texts:
I'm a beginner and trying to figure out how this circuit works (its a simple circuit that glows an LED when dark) :

https://www.youtube.com/watch?v=eIGWWKThprI&list=UUhtY6O8Ahw2cz05PS2GhUbg#t=65

schematic http://makezineblog.files.wordpress.com/2014/10/wp20_schematic_w_circle-transistor.png?w=1410&h=827
My confusion is when the light is present, wont the current still flow through the collector and base of 2N3904 ? This is connected in parallel ? How does this circuit work ? How is the LED portion of the circuit not closed when light is present ?

Ref:

http://makezine.com/projects/dark-detecting-led/


texts: Is it better to bootstrap a step-down converter from the input or the output?

texts:
The title may be not put so well. What I want to know is if it is better to draw energy for bootstrapping from the input like this:

simulate this circuit – Schematic created using CircuitLab
Or is it better drawing energy from the output like this?:

simulate this circuit
This question came to my mind when I saw on page 8 in this datasheet the option to use Vin or Vout for bootstrapping:

I think it is best to use the input for bootstrapping, since you don't want to draw more current from your output, since you want it to be as steady as possible in a switch mode supply/IC.
In my case, Vin=5V, and Vout=3.3V.


texts: How long can I power my device using a battery?

texts:
Lets say I have a battery that has 100mAh, and I am using it to power an IC that according to it's datasheet, consumes 1mA.

I understand that if I were to connect my IC to a bench power supply I would see it consumes 1mA (if it has a display), and theoretically I could leave it running constantly for months, but what about connecting it to a battery? How can I calculate the minutes/hours I can leave the device running?


texts: Can we use both FFT and PSD to obtain a random signal's frequency domain representation?

texts:
I always encounter random noise frequency domain representation as PSD(not FFT), something like in the below plot:

Without diving into math too much, practically speaking can we always use FFT instead of PSD to characterize a random signal? If so, what is the reason to use on to the other method in practice?

It even gets a bit more complicated because most of the time the signal can have both random and periodic components. Imagine I measure the constant pressure flow with a transducer's analog output. But those signal I sample will have both periodic and aperiodic components and random noise etc. In such case, if we have sampled the signal with enough sampling rate, what method between FFT and PSD would be preferred?

I before studied some Fourier series and transform and used many times FFT functions on MATLAB or Python for freq. domain view of a signal. Why would one need PSD if FFT is enough to for all types of signals?

(Digital scopes, for instance, show real-time FFT of a signal but not PSD. So not always PSD and not always FFT is used. How to decide which one to go for?)


texts: Eagle PCB- DRC Errors: Drill distance and size

texts:
I am new to Eagle, so please be polite if I am in the wrong area.

I added two mounting holes and had to move some components for clearance.  I also extended the board size slightly to accommodate the component move. I also did a ripup; to remove all routing.  The drill size is 0.125 in to use with a 4-40 screw. (The board grid is 100 mils)

After running Autoroute (all parameters are default), then checking for errors, I got this:

There are two identical holes, but #1 is the only problem in the error list.  Can anyone tell me what's wrong with hole #1?

I tried manually routing the trace near hole #1, but I get the same error.
Thanks, Steve


texts: Purpose of the series resistor in this schematic? (PFET Gate)

texts:
What is the series resistor for in the picture below?

My only guess is to modify the rise time of the gate?  If it is for the rise time, how would you calculate the right value for the resistor?

Also would a 10k have worked just as well for the pullups instead of a 47k?

(added links for the PFET and Opto)

sihfr911.pdf
PS2801C


texts: Problem with SPI communication to TDC-GP30 Ultrasonic Flow converter

texts: I'm working in TDC-GP30 an Ultrasonic Flow converter chip. Which can be directly hooked up with ultrasonic transducers to get digital output. But the problem is according to the datasheet the chip can respond to Remote communication through UART or SPI. when I tried with the default baudrate 4800 in UART to communicate with the chip I got some reply as a junk value which i can't interpret. so I switched to SPI communication and tried to read the registers by the address but all im getting in 255 as output. I have no clue what to do does anyone have any experience working in this which would help me


texts: Altium Bus on multiple sheets - pins without connection

texts:
I am running into an interesting problem:

SoC connected to an eMMC memory
Data bus width: 8
SoC provides 2 x 4 data lines

4 data lines by default, additional 4 are multiplexed on SPI pins

The SoC was devided into lots of different sub-groups. 4 of the data lines are on sheet A, the other 4 on sheet B. I tried to connect the sheets using a bus and ports in a hierarchical design.

In the PCB document, when selecting the bus in the Nets, all pins are highlighted as expected (8 on the eMMC, 8 pullup resistors, 8 on the SoC).
But somehow the four pins on the seperate sheet are only highlighted. They are not connected. (In the zoomed section, the selection was removed and one of the pins nets highlighted to show there is no air wire/connection shown).

I am pretty sure something is messed up here, but I don't see what this could be. Maybe you guys know?


texts:
I'm having a Direct Form 2 Diagram created from a signal

The task I'm trying to solve tells to assume that every multiplication != 1 and != -1 gives sigma² amount of noise. We should mark the occurrence of noise and then try to merge the noise to as few as possible noise gates.

Imho I'd have 4 noise gates

x[n] = 5/6 y[n-1] + a[b] - 1/6 y[n-2] + b[n] + 2 x[n] + c[n] - 5/6 x[n-1] + d[n]

where a[n], b[n], c[n] and d[n] would be the added noise from each multiplication.

I'm not sure if that's correct but if so: Can I "merge" or "move" around the noise gates in the Direct Form Diagram e.g. like this:


texts: Capacitor Discharging Time under a Sinusoidal Voltage Source

texts:
I just can't find the correct solution to the following, pretty basic problem:

A capacitor \$C\$ is continuously discharged by a resistor \$R\$. This is easily described by an exponential decay (\$\tau:= RC\$):
$$
U_C(t)=U_{C,0}\exp(-t\tau^{-1})
$$

Hence, a time \$t_1\$ can be calculated at which the voltage reaches a specific, lower voltage \$U_1\$:
$$
t_1 = -\tau\ln(U_1/U_{C,0})
$$

Now consider a sinusoidal voltage source which, as its voltages increases over time, will reach the voltage of the discharging capacitor and will thus recharge it. I'm searching for this exact moment in time \$t_2\$.

My Approach: Equating the capacitor discharge formula and the given voltage function:
$$
\hat{U}\sin(\omega t_2) = U_{C,0}\exp(-t_2\tau^{-1})
$$
Using Euler's Formula yields
$$
-\mathrm{i}\hat{U}\exp(\mathrm{i}\omega t_2) = U_{C,0}\exp(-t_2\tau^{-1})\\
\Longrightarrow\ \exp(\mathrm{i}\omega t_2+t_2\tau^{-1})=\mathrm{i}U_{C,0}/\hat{U}\\
\Longrightarrow\ \mathrm{i}\omega t_2+t_2\tau^{-1}=\ln(\mathrm{i}U_{C,0}/\hat{U})
$$
Using the complex logarithm gives
$$
\mathrm{i}\omega t_2+t_2\tau^{-1}=\ln(U_{C,0}/\hat{U})+\mathrm{i}\arg(\mathrm{i}U_{C,0}/\hat{U})\\
\Longleftrightarrow\mathrm{i}\omega t_2+t_2\tau^{-1}=\ln(U_{C,0}/\hat{U})-\mathrm{i}(\pi/2+2k\pi)
$$
Since we don't leave the first periodicity (\$0\$ to \$2\pi\$) \$k=0\$ should be applicable. We also expand the denominator:
$$
t_2=\frac{(\ln(U_{C,0}/\hat{U})-\mathrm{i}\pi/2)(\tau^{-1}-\mathrm{i}\omega)}{\omega^2+\tau^{-2}}
$$
Only considering the real parts again yields
$$
t_2=\frac{\tau^{-1}\ln(U_{C,0}/\hat{U})-\omega\pi/2}{\omega^2+\tau^{-2}}
$$
which sadly only returns unrealistic values in my simulation.

How can I find \$t_2\$ correctly?

Example:
As requested, a short example is presented below. In this case \$U_e=\hat{U}\sin(\omega t)\$ is the input voltage used above. However, \$R_1\$ is the charging resistor and is not considered here as there already is a simple approximate for the time \$t_1\$ when the capacitor stops charging. Thus, \$R:=R_2\$ was used in my description above.

I've marked the time \$t_2\$ at which I want to re-apply the current charge function which already is implemented for the first part (\$t<t_1\$) of the capactior voltage function.
The "finished simulation" would inlcude an alternation of charging (cap. voltage increases) and discharging (cap. voltage drops).

Regarding Jan's Answer:

I've plotted the given equation, which seems to lack an expected exponential decay:

Using the following component values

resulted in the following simulation result:

Even though the extreme values seem to somewhat match, I'm really at a loss why your solution doesn't give the same result.


texts: How can I get GPIO working on the Orange Pi Zero Plus (v1)?

texts:
When running the pyA20 library in python I get the error:

AttributeError: module 'pyA20.gpio.port' has no attribute 'PA0'

Or when running gpio readall I get the error:

Oops: Unable to determine board revision from /proc/cpuinfo
 -> No "Hardware" line
 ->  You'd best google the error to find out why.

Ive tried editing /proc/cpuinfo to make it the same as a standard Orange Pi zero but it wont allow me to save

Please note Im using Orange Pi Zero PLUS


texts: Switch-mode power supply and EMI on input power line filtering

texts:
I'm trying to reduce some switching noise I'm seeing (using LISN & Spectrum Analyzer) on my input power cable. My SMPS operates at 1.2MHz. I have room on the PCB and I'd like to place a SMT common mode choke with a couple of filter capacitors on the input and output of the choke. I was hoping to make a sort of Pi filter.

The device will use 12V from a vehicle cigarette lighter at approximately 75mA. I believe the output resistance of the car battery is relatively low.

I've looked at this Murata Noise Suppression PDF and I see a few examples of possible solutions but no Pi filters.

Any suggestions? Am I going at it all wrong?


texts:
simulate this circuit – Schematic created using CircuitLab

Yes, this circuit diagram is correct. No, I did not design it.

How do I describe this circuit in words? I thought about "a switch and light bulb in parallel, instead of series" but the circuit is so bizarre that I want to make sure what I am saying is unambiguous.

I cannot insert a schematic/picture/diagram/drawing, and I have a fairly tight word limit.

If anyone knows the tags for this question, add them.

EDIT (due to interest from the comments): The circuit was made by my 3rd grade teacher for an electricity test (when she thought the questions from the curriculum were too hard for us...)

