texts: How does a momentary dpdt switch function?

texts: Ok I'm feeling dumb right now. I got one of these momentary dpdt switches and can see via ohm meter that the middle terminals are normally connected to one of their corresponding edge terminals when the switch is "NOT pushed." However, when I push the switch, I see the connection broken on the terminal that was previously connected, but I also expect the middle terminals to be connected to the "other" set of edge terminals. However, I don't see continuity. IOW, I expect the dpdt functionality explained in this article, albeit a toggle dpdt. I want to hook this up as a "normally off" switch rather than a "normally on" switch. I do need a dpdt since I need it to control two circuits. I have used TWO different ohm meters just to make sure. What gives?


texts:
i´m still running into connecting problems with the "4x CREE XP-E2 M2/M3 on 23mm star PCB".

https://www.led-tech.de/en/4x-CREE-XP-E2-M2-M3-on-23mm-star-PCB

Can someone help me out how do i need to connect this pcb to run all four leds?
Just connect it to the power source with a resistor (on -) on the + / - labels on the pcb wont work. if i connect the power source directly on the left and right side of the led i got it light up. but just one led at a time...

thanks a lot :)

Edit: There is a picture of the pcb.

My testing power source is small 18650 3100mAh 3,7V battery.
i know that to get 100% out of the leds i need about 12V
The resistor is a 1,2 Ohm 3 Watt.


texts: Effect of high impedance Opamp buffer on current lost

texts:
In the below figure, end-user have the choice to output 4-20mA or 0-10V (using MUX control by uC), I have inserted high impedance buffer(The part number is not correct) with the voltage divider to reduce 0-10v output to 0-5V so ADC can read it (can also reduce to 0-1V) and calibrate 0-10V.

I want to know if the user select 4-20mA as output,  the buffer will be ignored due to high impedance, is that correct. If not do I lose any current.

simulate this circuit – Schematic created using CircuitLab


texts: How many transistors is a transistor connected to in a CPU?

texts:
On average, how many transistors is a transistor connected to in a CPU?

What is the average fan-out of a gate in a CPU?

What is the average fan-in of a gate in a CPU?

(I'm guessing these numbers are much less than the average of 7,000 connections between one average neuron and other neurons in the human brain mentioned in the
Contemporary transistors
question).

In the Apollo Guidance Computer and the Cray 1, every gate has the same maximum fan-in: max fan-in of 3 in the AGC, max fan-in of 5 in the Cray 1.
What is the maximum fan-in of any gate in today's CPUs?


texts: How to do capacitance measurement with high frequency oscillator

texts: There are many types of capacitance sensors. I recently come across moisture sensors which measure the dielectric constants of the materials and correlate them to the water content level. It turns out many commercial soil moisture sensors (such as VH400 and SM100) use 80 MHz oscillators, much higher than other lower frequency methods such as those using Timer 555, or simple RC charging/discharging. I am just wondering if anyone knows how to do the high frequency version in an economic way. VH400 sells $30~$40 per piece. All those sensors output a DC voltage proportional to moisture level.


texts:
I try to derive FOC for a 2-phase motor, but I'm struggling with the right formulas and I can't find any paper explaining it. The phases of the motor are 90° apart, such that I assume the Clark Transformation is not necessary:

$$
I_{alpha} = Ia
$$
$$
I_{beta} = Ib
$$

I'm not sure if this really is true, but the currents are 90° appart, as needed for the Park Transformation, which is only applying the rotation matrix with theta, the electrical angle:

$$
Iq = cos(\theta)  I_{alpha} + sin(\theta) I_{beta}
$$
$$
Id = cos(\theta) I_{beta} - sin(\theta) I_{alpha}
$$

Now I use the standart double PI controller as for 3-Phase FOC and the inverse Park Transformation, such that I get Valpha and Vbeta, which I can apply to SVM.

$$
V_q = (I_{qdes}-I_q) K_p + SumErrQ
$$
$$
V_d = -I_d K_p + SummErrD
$$

So I implemented everything, but it works not as needed. I can control a 2-phase motor this way, but Id becomes large for one direction, so something seems to be missed here? Is anyone experience with 2-phase FOC?

Edit: Ok, I think that this should works as I implemented, but for larger Reference Currents Iq, Id becomes an offest in average different from 0, also when no higher velocities are reached. Is it possible, that this is due to flux saturation? I think high pole-pair motors (50-100 pp) are pretty sensitive to flux saturation, right? Is there a way to overcome this?


texts: UART serial communication between STM32 MCUs

texts:
Good day everyone I am new to the group.  I would like to ask for your hints regarding the UART communication between 2 STM32 MCUs.
Basically I have 2 STM32 MCUs connected through UART.  A button on MCU1 will trigger an output on MCU2 and vice versa.  Initially I tried a single button from MCU1 which drives a single output in MCU2 and this is OK.  However when I added another button2 to MCU1 I could no longer transmit data from Button2 to MCU2.
Here's my code for the Transmit MCU1:
USART2 -> CR1 |= USART_CR1_UE;
USART2 -> CR1 |= USART_CR1_TE;
USART2 -> CR1 |= USART_CR1_RE;
USART2 -> CR1 |= USART_CR1_RXNEIE;
USART2 -> CR1 |= USART_CR1_TXEIE;
NVIC_EnableIRQ(USART2_IRQn);
.
.
.

void USART2_IRQHandler(void)
{
  HAL_UART_IRQHandler(&huart2);

//this is the first transmit code for button1 which is successfully transmitted to MCU2

if(USART2 -> SR & USART_SR_TXE)
{
    {
        if(!HAL_GPIO_ReadPin(BUTTON1_GPIO_Port, BUTTON1_Pin))
        {
                      //transmit this data to MCU2
                      USART2 -> DR = 0xFF;
        }
        else
        {
              //transmit this data to MCU2
                     USART2 -> DR = 0x00;
        }
    }
}

//this is the second transmit code for button2 but this never gets transmitted to MCU2

if(USART2 -> SR & USART_SR_TXE)
{
    {
        if(HAL_GPIO_ReadPin(BUTTON2_GPIO_Port, BUTTON2_Pin))
        {
             //transmit this data to MCU2
                       USART2 -> DR = 0xF0;
        }
        else
        {
             //transmit this data to MCU2
                       USART2 -> DR = 0x0F;
        }
    }
}

//this is the first receive code from MCU2 and successfully transmitted to MCU1

if(USART2 -> SR & USART_SR_RXNE)
{
    {
        if(USART2 -> DR == 0xE3)
        {
            //enable output

                        HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_SET);
        }
        else if(USART2 -> DR == 0x1C)
        {
            //disable output

                       HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_RESET);
        }
    }
}

//this is the second receive code from MCU2 but unsuccessfully transmitted to MCU1

if(USART2 -> SR & USART_SR_RXNE)
{
    {
        if(USART2->DR == 0xCC)
        {
            HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, GPIO_PIN_SET);
        }
        else if(USART2->DR == 0x33)
        {
            HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, GPIO_PIN_RESET);
        }
    }
}

}


texts: What are the dangers of emulating a battery with a step-up transformer and a 5v power supply?

texts:
I take long timelapses, for astrophotography. My camera's batteries are irritatingly short-lifed for this purpose, and so I wanted to try an alternative. I found .stl files for 3d printing the form factor of the battery as an empty shell, and I'm pondering popping something like this inside:
https://www.amazon.co.uk/Converter-Step-up-Regulator-Stabilizer-Adjustable/dp/B071H9NRTW/ref=psdc_430514031_t2_B07MY3NZ18
This would let me connect any micro-usb power supply and step-up the voltage to the 7.4 volts the battery itself ought to supply.
Now, I'm not so hot on electronics beyond basic circuitry, so the dangers of this approach are lost on me. Obviously I'll test that it's not going to melt the printed battery case and I'll check that the output voltage is stable before giving this a try. What I want to know is; are there any non-obvious dangers to this approach? For instance, if a certain component fries on that board, is there a danger that the camera this is plugged into will be killed? (input voltage will be 5v so that seems unlikely, but I just don't know for sure).


texts: How to derive an equation for the delay time to LED shutoff?

texts:
The question asks to create an equation for the time delay for the LED to turn off in terms of capacitance(CT), reverse current (IL) of the 1N4148 and the threshold voltage (Vt) of the MOSFET for the circuit below.

The hint given was that we can treat the 1N4148 as a current source with a value of 2 nA.

From the experiment that I performed, Threshold voltage = 1.824 V, Capacitance = 0.01uF, resistance = 600Ω, yield the LED turn off after 8.71 seconds.

I feel like I would use the capacitor equation, i=C dv/dt,
solving for dt, and plug in the values above. Is this a step in the right direction to solve this question.


texts:
I have a DC voltage source (between 5 and 10V) from which I want to charge cell phone with a USB cable. I believe that using a LM317 or similar IC for charging cell phones is not a good idea as most cell phones are coming with Lithium-ion batteries, which requires constant current phase first, then constant voltage phase.
   I have seen MAX1555 IC but it gives only 4.2 V as regulated output. If I connect a VBUS (usb cable) from MAX155 chip to iPhone, my iPhone may not charge because it's less than 5 V.

Can anyone give some insight?


texts: Why we use #pragma configs in PIC controllers?

texts:
Hi all I am new to the programming of PIC MCUs and I have with me PIC32 MCU. I have done a UART program in it and its working fine. I got the code for UART from Microchips website and its easily understandable. But I am confused with #pragma configs, I mean why this config bits are used. I did a little bit of google searching and found that all the #pragma configs can be found in c\program files\microchip\mplabc32\doc but I really don't know why we use it. Now lets say if I have to do a I2C communication then how would I know that which #pragma configs I need to include? I didn't find a good explanation for it on google. Can any PIC experts explain about it. Thanks.

