texts: Safety switch "breaking capacity" vs. voltage

texts:
In the context of safety switch rating (fuses, circuit breakers, etc.), the concept of breaking capacity refers to the maximum electric current which can be safely interrupted by a tripping safety switch, i.e. interrupted without the formation of an electric arc. The article Breaking capacity on Wikipedia states that

  The current breaking capacity corresponds to a certain voltage, so an electrical apparatus may have more than one breaking capacity current, according to the actual operating voltage.

I am curious as to what a breaking capacity vs. operating voltage plot would look like, but I haven't been able to find one. I suspect breaking capacity is negatively correlated with open circuit voltage, but that is just a guess.

For my question, consider the following case:

Let there be a circuit with a switch, where \$A\$ and \$B\$ denote the contactors of the switch. A voltage of \$U_a\$ is the maximum voltage between \$A\$ and \$B\$ such that no electric arc can form between them when the switch is open.

If the switch is originally open, a voltage of \$U_a\$ between \$A\$ and \$B\$ will not generate an arc between \$A\$ and \$B\$.

If the switch is originally closed and a current of \$I_b\$ flows, when suddenly the switch is opened, is the voltage \$U_a\$ now enough to generate an arc between \$A\$ and \$B\$?

If the flow of current reduces the voltage required for electric arc formation in the example above, why does it happen? Does it have to do with momentum of the charge carriers?

I hope my question is clear enough for being answered. If not, please point out where it is unclear.


texts:
I’m headed back to the CNF (http://www.cnf.cornell.edu/) shortly.
It’s a user clean room facility for semiconductor processing.
My goal is to make some very simple samples, for use in student teaching labs.
  I’ll take Ge and Si wafers
and sputter or evaporate metal on them.  The first task is to make ohmic
contacts for transport measurements.  (Hall effect and conductivity.)
I then had the brilliant (or silly) idea of also making non-ohmic (Schottky)
contacts to the sample.  One can then do CV measurements and get a third
measure of the doping density.  As well as having a built in diode..
it could be used as a temperature sensor.

My first trip there was wildly successful.
I sputtered two dots of titanium followed by aluminum on the samples
and then evaporated two dots of Al alone.

Table of results:
Sample           Ti/Al             Al only
Si-p           diode w/anneal      ohmic contact
Si-n            ohmic              diode w/anneal
Si-int.         ohmic             (unsure.. I broke it.)
Ge-n            ohmic              ohmic
Ge-int          ohmic              some diode behavior.
                                   Poor adhesion.

Sample I-V was done back in Buf. And then samples were annealed up to
300C on a hot plate.  Except for the intrinsic Ge the metal adhesion was good.
(They all pasted the scotch tape test.)
I must say that titanium looks to be a nice metal for contacts.

OK after that intro some questions.

I feel I’m reinventing the wheel, I’ve done a lot of on-line and library reading
but there is not very much practical advice for making contacts to semiconductors.
(There is a lot of theory.)  I keep wondering if there is some old Bell labs technical
document that could help me.  If anyone knows of anything like that I hope you’ll share.

I still would like to make a diode with Ge.  Any ideas of a metal to try?
Probing the Ge samples with Gold pogo pins it did look like the gold made a rectifying
contact.  But I’m guessing gold won’t stick very well.  I thought I’d try Indium.

The Ti/Al metal on Si developed a black layer around the edges.
I assume this is oxidation of the Al.
And I’m going to try Gold for the top layer.

Finally, are there any other things/ experiments
I could make/try by putting down metal on semiconductors?
I should add that the diodes displayed a nice photo-response.

Thanks for reading this rather long question.

Edit: adding Link to I-V curves (I is vertical (y) axis, chan. 2, with gain shown.)
https://www.dropbox.com/sh/v7roajd0dumt1o4/AABU1luSZvJFH2IND6SkRnnWa?dl=0
Excuse the messy lab pictures, I've now got pogo sticks on my "probe station."


texts: 230V switch controlled by Arduino Uno (Atmega 328)

texts:
I need to realize a switch for an electric motor whose power supply is at 230V.

That switch must be controlled by Arduino with a certain square wave signal. If the voltage was lower, I'd build a simple circuit with transistors used as switch. But I think it may be an hazard with 230V.

Which component can I use? I heard about solid state relay, but I do not know how to choose them and if they are right for this aim.


texts: Components in the circuit based on admittance (in complex form)

texts:
My Question
I have an admittance in complex form for a circuit.
Is it possible to know what components are in the circuit based on the admittance?
How do I calculate it?


texts:
I’m using an Adafruit micro-USB Charger connected to a standard 850mAh LiPo battery. I would like to know if it’s safe to charge the battery while also using it. The circuit that the BATT and GND pins are connected to will draw about 60-150mA. The charge current is 500mA.

From what I can tell, the charger board does not implement the MCP73831’s load sharing feature. I believe this means any load will be paid out by the charge current. Is this okay? In testing, I can see so far that the DONE light never illuminates (battery gets to about 4.18V and as soon as I disconnect BATT from the remainder of the circuit, it illuminates).

Schematic, etc: https://learn.adafruit.com/adafruit-microlipo-and-minilipo-battery-chargers/downloads


texts:
I have a circuit like the one shown below. To make the schematic easier to read, I only show 2 FETs in parallel. I actually have 8 identical FETs in parallel. The HT0440 is a high-side N-channel FET driver. It's controlled by a digital signal from an MCU.

simulate this circuit – Schematic created using CircuitLab

Power is not switched on and off rapidly in this application, but I am still concerned about the instantaneous heating in the FETs when power is turned off. Particularly when RLoad is small and the current is high prior to being switched off. I probed the source pins of the FETs during a switch-off event and observed this curve:

It takes about 250ms for the FETs to fully turn off. RLoad in this case was 10 Ohm. I did some calculations in a spreadsheet and came up with this curve for power-vs-time in the MOSFETs during the switch-off event:

Integrating under the curve, I get about 17Ws (Watt-seconds). That's the total accumulated power loss among all 8 MOSFETs. There's a graph in the MOSFET's datasheet that shows the maximum single pulse power dissipation as a function of pulse width.

Now, I know that MOSFETs in parallel will work "nicely" with each other to share the total current because of their PTC nature. However, I don't know if it's safe to assume they will continue to work nicely together during a switch-off event. In other words, as the gate pins are being driven low, is there some property of MOSFETs that would cause one single MOSFET to end up taking the brunt of the switching power dissipation? Or will they all share the total power dissipation equally?


texts: Precautions needed to parallel P-MOSFETs as high side load switches?

texts:
I plan to use P-MOSFETs (SI7463) as high side load switches, with a slight soft-start (to be tested and tweaked after PCBs are made).

I'd like to parallel them in order to make the equivalent Rds-on lower, but I can't find simple straightforward recommendations on how to do so.

I'd imagine that due to their positive temperature coefficient they will "automatically" share current "equally", however, I've seen some parallel applications in which a small series resistor is recommended (which defeats the purpose for me).

Does a simple implementation like this lack anything?

The load are LED Panels, up to 8A total. Switching frequency is maybe once or twice a day (10uHz? :D ).

With an advertised Rds-on of ~0.01R and 8A, power dissipation would be  0.6W. Junction to ambient on a 1x1" FR-4 board is about 52C/W typical, so 31C temp rise.

Adding an extra FET would be an easy and cheap way of halving the power dissipation and enlarging the effective dissipation area.

simulate this circuit – Schematic created using CircuitLab

Follow up:

I ended up following Trevors advice and using a single more expensive device with lower Rds-on (BSC030P03NS3). To the touch, it feels like the traces around the device heat up more than the device itself (4 layers, 10mm wide, 35um thickness on external and 17um on internal). (They are probably the same temperature and the copper feels hotter than the plastic). It works fine without heatsinks cause the avg temp over time is much lower than the peak (8 Amps).


texts: Problem switching boost converter using 2N2222, which turns on an RF transmitter

texts:
I am using a 2N2222 transistor to switch on and off the input supply of boost converter. The output of boost converter is powering my RF transmitter and voltage regulator which is used to provide 5V to four addressable LEDs.

simulate this circuit – Schematic created using CircuitLab
My controller works on 3.3V logic level, so the transistor's base is operated at 3.3V. The output of the boost converter is set to 12 volts.
My problem is I could not get a stable voltage at the boost converter output.
My transmitter does not work properly. It is missing data. (It works just fine when I don't use a transistor to switch the supply.)
Another problem is around 0.7 volt is dropping across the transistor, which is not suitable while using 3.7 volt Li-Ion cell as it further reduces the input voltage to the boost converter which is used to boost the voltage to 12 volts.
The LEDs I am using are fluctuating when data is transmitted.
My first guess was that it is due to the current capacity of transistor, so I switched to a TIP122 which is a Darlington pair transistor. Thr problem is still there.
My aim is to reduce power consumption when the RF transmitter is not used so I want to cut off power from rest circuitry.
What circuitry or component or method I should be using to switch the power supply without affecting the transmitted data?


texts: 24V, 200W DC motor Control using N channel H bridge

texts:
I am trying to build a controller for a brushed DC motor.
AIM:-

To Run the motor at continuous load of about 8A.
Rotate motor in both the directions i.e. forward and reverse.
Control the speed of motor, possibly using an MCU that will feed the PWM to MOSFET gates via a drive circuit.

ISSUES:-

Choice of MOSFETs
Drive circuit for the bridge using N-Channel MOSFETs for both high side and low side.
I want to drive the MOSFETs using discrete components only and not using a gate drive IC.

I tried the attached circuit, however, the upper MOSFETS get heated to about 75 degree celsius in just few minutes, if I can make some changes in this and make this work please let me know or if I need to use a different circuit altogether.
Since the MOSFETs were heating I also tried to use the STP55N (55A) MOSFETs but gave the same response.
IN_1 and IN_2 are PWM inputs for forward or reverse condition.
INP will be a 24Volt supply.
PS : Is this the issue with the drive logic that I am using? What can I do for that?


texts: Checking my understanding of "branch in parallel current" warning

texts:
A datasheet for a power connector I was looking at tonight has this warning:

  Note:

  Do not branch in parallel current which exceeds the rated current.  If
  branched in parallel, current imbalance or other problems may develop.
  If it is absolutely necessary to branch such a large current in
  parallel, be sure to use contacts made of phosphor bronze.  Design the
  circuits without causing imbalance and provide an extra margin for
  each circuit.

The connector has a current rating of 10A and has crimp pins that support 16AWG wire so presumably each pin of the connector can support 10A.

I read the language "do not branch in parallel current that exceeds the rated current" to mean that one should not draw more than 10A total across some number n of pins all hooked to the same power source.

