texts: protect a driver for steep edges into capacitive load from external voltage

texts:
I want to have a 5V trigger output signal that has rising and falling edges of up to 200ns max. into a load of 1-5 nF.

I thought about using MOSFET driver circuits (e.g. MC33152, many suppliers have similar). They are able to actively drive to GND and VCC (in my case 5V) with fast edges (range of 10-100ns) into some nF of load.

My problem: Because this 5V trigger will be an external pin, I need to make the driver output pins robust against, accidentially connecting external voltages (20-35V) to it and I have no idea how to do it.

I thought about using a schottky diode to block voltages from outside to go into the driver output. This however would also mean, that I could no longer drive the falling adge actively (because the diode will prevent that aswell). So I would need a pulldown resistor behind the diode, but this would not be enough to get steep falling edges.

How could I protect this trigger output against externally connecting 35V to the driver output pin without losing the possibility to drive the falling edge?


texts:
I think one is a 10uf capacitor 10-20l.
Second one no idea.


texts:
Simple question: Is it OK for the output pins to be high? I want to use the 7401N together with a 74LS138 to do memory address decoding. I will connect two Yx pins to two two separate input pins on the 7404N. From here the two output pins from the 7404N will be connected to the same pin on my Micro-Kim (the /DEN pin). Will that fry the 7404N?

simulate this circuit – Schematic created using CircuitLab

Regards, Jacob


texts:
I’m designing SLA 3D printer and I need to design UV LED array for LCD screen backlight. Preliminary design is 5x3 (5 parallel lines with three LEDs in each). All LEDs will be soldered on PCB.

The catch is that every LED will have 1W and my inner engineer cries out for active regulation, even though I understand, that passive regulation (via resistors) would be much simpler. I’m just high school student with very little knowledge about electronics, so could you point me to some solutions?

I’m going to solder the PCB myself and I’m not working on the project full-time, so I would definitely prefer something simpler (maybe regulation via MOSFETs?). I don’t need complicated dimming of individual LEDs via IC in BGA package or something like that.

LED parameters:
voltage: 3.2-3.6V
current: 300-350 mA
further info: https://www.aliexpress.com/item/1W-3W-5W-Warm-White-Royal-Blue-Orange-UV-Violet-RGB-High-Power-LED-Chip-Light/32804097246.html

I’m sorry for any grammar mistakes, I’m not a native speaker.


texts:
In modern devices (mobile phones, tablets, laptops) the battery charging current is automatically switched off when the battery reaches 100 %. After being disconnected, the power supply cools down. It is a healthy practice for the battery.

But if (after the charge) the device is kept connected to the mains and is used, who provides the energy? The battery or the wall socket? If it is the battery, the power supply should continue to charge it, but it doesn't, because it keeps being cold (1); if it is the power supply - somehow bypassing the battery - it should again become hot as during the charge.

(1) Moreover, the battery would continuously charge and discharge around 99% - 100 % and this could damage it.


texts: Switch array (crosspoint) and DC biasing of audio signal

texts:
For a project at my university, I am making a guitar effects switcher. Guitar effects work on instrument level audio signal which is AC only. I plan to use ADG2128 analog switch array (https://www.analog.com/media/en/technical-documentation/data-sheets/ADG2128.pdf) for this purpose. I am trying to achieve the following thing:

If I power ADG2128 from a single rail power supply (12V), I need to bias the input audio signal before routing it in the input of the chip, so it does not go in the negative voltage range, in order for the switch array to work.

I have never done something like this before, so my new question is how should the circuit for the DC biasing look like.

I need to add some DC voltage (DC bias) before sending the signal into the array and then remove this offset before sending it to the next effect. What is the proper approach to do this without accidentally filtering the sound or altering it?


texts: ATtiny85 power consumption double expected

texts:
I'm trying to get an ATTiny85 to run off a battery. I have it clocked from a 16.384 MHz crystal, with the divide-by-8 fuse set. Vcc is 3.3 volts. Figure 22-7 in the datasheet says that at idle ( set_sleep_mode(SLEEP_MODE_IDLE); sleep_mode(); ), it should draw around 300 µA. In actual fact, I see it drawing more like 850 µA. I can't figure out why the power consumption is double expected. I've turned off everything in PRR except for timer0, which I've configured to interrupt every 25 ms. So it should spend the vast majority of its time in the idle state, which is the best I can do given that I still want the timers to count.

The fuses are 0x7f, 0xdf, 0xff.

Here's the code it's running for this test:

#include <Arduino.h>
#include <EEPROM.h>
#include <avr/sleep.h>
#include <avr/power.h>

#define P0 0
#define P1 1
#define P_UNUSED 2

ISR(TIMER0_COMPA_vect) {
  // do nothing - just wake up
}

void setup() {
  power_adc_disable();
  power_usi_disable();
  power_timer1_disable();
  //PRR = _BV(PRADC) | _BV(PRTIM1) | _BV(PRUSI); // everything off but timer 0.
  TCCR0A = _BV(WGM01); // mode 2 - CTC
  TCCR0B = _BV(CS02) | _BV(CS00); // prescale = 1024
  // xtal freq = 16.384 MHz.
  // CPU freq = 16.384 MHz / 8 = 2.048 MHz
  // count freq = 2.048 MHz / 1024 = 2000 Hz
  OCR0A = 50; // 25 msec per irq
  TIMSK = _BV(OCIE0A); // OCR0A interrupt only.

  set_sleep_mode(SLEEP_MODE_IDLE);

  pinMode(P_UNUSED, INPUT_PULLUP);
  pinMode(P0, OUTPUT);
  pinMode(P1, OUTPUT);
  digitalWrite(P0, LOW);
  digitalWrite(P1, LOW);

  while(1) { sleep_mode(); }
}
void loop() {}


texts: Is conventional flow a real, physical thing or is it something we made up?

texts:
Is conventional flow a real, physical thing or is it something we still use for historical reasons?
• Electron flow is the actual current flow and the textbooks are the other way because of Benjamin Franklin.
• Conventional current is real and electrons just go the other way.
I know nothing about this and searching on the internet just made me even more confused.


texts: "mapping voltage" on an analog potentiometer using a voltage divider

texts:
I'm working on a simple project to learn electrical circuits. I built a little sound box that will play tones when you press buttons.

The battery provides 3volts and the "power boost" is a buck converter that increases the voltage to the 9v needed to power the speaker.

I wanted to include a potentiometer to adjust the volume so I used one I had on hand. The problem was that most of the range of the potentiometer provided so little voltage that no sound came out of the speaker and then right as you get towards the end the volume shoots up.

I read a bit online and it seemed like using an analog potentiometer would resolve the issue since the resistance changed exponentially instead of linearly.

I swapped out the potentiometers, but it seems like I'm running into the same problem: most of the range of the potentiometer's resistance the voltage is so low that no sound comes out of the speaker.

I was talking with a friend and mentioned the issue and he suggested using a voltage divider to map the desired voltage range along the potentiometer. This sounds sensible, but I have no idea how it should be implemented.

Does using a voltage divider to map the voltage range to the speaker make sense? If so, how would I do it? I've been searching around for things like "potentiometer with a voltage divider" and "mapping voltage on a potentiometer" and have found plenty of results, but not for the task I'm trying to accomplish.

Any suggestions? Helpful links?


texts:
So initially S1 and S4 are closed and current flows as seen above.

After some time S1 and S4 are open and current flows as seen above. Now I am confused about the polarity of the inductor, what if I said the current flows through D1 and D4 instead of D3 and D2 ?, would that be wrong ?


texts: Solder through-hole or surface-mount components first?

texts:
I am new to surface mount soldering. On a board with both SMT and through-hole parts (header pins), which parts should I solder on first?

I imagine the technique I use for SMT soldering is important. I have access to an oven and a heat gun - baking the circuit board after soldering on my header pins might cause some trouble, but I was wondering that the standard practice was in general.

I read here that

  The surface mount soldering must be done before thru hole soldering
  because thru hole soldering creates imperfections on the underside of
  the board that will prevent good thermal conduction between hot plate
  and board.

but this is specific to SMT soldering using a hot plate.


texts: Mystery circuit with a functional description

texts:
Im trying to understand the following circuit and its cryptic functional description.

How does this circuit work?

I especially struggle with the following things:

What is DEC8(blue)? Standard component?
010 triggers line 4(green), why? Should it maybe be 100?
What function does the inverted gnd behind a transistor serve? (red)
If current flows from vdd to gnd(orange) is f considered 0 or 1, why?


texts: Optimizing Multilevel circuit Logic with SDCs

texts:
I am reading "Principles of Modern Digital Design" on chapter 3.10, but I am confused on a certain part. It says that you can reduce multilvel circuit logic using SDCs.
Suppose you have the boolean function:
p = (a+b)'
q = (bc)'
f = p(b') + (p')(c') + qc
And suppose that the first level of the circuit produces the folliwing SDC:
S = (p')(a')(b') + pa + pb + (q')(b') + (q')(c') + qbc
Now we use the universal quantification of S w.r.t a, as the the second level of the circuit (f) does not use a as an input, to get:
S_{a} = pb + qbc + q'b' + q'c'
The book says we can use these "dont care" values to minimize the function to :
f = (p')(c') + q.
I don't understand why, and the book does not explain it well. I was wondering if someone could explain?


texts: Additional Resistor For Pierce Oscillator

texts:
I want to build SIM Card Reader by following a schematic from here as follow:

I realized that the clock generator (upper center) form a Pierce oscillator but with an additional resistor (R2 symbol in the schematic), which different than Pierce Oscillator circuit at wikipedia:
.
I've also found other variant of pierce oscillator as follow:

Which tapping output from the inverter instead of the capacitor like in SIM card reader schematic.
Could you please explain the use of R2? What if I removed the R2 from the schematic? And what the differences between the first and the last Pierce oscillator circuit?


texts: I ordered a Square reader so I can take it apart. I guess it used to be they just used a raw magnetic values from the strip. In order to encrypt it they must have some processor that takes power? Are they powering it off the stereo wires?


texts: Square wave generator has nigh-useless output

texts:
I have a system that was designed for testing digital components.  I have a device in the system which is used for generation and acquisition of digital signals.  Now, I will happily admit to not fully understanding everything I'm about to say, but:

The outputs of the device have a 50Ω nominal impedance,
The cable carrying these signals is a 50Ω cable designed for the device,
The PCB the cable is plugged into is supposed to use 50Ω characteristic impedance on the lines with length matching to 0.5" and signals routed on the same layer.

For clarity:  the output of the device is sent through a cable, which is attached to a PCB, where the signals are routed a short distance to a high pin-count connector.  I am trying to see how high of a frequency I can reasonably generate with this device, so I started with the default for the software I have:  50MHz.  And the signal looked like this:

When I slowed down the signal to 1MHz to get a closer look at the transition, I got this:

I believe that I'm following the instructions in the device's specification sheet correctly...50Ω cable (designed for the device), 50Ω traces on the PCB (if the company who designed the PCB did what they said they did), into a high-impedance load (my scope).