#pragma config FNOSC = PRIPLL       //Primary Osc w/PLL (XT+,HS+,EC+PLL)
#pragma config POSCMOD = HS         //HS osc mode
#pragma config FPLLMUL = MUL_18     //PLL Multiplier 18x Multiplier
#pragma config FPLLIDIV = DIV_2     //PLL Input Divider 2x Divider
#pragma config FPBDIV = DIV_1       //Peripheral Clock Divisor: Pb_Clk is Sys_Clk/2
#pragma config FPLLODIV = DIV_1     //System PLL Output Clock Divider: PLL Divide by 1


texts: How does 'Interrupt on Change' work on a PIC 16f877A controller?

texts:
I have a problem with my program. I am using "interrupt on change" on a 16f877A microcontroller. I use MikroC.
What the program should do:
The program should generate an interrupt when I press a button on port B4: B7 and set all the pins of port A to one while keeping the button pressed, if the button is released, port A turns off.
What the program does:
By pressing the button the pins of port A are activated, however they do not turn off when I release the button.
The code that is inside  while loop works correctly, the problem appears during the interruption.
This is my code:
unsigned char count;

void interrupt () {
  if (INTCON.RBIF) {
    count++;
    PORTA = ~PORTA;
    if (portb);
    INTCON.RBIF=0;
  }
}

void main() {
  cont = 0;
  TRISB = 0xFF;
  PORTB = 0;
  PORTA = 0;
  TRISA = 0;
  TRISC = 0;
  PORTC = 0;
  INTCON = 0b10001000;

  while(1) {
    PORTC= ~PORTC;
    delay_ms(200);
  }
}

Thanks :D
New code Edited*********
I have removed some of the wrong parts of the code. I rewrote it. Now pressing the button turns on PORT A; but I still don't understand why it doesn't turn off when I stop pressing the button.
unsigned char count, x;

void interrupt () {
  if (INTCON.RBIF) {
    count++;
    PORTA =~ PORTA;
    x = PORTB;
    INTCON.RBIF = 0;
  }
}

void main() {
  count = 0;
  TRISB = 0xFF;
  TRISA = 0;
  PORTA = 0;
  TRISC = 0;
  PORTC = 0;
  INTCON = 0b10001000;