I'm guessing it's a safety feature in case one wire of a parallel group were to break so that the remaining wires don't immediately have to take on a much higher current but I would like to check my understanding here.

Am I interpreting this correctly?


texts: Is voltage divider formula stated wrong everywhere?

texts:
Sample voltage divider circuit:

simulate this circuit – Schematic created using CircuitLab

In this circuit, \$Vout\$ is, by Ohm's Law: $$ Vin * \frac{R2}{R1+R2} $$

But this circuit, by itself is pretty much useless right? That is: If we don't connect \$Vout\$ to a load, then there is no reason to divide a voltage. So a better representation might be:

simulate this circuit

But in this circuit, \$Vout\$ is, by Ohm's Law:

$$ Vin * \frac{Rload*R2}{R1*R2+Rload*(R1+R2)} $$

So why isn't a voltage divider circuit formula stated as the second version, rather than the first one?


texts:
Noob question I'm sure, but I wonder if there's a simple device that will switch off current on one circuit when it senses current on another.
I'm replacing OEM switches in my car. Subaru's design is to power a backlight continuously, and power another light if the system is on. For example, the 'cruise' button backlight is on continuously, and the cruise computer powers a separate light if the system is turned on. The billet buttons I'm looking at have RGB backlighting with a common wire, i.e. four total leads to power the backlight. I'd like to connect the red lead to the continuous backlight power and the green lead to the system-activated power. However the product of this will be red/yellow instead of red/green as far as I understand it. (This is written as 'system-off-color'/'system-on-color'.) I would like to add some relay-like component to the circuit such that when the system-on light is powered, the continuous backlight circuit will open, resulting in red/green.


texts:
I made a PCB with two Arduino Pro Micro 5V on it as a control system for a machine. The PCB is powered by a 24VDC PSU and a part of that 24 VDC goes to a R-78C12-1.0 DC-DC converter. That gives 12VDC 1A to the RAW pin of the pro micro.

It worked perfectly for few weeks but one day the Arduinos randomly fried itself when I powered the machine/PSU on. The voltage regulator was the part that was damaged. I couldn’t figure out what caused it.

I used a spare PCB and since the second Arduino isn’t important/needed for now, I only used the one Arduino. I also placed a polarized capacitor between the 12VDC DC-DC Converter and GND. I did this thinking it will stabilize the 12 VDC going into the RAW pin.  Now when I turn it on it works sometimes, other times the HR-SC04 Sensor and LCD screen don’t work and I noticed the VCC pin on the Arduino dropped to 2.8V. When it was having this problem, I tried to connect a micro-USB cable in and that caused the Arduino to fry again. It was the voltage regulator again that was burned and blackened.

I looked online to see if others had similar problem and couldn’t get an answer. The only option I can see right now is to get a DC-DC Converter that output 6.5V instead of 12. Attached a screenshot of the schematics I’ve drawn on the easyEDA software.

Would anyone have any idea what caused this fry up?

Schematic of the PCB

The PCB where the Arduino Pro Micros burned out

Close up of the voltage regulator. It says "4BMD" on it before it was blackened.

The PCB mounted on the machine.There is plastic spacers so there isn't electrical contact between the sheet metal and the PCB.


texts: Modified laptop power supply pulses - voltage too low?

texts:
I have modified a laptop switching power supply by changing the voltage divider (as seems to be the standard way to do so), using a potentiometer so I could dial in exactly the right voltage - in my case, a hair under 5 volts.

Normally, it makes the typical high-pitched hum, almost inaudible with the case on. As I turned the pot to lower the voltage, that hum got lower and more click-y, finally reaching a couple clicks per second as I homed in on ~5V. Obviously the sound of the switching power supply acting as it's named. But hey, multimeter said it was fine, right?

Upon hooking up a string of 5-volt RGB LEDs (~1A draw initially, all blue), I discovered that they pulse in time with that clicking. That's the issue I hope to understand. I've tried changing the output buffer capacitors to something 50% beefier, but absolutely no change. I thought maybe it could just be the response lag of the feedback circuit, but half a second is practically eons to electronics... at least in the digital circuits I'm used to.

Is this a normal/expected issue? Google doesn't seem to think anyone's even tried to drop a laptop supply this low, let alone any reports of problems.


texts:
I've found this marking on an old transformer

This transformer has input voltage selection for the primary and 34v centre tapped secondary, it is used for an old power supply.

My question is: what further information are given by this marking ? (links to the general rules are welcome as well)


texts:
I've learned recently that lower frequency radio waves travel farther and have better object penetration than their higher frequency counterparts.

With this in mind, I was pondering about the two-way radios we use on the ship I work on.

Most everyone uses VHF radios for communication in the maritime industry, but we've always had a hard time sending or receiving transmissions when we are below deck with any crew above. We ended up ordering UHF radios and these radios fixed the problem, they work great.

Why is it that these higher frequency radios penetrate better than the lower frequency radios if lower frequencies are supposed to penetrate better?


texts: Effect of cable capacitance to low frequency analog voltage signal transmission

texts:
Regarding sending a low freq. (<150Hz) analog voltage signal with CAT6 STP cable I have heard that: if the frequencies down the cable will be low, there may be an issue with it driving a capacitive load (the cable inner to screen capacitance) in which case a buffer amplifier may be needed at the sensor end.

1-) Why might the capacitance of the cable be a problem for low freq. analog voltage signal transmission? Can this be explained theoretically or with a circuit model?

2-) How come a buffer can fix this?


texts: Does this look like a correct Bandpass filter?

texts:
A project task assigned me to make a simple series RLC bandpass filter with values B = 73kHz & freq center = 4.8MHz known.

I use equations B=R/L  and  fc=1/(2pisqrt(LC)) to get the RLC values.

Is the graph what I should expect? The center frequency lines up properly.. and I think the bandwidth is okay because it is so small (73kHz).

/edit
Here is a more zoomed-in version of my graph


texts:
just a short question while reading the Datasheet. What is the meaning of the Capacitors in the second line (marked red).
Do I need both (100nF AND 4.7uF) connected each of the Supply?

Datasheet Link


texts: Reverse voltage circuit protection using an N-channel MOSFET

texts:
I am currently working on a drive for a DC motor and I want to add a reverse voltage protection on my circuit so it doesn't fry in the case of an inverted power supply. I've read many tutorials on that subject and I chose a protection using an enhancement mode N-channel MOSFET.

My circuit will be powered with a 24V source and most of the N-channel MOSFETs only have a max Vgs of +/- 20V which is a problem because in a case of a reverse voltage, Vgs will be -24V, over the absolute maximum characteristics for most MOSFETs.

My question is this: Can I use a resistor voltage divider to create a lower voltage at the gate, thus having a Vgs that is within the specifications?

Something like this:

I have no background whatsoever with MOSFETs so I am wondering if that will cause any problems.


texts: How does a fuse blow at its current rating, regardless of voltage?

texts:
I know from reading elsewhere that it's safe to use a fuse with a higher voltage rating when replacing one, so long as the current rating and reaction speed is the same.

For example, if a fuse is rated 125V 1A, then a 250V 1A can be used.

Let's say these two example fuses have a resistance of 0.153 and 0.237 ohms, respectively. (Littelfuse 5x20mm fast-action cartridge type.)

Is it therefore correct to say that the 125V 1A fuse in theory should blow at 153 mW and the 250V 1A fuse blows at 237 mW? (Using \$P = I^2R\$)


texts: What is purpose of an Undervoltage Sensing Circuit?

texts: I am wondering what is the purpose of an IC such as the MC34064. Is it just to ensure a reset of microcontrollers upon power up or are there other reasons? I used to make a simple transistor switching circuit (with RC) for resetting microcontrollers in the old days. I am asking because the name of this IC is "undervoltage sensing" and not "reset IC" or something similar.


texts: Connector Current Carrying Capacity (circuits in paralllel)

texts:
We have a production application where nominal current is  285mA and the connectors is only rated for 300mA capacity!

There are two additional circuits available so we may parallel two circuits for power and return.

How can we re-rate the connector current? What is the applicable standard? Any ideas?


texts: test 0.5A inductive load through switch circuit

texts: We are a switch component manufacturer and typically run life cycle tests with resistive loads through our switch circuits.  Can someone recommend a circuit diagram set up to test an inductive load through same circuits?  Typical ratings 2.0A resistive, 0.5A inductive.


texts: Question about MOSFET CS amplifier simulation

texts:
This is the project statement:

I have designed the circuit and it worked well. This is the circuit:

It contains 3 voltmeters and 1 ammeter as shown.

This is a plot for vin = vG, vout = vD, vS and iDS:

The question is:
When I increase vin from +/- 100 mV to +/- 1 V, the plot becomes like this:

1- Why does vout become almost straight line when vin reaches its maximum values?

2- Why does vout become a straight line when `vin reaches its minimum values?

My guesses:

1- Because the MOSFET exits from the saturation region to the triode region.

2- Because the MOSFET becomes off.

I know my guesses -if they're correct- are brief and not enough (especially 1), so please provide me with detailed explanation about the reasons of the two cases


texts: Behavior of RLC circuit elements at t = 0

texts:
I'm wondering what are the behaviors of the inductor, L, and capacitor, C, at t = 0+

Please correct my understanding of the above circuit if I am wrong.

At t = 0, the capacitor acts like a wire. So I think that Vc must = 0 since a theoretical wire has no voltage across it.
However, if that is the case wouldn't Infinite current be flowing through the capacitor at t = 0 ?
What would the current flowing into the inductor be?
Shouldn't inductor act like a open (broken) circuit at t = 0, which mean no current?

Clarification: The switch is closed for a long time before time 0, at t=0 the switch opens


texts: Transistor amplifiers, ac model Rd when diode is reverse biased

texts:
So why is resistance of diode is infinite if it's reverse biased by a voltage source? The way I understand it, is that holes (positive) and electrons (negative) will be further apart in the diode, which will make the capacitance less ... ? So because of that resistance would be higher (infinite)?

Here's the context, for those who want to know more.


texts: Eagle Drill vs. Diameter Parameters when making Through Hole Parts

texts:
I am working on making footprints in Eagle for a through-hole connector I want to use. I am running into some issues as I try to determine the appropriate diameter and drill size I need for the through hole pads. I am using this schematic as I design the footprint:

My through holes will be copper plated, so I am working from the diagram on the left. This portion of the datasheet for the connector clearly states that the finished hole diameter is 1.02 mm, but at the bottom of the drawing there is a figure given for a drilled hole diameter of 1.15 mm. Which of these two numbers should I use for my drill diameter in Eagle. Also, what should the hole diameter be in Eagle. In other words, how much copper should surround the hole?


texts: This LED was sold to me as 5 Watt LED, what's its voltage rating?

texts:
I've go this LED

Polarity is marked but no rating is written on its body. It's claimed to be 5 watts.