I suppose my question is this:  am I measuring the signal wrong, or was the system designed wrong?  Is there anything that I am grossly misunderstanding?  If the system was designed wrong, are these graphs sufficient to show that or is there another measurement that would be more illustrative?

Edit:  I was asked to show what the signal looks like when "properly" terminated, aka not just floating non-terminated out of the connector of my system.  The process through which this signal arrives is kind of a mess (see my comments) but here's what I've got:

Edit#2:  I stuck a 50Ω resistor between the digital output I'm observing and the ground that the signal is referenced to and I got the following output.  From my understanding of this conversation, this seems to not be what I would have expected.

Edit#3:  See The Photon's accepted answer, but here's what the signal looked like after I removed a long, unterminated cable that was essentially dangling in the wind and also terminated the point I was measuring with a 50Ω resistor.


texts: Why do we need pull-up resistors or tri state pins for AVR external interrupts?

texts:
Let's say we need to write a program for ATmega32, that reacts to an external interrupt(INT0) through the pin D2. The interrupt is to happen during the falling edge of the signal.

I noticed it in the books that
DDRA = 0b00000010 is done to "activate the pull-up resistor". Why do we need it? Do we have to do the same if we want rising edge interrupt or a level triggered interrupt?


texts: Identifying Crystal Resonator Case Marking ('T' in a Diamond)

texts:
I have been trying for several hours to identify the manufacturer of a quartz resonator.  There is a marking of a 'T' in a rhombus, like so:

Does anybody know who's mark this is?  I know that I've seen it before, but none of the lists that have come up on any of my searches contain this logo.  I also tried performing a Google image search with this drawing (and a few variations) without result.


texts: Suppose I have a power supply with 2x12V cables. The 12V has been split into 2 inside the power supply. What happens if I join these power lines together in parallel, from an electrical properties point of view? What effect will this have on the power output?


texts: Is cache memory unnecessary in microcontrollers?

texts: Do we use cache memory in microcontrollers, if not, why not? If yes, what is its application in embedded systems or it is enough just to have RAM?


texts: Opto isolator for an Arduino weather station?

texts:
I have some Davis weather sensors that I want to attach to an  Arduino to build a small weather station.

I would prefer to have one power supply, but how would I create a opto-isolated circuit for the rain meter (reed switch) and the anemometer (reed switch). I know there are circuits that use opto-isolators like the 4N35, but how to I split the power? I prefer not to use a battery or something that could go flat. I can use a small solar power circuit maybe.

It is correct that I will need to power supplies, one for the isolated circuit and the other to drive the Arduino.

Any ideas? Suggestions etc. What is the ideal circuit for opto-isolators?


texts: Total current used by a brushless DC motor

texts:
Is it correct to say that 'the current' drawn by a BLDC motor is the same as the current from any single phase at a given time (assuming they are all balanced/equal in magnitude)?

I came across this diagram describing the characteristic shape of a BLDC current waveform:

From this diagram, it seems that the current is roughly flowing through one phase at a time, with only a tiny amount of overlap. What this doesn't look like is three sinusoidal waveforms 120° out of phase - a situation where the total current is more easily understood and calculated.

What is convention here?


texts: Why do some devices have 200V on the case?

texts:
I recently got a desktop LED lamp, and I feel a "strange" slight vibration when touching the metal case. I found that other devices also have high voltage on their case.

What is the reason/trade-off to design the PSU that way? Are "real" transformers inefficient? Even if it's harmless, why is the high voltage connected to the metal case, and not just through insulated wires?

When I turn the lamp on, the setup in the picture measures the power line (220V) 214Vpp (59Vrms). When I also touch the metal case, the voltage drops down to around 30V.

AC adaptor:


texts: Synchronized pulse generation from wirelessly connected boards

texts:
I want two or more boards (less than 10m range) to generate a LED blink at same time, within 1 ms difference, using wireless communication. First, due to power consumption, I am thinking to use bluetooth low energy as wireless medium. My concept is basic: each board has a microcontroller and a bluetooth module. One of the board will just broadcast a signal every minute and also blink a LED. The receiver will blink LED based on the set time interval, and whenever it gets signal from the broadcaster it will blink. Thus the outputs are synchronized every minute.

I would like to know how feasible this concept is or if I am overlooking something, because it looks pretty simple design. Or any other alternative solutions? Board size, power consumption and time synchronization are main constraints here.


texts: Will a man get electrocuted if he places the electrical test screwdriver on his foot?

texts:
Below is the typical circuit when somebody do the "test light" on wall electricity socket (Image 1):

In this "images 1", very little current will flow into his body, because the high electrical resistance of the "Test Screwdriver", then the "Test Screwdriver" will produce light.

But if that man do the "test light" using below method (image 2), will bigger/lethal current will flow into his body than in "image 1"?

Assume that same power source, and same "Test Light Screwdriver" used in both "image 1" and "image 2".


texts:
I am looking for a device which I do not know exists.

I would like to store the state of a number of analog switches, perhaps driven by a D Type Flip Flop.

I'd like to drive the flip flop and set values with a momentary toggle switch.

What I am looking for is a type of analog switch, which could store memory and survive power downs without relying on some sort of constant power source like a small battery. Basically a parallel accessed EEPROM with direct access to each of the bits through a single pin, or something that behaves in a similar fashion.

Can anyone think of a solution to this problem? Does something like this exist? My research came up with bistable multivibrators, but I could not find information that indicates if those would survive a power down or not. Cost and size are of concern to the design, of course.


texts: Home Automation Sensor Circuit Unexpected State

texts:
I embarked in a DIY project to replace a burnt home automation controller with a solution based on a Raspberry Pi using its GPIO inputs and outputs. I designed and built the electronics using breadboards and it's pretty much working now after several iterations. I still have a glitch that I haven't managed to understand and sort out and wondered if anybody could help me out to understand what could be the physical mechanism that is driving it and find a solution for it.
The problem arises only when the fire sensor is triggered, and the issue is that the associated led lights up as expected, but at the same time all the leds of the motion sensors light up as well and remain in that state indefinitely. The behavior is expected for the fire sensor as it is of a bistable type, but I don't know what drives the leds of the motion sensors to remain on indefinitely. The flood sensor doesn't light up, it's only the 6 motion sensors. The outputs in the raspberry side show the 7 sensors as active. The issue doesn't always occur, in some cases it works correctly and only the fire led lights up. It seems to occur most likely if several motion sensors have been triggered when the fire sensor is triggered, but not really sure. Once I cut the current from the fire sensor to ground via the transistor, everything returns to normal.
You can see the pictures and other info in the link https://www.raspberrypi.org/forums/viewtopic.php?t=300969.
The fire sensor info is available in this link, I'm afraid it's only in Spanish: https://www.calytel.com/Files/110195/153493301422160.pdf
The motion sensors are Pyronix.
The latest schematic is:

I am trying to find a fix before I jump into designing the PCB, would really appreciate if anybody has any insight on what could be the cause/fix. Thanks!
Edit:
After further investigations I think I have found the issue. I took some readings in the comparator when the fire sensor was active and found that the input in the comparator was negative, around -0.7 V. The spec sheet of the comparator has the following maximum rating: VIN Input voltage -0.3 to +36 V. I read that Phase Reversal can occurr in some comparators, this seems to explain the behaviour I am encountering. I have seen that I have different voltage levels in the ground cabling of my breadboard. Not really sure what the cause is, could it be the lengths of cabling in my breadboard?
Now the question is how to solve the issue. As I am going to build a PCB, with proper ground plane design will I solve the issue? As it's the first time that I'm going to design a PCB, can you give me any advice on how I should do the PCB design to solve this problem?
Another question is if I should connect the earth cable to the ground input from the power supply. The previous controller I am replacing had connections to both earth and the negative port of the power supply. Any disadvantages on connecting the earth cable to the ground?
And one final question, in my design I have two grounds, one corresponding to the 15V power supply, which I plan to connect to earth unless there is any issue with that, and another one in the Raspberry Circuit side (plug is not earthed in this case). Can I put both ground circuits on the same layer of the PCB making use of a 2 layer PCB or should I put them in different layers, requiring a 4 layer PCB?
Thanks in advance for the help!


texts:
I need to control an LED with a N-channel mosfet, but need the cathode to be connected to ground. I learned to do it this way:

but when I tried to connect it differently to keep the cathode of the LED grounded like this, there was a big voltage drop across the mosfet for some reason:

Exactly why does this happen? Would I be correct in thinking that using a P-channel mosfet would serve my purpose?


texts: Downsides of using a Heavy Guage wire with Low Amperage?

texts: I understand that different gauges are available for different amperages. Is there any downside to using a cable that is able to support a high amperage, for a low amperage?


texts: Full wave bridge rectifier: Does the capacitor "widen" the input voltage?

texts:
I am learning some basic electronics, and I'm trying to wrap my mind around some measurements I made on a full wave bridge rectifier.

Using my oscilloscope (grounded) and an isolation transformer to "float" the circuit I am measuring,  I made the following observations:

On points A (CH1-blue) and B (CH2-yellow).
Please note the "width" of the waveforms at their base.

On point C (CH1-blue). Same base width.
Without the filtering capacitor on point C, that's the expected waveform. Once I connected an electrolytic 100uF 25V capacitor as a filter, I got another expected waveform as well (DC level with ripple.)

Point C on channel 1 (blue) now with parallel capacitor.
What I'm not sure I understood is the waveform of points A and B again with the capacitor now filtering the output wave:

That above is point A on channel 1 (blue) and point C on channel 2 (yellow).

And now, point B on channel 1 (blue) and point C again on channel 2 (yellow).
Please note the wider base of the waveforms of point A and B with the capacitor when compared with the same points without it.
To explain this change, I came to the conclusion that since the ground alligator clamp of my oscilloscope is conected to the negative of the now charged capacitor, during the positive semi-cicle on point A (the rising of the waveform) point B is now 14V "beneath" point A or in other words, point A is 14V above ground - i.e. the leftover stored charge on the capacitor (first smaller peak). And then, the EMF of the transformer takes this waveform to its nominal value in volts shortly after (second taller peak). Point B is symmetrically opposite.
So, the negative lead of the electrolytic capacitor is in some sense advancing the rise time of the waveform on point A and in the other hand, delaying the fall time of the waveform in point B.
Is my conclusion accurate?


texts: AVR GCC: How do I improve code optimization

texts:
I tried to compile the following C code:

period = TCNT0L;
period |= ((unsigned int)TCNT0H<<8);

The assembler code I'm getting is the following:

    period = TCNT0L;
  d2:   22 b7           in  r18, 0x32   ; 50
  d4:   30 e0           ldi r19, 0x00   ; 0
  d6:   30 93 87 00     sts 0x0087, r19
  da:   20 93 86 00     sts 0x0086, r18
    period |= ((unsigned int)TCNT0H<<8);
  de:   44 b3           in  r20, 0x14   ; 20
  e0:   94 2f           mov r25, r20
  e2:   80 e0           ldi r24, 0x00   ; 0
  e4:   82 2b           or  r24, r18
  e6:   93 2b           or  r25, r19
  e8:   90 93 87 00     sts 0x0087, r25
  ec:   80 93 86 00     sts 0x0086, r24

So instead of 4 instructions it gets 11!