  while(1) {
    PORTC = ~ PORTC;
    delay_ms(200);
  }
}
```


texts: How can the same voltage and resistance produce a different amount of current?

texts: I'm following along with Ben Eater's digital electronics playlist on YouTube. In this video, he demonstrates two circuits each with the same voltage and resistance but with one circuit the LED is emitting more light. This is explained because each circuit provides a different amount of current. I understand that less current means the LED is not as bright, however as I = V / R, I don't understand how the current can be different if the voltage and resistance is the same.


texts: Massive ultracapacitor banks, why don't they work? (400V 3.38F)

texts:
This might be a stupid question, and I know that for high energy, quick discharge applications (like a railgun for example) supercapacitors don't really work, but why?

If I were to take hundreds of ultracapacitors (let's say they are 2.7V 500F individually), and then hook them up in series to get a 400V 3.378F capacitor bank, shouldn't that work better than a 400V 63300µF aluminum electrolytic capacitor bank?


texts: In a photo diode in which region light should be focused to fall?

texts:
In this question correct answer given is option \$(D)\$ that means in a photo diode light should be focused to fall in whole P and N region including the deplection region
but when I googled this site says

  This diode is generally operated in reverse bias condition. The light when focused on the depletion region, electron-hole pairs are formed and flow of electron occurs.

So here its says it should be focused only in deplection region.

What is correct ?

apart from this question I want to know the region why it is necessary to do that to point in the particular region?


texts:
Am a very beginner with electronic circuits and its components.. Im trying to turn on my water pump using Arudino nano. Ive got 25A solid state relay for that purpose. So according to little info I collected from google, I found we have to connect a diode to relay coil to avoid return current from the coil which will spoils the circuitary. but my questions are

how can we decide the diode to connect in this case. I mean any
specific values?
Also does the diode to connect to the positive terminal of the coil
in series with the out from Arduino? Or is it parallel?

This is the specification of the relay

If its not solid state relay what could be the solution


texts: Help Identifying Inductor From a Schematic

texts: I’m repairing a laptop but I don’t know what value inductor to use/get. The schematic has values, I just don’t know how to interpret other than it’s a 2mm inductor. It’s labeled 5A_Z120_25M_0805_2P on a 1.35V line.


texts: Controlling the speed of a brushless motor with the HA13535

texts:
I am using an HA13535 three phase brushless motor driver as described in this datasheet: http://www.datasheetarchive.com/dl/Scans-052/DSAIH00045920.pdf
The datasheet says the circuit features digital speed control, but I can't figure out how to control the speed at all. I currently have it setup for its soft-switching mode. I don't have experience with brushless motors and was hoping someone could point out what I am missing.


texts:
I have a Brookstone rover 1.0. In the app, you can trigger an IR LED to go on. I have also installed lights in the front and back of the rover in a simple LED series driven by a resistor connected directly to the battery.

I was thinking it would be possible to use discrete components such as a few transistors to trigger the LEDs to go on when the IR is off. The IR LED is connected to GND (this much I know), and when the microprocessor sets the pin to high the led goes on as the circuit is completed (this I am assuming). I have no way of accessing the code, and changing the procedures.

Is there a way to trigger a transistor as a switch so to speak to make the LEDs go on, when the IR is off (i.e. when there is no (+) going to the IR) and vice-versa?


texts: Determine saturation base current from NPN transistor datasheet (or what resistor do I need to ensure saturation?)

texts:
The Fairchild 2N3904 has a long data sheet so let's use that for this exercise.  I'm interested in using an NPN in common emitter configuration --- it's for switching.  It's my understanding that an NPN transistor is in saturation when collector-emitter voltage is equal to \$V_{CE(sat)}\$, which is about 0.25 V here.  Say our load is simply a resistor, so I understand how to calculate \$I_{C(sat)}\$.  My question is, how do I thence compute \$I_{B(sat)}\$?  Do I just use the DC current gain (\$h_{FE}\$)?

Let's suppose for example that my \$I_{C(sat)}\$ = 90 mA.  According to the data sheet would a conservative estimate for gain be \$h_{FE}\$ = 30?  I say conservative because I want to choose a resistor \$R_B\$ such that my TTL signal is sure to drive the transistor into saturation.  That is, my TTL signal will generate \$I_{B(sat)}\$.


texts: Optimising LED output without destroying them, factors, temperature

texts:
I want to maximise output of LEDs. The problem is I don't have the datasheets, only absolute maximum ratings. But even when operating below those ratings, I keep blowing them.

How should I determine best operating current? Trial and error? I'm considering running 10 or more overnight at a given current to if any blow. If this is the best way, then what other factors should I take into account? I suspect temperature is important - please can someone shed light on the relationships temperature has on LED operation?

I presume higher temperature decreases the forward voltage required to achieve a given current? For a given forward current, does the temperature affect lifespan? (Within reasonable temperatures e.g. -10 to 60 degrees c)

Thanks


texts:
I have a fixed DC voltage - say within the range of 12-24V. I'm looking to take this voltage supply and run it through some sort of circuitry so that I can have a USB-C female port say on a desk or wall port capable of charging various devices such as phones laptops etc.
I am familiar with the fact that USB-C protocol can utilize communication protocol to select the appropriate power to deliver to a specific device. I have seen the reverse of what I'm looking for in various videos in that power is taken from a power source via USB-C before its converted to a DC source depending on the power delivery capabilities of the source.
Is there an existing board capable of doing this? I understand that perhaps the circuitry would need to communicate first with the device connected first at a 5V level, before being capable of stepping up power delivery to match that of the connected device. So this may require some logic / stepping-down of power?
Some research lead the TPS65982 chip by Texas Instruments - but I'm not sure if this is what I'm looking for. Any suggestion/advice greatly appreciated.


texts:
I am getting data from compass( hmC5883L)  and trying to detect angle.

Well, i dont really care about offsets, i just want to check that if its flat on the table and i make a 90 degrees round, i will get numbers x-> 90+x

Instead for 90 degrees turn i get values like that :
(starting from 13 degrees)

13->180, jump right to 0, 0->180, 180->13

code to manipulate data :

                float gScale = .92;  // Scale factor for +1.3Ga setting

                float adjx = x - xOffset; //set to 0 for testing
                float adjy = y - yOffset;//set to 0 for testing

                xs = adjx * gScale;
                ys = adjy * gScale;
                zs = z * gScale;

                float heading = atan2(ys, xs);
                heading += declination / 1000; // Declination for geo area

                   if (heading < 0);
                     heading += 2*PI;

                   if (heading > 2*PI)
                     heading -= 2*PI;

                  float angle = heading * 180/M_PI;

What am i doing wrong ?


texts:
I'm trying to find power dissipation of my mosfet when I pull 17.5A. I'm using CSD18542ktt. Can anyone help me what equations can i use.

I have calculated the max power using the following equation.

P = (Tj(max) - Ta)/ RQja = 2.42Watts

Is this what i can dissipate without heat sinks?

So in my application, gate voltage is 10V and Rds(on) = 3.5mohms.

Power = 17.5 * 17.5 * 0.0035 = 1.07watts.

In order to check if i need a heatsink, i will multiply 1.07 with RQja. That gives me 66.34 which is way below my maximum junction temperature. Does that mean i do not need a heatsink?


texts: Understanding USB Differential and Single Ended Impedance Requirements

texts:
The USB IF spec mentions the following for USB 3.0:

This has me scratching my head. In my experience, \$Z_{diff} < 2 Z_0\$ -- typically around 1.6-1.8. So how is it possible to meet both the single and double ended requirements if the single ended requirement needs to be around 50\$\Omega\$ (readily achievable) to get the 90\$\Omega\$ differential impedance?

Some of the resources I've found even explicitly say 50\$\Omega\$, such as this Toradex high speed layout guide (PDF):

And this TI USB 3.0 hub reference design, which uses ~4.5mil trace, 5 mil space on 1oz cu, 3.7mil dielectric thickness also does 50/90:

...but this is straight from the horse's mouth.

Most information I find seems to emphasize the 90\$\Omega\$ requirement more than the 45 ohm requirement. Is it really important to get 45\$\Omega\$ or is 50\$\Omega\$ preferred? Can someone set the record straight for me?


texts: What type of DC-DC converter should I use for solar MPPT?

texts: I am currently doing a project that involves Maximum Power Point Tracking (MPPT) for Solar Panels. I plan to do this by using the Arduino as a controller to a DC-DC converter. I am going to use the perturb and observe algorithm in tracking the maximum power point of the solar panel. Now I am thinking of what converter topology to use: buck, boost, buck-boost, etc. What do you suggest I use?


texts: Is it possible to clean lots of dirty test pins reliably? We have about 6000 of these test pins and most of them are very dirty. If I cleaned them, what kind of lubricant should I use to relube them? Thanks.


texts: Very limited number of built-in components for simulation in Altium

texts:
I have very little experience with PCB CAD programs. I once used KiCAD for a simple circuit. Couple of days ago I tried OrCAD's free lite version PCB editor, but it was crashing a lot. So to compare I decided to try Altium for trial period and try it. I like LTspice but I also want a professional PCB program which can also simulate well before PCB routing. So I wanted to check out OrCad and Altium.

After playing a bit with Altium I noticed that it has a built in library which is called "Miscellaneous Devices.IntLib". In this library, as BJT models only 2N3904, 2N3904 and a generic one exists. Similarly only one MOSFET model. And for example if I want to use LM324 it doesn't exist. If you choose opamp it will be AD645A.

There is a window when you double click for a component as below:

It seems to me one has to find the SIM model for a component which is not in default library each time and modify it.

In OrCAD on the other hand I could see a huge built-in components library. If I look for lets say BC547B it is there or LM324 it is there or any voltage regulator...

Am I doing something wrong or is Altium's component library really very very limited and we have to do the work for each component? If so this is horrible for such an expensive software, I don't understand why it is too limited. Does anybody have experience with using Altium as simulation software and experience the same problem?


texts: Floating input in Op-amp Readout Circuit?

texts:
I was analyzing this circuit diagram in a thesis about a capacitive EEG electrode. The author talks about a flaw in the design where there is a "floating analogue input" that is causing the op-amp to go to rail and consequently maxing out the output. She suggests adding a very high value resistor or even a Zener diode from the input to ground. I'm assuming that she means the non-inverting input of the gain amplifier. I think however that the cause of the floating input might be from trace input bias currents saturating the amp, but then the best solution would be to have the resistor to ground be equal to R10 and R11 in parallel in order to minimize offset voltage. Would the 100 ohm resistor between the buffer and gain amplifiers have any influence?

Should the resistor between the non-inverting input and ground be equal to the feedback resistors in parallel or have as high a resistance as possible?

The readout circuit consists of a buffer and gain amplifier.


texts: Multiple LED outputs on FPGA using Verilog

texts:
I made a simple 0 to 9 up counter using Verilog. The output is 4 LEDs which are turned on when their corresponding bit is 1. The code synthesizes fine, but on the FPGA, only one LED lights on and off repeatedly. The other three LEDs do not light up at all.
Here is my code:

module counter(
   input wire clock,
   input wire reset,

   output wire [3:0] o_number
);

reg [3:0] cur_state;
reg [3:0] next_state;

always @(posedge clock or posedge reset) begin
   if (reset) cur_state <= 4'b0;
   else
    cur_state <= next_state;
end

// Next state function
always @(*) begin
   if (cur_state == 4'b1001) next_state = 4'b0000;
   else next_state = cur_state + 4'b0001;
end

 // Output function
assign o_number = cur_state;

endmodule

module display(
   input wire [3:0] inumber,

   output wire [3:0] LEDs
);

assign LEDs = inumber;

endmodule

None of the LEDs are broken as they all light up when tested individually. Clock has been adjusted so its period is around 2 seconds.

Please help me out. Thank you.

I revised the counter module. Here are all the files I used:

top.v

module top ( input wire clock, input wire reset, output wire [3:0] LEDs);
counter c1 (.clock(clock), .reset(reset), .o_number(number));
display d1 (.inumber(number), .LEDs(LEDs));
endmodule

counter.v

module counter ( input wire clock, input wire reset, output wire [3:0] o_number);
reg [3:0] cur_state;
always @ (posedge clock or posedge reset) begin