Has anybody worked with this? What's the voltage rating?


texts:
I am new to embedded C and been struggling with it for a while now.
The desired output for this project is:
When SW1 is not pressed, the blue LED must be on.
When SW1 is pressed the blue LED should turn on and off every 100ms.
I wrote this code but it doesn't seem to be working properly.
I tried it on the simulator and the LED toggles but the delay is more than 100ms, it's like a second.
And on the real board, I get random results, sometimes it doesn't turn off and sometimes it changes color to purple.
Why isn't this code behaving as it should? Why am I getting random results?

Code:
pastebin.com/ShE9rDCG

// BranchingFunctionsDelays.c Lab 6
// Runs on LM4F120/TM4C123
// Use simple programming structures in C to
// toggle an LED while a button is pressed and
// turn the LED on when the button is released.
// This lab will use the hardware already built into the LaunchPad.
// Daniel Valvano, Jonathan Valvano
// January 15, 2016

// built-in connection: PF0 connected to negative logic momentary switch, SW2
// built-in connection: PF1 connected to red LED
// built-in connection: PF2 connected to blue LED
// built-in connection: PF3 connected to green LED
// built-in connection: PF4 connected to negative logic momentary switch, SW1

#include "TExaS.h"

#define GPIO_PORTF_DATA_R       (*((volatile unsigned long *)0x400253FC))
#define GPIO_PORTF_DIR_R        (*((volatile unsigned long *)0x40025400))
#define GPIO_PORTF_AFSEL_R      (*((volatile unsigned long *)0x40025420))
#define GPIO_PORTF_PUR_R        (*((volatile unsigned long *)0x40025510))
#define GPIO_PORTF_DEN_R        (*((volatile unsigned long *)0x4002551C))
#define GPIO_PORTF_AMSEL_R      (*((volatile unsigned long *)0x40025528))
#define GPIO_PORTF_PCTL_R       (*((volatile unsigned long *)0x4002552C))
#define SYSCTL_RCGC2_R          (*((volatile unsigned long *)0x400FE108))
#define SYSCTL_RCGC2_GPIOF      0x00000020  // port F Clock Gating Control

// basic functions defined at end of startup.s
void DisableInterrupts(void); // Disable interrupts
void EnableInterrupts(void);  // Enable interrupts
void portF_init(void);
void delay100ms(unsigned long time);

int main(void)
{
        unsigned long volatile delay;
      // activate grader and set system clock to 80 MHz
        TExaS_Init(SW_PIN_PF4, LED_PIN_PF2);
        portF_init();
        EnableInterrupts();
        // set PF2
        GPIO_PORTF_DATA_R |= 0x04;
        while(1)
        {
                delay100ms(1);
              // if switch PF4 is pressed and LED is ON (00000101)
            if( GPIO_PORTF_DATA_R == 0x05)
                {
                      // turn LED OFF (clear bit)
                      GPIO_PORTF_DATA_R &= ~0x04;
                }
                // if switch PF4 is pressed and LED is OFF (00000001)
                else if (GPIO_PORTF_DATA_R == 0x01)
                {
                        // set PF2 - turn LED ON
                      GPIO_PORTF_DATA_R |= 0x04;
                }
                else
                {
                        // set PF2
                        GPIO_PORTF_DATA_R |= 0x04;
                }
        }
}

void portF_init(void)
{
        volatile unsigned long delay;
        SYSCTL_RCGC2_R |= 0x00000020;     // 1) F clock
        delay = SYSCTL_RCGC2_R;           // delay
        GPIO_PORTF_AMSEL_R = 0x00;        // 3) disable analog function
        GPIO_PORTF_PCTL_R = 0x00000000;   // 4) GPIO clear bit PCTL
        GPIO_PORTF_DIR_R = 0x04;          // 5) PF4 input, PF2 output
        GPIO_PORTF_AFSEL_R = 0x00;        // 6) no alternate function
        GPIO_PORTF_PUR_R = 0x01;          // disble pull-up resistor
        GPIO_PORTF_DEN_R = 0x14;          // 7) enable digital pins PF4 & PF2
}

void delay100ms(unsigned long time)
{
        unsigned long i;
        while(time > 0)
        {
                i = 1333333;  // this number means 100ms
                while(i > 0)
                {
                        i = i - 1;
                }
                time = time - 1; // decrements every 100 ms
      }
}


texts:
I was going through the datasheet of ADV7125 DAC and found this sentence confusing.

For optimum performance, the analog outputs should each
have a source termination resistance to ground of 75 Ω (doubly
terminated 75 Ω configuration). This termination resistance
should be as close as possible to the ADV7125 to minimize
reflections.

Well, what I think is - since the cable impedance is 75 ohms, and the load is also 75 impedance at the end of the cable, is n't the cable already devoid of reflections ? Then why adding that 75 ohms at the beginning (double termination) ??! Also suppose the cable impedance was 50 ohms in this case, what can we do to reduce reflection ?


texts: Quiescent power of BJT vs MOS transistors

texts:
This is a question about the power necessary to control a transistor circuit, i.e. the base current in BJTs vs. the gate current in MOSFETs.

Why is there quiescent power dissipated by base currents of BJT's?

Why doesn't it happen with MOSFETS?


texts: Serial Port communication to PC troubleshooting

texts:
GOAL
The goal is to bridge a serial port measurement device into a USB PL2303 device.  Various degrees of success were observed and I hope the community can point me in the right direction in terms of troubleshooting, based on the data / observations below.
SERIAL DATA DEVICE DESCRIPTION
A serial port measurement device (9600-8-N-1) has two outputs: each output sends a trio of bytes every second through:

green wire: TTL
blue wire: RS-232

The first byte indicates the qualify of the data and a good measurement is indicate with 0x80.
PL2303 HXD Description
I have successfully connected the TTL wire to PL2303 devices and have run into unusual results wiring the blue RS-232 wire to a pink PL2303 and believe it to be a HXD device:

Device Blue Wire:RS-232 <==> White Wire (PL2303 HXD)

HXD Description:

Supports  RS-232 serial interface with Programmable baud rate from 75
bps to 12 Mbps

Supports  RS422/RS485 interface

Extensive  flow control mechanism like adjustable high/low watermark
level, automatic  hardware or software flow control, and inbound data
buffer overflow detection

This product is designed for laboratory, product  testing, low-cost
MCU communications and other applications, there are four  lead,

HXD Wiring:

Red +5 V

Black GND

White RXD

Green TXD

Yellow RTS

Blue CTS

DATA / OBSERVATIONS
The first 3 lines show RS-232 results.  0x80 (valid data) starts at the end of the 3rd line:

Said measurement serial-device has only 2 additional wires (power / ground) for a total of 4 wires.
Assuming that there is nothing wrong with measurement device, (it has been tested good with other RS-232 adapters).  I inherited PL2303 HXD and although I can lookup a  data sheet, I do not have the original data sheet and can not be certain I have the correct data sheet.
QUESTIONS
Does the PL2303 HXD need to be configured somehow to 9600-8-n-1 or does it somehow default to the configuration or detect the communication protocol?  Any diagnostic questions or insight that would explain why the HXD does return good data are appreciated. Thank you
Perhaps the HXD model is not correct for RS-232 and the RS-232 design requirement should select a PL2303-TA?  Any clarification or insight that enables choosing the TA over the HXD (or vice versa) is appreciated.


texts: How to calculate energy transfer in inductive heating?

texts:
I designed an inductance heater. Its inductor is calculated 50 uH as below:

And I draw 9.4 A AC current at 33 Khz of it.

But, I want to know how to calculate the transferred energy to the working piece. Take this schematic into account:

Its power graph as below:

As you see some of the power is Reactance but there is always magnetic flux even when the power on the inductor is negative. Do I need to take the absolute value of the power as below?

Or it would be wrong and there is another calculation for the energy transfer ratio?


texts:
I have a circuit where I am using triacs to switch home appliances like fan, tube light etc. This is the circuit I am using:

(TRIAC1, TRIAC2, TRIAC3 come from arduino GPIO pins)

First load is a fan with a capacitor based regulator. (Sorry for showing fan and tubelight as a resistor). Speed is controlled by rotating a knob which changes the series capacitance. Lower capacitance means lower fan speed.

As seen from the circuit, I didn't use a snubber because I thought using a snubberless triac will do the job, however the following incident made me rethink about the situation:

1) When Bulb and tubelight are off and fan is ON, and I try to regulate the fan speed by rotating the knob, sometimes there is a flicker in the tubelight and bulb. Flicker is very short lived but still visible. Flicker doesn't happen at higher speed. It usually happens at lower speed levels. For ex - There are these levels: OFF, 1, 2, 3, 4, 5 (5 means direct connection to Live). When I switch speed from 2 to 1 (or vice versa), I see a short lived flicker in the tubelight.

2) If the fan is running at low speeds - 1 and 2, and I try to turn the fan OFF by pulling the GPIO (TRIAC1) LOW, the fan won't turn OFF. Instead it produces humming sound and continues to rotate at a lower speed which indicates partial turn ON of triac.

Now in order to fix this, I am planning to use a snubber. I read a few articles and this is the circuit I could come up with:

Rs and Cs are usually mentioned as 39 ohms and 0.01 uF respectively. However I have a few questions:

1) Is my assumption of spurious triggering correct? If yes, will the proposed circuit improve the behavior?

2) Usually snubber design for inductive load shows a pure inductor as the load and a parallel RC circuit as the snubber. Here, the load is LC due to the presence of capacitor based regulator. Should there be a modification in snubber circuit due to this?

Here is the fan regulator I am talking about:

EDIT:

Fixed the snubber circuit.

Added the image of fan regulator.

UPDATE:

Tried the snubber. It didn't work. I am assuming some sort of resonance when the regulator is kept at low speeds. This resonance might be preventing the triac from turning off completely.


texts: Relative difficulty between leading zero counting and addition

texts:
Consider a 32-bit or 64-bit ALU that must implement both count leading zeros and integer addition, with low latency (say a few cycles), implemented on a modern high frequency logic process.

Which is generally more complex, a fast adder or a fast leading zero count?


texts:
I need a help with filter realization. I dont understand how this works. This is a multiply and accumulate filter, I dont understand why cof[0] constant is multiplied, here is the code cof is the filter coefficients and sample is the samples. Any help with this very appreciated. Thank you

long long mac(int len, int *sample, int *cof, int item)
{
   int i, io;
   static long long y;

   io = 0;
   y = 0;
   item /= 4;
   for ( i = 0; i < len; i++ )
      {
      y += (long long)sample[io] * (long long)cof[0];
      cof +=item;
      io++;
      if ( io >= len )
         io = 0;
      }
   return y;
}


texts: In an opamp differentiator, how does high gain produce oscillations?

texts:
The gain of an ideal differentiator increases 20dB/dec - this means the gain increases as frequency increases. I'm wondering how high gain produces oscillations.