EDIT 2: No, this is not a fancy NOT gate. The question was "What will happen when the switch closes" and the teacher-accepted answer being "Lightbulb turns on"


texts: Things to be aware of when using voronoi shaped traces

texts:
I was thinking of giving voronoi shaped traces (e.g. http://publications.csail.mit.edu/abstracts/abstracts05/rus/rus.html for those who need an example, or just google image search it) a try.

In general is there something I should be aware of, compared to traditional (more or less) autorouted traces, that could fail or needs special care of or could fail to work as desired?


texts: Unable to convert ultrasonic sensor 5V echo to 3.3V using TXS0108E 8 Channel Logic Level Converter Bi-Directional

texts:
I'm trying to use an ultrasonic sensor with a Raspberry Pi. The ultrasonic sensor's echo is 5V, but the Raspberry Pi's GPIO pins can only handle 3.3V inputs. I ended up getting an 8 channel logic level converter to convert the 5V signal to 3.3V since I have three ultrasonic sensors I need to do this for and wanted to avoid a mess of resistors.
I believe I have set everything up correctly, but I am unable to get the 5V echo to convert into a 3.3V signal. I have verified that the ultrasonic sensor is working. If I skip the voltage conversion and allow the 5V echo to go straight to the GPIO pin, I can see the distance is being measured correctly.
I created a diagram showing my current approach. The ultrasonic is connected to ground and a 5V power. It receives a 3.3V trigger signal and provides a 5V echo signal. The 5V echo signal goes to B2 and should be coming out A2.
I tried connecting OE to 3.3V, 5V, and ground, but none of those combinations work. I have also verified that the A side is supposed to be receiving the lower voltage and the B side is supposed to be receiving the higher voltage.
Research
Here is an example I found about the usage:
Example wiring for bidirectional 3.3V to 5V conversion:
VA: 3.3V power +
VB: 5V power +
GND: Ground (-) from the two power supplies (3.3V and 5V power supplies )
A1 to 3.3V pin (such as from Raspberry Pi)
B1 to 5V pin (such as from Arduino)
When A1 has a high 3.3V signal, B1 will output the same signal at 5V and when B1 has a high 5V input, A1 will output the same signal at 3.3V ( No direction control required because this product is bidirectional! )

Here is a very helpful Youtube video
Here is another (less helpful) Youtube video
Additionally, I found this post which seemed relevant, but I'm not very familiar with electronics and wasn't sure if the issue in that question was the same.
I would really appreciate any advice. Thanks!


texts:
For the circuit shown in the figure. Assume that the swich is closed at t = 0
Find the final energy stored in the capacitor?


texts: Is it safe to control a solid state relay from the MCU output?

texts:
I have a +/-30V and +5V signal. I would like to rout this two signal by using the CPC1106N and CPC1006N solid state relay. According to the Absolute Maximum Ratings of the Input Control Current 50mA, but according the characteristic the Input Control Current to Activate is 0.5mA. So is it safe to control the solid state relay from the MCU?

simulate this circuit – Schematic created using CircuitLab


texts: How to exit from an interrupt's loop for MSP430

texts:
I'm new to MSP430 and microcontrollers. Right now I'm learning interrupt routines and trying to write a program that changes the LED's state (OFF-ON-BLINK) by every press on P1.1 button. I have used the "switch-case" statement to achieve this and to control the switch statement's variable, I used a port interrupt. And for the blinking operation, I used a timer interrupt. Everything works as it should be. The program starts with the LED is off. One press on the button turns the LED on and if it's pressed once more, it starts to blink. And one more press, then the program should go to the initial position and turn the LED off. But there is a problem with the blink case.
When the LED starts to blink, the program stuck at the infinite loop where the timer get involved to toggle the LED state. Because of that, a press on the button has no effect, the LED continues to blink. Instead of this, the program should return back to Case 0 (see the code below)
Without the interrupts, (by usign polling etc.) my code works flawlessly. So in order to not overcrowd here, I won't post my code completely.
volatile unsigned int mode;

#pragma vector = port_vector_here
__interrupt void anotherNameHere (void) {
    __delay_cycles(1000);
    mode++;
    P1IFG &= ~BIT1;
}

#pragma vector = timer_vector_here
__interrupt void someNameHere (void) {
    P1OUT ^= BIT0;
    TA0CTL &= ~TAIFG;
}

int main(void) {

    /* Port settings, P1.0 to output, P1.1 to input etc.
     * Port Interrupt settings, IES, IRQ etc.
     * Timer settings, TA0CTL, SMCLK clock etc.
     * The configured as it should be, there is no problem.*/

    mode = 0;

    while (1) {

        if (mode > 2) {
            mode = 0;
        }

        switch (mode) {
           case 0: P1OUT &= ~BIT0;
                   break;
           case 1: P1OUT |= BIT0;
                   break;

           // Case 2 is the problematic part
           case 2: TA0CTL = TASSEL_2 + MC_1 + TACLR + TAIE;
                   TA0CCR0 = 50000;
                   TA0CTL &= ~TAIFG;
                   while(1) {}
           // Program stucks here (in while loop). When I debug it on CCS, I can see that a press on the button triggers the port interrupt but program returns to this line after completing the ISR. So it can't go out of Case 2.
                   break;
        }
    }
}

As I said in the comment part, the program stucks at the while loop that triggers the timer. As far as I know, I have to use an infinite loop to trigger a timer interrupt but I don't know how to skip over that infinite loop after triggering and executing commands in the Timer ISR.
How can I do this? How can I skip the infinite loop over to return to the initial position?


texts:
I am currently digging into some amplifier feedback analysis tools papers and literature. I found some "term" right at beginning of this topic that I don't quite understand. That is "Error equation of system/circuit". Simple feedback system incorporating this term looks like this:

At the beginning I thought of it as being a closed loop error or something in that direction, but this figure represents it as something else. So, system error (or E) is just a summed signal resulting from \$V_{IN}\$ signal and \$\beta\$ (or feedback path signal)?
Also, in paper I am currently learning from (published by Texas Instruments) gives these three equations for feedback system (incorporating E):
$$ V_{OUT} = EA $$ $$ E = V_{IN} - \beta V_{OUT} $$ $$ E = \frac {V_{IN}} {1+A\beta}$$
These equations tells me that System Error actually is a summing output. But why is it named "Error"? I first thought of it is being some miscalculation of fault term. And I probably wasn't the first that thought of it this way.


texts: RTC capacitor with long lifetime selection

texts:
In my design I am using for RTC (BQ32000) circuit, for which I have used a 0.33F capacitor and it's rated lifetime is 2000 Hrs.

But I need to select a capacitor with 5000 Hrs lifetime.

I haven't found a part with 0.33F and a lifetime of 5000 Hrs.

My question is:

Can we place two capacitors in parallel to increase lifetime?

Alternatively where and how can I select a capacitor with a lifetime of 5000 Hrs.


texts:
I've got a 1980 Honda XL 185s that has a 6 volt electrical system.  The headlight uses a 6V AC, 30 watt bulb powered from the generator.  The other lights (tail, blinkers) operate off of the 6 volt battery on 6 volt DC.  I'm attempting to increase the intensity of the headlight in order to make it safe enough to ride at night.  Presently the headlight is very dim anywhere near idle speed and just slightly dim at any other rpm.

I'm assuming that changing my 6V AC to 12V DC and then installing a manufactured 12V LED bulb will be easier than changing 6V AC to 6V DC and building my own 6V LED light.

I am also assuming that LED is my only option for a bulb, as I believe that I lose wattage in the step up or conversion of the power.  Electricity is not my strongest subject, as you can see.

I'm open to suggestions if I'm going about this all wrong.


texts:
I am designing a PCB for which I have made a POC on Arduino. On Arduino it is very simple to flash the program I have written via the IDE.
I have made a bare minimum schematic for the device which will be used in the first iteration of the product.
Now I ask this question in hopes of understanding.
Are there specific ports to which I should add the JTAG or something to flash the drivers onto the MCU?
Or will it come pre flashed which would just mean that I have to solder the MCU the correct way onto the PCB with the passive components connect the entire set-up to the Arduino IDE for example if I use the ATmega386 and it will show up?


texts: How to determine data transmission rate from an eye diagram?

texts:
I would like to know how to determine the data transmission rate from an eye diagram such as the one given below:

Would it be the reciprocal of the length of time from the start of the diagram to the end? In this case 3 micro seconds?


texts:
Scenario:

The main device is a bank of Li-Po 18650 batteries as the main power source. Sometimes the device will be plugged into AC power when needed for longer periods of time than what the battery packs will handle. Sometimes the device will not be plugged into AC power and will only use the battery packs as the power source. If connected to AC power and there is a power loss, the device should switch to the battery pack for power (UPS). The main device will power 2 other devices. One will be 5V @ approximately 800 milliamps. The second device will be 12V @ approximately 1 amp.

Questions:

What charging options are available for this many batteries in this configuration?
Is there a charging option that will keep the batteries balanced in this configuration?
Should I be using batteries with protection IC?
I found this board that sounds like it may work, but is there something similar that is cheaper or is there a better board for my setup? Open UPS
Is my layout ok? If not, what should I change?

Thanks!


texts: How to replace the rectangle(DIP) bridge rectifier with round one.

texts:
I want to make an AC dimmer and the circuit diagram from the instructables uses a bridge rectifier which is in DIP package and rectangle in shape and the rectifier which I have is round one, so how can I connect it in the circuit replacing the rectangular one?

instructable - http://www.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit/?ALLSTEPS


texts: I2C bus line over different layers in an arc

texts:
I have the following board design in mind:

It's a 4 layer, ~5cm diameter board where 10 slave PCB's will be soldered to it that are connected over the I2C bus. The trace line you see is roughly 8 cm in length. This bus has the clock going over the top layer and the data bus over the bottom layer, but I could always change that.

I could also route the traces over 1 layer but use via's to cross each other at the end points, if that makes sense.

As far as I can tell I'm not doing something that is against any I2C "rules" bus I'm also not that familiar with this sort of setup.

The end-point devices will add roughly 150-200 pF total load capacitance to the bus, excluding trace, solder joint and via capacitance. Which as far as I could tell is not a problem since it's far lower than 400 pF already. The bus will be running on 400 kHz.

What method of routing would be recommended here? Am I accidentally designing a radio receiver or worse, a transmitter?

edit: I forgot a case where both are routed on the top layer; Should I match the amount of vias used on both lines even if those vias aren't strictly needed?


texts: Confused on when to use RMS current or voltage in calculations (regarding rectifiers)

texts:
For question a, why is the power absorbed by the DC source :
P=Vo*Io

However, for the same exact question, the power absorbed in the resistor is
P  = (Irms)^2 * R

Hence when do we use RMS current/voltage in calculations and when do we use the average current/voltage in calculations?