I tried to choose O1, O2, O3 and Os optimization options. The result is the same (except that O3 option optimized away this code at all).

I could write the source code in the following way:

period = TCNT0L | ((unsigned int)TCNT0H<<8);

I will get smaller, but still not optimal code:

  de:   22 b7           in  r18, 0x32   ; 50
  e0:   34 b3           in  r19, 0x14   ; 20
  e2:   93 2f           mov r25, r19
  e4:   80 e0           ldi r24, 0x00   ; 0
  e6:   82 2b           or  r24, r18
  e8:   90 93 87 00     sts 0x0087, r25
  ec:   80 93 86 00     sts 0x0086, r24

However I will not have a guaranty that the lower byte will be accessed first any more (this is essential requirement to keep 16-bit reading correct). And still the code has many extra unnecessary instructions.

Am I able to change compiler options and/or change the source code to make it better? I'd avoid go to assembler.

UPDATE1:

I tried the code @caveman suggested:

((unsigned char*)(&period))[0] = TCNT0L;
((unsigned char*)(&period))[1] = TCNT0H;

But the result is also not very good:

    ((unsigned char*)(&period))[0] = TCNT0L;
  dc:   82 b7           in  r24, 0x32   ; 50
  de:   e6 e8           ldi r30, 0x86   ; 134
  e0:   f0 e0           ldi r31, 0x00   ; 0
  e2:   80 83           st  Z, r24
    ((unsigned char*)(&period))[1] = TCNT0H;
  e4:   84 b3           in  r24, 0x14   ; 20
  e6:   81 83           std Z+1, r24    ; 0x01


texts: how the calculate the specific resistor in a parallel led circuit?

texts:
This is a Sequential LED flasher circuit i found in you tube.

He uses 11 leds in 5v power supply source and he connect them in parallel with a resistor 470ohms.

I try figure out how he measure this resistor but i can not.

If we assume  red leds are 2.1v and their current 20ma

11 red leds=220ma
5v-2.1=2.9v
2,9/0.220=13ohms resistor

i know i am wrong , so how he calculate the 470ohms resistor in the kind of circuits? (knight rider , led chaser etc.)


texts: Wire landphone speaker to arduino (noise problem)

texts:
Hi. I did something like the image above.
I took my phone's speaker and connected it to arduino's GND and Analog PIN 0 so my computer can detect when the telephone rings silently and notify me. (I removed the speaker)

On the arduino side, the code seems to be working fine everything looks perfect, it detects the ringing just fine.

Problem is: When I pickup the telephone I hear a horrible noise.
If I disconnect one wire and leave the other, the noise is still there! (Have to disconnect them both)

I tried adding a diod between each wire it seems to lower the noise a bit for some reason, but the noise is still too much.

How can I isolate the telephone? I just want to get the voltage reading from the speaker to detect if it's ringing or not. When I use my multimeter on the speaker it doesn't make any noise though..


texts:
I am planning on providing a system with the option of powering via USB.
Now the system will require greater than 100mA, so USB 3.0 interface will need to be used for powering the system.
The data transfer via USB will only be capable of interfacing with USB 2.0.

What is the difference between the power lines of USB 2 and 3 and can this impact my data transfer whilst being powered via "USB 3.0".
I have read something about the USB 2.0 Data pins being used for powering for USB 3.0B? Not too sure.

TL;DR
At the moment i am not sure whether my system will be able to transfer data via the USB 2.0 pins (D+, D-) whilst being powered by USB 3.0 (~900mA). SAME CONNECTOR.

Thanks


texts: How to size a resistor for use with an unmarked Zener Diode?

texts:
I want to design a simple voltage regulator circuit using a zener diode along with a resistor to protect the diode from excess current.  This is the classic zener circuit you see everywhere.

The diodes are unmarked and I don't have a spec to reference. But I know how to find the forward and breakdown voltages of the zener using a power supply and a multimeter.

Now I just need to determine the operating range of current for the diode so I can properly size the resistor.  How would I do this?


texts: Can someone help understand what these different RF power detector specs mean?

texts:
I've been looking at various RF power detectors for a project I'm working on, but I don't quite understand what the manufacturers mean by "dB range".

For example, the LT5534 Log RF Power Detector has a frequency range of 50 MHz - 3 GHz; the minimum it can detect is -63dB and the maximum is 2 dB. What does that mean?


texts: How can I use one microcontroller to increment/decrement 4 sets of LEDs using 8 push button inputs?

texts:
I want to design a very small project for a portable score keeper. It consists of using one microcontroller to control 4 sets/groups of LEDs on a small PCB. It is a very small scale project (3.5in X 1.5in). 2 of the 4 sets will consist of 4 LEDs each and the other 2 will consist of 7 LEDs each. Total of 22 LEDs but I will only need 4 LEDs to be on at one time. I would like to use push buttons to increment & decrement the score which will light up an LED. The LEDs will be labeled by score points. The smaller set will be the game score while the larger set will be the set score.

I was wondering if this was possible and how would I do this? is there a small enough microcontroller to be able to have have 8 push button inputs to manipulate 4 separate sets/groups of multiple LEDS?

I am planning to use plain 3V coin cell batteries for now but will look into small rechargeable power supplies. I have made a very simple dip-switch prototype using very tiny surface mount LEDs on a thin PCB with a coin cell battery. The dip-switch was bulky and took a lot of space. I would to slim it down and make it more sleek with less switches by implementing these ideas if they are possible.

Any words of advice and help will be appreciated. Thank you so much :D


texts: LTC4417 Power path converter not working

texts:
I am fairly new to pcb design and I am having trouble understanding why my PCB is not working. I am using a LTC4417 power path converter and a IRF7324 power mosfet to turn on an embedded system with a pair of 14.4V batteries. I have one internal battery and one swappable battery in my system.

LTC4417 datasheet
http://cds.linear.com/docs/en/datasheet/4417f.pdf

IRF7324 datasheet
https://www.infineon.com/dgdl/irf7324.pdf?fileId=5546d462533600a4015355f5e10a1b47

My system has an ON button (JP5 connection) that when shorted routes >1 V to the LTC4417 ENABLE pin that should then result in V1 (on LTC4417) being routed to Vout (on LTC4417) and the mosfet opening, thus allowing BINT_OUT to flow to V_toboard.

Problems:
The gate drivers VS1 and G1 show the same voltage so the mosfet is not opening. I believe G1 should be pulled low causing the mosfet to open.

I have shown three pictures below. The first is the schematic of the power controller section of my board.

The second pictures shows all the voltage readings on each of the LTC4417 pin when the EN pin is low.

The third pictures shows all of the voltage readings on each pin of the LTC4417 when the EN pin is high. In this scenario, V_toboard should be the same as B_int. Note: VALID1 connected to a pullup resistor and the 16.3 V reads a value of 0.4V but should read 0V when the voltage into V1 is valid.

Can you help me solve why the Vtoboard does not match Bint_out


texts: Understanding basic computer hardware diagram of address decoding circuit

texts:
Hi I'm a computer science student doing a computer hardware course and am having trouble understanding this circuit which is supposed to show how control signals at the memory can be generated using this address decoding circuit.

The explanation of the diagram is: "The generation of the necessary control signals at the memory is shown in the following circuit, which is an address decoding circuit.  It decodes the address to generate individual control signals to the different memory locations. When READ is active(0), READ0 is active(0) if ADDRESS is 0, and READ1 is active if ADDRESS is 1.  The write control signals are similarly activated".

Would someone mind helping me understand how this circuit works?  I know that the 4 gates on the right are OR gates and that to give an active output only one of their inputs needs to be active.


texts: Two voltage rails from one photovoltaic system

texts:
I'm working on designing a photovoltaic well water pumping system.

I will have two 12V 120W PV panels connected in series, for a 24V 240W output (during full sunlight).

Is it possible to connect a load in parallel to one of the panels?  In practice, will this reduce the power output of the system?

simulate this circuit – Schematic created using CircuitLab

What are the reprecussions of hooking up loads like this two a multi-panel PV array?


texts:
Is there any way to do matrix/vector algebra with analog electrical components?
Only addition, subtracting and multiplying.

I'm going to build a Linear-Quadratic-Gaussian(LQG) Controller.


texts: Finding Open/closed loop transfer function

texts:
I plan to determine the open/close loop transfer function of the attached motor. I have been able to combine K(s) to 1/s in series but am not too sure of how to add up 12/pi outside the summing junction and what to use as the gain(either tetha 0/teta 1 or teta 0/V1(s).

Also how to use this to determine the closed loop of the system


texts: ESP32 pico D4 SoC(System on Chip) Heat issue

texts:
I have designed my own PICO board using PICO D4 SoC with help of the document : ESP-PICO-D4-Datasheet. Everything works perfectly fine except heat is produced when chip is using WiFi functions.
I have tested with blink and Wifi sketch for a week and no issues found (without plastic case covered) . My plan is to put the same board behind wall switch and will have an plastic enclosure also. Only SoC chip gets heated no other components are impacted.
Is it safe to put behind wall switch?
Does simple heatsink on SoC would solve the problem?
Can I proceed avoiding this?


texts: Separating the grounds for sensitive signals

texts:
I'm designing an op amp based phono preamp. It has very high gain (60 dB for 20Hz, 40 dB for 1kHz) and the signal from phono cartridge is very low (like 5mV amplitude). So it's a very sensitive circuit.
As you may know signal from the turntable goes with coaxial cable + separate grounding wire to minimise hum and noise - current returning to cartridge has different path than noise going through the separate gnd wire.
I wanted to apply this philosophy to the input stage of my preamp - my goal is to make the cartridge return current path separate from the ground plane with all the contaminated currents that it picks due to EMI, 50Hz hum etc.
Is making a separate ground for the input stage and then linking it to main ground going to help me to lower the noise floor? I want to make the grounds separate and join them with low value resistor (like 10 Ohms to make sure that none of the "contaminated" current will flow through the phono cart return path.
I also include the schematic and PCB design.
The schematic:

PCB:


texts:
I'm completely new to electronics but my degree gives me a basic course with a project at the end.

I built this small circuit to detect when a light is shined on the LDR to turn on an LED so basically a light detector rather than a dark detector. I am simulating the circuit using LTspice but I cannot seem to get it to work.

My idea pretty much is that the LDR gives off a HIGH or LOW value to the threshold comparator then the inverse is outputted through the OUTPUT pin, since I want the inverse of that, I attached a NOT-gate to the output circuit to light the LED when the NE555 output is LOW instead of HIGH.

Like I said I am fairly new and I might over complicate this circuit for nothing, but I can't seem to find a way to make LDR change the output of the NE555


texts: Is the avalanche effect in Zener diodes a quantum mechanical process?

texts:
Firstly I would like to emphasise the word avalanche as it's fundamental to my question. I'm not concerned with shot noise, thermal noise or trash music.

There is a video that explains the avalanche effect inside a Zener diode, from which the screen grab below is taken.  In summary, the effect occurs as charge induced kinetic energy starts a cascade of electrons through the semiconductor, in a manner akin to a snow avalanche.