I've read so many times that negative feedback stabilizes the op amp but never quite get why the opamp needs stabilizing. I understand high gain is useless because a small input signal can saturate the output of opamp. Also I understand how the negative feedback reduces offset voltage, but that's it.

I don't get how high gain produces oscillations.

Any help?


texts:
I am designing a H bridge converter which is supplied with a 400VDC bus.

The switching frequency will be 20kHz

I want fit an LC filter to the output so that a sinusoidal voltage is produced, the operation and design of the filter is something that I have a good understanding of

My question relates to the capacitor type and dv/dt ratings

I thought metallised polypropylene capacitors were a good choice for an inverter filter capacitor and I have used them in the past with relatively low DC bus voltages (circa 24VDC)

A 400VDC bus isn't something I have much experience with my plan was to use a 680uH inductor like a Bourns 2322-RC and a 10uF capacitor like a Kemet  R463W510050M1K. The cutoff frequency would be around the 2kHz mark

http://uk.rs-online.com/web/p/polypropylene-film-capacitors/8752308/

However the datasheet tells me the max dv/dt is 100V/us, my H bridge will use IGBT's so the turn on time will be quite fast lets assume it switches on in 0.1us

400V in 0.1us is a serious amount of dv/dt and the capacitor is going to be very stressed and fail in no time at all

Can anyone advise me on what the best course of action is to protect the capacitor?, I have seen commercial drives use these types of capacitors so I am wondering how they are designed to last

Do we add a resistor in series with the capacitor to slow the rise times or fit in a dv/dt filter before the output capacitor so that it absorbs the bulk of the dv/dt stresses?, I believe a MLCC capacitor would be a good choice for this but I am open to ideas and keen to understand how to make a robust design


texts: Why is there no race around condition in NOR SR latch when S=R=0(initially)?

texts:
When the IC gets connected to the Vcc+, both the NOR gates get the input 0 and 0 (low) which yields the output 1. Now since both the outputs are again connected as one of the input to each of the NOR gate, the gate should yield 0 (Since the inputs now are 1 and 0). Now since the 2 inputs are again 0, the same thing should happen over and over again just as it happens in case of JK flip-flop where NAND gate is used while J=K=CLK=1.

Note: I haven't practically tested if the same race around condition occurs or not.


texts:
I have this IC here wherein pin 6 will take around 3A of current and a quick use of some online calculator says that the trace width for 3A on a 1oz. cu is 140mil (70mil for 2oz). On pin six it is impossible for me to place a 140 mil trace as it would hit the pads beside it. Even if we use a 2oz cu it would still have to taper in, as shown in the picture below.

Is what I did okay? Would the traces handle the current? I have noticed it to be also the case for BGA PMICs rated for high amps wherein I could not place a enough copper near where pads and will have to taper out.


texts: MIC28515 overheating with high input voltage

texts:
I've designed this MIC28515 buck regulator based on the manufacturer schematic reference. I'm planning to run it at 70VIn

I'm doing the tests with @ 5V 2A load Temp(Amb) = 20C.
When I set a VIn of 20V the IC's temperature shoots up to 68C for some reason.
For reference the temperature at VIn = 15V is just around 46C which seems somewhat normal.
Any suggestions to what could cause that phenomenon?
The manufacturer also claims to achieve 5A@50C with this IC.
My Design

Ref design:

Scope output @VIn = 20V:


texts: How to drive a 6v relay using 74ls08 output?

texts: Im using a 74ls08 and gate ic, and I cant drive a 6v relay by using the output of the 74ls08. In what way can I drive the relay?


texts: I am trying to learn about audio electronics and built a simple single stage amplifier with a 2N3904 transistor.  I play the guitar and know that when you plug an amp into a speaker it's impedance has to match.  I calculated the output impedance of the circuit by measuring the open voltage and then adding a resistor to the circuit until that Voltage was halved.  This gave me 15k ohms.  I have a small .5W 8ohm speaker.  How do these to things correlate?  Do I need to change the circuit to make the output impedance 8ohms or am I not understanding correctly?


texts: MAX485 Burns after working for some time. RS485

texts:
I am using the circuit provided in the datasheet of MAX485. But is getting burnt after some time of working. I don't understand what is the problem. I also tried getting new ICs from a trusted supplier, but the problem still persists.

It is working fine for some time, after that some small amount of smoke is coming from it and its input side is getting latched to 5V.

I connected it with a PIC Microcontroller. Everything else in the circuit is working fine including ethernet communication using ENC28J60 IC.

Edit :

So I understand that I need to connect common ground for RS485.

But I need to connect with devices directly working on AC mains. It only provides 2 lines of RS485 (A and B). How can I communicate with these type of devices without causing these problems ?


texts: So in the linear operating range of an op amp the output is A(Vp-Vn) where Vp is the voltage at the positive terminal and Vn is the voltage at the negative terminal.  But that does not seem to always be the case when I am doing my homework problems.  It seems that the output voltage is whatever is needed to keep the rest of the circuit valid according to Kirchhoff's Laws.  Is that a correct assessment or am I missing something?


texts: Best way to drop 10volts at 0.25A with linear regulator?

texts:
What would be a minimalistic circuit design to convert 14V to 3.3V at 0.25A with a linear regulator? I'm thinking about two linear regulators.

I've tried LM7805(14V-5V) to LD1117(5V-3.3V.) LM7805 gets hot even at 0.1A. What would be best solution without switching power supply? I'm trying to power efficiently ESP32 module from a car's battery.


texts: Driving H-Bridge Inverter via AVR (trilevel or bilevel PWM)

texts:
I'm attempting to design an inverter that will be driven mainly by an AVR uC. The H-Bridge will consist of 4 IR840 N-Channel MOSFETs. The left and right hand side of the H-bridge will be driven by two IRF2113 MOSFET drivers.

I will of course be feeding a pulse width modulated waveform to the mosfet drivers. However, my question is, will the input to one of the mosfet drivers need to be inverted? Suppose the left hand side MOSFET driver is fed directly from the AVR. Will the right hand side driver need an inverted version of the PWM waveform? If so, is it best to use the the inverted output on the AVR Mega 168? Or would a separate NOT gate be a better choice?

The actual signal is a 50Hz sinusoidal. In order to reduce harmonics, I've also seen some designs where "Trilevel" PWM was used. If I understand correctly, in Trilevel PWM the duty-cycle goes to 0 when the sine wave is at zero. At negative peak, the duty cycle is max. but the PWM is also negative (hence 3 levels).

Now, in order to generate the sine-wave my LUT has 625 values that go from 128 to 255 and then down all the way to 0. 128 is half-way in terms of amplitude. Now, in order to have a PWM that resembles like the figure below

I am thinking that my LUT should go from 128 to 255 and then when it reaches 128, it should rise back up to 255 instead of going down to 0. This should vary the duty cycle in such a way that it resembles the PWM waveform in the above figure. However, at 128 the duty cycle would still be 50% - should I just go from 0 to 255, back to 0 and then back to 255 in one-cycle?

Now, in order to actually have the trilevel PWM, one side of the H-bridge is driven via a 50Hz square wave while the other half is driven by the PWM waveform in the above figure. I am reluctant regarding this design - won't this cause the supply to be shorted when two MOSFETS on the same side are turned on at the same side?


texts: How to design a circuit for genrating random numbers

texts:
I'm working on a project, where we need to generate random numbers between 1-5. After researching a bit I figure out generally LFSR (Linear-feedback shift register) is used for generating random numbers (more preciously Pseudo-random).

So, I used 3 bit LFSR with polynomial \$x^3 + x + 1\$, which generates \$2^3 - 1 = 7\$ numbers {1, 2, 3, 4, 5, 6, 7}. Now I need to somehow map {6, 7} to one of the number {1, 2, 3, 4, 5}.

I can not use a mod circuit as it will be deterministic. So, How can I randomly (or Pseudo randomly) map {6, 7} to {1, 2, 3, 4, 5}.

I'm not a electronics student, so pardon me If the question seems silly.


texts:
I'm currently using circuits.io to create a very simple circuit. However, before ordering the board, I would like to print it in order to see if it's the right size and/or the elements fit in my own designed footprints.

Since circuit.io only lets you download gerber files, is there a simple way to print those gerber files? Maybe if someone can point me to the spec for the gerber files I could craft a simple script to convert the file to something that I could actually print.


texts:
I'm looking to design a circuit around the CN3065 that will be solar powered with a li-ion backup battery. I've seen circuits that can achieve this by using a charge controller with a dedicated load output, but CN3065 doesn't have one (and unfortunately I'm restricted to this chip since SeedStudio's OPL has no other charge controllers.)

The basic recommended circuit is as follows:

I'm reluctant to connect the load just over the battery terminals since this would presumably upset the charger, but most load sharing circuitry I've seen is designed for a constant input voltage rather than a solar panel:

My worry is that enough current will flow through Q1 to block current through the battery, but this will not be sufficient to drive the microcontroller attached to the load. I could place a (for example) 5V zener at the gate of Q1 to get around this, but then I'm back at the problem where I'm potentially charging the battery partially whilst drawing a load across it.

What supporting circuitry should I add to safely and sensibly connect a load to this circuit when the input power supply is given by a solar cell?


texts:
I have a design using PCIe 4 lanes that interface between 2 CCAs and will be connected through a connector/flex connection.
In the event that the mate to either CCA is not available, I want to know how I can verify the signals to the connector of each CCA and then, if there is a loopback that I could use to test one CCA if the other isn't available.
One CCA will have an ASIC/PCIe and the other will have a ZyncSoc/PCIe.

Thanks


texts: Multilayer PCB - are there voids in substrate between layers?

texts:
Having one of those moments again where you feel you are missing something seemingly obvious.

In multilayer PCB stacks, you have alternating layers of copper and substrate (either prepreg or core). The question is, does this result in voids?

Obviously the copper has some thickness, so if you pattern the copper, and then attach a layer of dielectric (e.g. FR4, rogers, etc.), then surely the areas where there is no copper would now be voids in the structure. Unless of course the dielectric is a conformal layer or the voids are in some way filled?

As an example. Take a design with a 6-layer stack up and say you want to do impedance controlled traces - is it possible to put a reference place on, say, layer 3, and the signal on layer 1 - assuming of course a gap is left in the copper on layer 2. If there are in fact voids caused by the thickness of copper on layer 2, then this wouldn't be possible because there would be a gap in the dielectric. I'm not planning on doing this, it's just a curiosity.


texts:
Im trying to learn a bit about the techniques to create an ASIC. I found that the NRE-Costs are the biggest cost part which means the creationg of the masks and you get a minimum number of ASICs back.