As the RMS current includes the dc current and harmonics, would this not be used in calculating for the power absorbed by the dc source as that current is going through it (not just the dc value (i.e. average value)?


texts: Understanding crystal resonator symbols - which one is 24Mhz?

texts:
So, I'm in need of a 24MHz crystal to drive an AVR microcontroller. I've got some crystals that I've desoldered off some old, useless equipment. I've found three crystals that have '24' on their packaging:
HC 24.00
TXC 24.0NQ4L
24.00R4L

Google search turned out nothing, so I don't know whether any of these is 24MHz, or 2.4MHz, or some other values. From what I've managed to find, 24MHz have three 0's after the dot, but I couldn't find if 2.4MHz quartz ones have only two 0's or not.

I don't have a counter to measure how many ticks these can generate (too expensive :/ )

So, to expand the question a little bit, as I have more crystals in my collection: How to find out, without googling, looking only on the number on the package, how many Hz's are there?


texts: I2C support on non real time OS? How does it work?

texts:
I have my RPI3 (master) connected to an Arduino board (slave) via I2C-bus. It works, except that after 5 seconds running communication over I2C I already get exceptions about 'No acknowledge from Slave'.
Since I never really understood how I2C (as some sort of PWM) works on a non real time OS like Windows IoT, I thought lets start there. Find out how this works. But I can't find anything on that topic. Who can share me some more information on how this really works?
How does a non real time OS manages to support the I2C bus? What/Who is generating the SCL signal? What/who is reading the actual bytes on SDA? It can't be Windows IoT itself, so who is taking care of that? Why can I read bytes of the I2C bus? Who is buffering them for me? And how long are they buffered?
Really hope somebody who understands all this is willing to explain it.


texts: How to control this 72-LED light bar PCB

texts: I have two LED light bars from an old (manufactured January of 2000) Unisys check scanning machine. They apparently (based on the PCB's labels) have 72 LEDs. Most of the LEDs are green, but a few red ones are scattered among them for reasons unknown. The boards have 16-pin ribbon cables and metal pieces glued to the backs that seem to be heatsinks. Breaking the glue, there seems to be a line of thermal paste between the heatsink and the metal surface of the back of the PCB. The individual LEDs seem to be isolated from each other, not even sharing a common ground or power. There don't seem to be any flip-flops or microcontrollers on the board. I found only one pin on the ribbon cable that seemed to have any continuity to the LEDs. Below are pictures of these boards. Any ideas of how these could be driven with e.g. an Arduino, besides soldering to each LED? Thanks.


texts: Removing wires from a circuit board socket

texts:
I'm trying my hand at repairing old joysticks. I have this Dualshock Analog Controller (SCPH-1200 M) which came with my old PSX and it didn't work properly anymore. So I've decided to open it so I could repair it or at least learn something new in the process. I've examined the connections from the PSX to the joystick and they've all seemed fine, correct voltage and no short-circuits. When I plugged it I've found that it seems as there were some problems with the wires because if I held the josytick in some way, it would turn off. So I've concluded that the problem must be in a strangled section of the wire, so I've cut that section to later rejoin the cables. However it appears as I cut the wires coming from the circuit board too short and I cannot make a connection with the other side.

So my next idea was to remove those wires still attached to the circuit board and insert the other side directly into the holes of the white socket (I don't know its name). But I cannot seem to get the wires out - I've tried pulling them but they won't budge and I don't want to break any more stuff.

Do you know how can I remove these wires in a way that will allow me to insert new ones into them?


texts:
Mosfets are pretty  cool but they are either designed for circuit boards or for breadboard's. Is there a version of a mosfet that can be used for slightly thicker wires   than what would be usually found to a
mosfet(wires that can fit within a breadboard )

of course there are relays but thry dont have the switching speed  of a mosfet and they make a lot of noise

basically a mosfet that can be connected to wires that are the size that usally relays are connected to.


texts: How to switch power supply between two sensors

texts:
I have two ultrasonic sensors, when one sensor acts as a transmitter other acts a receiver and vice-versa.

How can I supply power for the 1st sensor for 20 microseconds  and switch the power source to the second sensor for 20 microseconds with a delay of 10 milliseconds in between. For example, the powering up sequence appears like the below.

Power to 1st sensor for 20 micro seconds
Switch off power for 10 milli seconds
Power to 2nd sensor for 20 micro seconds
Switch off power for 10 milliseconds
Repeat steps 1 to 4

Note: Only one sensor is powered at a time.

edit: Ultrasonic sensor electrical supply:
The exact voltage applied to transducer depends on signal attenuation through the medium, which I am yet to determine, for this reason I would like to have the flexibility to go up to 200V (if need be). Ultrasonic transducer typically require 30mA.

edit: Ultrasonic sensor operation summary:
I would like to apply 2MHz sine wave (or pulse) to one sensor and listen with the other and then switch the pulse and listening mode.

edit: Transducer spec.


texts: What RF protocol do wireless mouses and keyboards use to communicate?

texts: I'm designing a device which uses Bluetooth 4.0 (Low Energy) and I noticed how hard it is to achieve decent battery life, but the average mouse or keyboard lasts months/years on two AA batteries. I know they are not using Bluetooth, but a custom RF protocol, but what is so fundamently different to BLE that the consumption is so low?


texts:
I have problem setting the correct prescaler for a clock using an external 32k crystal. Not really a problem, but rather an unknown.

The correct prescaler for it should be 1/128

//32.768k/128=256; 256/256=1 second!!

But it's 1 second too slow, the right one seems to be 1/64, but why?

Here is the code:

ASSR |=1<<AS2;
TCNT2=0;
TCCR2B= ((1<< CS22) ); // 1/64
while (ASSR& ( (1<<TCN2UB) | (1<<TCR2BUB) ) );
TIMSK2 |= 1<< TOIE2;
sei();
//32.768k/128=256; 256/256=1 second!!

ISR(TIMER2_OVF_vect){ number++; }


texts: Good day, I am investigating the effects of varying stepping angles of a stepper motor on its power consumption. How does microstepping affect the power draw of stepper motors?


texts: Modifying and recertifying equipment for Explosive Atmospheres IEC 60079

texts:
I'm wondering what is involved in modifying equipment that has been certified for use in explosive atmospheres, such as ATEX Zone 1 or 2.

A couple of times recently at my work we have discussed integrating some technology into a processing facility with explosive atmospheres, but the certified equipment available COTS does not quite meet the specification we need.

Rather than develop a whole new product from scratch, I'm interested in knowing whether a company can take another company's product, swap out one part (in our case typically passive parts like the lens in a security camera or the lid of a junction box) for a part that we design, and have either our part or the combination of our part and the original equipment recertified.


texts: Somfy WT motor must not be driven by a solid-state relay or triac relay?

texts:
I came across this line in the installation / operating guidelines of a comfy (blinds) motor:

The drive must not be driven by a solid-state relay or triac relay.

Would there be any technical reason why this shouldn't be allowed? (see installation / operating guidelines)
These blind motors can detect when they are frozen or when there is an obstruction. Thus, when they feel resistance they won't try to move up/down.
Could it be that when I connect then to SSR this would interfere with this function?
I currently have it working with 100nF and 100 ohm snubbers over both directions of the motor. (These are 0.5A/230V reversible motors.)


texts:
I'm new to EE, and I am reading a text book which says:

  Phase describes the position of the waveform relative to time 0.

The a quiz asks What is the phase shift for a sine wave with the maximum amplitude at time zero, the answer is 90 degrees.

I'm confused, why it is not 0 degree?


texts:
I have a little bit of confusion on how the textbook author is determining the low frequency cutoffs for the 3 high pass filter components of this circuit:

For the capacitor Cs, he finds Zi which is after the capacitor, while treating Ce as a short. That makes sense because it would create the equivalent of a simple RC circuit and you can do your normal RC frequency analysis 1/(2*pi* Zi* Cs). Since Ce was shorted to ground, RE is shorted as well.

For the capacitor Ce, he finds the Thevenin resistance looking into the opened capacitor Ce, while also opening the capacitor Cs. Not to mention that he doesn't even look at the components that are connected to the collector...

Why is it when we are focused on the effects of capacitor Cs, we short capacitor Ce, and while we are focused on the effects of capacitor Ce, we open capacitor Cs?

This is from Boylestad Electronics Devices and Circuit Theory 11th Edition. This shows what he Cs, and it doesn't include the resistor RE, implying that Ce has been shorted. Note that little re is the base to emitter model resistors (approximated 26mV/IE) :

And this is what he does for capacitor Ce, and it implies that the Capacitor Cs is opened (for thevenin resistance, the voltage source would be shorted, and thus R1 and R2 would be shorted if not for the opening of Cs):


texts: How do I increase the height of a prop using a linear actuator and raspberry pi in under 35 dollars

texts:
For a competition, we need prop that will start at 2 feet, and rise (using a linear actuator or anything suggested) to at least 2.5 feet. We need this prop to be under 35 dollars (However we can spend up to 50) If we use the raspberry pi (which is already purchased) then how do we code it? How do we build? Ans lastly, how do we make it go off at a certain cue during the play?

Edit (more information): The keystone, the prop which is sitting on top of this contraption, is extremely light, less than 75 grams. I need this technical prop to extended like a telescope to raise the keystone up about 6 inches (or more)

I can reply to comment if you need more information


texts: Embedded Ethernet Solution w/ PoE+; SPI or MII?

texts:
I am currently undertaking my first hardware design attempt of an embedded Ethernet project w/ PoE+. I have experience working with embedded systems with Ethernet (mostly ARM M3/M4 processors with RMII interface to an external Ethernet PHY transceiver), but this is my first time actually doing the hardware design for an Ethernet capable device. I will also be writing the firmware for this project.

The purpose of this project is to create a downstream I/O board that communicates over TCP/IP to a controller board. Multiple downstream boards will be connected to one controller and report analog input statuses as well as execute output control commands from the controller. This downstream board will also have a basic web server that will be accessed via a web browser so a user can set configuration options.

In regards to the PoE+ feature, I will be using a third party module. I bring up the PoE+ in case this has any impact on the answer to my question, but I don't think it does.

I will be using an ARM Cortex processor so there are two paths to take for embedded Ethernet...

(1) ARM Cortex M3/M4 processor with internal MAC and (R)MII interface to external PHY. And then obviously the RJ45 and magnetics. This design I am familiar with and I know will guarantee satisfy my needs.