    if (reset) cur_state[3:0] <= 4'b0000;
    else begin
        if (cur_state[3:0]==4'b1001) cur_state[3:0] <= 4'b0000;
        else cur_state[3:0] <= cur_state[3:0] + 4'b0001;
    end
end
assign o_number[3:0]=cur_state[3:0];
endmodule

display.v

module display( input wire[3:0] inumber, output wire [3:0] LEDs);
assign LEDs[3:0] = inumber[3:0];
endmodule

top.ucf

NET "LEDs[0]" LOC = K12;
NET "LEDs[1]" LOC = P14;
NET "LEDs[2]" LOC = L12;
NET "LEDs[3]" LOC = N14;

NET "clock" LOC = T9;
NET "reset" LOC = L14;


texts: What circuit performance changes may be caused by conformal coating?

texts:
I realize that, in principle, conformal coating should be inert and not affect a circuit's behavior, but are there any real-world performance changes to look out for when using conformal coating?

I have two boards that pass IRIG signals (low-speed digital, 5 V) that are nominally identical except that one is conformal coated. The coated board has sloppier IRIG edges, but I suspect this is because of variations in the performance of the ICs in the chain (an optocoupler, a transistor, and an inverter), rather than the conformal coating.

Has anyone experienced problems that they have directly tied to conformal coating?


texts: Why modern cellphones do not have an externally visible antenna?

texts:
Old phones had either a fixed antenna inside a housing which was externally visible, or a retractable antenna, which was visible when used. I'm assuming this was needed to obtain a certain total length.

In modern cellphones all the antennas are inside the case. The height dimension of older cellphones was similar to current modern cellphones (smartphones). Why now externally visible antennas are not needed?


texts: Need help understanding RC discharging through a transistor in a timer

texts:
Once I push and release a pushbutton I want a LED to light for say 10 seconds.
I found a design for this on the web and tried it out:

What I observed on the breadboard was that the LED lighted for at least 60 secs and seemed to be exponentially decaying.

I also found equations describing a discharging RC circuit:

$$V_C=V_0e^{-\frac{t}{RC}}$$
$$I=\frac{V_0}{R}e^{-\frac{t}{RC}}$$

According to these equations the capacitor should be "fully discharged" in t=5*R*C.

In my case R = 10kOhm and C=220uF => t = 5*1e4*2.2e-4 = 11 secs.

So what is wrong in this analysis?
Also since the transistor (BC 548) needs V_BE about 0.7 V or more I would think that the LED would decay exponentially until the voltage out of the capacitor dropped down to 0.7V and then the LED would instantly shut off.

How can i modify the Circuit to behave more like what i want?


texts:
How does an ultrasonic distance sensor work?

My thoughts:

A microcontroller (Arduino nano) sends a signal to an amplifier that makes it into a 40kHz pulse, which then goes to the transmitter which sends it out. After some time the receiver get the pulse, where it runs it though an op amp (because of the loss in air?) and then sends it back to the Arduino.

If this is true, how does the Arduino / microcontroller convert this information into time?


texts: I want to digitize (convert from analog to digital) a signal that can vary from -300 volts to +300 volts. Can anybody suggest how to handle this high voltage signal?


texts: ADC resolution and effective number of bits

texts:
As I understand it, if I have a 3-bit ADC with 2-bits effective resolution, and a full scale range of 7V, this means that instead of my LSB being 1V (7V / 2^3 - 1 = 1), my LSB is actually 2.33V (7V / 2^2 - 1 = 2.33).

Is that correct?

The ADC can still output any 3 bit value though can't it? So does this mean that if my input is 1V, instead of constantly getting an ADC output of 001 which I would expect for an ideal 3-bit ADC, I would instead get varying output that averages out over time to 2.3333V?


texts: why capacitance depends upon frequency physically irrespective of mathematical fact?

texts: Sir,I know that when f=0 capacitive reactance will be infinity according to mathematical formula and thats why capacitor blocks dc.But what is its physical significance?I mean why capacitor blocks dc when frequency is null?I really dont get its answer to clearly understand it.Thank you.


texts:
I had worked previously on a project which used a L298N motor driver to control motors.Datasheet Link.

I have now completed my project and started with the production phase of it. But while I was successful in dispatching the first lot perfectly fine, the second lot is giving a lot of issues. And the issues are:

When I am giving 0 and 5 V to turn my motors in one direction, instead of giving +Vcc and ground voltage, it is giving me +Vcc and 3 V. I am getting really confused about why 3 V is coming when it should have been 0 V. And this is not only with one driver, but many of the drivers are also doing the same. And if I change Drivers by desoldering and again soldering, I sometimes work, or either I have to again replace the driver until I get the correct output. I am doubtful If my circuit is wrong because my first lot have been dispatched without issues.

Can the lot of my L289N be wrong? I am attaching my circuit too below: At sense pin is a connected a 470 mohm resistor to ground.

Also attaching the internals on L298n from datasheet


texts: Phototransistor with digital potentiometer

texts:
As per the circuit diagram below, I'm trying to use a phototransistor with a digital potentiometer so that the sensitivity can be adjusted. PH_TR connects to an analog pin on a SAMD21 chip.

Is there any reason why this won't work. I'm not entirely sure how the digital potentiometer works. Will having W connected to GND as well as the low part of the resistor cause any problems?

What I'm trying to achieve is a resistance that can be adjusted between 0\$\Omega\$ and 10k\$\Omega\$.

TPL0401 Datasheet (digital potentiometer)

TEPT5700 Datasheet (phototransistor)


texts: MOSFET reliability for critical applications

texts: I am working on a critical circuit that drives a DC motor in an aircraft landing gear system. The electric motor is a simple DC motor where one polarity extends the landing gear and reversing the polarity retracts it. My question is are there any reasons why using MOSFETs instead of mechanical relays would present a reliability issue? Obviously it is important that the gear comes down when it is commanded to so making sure this is reliable is high priority.


texts: What is the difference between BRAM and distributed RAM

texts: I am doing a project on BRAM implementation. What is the difference between Block RAM and Distributed RAM on FPGA in terms of implementation, area, speed etc? Which is better?


texts:
I have some trouble in understandy Space Vector PWM (SVPWM) with the zero vector. To modulate the amplitude of the vector, the zero vector (000) or (111) is applied for a certain time. This means, that the motor phases are shorted. This should lead to braking, or am I wrong? And if so, this would be very inefficient, right? What am I missing here?

Edit: Here is an example of SVPWM, where the zero vector is applied for a certain time. With a 3 phase-inverter, this means all low-side mosfets (or all high side mosfets) are conducting, which means all phases are shorted together. I understand that this zero vector needs to be applied to modulate the current amplitude, but I don't understand if this state really means braking for the motor and if so, then this should waste a lot of energy, right?

It is also good to see in the following picture, where all phases are sometimes connected together through the high or the low side:


texts: Is this RC circuit really in series? It looks parallel to me?

texts: If you read the second paragraph, it claims that the resistor and capacitor are in series, but they are both connected to same positive potential and both lead to ground, so isn't this a parallel configuration?


texts: ESC target speed tracking for brushless motors

texts:
Does anyone know if the common ESC units used for drones allow for target speed tracking as either open-loop or closed loop system? A lot of the units I have seen only let you set min/max throttle via PWM and don't allow you to actually set a target rotational velocity.
Brushless DC motors should in theory be able to have their rotational velocities controlled using an open-loop controller which varies the rate of coils energizing.


texts: Im building a Nintendo 64 to PC adapter as outlined in this guide. It calls for two 4006 ICs. RadioShack did not have this type, but I was told the following two would work: LM339 or a LM324. Will either of those suffice for the project mentioned above?


texts: Motor with two endstops using limit switches

texts:
I have a circuit where two limit-switches to be wired with motors to do the following functionality. It is to be used in a remotely placed device so that the intervention of microcontroller on the working of the motor should be minimized.

The circuit shall perform the following operation

When the supply is positive the motor should rotate CW. After reaching the limit switch, the motor is to be disconnected from the supply. Afterwards, by using a trigger (maybe reversing the supply, for example) the motor should rotate counterclockwise to reach the other limit switch. After reaching the switch, the motor should be disconnected from the supply again. By keeping the motor in this position and if we again give another trigger, the motor should rotate clockwise again.

In short, the motor should rotate to and fro. The limit switches should disconnect the motor when the knob reaches the limit switches. A trigger should be there to make the disconnected circuit live again.

The circuit is to be used in mostly damped areas place. The motor is actually closing a water connection valve. It can be easily done by using some microcontrollers. But if the microcontroller or any of the small components like we may use as switches(diode, MOSFETs etc..) fails, it may result in utter loss of water.

The motor has a maximum rating of 3.6VDC. And the supply is a 3.3V Li-ion Battery.


texts: Feeding 12V Pulse into Microcontroller 5V - Use a Transistor?

texts:
I have a 12V Tachometer Pulse Signal From an ignition unit(From the data sheet)...I would like to feed this pulse into a micro-controller to output the speed to a LCD display. I don't have a scope to put on the 12v signal, but I did put it on a multimeter and the frequency matches what I was expecting. Albeit, the signal is a bit jumpy.

What's the right way to connect this pulse into MCU? Optoisolator?

Is this a safe way to connect the 12v Pulse into the MCU? Should I use a voltage divider on the pulse?

simulate this circuit – Schematic created using CircuitLab


texts: What to look for in an isolation transformer?

texts:
What do you want from an (isolation) transformer besides it having the minimum voltage/current/power(/frequency?) specs that the to be isolated device needs? Does it matter whether the transformer is being used to perform precise measurements, to prevent for getting in contact with live circuitry or something else?

The reason why I'm asking is that for a 230V isolation transformers that can handle at least 2A current, I've seen isolation transformers starting from €60 for a bare transformers to well over €200 for units that are in some kind of enclosure and have medical grade specifications. While my primary motivation for an isolation transformer is working on power supplies it would be nice if it is not a single purpose tool.


texts: Calculating the voltage difference between a switching pin out and a constant Vout

texts:
Sorry to trouble you all with a similar question. But this is a different question altogether regarding calculation of voltage difference.
I am using NCV3063 IC.

According to my design of the boost converter in my board, I am measuring the values of pin1 and pin2 in multimeter and scope respectively. This is a reference board.

For Vin(Vcc) of 16V, The voltage at pin1(SWC) of the IC is 5.05V as measured in DMM.

Pin2 (SWE), I am measuring in scope, I am getting a peak-peak of some 15.8V with 30.6% duty and max amplitude of 13.8V.
Now, Vswce=difference between the pins 1 and 2.

How to calculate the voltage difference between (1) and(2)?

Or in general, how to calculate the voltage difference between a switching Vout pin (here, pin2) and a constant Vout pin (here, pin1).

Please help

Thanks


texts:
I recently came across this video on YouTube, in which the guy is soldering a .5 mm QFP component.

Hand soldering a .5 mm QFP Chip

As I haven't done a lot of soldering in my life (and never used flux), I have a few questions.

The guy in the video uses only flux without solder to do all of the soldering. How is this possible? What kind of flux is he using? As far as I know, flux is only used as a cleaning chemical during the soldering process. Correct me if I'm wrong.
He puts flux over the PCB traces and the space between them. If the flux is conductive, how is it possible that there are no short circuits created?


texts: Why to double reverse diodes in parallel to MOSFET?

texts:
I am building an H-bridge by this article.

In the H-bridge MOSFETs IRF9530 and IRF530 used.

By datasheet of Vishay both of MOSFETs have reverse diode inside the package.

So by proposed schematics the reverse diodes is doubled in parallel.
I understand that reverse diodes inside MOSFET package are put there to protect the transistor from inductive reverse current.

Why to double reverse diodes in parallel?

Maybe some special diode should be place in addition to MOSFET internal diode?

Maybe external diode can be ignored if the transistor packaging includes the reverse diode?


texts: How to check for the ESD protection of the capacitors

texts:
I have this circuit

I need to check whether my input capacitors C0001-c0004 are protected for ESD events.
My ESD pulse spec: +/-8kV, 2kohms & 330pF. I have taken 130% of this +8kV as my ESD pulse for the worst case calculations.
I am performing the calculations as per this Article - Capacitor as ESD Protection
So, in accordance with the above article,
My calculations are below:

According to the above calculations, my questions :