Shuttle Services seems to be cheaper which means that more ASIC-Designs are done at the same time. So the part of the costs one has to pay is smaller. But the resulting ASICs are less too.

But what about the masks resulting from that. Are they have a disadvantage against a dedicated run? I mean will producing more ASICs be more expensive since the mask only is for, maybe, 1 ASIC instead a full mask for many of the same ASICs?

In fact my question is if the costs one is saving by using shuttle services is firing back later when producing more ASICs.

If someone knows... whats the cheapest way to get a most optimized (custom) ASIC that has the potential to create more of the same ASICs for cheap later. Maybe 28nm or even lower...


texts: What is the binary format of the OrCAD .OLB files?

texts:
I want to auto generate .OLB files for my own components, so I need to either use Orcad Capture scripting, or alternatively write the binary .OLB files myself.

Is there anybody that have seen a specification of the binary OrCAD .OLB file format ?

Sorry if this question is non-SO compliant... however, I have sometimes seen useful answers toeven non-SO compliant questions ;-)


texts:
I've been trying to figure something out for a while, and have experience with digital systems (logic gates, flip-flops, etc.), but not necessarily "real" systems (with Zener diodes, etc.) so here goes the preamble...

Looking at other posts here, I'm not going to try to build anything.  What I want is something to run my 19V Router (1.75A max based on the wall wart) + 5V 2A ATA (2A, again by the wall wart) during a power failure.  But I want hours of runtime, and not minutes, so an off-the-shelf UPS is right out (without any modifications, AC->DC->AC->DC conversions).

Reading a response on this post, it seems like the best idea is to hook up a charger right to an AGM battery (or other lead acid).  So then I want to get a good charger to maintain the life of my battery, so I came across a charge controller for solar panels, which is great, because according to this thread, I can attach a 120VAC -> 30VDC transformer to a 24V charge controller, the controller to a 24V AGM, and the battery terminals to a few buck regulators for the 19VDC and 5VDC, and voila! Simple DC UPS...  I think.

Now here's the question(s):
1) Should I worry about the charging profile (PWM and MPPT) affecting the buck regulators / the output to the router & ATA?  Or will the presence of the battery help "buffer" the fluctuations to keep the steady ~24VDC?
2) This is one I'm throwing out there to see what people have to say about it: I notice that the charge controller has a "load" output (link added to explain what I'm referring to, not necessarily for buying advice).  Could I use this instead of connecting directly to the batteries?  I doubt I'll need to use the LVD function, but I don't know how it'll work (0 switchover time, etc.).  This post makes it look like it doesn't work that way looking at the relay, but I don't know.

Thanks in advance!


texts:
I'm looking for an algebraic solution (gates and adders) to align the '1' bits of a vector to the LSB's.
For example:
11001001 will transform to: 00001111
1000 will transform to: 0001
1100 will transform to 0011.

I achieved the above but with a custom HDL function that's quite complex (non algebraic) and will probably have poor timing performance. A LUT is another option - but not if the vector is long.
So can this be done algebraically ?


texts: Can any type of op amp output stage be forced into Class A operation?

texts:
I'm trying to choose a good op amp for a Class A small signal audio amplifier circuit.

I've done my research and understand the use pull up or pull down resistors externally to force Class A operation, and other specs influencing op amp choice generally.

What I can't find in my research is this - when choosing an op amp for use in a Class A design, is there an advantage to one type of internal op amp output stage type?

e.g.,

rail-to-rail emitter follower
totem pole (NPN-NPN)
common collector (NPN-PNP)


texts: Are there any powerful processors that exist that are hobbyist friendly?

texts:
Ok so I have a project I am wanting to create but it would require a bit of processing power. The most powerful thing I've seen yet has been the ATMega1284P. Really by power I mean I need Program Memory and RAM, not raw MIPs.

Is there anything else out there that is hobbyist friendly?

By hobbyist friendly I mean not having to have any expensive machines to solder it (rework stations etc). Also of course being capable of buying just a couple of them without spending an arm and a leg. And of course having freely available compilers and other software tools.

My project is to build a small (portable) calculator with simple graphing capabilities and possibly some limited programming capabilities.


texts: Can I convert a split phase motor to a permanent split phase one?

texts:
The induction motor I am using has a dead current relay and finding the part is proving quite difficult. The motor has neither a run nor a start capacitor. I am considering the idea of switching the dead relay with a capacitor from a pancake induction motor salvaged from an old bread making machine. My guess is that it should work considering a bread machine requires quite a bit of torque.

Is there issues with doing this? Will the motor burn out? The motor has a main winding and a start winding which is connected to the current relay. If I replace the current relay with a capacitor, I'm afraid that it will burn out the start winding.  If I did this, will I have to also add a relay to switch the capacitor off after a second or two?


texts: How is the integration time set for a camera?

texts:
I using the TSL1401R-LF Linescan Camera Module, which reads in a 1 X 128 line of pixels, and I'm having trouble understanding how the integration time is set for this device.

I understand from page 9 that the minimum integration time is a constent that results from a function of the clock speed, but I don't fully understand when this integration period takes place.

According to the timing waveform (Figure 1 on Page 5) the integration period appears to be set after the first 18 clock cycles. Does this mean that the integration period is set while the camera is outputting pixels?

How is that even possible? Also does this mean that in order to achive the minimum delay time I would have to take that time and divide it across those remaining 110 clock cycles (i.e. 307 ns for a total of 33.75 us)?


texts:
What techniques are useful when layout a circuit on a breadboard? Specifically, making it as least cluttered and readable as possible. My circuits always come out looking horrible and really messy.

Is there a technique on where to start? Or some rules on what to connect first?


texts:
I'm using the op295GP opamp. In the datasheet on the 1st page it's says it has a wide single supply operating range 3 to 36v. What's the difference between the supply voltage ( pg5) and the single supply operating range 3 to 36v?

http://www.farnell.com/datasheets/663089.pdf


texts: I have an idea for an automated small toyish submarine. Can I use the Arduino for this? Does it behave well under the ocean surface?  I think I'll need some kind of casing with silicone around it, and a small propeller that will push it forward. What's the best suited Arduino for this project? It will need to be remote controlled.


texts: How to make an external PCI adapter that runs on USB3.0?

texts:
Motivated by old PCI (NOT PCIe) cards, and laptops without expansion slots, I want to try making a PCI-over-USB 3.0 solution. This is about 70% experimentation, and 30% actual use.

Is this viable? I was thinking of buying something like this Cypress USB controller, in conjunction with a PCI bus master board, and (I'm guessing) a microcontroller to interface the two.

I'm not experienced in this, which is why I want to learn... I am an EE, but not this advanced.

Is this doable? Would it be possible as a long term learn-and-do project?


texts: How do you design a CMOS buffer with exact same delay of a CMOS inverter?

texts:
Everyone knows that a CMOS inverter is simply a PMOS connected to an NMOS. There are situations in asynchronous design that we need to compensate for the inverter propagation delay in a parallel signal running along side of the other signal. In that case I can see that designers add a buffer in gate level schematics.

But I need to implement that buffer by myself using CMOS cell libraries and it seems to me the most rational approach is just to put two inverters in series which inverts the signal twice hence acts  like a buffer. But it seems to me that the propagation delay also will be doubled.

How one can have a buffer with EXACT same propagation delay of an inverter?


texts: Which electrical circuit produces a decaying alternating current wave in response to a pulse?

texts:
Consider a voltage source with an infinitesimally short burst having voltage time-integral 1.

I see how a low-pass filter creates an output voltage like \$e^{-kt}\$ for some \$k\in\mathbb R\$.  What if \$k\$ were complex?  Which circuit produces a decaying alternating current in response to a pulse?

Illustrated below are the results of five evenly-spaced pulses.  The blue graph shows the output of a regular low-pass filter.  The orange graph (with \$k\$ that happens to have exactly the same frequency as the input pulses) is what I'm trying to produce.

Here's a diagram of what I think is being suggested in the comments:


texts: Can I connect 4 TTL communication devices to a single atmega 2560 RX pin?

texts:
I need to read 4 devices with one Rx pin on atmega2560. Devices are DS457 Motorola bar code readers. They communicate in inverted TTL at 9600 baud rate. I have already made signal inverter with 2 transistors and resistors.

My question is:

Can I connect all 4 Tx of DS457 to single Rx pin without problems or do i need any diode for each reader?

The readers will not work at the same time. Only one at a time.


texts: Do I need to isolate the power to buzzer circuit from other sensitive circuit?

texts:
I am planning to add a buzzer circuit, which will share the power plane with a micro-controller.  Do I need to add a choke or so to isolate the two components?  If so, how should I do it?  Thanks in advance.

Buzzer: http://www.digikey.com/product-detail/en/CT-1205C-SMT-TR/102-1200-2-ND/504821


texts:
I'm trying to generate tone with couple configurable frequencies on pin OC0B of Atmega328, Fast-PWM mode.

TCCR0A  |= _BV(WGM01) | _BV(WGM00);
TCCR0B  |= _BV(WGM02);

TCCR0A  |= _BV(COM0B1) | _BV(COM0B0);
TCCR0B  |= _BV(CS01) | _BV(CS00);

OCR0A   = 100;

I set to Fast PWM(7), then prescaler 64, OC0A is disconnected and OC0B is connected in inverting mode. There is no tone on OC0B.

I was only able to generate tone on OC0A when I set COM0A0 to 1. But I only need to generate tone on OC0B.

So there are two questions.
1. How can I generate tone on OC0B pin?
2. While tone is generated on OC0B, can I use OC0A as GPIO pin?


texts: How does inductance change with presence of different directional magnetic fields?

texts:
If I design a coil driver for a certain application, I assume there is a fixed load right? It may have drive any inductance between an interval but you can not drive any coil, because the driver is designed for a certain application.

So, how does a coil's inductance change with a magnet's presence?

Assume I want to drive the coil with sinus wave. Just under the coil, there is a magnet that its center is fixes to a shaft and its in release.

So, say that my coil is designed to draw peak to peak 1A in 10KHz.

How would that change? How can we calculate the change?


texts: Advantage of series vs parallel battery in handheld product

texts:
There are many handheld product like laptop or an Handheld measurement equipment that all parts would works fine with 3.3V or lower VCC. However these devices still comes with a 11.1ٰV battery or higher voltage.

My question is, doesn't it more efficient to use 3 cell in parallel instead of series in order to reduce power dissipation on voltage regulator?