I believe that electrons are fundamental quantum particles so the  Uncertainty principle should apply.  By definition, this means that the exact path of the cascading electrons and therefore the overall current flow can only be modelled stochastically.  Specifically, it cannot be modelled deterministically no matter how powerful your computer is, even if it were the latest quantum machine from IBM or Google. So if you had a very large computer, a shed load of differential equations trying to model the electron trajectories, it still couldn't possibly work due to the Heisenberg effect.

Is this correct?

This is a cunningly disguised XY cryptography question. Quantum random number generators are flogged for lots of £££ and marketed on the basis that quantum randomness is more random than classic RNGs A quantum RNG might use a laser whilst a classic RNG might use avalanche noise. The marketing basically implies that diodes are deterministic /predictable given a quantum computer.  I wanted an EE perspective from inside a Zener.

Does a reverse-biased P-N junction create quantum noise does not immediately apply to my question as that only deals with low bias voltages with is not the avalanche effect. Also the accepted answer is shot noise based, not avalanche noise based and these are significantly different.


texts:
Find voltage V and current I.
As per the book, answer is (e) 3 mA, +3 V; (f) 4 mA, +1V .
But I don't know how we got there.

Edit:
For figure (e):

I understand that diode connected to +3V supply will be forward biased because the anode of this diode is connected to maximum positive voltage in the circuit.
But, I don't understand why diodes connected to +2V and +1V is reverse biased.

For figure (f):

Diode connected to +1V supply is forward biased because cathode of this diode is connected to least positive voltage in the circuit.But, I don't understand why diode connected to +2V and +3V is reverse biased.


texts: ESD/surge protection with TVS and spark gap

texts:
I made a footprint for a TVS diode with a spark gap underneath it. The standoff height of the diode is about 0.2mm.

A few questions:
Is there any benefit of putting a spark gap and a TVS in parallel?

and if so:

Will the spark gap be as efficient as it is in 'open air'?


texts:
I have the following nested struct definition in my .h file:

struct PARAM
{
    uint8_t data1;
    uint8_t data2[2];
    uint8_t data3[2];
};

struct CONFIG
{
    uint8_t data4;
    struct PARAM par1;
    struct PARAM par2;
};

In my main.c file I declare the following array:

struct CONFIG settings[100];

and I try to initialize the first element as follows:

settings[0].data4 = 0x01;
settings[0].par1 = {0x01,{0x01,0x01},{0x05,0x06}};
settings[0].par2 = {0x01,{0x01,0x01},{0x05,0x06}};

But I get the following error for the setting[0].par1 line:

  Expected expression.

Does anyone know what I am doing wrong?


texts: Nodal analysis - how to handle two adjacent supernodes

texts:
I'm a first year engineering student who has a problem with harder nodal analysis problems.

Consider the circuit in the attached image. The usual way to deal with the voltage sources in the upper left branch is to make a supernode. However, one of the nodes (node 1) is necessarily common to the supernodes. I need to know how to handle these situations with nodal analysis and without repositioning the sources. I'd be really glad if someone helped me.


texts: How to calculate the output voltage of the mirror circuit?

texts:
Please refer the following circuit added.

Output voltage (Vout-A) is measured as follows,

Following is the way I have started analysis:
Krichhoff's voltage law around the loop ( R12 -> R3 -> V_BE(Q2) -> V_BE(Q1) ) can be used to calculated the voltage across R12
This drop across R12 will be equal to drop across R3 (10 Ω)

But when measures in Ltspice, Voltage across R3 = 12.56 mV
Voltage across R12 = 23.7 mV
As per my understanding voltage - drop across the R12 and R3 will be equal, and it should be 12.56 mV.
Why voltage across R12 is 23.7 mV?
I suspect that D1 and R5 plays a role.

My intention is to calculate the output voltage Vout-A.
Could anyone suggest a method to find the output voltage Vout-A?

Edit
" it should be 12.56 V " changed to " it should be 12.56 mV".


texts: Understanding crest factor of a voltmeter

texts: I was studying signals and systems and came across the crest factor which is defined as the ratio of Vmax of the signal to the rms value of the voltage with the dc component removed. It then proceeds to says that a voltmeter with high crest factor is able to read accurately rms values of signals whose waveforms differ from sinusoids, in particular, signals with low duty factor. My question is what does this mean, as far as I knew crest factor was defined for periodic signals, how do I relate to the crest factor of a voltmeter?


texts: is it possible for the phase difference between voltage and current to exceed pi/2 in a RL circuit?

texts:
I did an experiment where I made a RL circuit. My IV was resistance and DV was phase difference between voltage and current. To find the phase difference, I took the difference (Δt) between time when voltage was maximum and time when current was maximum (I made sure time for Vmax < time for Imax, since voltage leads current in an RL circuit). To get phase difference in radians, I did (Δt/time period)*2pi. I got time period by doing 1/frequency (I used a 50Hz AC generator). But when I did all this, I get phase difference values that exceed pi/2.
Is there anything wrong I did here? If not, how is it possible (in terms of physics) for the phase difference to exceed pi/2?
If it helps, this is how I set up the circuit.

Sorry if the answer is actually something really simple. I've tried googling but found nothing. Also, please explain in layman's terms!! I'm a high schooler and we've never actually covered inductors in school.


texts: Can I use an analog input for a discrete signal field device on the A-B Micro820?

texts:
I have an Allen Bradley Micro820 (2080-LC20-20QWB) with four sinking 24 VDC analogue inputs and eight 24 VDC sink/source discrete inputs. I need one more discrete input for my project than the 8 that I have to work with (not counting the analogues).

Can I simply use one of the analogue inputs as a sinking discrete input?


texts: Cannot establish serial communication from a sensor

texts:
I have the following wind sensor (RT240):
http://www.nrgsystems.com/FileLibrary/829de7ea934944f09798ad2830abfa65/RT240_and_RT20_Manual.pdf

It has a 8 pin connection cable and I'm trying to receive/send data from a PC by using "Full duplex pin assignment" at page 9.
I want to convert RS485 to RS232 for communicating with a PC.

The point is, I'm kind of lost between protocols and interfaces in this manual.
I'm trying to use RS485 interface and I have the following converter I-7520A (at page 14):
http://ftp.icpdas.com/pub/cd/8000cd/napdos/7000/manual/7520.pdf

If what I'm trying to do make sense, here is how I connected the connector pins to the RS485 converter:

Here is how I connected the cable connector pins to the RS485 converter:

Pink (RXD-) to 5 TX-

Yellow  (TXD-) to 7 RX-

Red  (Control con.) to nowhere

Grey  (RXD+) to 4 TX+

Green  (TXD+) to 6 RX+

Blue (Analog ground) to nowhere

White  (Supply Voltage - ) to 10 and they the together to + of 24V DC

Brown  (Supply Voltage +) to 9 and they the together to - of 24V DC

First of all, when I power the sensor and the converter I can’t hear any sound from the sensor where I supposed to hear tickling sound normally. It looks like it doesn't power up unlike the converter. And I also don’t see any data from the PC serial port by using Windows HyperTerminal.

I’m really lost, could anyone guide me how I can use RS485 interface with this sensor and convert it to serial. There is also SDI-12 protocol in the manual which I have no idea about.

What I was trying to do was to use RS485 protocol for this sensor and receive send data in ASCII format. Could anybody give me a little help? It looks like I'm doing something fundamentally wrong here.


texts: A question regarding the resonant circuits

texts:
I am at the beginning of trying to understand resonant circuits, so after doing some research about the basic of resonant circuits , I noticed that there are diagrams appearing the basic working of a resonant circuit or LC circuit but there are a one small diffrence between them and that deffrence is that some diagrams shown that the power source negative stays connected to the LC circuit but others diagrams shown that the power source negative is not connected to the circuit,
I understood that for the LC circuit to work it must connect the power source to the capacitor to charge in it then deconnect the power source positive, so my question is about the negative, thank you all for any help.


texts: Difference between speed control unit of bldc motor and induction motor

texts:
Is there any difference between a speed control unit of a 3phase bldc and 3phase induction motor? (Considering the complexity in design, efficiency, weight, cost etc)

Supposing the wattage of the motor is 1.5kw -2.5kw


texts: CD4017 Decade Counter Based LED Flasher Question

texts:
I am creating a simple LED Flasher with NE555 and CD4017. I am actually dividing the pulse frequency of NE555 by five. Because I have merged each pair of the output pins to finally get 5 outputs.

I have attached 4 pieces of 3V LEDs (draws approx 200mA current each) in Series to each of the 5 outputs.

I couldn't find any error in the circuit. But when I test the circuit, I measure only 3V-5V at the five output pins. As a result the LEDs do not glow. What could be wrong in the circuit? My question is specifically around the values of resistors. Are they too high to allow sufficient current?

The circuit diagram (partial, showing only 1 of the 5 outputs) is given below.


texts:
Looking here, I am shown that the connecting symbol, means the wires are,  literally "connected" as shown below.

I am currently working on trying to decipher an FM Radio schematic, but am having trouble with this "connected" thing...

On the above schematic, I am shown that almost everywhere on the board, there are connecting wires.
Is this exactly how it's meant to be soldered/constructed? Am I meant to grab 3 wires, and just drop a blob of solder on them so that they are all connected?


texts:
I am interested in the MFI made for iPod program, and found

This $59 Cable Lets You Connect iPhone to Arduino — No Jailbreaking!

Programming iPhone Sensors Book

I have ordered the cable and will check it
But the question is how would this influence on my device working with that cable or a clone with out apple approval of MFI?

Is this apple response to android hardware dev openness?

Thanks a lot

Edit:
im interested in the software side, in the approval for the appstore, as the normal expensive approval for the MFI is not in my plans right now...


texts: Do different Line-Ground voltages on a 240v L-L PSU fed from a 3 Phase High Leg Delta system pose a problem?

texts:
I'd like to know if there are any negatives related to powering an ASIC miner PSU at 240V, 2 hots and a ground (C13 plug), from a three phase, center-tapped, high-leg delta system, when the line to ground voltages vary between the two hots going into the PSU. We can switch to an ungrounded 240V delta secondary or a 208V wye configuration so feel free to comment on that if you wish.

PSU is powered from a single phase panel that is completely wired with double-pole breakers in order to provide 240V L-L voltage (AC 60Hz).
One of the panel's hot line is the high-leg of the delta secondary, which means that the line-ground voltages from the hot legs into the PSU are 208V and 120V.
I don't have the schematics/diagram for the PSU but it's a generic version of Bitmain's APW7 PSU; 1800w 200-240V AC to 12V DC (two V+ & 2 V- terminals). Internally the ground from the C14 plug is directly terminated to one the the PCB's mounting screws.
Powered the unit up to roughly 50% load without a problem, yet (to either PSU or equipment).

Would really like to know if this setup may present problems down the line, especially when connected to other switching PSU driven equipment powered by the other phases (equivalent L-G voltage legs), be it via data cables, direct physical contact of cases, mounting racks, etc. Thanks!


texts: Problem in star delta starter in air compressor

texts:
I am a beginner in electrical engineering. I am trying to understand how motors are connected in a star and delta system.

I studied the star delta starter from this link. It describes the connection of a motor connection as in following diagram.

Above diagram shows V1 and V2 connected to the same phase through the main contactor and delta contactor.

But, this diagram does not match my real wiring. It seems to be wrong.

What is the correct wiring scheme? Is there any problem with my connection or  with the diagram in the link. I didn't check the winding of the motor. I trusted the tag on the wire.


texts: Precision rectifier doesn't give expected output

texts:
I'm currently designing a precision rectifier. I have a current sensor that outputs a current (AC) of 0.3mA to 32mA for 0-100A across a resistor of 510 ohms. As the value of the voltage will be around 0.3v for 1A of current, I can't just use a half-wave rectifier and rectifier the output and get the Dc value. I won't be able to sense current till it reached 5A or so. Hence I decided to design a precision rectifier.
The circuit is straight forward, didn't have any issue with simulation but when I actually implemented the circuit on a breadboard, I'm not getting the possible output.
The current sensor is sensing 11A current. It's outputting 2.2mA and I'm getting a voltage drop of 1.2V across a 510-ohm resistor. So far so good. Now I'm giving this voltage to the non inverting pin of LM358P. I'm measuring the same voltage at the output pin of the opamp. But when I measure the voltage after the diode (D1), I'm getting 2V for some reason. I'm getting the same 2V at the non-inverting input of the opamp too. I'm not sure where is it getting that 2V from.
When I connect the load resistor(Rl) and smoothing capacitor(C1), get 10V after the diode (D1). I'm not sure what I'm doing wrong?
I have attached the circuit to this email.


texts: Laser emitter for serial communications?

texts:
I want to build a 2-way serial communications rig using low cost LED lasers. 9600 baud would be ok, but faster speeds would be more useful. (This is purely a hobby project. The further I can establish a communications link the cooler it will be, but there is no hard requirement.)

Initially I'll probably use red LED lasers because they're easy to aim, but will eventually switch to IR. My thinking is that I will put an iR phototransistor in a parabolic reflector (like an old car headlight assembly) and put a cheap visible light blocking/IR pass filter in front (An "IR notch filter" to use signal processing terms for an optical filter) and put the whole assembly in a cylindrical tube. That way ambient light will be greatly attenuated and with the parabolic reflector pointed roughly in the direction of the sending laser even a "near miss" should be enough to generate a decent signal in the receiver, and if the beam is bigger due to being scattered over distance, the parabolic reflector will serve to focus it on my receiving phototransistor.

The dirt-simplest way to do this would be to power an off-the-shelf laser pointer through a transistor, and apply a CMOS level control signal to the gate of the transistor.

However I suspect that the voltage/current regulator on the laser pointer would tend to flatten out the high frequency switching of the power and prevent clean switching of the signal. (Most voltage regulators I've seen include one or more capacitors to flatten out the signal) Am I right in my suspicions?

I could buy a laser diode, regulator, and collimating lens and attempt to switch the output of the regulator into the laser diode, but I'm a software developer who likes to tinker with electronics, not an EE.

Are there low-cost solutions to sending digital signals with LED lasers? I'm willing to spend money on it, but would like to keep the costs down.


texts:
I am using a stepper motor for a gantry setup. When I run the motor above certain speeds, in this case 4rev/sec, it produces a high frequency sort of whinny sound. It is a 4.5A motor and I am running it with 24V.

If I run the motor at 48V, I am able to reduce the high frequency sound quite a bit, in fact I have to go up to 6rev/sec for it to be at audible/annoying levels.

My initial guess is that at 48V the stepper is able generate more torque since the current in the coils is able to overcome back EMF and rise to higher levels than in 24V. Is this a correct assumption or is there more to it?

I do not believe the motor is defective since I tried a few different motors with the same 4.5A rating and they all have a point in the speed where they begin to produce the high frequency noise.


texts: How to construct a signal with only unit functions?

texts: I don't understand the solution to this problem. How can I write a ramp function in the form of a step function?


texts:
I have humidifier power supply with a blown 2W resistor.
From what I can see the colors are red, gold, gold, orange and grey or the inverse.  I cannot tell the direction because the two external bands are in the same place.
What is strange to me is to have two gold rings in the middle.
How do I decode this resistor? It looks similiar at the one in the picture but I have an orange ring instead of red. I understand the picture is bad but I don't have a better one.


texts: Effect of switching noise on a handheld measurement device

texts:
I'm planning to make a handheld LCR meter (plus more) based on Cypress's PSoC 5LP chips. One of their many features is a built in boost converter, which seems an attractive prospect, since it would allow me to efficiently power the device from two AA cells, instead of inefficiently with a linear regulator on a 9V battery. The boost regulator supports up to 50mA of current going from 3V to 5V, with a 10uH external inductor. The regulator uses a 400kHz switching frequency.

However, the nature of the device is that it does sensitive analog measurements. In ESR mode, for instance, it generates a waveform at around 100mV, and has to accurately measure the attenuation. When measuring inductance or capacitance, it likewise has to generate and accurately measure waveforms, at frequencies from a few kilohertz up to about 1MHz.

Will I see significant coupling of noise from the boost converter into the analog signals I'm measuring? What steps can I take to prevent it - and is it practical to eliminate the noise to an acceptable degree in a handheld application with a reasonable cost constraint?


texts:
Capacitor Run Single Phase Induction Motor have very high starting currents, possibly in the order of 35-40 Amps upon startup for a 1 hp device, whereas the nominal current usually lies in the order of 4-5 Amps. How does one choose the appropriate wire gauge for the windings?
If we decide that our wire is to handle 40 amps, we will be using 8 AWG, which is probably a bit too thick for windings of a device of small size. If we use the nominal current the size could go down to 16-18 AWG.
I assume that in practice it will be a compromise between the two, but how do we know our compromised mid-sized wire is capable of handling current above its max rating? I cannot find specs on wires which give a max continuous, and max peak (and given duration). Where can I find wire with such specs?


texts:
I am looking to set up a voltage-measuring system for the output of a recently purchased HV power source. The source supplies around 0 - -60 kV DC and 10 mA to my load. Unfortunately, the source does not have a voltage measuring system, so I will be tasked in its creation. This will be of particular difficulty because I do not have enough money to purchase sufficient HV probes that could simply be attached to a multi meter. Thus, I will need a way to lower the incoming voltage from -60 kV to something manageable for the multi meter.

Currently, this is the schematic that I am considering to use in order to lower the voltage:

simulate this circuit – Schematic created using CircuitLab

The multi meter that I currently own can handle up to 660 VDC. Using my apparatus above coupled with the multi meter, would the multi meter be able handle the voltage that is delivered to it and give out an accurate reading of the line voltage (assuming that a series of calculations are performed)?


texts: Industry standard measure for coaxial cable stiffness?

texts:
Is there an industry standard measure for coaxial cable stiffness?  By stiffness I mean the spring force experienced when bending or deforming the cable.

In my search for a highly flexible lab test cable, I've been unable to find a standard measure of coaxial cable stiffness.  All the manufacturers give minimum bend radius numbers, but there doesn't seem to be any industry standard way of denoting cable stiffness.


texts:
In Host PC that have USB Type C Ports is it correct to assume that they will be implemented with PD controllers and thus :-

Use the CC lines to decide whether to provide VBUS (and in the worse case may even not provide VBUS power) ?
Once proper validation with the device connected then will be able to provide +5V upto 3A on the VBUS lines ?

Thank you in advanced


texts: calculating the total power needed by factory

texts:
Our company is planning to shift to a new site and I was tasked with finding out the required kVA power to install a PMT. I have the kW ratings, amperage, voltage and power factor for all machines and other equipment in use. Using this as a reference, I found the reactive power for all machines, then summed up the total kW ratings, summed the kVAR ratings, and used the power triangle to get the total real power.

Is this method correct? Is it 'accurate'? I was told it is incorrect and I would have to find the real power for the single-phase and three-phase machines separately, and divide the single-phase total power by 3 because it goes into three-wires. This is the first time I am dealing with a real-life design problem so help would be appreciated. If any other details are required please let me know.


texts: Connecting battery packs in parallel and series, each with their own BMS

texts:
Recently I bought cheap a lot of CASIO DT-9723LI battery packs.

Every pack consists of 2 Sony 6th-gen Li-ion 18650 cells and its own 2s BMS.
Here the question arises: Can I connect this packs parallel and series simultaneously?

My desired pack must be 6s (so 3 Casio battery packs in series) and 9p (9 Casio battery packs in parallel). I know that I could take out the cells and build a new pack with its own new 6s BMS, but that is a lot of work. On the "old" BMS PCB (from the Casio battery packs) I found two TPCS8208 Field Effect Transistor and one S8232A Battery Protection IC. Maybe it will help.


texts: Power dissipation on chip vs. Over power dissipation

texts:
I was reading this pdf regarding computation from MIT's opencourseware and on p.8 through some obscure mathematical manipulation they basically reach the conclusion that the cooler you make your chips, the less heat is dissipated and the bigger the maximum integration density can get. This seems intuitively logical to me, but their last statement piqued my interest:

  At lower temperatures, the power dissipation on chip is decreased, but the overall power
  dissipation actually increases due to the requirement for refrigeration.

For their actual calculation they used room temperatures, so I'm assuming they mean that if we try to cool the chip (to any temperature lower than room temperature), it would be obselete because the cooling itself would increase the overall power dissipation.

But I don't understand this argument. You could say the same for refrigerators. What does it matter that the overall power dissipation increases? If you cool the chips, you can increase the integration density which would lead to stronger computers. What does it matter that the heat in other parts of the system increases? I might be wrong about this, but this is how refrigerators work too, no? It's just in the laws of thermodynamics..

So an answer to this question would clarify the above statement (or say it's indeed stupid). Why shouldn't we cool chips to low temperatures in order to increase the maximum integration density?


texts: Full Bridge Rectifier with Filter Capacitor circuit

texts:
I have a problem where I have a 60 Hz sinusoidal power signal with an amplitude of 14.14 V through a full bridge rectifier with constant voltage modelled diodes (\$V_D = 0.7V\$)

The load current is \$30 mA\$ on average. I need to find the ripple voltage \$V_r\$, average DC output \$v_{outavg}\$, peak inverse voltage experienced by the diodes \$PIV\$, the peak and average currents through the diodes \$i_{dmax}\$ and \$i_{davg}\$. The circuit uses a \$250 \mu F \$ capacitor as a filter capacitor.

Since we aren't given the ripple voltage and the resistor are unknown i'm not sure how to proceed.

I have the input: \$V_1 = 14.14 V\$

Peak output: \$ V_{peak} = V_1 - 2V_d = 14.14 - 1.4 = 12.24V\$

Peak inverse voltage :\$PIV = V_1 - V_D = 14.14 - .7 = 13.44 V\$

$$i_{davg} = i_{loadavg}  (1 + \pi\sqrt\frac{V_{peak}}{(2V_r)})
= 30 mA  (1 + \pi\sqrt\frac{14.14}{(2V_r)})$$

$$i_{dmax} = i_{loadavg}  (1 + 2\pi\sqrt\frac{V_{peak}}{(2V_r)})
=  30 mA  (1 + 2\pi\sqrt\frac{14.14}{(2V_r)})$$

$$V_r = \frac{V_1 - 2V_D}{2fRC} = \frac{14.14 - 1.4}{2 \cdot 60 \cdot R \cdot (250\times10^{-6})}$$

How do I solve for \$V_r\$ without knowing the resistor? And where else do I go from here? Is what I have correct so far?


texts: LM2577 based boost converter board gives random shut-downs with a 3.7v Li-Po

texts:
I recently bought a LM2577 based boost converter board from dfrobots.com such as the one below.

I'm trying to use it to generate a stable 5v from a 3.7v 2100mAh Li-Po battery. The Li-Po voltage was now at 4v when I wired up the circuit. I connected it to power an android mini-PC (mk808/802 type, RK3188 based). The mini-PC worked for 15-20 minutes and suddenly shut-down, even the boost converter shut-down. It happened everytime I tried, sometimes within a few seconds.

The reason of shutdown was that it was getting ~0.6v at its \$V_{in}\$ pin which is weird since there is a Li-Po battery at 4v already connected to it, connections are firm, contacts are also good so it's not a connection/contact issue. It's not even a battery issue, I tried it with various batteries, same outcome. I use a standard micro-USB cable to power it, I just cut the cable and connected power and ground wires of USB cable to the same on the bost-converter board.

I just don't get what the reason for this ghostly 0.6V is? I highly doubt it might be due to some capacitor or the LM2577 itself, I don't know what it is, but it's totally annoying.


texts: I wanted to convert 0-1v, 2ns pulse to 0-7v, 2ns pulse

texts:
I wanted to generate a 2ns pulse width signal in particular 2ns ON time and 6ns OFF time signal. I can generate a 0-1v signal having 2ns pulse width using FPGA(by any means we cannot have more than 3.3v from FPGA). And now I wanted to use the 1v, 2ns pulse width signal to generate 7v signal of same pulse width. I have tried using BJT as a switch with Vcc 7v in different configurations but could not amplify the signal. I would like to have some ideas to solve this problem out.
:> Is there any way to generate a 2ns pulse signal just like using 555timer.


texts: How to keep circuit powered when battery disconnected for short time

texts: In an assembly, I'm using spring loaded pins to connect a battery to a circuit board.  It's possible from dropping the assembly that power may become disconnected for milliseconds at a time from the shock of dropping it. I have a capacitor bank that holds a charge for 30+ms when the positive node of the battery is disconnected.  The problem is I don't think the capacitors will have any affect if the negative battery terminal is disconnected, or both at the same time because there will not be a complete circuit.  Is my logic flawed?  Is there a better way to do this than using a capacitor bank?


texts: Modifying an Old Projector with LED Bulb

texts:
I have an old projector I'm converting to LED just for fun.
I've bought an 11000 lumen, 100 watt LED.  I'd like to wire this directly into the housing unit for the old light, using the connectors from the original bulb with a step-up or step-down board to reach the 30V needed for the LED.  However, I'm having trouble finding out the voltage that went to the original lamp.
The manual (https://www.manualslib.com/manual/720744/Sharp-Xg-Mb70x.html) for the projector (Sharp XG-MB70X) says it's a 275W bulb, but doesn't list the voltage/amperage that I've been able to find, though I've had trouble with understanding many of the diagrams in there, being new to this community and just beginning the long journey to understanding electrical diagrams.
Is there a way to find this out?  I would just test it but thanks to numerous failsafe switches getting a Multimeter in there while it's actually running isn't possible without drilling holes through the housing.
Also, as a followup, I'm worried about the heat produced by the LED vs the original bulb.  Any thoughts on the difference in heat between a 100W LED and 275W mercury bulb?


texts:
I've read lot of topics here.
I read some people saying I prefer to "have CMOS characteristics" & so on
, also in some data sheets (like AVR), they say it have CMOS characteristics, etc...
I remember once "CMOS compatible" word?

So why having "CMOS characteristics" makes people proud?


texts: How can I choose an absolute encoder with appropriate resolution?

texts:
I have a motor that runs between 3 to 3000 RPM. The drive update time is 2.2 micro seconds. What is appropriate an encoder resolution for this work (especially for lower speeds) so the drive could update the motor at each 2.2 micro second without missing signals and instability?
Is there anyway that I demand to update data at longer time (more than 2.2 micro seconds) by same drive?
here is the part of a white article written by siemens group. I did my calculation based on this.

and the results of my calculation are as shown below

here is the drive specifications


texts: What is wrong with my Arduino 7-segment display code?

texts:
I am trying to make some Arduino code count on a 7 segment display. I have the wiring all right but this code will not delay one second and go to next function. Any ideas?

/*
  Blink
  Turns on an LED on for one second, then off for one second, repeatedly.
  This example code is in the public domain.
 */

void setup() {
  // initialize the digital pin as an output.
  // Pin 13 has an LED connected on most Arduino boards:
  pinMode(3,OUTPUT);    pinMode(4,OUTPUT);    pinMode(5,OUTPUT);
  pinMode(6,OUTPUT);    pinMode(7,OUTPUT);    pinMode(8,OUTPUT);
  pinMode(9,OUTPUT);
}

void n0() {
  digitalWrite(3,LOW);  digitalWrite(4,LOW);  digitalWrite(5,LOW);
  digitalWrite(6,LOW);  digitalWrite(7,LOW);  digitalWrite(8,LOW);
  digitalWrite(9,HIGH);
}

void ndash() {
  digitalWrite(3,HIGH); digitalWrite(4,HIGH); digitalWrite(5,HIGH);
  digitalWrite(6,HIGH); digitalWrite(7,HIGH); digitalWrite(8,HIGH);
  digitalWrite(9,LOW);
}

void loop() {
  n0();
  delay(1000);
  ndash();
}


texts:
The problem is how the phase φ effects the outcome when the input(message signal) is the DSB-SC LSB.
It's :
message: \$m(t)=A_{m}cos(ω_{m}t)\$
carrier: \$c(t)=A_{c}cos(w_{c}t)\$

I found that the LSB through the DSB-SC
\$DSB(t)=A_{c}A_{m}cos(ω_{m}t)cos(w_{c}t)=(A_{c}A_{m}/2)[cos((ω_{m}-ω_{c})t)+cos((ω_{m}+ω_{c})t)]\$

The component \$(A_{c}A_{m}/2)[cos((ω_{m}-ω_{c})t)]\$ is the expression for the LSB(t)

So the LSB(t) gets mixed with a Local Oscillator
\$LO(t)=Acos(w_{c}t+φ)\$
and the output d(t) passes through an Ideal LP Filter and the y(t) signal comes out of LPF.
So I've reached that:
  y(t)=\$(AA_{c}A_{m}/4)[cos((ω_{m}t+φ)]\$

I have reached at a dead end trying to understand the effect of phase φ when:
φ=(0,π/4,π/2,3π/4,π)


texts:
I have a code where I don't understand parts of the I2C protocol.

The code below is a part of the code to read a bit from the bus

  if (SDA==1)
  {
     i_byte = (i_byte << 1) | 0x01;
  }
  else
  {
     i_byte = i_byte << 1;
  }

Why is the ORing with 0x01 done ?

The code below is a part of the code to write a bit from the bus

  if(o_byte&0x80)
  {
     i2c_high_sda();
  }
  else
  {
     i2c_low_sda();
  }

Again ANDing with 0x80 is done for what ??

The passed parameters for writing are 0x00, 0x90 and 0x91. I understand that 1001 is the allocated address group for the ADC PCF8591F but what is 0x00 and 0x91 for ??

I have searched the complete the THE I2C-BUS SPECIFICATION VERSION 2.1 but I find no reference to these hex numbers. Am I missing some other resource that I need to read ?


texts: How to set up Keil Logic Analyzer to read specific pin?

texts:
How can I set the Keil uVision 5 Logic Analyzer so that I can read the status of a specific pin, example high or low?

I have read the official docs here, however it does not say anything of the sort. I know it can be done as I had seen a demonstration which ustilised this useful function, but can't remember how.

Let us say I want to monitor pin 10 on port 0. I have tried many variations such as:

PINSEL0<<10
0<<10
P0.10
, however I keep getting the same error message below. Any help on how this can be done?


texts: What is the speed of a baud rate? - RN42

texts:
After wondering/researching about this for days, I finally ask this question: What is the speed (bits per second) of a bluetooth SPP RN-42 device? Is 1 baud = 1 bit (thus 9600 baud = 9600 bits per second) or 1 baud = 1 packet (9600 baud = approx. 9600 * 8 bits = 96000 bits per second)?

The data sheet says: "Sustained SPP data rates: 240 Kbps (Slave mode), 300 Kbps (Master mode)" but do they mean BAUD per second or BIT/BYTE per second?

Any help would be appreciated!


texts: 2n2222 NPN low side switch not working with 31V

texts:
I'm attempting my first slightly more advanced circuit and failing. I have a led string which I'm powering with a 31V 0.21A power adapter that came with it. Now I'm trying to switch it on and off with a 2n2222 NPN transistor which I'm controlling with a Raspberry Pi 3.3V GPIO. Initially, I had an optocoupler in there also to keep my Raspberry safe but took it away to confirm it isn't the problem.

I have connected the emitter to ground, collector to the LEDs and the GPIO to base via two 220 resistors, achieving 440 ohms.

Now, putting the GPIO to high or low doesn't affect the lights (at least noticeably). Instead, the lights are steadily burning with a faint glow. Removing the GPIO from base pin turns off the lights completely. I'm having a hard time understanding what's going on.

Some questions that might solve this:
I based my resistor calculations on this tutorial assuming 100 hFE. I'm not sure about the hFE value. The 2n2222 datasheet doesn't really tell what it is with 31V and 0.21A. Any help here?

The 31V is quite high (weird choice by the light manufacturer in my opinion) but the transistor can handle up to 40Vce and 1A. Am I misunderstanding something here?

One option is that I somehow got high and low the wrong way. Does the behavior sound like it could be caused by an inversed circuit?

Solution
Thanks to @WillDean I realized I was using two grounds which was messing up a whole lot of things. I didn't realize this is an issue before the obvious was stated.


texts: what could happen if i touch the two electrical wires of a 120 v with my hands?

texts:
In my house there is  2 wires the black one and the red one, what could happen y for example I touch both wires with my hand. we have 120 V, Pd. somehow we tried to install a lamp there but didn´t work.
I have googled it and it says that if i have sweety hands i will get only 12 mA that will hurt me but it won´t be fatal
so what could happen?


texts: closed loop gain and bandwith calculation

texts:
For school I have to solve this schematic (For connection 7), but I have no idea how to do this.

They ask me to calculate the bandwith and the Closedloop gain in dB.

Edit: High Resolution Image


texts:
I am trying to fit all three modes on of 555 timer on a breadboard. But no matter what I do I am not able to get it to work on a single breadboard. When I move the circuits on different breadboards they work as expected. Is there something wrong with the voltage supply? I tried powering my BB with Arduino 5V  pin, but no luck.

The weird thing is that when I power up two breadboards with jumper wire the circuits still work. I would really appreciate if someone can tell me what is wrong with these circuits.

EDIT - Added schematic

simulate this circuit – Schematic created using CircuitLab

EDIT
Here is a link to what I am trying.


texts: How are current and voltage related to torque and speed of a brushless motor?

texts:
I know that electric vehicles have different performances depending on battery and motor, but it's not clear how electrical and mechanical units are related.

Can anybody please help?

Will a 100V motor raise against slopes better than a 50V motor?


texts: How to derive the torque expression for a BLDC?

texts:
How can I derive the torque equation for a star-connected, brushless DC motor, given its back-emfs waveforms and currents?

I'm currently reading the article A Park-like transform for the study and the control of a non-sinusoidal brushless DC motor, in which the author presents the equation for the torque in a star-connected, BLDC:

$$ T = p.(\phi'_{ra}.i_a+\phi'_{rb}.i_b+\phi'_{rc}.i_c) $$

in which

\$ T \$ - Electromagnetic torque
\$ p \$ - Number of pole pairs
\$ \phi_{rx} \$ - Rotor flux induced in the stator phase '\$x\$'
\$ i_x \$ - Current in phase '\$x\$'

However, the only introduction to the above formula is that "through an analysis of the consumed power by the machine, we can deduce the electromagnetic torque expression, assuming constant airgap", no more explanations, nor sources. Additionally, it is unclear to me whether the \$'\$ in \$ \phi' \$ denotes differentiation in respect to time or in respect to the electrical angle (I suppose it's the latter).

If someone could walk me through the process described by the author, or at least clarify it a bit I'd greatly appreciate.


texts: Evaluate power and efficiency in opamp, exercise

texts:
Can you help me with this exercise?

An amplifier operating from a single 15-V supply provides a 12-V peak-to-peak sine-wave signal to a 1- kΩ load and draws negligible input current from the signal source. The dc current drawn from the 15-V supply is 8 mA. What is the power dissipated in the amplifier, and what is the amplifier efficiency?

My solution (wrong);
Pload = (12V / Rload) * 12V
Psupply = 15V * 8mA
Pdiss = Psupply - Pload
New solution;
Vorms = 12V / (2*sqrt(2)) = 4.24V
Pload = (Vorms / Rload) * Vorms = 0.618 mW
Psupply = 15V * 8mA = 120 mW
Pdiss = Psupply - Pload = 119.4 mW
Efficiency = (Pload / Psupply) * 100 = 0.515
I think it is still wrong, the results seem too bad.


texts: Calculating current in one branch of circuit

texts: I want to calculate the current labeled in the diagram \$i\$. I am thinking that since there is 3V it would be as straightforward as \$\frac{3V}{6\Omega}\$ for the current in that branch labeled. Is that the correct thinking or am I missing some concept? I see that there is 2A being delivered as well, but would that change my answer?


texts:
I am hacking some old phones into my arduino project. I am currently controlling all of the ringers, dials, and hooks through my board.

At a certain point, I would like to connect the two handsets and let them function kind of like a basic intercom. There are four wires into each handset, two for the microphone, and two for the speaker. As I understand it they function much like any cheap microphone or headphones you could plug into your computer.

My initial thought is that I could just connect the mic of one to the speaker of the other, but I don't know audio circuits very well and am not sure if additional circuitry or op-amps would be required. What is the simplest way to do this?

Also, what would be the best way to toggle this connection, so I can control if the lines are open or closed?


texts: Cascade multiple Full-bridge Rectifiers Connected to Multiple AC Sources

texts:
I want to rectify multiple isolated AC signals (Generated from multiple wireless power receiving coils) to a single DC load. For example, consider the following the schematic with two voltage sources \$V_1\$ and \$V_2\$ representing two wireless power receiving coils. \$V_1\$ and \$V_2\$ are at the same frequency (say around \$500~\rm{kHz}\$) and same phase.

simulate this circuit – Schematic created using CircuitLab

Question One:(solved more or less from the answer by @AndyAka and the other comments)

Will this circuit works even if the magnitudes of \$V_1\$ and \$V_2\$ vary significantly? For instance, the magnitude of both sources can vary between \$5\$ V to \$20\$V independently.  Is there any better topology?

Question Two

2. How do we calculate effective AC load impedances seen by two sources (i.e. \$R_{L1}\$ and \$R_{L2}\$)?

For example, if we have a single rectifier, we know its equivalent ac-side impedance is \$\frac{\pi^2 R_L}{8}\$[reference]. Now the question is, how can we calculate the equivalent impedance seen by two AC sides (see schematic \$R_{L1}\$ and \$R_{L2}\$)?

Here is my approach so far:
Both ac links will have the same current. Therefore, equivalent load impedances should be proportional to the voltages, i.e. \$\frac{R_{L1}}{R_{L2}}=\frac{V_1}{V_2}\$. But what will be their values? is \$R_{L1}+R_{L2}=\dfrac{\pi^2 R_L}{8}\$?
If this way of calculation is correct, I have another problem because of my \$V_1\$ and \$V_2\$ also dependent on the equivalent load impedances \$R_{L1}\$ and \$R_{L2}\$. In this case, do I have to use an iterative method to solve this problem?


texts: How drift current is independent of bias voltage in semiconductors?

texts:
According to my textbook:

The drift current is relatively insensitive to the height of the potential barrier. The reason for this anomaly is the fact that the drift current s limited not by how fast the carriers are swept down the barrier but rather by how often.

From what I know, the drift current(let's say for holes) is given by, $$\vec J_p=pq\mu_p\vec E$$ where p is hole concentration, q is a charge, \$\vec E\$ is the net electric field and \$\mu_p\$ is hole mobility. The net electric field here is the vector sum of the applied field(due to bias) and the built-in field due to the donor and acceptor ions.
Even when there is no bias and the junction is at equilibrium, the above equation still holds. In fact, at equilibrium, it can be said that \$\vec J_{diffusion}+\vec J_{drift}=0\$ and the expression for \$\vec J_{drift}\$ is derived from the above equation.
So I don't understand how the electric field does not affect the drift current.
PS: It may be that I'm wrong about \$\vec E\$ being the net electric field(while it should be the
built-in electric field). But even then, I don't get how the applied electric field(due to the bias) does not affect the drift current.


texts:
I have a MAX232 IC wired to a PIC24FJ64GB110 on pin32 (TX) and pin33 (Rx), Clock = 16 MH. This is the code:

_CONFIG1( JTAGEN_OFF & GCP_OFF & GWRP_OFF & COE_OFF & FWDTEN_OFF & ICS_PGx2)
_CONFIG2( IESO_ON & FCKSM_CSDCMD & OSCIOFNC_OFF & POSCMOD_HS & FNOSC_PRI & PLLDIV_DIV2 & IOL1WAY_ON)
_CONFIG3( WPCFG_WPCFGDIS & WPDIS_WPDIS)

void InitUART1(void)
{
    // configure U2MODE
    U1MODEbits.UARTEN = 0;  // Bit15 TX, RX DISABLED, ENABLE at end of func
    U1MODEbits.USIDL = 0;   // Bit13 Continue in Idle
    U1MODEbits.IREN = 0;    // Bit12 No IR translation
    U1MODEbits.RTSMD = 0;   // Bit11 Simplex Mode
    U1MODEbits.UEN = 0;     // Bits8,9 TX,RX enabled, CTS,RTS not
    U1MODEbits.WAKE = 0;    // Bit7 No Wake up (since we don't sleep here)
    U1MODEbits.LPBACK = 0;  // Bit6 No Loop Back
    U1MODEbits.ABAUD = 0;   // Bit5 No Autobaud (would require sending '55')
    U1MODEbits.RXINV = 0;   // Bit4 IdleState = 1
    U1MODEbits.BRGH = 0;    // Bit3 16 clocks per bit period
    U1MODEbits.PDSEL = 0;   // Bits1,2 8bit, No Parity
    U1MODEbits.STSEL = 0;   // Bit0 One Stop Bit

    U1BRG = 9;  // baud rate

    // Load all values in for U1STA SFR
    U1STAbits.UTXISEL1 = 0; //Bit15 Int when Char is transferred (1/2 config!)
    U1STAbits.UTXINV = 0;   //Bit14 N/A, IRDA config
    U1STAbits.UTXISEL0 = 0; //Bit13 Other half of Bit15
    U1STAbits.UTXBRK = 0;   //Bit11 Disabled
    U1STAbits.UTXEN = 0;    //Bit10 TX pins controlled by periph
    U1STAbits.UTXBF = 0;    //Bit9 *Read Only Bit*
    U1STAbits.TRMT = 0;     //Bit8 *Read Only bit*
    U1STAbits.URXISEL = 0;  //Bits6,7 Int. on character recieved
    U1STAbits.ADDEN = 0;    //Bit5 Address Detect Disabled
    U1STAbits.RIDLE = 0;    //Bit4 *Read Only Bit*
    U1STAbits.PERR = 0;     //Bit3 *Read Only Bit*
    U1STAbits.FERR = 0;     //Bit2 *Read Only Bit*
    U1STAbits.OERR = 0;     //Bit1 *Read Only Bit*
    U1STAbits.URXDA = 0;    //Bit0 *Read Only Bit*

    IFS0bits.U1TXIF = 0;    // Clear the Transmit Interrupt Flag
    IEC0bits.U1TXIE = 1;    // Enable Transmit Interrupts
    IFS0bits.U1RXIF = 0;    // Clear the Recieve Interrupt Flag
    IEC0bits.U1RXIE = 1;    // Enable Recieve Interrupts

    U1MODEbits.UARTEN = 1;  // And turn the peripheral on

    U1STAbits.UTXEN = 1;
}

void __attribute__((interrupt, no_auto_psv)) _U1RXInterrupt(void)
{
}

void __attribute__((interrupt, no_auto_psv)) _U1TXInterrupt(void)
{
}

void main()
{
    RPINR18bits.U1RXR = 8;      //RP8 --> U1Rx
    RPOR4bits.RP9R = 3;
    InitUART1()

    while (1)
    {
        putcUART1(0x64);
    }
}

I did not receive anything from it. what I am doing wrong here?


texts:
How can I design a circuit which utilizes a photo-transistor to make a light sensitive switch that is when there is no light in room, the led connected to the photo-transistor lights up and when there is light in room, the led connected to Phototransistor turns off? Any schematic or circuit diagram would be really helpful.

Here is the link but I am using photo-transistor but this circuit is for LDR, so how can I use photo-transistor in this circuit?

Here is my Implementation on breadboard. Please tell me if this is correct. I tried to make the two lines in parallel. I suspect my connectionof base of the transistor with resistor is wrong, correct me if I am wrong.SORRY I DID NOT HAVE ANY OTHER SOFTWARE TO SHOW MY IMPLEMENTATION SO PLEASE NEVER MIND :).


texts: Application notes and sources for supplying a Micrcontroller in a power supply

texts:
I'm currently developing a project, where I have to design SMPS using a digital controller.

The system is supposed to supply the microcontroller during operation. But the microcontroller still needs a supply to start up the system. I was told there were methods to supply the microcontroller during start up, which later gets turned off when the SMPS is fully operational.

Right now I am having a hard time finding any sources or applications notes that describes these methods.

Edit 1:

The microcontroller used is STM32l4R5-p with an input range of 1.71 to 3.6 V_DD when using internal LDO. But the whole SMPS project has an input range of 115 to 230V RMS ±10%, which I know is a bit of a challenge.


texts:
Consider you have two devices designed to be I2C masters in same bus. However, only one of them is operational at a time and the other one is completely powered down. In my case the devices have internal pull-ups on SDA/SCL so when one device is powered off, it'll effectively kill the whole bus which is obviously not good.

It should be super simple to just severe powered down device's SDA and SCL lines from the bus when it's VCC is low, and re-attach them when it's VCC is high. Like a relay switch. But when I try to google for what I think I need, I get some big mains voltage relay stuff which (while I guess it could work) is a bit too dumb for my taste. My devices and I2C bus are 3v3.

There must be a word or technical term I'm missing here. What am I looking for and where to buy one piece of that component?


texts:
I found this weird component at a resale store. I feel like it is some sort of pick up, but I'm not sure. Lots of things could have a quarter inch TS cable coming out of it and there are no markings on it whatsoever (save for a small "26" on the suction cup section, which I feel like is just for the suction cup).

The weird thing is that the swivel bracket uses a hardened bolt.

I feel like this thing isn't meant to bear any seriously high loads or anything.

What do you think it could be?


texts:
I am just getting started out learning electronics and I keep finding myself having to order capacitors and transistors and other parts for simple projects.

What are the best starter sets for a beginner? i.e. who sells a good set of capacitors for a newbie? transistors, resistors, LEDs, etc...

Im interested in both complete sets (that includes different types), as well as individual sets (say, for just capacitors).

Ideally, the kits are weighted toward pieces that you will use more often.

Any suggestions?


texts:
I'm trying to determine whether it is more appropriate to place an LED in series or in parallel with a solenoid.  The application is to monitor the solenoid, i.e. if the solenoid is burnt out, the LED turns off giving indication that the solenoid is burnt out.  I am using 24Vdc source.

If I connect the LED in parallel with the solenoid, my concern is that the LED is of much less resistance than the solenoid, and the current will take the path of least resistance.  Thus bypassing the solenoid.

If I connect the LED in series with the solenoid, I am unsure how the solenoid acts if its "burnt out."  Will it be equivalent to an open circuit or a short?  If it is open, then the LED would work as there is no continuity in the circuit, but if the solenoid is shorted, the LED indication would remain turned on.

Can all this be explained with Kirchoff's laws?


texts: What is wrong with my L7805CV + BUF 654 NPN transistor circuit

texts:
I really can't understand why this circuit get so hot and it does not turn on my LED strip (2 x 3 RGB leds).

I use a L7805CV voltage regulator, a BUF 654 NPN transistor. I have check the regulator and it works fine when it's not connected to the transistor, but I get strange low readings when I hook it up to the transistor. Taking out the 5V wire and connecting it again blinks the LED strip shortly.

Black wire: 12V
Red, Blue & green wires: color led GND

UPDATE

A lot have requested the schematics

I'm new at hobby electronics and don't find schematics that helpful - yet.
The LED strip has a lot of build in resistors.

I will use a ATtiny85 (arduino mini chip) to turn on the transistor - it has 5 V in and outputs - so will supply it with 5V from the L7805 and do some logic turn on (via the transistor) and PWM on the LED strip.


texts:
How to calculate this capacitor on pulse transformer primary?

I've tried 470 nF but the PWM on capacitor's output lost its level, normally both PWM are 0 to 12V, but when I put this cap, the PWM on cap's output becomes -5V to 7V (even when I disconnect the transformer). I don't know that's wrong with it. Frequency is 30 kHz.


texts:
Supposing I have a small solar panel rated at 5V and a supercapacitor rated 5.5 V 1 F, would it be possible to charge the cap fully?

Or in general, can a cap be fully charged with a low current, constant voltage source?


texts: Please help me understand how this inductive proximity sensor works

texts:
I'm trying to build out an optocoupler circuit to connect a new proximity sensor to my 3D printer and want to understand how it behaves before implementing.
It's a Printrbot Simple Metal,  Printrboard R5, and the stock Z-probe is a 4mm inductive sensor,  LJ12A3-4-Z/BY - PNP N.O, and this plugs directly into the input on the board.  It's a 12V system, and this particular board is fine with 12 V on the Z input.
The old probe gives me 0 V from Black to Gnd when not activated, and when activated gives the full 12V.  Makes sense, normally open (no current flow), and when triggered, closes and gives a 12 V signal.
I have the circuit outlined below and it works the way I want - when the proximity sensor picks up metal nearby, the 817 is triggered and my output works (Led turns on). The new probe - LJ18A3-8-Z/BX is NPN NO with an 8mm sensing distance.  When not triggered it gives me 12 V from black to ground, and when triggered gives me 0.7V black to ground.  So basically a gives a low signal when triggered.
With the optocoupler, I think what's happening is this:
black is 12V when not triggered,  high on input, PIN 1,  basically both at 12V, no current flowing from black to GND.  And when the sensor is triggered, the black line goes low (12v - 0.7 for the transistor in the sensor), so I get a positive potential diff from black to ground, triggering the 817.
Does this sound right?
Also, I can't for the life of me figure out a configuration that would use the old sensor (high signal) with the same 817. Any thoughts? I gather I can't easily have a simple (same) circuit that works for both and probably need a jumperred gate to invert the signal for the old sensor and bypass that gate when using the new one.


texts: Can I use MOSFET to output big current with small voltage?

texts:
I search online for the usage of (power) MOSFET and it leads to some chip like STE250NS10. I read the manual and it show the schematic diagram like

In the manual, there are several tables to illustrate the output characteristics. One of them tells the change of drain current against voltage of drain and source if we fix the voltage between gate and source. I am going to output about 20A current with small voltage. I didn't use MOSFET before and I don't know if I should fix the voltage of gate and source then change the voltage b/w drain and source to output the desire current. But if I did that, I need the drain-source voltage about 0.14. However, the curve is so steep so even I increase the drain-source voltage by 0.2, the current change to about 100. So I wonder what's the good way to use the MOSFET for current control. I don't have any experience in using MOSFET, so which pin is the gate, source and drain in about diagram and if 1 and 4 are connected, why we need to separate them into two pin? Thanks.


texts:
Can I connect an rs232 Ethernet converter to a switch and expect to receive a data on a php server listening to the of IP conversor?

In windows I need to install drivers to create a virtual com, so I guess if I connect a converter directly to a switch it will not work?


texts: Ambient Light cancellation on Pulse Oximeter

texts:
I'm  trying to build a pulse oximeter using TSL2305 LTF sensor and 2 LEDs(Red and IR).
The desired graph expected from the light are plotted correct but I want to know whether there should be any ambient light cancellation from the obtained values of red and IR lights to get an accurate result.
For now the red and IR lights are toggled at an interval of 10ms , should an OFF time of both the lights be added in between to acquire the ambient light that must be subtracted from the red and IR light so detected?


texts: Can a multi-secondary transformer be used with a full wave rectifier?

texts:
I got this board and from what I see, it should be used with a center tapped transformer with 0-9-18 as secondary because it uses a full wave rectifier:

I have a normal transformer with 4 secondary pairs:
18-0 18-0 9-0 9-0

Is it possible to use this transformer with the before mentioned board? Any suggestion?


texts: Switching between two sources of power to a battery?

texts:
This is the simplified system:

a battery (3.6 V, 2450 mAH, NiMH)
a solar panel (max 5.2 V, 157 mA)
a wall charger (5 V, 2100 mA).

The battery is constantly being drained, but very slowly (85 mWh per day).

The solar panel produces 62.5 mWh per day on an average day (7 hours of low sun at only 8,000 lux).

This sustains the system for a little over a year if we assume everyday is an average day (without solar the batteries drain in a few months).

The wall charger is only used once a year to quickly replenish the batteries back to full, so the system can last another year.

Every few years the batteries will have to be replaced.

I want these scenarios to happen:

If wall charger is not plugged in, trickle charge battery with solar panel only.
If wall charger is plugged in, stop charging with solar panel and fast charge the battery only with wall charger.

How do I switch between the two scenarios?


texts: Verifying schematic ideea: Circuit design for mosfet driven by ESP32

texts:
I have an ESP32 that I will use to drive open a solenoid valve. The Mosfet I will use is a IRLZ44N which is best operated at 5V (I think that the 3.3V voltage, although is above the Vgs(th), will be insufficient). My circuit therefore uses 3 voltages: 3.3V generated by the built-in regulator, 5V and 12V provided by a PC power supply.
I read on some forums that at a high frequency the mosfet's capacitor can damage the IO pin with the inrush current. Because I will use the PWM of the ESP32 at about 500Hz in order to lower the power consumption of the valve I am afraid that I could fry the pin used.
This is the circuit I came up with:

simulate this circuit – Schematic created using CircuitLab

R2 is the valve which draws about 5W
Q1's base is pulled up by R4 so that the mosfet is not conducting when the MCU is initializing. The collector current should be limited to 80mA which is lower than the absolute 100mA for this bjt.
R1 is an "artifact" from the time when the Mosfet gate was directly connected to the IO pin. I am not sure if it would do anything in this circuit as the power supply is pretty beefy and thus should handle the inrush current.

My aim is to use as little resistors as possible without the risk of burning the ESP32. Is this circuit safe even without that R1? Will discharging the gate capacitor through the bjt at the PWM frequency affect it?


texts: Running Two Network Points From one Cable

texts:
I would like to run one 12 core cable (as seen on this link) though a conduit.

Would I be able to connect two RJ-45 Connections to the two ends? I know that Twisted pair cable would be better, however i would like to know the minimum cores required (since i expect that i could use some of the cores as a common earth?)

I would not like to use a switch or hub on the other end. Is this idea viable, and are there alternative suggestions? in essence I do not have space to run two coaxial cables in the conduit..

Thanks!


texts:
I was reading some notes about a microstrip line. Here the scheme with the reference system:

In this scheme (sorry for the bad quality of the picture) the upper strip is represented as a charge sheet between two different dielectrics (air, with permittivity epsilon0, and the inner dielectric, with permittivity epsilon1).

In these notes there is this boundary condition (together with others):

Do you know the reason for that? Why the voltage between the strip and GND plane should become 0 if y tends to infinity?

The quantity V(x,y) is defined as a function such that E = -grad (V) (this approximation is true for low frequencies, in which we may assume a TEM propagation mode)


texts: I have been asked to continue an unfinished project using Sigfox ATA8520 transceiver and Arduino DUE board. There are some LEDs and buttons on the board which I think are used for selecting different modes on the board. When I turn the board on, I see that the LEDs are driven through transistors that randomly turn on without touching the board. These LEDs do not glow quite dim but bright enough to see in a well lit room. What could be causing it and how can I fix it?


texts:
What kind of techniques are used to enable a user to safely upgrade a device firmware post sale? I want to do this with a Cortex M3/4 microcontroller, but I guess techniques for any micro should do.

Preferably with the least amount of extra components of course.