Since the required capacitance is more than the actual capacitance present in the above calculation, does this mean, I should increase the input capacitor capacitance value? Or what does it mean?

So, after the ESD event, the capacitors will help to clamp the voltage to 72.512V approx. , & it will be present at Input_P node and will damage the Q0002 transistor, since Q0002 Vce(max) is only 45V. Since, 72.512V > 45V, won't this 72.512 damage the transistor and the other downstream components and also components connected on the Input_P rail?

So, should I focus on the capacitor capacitance value for the ESD calculations or should I focus on the ESD Clamp voltage ? I am confused. Please tell me how to validate my design using the calculation.


texts:
I am carrying out some research on CCDs for a h/w design project that I have coming up that would include a 2D bar-code scanner module. I know that there are ready made modules available and thus there is no need to design one ourselves, still I would like to know a little more about barcode scanners. To that effect I have a few questions

Are the CCDs used in bar-code scanners, especially for 2D scanners, similar to those used in cameras?
If not, what is the exact difference?

A pointer to specific brands and/or manufacturers would also be nice.


texts: How to stop two DC motors simultaneously using limit switches

texts:
I need some help - I'm building a machine but I'm not sure of the best way of doing it.

Thanks a million for your help

Just to refresh my point - I've made one or two changes

I have two large wire spools. One empty and one full. The full spool (approx. 500kg) is much larger than the empty spool (100kg when full).

I wish to transfer the wire from the large spool to the smaller spools. I want to do this regularly so I want to set up a system that will not have to be monitored but can turn itself off when the smaller spool is full and/or the larger spool is almost empty - whichever happens first.

I want to keep this as simple as possible.

I'm looking to put a motor on the small spool and use this to turn the large spool through the pull of the wire

I will be using one small spool at a time along with one large spool at a time

I want the entire system to shut down once the small spool is full or the large spool is almost empty - whichever happens first

The wire in question is a high carbon wire with a very high tensile strength so this should not be a problem for the wire - I am confident hat the wire will be able to handle the pull as long as there is a slow start up and slow down

The large spool has a weight of 1100lbs (500kg), a diameter of 28 inches (70cm) and a depth of 12 inches (30cm) - in the picture attached there are two large spools stacked on top of eachother on one pallet

The small spool has a diameter of 19 inches (48cm) and a depth of 9 inches (24cm)

I want to unwind the entire contents of the large spool onto 5 smaller spools - each smaller spool will be manually lifted off and replaced with an empty spool each time the small spool is full - maximum rotational weight on the take up spool at any one time is 220lbs (100kg)

I would like to start and stop the small spool slowly - ideally a slow start/stop lasting approximately 3 to 4 seconds

I would like to turn the small spool - the one powered by a motor at between 3 to 5 revolutions per second (180 to 300 rev per minuet)

A uniform wrapping speed is not critical - I am conscious that the wrapping speed will change as the diamter of the larger spool decreases and the diameter of the smaller spool will increase. I don't need any footage count - just plain transfer from one spool to another

I do not have any motors at the moment so any suggestions would be greatly appreciated

I have access to 110 Volt, 230 Volt and 3 phase 400 Volt supply

I don't need the motors to run in reverse just in one direction

I'm hoping to get this done for as cheap as possible - at most €1500

Please give me some suggestions on how to start and stop both motors and the best type of motors for the job

Thanks very much for your help


texts: Why do you get shocked touching a live wire?

texts:
A number of times (over many years) I've accidentally touched a live AC mains wire (120V, 60Hz) while working on home wiring.  The feeling is always similar: uncomfortable tingling feeling at the point of contact (generally the tip of my finger).  In all cases, I most certainly have not had "good" contact with ground (for example, when it occurred today, I was standing on a plastic stool, with rubber soled shoes).

My question is: why do I feel a shock?

More specifically:

My resistance to ground is too high to have any non-negligible current.
My capacitance to ground seems not high enough to have a noticeable shock (see below).

I see some resources online suggesting a capacitance to ground of a few 100 pF.  If true, then (assuming 100 pF capacitance):

Z = 1/(2*Pi*f*C) =~ 26 MOhms
I = V/Z = 120V / 26 MOhms =~ 5 uA

The threshold of sensation is generally specified to be around 1mA (somewhat less at 60Hz).  So, if my body capacitance is correct, then I'd expect to feel a sensation only at voltage 100 times higher (10kV).  Of course, my body capacitance could be wrong.  Is it, or is there a different effect going on?

Question part 2: Why is the sensation only in my fingertip?


texts:
I am trying to work out what function the components in inverter colors serve, this is a schematic I have derived from a net-list to make it easier to explain my answer

E1 is an Error amplifier inside a LDO Regulator (VCVS)

Net 3 is connected to source of a P-Channel MOSFET with upper and lower clips.  (I think this is unusual as I have found that the output of error amplifier is with respect to the input)

Net 9 is the FB (Feedback) node,

Net 12is the reference voltage node,

2.8V output voltage is set using feedback resistive divider. Has dropout voltage of 220mV for 150mA. Nominal input is 3-5.5v.

Is there a name or key word for this type of compensation?

How does this help for stability, PSRR (both) e.g. If I wanted to perform open and closed loop analysis for placement of poles and zeros ? What would this change?


texts: Can I connect my laptop that runs on 18.5V directly to a 12V battery?

texts:
I have days of electricity outages here (due to war!) and I need to use my laptop. The thing is, it runs off 18.5 V 3.5 A (AC adapter output), so it is expecting 18.5 V, what will happen if I connect it to a 12 V? I know for sure some laptops will work! I tried some crappy old laptop and it ran even though the adapter its AC adapter outputs 18 V, but I did not want to try this on my laptop as I don't know what might happen.

The laptop's internal battery is dead and I have actually removed it, so should not the voltage be enough to run the laptop since now there is no battery to charge! And since the internal battery outputs 10.8V, should not the laptop be able to run on that low voltage from the power source as well?

But again I was afraid if I provide too low voltage the laptop will try to withdraw more current, and that might heat it up and fry it! But then I thought I can add a fuse to prevent the current from exceeding certain limit (say 7 A?)

And if we assume it does not work! Then I can add 2 batteries which will give me 24 V, but now I'm thinking 24 (actually almost 28V when the batteries are fully charged) might be too much for the laptop and now high voltage could really hurt!

A solution to that could be to add a linear voltage regulator, but that wastes too much energy (or does it not?), which is why I'm not using DC-AC power inverter in the first place, after all I'm trying to make this setup as efficient as possible (because as I said we have days of outages), so how do I reduce voltage without having to waste much energy?

Assuming the batteries are fully charged, thus outputting "almost" 28 V the regulator then will have to drop the volt down by 8 volts! Will this waste too much power? and by too much power here I mean like 50 watts! because the laptop runs with that much so if it will waste 50 watts or so, then it will be actually wasting the same as the actual load does! and that is a lot.

And an important question here, will I have problems with the regulator heating up? or that little difference isn't going to cause much heat?

To sum the questions up:

Can I connect my laptop that runs on "18.5 V" directly to a 12 V battery OR 24 V (2 batteries)? If I have 2 batteries outputting 24 V how do I reduce the voltage without wasting energy?


texts: 555 Timer in monostable mode with reset on the same momentary button

texts:
I've been researching this problem for a few days. I have a 555 timer for controlling a car heated windshield, and I'd like to have a single button controlling it, and use that same button to cancel mid-timer, if the user doesn't need the full duration.

I've so far come up with the following schematic, and have been testing on protoboard:

It has a 555 timer with around a 5 minute timer (doesn't need to be exact), and the output switches a mosfet configuration which turns on a relay. This relay then changes which line the switch pulls to GND from trigger to reset.

My problem is that when I have this circuit built, pushing the button causes the relay to energise, which pulls reset low before I can release the button, so the relay vibrates on and off rapidly, which gives an unpredictable output.

I think I might need to debounce the switch, but I am not sure what the best way to do this is (other than just putting a capacitor in parallel), and also I may need to delay the pull-down of the reset pin on the 555 so I don't end up with this vibrating effect, which I think is unrelated to the debouncing.

I've found this link which seems to do what I want, but I don't think the schematic they used is noticably different to the one I've designed.

Appreciate any help.


texts: how to config Nodemcu interrupt as slave in arduino IDE

texts:
I want my NodeMcu to broadcast recieved data from SPI to wifi.
I need to use interrupt of recieve and to broadcast.
In the manual bellow there is no slave SPI for Node mcu.
Is there some manual i could use to accomplish it?
Thanks
https://diyi0t.com/spi-tutorial-for-arduino-and-esp8266/


texts: MOSFET drain-source on-state resistance as a function of temperature and drain current

texts:
I have a question regarding an article/paper I have read (https://www.electronicdesign.com/power/analyze-mosfet-parameter-shifts-near-maximum-operating-temperature) and hope someone can help me here. In this article the author describes an equation for the drain-source on-state resistance of a MOSFET as a function of temperature and drain current. Unfortunately, I am  too stupid to understand a small but important step of the author. It is about the resistance coefficient a of equation 6. The author says "a is a resistance coefficient derived from the Point 1 voltage and current (Figure 2, at 25°C)", but I don't understand how exactly, he determines this coefficient. I tried some calculation, but I don't get the same results for a like the author (listed in table "SIMULATION RESULTS FOR FIVE MOSFETs" in the article/paper).

Has anyone read this article or understands the author at once?
Many thanks in advance!


texts: How can I attenuate a video signal in discrete steps using digital control?

texts:
I would like to use a μController to adjust the brightness of VGA/EGA RGB signal.
My intention is to allow for a setting from "full brightness" (0% attenuation) to "completely dark/black" (whatever % necessary, probably >80%).

I assume it means that all three channels should be adjusted in parallel to the same level, but I'm also open to them needing their own separate adjustment curves to compensate for the perceived brightness of the different colours. The attenuator/s should be controlled from a (single) μC, like a PIC or similar.

A digipot could be a possible solution, although according to this app note from Maxim (https://www.maximintegrated.com/en/app-notes/index.mvp/id/3081), there seems to be at least -3dB loss for an ordinary digipot at video frequencies. It may be incorrect, or there may be better digipots that I have not found yet.


texts:
There is a Heltec's wifi kit 32, that is based on esp32 controller with a battery attached. I want to write a script to know if the device is plugged in to a PC or a charger.

Script provided here by Heltec allows me to easily measure the voltage on the battery. The logic boils down to the following lines of code:

float XS = 0.00225;      //The returned reading is multiplied by this XS to get the battery voltage.
uint16_t MUL = 1000;
uint16_t voltage =  analogRead(37)*XS*MUL;

My original idea was to measure if the value of voltage is growing to figure out if the device is plugged in. Unfrotunately the value is constantly jumping back and forth, so it isn't very reliable.

What is a better way to understand if the device is plugged in?


texts: How Does Connecting a Battery in Series Affect Current Flow

texts:
Background:

I am creating a circuit to run electronics and motors.  The some of the electronics are 5V some are 12V and the motors are 24V.  I have a small universal 12V battery for the electronics I run it through a 5V regulator for the 5V electronics.  In addition I have a huge Optima Yellow Top 12V battery.  I want to create a 24V circuit for the motors by connecting the small 12V battery to the large optima 12V battery in series.

My Question:

How would current flow through this circuit?  In other words, do the motor take an equal amount of current from each battery?  Would the current in the wire from the positive terminal of the smaller battery to the negative terminal of the Optima battery be the same as from the optima positive terminal to the smaller battery negative terminal (the motors will be between the optima positive and the smaller battery negative).  Will the optima battery be able to supply the majority of the current?  If I hooked another 12V battery in parallel with each of the 12V batteries, how would current be drawn from that battery?

Thanks for any help,
Joel


texts:
CAN bus transceivers come in 5 V and 3.3 V, and bus voltage levels are differential, 2.5 V +/-1.25 VV.

Is there a CAN bus which can be operated at 12 V (also the differential voltage is higher)? I would like to do this in order to make the bus more robust.


texts: Common mode inductor and diode circuit (EMC filter?)

texts:
I found this Buck converter circuit online, but not so sure what's the purpose of the circuit marked in red box and how it works.
Please come in and discuss if anyone has an idea of it.
Thank you


texts:
What is "discrete diode" and when it should be used? Google doesn't help to find the answer.

What is the difference between discrete diodes and others?


texts:
Based on my study, I found that there are two different type of positioning the contact for the 3.5mm audio plug, and it is depend on the manufacturer (ex. handphone manufacturer). The difference is as follows:

Type 1: 1 is left channel, 2 for right channel, 3 for microphone, 4 for common/ground.

Type 2: 1 is left channel, 2 for right channel, 3 for common/ground, 4 for microphone.

How can I determine the type of the plug when buying the earphone? Is there any effect if I par accident buy the second type of plug connection and plug it into a device with a female jack of the first type?


texts: what filter to use for highly fluctuating data

texts:
I have the following data collected from a heart rate sensor.
The data is in bpm vs. milliseconds. All the data points below 80 is incorrect (errors/noise). When it plummets below 80, it's because the heart rate sensor fell off the subject.
Similarly, although on this graph it is not there, there are often spikes that go as high as 500. Those high peaks are caused by something physically tapping the heart rate sensor. The rate should ideally be between 100-160. However, I'm not sure what filter to apply to correctly display this data.
I tried applying a 100 point median filter. This got rid of majority of the low and high peaks. However, I was told that this removes too much of the detail and that I should use an average filter so that it more accurately describes the data. My argument against this is that \$\frac{100 + 0}{2} = \frac{50+50}{2} = 50\$. Many different values can give me the same average.
I do not come from a DSP background. Hence, how should I proceed? Are there other types of filter that will more accurately let me display this data? Ideally, I'd like to keep the general trend, but not include the sudden dips(any data that dips below 80) and spikes(any data that shoots above 200bpm).


texts:
I have a project with a custom USB device that pumps out a stream of data every 1.125 seconds to a Raspberry Pi running Windows 10 IoT, and occasionally receives an 8-byte command. The USB device and the Raspberry Pi are in a custom enclosure and I've got a nice touchscreen going for basic interactivity.

I was kicking around the idea of having the option of plugging a real PC into the device and having that take over the operation of the USB device. Let's consider the device-to-Pi connection to be permanent, and that I can wire an external USB port to my enclosure that connects to the device. I understand that USB is a point-to-point protocol and I can't just use a y-cable. I am able to modify the USB device at the PCB level.

Is there a way to do this? Ideally, I'd like the device to detect when a PC has plugged in and override the device-to-Pi connection and permit two-way communication with the PC while it's connected.

BOUNS POINTS: Is there a way to still receive the data stream at the Raspberry Pi? This would solve some datalogging issues.

I did find this: http://www.ti.com/lit/ds/symlink/ts5usbc400.pdf. It sounds like it might work (I can use Vbus of the PC to toggle the logic somehow, maybe), just glancing at the datasheet. However, this doesn't solve the problem of the bonus question.

If it helps, the USB device uses an NXP MK66FX1M0VLQ18 microcontroller.


texts: What are the benefits of this type of JFET biasing

texts:
The next schemtaic I was found as an input stage of ultra-linear phono amplifier.

What are the benefits of that type of biasing? I don't see that 12V zener has 12V voltage drop on it (only 4.2V) and in this situation how I can predict the Q-point of JFET?
What JFET's may be used with such schematic? I take JFET 2n4391 and the voltage gain of the stage drops dramatically.


texts: Are there rules for selecting wire gauge for single-pulse applications?

texts:
I'm trying to size wire for UL 508a panels. I have UL's wire gauge requirements, but those requirements are for continuous use. The device I'm designing will only run for two seconds, with minutes or hours between runs. Since currents of interest are 25, 50, 100, and 200 amps, there's a lot to be saved by not using wire rated for continuous use!

Is there a proper way to size wire for pulse applications like this? If the continuous ampacity of (for example) 75C copper stranded 4 AWG is 85 amps, how much can I run for two seconds? Is there some rule of thumb? Some equation? A table? Appropriate application of calculus?


texts:
I always thought that bodies of water were ground, meaning that any electric voltage that meets a lake for example would be immediately become grounded and the voltage would be that of the earth, in other words zero. I'm thinking of times when lightening strikes a lake and people nearby in the lake get electrocuted. I have two questions.

Why do people get electrocuted if the lake is ground?
Even if the lake is not ground, where is the current flowing to so that it flows through a person's body thereby electrocuting him?


texts:
I would like to convert the usb output of a scale to a serial format so I can read it through a com port.
I saw this tutorial from adafruit Adafruit serial scale but that scale is not available anymore and scales with serial output tend to be expensive.
I would like to take DYMO 10 LB and attach the usb port on it to a USB to serial and then attach this serial output to a serial to usb converter. Then I will have a COM port and I can read the data through a serial monitor.
The question is will I be able to read the data coming out of this and interpret it as a weight?
And if not, how hard will it be to write my own driver to read data coming from the scale?


texts: Common-Source MOSFET Amplifier Schematic & Analysis

texts:
From some practice problems I'm working on for my electronics exam:

  A Common Source (CS) MOSFET amplifier is biased at \$I_D=0.25 mA\$
  with a current source connected at the Source terminal of the MOSFET.
  The transistor has \$V_{OV}=0.3V\$, and a drain resistance of \$R_D=15
> k\Omega\$ connected to the DC supply of \$15V\$. The device has
  \$V_A=50V\$. The amplifier is capacitively fed from a source with
  internal resistance \$R_{sig}=100 k\Omega\$, and a \$20 k\Omega\$ load
  is capacitively coupled to the drain of the amplifier.

  (a)Draw the schematic for the amplifier system.
  (b)Calculate the voltage gain of the system.

This seems to imply that the MOSFET should be in linear mode, however when I draw out the schematic things just don't add up:

simulate this circuit – Schematic created using CircuitLab

In my DC analysis, the current through \$R1\$ must be \$0.25mA\$ therefore the voltage drop across \$R1\$ is \$0.25mA \times 15k\Omega = 3.75V\$. But, and here is where I think I'm screwing up, \$V_S = 0V\$ therefore \$V_{DS}=15V - 3.75V = 11.25V\$ which is way over \$V_{OV}=0.3V\$!

Doesn't this mean that the MOSFET is actually in saturation mode?

I assume I'm either forgetting or unaware of something basic... please set me straight.


texts: Where I can find good examples to run with Digilent Spartan 3E Starter Board?

texts: I'm looking for tips that are not on the site of the Digilent.


texts:
I'm designing PCB that includes 24MHz SMD 4 pins crystal.

According to my understanding, the crystal package marking is for Pin number 4.

I wonder, how should I indicate in the PCB this pin? Should I put a circle near this pin as I do to any SMD to indicate Pin #1?
actually, I did it but I'm not sure about it.

Is there any standard or marking for this situation?

Thank you very much.


texts: Alternative ways to maintain temperature stability of silicon BJT circuits other than feedback resistors

texts:
So I've been messing with Bipolar Junction transistors lately and I'm trying to really nail the concepts of designing circuits with these things cause I want to start using them in some of my circuits and maybe design my own amplifiers.

I've read online that if you want to make a temperature stable BJT circuit the easiest way is to place a resistor in the emitter junction and choose the resistance such that it's voltage when your circuit is stable is ~1.4V. I understand how it can accomplish this by being able to buffer changes in current due to the resistor proportionally changing it's voltage in response to the change in current, which thus inversely affects the base current and thus returns the circuit to the stable state.

However, what if I were to use 2 silicon diodes instead of an emitter resistor? Assuming silicon diodes have a voltage drop of around 0.7V each, the diodes would have a bias of 1.4V just like when we were designing for the resistor. Would that maintain temperature stability like the resistor did? I've found conflicting reports online but I can't really see how the diodes could regulate changes in current besides just keeping a pretty stable voltage drop of 1.4V.

Here's an little circuit diagram of what I'm talking about, disregard the component numbers if that changes anything:

Now I do notice that in this example the voltage across the collector-emitter junction will be greater than half of the supply voltage.(assuming beta is ~100). I've read that there's a principle or something regarding this case,and I've seen a lot of people design their BJT circuits with the collector emitter junction to be half collector supply voltage. Does this half supply voltage thing also temperature stabilize the BJT?

Tl;Dr If your collector-emitter is at half supply voltage and there's no feedback/emitter resistors is the BJT temperature stable?


texts: Anti-static wrist strap around your wrist or around your ankle?

texts: Does it matter whether you wear your anti-static wrist strap around your wrist or around your ankle?


texts:
In the below circuit, the diodes protect the LM317 against both of the caps discharging into the IC when input or output is shorted. LM317 is itself capable of having it's output shorted without damage. But the input-output voltage difference must not exceed 40V. In my circuit, I'm applying 45V to the input, and getting 30V from the output. In normal conditions this means a 15V difference over the IC and everything is fine, but if the output gets shorted somehow (maybe because of the initial charging of large capacitors connected to the output), I get a full 45V above the IC and this is enough to damage it according to datasheet (it's above the 40V maximum).

What can I do to prevent this, without using another IC like LM317HV?


texts: How to charge a battery when the charging socket is broken?

texts:
First of all I'll explain my situation: I own a Bluetooth speaker, more precisely this one: http://www.leicke.eu/en/products/EP18108

Due to my clumsy hands it fell while the USB cable was connected to the charging socket, and the USB socket split from the speaker's board. All features of the speakers work great, but I cannot charge it without the socket.

One solution might be to solder the socket back to the mainframe, but it doesn't seem a good idea with my standard soldering iron.

However, I can access to the battery which shows the black and red cable.

I'm not sure if I could charge the battery by connecting directly to a 5V source, or maybe that is not that simple and could damage the rest of the mainboard. Maybe I should take the battery out every time I would need to charge it... maybe you guys knows a better way to connect a charging circuit to this cables and perform a new charging socket in the speakers box.

Could you please give me a hand on this?


texts:
I saw lots of WiFi dongles withing the price range from $2,50 to $3,50 (eg. this one).
I am current doind a project using a microcontroller with usb, that requires WiFi.
I'm interested what kind of chips are used in these dongles and where can I buy them.


texts: Are tubes used for high voltage/high power h-bridge circuits?

texts: If so, when working with a load that involves voltages > 1kV and power levels well into the kilowatt range, which type of tube would be more useful: Triodes or Thyratrons? I saw a similar question about the possibility of using thyristors for an h-bridge control circuit. Could thyratrons be used as well?


texts: How to program Micro-controllers for beginners

texts: I have never worked with micro-controllers in my life, and have a small experience in programming. I know a bit of java and TI-basic, but haven't ever made any useful programs. I have random micro-controllers sitting around (i have a few PIC's and an ATMEGA168.) First, I am wondering what hard-ware I need to get to connect it up to USB. (I don't think it can just be a direct connection), second what software should I get (mac or windows, or even linux it doesn't  matter), and last, for someone horrible in programming, what is a good way to learn, and what language does it require. How do computers work to communicate with these devices?


texts: Solutions to covering exposed pin headers using a cap?

texts: I have the following 6 pin headers exposed which is attached to a cable. I was wondering if there was a solution to protect the pins using a cap system like a usb stick cap. Since this will be going in my bag, I dont want to have it break/bend during travel.


texts:
Is there a way in eagle to center a trace between two pads? and by center, I mean directly center it with even spacing on both sides of it.

I'm asking because its easier to solder pads that aren't too close to another trace and I don't want to create any shorts. Also, I believe having traces too close together introduces on-board capacitance.


texts: Why is noise power not multiplied by spread gain?