As an example in fanless laptop (like Asus UX305), 5v seems to be sufficient for most parts, so probably 2 cell 7.4v battery suits better than 3 cell 11.1V.

Where am I going wrong?


texts: How can the contact points of jumper cables handle the hundreds of amps required to start a car?

texts: When jumpstarting a car, you connect those big alligator clamps to the terminals of the batteries. The cables themselves can handle the current just fine, but the contact points between the alligator clamps and the battery is extremely small. I'd imagine a maximum of 4 teeth are touching each terminal. How do those contact points not simply explode under the hundreds of amps?


texts: Using on-board amplifiers instead of external amplifiers

texts:
I'm trying to replicate a Silicon Photomultiplier array multiplexing scheme by SensL. The link to their application note is found here:

http://sensl.com/downloads/ds/TN-Signal_Driven_Multiplexing_Method.pdf

According to the datasheet of their MicroFJ-60035-TSV silicon photomultiplier, the fast output signal is 150 mV, so some amplification is necessary. In their paper, they used a set of Minicircuits amplifiers in order to amplify the multiplexed output signal, the MiniCircuits ZX60-43 and ZFL-1000LN+ external amplifiers. They were connected in series in order to provide a larger gain of ~200. Links to the datasheet are below:

https://www.minicircuits.com/pdfs/ZX60-43+.pdf
https://www.minicircuits.com/pdfs/ZFL-1000LN+.pdf

I never worked with external amplifiers such as these before, and I'm looking for a way to swap them out for smaller IC amplifiers that can be put on the same board as the SiPM array. Going from larger amplifiers such as these to ICs, how are they different, and how can I choose the best IC (or pair of ICs) to provide the same gain? Why are external amplifiers such as these used in the first place rather than ICs? Also, given how they're both broadband amplifiers, how would they be put in series? It feels that the amplifier order matters, but I'm not sure how.


texts:
I am working on modifying SG acoustics SGA-SOA-2 op-amp.
The goal is to make it work on 32 \$ \Omega\$ headphones load, and use more common transistors.

What I did was:

Replaced all transistors with common SMD ones with highest gain (BC847C/BC857C).
Re-tuned currents for lowest distortion and input offset voltage. Returned C2 for frequency compensation due to much faster transistors and higher op-amp gain.
Removed protection diodes
I figured out that original design(with transistors replaced ) had visible harmonics when working on 32 \$ \Omega\$ load (~ -80dB), I replaced output stage with compound transistors. I was also trying to design MOSFET power stage, but harmonics were terrible (~-60dB), probably due to huge crossover, which feedback was not quick enough to fix. Another option was to add extra BJT power stage, but final performance was about the same as compound version.
Reduced resistance of R10 and R11 to 1 \$ \Omega\$, original 4.7 \$ \Omega\$ ones were causing harmonics.
Removed 10 \$ \Omega\$ resistor between C4 and C5. Not sure why it was there.

Here is what I've got at the end:

Simulation on 1kHz sine shows that 1st harmonic is at -124dB, second at -135dB.

The questions are:

What is more adequate model for headphones? I currently use 32ohm resistor, but I feel this is far from reality.
What is the purpose of R7, R10 and R11 resistors? On simulation results stay the same if I remove them.
What is the purpose of C1/R8?
Is there something in this circuit which will make it performance much worse when implemented in real world (target application - 32 \$ \Omega\$ headphones amplifier)?
Are there some transistors which have significantly better performance for this circuit? Lower noise for example... I was thinking about also common SS9014/SS9015 - but not sure they are any better than BC847C/BC857C for this application.
While performance with feedback seems to be ok, when feeding small signal (1mV) with no feedback I see that amplifier is highly non-linear. Is it beneficial to make it more linear in this configuration?


texts:
I'm actually designing a circuit with decoupling capacitor. I'm done with the schematic and now I'm working on the routing.

Here come the question :

In schematic you can put the capacitor anywhere between the supply line and the ground. While in routing the capacitor have be as close as possible to the chip. Is there any more requirement? For exemple :

simulate this circuit – Schematic created using CircuitLab

Please, look at it as if it was a layout. Is there any difference if the decoupling capacitor is before or after the IC? Normally these two circuits will have the same behavior but I got a doubt.'

Don't hesitate to comment if I wasn't clear enough. Thanks :)


texts: Equivalent circuit of a three phase induction motor

texts: So, i know that a equivalent circuit of a single phase of a three phase induction motor is just like a transformer equivalent circuit when it is at standstill. When, however, it is rotating the frequency dependent quantities like voltages, currents, reactants change as they should change. But, the thing with induction motor is, the input power and the output power, when rotating, are not same(because some power is given to the shaft) unlike transformer. In transformer i used this property to create equivalent circuit referred to primary side. Now, how can i further simplify the equivalent circuit of the three phase motor (equivalent circuit referred to stator).


texts: How to automatically reverse the direction of a motor without human intervention?

texts: I am working on this project where I have an arm at rest want a brushless DC motor (BLDC) to automatically reverse: (I've added an image and text above for a visual reference) Given that I am taking High School Physics, and am not in any way good at engineering, how can I accomplish this as simply and as inexpensively as possible? Thank you in advance for all of your help!


texts: High frequency clock from clocked RS latch

texts:
We were taught that this circuit is not of much use as when CLK=1, J=1 & K=1, Q toggles at a very high rate. So suppose I want to make a high-frequency clock, can I use this?
Of course, the frequency itself can't be changed for given logic gates, but can I make a clock from this by giving high inputs at CLK,J and K? (I don't care about the exact frequency, it should just be like in MHz)


texts: These rectangular 2x5 and 2x3 pin connectors seem to be commonly used for flat ribbon connectors.  This example is from an AVRUSB programmer.  What is the name of this style connector?


texts:
I have a buck converter with an operating frequency of 180khz.
I want to power a microcontroller  (raspberry pi) with it at 5v.
I understand the 180khz noise is not desirable for use with a microcontroller.

Would a capacitor across the output of the converter help remove the 180khz noise? How do I find the right one if so?

Many thanks in advance.


texts:
I am adding over-voltage, over-current protection in my circuit. My circuit/PCB has many DC-DC converters and these converters power a processor and various other ICs. The input voltage range (that I want to allow but my circuit can withstand more than that) is 7-12V and current will be 350mA (at 12V) or 600mA approx (at 7V).

The over-voltage protection will be provided by Crow-Bar circuit and fuse. The over-current protection should be provided by fuse alone.

After reading about various PTC fuses, I got to know they have maximum Voltage Rating. After reading more, I got to know may be PTC fuses are not good choice for over-voltage protection but I want to know what will happen if we exceed it's voltage rating?

Will it open or short? I guess if it gets open-circuit after applying voltage more than it's rating than it's still useful for my circuit as it will act as PTC re-settable fuse below 60V (rating of my fuse) and as conventional fuse for voltages more than 60V.

The acceptable voltage range to my circuit/PCB (although the circuit can withstand more voltage) is 7-12V but I have selected a PTC re-settable fuse with maximum voltage rating of 60V (0ZCF0100AF2A).

After reading document of my PTC fuse, I got to know PTC fuses has to maintain it's internal temperature, then a short-circuit event at 60V (caused by crowbar circuit) will have higher resistance (and lesser current) than a short-circuit (actual short-circuit event) at 7V. This means at 7V, there will be more current flowing through my circuit (few hundred ohms) and I am not sure if it can cause some issue? Please help.

Also, if the user applies 60V and my TRIAC gets triggered (shorting power rails), then due to very high resistance of PTC fuses (at 60V), a current less than holding current of TRIAC will be flowing which may turn-off my TRIAC. I can sense that TRIAC will keep on turning-on and off. Am I correct? If yes, then how to fix it?


texts:
Is there any way I can reduce the DALI commissioning?
I have an Occupancy sensor, photo sensor and a switch which are DALI devices.
So every time when I turn on the device it goes for commissioning and it takes 20 secs for one device commissioning.

Is there any way that I can reduce the commissioning process each time when I turn on the device ?

Say if I write the DALI values to an EEPROM, will I be able to use the values instead of commissioning the next time when I turn on the device?


texts: Motors and H-bridge - High current on PCB

texts:
I want to control a motor by using H-bridge on PCB.

I am using IRF4905 and IRF3205 MOSFETS (P and N, respectively), and some 4N27 Optocouplers.

The motor takes about 70 amps

How can I make my circuit board hold this much current?


texts:
I'm building various r/c vehicles like warplanes, tanks, auto-turrets, etc. and I want to fit some of them with some kind of a weapon. I've decided an air soft gun is a good choice. So, mounting and shooting the gun is easy. The problem begins, when I want to create a software damage model for my vehicles. I need to find a way to detect when and where my model was hit.

I'm thinking about to layers of plastic or some other slightly elastic mterial, each covered with sth conductive. They are placed close together. When a bullet hits one, it bends, touches the other and the current flows. However it doesn't seem to be a very elegant solution. Especially when it comes to hit angles like 60+ degrees or centrifugal forces acting on my plane. I don't think it will also work on sloped surfaces like airfoils etc. I will also probably fail on thin surfaces, because the sensor would be quite thick itself - the upper layer, the conductive things, the gap, etc.

Is there a better way of doing this? I'm really out of ideas so any help means a lot. Also, please don't tell me how good/bad my idea is. I just need to find a solution to a problem.

Thanks,
Kiel366

P.S.: I don't need an exact hit location. Locations like: wing, elevator, first half of the fuselage are totally fine.


texts: Why phase bump causes signal distortion in source follower?

texts:
This lecture shows the frequency response of source follower.

As you can see, the transfer function has one pole, one zero and they are close to each other.

So from the phase plot, we can see that there is a phase bump here. I have heard that the phase bump causes signal distortion.

However, I can't find the explanation anywhere now.

If the pole and zero are far from each other, the output signal is also shifted in phase.

Could anyone explain that? Thank you.


texts:
I'm having the odd problem where a STM32F4 wont resume operation after pulling NRST low.
Power cycling the STM32F4 works just fine.

NRST is configured with a 0.1uF cap to ground. It has no other connections.
On removing the jumper from NRST to ground, voltage on the NRST pin is 3.3V (as it should be).

Any ideas as to what may be causing this issue?