Or the other, less expensive option that I am considering...

(2) ARM M0+ processor with external 3-in-1 Ethernet controller interfaced with SPI. And then obviously the RJ45 and magnetics. For the SPI Ethernet controller, I am looking at the Microchip KSZ8851SNL.

Can anyone give me a reason NOT to go with the less expensive M0 route with external Ethernet controller. Ultimately, the only cost savings is about $4 or $5 for the M0 vs M4 processor setup because both the external PHY and external MAC+PHY controller are basically the same price. This however will be a mass produced design so any savings makes a difference as volume goes up.

I am mainly concerned with potential bottlenecks in performance using the SPI interface, however I am also thinking that with such minimal traffic requirements, I should be OK with the SPI interface. The datasheet for the KSZ8851SNL says it can run at a MAX SPI clock speed of 40MHz. I am not sure if I would need to run at the max or if a slower clock speed would do. And then what would the minimum clock speed of the M0 MCU be to get good performance (no lag loading pages etc)? I am looking at M0 options that have a max clock speed of 50-75 MHz.

Firmware wise, is MII or SPI more difficult to implement, or are they the same difficulty?

What are some network applications or requirements that would make SPI Ethernet controllers not cut it and I would need to use the MII with a more advanced processor?

Or in any of your humble opinions, is it worth it just to go for the M4 MII solution and have a future proof design that could also be re-used for new, upcoming hardware projects?

And lastly, in regards to PoE+, am I correct in thinking that PoE+ will be unaffected by SPI vs MII? Also would it be possible to design the board in a way that PoE+ population is optional? Basically can I offer a Ethernet OR a Ethernet with PoE+ assembly option with the same board design? I think the PoE+ is a parallel circuit so PoE+ should be able to be optional without effecting Ethernet data transmission.

Sorry for the long read and I appreciate any insights!


texts: 21v solar panel safety issues, and how to get a consistent 12v from it

texts:
We just bought a 50w 12v solar panel but it's actually getting 21v in full sun. Are there any safety issues we should take into consideration with this getting producing almost double what it's supposed to produce? And how can we get a consistent 12v from it?

Apologies for the newbie questions, I bought this for my 10 year old who likes to make electronics projects, so clearly there's a safety issue high in my mind and I'm far from an electronics expert, I just facilitate him with maker type projects as much as I can.

Here's the unit we bought.
https://www.banggood.com/50W-125V-Portable-Solar-Panel-Dual-USB-For-Car-RV-Battery-Charge-p-1506635.html

Thanks in advance.


texts: 2nd order passive low pass filter cutoff frequency with additional paralel resistor before the second capacitor

texts:
How we can calculate the transfer function and cutoff frequency for this type of filter?

For second order low pass filter the natural frequency is:

$$
f_n = \frac{1}{2\pi \sqrt{R_1 R_2 C_1 C_2}}
$$

damping factor is:

$$
\zeta = \frac{R_1 C_1 + R_1 C_2 + R_2 C_2}{2 \sqrt{R_1 R_2 C_1 C_2}}
$$

and the cutoff frequency is:

$$
f_c = f_n \sqrt{(1 − 2\zeta^2) + \sqrt{4\zeta^4 − 4\zeta^2 + 2}}.
$$

But for this type of filter I don't know the cutoff frequency formula.

simulate this circuit – Schematic created using CircuitLab


texts:
I was looking for a way to simulate a button pressing with an arduino in a black-box circuit I cannot modify (I have no GND), you can see it in my previous question and question.

Then, reading this post, I found the MAX4544:

It is not very clear to me how this IC differ from a relay that operates on two DC circuit. It has a control pin that can move a digital switch that open or close a circuit. Relay are defined from wikipedia as "A relay is an electrically operated switch".  Can anyone explain me in plain english please?


texts: Dirtbike ignition system: power consumption

texts:
I am trying to calculate the amount of power that a Honda CRF450 dirtbike's ignition system (ignition coil + spark plug) will consume. I'm not very familiar with ignition systems and the currents they involve - what is the easiest way to calculate this?

So far, I've found that the ignition coil's resistance is 0.1 - 0.3 \$\Omega\$, so the power (while charging the coil) is
$$
P_{active}
= \frac{V^2}{R}
= \frac{(12~V)^2}{0.1 \text{ to } 0.3~\Omega}
= 480~\text{to}~1440~W
$$
Then, if I pick an engine speed of 5000 RPM as an example, the time between sparks is
$$
T
= \frac{2\text{ revs/spark}}{(5000~\text{RPM}) / (60~\text{s}/\text{min})}
= 24~\text{ms}
$$
If I estimate the dwell time as 2 ms, then the average power consumption is
$$
P_{avg}
= \frac{2~\text{ms}}{24~\text{ms}} (480~W \text{ to } 1440~W)
= 40~\text{to}~120~W
$$
This is a huge range, and the higher end of the range sounds too large. Is there a more precise way to estimate this average power?


texts: How to calculate how much data a Core 2 duo E8 can write to the RAM per second?

texts: I'd like to know how exactly I could calculate how much data the Core 2 duo E8 can write to the RAM per second, given that it is not overclocked and the RAM is 333MHz-DDR3?


texts: What is a capacitor doing in this circuit?

texts:
I'm trying to understand some Op-Amp circuits given in a PDF by NI that shows a collection of useful opamp based circuit configurations.

I'm confused about this one that says Inverting amplifier with high input impedance. My doubt is what is the purpose of using a capacitor in the feedback loop of this circuit? Doesn't this circuit behave like an integrator with the capacitor in that position? How is it contributing to high input impedance? Please help!


texts:
I have a Uni-t UT210e clamp meter.
I noticed that when measuring AC current, the reading varies if I move the wire inside the clamp. The measured value displayed on the meter is higher when the wire is closer to the upper part of the clamp, and it is lower when the wire is right in the center of the clamp.
Is this happening because when moving the wire inside the clamp, the electromagnetic field around the wire is also moving, making the reading to vary?

Product manual: https://www.uni-trend.com/uploadfile/cloud/English%20manual/General%20Meters/UT210E%20English%20Manual.pdf
Product page: https://www.uni-trend.com/html/product/General_Meters/digitalclampmeters/UT210_Series/UT210E.html


texts: Creating a memory mapping to peripheral memory on STM boards

texts:
I am trying to find a way to load/execute code that is stored on an external SRAM chip without having to load it to the microcontroller internal memory. I'm not 100% sure of the name for what I'm trying to do but I think a memory mapping would work.

Reading the CMSIS driver for the board, this file (large file so no line numbers, but search for "#define APB1PERIPH_BASE" ) shows me that the peripherals of the boards, buses and such are already handled with memory mappings. So with this, I was thinking of mapping a region of code with an interrupt that would fire on memory accesses so I could fetch the data from the device using the SPI bus of my project's board. Doesn't need to be fast.

I thought also of using DMA but I'm similarly stumped.

I can't seem to find any definitive documentation either on creating a memory map or handling DMA with Peripheral->Device and Device->Peripheral transfers. I have a bunch of documentation on DMA internals but nothing with concrete information regarding memory maps.

I'm assuming that the STM32Cube CMSIS library has specific initialization code to setup the existing memory maps for the board but it must be using a precompiled driver because I can't see the source files, only headers.

I'm otherwise lost in the vastness of the ARM documentation and it is taking a long time to skim the documentation since I can't exactly name the thing I need in the same terms as in the documentation.

To keep it in simple terms, how can I create a memory map for an STM board using the STM32CubeF7 so I can transfer information to and from an external chip without loading/storing parts of the data in the main microcontroller memory.

Code examples would be great but I'm also looking for documentation for how it works in details.

EDIT 1 :

I have begun reading in more details the ARM Cortex M7 - Generic User Guide (page 28), and it in they mention a range of memory used for External RAM. What I am really looking for is how to wire up external RAM on my board to be used as external RAM.

I will keep analyzing the document but I have not seen specific documentation on using external SRAM chips as an ARM external RAM.

EDIT 2 :

I have found several questions on StackOverflow regarding programming STM boards with external memory chips. One of them was using FMC and it linked to a document by STM. Now I think I understand better what the current situation is and what the answers and comments on this question were saying.

Since I am using SPI right now, it would be impossible to map this directly to memory. Instead there are protocols like FMC and QuadSPI (or QSPI?) where the protocol and external chip specs can function with memory mapping. The linked document above (AN4761) shows examples on how to setup such functionality using SRAM, NAND and other chip types.

Reference material :

Board : STM32F756zg Nucleo https://www.st.com/en/evaluation-tools/nucleo-f756zg.html
Platform : STM32CubeF7 https://github.com/STMicroelectronics/STM32CubeF7
ARM M7 Generic User Guide http://infocenter.arm.com/help/topic/com.arm.doc.dui0646a/DUI0646A_cortex_m7_dgug.pdf
Using STM32L476/486 FSMC peripheral
to drive external memories https://www.st.com/content/ccc/resource/technical/document/application_note/3f/38/6c/cc/0b/7b/41/b7/DM00228015.pdf/files/DM00228015.pdf/jcr:content/translations/en.DM00228015.pdf


texts: Choosing the type of battery for a project

texts:
I am working on a machine which consists of 10 servos, and one microcontroller. The servos need to be on pretty much all the time for about 8 minutes. I am planning on using the ATmega16 to provide the signal to the servos. The servos I am using are the TGY-S4505B.

So the problem I am having is that there is no specification for the amount of power that servo draws, so I don't know what to design for.

Second, I don't know which type of battery works best for a project like this one. I can choose either NiMh or LiPo (the machine is mobile, so it must have a portable power source). I have the facility to charge both, I just don't know which type is better. The weight of the power source should be < 250g, but this is flexible. Any advice regarding the power setup for my project would be very helpful.


texts: Use 555 timer to output same interval as user presses a button

texts:
I was curious if such a circuit already exists tentatively using 555 timer chip (I know I can do this with a micro controller so please don't suggest that). Basically I need following functionality:
- by default output is low
- user presses a button for random time interval T
- once button is released the output goes high for same time period T then goes back to low.
Any ideas or circuits are highly appreciated.
Thanks !


texts:
In a conventional MOSFET, the body is doped silicon, but why is the body of FD-SOI FETs undoped?
I have come across this in multiple sources where they all state that it doesn't need to be doped because the body is very thin without explaining it. Why do we not need to dope it if the body is thin?


texts: Controlling power with Isolated DC-DC Converter remote on off vs Relay

texts:
I am designing a simple PCB with multiple DC to DC converters. One in particular is an isolated DC to DC converter with a remote on / off pin (to turn the converter on and off).