texts:
In my intuitive consideration, noise power should be enlarged as spreading gain times. The reason why I think this is:

Let us consider that the information signal is of bandwidth W Hz.
Then, the receiver suffers from the noise of bandwidth W Hz as well.

If we do the spreading work into the information signal with chip rate. Commonly it is much larger than W Hz. Then, (information signal X spread spectrum signal) will also have much larger bandwidth than W Hz. Thus, the receiver suffers from the noise of bandwidth much larger than W Hz.

Since noise is BW*N0/2, where BW=bandwidth and N0=noise density, I think much larger noise happens.

Why do people say DSSS makes much better SNR? (roughly, people say SNR will be increased around spreading gain times.)

$$C = BW \log_2 ({1+SNR}) \quad\longrightarrow\quad C = BW \log_2 ({1+G\times SNR})$$

Edit!!


texts: What's the difference between a thermal imaging sensor and an infrared CCD?

texts: I was always under the impression that thermal radiation is essentially infrared energy, so what's the difference between a full thermal imaging camera (e.g. an FLIR) and a standard infrared CCD chip? Surely the latter should function as the former? Yet the price difference is astronomical.


texts: Applying a voltage at the output of a linear regulator

texts:
I'm working on a fairly complicated project and in the process I encountered a fairly simple problem. My project has a microcontroller which will, of course require programming. However, the PCB will draw its power from a custom designed motherboard, and for the purpose of testing and writing the firmware, it would be grossly inconvenient to require that it be connected to the motherboard simply to program it.
My solution was to simply stick a header onto the 5 V rail and power it externally. However, the 5 V rail is supplied by a linear regulator (LDL1117), which bucks 6 V from the mobo down to 5 V. This means that if I power the rail externally, the regulator will have 5 V at the output, while the input would be floating. Is this inherently a problem? Could this damage the regulator?


texts: What is the relationship between the current produced fuel cell, the electrodes and the voltage of a fuel cell?

texts:
I read somewhere that the bigger the surface area for the redox reductions to take place, and ultimately, the more redox reactions that take place, the more electrons that flow through an external circuit and the more electricity that can be generated. If this is the case, what does the voltage of a fuel cell, which I believe is caused by using dissimilar metals for the electrode and anode (correct me if im wrong) has to due with the amount of electricity and electrons generated?
doesn't V=IR tell us that for some fixed Voltage we will get some fixed current if resistance is kept constant.


texts: Which capacity measurement is the correct way to measure?

texts:
So I've seen batteries showing their capacity in mAh and I've seen others showing in Wh. Phone batteries are always measured in mAh, while for some reason BatteryInfoViewer on my computer only shows in Wh, but doesn't show any amp levels.

So here's two different batteries.

My phone's battery; 3.1 Ah x 3.85 volts = 11.9 Wh
My laptop's battery;  42 Wh / 17 volts = 2470 mAh

When you look at it in mAh, the phone's battery seems to have more capacity than the laptop, which made no sense before. But now with Wh, laptop's battery has 3.5 times more capacity than the phone. Why do we have two different measurements for capacity?

But I really don't get it... Why is it less in mAh but more in Wh? I get that it's because of voltage but that's not the question.

The question is... If I were to somehow use my laptop's 3100 mAh (42Wh) battery on my phone, would it last longer or shorter?


texts: Will discharging work if the grounding chassis isn't connected to the mains or otherwise grounded?

texts:
Suppose you have a CRT screen and you want to dismantle it for whatever reason. The high-voltage anode needs to be grounded in order to avoid the risk of electrocution. The metal grounding chassis of that RCT screen won't work unless it itself is grounded which it isn't if it isn't connected to grounded mains or grounded otherwise. Am I understanding this correctly?
It made me wonder after watching this video https://www.youtube.com/watch?v=SdFIi-ZF-6M&t=102s . Am I missing something here? Is that really a correct way of doing this?


texts: Common mode and differential mode noises

texts:
I want to understand common mode and differential mode noise more intuitively.

I have read this article. But I would like some analogy or experience with real circuits with some example to understand better.

Can someone please help. I have read answers in this forum too. But it didn't provide clarity.
I would be able to understand the answers if it is in the more basic level which is why I am asking some analogy.

Please help. Thanks


texts: What are the names of these types of cables?

texts:
I need the name for these cable connectors, for use in a user manual

The flexible part has 4 lines and connects to hearing aids.

The smaller end has 4 holes and connects to the end with the label CS 64 of the cable in the first figure. The larger end looks like a male 6 pin PS/2 connector. Both cables are required for programming hearing aid through I2C bus.

What are the names for these cables?

EDIT1: Close up of the flexible cable attached to a hearing aid


texts: So, I want to make AC 220V to DC 220v rectifier. Can I use two or three diodes in series, because the reverse voltage maximum of one diode is about 60 volts?


texts:
I want to build a robotic arm for a project, but I got stuck while testing the motor driver on the breadboard.

I have followed the instructions from this instructable: https://www.instructables.com/id/Easy-DC-Motor-Controller/ and I connected the pnp transistors the right way (the author confirmed in the commentaries a long time ago) and also like in the diagram.

The problem is that when I turn the power on, the motor starts to spin (slowly but it has a snail gearing reducer) and the first mosfet is getting very hot very quickly, and if I try to control the circuit by touching the first contact with a positive voltage it doesn't do a thing. I even tried doing only half of it.

I tried to reassemble it again many times, changed the transistors with other new ones, checked the connections and after numerous voltage measurements I concluded that the problem is that, when I am powering up the circuit, for some reason, there is a 12v voltage between the pnp collector and ground and the voltage continues all the way to the resistor to the far left, although at the resistor the voltage is dropped to about 7v.

I also simulated the circuit in proteus before i bought the parts (I need 6 good working drivers) and it worked fine.

It may be a stupid mistake, but please help me if you have any idea what the problem might be!


texts:
I have been doing the question below in what I thought was the correct way. After doing some more reading I am now slightly confused and would appreciate some clarification. Previously I was just using a 4 line cache and recording hits/misses based on the binary numbers shown.

After doing some more reading I found that the address (comprised of the tag & line portions together) gives the block number in main memory, meaning there should be 16 slots in memory.

As far as I read using direct mapping the first line of cache should hold the values of the 0,4,8,12 main memory blocks and so on for each line. This makes me preety confused since I thought when the tag was different to the one currently stored it would take that as a miss and go searching. Can anyone explain this to me ?

sorry if this is hard to understand.


texts: Arduino HC-SR04 sensor through CD74HC4051E multiplexer using single wire

texts:
I'm trying to get distance using HC-SR04 sensor and arduino. I've connected together Trig and Echo pins on the sensor, then it goes to port A7(pin 4) of multiplexer(selectors configured as follows: S0 high S1 high S2 high).
I uploaded code from examples(sensors/ping) and pingPin connected to in/out of multiplexer:
only I've changed duration of trig impulse to 20uS.
If I don't use multiplexer and connect pingPin directly to sensor everything works. If I disconnect pin of sensor from mux, I get some random values from mux out pin, it's okay. If connect pin from sensor to A7 it reads only zeroes from mux in/out. And it prints zeroes more slowly than when connected directly and working. So I guess I'm not getting any impulses from sensor or my trig signal can not go through.
I've just tested port A7 from mux with long trig impulse. When not connected to sensor it's 0 5 0 5 so it's okay. But when connected to sensor it's only 0V 1V 0V 1V and not 5. Maybe problem is here?

Why doesn't it work?

It works like that: arduino sends HIGH impulse 20uS long to sensor and then waits for HIGH impulse from the same pin and I get duration of this HIGH impulse.

Code from examples:

const int pingPin =3;

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

void loop()
{
  // establish variables for duration of the ping,
  // and the distance result in inches and centimeters:
  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delay(1000);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);

  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();

  delay(100);
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

datasheet 74hc4051
sensor datasheet

Maybe it's important?

  Effectively the selected channel has around a 80 ohm resistance
  (between the selected pin and the common pin) achieved by side-by-side
  MOSFETs (one P-channel and one N-channel). The unselected channels
  have a very high resistance between them and the common pin.

Maybe I should connect trig through transistor and A7 to its base?.. tried. didn't work.
So I think problem is really in low voltage from A7.. 1V there, not 5..


texts: Interfacing Problem with 16 MG996R servos

texts:
I am using 16 MG996R servo motor with PCA9685 servo driver and Arduino Uno, but the motors are not working properly.It works well a Month ago but is not working now.
The servo only twich a little when I connect external power supply.


texts:
Disclaimer: I am a total newbie

I have something I bought that once is switched on does something each time I press a button, now, I want that to happen periodically(no accuracy needed) so I was thinking on substituting that button for something.

Is there any simple thing I could put there which would give me a periodic "button press"? Doesn't need to be accurate and I would be thinking on ranges from 5 secs to 30 secs, but anything is acceptable really, I would prefer non-ic alternatives.

Basically I want to swap something like this:

with a timed "push event"


texts:
simulate this circuit – Schematic created using CircuitLab

I have an output that can operate a relay at 12V but the drop out voltage is 6V. So the relay never drops out once pulled in at 12V, even though the voltage across the coil is 6V. I understand as per the datasheet, must drop-out voltage must be below 1.5V. How can I drop-out the voltage to less than 1.5V when the voltage is below say 9V?


texts: Does the weight of a mass effect the transfer function of a vertical mass-spring-damper system?

texts:
Usually in system dynamics, I dealt with horizontal mass spring dampers. Now in my advanced class I am dealing with vertical mass spring dampers. So a spring is hanging from the ceiling with a mass connected, and then the damped is under the mass. The damper is in some sort of oil and that is creating the "damping" effect.

In this problem, the spring is assumed to be negligible mass, but the damper has a mass, along with the weight that is acting as the mass.

I know that for a mass spring damper system (when its horizontal), the transfer function is
$$H(s)=\frac{\omega_{n}^{2}}{s^{2}+2\zeta\omega_{n}s+\omega_{n}^{2}}$$

But now the mass of the weight and damper are acting on this system. So does that affect the transfer function?


texts: Purpose of the C3 in this Transistor Arrangement

texts:
I'm working on building this circuit which is based on a "Fuzz" distortion guitar effect, and am wondering what the purpose of C3 is, connecting the two collectors of the transistors.  Is it for some type of DC blocking between stages?  Most other design schemes I've seen for this type of circuit don't have any connection at this point.  Does the actual capacitance value matter much at this junction?  Any advise or reference to a source where I could learn more would be greatly appreciated.
Circuit designed by Mad Bean Pedals


texts: How to command a 220v device through a 12v output

texts: I have a vending control board whose output is 12v-DC but the problem is that with this device I have to control a device whose input is 220V-AC. Can anybody help me make this possible? Sorry for my dumb question but i am relatively new to electronics.


texts: How does current flow through a voltage source?

texts:
Im going back to electricity 101 to understand several things Im missing. One of them is exactly how does current flow through a DC source.

Heres my understanding: A voltage source is one which has an excess of electrons in one side of its terminals, and a lack of electrons in the other, when connected together via a resistance or cable, electrons will flow from the side with an excess of electrons, to the side with a lack of electrons.

Inside the source itself theres no current flow, only "around the supply", meaning if I have say a battery, the only way that electrons will go from one side to the other, is by connecting a cable from its + to - side, the electrons will flow through the cable all the way to the other side. When both sides have reached an equilibrium in which both have the same amount of electrons, theres no voltage potential (dead battery), thus no current flow.

Very often a textbook will substitue components for DC sources, for example if we have a voltage source connected to a diode in series with a 2 resistances, the equivalent circuit  will substitute a 0.7V DC source for the diode, and add the 2 resistance in series with it such as this:

Lets take this circuit:

The equivalent circuit is the following, where V2 equals the diode:

So the way I understand it, in the circuit above, replacing the diode with say a 0.7V battery or 0.7V DC power supply would be the same as having the diode, yet, how is it possible that current will flow from the positive terminal of V1, through the resistor, THROUGH the 0.7V battery (or dc supply), through the second resistor into the negative terminal? I thought that no current could flow through a battery or dc source.

I used a diode to make an example but there are several places in which Ive seen multiple voltage sources in a circuit, yet I dont understand how can current go through them.


texts:
I'm struggling to understand the pin order on a ribbon cable.

I want to connect two boards (one main board with the MCU, the other one for the front panel to pots and buttons) and i need a 2x20 connector to connect the boards. I found on Mouser this connector but i can't find the related cable. I don't need to use that specific connector, it is just one that i found searching on Mouser.

On top of that, i need to understand what's the pin order using this cable. Basically how can I connect the two boards without swapping pins.


texts: Calculate phase shift from desired power factor

texts:
I'm learning how to calibrate energy measurement device, and acting upon colleagues instructions I'm getting worse results in each iteration. I'd like to check with someone here if instructions are correct.

Calibration requires to set such load to have power factor 0.5. According to instruction, I need voltage at 240 angle and current set at 300 angle. However, this results in worse result. Setting 240 angle of voltage and 180 angle of current provides expected results.
Which phase shift between voltage and current here is correct?

I'm aware my question is probably faulty in many ways, however this is best way I'm able to express with my current knowledge.


texts:
I got a 110V version of the Aoyue 968A+ soldering station by mistake and shipping the station for a replacement or selling it is not an option. I reverse engineered part of the station looking for the cheapest way to convert it to 220V input capable (instead of using a 220V to 110V transformer).

This is the bit of the pump and hot air gun driving circuit that I reverse engineered. I'm wandering if it could be "fixed" by placing a diode between say the TRIAC and the hot air gun heating element therefore chopping half the 220VAC mains sinewave. The pump seems to be the same for both 220VAC and 110VAC versions of the soldering station though, so I'm thinking how could I find out if 220VAC was to damage the pump.

simulate this circuit – Schematic created using CircuitLab

Hot Air Gun Heating Element:

On the other hand, there's also a transformer with 110VAC input and 24V and 9V outputs for the soldering iron and the 5V linear regulator tied to the logic circuitry respectively. Is chopping half of the 220VAC sinewave before the transformer input a solution too? I saw a post about half wave rectifying and a hefty discussion about its effects on the transformer, so another option would be trying to wind more turns into the primary winding, would this be advisable or too much work / space required to achieve it?. I have yet to reverse engineer this part of the cricuitry but there's also an optocoupled BTA12-600C TRIAC that's controlling the soldering iron heating element.

Transformer Label:

Transformers Remaining Space for Extra Winding:

This is the PCB with the heaters and pump controlling circuitry:

On a side note:
I'm willing to upload a schematic of the remaining circuits if the MCU on the bottom layer was to be identified. It's a 7mmx7mm 32 pin ~0.7 pitch TQFP marked as " REN10 509 H3G1 " with the following pinout ->

Pin 1 - 5V

Pin 2 - "M" programming?

Pin 3 - "R" programming?

Pin 4 - NC (in this PCB)

Pin 5 - GND

Pin 6 - NC (in this PCB)

Pin 7 - 5V

Pin 8 - NC

Rest of the pins - apparently GPIO


texts:
Starting with JK flip-flop, show the design of a D flip-flop with a synchronous reset, R.

I know how to create a D flip flop with J-K flip flop, but i'm not sure what "synchronous reset, R" exactly means. Is it another input in D flip flop that resets output when is active? And what's the point of it?


texts:
In below circuit I pointed(red arrow) the part with "power supply rails with two caps".

As you see, it is drawn seperately from the main circuit.

1-) Does that mean the capacitors C1 and C2 are optional?

2-) I'm having some days spikes from the circuit output(ADC). I was planning to investigate the power supply. Below is the sampled data from a noisy day. Is there a possiblity that this can be power supply noise?:

edit:

Here AC coupled scope view of 15V to gnd rail:

Here in freq. domain:


texts:
According to the Sedra/Smith Microelectronic Circuits textbook, 6/7 eds.,  increasing \$v_{DS}\$ beyond \$v_{OV}\$ has no effect on the channel shape and charge.  Why is that?  It seems as if (thinking naively) increasing \$v_{DS}\$ should move the point at which the channel is pinched towards the source, thereby decreasing the charge in the channel.  Also, if \$v_{DS}\$ is large enough, wouldn't we have some sort of breakdown?

The textbook says further that any increase in v_{DS} above the saturation threshold appears as a voltage drop across the depletion region.  Why is that?

A related question: why is the bottom of the channel a straight line?


texts:
Why I cannot to choose some parts as breakpoint in the Keil? please consider to these pictures:

If you consider to some parts that I determined, you will know that I cannot to select those as a breakpoint. Why? some of them are function. that's odd to me.

Note that we can choose some parts that are determined with a gray square at the left but if you consider the parts that I determined don't have it.


texts: Review/improve anti collision circuit using hall effect sensors

texts:
I'am designing an anti collision circuit with hall effect sensors.

Mechanical principle:
it's basically two squares, one smaller than the other. The largest square hits an obstacle making the magnets move past the sensors, and the movement shall stop.

The hall effect sensors goes low then the magnet is near.

Electrical Principle:
My design idea is to wire the four sensors parallel with a resistor on each output pin.

In normal state the resistance would be small and a low voltage drop will appear. But then one magnet is out off range from the hall effect sensor, there will be three parallel resistors which will give a larger voltage drop.

I'am using a window comparator(good old LM324) to check the voltage and turn on a solid state relay, which turn on a power relay(controlling the movements).

The idea is that the 10k resistor should be mounted at the sensor, making it possible to detect short circuited wires(GND/10V to output)

Schematic

Questions/worries

The difference between the two states is only 0.3V. I would like to raise this  to a coupled of volts. How would you do it? (I tried with some diodes and LEDs but did not go as expected)
Is the circuit design to sensitive ? how would you have done it?


texts: When using PWM, what is the purpose of having two complimentary square waves on the same channel?

texts:
I'd like to use the PWM I/O on the SAMA5D2 Series Microprocessor (Microchip).What I'm confused about is why each PWM channel has a high and low output pin. The datasheet specifies

  Each channel controls two complementary square output waveforms.

My understanding is that you only need one of these outputs to drive an external peripheral such as a fan. In what instance would two complementary PWM outputs be used?
Also, do I need these two complementary waveforms to drive a 4-wire PWM fan?

I've added a I/O description and timing diagram example from the datasheet for clarity.


texts:
I hope someone can help I am trying to find out what this component is so I can hopeful replace it

The device is a Fluke Network Management device

the unit works for about 2-3 minutes depending on temp then gives out a high pitch squeak the unit keeps flashing looks like there is life but the unit stops responding
I first thought it was the PSU from where the noise was coming from

I striped the unit down set it up on my desk plugged it all back in and waited the noise not sounds to come from the main board in the photo it is where a second board plugs in and the power supply comes from

All the but has on it is 8Y I have looked high and low the best I got to was a 3 pin transformer or a rectifier but not 4 pins plus I'm not sure if the specs are the same or if its a transformer or a rectifier

I am going to pull some none working devices apart to see if there is one in something else

Update

I have not received very much from Fluke nothing from technical

So to get things moving I have removed the part not the cleanest of removals but I just sniped it off

It looks like a common mode choke with help from people on here to me but its the values of it that I'm not sure of, is there any way to work it out the unit will take 100-240 VAC 47-63Hz 25 Watts not sure if this helps

would this be a replacement TDK ZJYS51R5-2PT Choke

I've got nothing to loose the unit stop working after this bit gives a high pitch noise

If anyone can help me would be good

Thanks


texts:
I want to power a 5V white LED strip (50cm) from an Arduino (Leonardo, connected through long USB cable to my PC permanently). The idea is to have the LEDs dimmable through the Arduino pwm signal. I have trouble getting enough brightness from the strip.

When I connect the strip directly to USB I measure 300mA and get full brightness.
When I connect the strip to the Arduino output I measure 30mA and brightness is way too low.
When I connect the strip to a ULN2803A Darlington driver (connected to Arduino VCC (4.6V) and output) I measure only 18mA
When I connect the strip to the ULN2803A but to an additional 5V USB I measure 95 mA and get a brightness that would be acceptable for my purposes but requires an additional USB connection which I would like to avoid.

Browsing on internet (I'm just a hobbyist) I got the idea to use a boost converter to get a higher voltage on the LED strip. Would that be a good idea or are there simpeler ways to get more brightness?

ULN2803A datasheet

LED strip data: 3528 SMD 30LED power consumption 4W/m (I use 50 cm)

The reason for me to think about a boost converter was because the USB is 5V and the Vin of the Arduino is 4.6V so I thought that this difference could be the problem.


texts: CMOS gate logic switching time based on input vectors

texts:
My question is regarding CMOS logic gates switching time based on input.

Say I have a NAND gate and my input vectors are:

00 | 1
01 | 1
11 | 0
10 | 1

So, the output is not switching in case of the first 2 vectors and switches for the rest.

I would like to know if the gate will temporarily lose its Logic 1 state and in the process adding to compute time when the input toggles from:

00 ---> 01

I need to know this as I have built a gate level netlist (verilog) simulator which adds to compute time only when the output toggles. I need to know if my approach should look at the input values instead.


texts:
I went for an interview for scientist position in BARC India.
They asked this problem

How will you measure a high voltage like 765kV AC ?

I replied that we can step down using potential transformer and then measure it using a voltmeter.

Then they said tell me some other method?

How will you measure HVDC line of 500kV?

I was not able to answer all this. Please help me with this problems.


texts: How can I replace 10k potentiometer with 5k joystick?

texts:
My YAMAHA PSR S950 pitch bend is broken, and it got 10k potentiometer inside.
Everything I got here is some joystick, and Arduino (if that helps).

Finding exact size 10k potentiometer is not going to help, as everyone sells them for $50 here.


texts: Looking to create 36 channels of PWM control for LED sculpture

texts:
I'm a sculptor, not an EE, but I'm trying to incorporate controllable LEDs into a piece that I'm working on, and I could use some advice figuring out a practical approach. I'd like to be able to control 12 separate channels (the piece is a dodecahedron) of RGB strips, and that means I'll need 36 PWM outs, which is more than I have access to on an Arduino. As far as I can tell I'll need a shield, something like TLC5940 Breakout - though that only gives me 16 PWMs so I'd need to daisy chain three of them, which I know can be done, but I'd like to know what issues might result. Something like Brilldea LED Painter might also be a solution, but I'm relatively pressed for time, so something pre-assembled would be a nice perk.

I'm new to this, so I'm not sure of the accuracy of what I just said, but hopefully some of you can fill me in on what might be a reasonable approach. Thanks for your help.


texts: Arduino standalone with 9V battery and accelerometer

texts:
I'm using an Arduino Mega for a project involving an accelerometer. Everything works fine when the board is connected via USB. When I use a 9V battery plugged in with the 2.1mm jack, values are completely messed up.

I'm using a MMA7260Q triple axis accelerometer, which gives an analog voltage for each of the three outputs. The voltage is in ratio to the measured acceleration and to the supply voltage. In order to read the correct values the following code is required: (in the 800 mV/g mode)

 int accValX = analogRead(A0);

 accX = (((accValX*5000.0)/1023.0)-X_0)/800;

Probably the voltage is not constant and that affects the acceleration readings.

I've connected the sensor as shown below. The picture is from this tutorial, the board I've used is the Mega version. The 9v battery is used with the 2.1mm jack and a power adapter as show here.

Am I using the correct set up to power on the board? Or should I use the Vin pin to supply the 9V...
I've read in this question that 9V batteries are not the best choice to power on the Arduino for a standalone application. What does a LiPo-powered setup require?