Thanks!


texts: H2S Sensor with 1 PPB Lower Detection Limit

texts:
We're trying to create an IoT device that can detect/mesaure H2S in ambient air with a
lower detection limit of 1 ppb or 0.001 ppm

However, checking Digikey and other similar suppliers, I haven't found any sensors that fit this requirement. Below are examples of what I've found:

DGS-CO 968-034:
https://www.spec-sensors.com/wp-content/uploads/2017/01/DGS-CO-968-034.pdf

ZE03 Electrochemical Gas Sensor Module:
https://www.winsen-sensor.com/d/files/PDF/Gas%20Sensor%20Module/Industrial%20Application%20Gas%20Sensor%20Module/ZE03%20Electrochemical%20Module%20V2.4.pdf

What we've found are already existing devices, which are classified as H2S Analyzers:

Model T101 UV Fluorescence H2S Analyzers: http://www.teledyne-ml.com/products_/instruments/gaseous/sulfur/Documents/T101.pdf

Serinus 55 H2S Analyzers: https://www.ecotech.com/wp-content/uploads/2018/01/ECOTECH-Serinus-55-Brochure.pdf

We've already considered integrating with existing devices, but we want to see if we can develop our own device.

Does anyone know of a commercially-available sensor that can fit this requirement?
Or perhaps, a company that makes these sensors on request?


texts:
First- I've read through various posts about similar topics, looked at schematics, and I couldn't quite find something that matched this particular issue, here goes..

Cliff notes at the bottom...

I'm helping a customer with a lift.  In reality, it's a material lift with a winch and an Up/Down controller, but she is handicapped and needed something, and this was readily available. The problem is that as long as she holds either button down, the winch will continue to pull up or let out cable, to the point that either motor trips the fuse or the cable gets tangled up and causes problems.  I would like to install 2 limit switches, 1 to stop the motor when going up at a certain point and 1 to stop the motor when the lift reaches the bottom.

I have 2 240v AC or DC limit switches with NO and NC contacts.  When opening up the motor and controller electronics, im met with 4 wires.  With my meter on any combination of these wires and the motor activated, I get various voltages, all DC.  The highest voltage I've seen when running the motor was 144vdc.  If I break any of the control wires (like with the limit switch relay) neither direction works.  There is only a white and a black wire going into the motor, if I break either of these neither direction works.

I see that going up or down produces either positive or negative polarity, and from what I've read, some diodes might be necessary, I just don't understand how I would wire them in.

My background is commercial and residential electrician, nurse call, security, and fire alarm systems.  Sometimes these systems needed diodes, but of course this was all low voltage.  Can anyone provide me with some insight on how I could make this work?  I can provide a rough wiring diagram of what's existing.

Cliff notes:
Lift with 100+VDC motor, need to limit up and down travel
When breaking any wires with a relay, neither direction works
Please help me figure out how to install a limit switch for up and a limit switch for down travel!


texts:
My purpose is to store values from 0 to 3.
From synthesis point of view, which one of the following will be more area efficient, when coding in VHDL ?

signal a: integer;
signal a: integer range 0 to 3;

Will the first choice takes up 32 bit register inside FPGA?


texts: two-quadrant frequency mixers without transistors?

texts: I understand that four-quadrant frequency mixers without transistors are difficult to implement. But what about two-quadrant? Would implementing mixers without transistors still be difficult? Would these mixers suffer from "threshold voltage" (if using diodes, maybe?) and one has to increase the physical size of the mixer?


texts: Why are data records in intel hex files often limited to 16 bytes, even for long contiguous blocks?

texts:
I'm not sure if this is true in general, but all intel hex files I have seen (from Atmel Studio, STM32CubeIDE and MPLAB) use data records with a length of 16 bytes. Even when the addresses written to are completely sequential there are just a lot of 16 byte records. This results in a lot of redundancy, because the preamble with the memory address is transmitted again and again.
Why is it not common to use longer data blocks? Even if we wanted to stick to power-of-two data block lengths we could easily fit 128 Bytes in one record with the one-byte length-field and reduce the amount of totally transmitted data by some ~30%.
Sometimes I see even shorter blocks, still without skipping any memory addresses. In the following example I added "-" to make it easier to distinguish the seperate fields (:LL-AAAA-TT-...) from each other.
:10-0160-00-3D0B00083D0B00083D0B000800000000-9F
:10-0170-00-3D0B00083D0B00083D0B000800000000-8F
:0C-0180-00-3D0B00083D0B00083D0B0008-83
:10-018C-00-10B5054C237833B9044B13B10448AFF3-C5
:10-019C-00-00800123237010BD0C00002000000000-23

There are a lot of data records with 16 data bytes, always increasing the address by 16. And then there is one record with only 13 bytes, with the next address increasing only by 13.
Can somebody shed some light on this behaviour?
Because both gcc for STM and AVR controllers as well as the MPLAB XC Compiler for dsPIC show this same behaviour I don't think that it is someting architecture or compiler specific.
Is this just "evolved historically" to keep compatible to older parsers? Or does the checksum become too inefficent for longer records?
And for the even shorter records I can only imagine it has something to do with the linker? Are the shorter data records the end of some logical block and the linker is for some reason not filling up the record with data from the next block? Or is there some other reason?


texts: Location of modulation and multiplexing in a GSM network

texts:
My question is regarding the location of GSM channel access methods TDMA/FDMA.

Here is an illustration how voice is processed before reaching the base station on a tower:

It is not mentioning the multiplexing(TDMA/FDMA) part.

I have two questions:

1) Where is the modulation carried out? On the Base Station or before?

2) Where is the multiplexing(TDMA/FDMA) occurs? On the Base Station or before?

(Is base station just composed of antennas for transmission or also includes any of those processes?)


texts:
I'm planning to start a project based around a Freescale Cortex-M0+ chip.  Apparently the M0+ is SWD only and does not support JTAG.

I've been looking around, but I can't find much in the way of SWD programming hardware, and was wondering if anyone had a recommendation.  I'd also like software that would allow me to step through my code on the chip. Any suggestions?


texts: How to use 0.1 inch header footprint for high speed signals?

texts:
I have a board which has a dual 0.1 inch header footprint (the totally standard kind you see everywhere).  Trouble is, this carries a fast 300-500 Mbit DDR LVDS signal (!!) to another board. Okay, so not the best use of a 0.1 header there.  I didn't make this but would like to reuse it since the board is cheap and readily available.

So: I'd like some way to carry high speed signals with some degree of signal integrity starting from a 0.1 inch header footprint.  This isn't a request for a part recommendation, rather a question about how to approach this.  For example I could use super-short pogo pins, or a shielded ribbon, or FPC cable, or maybe solder a single header strip to both boards directly (~3mm mated height, permanent), or maybe there is a high speed connector that fits this footprint.  I can design the other board this would connect to however I want.  Also, I don't need to cover any distance, this can be as short/direct as physically possible.

Btw: The differential pairs go to side by side pins on the header, and they are quite well length matched.  So there is that at least.


texts: How does the controller know when to jump to the ISR?

texts:
I am talking about things at the core level.

As far as I understand, the controller core just executes instructions which are fetched from the memory (Fetch - Decode - Execute). When an Interrupt arrives, how does the core/ALU decide to jump to the ISR?

Because we, or the compiler, don't add any instruction to poll the interrupt status - then how does it know that an interrupt needs to be served?


texts: MOSFET switching times due to dynamic gate current

texts:
I'm having difficulties in understanding this statement from "The Art of Electronics 3rd Edition".
I don't understend how they estimated the MOSFET's switching time using the gate current and the feedback capacitance. Here is the quote:

As another example, imagine switching a 5 amp highvoltage
load with a power MOSFET (there aren’t any highpower
JFETs), in the style of Figure 3.50. One might
naively assume that the gate could be driven from a digital
logic output with low current-sourcing capability, for
example the so-called 4000-series CMOS logic, which can
supply an output current of the order of 1mA with a swing
from ground to +10V. In fact, such a circuit would be a
disaster, because 1mA of gate drive into the 200 pF average
feedback capacitance of the IRF740 would stretch the
output switching speed to a leisurely 50μs.

Figure 3.50:

Thanks.


texts: How to estimate Li-ion battery health for an unused smartphone?

texts:
I am considering purchasing a new smartphone that is several years old and could use a little electrical engineering help from the EE geniuses here.
I've performed quite a bit of research, and found so much conflicting (and just plain wrong) information that I'm hoping the voting system here on StackExchange will help yield at least one quality answer.
The device I'm considering is a Google Pixel 3XL.  I don't think they make them anymore, and my understanding is that they were manufactured in 2018-2019.  I think a safe rough estimate would be to say that the stock of phones is 32 months old.
The chemistry of the battery is Li-ion.  I found a chart with self-discharge rate estimates for different battery chemistries here.  It claims a 10%/month self-discharge rate for Li-ion batteries at room temperature.  I have no idea if that chart is accurate.  I also have no way to know the temperature at which the devices were stored.
The devices are still in their boxes and should have never been charged after the original factory charge.  I don't know the level of the factory charge (if you do, please chime in!), so I'm thinking a reasonable estimate might be 70%.
If my estimates are close, and math hasn't recently changed, that would mean that the battery would be more-or-less discharged after ~7 months.  Given the estimate that the device is 32 months old, that would mean that it has likely sat with a dead battery for a little over 2 years.
From my research, many people claim that if a Li-ion battery goes completely dead, it will never work again.  But I've also read numerous stories of people buying old smartphones in the box and being able to charge the batteries and have them work fine.  On the surface, it seems that only one of those claims could be true.  But I'm guessing there are details of which I am not aware.
Given the above data, what is a reasonable expectation for the batteries in these phones?  I realize all answers will be approximates, but about what percentage of the original capacity will one likely receive from the battery?  And, approximately, how long until the battery will no longer be able to be recharged above 50%?
If you can explain the reasoning for your answer, it will help me learn more.  Thank you.


texts: What happens if you put the connector of a live charger in your mouth?

texts:
So what exactly would happen if you put the connector of a plugged-in charger in your mouth? I am sure it is a bad idea but can it really hurt or even kill you?

Some posts on social media led me to this question.


texts: Why is XOR called a controlled inverter?

texts: I wonder why XOR is called a controlled inverter?


texts: Finding the equivalant impedence of a circuit

texts: I've been given the above circuit and asked to find the equivalent impedance, however after drawing it half a dozen different ways I cannot find a way to simplify it. I can simulate it, and I get (what I think is the right answer) of -0.934-j1.467 ohms, but I'd like to know if there's a way to do it manually, and if there's some useful trick that I'm missing out on here. Or maybe its something simple!


texts:
As I asked in "Adding multiple analog signal" before, I got that: for adding some signal together, we can only use op-amp, instead of lovely integrated circuit (ough).
But the question arise because now I want to add differential signal output from ADA8282 and I have found this ST application note AN4586,
"Signal conditioning, differential to single-ended amplification", helpful for amplifying differential to single ended, but is there any easier way than converting each one separately to single ended, then add them together? I really hate handling op-amp by two power supply(ough!).

