I bias M4 and M3 properly? Currently, I am not able to drive them into saturation with the diode-connected structure.
I am not able to drive the Cascode PMOS into saturation. Also, can (M3, M4, M9, M10) be biased with a single biasing circuit?


texts: How to transmit analog signals over cable?

texts:
In my current project, I need to transmit 4 analog signals (A1, A2, A3 and A4) on a cable from one PCB to another. I am working at 3 VDC and the distance between them is relatively short (< 30 cm).

I am not comfortable with this situation since I have always worked within my PCB. I have read that the transmission needs to be differential, so I will transmit 9 wires : A1-, A1+, A2-, A2+, A3-, A3+, A4-, A4+ and GROUND.

What should be my configuration to make it work ? Or more precisely : what type of component should I use to transmit and receive the data on both ends ? Are there standard references ? Will the differential signals be digital or analog during the transmission ?

I may ask basic questions but I am a beginner at this, sorry...

Any help/advice will be greatly appreciated. :)

EDIT :

My PCB will need to pass the EMC certification, which is why I need to be careful with signals I am transmitting.
The analog signals are related to this ECG sensor : https://datasheets.maximintegrated.com/en/ds/MAX30001.pdf . It needs to inject and receive current on two pins and measure the voltage on two other pins.
The frequency of the current injected can reach 131 kHz based on the datasheet
I need to be as accurate as possible, which is why I need to transmit the analog signal as differentials


texts: How to add identical pad names to a package

texts:
In a schematic you can you use the @ notation to specify multiple pins with identical names for example GND@2. This doesn't seem to work in a package/board. For example an arduino board PCB has several identical pin names such as TXO or RXI.
This is how it's shown in the datasheet as well as printed on the pcb so using incrementing numbers for all pins would be confusing. Even worse there are pins on 3 sides of the pcb and even a few miss aligned pins next to rows of pins adding to the confusion.

What is the proper way to name identical pads or a good way work around this issue?

Example board:


texts: is my schematic correct? (Optocoupler with triac)

texts:
I designed a pcb that contains an optocoupler and a triac to work as a dimmer for AC

But when I give a high value to the GPIO corresponding the triac doesnt fire

So I am looking for the mistake I did ...

Is my schematic wrong ??

if its correct , what could be the problem on the pcb leading to this problem ??

How can I check it ??

I want to search for the problem but I dont know where to look


texts: Voltage dropping capacitor and small voltage transformer

texts: I want to make a mains voltage sensor for a power meter project. Since space is an issue, I looked for an alternative to a full size mains transformer. Is possible to use a voltage dropping capacitor to lower the mains voltage to about 12v and then feed it in a 1:1 small transformer for separation ?


texts: Solar panel with broken glass produces designated Voc but far less Isc Amperage

texts: I have quite several 72 cells solar panels with cracked glass taking punch during the handling. The designated Voc is a little over 45V and almost all of the cracked solar panels (20pcs) generates Voc above 44V. However the Isc measured are all over the places from 2A to 6A. The designated Isc is about 9A. I measured around 9am and the sun generates over 1000W/m**2. I guess the low Isc is directly related to the damage the panel received. However I don't quite understand why Isc is much lower while there is almost no loss with Voc. Is there something I didn't do right or missing with measurement?