Currently i have in mind of connecting that converter to a general purpose or SS relay, controlled by arduino microcontroller chip, Atmega 328P. This will be used to open and close a mechanical/solenoid lock.

However, is it a good idea to skip the relay, and wire up the chip directly to the remote on/off of the converter? Or is it better to keep the relay? is the remote on/off pin of the converter isolated? Thanks.

Attached is the datasheet to the converter

http://docs-asia.electrocomponents.com/webdocs/0aca/0900766b80acafda.pdf


texts:
My workmate designed a 4 layer PCB with blind holes through 1 to 2, 1 to 3,  and 3 to 4 layers due to very confined space.
From my memory, it can't be manufactured.
But the pcb factory managed to make it and all blind vias are connected properly. The board is gold plated.
And it's very weird all blind vias have no visible holes. What you can see is a gold pad. My mate and I are pulling our hair out(not much left) to figure out how the pcb manufacture made it.

thanks


texts: Are there technical documents about microprocessor design by Jim Keller?

texts:
Jim Keller has worked leading various chip design projects at Intel, AMD, Apple and Tesla among other companies.

Does anybody know of any technical documents about microprocessor design written by him? I couldn’t find anything in IEEE Xplore and on the web all I could find were nontechnical interviews.

Many thanks in advance!


texts: Voltage, inductance & lightning in a length of wire

texts:
I initially got the idea after watching the famous Mike Holt video on grounding.

https://www.youtube.com/watch?time_continue=138&v=mpgAVE4UwFw

Mike warns that longer wires to ground rods can attract more energy. So I thought he meant the lightning voltage can increase after passing through the wire (it doesn't as one of the Answers has detailed at length).

I have many surge protection devices which protect many circuits so I wanted to know the mechanisms of it. And I tried to review the physics below:

Given the inductance for a given length of wire, the induced voltage along the length is given by:

$$v=L\frac{di}{dt}$$

So the greater the rate of change in current, the greater the induced voltage.

Hence the longer the wires. The greater is the surge voltage.

From here:


texts: Connectors for horizontal and vertical mount

texts:
Alright, I will try to formulate this as a non-shopping question... let's hope I can make it so.

I do have a board (which I can still change) which basically has 1 hole in each corner. This board, features some (user-accessible) connectors on one side (USB, ...) and now I'm looking for a way to fix this board to some mainboard.

I would like to be able to fix the board either horizontally or vertically, the required pin count is around 150 (including power and ground).

What I am looking for is a way to mount the board either way with as few additional components as possible. I also have the option to mount it to the casing in either direction but I'd rather have a version where the board is really tied to the mainboard (and to the casing).

The main question is now: Do you have another idea than using a 90° 1.27mm (0.05'') pin header?


texts:
i have recently been into atmega world after i heard it is much better than pic and it is my second tutorial about writing to LCD i wrote this program in atmel studio but it doesnt work i double checked the hardware and everything was okay, what is the problem??

#include <avr/io.h>
#include <util/delay.h>

void initLCD(void);
void writeChar(int);
void sendCommand(int);
void checkIfBusy(void);

int main()
{
    DDRC = 0xFF;
    DDRD = 0b11100000;
    initLCD();
    writeChar(70);
    while(1);
}

void checkIfBusy(){
    DDRC = 0;
    PORTD |= (1<<5);
    PORTD |= (0<<6);
    while(bit_is_set(PIND, 5)){
        PORTD |= (1 << 6);
        PORTD &= (0 << 6);
    }

    DDRC = 0xFF;
}

void sendCommand(int command){
    checkIfBusy();
    PORTD = 0;
    PORTC = command;
    PORTD = 0b10000000;
    PORTD = 0;
}

void initLCD(){
    //Clear Display
    sendCommand(1);
    //Function Set
    sendCommand(0b00111000);
    //Display Control
    sendCommand(0b00001100);
}
void writeChar(int character){
    checkIfBusy();
    PORTD = 0b01000000;
    //Write the character
    PORTC = character;
    PORTD = 0b11000000;
    PORTD = 0b01000000;
}

EDIT

I changed the code but it still doesn't work, what is the problem then?


texts: STM32F303VC I2C works in Debug mode only

texts:
I am interfacing HDC1000 with STM32F303VC. My I2C code works in Debugging mode only. Other Blinky and UART code works properly. Write works perfectly but, Read function code stuck here:

while(I2C_GetFlagStatus(HDC_I2C, I2C_ISR_RXNE) != SET)
{
    if((HDC_Timeout--) == 0)
        continue;
    return HDC_TIMEOUT_UserCallback();
}

I have selected correct CPU. I am using Coocox IDE. Please find my code and appreciate help. 10Kohms pull ups connected on both SDA and SCL lines.


texts:
I want to build a magstripe spoofer as a weekend project. I've seen others online do it using a steel shim wrapped in wire. This is only one coil. What can't understand is if cards have multiple tracks, how can one coil emulate all three tracks being swiped through. I thought I would need at least three thin steel strips each connected to a separate coil to spoof the 3 tracks found on a magstripe.

Are they somehow spoofing all three tracks through the one coil, or are they only building single track spoofers?

EDIT: Example of one http://hackaday.com/2008/08/04/magnetic-stripe-card-spoofer/


texts: How is definition of cutoff frequency consistent with KVL?

texts:
Low pass and high pass \$RC\$ filters have a cutoff frequency that is equal to
$$f_c=\frac{1}{2\pi RC}$$
This should be the frequency at which the ratio \$|V_{out}/V_{in}|\$ is equal to \$1/\sqrt{2}\$.

But how can I have at the same frequency the same ratio \$|V_{out}/V_{in}|\$  measuring \$V_{out}\$ firstly across capacitor and then across resistance?

KVL states that \$V_{in}=V_{resistance}+V_{capacitor}\$ at any time, but if at \$f_{c}\$ we have \$V_{resistance}=V_{capacitor}=(1/\sqrt{2}) \, V_{in}\$, then KVL would not be respected!

I'm surely missing something but I really can't see how the definition of cutoff frequency is consistent with KVL. Any help is highly appreciated


texts: What does "-1" and "x2" mean in a triangle symbol on a schematic?

texts: In this document, P. 5, "test circuit 1", there are triangle symbols with "-1" inside, and another one with "x2" inside. What do they mean?


texts: Relation between EM frequency/Intensity and voltage/current in a Circuit

texts:
Let's say I have a circuit connected to an antenna which listens for a certain frequency range. The antenna would generate an electric current. For an electromagnetic wave we have two main properties- Frequency (or wavelength) and Intensity.
I would like to know what property of EM corresponds to power (electricity). What I mean by this is that does frequency corresponds to voltage (i.e. higher frequency would generate higher voltage) and intensity corresponds to current(i.e. higher intensity would generate higher current), Or the other way around?
The same question for generating EM waves- More voltage would produce higher frequency and more current would produce more intense EM waves or the other way around?
Or am I thinking about it in a wrong way? I guess a different way to ask it would be -in a circuit for detecting EM waves, How would I measure the frequency and how would I measure intensity of that wave? Or while generating EM waves, how would I control the frequency and how would I control the intensity of the wave?


texts: Bjt amp with 2 voltage sources bias point

texts: I'm trying to bias the bjt amp with two voltage sources and make the collector of bjt at 0.5V to maximize output swing but the simulation give me too much different result, why? The collector current I choose - 5ma, R4 voltage drop - 1V, XMM1 shows 3.6V


texts: Driving LM386 with signal referenced to virtual ground

texts:
I'm working with a chip that outputs audio signals to headphones that are referenced to a virtual ground. Since I'm connecting the audio signal to a speaker instead of headphones, I'd like to implement a basic audio amplifier on the same board (sharing the same power source and ground).

I'm thinking of using an LM386 since they're a jellybean part.

However, I'm not sure how I would go about doing this. I've read the data sheet of the LM386 but the application notes don't really go into handling a virtual ground. The virtual ground is roughly 1.2V when referenced to actual ground and can source/sink about 150mA before it goes into short circuit protection mode.

All the circuits I've come across just ground both the inverting input of the amplifier and the input signal ground (why?). Obviously, if I did this, I would short the virtual ground to actual ground.

The schematic I am specifically referencing is the one below (source):

Is it just a simple matter of connecting the virtual signal ground (instead of actual ground) to the inverting input of the amplifier or would I have to look into building in a isolated power supply to power the LM386?


texts: Single phase neutral current & three-phase neutral current with respect to kirchhoff's law

texts:
In the below schematic, would be the sum of all current in the single phase neutral wires equal to the current in neutral wire going to the 3 phase main disconnect?

In theory, we know that if the 3 phases are equal, neutral current is zero. How would this be still true if each single phase neutral current is not zero (some loads would be on)?

What is the consideration ofKirchhoff's law in this context?

simulate this circuit – Schematic created using CircuitLab

Figure 1. Original schematic.

simulate this circuit

Figure 2. Schematic redrawn for OP to tidy up.


texts:
I am attempting to build the following amplifier

The amps used are MAR-8A+'s from minicircuits

C1, C2, C3, L1 - while these are available on the board they have not been placed

The filters are epcos saw filters with a Pass Band Frequency: 433MHz to 434.71MHz
I have designed and built the following PCB:

Upon building it the first few times I found the amps were blowing, I changed the resistor values and seem to have fixed this (schematic shows updated values).
Then I discovered it was oscillating, after fiddling with the physical power connections I found using pins and croc clips did not work and resorted to soldering wires on. This fixed the issue on the boards and subsequent ones up until now.
However recently they have started oscillating again at approx. 433MHz. First off it is just small oscillations, and then when the antenna is attached they multiply massively. I have noticed there is interference at 1.825 GHz and 945 MHz, this happens even when the board is not populated. As the board size is a quarter wavelength of the higher frequency I suspect this may have a lot to do with it.
I think I may also be needing the front end tuning that I have left out (due to not being able to make it accurate enough). Is there anything major I have missed? such as 50 ohm matching and termination?
Example Traces:

Many Thanks, let me know if I have missed any important info and I will add it.


texts: 3.3kV isolated heatsink for TO247 packages

texts:
I want to use some TO247 devices with an enclosure. In fact, I have to and there is no choice.

The enclosure has to withstand a dielectric strength test of 3.3kV for 10sec plus 6.6kV for 20ms. All devices together have power dissipation of 60W.

There is a method required to bring the heat out of the enclosure. If the isolation requirements were not so high, I would choose isolated thermal pads. Those I found can not fulfill this isolation requirement.

There are modules which are sufficiently isolated, but the devices are idle most of the time. This leads to storage issues.

Are there any solutions to bring the heat out of the enclosure, without violating the isolation requirements?

Even ideas are appreciated.

Edit - There are some questions I want to answer:

Dimensioning the heatsink is not the issue / obstacle. The issue is the dielectric strength between conducting parts (live parts) and the enclosure (dead metal).
I cannot influence the enclosure itself. It is the power distribution in a commercial vehicle.
The circuit is to protect and switch consumers, which are used a few times a year only. They might be switched-off for 9 months. Storage-effects for power modules occur when they are not used for a long time. The housing materials and in special encapsulates collect water over time. This leads to corrosion.


texts: Powering circuit directly from USB while charging li-ion battery side by side

texts:
What I am thinking of implementing:
1. I have remote monitoring circuit using gsm which senses electrical parameters like phase, power, ac supply etc. Now considering case of no ac supply available then also device should be able to send notifications. to achieve this I am thinking of running module on battery(3.7v Li-Ion).
2. As it is remote monitoring system, so battery will always be connected to supply for charging.

As per my knowledge one should avoide keeping battery connected for charging for all the time, it will reduce life of battery/overheating/overcharging are the parameters comes into the picture.

If I do like |Wall Adapter((ac-dc smps)|-->|battery
charger|-->|circuit| above mentioned parameters will participate.
If I do like Wall Adapter and battery to use in parallel using OR
ing with two diodes or using relay or using IC's like TPS2104/MAX
6326/TPS2110 etc then how can I take care of side by side battery charging?

I googled so many things to implement this but not found useful or may be I am not looking into right direction. I referred similer link 'http://forum.allaboutcircuits.com/threads/how-to-charge-a-battery-while-supplying-power-to-my-device.67530/' but no luck.
Even I looked into the data sheets and videos for li-ion charging circuits using MCP73831 or TP4056.

I am totally confused how to proceed further.
Is it a good idea to use |Wall Adapter((ac-dc smps)|-->|battery charger|-->|circuit| or
using Wall Adapter and battery in parallel and side by side charging battery. or to use wall adapter when supply is available and side by side charge battery so that I can use battery when power will be absent.

I know UPS works same way like it powers directly from supply all the time and charging battery side by side. At the time supply is interrupted it switched to the battery.
I am looking for simple solution, and I think this is a right forum I am looking for a solution. Thanks in advance...


texts: AC 230V Voltage Line Detection with sharp PC814 Switch Home Automation

texts:
I want to use home automation, so I am thinking of using INPUT to ESP8266 from PC814 bi-directional optocoupler for mains 230V physical switch.

Using this scheme I don't have to modify my house wiring and I will just connect physical wall switch output which was going to device will now go to PC814 optocoupler using some 100k resistor. Now PC814 output size NPN Switch will be connected to NODEMCU GPIO.

But I doubt that @ 50 Hz my input will be toggling every 20 ms. How can I avoid this toggling and by using mimimum components to get continuous signal until power is present on input of PC814?

Need experts advice if anyone had tried this scheme.


texts:
While writing software for stepper motor drivers and tinkering with AVR timers I've notice something interesting (to me at least).

Enabling and disabling pin output on AVR port has strange transient characteristics. I've expected to see crisp ON/OFF signals between 0 and 5V (Vcc), but what I saw was peak-to-peek voltages greater than 7V:

I'm not an expert and can't find any information about transient characteristics of AVR ports. So I can't understand the reasons behind this observation (is it normal or not) as well as possible consequences for "down the line" components (should I protect then from negative voltages?).

Some additional information:

I'm using atmega 328p microcontroller on Arduino board. The problem only manifest itself when I'm using probes in 10x mode (Rigol DS1052E) with bandwidth limit OFF.

The source code – https://gist.github.com/anonymous/5bdf6395416f4f497754290b5cbf7bb7


texts: Diode contribution in photo-diode's model

texts:
A common model used to represent a photo-diode is shown below:

It is then said that the current through Rsp (series resistance) is ip+id, where ip is the current proportional to the incident luminous flux and id the dark current (constant at a given temperature).

My question is: In the model it is always shown a diode Dp, that accounts for the rectifying effect of the junction. But it can't be an ideal diode, otherwise ip+idwould flow through it and not through Rps. What is the role of this diode in the model and how does it affect the current through Rsp?


texts:
I am unable to get any output on HO pin of IR2184 high side gate driver when I tried to drive a half H bridge.

Vcc is around 12-15V, input to IC is around 8V square wave, bootstrap capacitor voltage is observed to be around 8V. I m able to get LO pin output.


texts: Is Beryllium Oxide still used in the industry?

texts: Long ago it was used as a heat sink compound in (among other things) power transistors. It was very good at it's job. Unfortunately, it is horribly toxic. Is it still used anywhere an EE might come across it unaware?


texts: does the orientation of a choke in an LVDS application matter?

texts: I found the diagram below online while looking for information on the orientation of a choke I intend to use in an LVDS application. Does the orientation of the choke matter? The part I intend to use is the 744233121 by Wurth Elektronik. The chokes will be located right before the FPC connector on my PCB to which I connect the off-PCB display module.


texts: Does anyone know of a microcontroller/DSP with no clock speeds or any oscillators in excess of 1.705 MHz?

texts:
I am planning on making a simple electronic device which I might eventually try to market if it works out O.K. Before taking the plunge and trying to mass produce it, I would first try to sell a few on the internet to see if anyone even wants it.
It turns out, however, that to sell anything in the United States you need to pass FCC testing, or meet the criteria that makes it exempt. From what I hear FCC testing costs upward of $10,000, which I am not willing to put up right now. After much searching online for the official FCC documents (which were near impossible to find) it seems like one of the conditions is that that makes you exempt from FCC testing is if there is no oscillator or frequency in your circuit which is over 1.705 MHz (please let me know if this is wrong, I asked on here before finding the documents and everyone said it was 9 kHz and closed the thread).
Here is the link to the regulation:

Title 47: Telecommunication
PART 15—RADIO FREQUENCY DEVICES
Subpart B—Unintentional Radiators
§ 15.103   Exempted devices.
The following devices are subject only to the general conditions of operation in §§15.5 and 15.29 and are exempt from the specific technical standards and other requirements contained in this part. The operator of the exempted device shall be required to stop operating the device upon a finding by the Commission or its representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected. Although not mandatory, it is strongly recommended that the manufacturer of an exempted device endeavor to have the device meet the specific technical standards in this part.
...
(h) Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines or contain provisions for operation while connected to the AC power lines. Digital devices that include, or make provision for the use of, battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, do not fall under this exemption.

Does anyone know of a micro that has a clock speed and all oscillators lower than 1.705 MHz? I found some micros that have clock speeds of 1 MHz, but oscillators are 4 MHz. A clock speed over 500 kHz could probably work, but 1 MHz would be best!


texts:
I have a dual primary transformer out of an old amp and would like to use it for another project. I can't find a datasheet or a way that explains how to wire it for 220 operation. All the diagrams  that I have seen have only 4 input wires.

One post suggested connecting the black and white wires together but it then just overheats and shuts down.

Any help or info will be greatly appreciated. Thank you


texts: UART does not work properly after changing HSI to MSI in STM32L152

texts:
I am using STM32L152R8T6-A MCU. I use 3 UARTs in my project. UART buadrates are 9600 and 115200 bps.
Initially I set the clock source to HSI (16MHz) and everything worked fine. But then I decided to change the clock source to MSI (2.097 or 4.194 MHz). The program runs properly but it seems that UARTs miss some bytes, i.e. instead of getting 11 bytes, it gets the last 8 bytes.
I used the STM32CubeMX configurations and didn't change anything in initializations:
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_MSI;
  RCC_OscInitStruct.LSIState = RCC_LSI_ON;
  RCC_OscInitStruct.MSIState = RCC_MSI_ON;
  RCC_OscInitStruct.MSICalibrationValue = 0;
  RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_RTC;
  PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSI;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    Error_Handler();
  }
}

Has anyone any ideas?


texts: With so much radio signalling occurring simultaneously (TV, Cellphone, Radio, etc.), how does our atmosphere keep them separated and avoid disruption?

texts: I know this question has been asked before, but I still don’t completely understand. I understand that different stations are given different frequencies, but waves are able to interfere with each other if they meet. If they do, they produce a completely new wave. So how are we still able to single out one wave?


texts: Control 12V LED Strip with 5V from RaspberryPi or Arduino

texts:
I have a 12V RGB 5050 LED Strip with no controller and I cannot change the color without modifying the circuit. What I want to do is hook it up to my Raspberry Pi or Arduino and control the color and brightness through the terminal or serial communication.

I realize I can't simply wire the strip to the RPi GPIO pins or the Arduino as neither of them support a 12V output, but I believe I can use a transistor with a 12V input and control it with an RPi to change the LED strip values.

What transistor is recommended to go about doing this? Is there any other way I could achieve what I want without having to buy expensive parts (> $5)? Any other recommendation about anything would be helpful. Thanks.


texts: What considerations should I have for high-current power supplies?

texts:
I'm still pretty novice at electronics. I've recently been thinking of a project to make. The difference in this from my other projects is that for this I would need quite a bit of power. I'm use to using only a USB or battery powers supply. For this one though I think a PC power supply will be needed.

What precautions and considerations should I have when working with more amps(though the same amount of voltage)? If I hook an LED up to 5V, 500ma then it lights and works well. Will that be the same if I hook it up to 5V, 22A? What about for microcontrollers and other integrated circuits? Will they not be fried by the higher amperage?

If I do have something that does specify a max amperage rating, how do I decrease the amperage without affecting the voltage?


texts: Easiest / cheapest way to build a dc power supply in the 0 - 50V DC range?

texts:
I would like to build a small DC power supply (or find a cheap way) that allows me to get voltages in 0 - 50V DC range.

I had a look on ebay and some electronic shops but most supplies dont get higher than 12/24V DC. I know about variacs, but they are quite expensive and seem to output only alternating currents (someone can confirm?).

I dont need a lot of amps, something around 0.5A should be enough. What I'd like to do : I have a few fans/ small electric motors (running  9/12V) that i'd like to use and push to their limits. Best I was able to get from now is 24V DC, by using -12V / +12V from a old computer power supply.

I'm thinking about buying several 12V transformers and putting them in series but it seems a rather expensive and not reliable solution.


texts:
I've found this schematics:

(link)

On the page they say "It can boost by 14dB" (they mean that amplifier can boost bass by 14dB). But now I'm little confused - is the circuit configured to boost bass by 14dB or must I change something to boost it by 14dB ?

How can I calculate that?

Thanks :)


texts: I need to drive a DC motor @ 24V, 6A with a MOSFET. How can I sense the current that the motor is drawing with a microcontroller? I have to know when the motor is stalled.


texts: Hot & neutral have similar voltage to ground: Finding the problem Part 2

texts:
I accepted an answer to a similar question recently, but I now have additional information and have realized  that I need a more specific answer. I am nearly certain that my landlord will be unhappy about fixing this and try to claim there is no problem, and I would like to get as close as I can to figuring out what the real problem is, given that I have no training and no diagnostic tools beyond a multi-meter.

I have an APC battery backup and surge protector for my computer. It has a light, labeled "Building wiring fault." This light is on, and my computer will not start. So I bought a multi-meter (Etekcity MSR-C600).

Checking voltages at the outlet, I found the following:

Hot to neutral: 117.5
Hot to ground: 60.8
Neutral to ground: 55.9

I then checked the voltage several other outlets. All of them have the same hot to neutral voltage, but the hot to ground and neutral to ground vary considerably. For example, another socket had:

Hot to ground: 77.2
Neutral to ground: 36.5

This difference is puzzling given that all the outlets in my apartment are on a single circuit.

I unplugged every appliance in my apartment and retested every outlet. The results were exactly the same.

I have tested several outlets in two of the other three apartments in the building. The one on the same floor has several outlets that are just like the first one I tested above, and also some outlets with readings that are just what they should be. The apartment above me has the same problems as mine, but with a lower voltage to ground, about 15 to 20 volts, again from both the hot and the neutral.

I called PG&E and they sent a guy out. He tested the neutral against the ground at the meter and found no voltage. He also checked the wire connections at the building and found no problem.

Is this sufficient to tell me the most likely cause of the problem? I have been wracking my brains to try to postulate any electrical fault that would result in the pattern of voltages that I am seeing (and I have checked all these readings multiple times) and I have failed completely. It seems to me that a floating ground should have no voltage to the hot. If the ground was shorted to the hot, there should be no voltage to the hot and ~115 volts to the neutral. If shorted to the neutral, there should be 115 to the hot, and no voltage to the neutral.

The only pattern I can imagine that partially fits is if there is a short between the hot and the ground with a significant resistance in between. But that still does not account for the variation across outlets. And I also don't understand how this problem can affect multiple apartments when we are all on different meters, which we are. Finally, in my apartment the sum of the ground to neutral and the ground to hot is about equal to the hot to neutral. But in the apartment upstairs, the two voltages are still roughly equal, but sum to only about a fifth of the hot to neutral.

One thing that may be relevant: there is rigid conduit to an outlet in my kitchen, which extends past the outlet as flexible conduit and is then clamped to a pipe attached to my hot water heater. I have not yet checked whether there is a similar arrangement in the other apartments.

Given the above, how do I go about locating and identifying the actual wiring problem?


texts:
Please bear with me as I'm not too experienced with this.

I'm attempting to use an ADC to get readings from a photodiode. From what I understand, I should likely use an op-amp as the range of the current that will be provided by the photodiode is low (0-150 uA), and I can output a voltage required by my ADC (0-3.3V).

To get an idea of what I should be looking for, I used the site here

The above is what I produced from that site. However, I noticed on the second op-amp's (LT6202) datasheet, is that is has a minimum output current of 30mA. I was unable to find any reference to a maximum analog input current on the ADC's datasheet, and I wonder if this safe as an input, or should I go about finding different op-amps?

The selected photodiode (TEMD6010FX01)

The selected ADC (MAX1249)

The first op-amp (LTC6240HV)

The second op-amp (LT6202)


texts: AC Fan Wiring without knowing connection

texts:
I am trying to work out how to wire up this A/C motor. There are three wires and one of the wires (Wire 1) has a marking (Z2). Two of the wires have terminals (wire 1 & 2) and the third wire has been cut. Wire 2 also has a jumper wire which has also been cut.

After having looked at other fan wiring diagrams I see a lot of them refer to a capacitor but I am unsure whether this motor needs a capacitor and if it does what type and size of capacitor and where would it be wired with this motor.

My initial thoughts were that maybe there was a capacitor that went between the cut wires but without any markings or wiring diagram I am at a loss.


texts: Blown Capacitor and Bad Zener Diode in a Switching Power Circuit

texts:
We have got a few boards with failed power.  Some boards went alive after replacing a bad capacitor (swollen can).  Some boards went alive after replacing a zener diode (somehow shorted to ground I think.  My colleague threw it away so I do not know what condition it was at).  The said capacitor, C101, and zener diode, ZD1, are located in the lower left corner in the SMPS circuit shown below:

These two are neighbours so naturally I think they might fail due to the same source.  However, I have no clue why they failed.  Are there any design flaws in the circuit?  These are of small percentage of the boards out in the field, but I think it must be some design problem that triggers the problem intermittently.
Please also note that the capacitor that died in the field is rated 50V.

Here are some measurements at Vtrans, Vdiode, and Vzener.
Vtrans (with load at Panel_12V):

Vdiode (with load at Panel_12V):

Vzener (with load at Panel_12V):

Vtrans (without load at Panel_12V):

Vdiode (without load at Panel_12V):

Vzener (without load at Panel_12V):

The waveform before D120 looks like this during a typical load at Panel_12V (It looks terrible but I don't know if it's normal or not...):

Zoomed shot of the waveform before D120 looks like this during a typical load at Panel_12V:

The board also emits a hissing sound (rather loud, compared to other boards with switching power circuit I have seen).  I don't know if it's relevant to the cause of the bad capacitor and zener diode.  It is also a problem we want to solve though.

Please find the datasheet of the SMPS IC, FSDM0465RB, here:
https://www.fairchildsemi.com/datasheets/FS/FSDM0465RB.pdf


texts: TPS61169 LED driver not functioning properly

texts:
I recently designed a PCB for the TPS61169 LED driver. I used the sample layout from the datasheet, as it is a tiny SMD package and I couldn't breadboard it. I also followed the Typical Application in section 9.2.

However, it doesn't function properly.

Referring to 9.2 figure 4,

Supply voltage is 5.0V
CIN is 100uF tantalum + 0.1uF ceramic
L is 6.8uH inductor
D is an SS24 schottky diode
COUT is 2x 1uF ceramic
RSET is 2x 1.6R resistors in parallel (0.8R equivalent)

In testing, I have been trying to drive 3 green 3W LEDs in series.

Using the equation in 8.3.4, RSET = 204mV/250mA = 0.816R.

I calculated the inductor peak to peak current using equation 4 to be 3.84A, and the inductor peak current using equation 5 to be 2.17A. I don't think these are correct, however, as they seem high compared to the values in table 2 of the datasheet - Recommended Inductors.

Here is a schematic of the board:

A few notes: the two inductors and the two diodes are for different components - through hole and SMD - as I didn't know what components I had or could get at the time. Also, only two of the resistors R2 - R5 are populated.

Here is the board done in Eagle. Layout is per the datasheet.

Symtoms:

unexpectedly high current - my power supply reports a current of whatever its limit is set at, and will go up as high as I dare to set it. The current measured by my DMM in series with the LEDs is about 1/4th, and scales with the input current. I have no clue where the extra current is going.
voltage drop - along with the high current, my power supply goes into CC mode, and the voltage drops to 4.2V at 250mA. As I increase the current, the voltage decreases.
CTRL pin - the CTRL pin is used to dim the LEDs. However, feeding it a 20KHz square wave from my function generator has no effect on LED current. If I ground the CTRL pin, give it a voltage under 0.7V, or leave it floating, the LEDs will not light.

Here are some screenshots from my scope...

What I think is going wrong:

I had trouble soldering the TPS61169, as I stupidly didn't put thermals on the connected copper planes, therefore, I had to use excessive heat. I don't think I destroyed the TPS, as I made two of the boards, and they both display the same problems. It's less likely that I destroyed both.
more likely is that my inductor is saturating. Unfortunately, I don't have a different one yet, and the one I used was from aliexpress, and didn't have specs on current handling or saturation current.

As soon as I get a proper sized inductor, I will try that.

Am I correct in suspecting that the inductor is saturating? Are the symptoms consistent with a saturating inductor? Is there anything else that could be causing these problems that I am missing?

Thank you all for your help.


texts: how do i power a 12 v motor forward and reverse, using pulse wave modulation on reverse only?

texts: I am trying to build a device which uses a 6-12 v 8 amp dc motor controlled by a 2 channel rf relay, and powered by a 12 v battery. i need the motor to run forward and reverse, but in reverse i need the speed to be approx. 25% of the forward speed. i have a pwm module that i use to get the reduction, but i cannot get the pwm to work on reverse only, as i am getting pwm in both forward and reverse.i have destroyed 2 relays already trying to figure this out @ 10 bucks apiece. now i am thinking of wiring 1 relay hooked to the motor using straight polarity, and 1 relay hooked to the motor reverse polarity, with a diode on the positive side of each relay. i had the device working well without pwm, but reverse needed throttled down and when i added pwm things went to hell. am i looking at this the wrong way? can reverse speed reduction be achieved another way?  thanks


texts: How to find what circuitry is required for synthesis of following digital VLSI design problem?

texts:
My thoughts:
Here price of chocolate is increasing in Geometric progression with common ratio 2 and first term 1, so on nth day price of chocolate will be $T_{n}=2^{n-1}$\ irrespective of wheather child comes to buy it or not. But reward he gets is on basis of what net total sum of amount he had  child has spent on purchasing chocolate if it is divisible by 3 then he will get reward else not. He can skip some days too, if sick.
Suppose on day one child went to buy chocolate he spent 1 dollar, on second day he went again and spent 2 dollar, now total cumulative dollar spent is 3 dollar for first two days which is divisible by 3 , so child will get reward on second day itself.
Also if he go to shop on first day and 4th day respectively skipping second, and third day (due to being sick) then total amount spent on the chocolate upto 4th day will be  9 dollar(1dollar on first day+ 8dollar on 4th day) which again is divisible by 3.
Also he will get reward if he goes to buy chocolate on 2nd and 3rd day, skipping 1st and day,then his total spend upto 3rd day will be 6 dollars ,then he will  get reward on 3rd day as 6 is divisible by 3.
But i don't know how to generalise it, because there is no upper limit on number of days he went(like week/month/year anything). there are so many sample points. And instructor wants us to design Digital Sequential circuit for it. So, If possible give hints , or some of your thoughts. I would be very grateful.
Thanks in advance.


texts: How to access a Thermocouple signal in PC?

texts:
I'm looking for the way to access a thermocouple signal to use it in my own software.

I suppose that I have to place a data acquisition system (something like this https://www.dataq.com/data-acquisition/thermocouple/) between the thermocouple and the PC. The problem is to find a DAQ that shows the software calls to use it in my own code. I'm seeing that the main part of the DAQs have their own closed software and don't allow to see those calls.

Does anyone know a DAQ that allows this? Or another method to connect the thermocouple and use the signal?

Thanks in advance


texts: How can I make a device that will remotely disconnect an Ethernet port?

texts:
In some environments it can be helpful to have the ability to turn off an Ethernet port remotely. One case of this is in a public building where you might have a computer kiosk using the port once a week, but the rest of the time it is open for anyone to plug into and you don't want the port to be active to them. I can also see times in a corporate environment where you might want to be able to easily shut off a port if someone gets a virus.

I can handle all of the remote access parts of the project, but what can I do to actually disconnect the Ethernet port? Using relays on all of the lines seems like it would take up a lot of space and cost a good amount of money. Could I use a simple resistor and mosfet or transistor to pull the lines low? I want to make sure that I wont hurt the devices on either side.


texts: Calculating Power Dissipation in a Filter

texts:
Apologies in advance if my question seems too basic. I don't really know where to go from here.

I understand that power can be calculated as P = IV or P = V^2/R or P = I^2 x R. I think I'm not conceptually understanding how to actually use these formulas together to calculate power dissipation in a component.

For instance, I have this filter here. Its datasheet has a bunch of useful information, in particular rated voltage and rated current, 50Vdc and 15A respectively. I really don't believe I have the correct value for power dissipation if I just multiply the two values and get 750W. That seems far too much to be believable.

If I want to calculate how much power this filter dissipates, where can I find the correct values to calculate power dissipation in this component?


texts: How to convert KiCAD pcb file to HPGL/1 for use with old HP plotter?

texts:
I intend to use my HP 7475A for directly plotting etch-resistant ink onto a pcb. My problem is that, while KiCAD has an option for HPGL exports, it only generates HPGL/2 compatible files. Those make heavy use of things like the polygon mode or a variable line width, which are all not supported by my relatively dumb plotter.

I already thought about using a slicer for 3d printers, as the task of filling out shapes with a single-width stroke is the same. Unfortunately I can't find a way of converting the resulting G-code back to HPGL/1 code. I also tried to use Inkscape but only ended up with an outline of my traces without any infill.


texts:
Question 1: When one interrupt handler is executed, will it be interrupted if another interrupt with the same priority occurs?

Question 2: When one interrupt handler is executed, will it be interrupted if another interrupt with the lower priority occurs?

I used MSP430. The interrupts are always nested as long as GIE is enabled. The priority is only determine whose interrupt handler is executed first if there are a few interrupts occurred at the same time and pended (before they are responded).
But I don't find any answer for Cortex-M0 in its documents and google search.


texts: Pin identification of transistor and transformer from photo of module

texts:
From the photos of this driver board (no hands on testing, the photos are all I have to work with), how can one reason-out the E, B, and C functions of the pins (1,2,3) of the transistor, and the coil pairing of pins (4,5,6,7) on the transformer?

Assuming the trace from left side of D5 passes underneath D4, I am thinking 4 and 6 are the output coil since they lead fairly directly to LED terminals.

What is the significance if any of peculiar shape of the hole in the transistor? does it have a function and or indicate type?

(Disregard the red arrow)

The board is discussed in this other question.


texts:
I am having lots of trouble trying to understand  how the mosfet is triggered. The  text I read assumes the source of the NMOS connect to ground, while a positive voltage is applied at the gate.

Because the source is grounded, VGS (voltage between gate and the source) = VG (voltage of the gate). And then, it claims that because a higher VG accumulates positive charge at the surface of the gate, which repel the holes beneath the oxide layer, leaving the negative ions. So the charge density beneath the oxide layer is:

where Qd is the charge density at the depletion region created by applying VG.

Now this is my question: WHY does the term VGS instead of VG? If, say the source is not grounded, but connect to something like 0.01v, then VGS is not equal to VG, and to overcome VTH (threshold voltage), I didn't see why we need to consider the source voltage  To me, this doesn't make sense because repelling holes and creating the depletion region beneath the oxide layer has nothing to do with the voltage level at the source; only the gate voltage matters. Why VGS then?


texts: A question about the use of static reference resistor and balancing a floating source for an instrumentation amplifier

texts:
After reading an article for floating source wiring I decided to use the following scheme:

And following that in the below circuit I tried to make a more complete model for a floating source used with an instrumentation amplifier of a data acquisition board.

(right-click to view larger)

C_leakage is the leakage capacitance between earth modeled from this article. In my sim, in the middle of the cable there is a model for capacitive and inductive inference as you see. InAmp used in the sim is AD8221.

Following the article's recommendation I found out that in the sim, if I don't use any Rearth and connect AIGND directly to earth, the interference through the earth becomes very apparent; but higher the resistor Rearth the lower the that interference effect becomes.

On the other hand Rsource and Rreturn must be equal to get rid of the magnetic and capacitive interference through the cable.

I decided to use this STP configuration above instead of the configuration below:

It is because in this article if Im not wrong it recommends to use STP cable but not bias resistors between the source inputs ends to AIGND.

I also read in different articles that the shield better to be connected to the source's ground at the source side. So exactly like here.

My questions are:

1-) If I use the diagram in my LTspice sim above as a setup for many floating inputs, should I use a 10k to 10Meg resistor for Rearth? In sim Rearth gets rid of or reduces the interference through the earth. But in practice how does it actually do this and is that really needed? And what if I dont earth AIGND is that still neded?

2-)I have 5 type of DC outputting transducers. By STP I will guarantee the imaginary impedance balance but there might be source resistance unbalanced. Should I measure their source impedances seen by one and add the same source resistance to the source ground to make R1=R2 here? In other words should I make R1=R2 even though R1 source resistance is <100 Ohm?

3-) Would adding a series resistor to the source ground to balance the lines have any effect on cross talk during multiplexing?


texts: How can RPM be measured in 3 phase induction motor?

texts: I was thinking measuring magnetc flux from embedded magnets on the shaft via hall effect sensors but I am not sure. What would be the easiest way to measure speed of the rotor? I am talking about mechanical speed so frequency of the phase currents is not the way to do it.


texts: I want control 64 servo with arduino. I'm planning to use I2C based controller cards for control. I going to use SG90 and PCA9685. According to datasheet each servo consuming 550mA. Now I am going to choose a power supply. But which type of power supply is enough for me? Thanks


texts: Simplest way to control the speed of 4 identical fans

texts:
Hi, my computer has 4 fans in it running on 12v from the PSU.

How can I control their speed?

Maybe a potentiometer?


texts: How do you connect alternators in series?

texts:
What does the circuit diagram of three phase generators connected in series look like?
I know they are usually connected in parallel for obvious reasons.


texts: Need help to calculate time in an RC circuit with a AD converter and a multiplexer!

texts:
I am not sure how to describe this in english, but i will give it a try.

I have a unipolar AD converter with Vref=3.3 V and 12 bits. The digital output is d=969 so that gives me the Vin=780.879 mV.

I also know that the LSB=805.664 µV.

So now a analog multiplexer (with inner resistance) is connected to the ADC. It looks like the image shows.

Before the AC starts i want the voltage to reach 1/4 of the LSB value. C is uncharged and the multiplexer pluggs in a sender that gives the voltage 0-Vref and has a inner resistance of 7 kΩ.

I need to calculate the time to reach ¼ LSB in the worst case scenario if RMUX = 3 kΩ, C = 12 pF . Can someone help me with that?

I have a formula i found but i don't know if it is correct, and i am not completely sure on which U values to put in: Uc=Uc∞-(Uc∞-Uc0)e^-t/RC

Thanks!


texts: Is this question wrong? possible to calculate gain without beta or Ic given?

texts: How to proceed with this question? I can't think from where to start.


texts:
I'm gonna start to excuse me for my bad soldering/layout, but this is .

I am using a mosfets (IRF520) to which I have connected a 12V power source to the drain and source. They are connected up to a led strip. The gate I am controlling with my arduino MKR1000 (3.3v outputs). The circuit does exactly what I expect from it except for one thing: the leds dont burn as bright as I would expect. When I connect a 12v input to the gate they do burn as bright as I expect. My guess is that it is because the voltage I put on the gate is too low, and the mosfets are acting as a variable resistance.

The store I bought them though tells me that they should burn as bright with 3.3v as with 12v. Am I doing something wrong, or am I using the wrong mosfets?

Schematic I used:

Link to datasheet:
https://www.vishay.com/docs/91017/91017.pdf


texts: Writing long PLC code routine without scan-time over-run

texts:
I wonder if is a problem with response time of PLC in some cases?
If so, what is the case?  How to designer it solves ? For example calculation are to complex, the next step must be calculated in 200 ms but it take 600 ms.

[Clarification:] PLCs typically execute their logic in a repeating scan sequence as follows:

Read the inputs.
Execute the logic.
Write the outputs.

The result is usually a predictable scan rate.

Sometimes some complex logic has to be executed and this can extend the scan time and interfere with the performance of the process as the response time is extended.

How does the designer execute time-consuming logic without extending scan-time excessively?

[/Clarification]

Sorry for My English.


texts:
I have a MAL213836109E3 axial capacitor.  There's a stripe on one side of the capacitor, but it isn't a tantalum capacitor.  Does it indicate + or - in this case?
This is the DigiKey link to it:  https://www.digikey.com/en/products/detail/vishay-beyschlag-draloric-bc-components/MAL213836109E3/263338


texts: Bluetooth headphones pair to some unknown device. Can't pair to my source

texts:
Apparently, there's some BlueTooth source in the building with a policy of "pair to everything". I am NOT able to find that and snap its neck off!

For the headphones:

I use the "restart" procedure, which is to connect the headphones to a USB source for recharging
I then turn them on and they start blinking that they are diconnected, cool
BT at the source is turned on and now I am pairing
Headphones now show that they are paired, but my source says it can't pair to them!

(I can't do something like start the source pairing before I start the headphones, this just doesn't work. Normally, the headphones need to be "on" and in "disconnected" mode for about 10 seconds before they let a source pair with them. Of course, for this super-power source, they connect immediately)


texts: interfacing microcontroller with a high inductive load

texts: I have a confusion about interfacing microcontroller with an inductive load , if for example i have a switch lets say a BJT which is turned on and off through a microntroller pin to turn on an off an inductive load (lets say a motor or relay) i would be needing a free wheeling diode for protection because energy stored in the inductor will try to move current through the circuit but what would I have to do for big currents , use a schottky diode or do i have to use some other component with it ?