I have found book about this:

It tell: maximum feedback resistor is restricted to input offset voltage. I want to minimize it to minimize OpAmp noise, (2) What is minimum limit?

Other methods:

(3) Can I use this method (serializing sources) that is easier because we don't have to waste anything to drive OpAmp:

Not: (4) after this I want to send signal through balanced line.

Why I want to add 4ch together? I don't want to load them on processor then I want it to be analog. These are come from 4 antenna that placed close to one another, after some analog process we have pure sine wave range from 0 to 3Mhz, I want to add these 4 channel to improve SNR (ADA8282 told something about phase matching then I hope summed signal will have better SNR). Also if I decided to change LNA PGAs gain they will all be changed together.


texts: Why is harmonic voltage flowing to the source

texts:
In non-linear loads, Current Harmonic Distortions are created, which in turn creates voltage harmonic distortion that are said to flow from the load to the source ( system ).

My understanding of Harmonic Distortions in AC circuits ( based on different papers as well as What exactly are harmonics and how do they "appear"? ) is that harmonics are not "created", but are merely a mathematical representation needed to do the Fourrier transform of the wave and explain it mathematically.  If that is the case, how can these Harmonic Distortions flow back from the load ?

Any insights would be appreciated.

EDIT:  Reading http://electrical-engineering-portal.com/res/Harmonic-detection-and-filtering.pdf, it seems I was mistaken and it is harmonic current that flows back to the source, causing a distorted line voltage in the load.  My question then becomes, is this harmonic current flowing back through the neutral line ( 3-phase wye ) ? If so, how does this works in delta connected system ?  Would this mean the current is flowing back to the source on the same line ?


texts: Oscilloscope voltage not matching function generator

texts:
What are the reasons why my oscilloscope shows a different voltage from my function generator?

I have set the Vpp of the function generator to be 10V, but I set the probe to 10x and on the device, it is set to 1x, for this setting I get 20.80V output.

When I set the device to 2x, I get 41.6V and at 10x I get 208V. I am new to using both devices and I don't know why I can't accurately get the voltage value from the function generator.

Please help.


texts: Variable does not bounce back as desired (LED's)

texts:
I am changing a variable with a predetermined rate. When my variable gets too large, I cap it back to the largest value I want to make it, and change the sign on the rate to make the change go the other direction.

x += rate;
if (x > 255){
  rate = -rate;
  x = 255;
}
if (x < 0) {
  rate = -rate;
  x = 0;
}

However (when I execute this code and use the variable to control the brightness of some LED's), once x goes to or above my highest threshold, it resets to the lower value and goes up again.

None of the other code manipulates or uses x, unless when I am setting CRGB values with x to an LED array. This code runs in void(loop).


texts: Voltage Regulator Not Providing Enough Current/Voltage

texts:
I am attempting to deliver 9V @ 1.1A to a PCB circuit design using an L7809CV voltage regulator which is rated for 1.5A max.

Using a power supply, I can deliver the required current and voltage to my PCB (9V/1.1A) and all is well.

Once I turn up the voltage to ~12-14V (emulating an automotive application) and feed it into the L7809, the regulator will output 9V as expected with NO LOAD on the device. Once the load is applied, the device will only deliver 6.9V/0.1A, well below what is expected.

The device does get hot to the touched during extended use, but I would expect the correct current/voltage to (9V/1.1A) to be delivered when the device is cold. Is this not true?

Datasheet for voltage regulator: http://www.mouser.com/ds/2/389/CD00000444-249828.pdf


texts:
I am trying to simplify the following portion of a circuit for analysis.  I am not sure if it would simply be shown as 2 resistors in parallel or something else as the nodes are connected.   I do not have the resistor values currently, so I need to derive an equation for the resistance at a,b, and c.

Edit: I am looking for the resistance between a-b and b-c.

Thanks


texts: Any website resource to find diode/transistor replacement from through-hole to SMD footprint?

texts:
I always having this problem when trying to convert my prototype design (which usually built using normal discrete through-hole electronic components) to surface-mount (SMD) version for size-shrinking & mass-production.

I always have difficult time to find a substitution/replacement model for the SMD side. Anyone here have any good resource/website which can direct me to find SMD replacement for diodes & transistors?


texts: How to know which side of the terminal block on pcb drawing

texts:
I'm planning to use Seeed's PCBA Prototype, where they request to use their open parts library(if you want them to solder the parts for you).

I came across their screw terminal block(part 3470070P1). And viewing it in Eagle, looks like this:

How do I know which side is the entrance for inserting the wires? I've checked the 3D model and drawing on the terminal, but it seems they didn't state which side is which?


texts:
I am trying to understand a simple class-AB output stage. The bias voltage for the transistors is made by using two diodes. The following picture show the circuits. The currents drawn are how, i believe, the currents will flow.

I want to understand the currents, to be able to find a value for the resistor, R.

Especially i am thinking of the following:

Is the transistor Q2 solely driven by the input? I think this as there is no other path for the base current.
Will the current through R be used for driving the transistor Q1 and the diodes?

Then, if this is the case, how can a reasonable value for the resistor R be found?

I know that the lowest possible voltage across R is 5.5 V, and i know that I_C for Q1 is at most 260 mA. Given this i believe that the minimum current for driving the transistor is:
$$R = \frac{5.5}{(\frac{0,260}{\beta})}$$

This i enough current for driving the transistor, but how is it possible to determine the needed current through the diodes? I suspect that it is a quite low current. Will the easiest way to just undersize the resistor, and forget about the diodes?


texts: Is it possible and safe to freeze rechargeable NiMH batteries to revive them?

texts:
I have a couple of rechargeable AA NiMH batteries that I can no longer charge.
After the charger claims the batteries have been charged fully they still output 0 Volt.
I found some posts that claim that batteries like this can be fixed by

placing them in a freezer in a sealed plastic bag for 16-24 hours
letting them warm up to room temperature
Charging and discharging them a couple of times

Is this safe?
Could this restore the batteries to "decent" working condition?
The question is meant to be generally useful but my specific batteries have the following specs: AA/HR6/DC1500 NiMH/1,2V/2300mAh.


texts: How best to detect missing/lost packets in XBee S2 communications

texts:
My main aim now is to determine if there will be any packet loss in transmission between two Xbee s2 modules, when the distance between them are varied, and in different environments.

Please how best can i measure/detect this..

many thanks


texts:
How can I find the Temperature Coefficient of Capacitance of the following capacitor series:
http://www.cde.com/resources/catalogs/TAS.pdf


texts: USB Type C swap A/B rows for easier routing

texts:
I'm routing a USB-C receptacle on a carrier board for a System on Module. The location and orientation of the receptacle and the SoM headers are dictated by the design of the device.

I noticed that if I would swap the signals running from the SoM to the A and B rows of the USB-C receptacle, routing would be substantially easier. As the USB-C port design is mirrored, one would assume that would works just as well.

But I'm afraid that somehow the bult-in logic of USB-C where it resolves cable orientation would somehow cause trouble in my swapped layout. Could I trick the system by swapping ALL signals except CC1 and CC2? Would DisplayPort still work?

If I just leave it as it is, I will have to have differential signals cross-over, as well as have P/N swaps, wheras in the swapped situation, I can simply route almost everything in more or less straight lines.

-edit-

Below is an image of the supposed routing if I make an exact copy of the schematics of the development carrier board that my SoM supplier has made avilable to me, shown within the physical constraints of my carrier board layout. I think everybody would agree that if I rotate the pins on rows A and B of the type-c connector, so (SS)TX1 becomes (SS)TX2 and vice versa and (SS)RX1 becomes (SS)RX2 vv., routing becomes much easier. And then I haven't even shown the amount of P/N reversal that would have to be applied in the below case.

Any way i guess the comments that have already been made reassure me I can go ahead and rotate A and B and don't do anything weird with the CC1 and CC2 pins, because I understand now that I can just see this rotation as exactly the same as a normal connector rotation.


texts: How do run a 120Vac water pump using Arduino starter kit supplies

texts:
I'm very new to EE so forgive the simple question. I have a small water pump 120Vac that I want to turn on and off via my arduino. I have the arduino starter kit as well as a 12v relays.

I've tried to get the relay working and can't even seem to do that. This is the instructable, which I'm trying to do.

I understand that I have a 12v relay, which means I need a way to send more current through to the relay than the arduino 5v can provide. so I tried the smaller transistors (bc5478) in the arduino starter kit, along with one diode that also came with the kit. I thought the transistor had enough juice to activate the relay, but when I put a multimeter to it, it switches between 7 and 9v.

I should also mention I have a 9v battery connected to the relay which should power the pump.

Conceptually, am I doing anything wrong? Maybe I just hooked it up incorrectly?


texts: Grounding an Opto-isolated Microcontroller

texts:
First off - thank you all so much for all you have done for me, and the hobbyists all around the world.  I love you all and truly appreciate what you do for the field of hobby-ism.

The AC in this circuit is the mains from the wall, 120v AC.  The full wave rectified voltage is 170v DC. My goal was to control the vacuum motor speed using python in the Raspberry Pi.
I am presently running the above setup, and it seems to work fine for the most part.

I am trying to find a better solution for grounding so that I can attempt to solve two minor issues: (and make it safer?)

ISSUE ONE: I have a k type thermocouple also attached to pins on the Raspberry Pi.  It works perfectly, up to the second the motor starts up.  Then, the temperature reading goes crazy, jumping all over the place.  I suspect due to noise.  I have read that one should ground the thermocouple's breakout board to "MECHANICAL GROUND".  Which, as I understand it, is not presently in my circuit.

ISSUE TWO: The motor runs slightly more erratically when I have the thermocouple active.  I say "erratic" because I can hear it rise and fall slightly every 30 seconds or so.  This does not happen when I remove the thermocouple from the circuit.

Thus my questions are:

1)  Are chassis ground, mechanical ground, and earth ground the same thing when it boils down to it?  Which one should I connect my thermocouple to? What if I ground my circuit like the schematic I created below, and then tie my thermocouple ground into earth ground.  In doing that, wouldn't I just basically be destroying the electrical isolation that I created with the optoisolator?  I would hate to fry another Raspberry Pi, that was so sad.

2)  Is there any advantage to grounding the negative side of my capacitor to earth ground?  I am thinking that it must be, at the very least, a bit safer.

3)  Is earth ground just the third prong on a normal household outlet?

Proposed circuit modification:

-The Raspberry Pi is powered by a 5v wall wort.

-The Thermocouple is connected using the MAX31855 breakout board, and is interfaced as such, using a soldered PCB and a ribbon cable to the Pi:

This is what it looks like in real life, the yellow wire is a grounding wire that I added to see if grounding to a different ground pin on the Pi would make a difference in my wildly fluctuating temperature data.  It sadly did not: