texts: Audio transformer for 12V light emitting circuit

texts:
I'm working on transmitting audio through light using amplitude modulation of an LED, received by a solar panel connected directly to an active speaker. Something like this:

simulate this circuit – Schematic created using CircuitLab

I only have rudimentary understanding of analog electronics (I work mostly with software), so I'm wondering which transformer that should be used. The schematics I find online are all for a 9v or 3v circuit, but since I need a strong light, my LED is 7W 12V. Is an 8 ohm to 1k ohm the correct one? What's the equations for audio transformers and voltage? I only seem to find voltage converter circuits and equations when searching for this online.

The circuit contains parts I already own (LED and solar cell), but I'm happy to order other types if need be.

EDIT:
Here are a couple of projects using this technique:
http://www.instructables.com/id/HOW-TO-Send-AudioYour-Voice-Over-a-Beam-of-Light/?ALLSTEPS (photoresitor instead of solar cell)
http://asd.gsfc.nasa.gov/blueshift/index.php/2013/01/22/try-it-at-home-turning-sound-into-light-2/ (No transformer)


texts: Converting an electrical schematic into a physical panel layout

texts:
I'm an undergrad researching physics, my job has been to make this electrical schematic, can I get some help figuring out the physical layout?

I've basically self-taught myself enough of solidworks electrical to make this drawing, along with how to make/read electrical diagrams, etc, so I am unsure if my drawing follows any conventions, or if I'm missing something that's obvious.
With that said, the system I'm working with is a series of 24 VDC ultra high vacuum solenoid valves, which need to be toggled off and on with secure switches, with lights indicating their positions, and some of the valves can only be turned on/off if other valves are turned on/off, so I've been using relays to accomplish that.
I have 13 relays, all basically the same, a power supply, and a linear feedthrough manipulator (the motor symbol). These are the relays I'm using, and their sockets. Along with the 8A 24VDC power supply here. I have many questions about what's going on with the data sheets and specifications for this specific power supply, but I feel like the nature of that question has more to do with navigating the purchasing of components, and less to do with their arrangement.
While looking for a power distribution block, I ended up deciding on these ones on amazon.
However, I am very unsure of that decision, and I don't know if there's more to choosing a power distribution block than finding one with the right number of inputs and outputs that supports the voltage and current I need.
The part that I am now having trouble with is the physical layout of this system. I am unsure how to mount the switches onto the cabinet. I tried looking at some supply places online, but their inventories are so massive and unorganized that it is difficult to tell if there are products out there made for switch mounting. I was imaging some kind of panel I could plug the switches into, and then wire them from the back, but I am now thinking I will need to drill holes in the door of the cabinet. I also don't understand how I'm supposed to arrange and use the terminal strips. These are the terminal blocks that my "supervisor(?)" instructed me to use, but they don't seem to be capable of really distributing power, so I don't understand where they come into play if I am using the power distribution block.
Also, is there some way to make a normal terminal strip into a power distribution block? I don't fully understand the purpose of having a large terminal strip if each input only goes directly to a single output. The terminology on the internet about the differences between power distribution blocks, terminal blocks, terminal strips, barrier strips, barrier blocks, etc is entirely confusing.
I am also unsure how to choose a cabinet. I tried finding resources online, but there isn't a lot of information about how to figure it out. I initially tried planning it out in the Solidworks Electrical Cabinet view layout, but that was cumbersome and irritating. I've been trying to figure out the dimensions of things needed on paper, but I get lost in the process.

So, TLDR:
Does the power distribution block I choose really matter, as long as it meets the basic specifications?
What's the best/standard/common way to mount switches for a control panel?
What are the things to consider when looking at electrical cabinets?
Are there any important general rules when arranging things on DIN rails in cabinets that someone who has never had any real life experience would probably not know?

Sorry if these questions seem a bit elaborate or silly for a simple design, I'm a junior undergrad working on a very important piece of physics lab equipment at my university. The components I'm turning off/on are several thousand dollars each, as well, so I'm extraordinarily cautious.


texts: Op-Amp output not stabilizing in precision current sink

texts:
I am creating a precision 3A current sink which functions when connected to 12+ volts. I am using the following circuit:

The voltage reference is created by a 0.4V precision reference chip (LT6650CS5) and divided down to 0.3V.

For some reason the output of my Op-Amp is oscillating instead of settling which is causing the output of the FET to oscillate.

Op-Amp output (vout1)

Any ideas?


texts:
Here I have a design ( Vcc = 12V ) where relay gets activated whenever reed switch gets closed. I want to activate the relay after a delay of about 2 to 3 seconds from the instant reed switch gets closed.

To do that I have added a RC element R3 and C1 in the circuit to generate a delay of about 3 seconds. In theory I believe the circuit should work and relay should get activated after 3 seconds from the instant reed switch gets closed. But when comes to implementing it in as real life circuit will it work? or is there any modification that needs to be done in this circuit to obtain my desired results?

Any help is highly appreciated, thanks :)


texts: Digital control of electromechanical gauges

texts:
I have the exact same scenario as a previous question Digital Control of Analog Gauge but am still having trouble solving.
I have two (fuel and temp) old (circa 1973) electromechanical analog gauges made by VDO that I'd like to control digitally. They are 3 wire (12v, ground, and signal) gauges where the signal was originally connected to a sending unit (fuel float or temperature sender).
I've created a number of circuits and have had some success with the one shown below (using a low pass filter, operational amplifier, and MOSFET) but I haven't got it working well yet.
Digital to Analog Gauge circuit

Because the original gauges use a logarithmic scale of some sort, I've measured and created a map in code that varies the PWM output based on the percentage of full (or hot) that I desire. The range of the pwm used is narrow but it works ok with just one gauge and a consistent voltage from the 12v power supply. However, any slight changes in voltage or resistance in the system, such as varying the input voltage from the 12v power supply, putting power to the instrument lights, or adding the second gauge, changes the calibration and makes the needle move more or less than previously.  I am using a single 12v power supply for testing.  I have a 12v to micro USB buck converter connected to power the Arduino.  I share the ground from the power supply to the ground pin of the Arduino.  I use the same 12v and ground from the P/S for power/gnd to the op amp.
Example videos moving through 5 or 6 distinct (cold, normal, half, 3/4, hot or empty, reserve 1/4, half, 3/4, full) steps: https://youtu.be/VGjDCAPXvEQ https://youtu.be/2KRYqxt8-eU
Any suggestions for how to make this reliable?
Components used: Arduino MKR Zero with 12-bit DAC, LM358 Op amp, 2N7000 MOSFET
I don't think the Arduino code is particularly relevant but I'll include it here for completeness.  Obviously, this will eventually use fuel and temp info from my CANbus to write the appropriate PWM output but for now I'm just trying to calibrate the output with fixed steps.
int tempStep = 0;
int fuelStep = 0;
int tempIncrement = 1;
int fuelIncrement = 1;

int tempGaugeMap[] = {
  2500, // bottom of cold
  2560, // top of cold
  2600, // quarter
  2635, // half
  2655, // three quarters
  2680, // bottom of hot
  2695 // top of hot
};
unsigned int tempSteps = 6;

int fuelGaugeMap[] = {
  2710, // reserve
  2730, // empty
  2760, // 1/4
  2820, // half
  2900, // 3/4
  3500, //full
};
unsigned int fuelSteps = 5;

void setup() {
  // open a serial connection
  Serial.begin(9600);
  // make our DAC pin an output
  pinMode(0, OUTPUT);
  pinMode(1, OUTPUT);
  // 12-bit DAC resolution
  analogWriteResolution(12);
}

void loop() {
  int tempVal = tempGaugeMap[tempStep];
  int fuelVal = fuelGaugeMap[fuelStep];

  analogWrite(0, tempVal);
  analogWrite(1, fuelVal);

  if(tempStep >= tempSteps) { tempIncrement = -1; }
  if(tempStep == 0) { tempIncrement = 1; }
  tempStep = tempStep + tempIncrement;

  if(fuelStep >= fuelSteps) { fuelIncrement = -1; }
  if(fuelStep == 0) { fuelIncrement = 1; }
  fuelStep = fuelStep + fuelIncrement;

  delay(1000);
}

I've made some measurements of the gauges themselves as follows:


texts: AC to DC conversion: is this an appropriate implementation?

texts:
I understand that a 20v AC converter supplies 20V RMS AC. I wish to convert this to 20v DC and so have drawn up a schematic for this which includes: the AC to DC conversion, regulation, smoothing, and noise reduction.

I am looking for constructive feedback please.

If a part of it won't work can you please identify which part and why; extra points for how to improve it.

Schematic:

I am reletively new to electronics and come from a computer science background so please excuse my ignorance where appropriate.


texts: 74F86PC XOR does not work in 4 bit adder

texts:
I made a 4 bit adder where one input is from user and the other from a gated master-slave R S Nor.

It seems that the XOR gates (note,  not just one) always give a floating output. I have pulled all inputs to ground through 1k ohm resistances, added bypass capacitors,  and ensured proper connections. What's wrong?

Information

Voltage -  6V

Uses ~11m wire

Base -  the soldering type breadboard with holes and solder already on the holes.

I'll give any other needed info ASAP. Thanks.

PS I'm not posting pictures as it's a jungle of wires and pretty much nothing can be understood from it.

EDIT

I connected an XOR gate on a solderless breadboard to see if my XOR gate was broken. But the moment I powered the circuit board in question, the XOR output went low. Seems this is true for all the 74F gates I use (74F02N NOR and the 74F86PC XOR), but not for the others (74HC08 AND and 74HCS32 OR and 74AC04PC NOT)

Pictures -

Extra questions - where do I get to know what the letters in the names mean? I now know (from asking others) that HC shows CMOS components and from you that F is Fast, for example.

Thanks.


texts:
I know this topic has been discussed a lot, but there seems to be varying opinions about the solutions..

The problem is we are trying to make a current source with an op-amp driving a FET as the load. Our goal is to have a fairly high bandwidth for the regulating loop(couple of 100kHz?), but the output of the op-amp is oscillating.

Using a ADA4807 and a ST P36nE06 mosfet.
The values for the series(R2) and parallel(R3) resistors were chosen from the op-amps datasheet about driving capacitive load.

There is a 100nF bypass cap very close to the supply pins, and a 2uF cap also.

We have tried a few things which includes:

Upping the series resistor to 50ohm or 100ohm. Did not fix it.
Adding 1nF cap from output to -vin of the op-amp, together with a 10k or 100k resistor (miller integrator). Did not help.
Changing the 10mOhm resistor to 100mOhm. Did not help either.

The prototype is done on verroboard. I don't know if that could be an issue?

I would think this op-amp would be able to drive any capacitive load, but it doesn't seem to work for us. What are we doing wrong?


texts: What does each of the basic crowbar circuit's components do?

texts:
I have a general question about the key components of basic crowbar circuit below

I want to use a crowbar circuit for several DC to DC LM78xx linear regulators (various outputs, 7805 7809, etc.) to protect my devices against high voltage. At this point, I am more concerned about the general circuit behavior but I would highly appreciate if you could tell me what I need to pay attention when choosing components for my circuit.

Ok, Forget about components at the left side of the 7805. I know it is for AC to DC.

Please tell me what these components do during normal operation and during overvoltage condition? I want to know what happens during the normal operation while the zener is leaking current.

1. Fuse F1:

I have seen this fuse in various locations in various crowbar protection circuits. Is it important where to put it? I have seen it in this exact position, also after the output capacitor of LM7805 or even before the input capacitor of LM7805. Which place is more optimal?

What type of fuse is the best for these applications? I think Slow Blow fuses (like T1A) are better because I can choose them very close to my actual current consumption and it allows some transient without blowing.

2. Zener Diode D2:

I know how Zener Diodes work. I want to know how I should choose them to be optimal. Do you suggest TVS
?
Can Zener in this circuit cause the output voltage of LM78xx raise or drop (I have seen this reported around the web)?
Is it possible to use the Zener only configuration + Fuse for the crowbar circuit? Why not?

What are the most important points in selecting this zener diode?

What does the leakage current of the Zener do during the normal operation?

3. Resistors R1 & R2:

What do these resistors do exactly?
Why would someone want to put R2 there? I have seen most of the circuits without R2.
Is R1 by any chance for protection against gate floatation?
If it is why some designs don't have this R2?
What are the optimal values of these resistors? Should R1 > R2? or R1/R2 > some value?

4. Capacitor C4:

What does this C4 capacitor do?
Should it be polarized? or is it better to be ceramic or film capacitors?
How does choosing a high or low value of this C4 can affect the performance?
Is it important for it to be low ESR or not?

5. SCR:

I am not familiar with this device. I only know that it conducts when the current gets to it!
How should I choose one that is optimal?
Can you tell me several models so I can start with?

What are the main benefits of SCR against a thyristor?

6. Limitations, disadvantages, and drawbacks:

What are the limitations, disadvantages, and drawbacks of this circuit?

Relatively unrelated question about C3 > C2?

Is it normal to use C3 > C2? Is there any reason for this? Haven't seen this!!

Thank you very much.


texts: XOR light switch with two switches and a relay

texts:
I have just created a circuit which uses an SPDT relay to switch a light on or off whenever i double clap. It works fine with my desk lamp, so i thought it would be nice to add it to my wall mounted lamp, which has two switches in XOR configuration. My goal is to be able to toggle the light with the relay as well.

My only idea is so far to replace one of the switches with the relay, but i wouldn't like to go that way.
Has anyone got an idea how could i wire the switches and the SPDT relay together the way I would like it to work?


texts: Why would one drive LEDs with a common emitter?

texts:
I've seen tutorials aimed at beginners suggest the way to drive an LED from something without enough current drive is this:

(option A)

but why not this:

(option B)

Option B seems to have some advantages over option A:

fewer components
the transistor does not saturate, leading to a faster turn-off
the base current is put to good use in the LED, instead of making the base resistor warm

and the advantages of option A seem to be few:

brings the load closer to the supply rail

but when Vcc is significantly greater than the forward voltage of the LED, this hardly matters. So, given these advantages, why would option A be preferred? Something I'm overlooking?


texts: RFID reader antenna with 2 series capacitors - what do they stand for?

texts:
I have found a RFID antenna "ready to use with enclosure". However, it has a coil in series with 2 3.3nf 50V capacitors.

It doesn't work with my cheap RFID reader circuit (HZ-1050); it only works if I remove the capacitors.

simulate this circuit – Schematic created using CircuitLab

I have three questions:

What is the purpose of these capacitors?
Why doesn't this antenna work with my reader?
Can I make it work? How?


texts:
In reading about op-amp compensation I came across two variants of compensation. Sometimes the compensation is done with a simple capacitor. And sometimes a rc as shown in the figure below (r1 and C1).

So, the capacitor is used to roll off the frequency response for stability reasons.
What effect could the resistor in series have?
To me the resistor seems rather useless.


texts: Need a voltage follower buffer for a tube, how do I calculate and select a mosfet?

texts:
I'm finishing up a design here: https://123d.circuits.io/circuits/852190-jan-6418-vaccum-tube-valve-preamp which is a preamp for an instrument.

First, let me know if anything stupid pops out at you with this circuit, I'm not an EE :(

Second, the original design I'm modifying heavily is here:http://s13.postimg.org/patw5krxj/k270.png

Here is my current progress:

The original design calls for T1 to be a BSN254A, which is no longer available, so I need to concoct a replacement circuit. I think a mosfet was selected originally because it's voltage, not current, driven and doesn't put a load on V2.

I don't have the faintest clue how to select a proper replacement mosfet and how to calculate the values surrounding it. Where do I start?

EDIT

Since this is a guitar stompbox project, supply voltage is 9v which is fed at v1 in the top right. My bad, I'll mark that on the schematic. Hoping to make this a PCB people will actually use to give themselves a nice warm tone with their guitars and mikes someday :)


texts: Effect of lower voltage supply in flash circuits

texts:
Let's consider

this circuit which represents the internal structure of a flash for a generic camera.

enter link description here

Here my reference guide.

Usually in an external flash there are 4 aa batteries with 1.5V, so a total voltage source of 6V. Now let's suppose to use 4 aa rechargeable batteries, which are of 1.2V. The flash works also in this situation (with 4.8V of total voltage source), but which may be the effect of this variation?

Does it mean less maximum light emitted by the flash?

I'd say that lower voltage mean lower maximum light emitted by the flash, but same recycle time (since the time constant depends only on the capacitance and the resistance).


texts:
I'm looking to purchase a webcam (or several) for live streaming since I'm stuck in my house for the indefinite future because of the coronavirus. However anything halfway decent is completely sold out right now because hoarders are buying all the stock and reselling it at 2-3x the price.

I've been trying to figure out if it's feasible to buy one of those MIPI cameras that people use with Raspberry Pi's and turn it into a USB webcam that can use standard UVC webcam drivers. https://www.raspberrypi.org/products/camera-module-v2/  I imagine that I would need some sort of board that acts as a bridge between MIPI and USB.  I would prefer to buy something off the shelf, like an eval board or some sort of breakout that someone has designed, rather than build my own.

Cypress has a line of chips that act as a bridge between MIPI and USB 3.0, but the eval board is $250, so that makes it more expensive than just buying an over priced webcam, so it's not really worth it.
https://www.cypress.com/products/ez-usb-cx3-programmable-mipi-csi-2-usb-30-camera-controller
https://www.e-consystems.com/CX3-Reference-Design-Kit.asp

I found a company called Arducam that sells MIPI cameras and associated products, and they have several boards that convert MIPI data to USB data, but it doesn't look like they are UVC compliant, so I'm not sure if that would work with the video software I plan on using.
https://www.arducam.com/product-category/usb-camera/

Does anyone have any other suggestions?


texts: If I set a multimeter on 'ohms' and put it across a battery, does it short the battery?

texts: As the title says. I am not very good at electronics (I might have, uh, actually done this, for no good reason...). I am wondering now if I should be worried about the battery being damaged.


texts: LCD brightness and contrast control with PWM

texts:
Is it reasonable to control LCD brightness and contrast directly with the PWM pins of an Arduino, or would it be advisable to use a capacitor/filter to get a constant analog voltage?

I assume human eyes can't respond at PWM frequencies, but is there any issues with the LCD electronics?


texts: Detect self power off (and delay power off)

texts:
I'm new! And quite a newby. :\

I build a project with an Arduino and some neopixels. The problem is, that the neopixels stores its last state, and when I switch on the power supply (for both), they tend to blink on start before the Arduino has the chance to toggle them off.

It is one switch that toggles on and off. So I thought, may be I can measure the power supply and detect when it is switched off, but keep it on with a capacitor (seperated by a diode, so the measurement is not falsified by the capacitor). If a LOW is detected, I could send a turn-off signal to the LEDs and voila, problem solved.

(I didn't used the right resistor-values for the voltage drop to 5V. sorry)

My first question: Is that possible at all? Or is the draw of the arduino to high for a capacitor to keep it up long enough?
How big should the capacitor be?
Or do you guys have a better way to solve this?

My other much more simple idea would be a relay, which would bypass the switch and would be powered on by the arduino at it's power up. So I can detect the power off state and do my things and then switch myself off with the relais. But my goal would be to get it done without that giant ugly and loudly clicking relay.


texts: Wiring up 110/220VAC to 6V center tap transformer

texts:
I have a center tap transformer that does 110 or 220VAC stepdown to two 6V rails (with opposing phases). On the 110/220 side there are what appear to be two separate rails, and the wiring diagram is a bit confusing to me:

In order to use this on a 110VAC source and get the proper 6VAC output, how do I wire up the mains side? Per the diagram it seems like I would wire the mains to a single black/red set (with the other set tied off and insulated), or possibly tie them in parallel (black to black, red to red). Is the idea that for 220VAC input I'd tie the center black and red together and wire the 220 mains to the outer pair of wires?


texts:
consider this rule: In SR latches using NOR gates the S should be connected to Q and the R should be connected to Q' and for the SR latches using NAND gates vice versa.

is this a convention ? or a rule?

and another question I have about conventions is that why in SR latches with NAND gate when s = 1 the output is Q=0 ( S is the set input so when it is 1 the output should be Q=1)


texts: Replacing normal fuse with self resetting fuse

texts: I have a multimeter with a normal fuse that I have recently broken and I would like to replace it using a self resetting fuse with the same specifications (250mA / 250V) by soldering it in place. Would there be any draw backs?


texts: Term for a chip that is used in a camera to detect light

texts:
In terms of an integrated circuit, what is the term for a chip that is used in a camera to detect light?

I hope this photo helps. What is the technichal term for the light sensitive IC in a camera?


texts:
An open appeal for a simple way to control 2-colour, 2-lead LEDs. I am using these LEDs as the 'mimic' lights for my model train layout point control. Working on 12v DC, the point motor is wired to provide a +12v feed to either of 2 connections when the motor switches from one position to the other. I usually use two separate LEDs (1 red and 1 green) wired to a common -12v DC and, I have no problems with the basic circuitry required. However, for these 2-lead LEDs to work, I have to reverse the polarity in order to change the colour output.

I am sure someone out there has a simple solution to this and, I would be glad of any assistance. I can supply any further information you may need.


texts: Microcontrollers interrupts what is "pending"?

texts:
I just started learning timers with my lpc 1347 board. Here is simple code from lpcopen

    uint32_t timerFreq;

/* Generic Initialization */
SystemCoreClockUpdate();
Board_Init();

/* Enable timer 1 clock */
Chip_TIMER_Init(LPC_TIMER32_0);

/* Timer rate is system clock rate */
timerFreq = Chip_Clock_GetSystemClockRate();

/* Timer setup for match and interrupt at TICKRATE_HZ */
Chip_TIMER_Reset(LPC_TIMER32_0);
Chip_TIMER_MatchEnableInt(LPC_TIMER32_0, 1);
Chip_TIMER_SetMatch(LPC_TIMER32_0, 1, (timerFreq / TICKRATE_HZ1));
Chip_TIMER_ResetOnMatchEnable(LPC_TIMER32_0, 1);
Chip_TIMER_Enable(LPC_TIMER32_0);

/* Enable timer interrupt */
NVIC_ClearPendingIRQ(TIMER_32_0_IRQn);
NVIC_EnableIRQ(TIMER_32_0_IRQn);

and interrupt handler

void TIMER32_0_IRQHandler(void)
{
  if (Chip_TIMER_MatchPending(LPC_TIMER32_0, 1)) {
    Chip_TIMER_ClearMatch(LPC_TIMER32_0, 1);
    Board_LED_Toggle(0);
  }
}

My question is what is "pending" and why I must check it in IRQHandler? Thanks!


texts: boost converter circuit behaving strangely

texts:
I built the following circuit:

The boost onverter works fine when applying 0.5 time ON PWM signal (Vout = 2.5V) but when I  try to increase the voltage using 0.8* time PWM signal the Vout** stays about the same.

*Vout = 1/(1-tON)
**Vout relative to ground

Why does that happen and how to fix it?

TECHNICAL DATA:
Inductor current = 30mA.
DCR = 16 ohm.


texts:
I did a lot of research for being able to control my Mitsubishi FX-5U PLC.
I want to control it over network using SLMP with 3E frame messaging, but I am unable to understand the message frame.
I am referring this manual. But despite spending days I havent been able to understand how to control the PLC using SLMP.
I understand that if I use this message frame, I will be able to read data on D200 register, and it does work successfully.
50 00 00 FF FF 03 00 0C 00 10 00 01 04 00 00 C8 00 00 A8 01 00

But, I just don't understand, how to access and control the devices on X and Y. Lets say I have to read data from all inputs (X) or write data to all/few output (Y) at once.
I tried resolving this issue by trying to write to outputs, Y1 and Y2, and set them to high, but it doesn't work (Below frame is in ASCII format)
50 00 00 FF FF 03 00 0D 00 00 10 14 01 00 01 Y* 00 00 01 00 02 11

I know I am doing it wrong, so want to know really what am I doing wrong


texts: Method and probes for measuring resistance of conductive braiding?

texts:
Looking for advice on a method to measure the resistance of a piece of conductive braiding. The braiding is a metal plated material; it's flat when pulled taut and expands into a cylinder when bunched together. Preferably, I want to measure the resistance while it is expanded, which would mean putting it on a (non-conductive) mandrel or rod. The problem with this is that the probe clips aren't big enough to get around the larger sizes of braid and make good contact.

Are there some sort of wraparound probe leads that exist which could be strapped around the mandrel? Would it be better to make a test fixture that will strap flat pieces of copper around the cylinder and then use typical pin-type probes and account for the added resistance from the copper straps? Does it even matter to measure the braid while expanded?

I've been digging around online but can't find anything on a "standard" method for measuring resistance of conductive braids.


texts:
i have breadboarded a TDA2050 amplifier, using this schematic

i get good sound intensity with a half acceptable quality. the down side is the constant noise and humming. i have found a possible solution for the problem to be the input, as when i connect the GND to input the noise is fully removed. the situation improved a little when i added a 10k parallel resitor in the input, but i was wondering if it was possible to use another circuit in the input stage that outputs exact GND or 0v DC when there is no signal and the signal itself when i have a signal. i have tried a ua741 differential amplifier, voltage follower circuit, and a mosfet based buffer . they all enhance the quality but the hum is still non-negligible,

thanks in advance


texts: Where does tesla radiant energy come from?

texts: Few days ago, I had read an article about tesla radiant energy.I want to know whether this energy comes from the air or the wasted energy in radio stations?


texts: Which is the loudest in terms of sound intensity - Sine, Square or Sawtooth waveform?

texts:
From this, (Square wave / Sine wave is more audible) I now understand that a Square soundwave will be louder than that of a Sine sound wave when played at the same frequency (for example 500 Hz). However, how about a sawtooth sound wave; which order from loudest to quietest is it placed?

I know that the Sine wave is only composed of the fundamental frequency and hence produces the lowest pitch - which is less sensitive to human ears. Square sound waves are composed of infinite odd harmonics, and sawtooth waves are composed of both odd and even harmonics. From experimenting, I have found that square sound waves are louder than sawtooth, which is louder than sine waves. What is the explanation behind this system of order?

Thankyou very much.


texts: Generate an n bit random number in Verilog

texts:
I can easily generate a random number of width 32 bits in Verilog using $random. Is there a way to generate a random number of exactly n bits (say n = 70)?

I guess I could concatenate many 32-bits random numbers, and then restrict down to the required number of bits, but that seems like a hack.


texts: How do TVSS and Circuit Breakers (thermal-magnetic) interact with each-other?

texts:
In EU you can find thermal-magnetic circuit breakers all other the places in buildings and it's not uncommon to have daisy chains of them (meaning a main panel will have one, which is connected to another secondary panel which has another one, etc).
First of all I am not whether having daisy chaining of breakers increase surge protections (against lightning or shorts)?
Also, say we have a TVSS in the mix now (e.g. one found in a UPS), what is the electrical relationship between that and the breakers? Do the breakers add protection or do they subtract it to the efficiency of the TVSS? Or does it not matter at all?
Thanks a lot!


texts:
Is there any alternate way to design Astable Multi Vibrator with use of only Resistor & capacitor ? ( avoid 555 Timer ) , avoid BJT if possible.

my aim to make most compact Astable MV.


texts: How to chose the right voltage and coil(s) for coilgun?

texts:
Coilgun is a simple canon which attracts piece of metal into the core of the coil and then, when the piece of metal reaches midpoint of the coil, removes the power and leaves metal at it's accelerated speed.

I've seen people making these and it seems to me as a safer alternative of railgun, though still very dangerous.

I'd like to ask how to reach good balance between different aspects of the design. There are three things that are kinda in conflict and all have positive and negative effect:

Voltage - Higher voltage means higher current through the coil and much more energy delivered. But it also increases risk of fatal injury and requires thicker wire insulation.
Wire thickness - Thicker wire heats less and has lower resistance, but limits feastible amount of turns the coil has. Also up from certain thickness, manufacturing of the coil is not very easy process.
Number of turns - AFAIK, number of turns boosts magnetic field strength quite well. However, the more turns the higher resistance AND inductance. And the coil must charge fast, so inductance is a Bad Thing.

Is there a simple way to calculate or guess optimal parameters? I intend to make a gun that is safe enough to make at home with precautions but also powerful enough to shoot objects off a table.


texts: How much accuracy can I get with RF / acoustic triangulation?

texts:
Lets say I wanted to track an object locally in 3D space. This object could be transmitting at low power. I could have 3 or more receivers in the same room as an object. How much accuracy could I expect to get in practice?

Would my calculation be based just on received strength or would it make sense to do something such as send coded pulses in order to synchronize them. ie by determining the phase difference of the pulses relative to each receiver to improve accuracy. I guess this accuracy would be dependant on frequency?


texts: I'm trying to identify the IC chip below, which I believe to be an RF Switch. Any help anyone can offer regarding who the manufacturer might be and/or what the part number might be would be greatly appreciated.


texts: Ground coupling a high voltage source with the A_GND and D_GND

texts:
I have a device that measures the current in the mains through a 0.01 Ohm 20W shunt resistor. The voltage across the shunt is amplified by a op amp and feed into a uC's ADC for farther calculations.

But to measure the voltage drop across the shunt the the mains needs to be ground coupled with the op amp and the rest of the components, which means that the D_GND and the A_GND will be 220 V above earth, and I feel very uncomfortable about that,

So what can be that to avoid raising the GND to such a high voltage?
I know one solution would be opto-coupling the signal, but it doesn't really fit in my project. Also a capacitor between the GND and the mains might work. Any thoughts?

Here is the schematics:


texts:
for my home automation project i'm using 10 Sensirion SHT21 Temperature and Humidity devices, those devices are distant 30/50 meters away from my ESP32.

Those devices are driven using 5V and at both ends there is a PCA9306 level translator with EN pin wired to the respective GPIO (LINK HERE), so this solution gives to me the ability to use 5V over 3.3V on I2C side and go more meters away from my ESP32 using a simple cat.5E or 6 UTP cable.

So, on all 10 cables directed to the sensors there are: SCL-SDA-5V-GND.

Now, basically i want to "shut down" the sensor channels and avoid to leave 5V on all sensors (and wires) while they are not reading (the ESP32 polls them sequentially)...optimizing the power consuption that it's present on the wires.

I was thinking to use a PMBF170 mosfet (because i have a lot of them and the required current of the sensors and cables can be ok and far from the maximum 300mA drain current) in parallel of each GPIO (that send the EN signal to the respective PCA9306) and wire between VCC and DRAIN the VCC and GND cables directed to the sensors similar to the below image:

Is that a good idea? it can be feasible or it's completely useless?


texts: Controlling 13 outputs with a mcp23017 or 74hc595 and two uln2003?

texts:
I need to drive 13 20ma (constant) loads with a single microcontroller with only 5 available pins. My first thought was to just use a mcp23017 or some 74hc595's but after reading the datasheets it appears they both have low max current into vcc (125/70 respectively) so that won't work directly. I have a bunch of uln2003 chips so I was thinking of using those with the port a expander to drive the loads but it feels heavy for what I'm doing. Am I missing something simple here?

The mcp23017 says it has max 150ma into vcc and 125 out vdd, could I do something clever like source  7 of the loads and sink 6 of them through one mcp23017?


texts:
What does it mean for a circuit to provide an output power of say 1000W? Is "circuit providing power" referring to the battery supplying energy to the external circuit, or is it referring to the power of the components? In general I'm just finding the terminology used in electricity a bit confusing.

EDIT:

What does "circuit provide an output power" mean?


texts: Can I drive an optocoupler input with just 0.5mA (500 microA)?

texts:
Im trying to interface a keypad button in a device with a MCU, and they need to be in different circuits, with no shared GND.

This keypad button has 5V DC when not pressed, and 0V when pressed. I want to use an optocoupler to "sense" when the button is being pressed (or released) so I can send a signal to an MCU.

But when pressing the button, the amount of current that flows is only 0.5mA. Is this current enough to "turn on" the internal led of an optocoupler, and then it switches the internal transistor?

I tried an ordinary led in series with the keypad button wiring, and although it allows current to pass and the button works, it never lights. The current in the led is even less, it's 0.32mA.

So, if an ordinary led doesn't light, would the optocoupler work?

The optocoupler I have is the 4N25.  I can't find if there's a min input current in its datasheet.

If not, is there another way for me to do it?

I added a diagram of "what I wanted to happen" and "what I did for testing", to be more clear.

Thanks!


texts: How to design a snap/breakable PCB module?

texts:
I am designing a board which can be snapped (a part of the PCB could be broken off if not required):

Are there some design guidelines I should follow? What are the common rules (holes sizes and spacing) so the board can be snapped without too much strength but also not too easily?

Also, I saw some examples that uses two lines of stamp holes (e.g. the board below). Are there some advantages of doing that (e.g. reduced mechanical stress) other than having custom spacing between the boards?


texts: Is my wire rated at a high enough current?

texts:
I am in the process of planning a speaker build. I am making sure my current wiring is up to the demands of a new system. The amplifier is a CV 1800, which can put out 9.5 amps at 4 ohms in stereo (600 watts) or 19.5 amps at 4 ohms in a bridged mono setting (1800 watts). I am wondering what it would put out at 3 ohms. I am lost as how to calculate this, as I don't think it follows any basic V=IR, P=VA equations that I could use in an ideal situation.
The wire I'm using is rated at 300 volts and 12 amps. Would this be adequate for use at 3 ohms? (I'd also guess the wire is about 50 ft)

The wire: http://www.farnell.com/datasheets/2335141.pdf

The amplifier data sheet (The Cerwin Vega website isn't responding to me):
https://mans.io/item/cerwin-vega/cv-1800
or, just search cv 1800 data sheet


texts: Does this speed controller alter resistance or capacitance?

texts:
The attached image is of a ceiling fan speed controller module I brought online. It seems the attached circuit mainly consists of some capacitors. This  makes me believe that the 4 different settings on the switch alters capacitance, rather than giving out a different voltage?

Has anyone worked with a ceiling speed control switch like in the attached images before, that can shed some light on it's operation? I need to figure out how to connect this to a ceiling fan motor I'm fixing.

I don't have the required multimeter to measure capacitance, and taking resistance readings on the 4 different settings only delivers a reading on setting 4, and nothing on 1-3, not even continuity.

I'm not brave enough to connect this switch to 220V (with load of course to prevent a short) and measure it with my multimeter.

I guess I won't get a resistance/continuity reading on a cap since it's not charged and not letting current through, right?


texts: How can I wirelessly deliver ~30B of data to ~10 peripherals roughly every 50ms?

texts:
I am thinking of a system where 10 or so peripherals need to receive 30-50B of data every 50-ish milliseconds (each peripheral gets unique data). The total throughput required might not be huge (6-10kB/s) but the problem lays in the number of devices which need to receive the data.

I've looked into using BLE but even though the total throughput lies well within the maximum possible ~35kB/s, what I want is not possible due to the hard limit of 20ms Connection Intervals. Another solution I considered is using a simple RF transmitter and RF receivers which all listen to it simultaneously. I'd have to manually take care of error correction etc but I would not have to worry about switching between the receivers which takes precious time. A problem with that would also include the inability to have two of such systems deployed near one another without the risk of the transmitters talking over one another.

So what other solutions are available to me?


texts: Could I get a second pair of eyes to check if this BMS can be used for charging?

texts: I'm new to electric engineering and electronics in general, so as a first project I'm building a battery using 18650 cells (4S4P). I am aware of the risks when buying from Chinese suppliers on aliexpress, however I'm curious if this BMS supports balanced charging protection. After some research, I believe it does, seeing as there are electrical contacts for each cell, much like a balance cable. I would be extremely grateful for someone else to double check for me. Thanks!


texts: Methods to ruggedise a USB3.0 type A port

texts:
I am developing a carrier board for a autonomous navigation robot. I need to change the USB 3.0 type A ports to ensure a reliable connection in a rough terrain.
I am familiar with some methods as:

USB Screw-locks plug and receptacle

Hercules Connectors

Lockable USB receptacle

Bulgin Buccaneer Sealed USB Data Connectors

What other options do I have ?
Source 1


texts: Package outline dimensions - meaning of theta and package identification

texts:
When reading data sheet dimensions to create Eagle devices, I've come across a theta (θ) dimension, which seems to indicate the seating angle of a device pin in relation to the pad.

Typically, 0º and 7º θ values are given, and other dimensions can vary significantly for different θ values!

I can't find anything else in the datasheets that would help differentiate these packages - they seem to have the same marking codes.

For instance, the NX3V1G384


texts: What material are plug pins made out of?

texts:
I've noticed that some Mains 120/240V Voltage plugs are a gold color and some are a silver cover. I'm talking about the kind of plug pins on something that plugs into a standard 15A/20A receptacle.  Are plug pins made of brass or is it something else?  If it is brass, can any brass work or are there certain properties to the material that make it electrical grade?

I don't want an entire plug, just the pins. I'm hoping for plug pins that could work for a variety of devices (computer charger, cell phone charger, night light, toaster, microwave, etc...).  I want something standard, obviously electrical grade, that can handle that kind of pull.  How do I know what material my plug pins need to be made of?

As I have tried to search, the only companies that show up are based in India and there seems to be no way to just order some plug pins without doing a huge bulk order. Where can they be purchased?


texts: Should same sized peltier elements be cascaded?

texts:
I learned that peltier elements give better cooling on cascading but need to be growing in size towards the hot side.

I have 4 peltier elements of 40×40×35mm and I am planning to make a portable fridge.

Now the question is should I line them along one side parallel to each other or should I stack them up (2 sets of twos)?

If I should stack them up, should I just place them one over another,  or connect them via heatsinks/metal sheets?

If I should place them parallely (on single wall) what should be the minimum distance between them?


texts: Component on Crypton gas analyser circuit board

texts:
This is my first visit to this site. I am no more than an enthusiast in these matters.

My Crypton 307 CO/HC emission module expired in a puff of smoke. The offending part is marked KB LO 2 and + AC -. It is the size of half a thumbnail and has four pins in line on its underside.

I should be grateful for any information as to what it is and where I might obtain a replacement.


texts: why my LEDs burned with the right driver?

texts:
I am trying to connect, in parallel, 18 LEDs that have these specs:

LED

size: 10mm;
Voltage: 3.2V - 3.4V;
Current: 20mA.

Driver

Type/Model: MeanWell LPC-20-350 (datasheet: http://www.meanwell.com/search/lpc-20/LPC-20-spec.pdf)

From my calculation, by putting 18 LEDs in parallel I need a total current of 360mA, so by driving a (max) current of 350mA i do not need a resistor (to limit the current) and it should not burn the LEDs, however after a blink they all burned.

What am i missing?


texts: ATtiny measuring voltage for battery charger

texts: Would it be possible to use adc with the reference voltage at ground, to determine the voltage of say a battery? I was thinking of creating a battery charger with the attiny for automatic cutoff and such. Or would there be an easier way of achieving this? I would assume some analog circuits would work, but I'm not sure which route is best. Thanks in advance.


texts: Simplest device for mini operating system

texts:
I have been developing an operating system off of this video and I want to begin building a device to support this os. All it really does is print to the screen. I want to build a small device with an lcd color screen that can boot this os (from something like an sd card) and is as simple as possible.

What parts would I need to build a small and portable device that can print the output onto a small lcd screen?


texts: Building a digitally controlled bench power supply using an AVR

texts:
This article describes a rather nice solution for building a current- and voltage- controlled benchtop power supply using a DC supply in the range of 20-30 volts and some additional down-regulation circuitry, with current and voltage control provided by an AVR microcontroller in a feedback loop.

I like the idea, and I'd like to build my own, but I think the interface is a bit kludgy, so I'd like to improve on it. Unfortunately, although they sell a kit, they don't provide schematics. I understand about half to two thirds of the concepts they describe when it comes to power regulation - certainly not enough to build one myself - and the circuit diagrams they publish aren't complete.

Can anyone point me to some resources to get me started on building this myself? Ideally, I'd like schematics that incorporate most of the analog side so I can modify them in a fairly straightforward fashion to incorporate the microcontroller, since my knowledge of analog circuitry and power regulation isn't great.

Also, the linked project shuns existing regulators in favor of a lot of discrete components. Are there more integrated solutions that would simplify the design, without sacrificing features?


texts: Using a 4-pin computer fan controller without the load

texts:
Is it OK if I use the controller from a CPU fan without connecting the motor's coils?

All I want is to use the Hall effect sensor.

The datasheet is posted here, the driving output circuit uses a darlington pair.


texts: How to control transistor with lower base voltage than supply voltage

texts:
Here is the link to simulation of h bridge that I built Simulation link in this I was somehow able to control transistors with 5 volts when supply was 9 volts

but I still didn't completely understand it as for current to flow base voltage has to be .7v higher than emitter voltage, so I simulated only one transistor of circuit and it didn't work which means the 5 volt at base of transistor wasn't able to activate transistor Simulation of only one transistor

So can someone please explain me how the first circuit works but second doesn't and is there a way to control transistor with lower base voltage without overcomplicating circuit with something like bootstrapping circuit


texts: Force per velocity per time squared signifies what?

texts:
Anyone know what force per velocity per time squared signifies? It has something to do with magnetic fields.
I was doing dimensional analysis and it popped up. (Charge is given units of force and the rest just follows)
\$ E \quad = \quad \frac{q_1}{d^2}  = \quad \frac{F}{d^2} \$
\$\frac{1}{\epsilon_0} \quad = \quad \frac{d^2}{F}\$
\$F \quad = \quad \frac{1}{\epsilon_0} q_2 E \quad = \quad \frac{d^2}{F} \frac{q_2 q_1}{d^2} \quad = \quad \frac{d^2}{F} \frac{F F}{d^2}\$
\$B \quad = \quad \frac{I_1}{d} \quad = \quad \frac{q_1}{t d} \quad = \quad \frac{F}{t d} \quad = \quad \frac{F / v}{t^2}\$
\$\mu \quad = \quad \frac{t^2}{F}\$
\$F \quad = \quad \mu I_2 B d \quad = \quad \frac{t^2}{F} \frac{q_2}{t} \frac{q_1}{t d} d \quad = \quad \frac{t^2}{F} \frac{F}{t} \frac{F}{t d} d\$
\$c \quad = \quad \sqrt{\frac{1}{\epsilon_0 \mu_0}} \quad = \quad \sqrt{\frac{d^2}{F} \frac{F}{t^2}} \quad = \quad \sqrt{\frac{d^2}{t^2}} = \frac{d}{t}\$
https://tok.fandom.com/wiki/Template:Electromagnetism_header


texts:
Inspired by this SE question, I was wondering how good CircuitLab would be a solving this type of problem.

Why do we not include the current source when finding the Thévenin equivalent impedance?

simulate this circuit – Schematic created using CircuitLab

The question asks: what should be the value of an impedance attached to the right side such that the power is maximized. One method to solve is to find the open circuit voltage and divide by the short circuit current.

I got the correct answer eventually, but the process was a bit clunky. Any tips on a better process? I am still learning CircuitLab.

I used a frequency of 1 rad/sec (1/2pi Hz) so the impedance for the inductors would match the inductance.

I really only want to run at one frequency, not a range. I used a very narrow range instead. A lot of points per decade are necessary to be sure that a point is within the range (otherwise you get nothing).

At first I was using degrees for Voc and Isc. But the default has limited significant figures and I don't know how to change it. I switched to rads.

After I got the Voc and Isc, I used Excel to divide the two. Then, for the final answer, the imaginary part is inverted.

With formulas shown:


texts:
I have this question, where the drain-source current and its bias gate voltage of a MOSFET is known where source is connected to ground.

I find its drain current is less than saturation current by a huge margin, but not zero. So I have concluded it's in linear region. Now I am asked to find the drain voltage (Vds).
Using Id equation in linear region, I found two possible values for Vd. Problem is that both the values are positive and for both Vd<Vg-Vt is satisfied. How do I identify which is the right answer?


texts: How to determine wiring of unknown LED scrolling display board

texts:
My school has a LED scrolling display board from long ago in the main lobby. When I flip the power switch, it turns on and starts displaying zzzzzzzzzzz... There's a connector on the outside (2x10 pins, see picture) that doesn't match up with anything I can find at school or online.

I have done some testing with a multimeter. Labeling the top left pin 1, the top right 2, second to top left 3, second to top right 4, and so on, I have done some testing. Pin 1 is connected to pin 2 with a resistance of about 3.7 ohms, while pin 2 is connected to pins 4, 6, 8, etc. (all the pins on the right side) with almost no resistance. 1-2 have a voltage drop of about 4.7 V when the thing is on, and 1 is positive while 2 is negative. All other pins next to each other (5-6, 7-8, etc.) also have a voltage drop, although it is a little smaller. 3-4 has a voltage drop of 0 in either direction.

This testing leads me to believe that the pins on the left are connected to power while the pins on the right are connected to ground, but I am not sure of this. Even if that was true, where do I go next? How can I go from displaying zs to being able to input a message for display?

For reference, the only company name anywhere on the board is "The High School Source Property of MarketSource Corporation 10 Abeel Road Cranbury, NJ 08512 (800) 877-4401"

The board is a matrix of LEDs about 2 meters long and 6 LEDs wide.

Thank you so much for your help. Let me know if you need any more information.


texts:
I have several shift registers and only one "read" pin.

I would like to know if I can use PNP transistors to switch between the registers ?

So every emitters will be connected to the data output of his associated shift register, every collectors connected to the single input and the base connected to some current source allowing me to switch between the registers.
I'm a bit scared about signal integrity. Does it sound ok for you or a total non sense ?

(Don't take in account the selected parts number, just for the example)

EDIT : A simple remark, clocks and latches are all "synchronized" on the same two pins. So this would allow me to drive virtually as many register as I want with only 3 pins used on the arduino.


texts: H-bridge ic for high voltage and/or current

texts:
I tend to design my circuits around H-bridges, but the problem with making them out of standard mosfets is that I always have to compare the rise times, fall times, threshold voltage, etc of my n-channel transistors and my p-channel transistor. I figured this circuit would be best as an IC, but the h bridges I found all seemed for relatively low current and voltages. I figured if this type of device was mainstream, it might exist under a different name.

Are there any standard ICs that consist of well matched p-type transistors and n-type transistors?

I am looking to switch ~3kW at frequencies on the order of ~1kHz-1Mhz (depending on what is feasible.)
The current and voltages being used will depend on what is feasible. This may require two separate devices depending on what I choose to do.

My high voltage applications would probably not exceed 1kV (to start), and my high current applications would probably not exceed 50Amps (to start.


texts: How can I turn a midi keyboard to a stand-alone piano using Arduino or any other way?

texts:
I have a midi keyboard, but I find it frustrating to start PC, DAW system every time I want to play.
Is there a way to use Arduino to create an on the go stand alone piano. (It should work like a digital piano). Just switch on and play.


texts: DC Current Measurement (resolution of ~ 1 uA)

texts:
I haven't worked with electronics in a long time, and now have the task of measuring the power consumption of a low-power device I'm writing firmware for...

When the device is drawing very little current, the DC power analyzer shows the current oscillating(?). So, my question is, is the average current of a reading with peaks of 100uA and -100uA, around 0A? or is it something else?

My confusion is because I didn't expect to have negative and positive values in my reading. Any help is much appreciated!

I'm using the Data Logger function of the Keysight N6705C DC power analyzer.

p.s: Attaching the reading from the analyzer. (Avg:8uA, Peaks: -256uA, 887uA). The spikes in the reading are not the issue since they are triggered by periodic tasks in the MCU. My concern is the min, max, average indicated in the reading.


texts: Capacitance to Voltage converter - Water level sensor

texts:
I have to design by myself a capacitive level sensor. To create my "capacitor", I use two copper strips that I take from a copper tape and put it on the tank where I have to take the measurement.

However, the measurement must be a voltage or a current as my PID controller can only "read" this kind of value. Therefore, it means that I need something to change my measured capacitance into a V/I and I do not find an easy way to achieve the conversion.
By easy way, I mean that I am in a city where there are not a lot of electronic devices that are available so easy means "without too many components hard to find".

The specifications of my system are the following ones:

Measured Capacitance : [5pF(low level) --> 35pF(High level)]

This is the full range but I could use a small range inside this one

Input of Controller: 0-10V or 4-20mA

I hope that someone can resolve my problem, or at least give me an idea.
Thank you in advance.

Sincerely.


texts: Conditions for writing primary current = m*secondary current transformer

texts:
In a transformer, under which conditions can we write the following equation :

It suppose that the magnetizing inductance is infinite? So the permeability of the core is infinite and the transformer has no gap (so it cannot be applied to a flyback transformer). In other words, it means that the transformer store no energy which can be coupled to the secondary. So the energy is instantaneously transfered to the secondary?

Thank you very much,


texts:
whenever the sampling theorem was explained to me, a situation of this kind was proposed to me.

If we look at the previous image we will see that the condition to avoid spectral aliasing is that we have

\$f_S \gt 2 f_0\$

But now let's consider this specific situation (which corresponds to a pure sinusoidal signal):

or also a more general situation in which there is a certain bandwitdth on the positive frequency axis. In this case, which is the condition to avoid aliasing?


texts:
I have these ICs

and I want to wire them like the sparkfun 16:1 mux breakout board.
Here is what I have so far. Is this correct?

 However I feel like these are not the same as the actual ICs. Also another quick question, how many of Mux can I daisy chain?
Thanks in advance :D


texts: I'm having a little trouble with an isolation amplifier. I'm using an HCPL-7800 isolation amplifier, in the circuit format provided by the manufacturer as a test circuit, and feeding it low voltage DC (0-200mV input). The gain of the amplifier should be flat at about 8.029 nominal, but at low input voltage (1mV) I'm seeing a gain of 25, and at my max input voltage (180mV) I'm seeing a gain of 7.9 (linear drop). I've almost exhausted every resource on this. I've laid out the board according to the manufacturer's recommendations, used the proper soldering temperatures, input resistance, etc. I've even been in correspondence with Avago, who claims it's properly set up, but they themselves have no idea why it isn't working correctly, and their demo board is a near copy of my  circuit (different resistors, different input range). They have however given up on this issue and stopped responding. Does anyone have any insight as to what would cause this phenomenon? Thanks All]1


texts: Writing and reading from and to SRAM memory

texts:
im just learning SRAM.
I wanted to ask, consider the 4x4 memory cell array below

If i wanted to select a word line or row, would the row decoder be a 4x1 multiplexer where each wordline is connected to a Vdd to enable a read or write operation on the cells?

So maybe 2 bits can select any 4 wordlines.

And for the Column decoder, will it be another 4x1 decoder, where the each bit line will be connected to the multiplexer 4x1 and this multiplexer connected to a line which can be either 1 or 0?

Where does the sensing amplifier come into this and are there any other peripherals?


texts:
I am using a safety PLC from Schneider and it is connected to a safety output relay with model number XPSMCMRO0004. The datasheet mentions that the min and max switching current is 20mA to 6Amp respectively.
I wanted to ask how is switching current different from Load Current. As i understand switching current is just to switch the coil of the relay and it should be different or independent of the load current. Or are they the same in this case? Any help will be appreicated.


texts:
I got some 0.1uF ceramic capacitor in front of my mcu IO pins to smooth the inputs values/spikes

I was wondering if this placement is bad or not because their position is "over" the input so maybe (unexpected?) current will "hit" the pin before being smoothed by capacitors.

Is it something like this worth the layout refactor effort?

Notes:

input pins will detect LOW values
input pins are pulled up by R6,R8,R10 resistors
ground wires are still visible because I didn't ratsnest'ed yet :)

Edit:
this is the schematic for each input


texts:
I don't understand, why the voltage V2 is approximately Vb.
Can't V2 be 0, if Vb is enough high, so that the emmiter-current of Q2 is Ie2?

The assistent only told me, that because both transistors are aproximately the same and because the two resistors R2 are also aproximately the same, therefor the Voltage V2 has to be the same as Vb.
The point, where I get confused is, that the Current through the left R2 resistor is dependet of the Voltage V2. Correct me if I'm wrong.

I hope someone can help me.

Have a nice day:)


texts:
Is a short circuit that occurs for as long as an instance safe?

In the following schematic done from here, I have a silicon controlled rectifier that is used as a latch (the circuit simulation doesn't seem to be really accurate).

  That white link thingy is a closed switch. In the diagram, the SCR is
  turned on and I have just closed the switch connected to ground. At
  this moment, a theoretical huge surge of current is going through the
  anode, out of the gate and through the switch to ground, which
  immediately turns off the SCR, so this stops and thus happens quicker
  than the blink of an eye.

In real life, I connected the gate to positive which turned the LED on and then connected the gate to negative, which turned the LED off with no problem.

However as shown in the previous image, it shows a large amount of current going through the anode of the SCR and out of the gate.

After looking around for a bit, I found an image (and added some edits) which gave me an idea as to where the simulator's result may have come from.

  NOTE1: If gate is pulled to ground, the current would rather go through
  here than through the base of the NPN transistor out of the emitter to the cathode. This means no current is going
  out of the PNP transistor so the PNP transistor turns off and
  everything turns off. But is this safe?

Seems like a normal SCR can behave like a GTO thyristor.

The catch is, for a short moment when the gate is connected to ground before the SCR turns off, there would theoretically be a large surge of current going through the anode and out of the gate for a short period of time. Is this safe (in a way you can pass a safety regulation if selling as a commercial product, excluding the fact that the circuit allows you to enable both switches at the same time)? Can I do this to all thyristors? If not, what do I need to look for to ensure it's safe for certain types of thyristors to have their gates brought to ground?

I'm using a BT169D SCR, which is not labelled as a GTO thyristor but seemingly behaves like one.


texts:
I am planning to build a light from 12 LEDs (CREE XML RGBW).  These are 4 diodes on one star - a red, a blue, a green, and a white - with a total forward voltage of 13.9V at 350mA.  Is there any kind of "slim profile" (i.e. max. 24-30cm long and max. 3 cm high) heat sink that could dissipate 170W?  Also, shouldn't it really be able to dissipate whatever the max. forward Voltage is at 1,000mA (the max current drive these LEDs support), just to be safe?  I have looked everywhere, and I haven't found any.  I am working on using some of the calculators online, but so far I get different results than expected and I am also having some difficulty identifying some of the parameters (e.g. junction-to-case thermal resistance and thermal resistance of the heat sink in question).
For example, using this Celsia calculator, I set Q = 170, Tcase Max = 100 (the default, I don't know where to find this), Max Ambient T = 30 (because the light will be in open case suspended in air in my house), and I play with different values of Volumetric Thermal Resistance across the range in their table, I get heat sink volume estimates between 121 cm^3 (Rv = 50) and 1943 cm^3 (Rv = 800).  A 30cm piece of the MakersLED HeatSink SLIM has a volume of 1801 cm^3.  Based on the calculator, that heat sink should most likely be adequate for all 12 of my LEDs.  However, the manufacturer recommends no more than 33 W per 1 ft (approx. 30cm) of heat sink. 33 W is very different from 170 W.  I'm thoroughly confused.  I'd appreciate some help, even if it's just links to resources that will help me figure this out for myself.  Thanks.


texts:
I'm trying to use 3 TCA9539PWR and a TCA6408A on an I2C bus.

Here's the schematic diagram:

However, when I try to send the TCA9539PWR's addresses , none of them responds (no ACK) and when I try to send the address of TCA6408A (0x40,) the wave shows that it can't pull down the bus fully.

I use 10k pull-up resistors, and I think it's the resistor is strong enough;I can't change the res on the pcb easily, so it's hard for me to test that.

That's a part of the code I use to control the SDA and SCL:

void SDA_OUT(void) //init SDA to send Data
{
   GPIO_InitTypeDef GPIO_InitStruct;
   GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
   GPIO_InitStruct.Pin = I2C_SDA_Pin;
   HAL_GPIO_Init(I2C_PORT, &GPIO_InitStruct );
}

//...

void SDA_IN(void)    //release the SDA wire
{
   GPIO_InitTypeDef GPIO_InitStruct = {0};
   GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
   GPIO_InitStruct.Pin = I2C_SDA_Pin;
   HAL_GPIO_Init(I2C_PORT, &GPIO_InitStruct );
}

//The SCL wire was initialized by STM32CUBEMX;
  GPIO_InitStruct.Pin = I2C_SDA_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);


texts: How to prevent high side PMOS from glitching?

texts:
I want to use a PMOS-Transistor as a high side switch like so:

simulate this circuit – Schematic created using CircuitLab

But when I tested this circuit on a breadboard, there was always a small voltage spike at the output, when the 12V where switched on. Since this will be used as a control signal to external devices it must not glitch when powered on.

Is there anything I can do to improve this circuit? Or are PMOS-Transistors entirely unsuitable for this purpose. I already thought about using NMOS instead, but then I would have to add a charge pump to get above 12V which would add an undesirable amount of cost and complexity.

Since I do not have to source a lot of current (/the voltage drop is not that relevant), would it help to use BJTs instead?

UPDATE:

I did some more measurements and the amplitude and duration of the spike is proportional to the load resistance. Removing M2 did not change the result.

This means that this is not a suitable solution for me because the load resistance can be very high. With R_Load > 10k the output voltage does not even go down to 0V.

So the real question seems to be: what are the alternatives? BJTs?

UPDATE 2:

The question is not why this happens (I know it happens because it takes a few microseconds to charge the gate), but how to prevent it. Another PMOS transistor will not help, because it could make the problem less severe, but it will still be there. Especially with light loads.

So again my question: Can I somehow make this better? What happens if I replace M1 with a PNP-Transistor and a base resistor (I don't have one to test at the moment)?


texts: How to calculate Vout from the MOSFET circuit

texts:
This circuit diagram is given in my book :

simulate this circuit – Schematic created using CircuitLab

and said that from the above figure , they calculate \$ \frac{V_{out}}{V_p}  \$ while considering \$r_{o2}\$ and write down the answer is:

$$
\frac{V_{out}}{V_p} = \frac{1+g_{m2}r_{o2}}{1+\frac{r_{o2}}{r_{o4}}}
\approx\frac{g_{m2}r_{o2}}{1+\frac{r_{o2}}{r_{o4}}}
$$

No detail calculation was given and I tried my self but could not reach the solution. How can I do this kind of calculation?

can someone show me step by step solution for this so that I can do this kind of problems by my self in future. thanks in advance.


texts: How are the USB packets generated on VCOM Port (USB CDC)?

texts:
I'm trying to understand how a virtual com port sends the packets over USB. The reason behind is that I want to send packets from a PC to an MCU configured as a Communication Device Class. If I send 63 byte message with a terminal on my PC, will the MCU get a single USB packet (assuming it is configured to receive 64 bytes per packet)?

Thanks.


texts:
In order to achieve this I was going to have the following setup:

Base Station

Raspberry Pi
Xbee 2mw

Led Station

Xbee 2mw
RGB LED http://www.pololu.com/catalog/product/1222

My main questions are:

Is it possible to use the xbee to drive the tri-color driver without needed a microcontroller, arduino or raspberrypi on the led station side?
If I want to expand this in the future, can I add more LED and drivers combinations to be driven by the same xbee?

I'm new to this so any help or advice would be appreciated. Thank you!


texts: 5V-5V isolated and load regulated power supply

texts:
Hi all

Requirement: 5V-5V isoltaed and load regulated power supply, load current-0-500mA

I am getting 5V output at no load, but when load increases output voltage decrease rapidly and at 500 mA load output voltage become 0.235 volt.I tried changing compensation resistor so as to increase gain, but it dint work. Can anyone suggest what should be done to keep the output voltage stable at 5V in 0 to 500mA load.


texts:
I'm building a device that contains microcontroller (Arduino) and several other modules. What makes me worry is the fluctuation of voltage at the Vcc input of one of the modules. High level scheme of power distribution is shown below:

When I measure voltage with my portable voltmeter then I get stable 5.0V at OUT1, however when I measure voltage at the Vcc input of 'Arduino MEGA Sensor Shield 2.0' (which is just providing a convenient way to connect all modules to Arduino microcontroller) then I see a continuous fluctuation of voltage in the range 4.9-5.0V. So I started to power off all modules one by one and I found out that it is CO2 gas sensor that is causing this fluctuation. When CO2 sensor is powered off then Vcc is stable. Then I powered CO2 sensor directly from OUT2 of X705 like shown below:

In such setup voltage is stable and no fluctuation is observed.

While it seems that I solved the problem I still would like to understand why the problem got solved this way and here come the questions:

Question 1:
From specification of X705 and all ICs it consists of I understood that despite there are 4 outputs there is still only one voltage converter (boost). So in other words this is not 4-channel power converter, but rather only 1-channel, and these 4 outputs are all connected to this single channel. If so, then why reconnecting CO2 sensor from Sensor Shield directly to X705 solves the issue with voltage fluctuation? Or I understood something incorrectly from specifications?

Question 2:
X705 is rated to provide up to 8A, but all modules connected to it consume max 500mA.
CO2 sensor itself consume max 85 mA. Why CO2 sensor is causing such voltage dropouts?
I understand CO2 sensor has internal heater which is being switched on/off frequently, but why it has such effect on Vcc line?

X705 consists of the following ICs:

Injoinic IP5310 Power Bank SoC with 3A charger and 3.1A discharger
TI TPS61088 10-A Fully-Integrated Synchronous Boost Converter
AO 4447A 30V P-Channel MOSFET
TI NE555 Precision Timers
TI CD4011B CMOS NAND Gates

Some links:

X705 description can be found here
CO2 sensor is MH-Z16
INA219 current sensor description


texts: Differential equation for a notch filter RLC circuit

texts:
I'm trying to write and solve a differential equation for this simple RLC notch filter and I'm not sure what I'm doing wrong.

simulate this circuit – Schematic created using CircuitLab

So first, I apply KVL to (1) the loop source-resistor-capacitor-source and (2) the loop source-resistor-capacitor-source to get what's essentially an RC and RL circuit:

\$ RC\frac{dI_R}{dt} + I_c = C\frac{dV}{dt}\$

\$ L\frac{d^2I_L}{dt^2} + I_R = V\$

Adding these, I get

\$ L\frac{d^2I_L}{dt^2} + 2R\frac{dI_r}{dt} + \frac{I_C}{C} = 2\frac{dV}{dt} \$

Using KCL I know that

\$ I_R = I_C + I_L \$

Using impedances, I get

\$ Z_C = \frac{1}{j\omega C} \$ and \$ Z_L = j\omega L \$

Based on the current divider equation, I have

\$ I_L = \frac{Z_C}{Z_L}I_R \$ and \$I_C \frac{Z_L}{Z_C}I_R \$

\$ I_C = -I_R \omega^2 LC \$

\$ I_L = -\frac{I_R}{\omega^2 LC} \$

If I put this into the differential equation, I get

\$ \frac{d^2I_R}{dt^2} -2RC \omega^2\frac{dI_R}{dt} + \omega^4LCI_R = -2\frac{dV}{dt} \$

If I try to solve this, I get positive exponentials, which I know are wrong since current won't increase without bound. I'm not sure how else to go about this. Any help is appreciated. Thanks!


texts: Voltage exceed source voltage over a coil when opening a switch

texts:
Well, I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

When the switch is closed for a long time, the current that is flowing trough the resistor \$R_1\$ and the coil is given by:

$$\text{I}_\infty=\frac{\text{V}}{\text{R}_1}=\frac{10}{100}=\frac{1}{10}\tag1$$

With that given I can solve what happens when I open the switch. The current trough the coil will stay in the same direction as when the switch is closed. Now, at the moment when I open the switch the voltage across the coil \$\text{V}_{\text{Y}_1}\$, is given as:

$$\text{V}_{\text{Y}_1}=-\text{V}\cdot\frac{\text{R}_1+\text{R}_2}{\text{R}_1}\cdot\exp\left(-\frac{\text{R}_1+\text{R}_2}{\text{L}}\cdot t\right)\tag2$$

  So, the voltage over the coil will start (when I open the switch) at \$-\text{V}\cdot\frac{\text{R}_1+\text{R}_2}{\text{R}_1}=-10\cdot\frac{100+100}{100}=-20 V\$, which is (absolutely seen) higher than the supply voltage. How is that possible? Or is the formula \$(2)\$ wrong?


texts: HD44780 based LCD display shows half-black, half-blank

texts:
I have been trying to get a HD44780 LCD display to work for multiple times. The first time was by parallel port from a computer, then multiple times using different PIC uCs. I am only able to get the display to show half of the dots (the right side of the screen) as black, and the left side as blank/white. I read from the internet that it means the display is not initializing properly.

The display is Tianma TM161A/B

    setData(0b00110000); // INIT
    strobeE();

    DelayMs(5);

    setData(0b00110000); // INIT
    strobeE();

    DelayMs(5);

    setData(0b00001111); // ON/OFF
    strobeE();

    DelayMs(5);

    setData(0b00000001); // CLEAR
    strobeE();

    DelayMs(5);

    setData(0b00000110); // ENTRY MODE
    strobeE();

void strobeE() {
    mPORTDSetBits(E);
    DelayMs(1);
    mPORTDClearBits(E);
}

I have used a logic analyzer, a logic probe and a multimeter to check if the connections between the PIC and the LCD are correct. I think they are.

A ( bad ) picture of my timings on a logic analyzer;

Link to the datasheet

What am I doing wrong?


texts: How is rise time related to bandwidth of the signal?

texts:
Say, I want to limit the rise time of my digital signal edges to avoid dealing with transmission line effects.

How do I determine the maximum frequency of harmonics in my signal knowing that my rise time is, say 5ns?

How do I determine corner frequency of my low pass filter knowing that hold time on the receiver chip is, say 10ns?

In wikipedia I've found the formula

$$
BW=\frac{0.34}{t_{rise}}
$$

does it apply in this case?

Edit

I failed to make myself clear, so I'll try to explain my line of thought.

Say, I have a 30HMz signal and my trace length is well below 1/10 of the wavelength. So I don't have to deal with transmission line effects in respect to that. But my edges are steep - 5ns. This adds some high frequency components into my signal that potentially will suffer from transmission line effects.

My idea is that I slow down edge transitions up to a point where I don't have to deal with transmission line phenomena. The question is twofold:

how do I calculate fastest rise/fall time that with the given trace length would enable me to traeat my circuit as "lumped"?
how do I slow down the rise/fall time?

Rise/fall time is time for voltage to change from 10% to 90% of max value. I know how to calculate the approximate speed of signal on FR4 board.


texts: Breaking a 16-bit long int to write into eeprom?

texts: I am writing data to eeprom AT24C16 using PIC microcontroller pic18f4520. Every address of this eeprom can hold 8-bits while I am using long int's to store data that are 16-bit in size. How to break long int into 2 8-bit parts to write them and how to get them back together after reading from eeprom??


texts: Header pin plastic sliding off stripboard

texts:
When I was soldering header pins onto a stripboard I noticed the plastic in the middle of the pins had become extremely loose to the point if I turn the board upside down the pins will fall off the stripboard.

What I want to know is how do I stop this from happening or is this what usually happens?

I’m using a 5 to 10 year old 40 watt soldering iron with a lot of grime on the iron

And these are the header pins I’m using. The plastic being the black bits→

This is where I bought the pins: http://www.maplin.co.uk/p/254mm-pin-strip-jw59


texts:
I have an STM32F2 development board that came with a PSRAM (IS61WV10248BLL), and I have a custom board with a different PSRAM (MT45W8MW16BGX).

I have managed to get the PSRAM on the development board to work fine. However, I'm having problems driving the new PSRAM on my custom board. The main difference I see between the two memories is that the new PSRAM has more address pins. I have made sure to properly initialise all my clocks and GPIO pins, and I have checked that the ARM memory controller has reasonable settings.

What difference between the two PSRAMs could cause my old driver to go wrong?

Below is the memory controller configuration I am currently using:

  p.FSMC_AddressSetupTime = 0;
  p.FSMC_AddressHoldTime = 0;
  p.FSMC_DataSetupTime = 4;
  p.FSMC_BusTurnAroundDuration = 1;
  p.FSMC_CLKDivision = 0;
  p.FSMC_DataLatency = 0;
  p.FSMC_AccessMode = FSMC_AccessMode_A;

  FSMC_NORSRAMInitStructure.FSMC_Bank = FSMC_Bank1_NORSRAM2;
  FSMC_NORSRAMInitStructure.FSMC_DataAddressMux = FSMC_DataAddressMux_Disable;
  FSMC_NORSRAMInitStructure.FSMC_MemoryType = FSMC_MemoryType_PSRAM;
  FSMC_NORSRAMInitStructure.FSMC_MemoryDataWidth = FSMC_MemoryDataWidth_16b;
  FSMC_NORSRAMInitStructure.FSMC_BurstAccessMode = FSMC_BurstAccessMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_AsynchronousWait = FSMC_AsynchronousWait_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignalPolarity = FSMC_WaitSignalPolarity_Low;
  FSMC_NORSRAMInitStructure.FSMC_WrapMode = FSMC_WrapMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignalActive = FSMC_WaitSignalActive_BeforeWaitState;
  FSMC_NORSRAMInitStructure.FSMC_WriteOperation = FSMC_WriteOperation_Enable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignal = FSMC_WaitSignal_Disable;
  FSMC_NORSRAMInitStructure.FSMC_ExtendedMode = FSMC_ExtendedMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WriteBurst = FSMC_WriteBurst_Disable;
  FSMC_NORSRAMInitStructure.FSMC_ReadWriteTimingStruct = &p;
  FSMC_NORSRAMInitStructure.FSMC_WriteTimingStruct = &p;


texts: Another question about CMOS tri-state buffer internal structure

texts:
About my previous question: CMOS tri-state buffer internal structure

I have just one more question:
is the value that "activates" the transistor related to the value of the Output? Because if I choose the input "high" and the control "high" I will activate the top transistor in "low" but the output value should b e "high". So it's not related, right?

Thanks!


texts: Why charging time is same and discharge time is different for two inputs in dual slope integrating ADC?

texts:
For different input voltages in dual slope ADC, charging time remains same but discharge is proportional to the magnitude of the input voltage. How it works in that way ?

Charging time is independent of input magnitude but discharging time is dependent on magnitude. Why ?

What is the circuit ensures this ?


texts: ESP Breakout PCB design (KiCad) questions

texts:
My first PCB made with KiCad. I have some specific questions about my design. First I was not sure of this would have been another down-vote magnet but this article encouraged me to post this.

Capacitor placement; should C2 be connected to the ESP pins directly in stead of the front and back plane? It is supposed to be a decoupling capacitor.
Should I redraw sharp corners in a trace like on the back plane near pin 4.
What is the downside of using GND as back plane and VCC as front plane in stead of using traces only. It's a lot of surface, it does not feel right to just 'power' the entire front and back of the PCB.

Note: P4 is for input power to the board and the board will not be used for programming the ESP, just for continues use with deep sleep enabled.

Please add a comment when you down vote, I am here to learn.

All the data is on GitHub, in case you need it.

UPDATE
Added a better regulator, added a capacitor, added two mounting holes, removed the VCC field from the front, removed the crazy via's, moved some parts around and used the space below the components for traces.


texts:
(source: tomshardware.com)
While i am quite familiar with most of the specifications on a power supply unit like this one, I fail to understand what is going on with the negative voltages.  I have a few theories, though.

The negative voltages are just the grounds which correspond to the matching positive voltages.
These are actually at negative potential relative to ground

However, neither of these explanations really explains why you would have these outputs sourcing half an amp of current.
If they were the grounds, then they would have to sink just as much current as the positive side was putting out.  In addition, there isn't a negative output to match with every positive output.
However, if they really were at a negative relative potential to ground, I would not expect them to be sourcing current, because that current would have to flow against a voltage differential.
So, what is going on with these negative voltages?


texts:
My idea is to start soldering and I would start with something quite simple.
I chose the project (https://cdn.makezine.com/make/08/pummer.pdf), a pummer with solar cell charging up a supercapacitor and then starting to pum a led when the capacitor is full.
In the schematic and explanatiuon it is suggested a solar cell giving 20mA at 3V.
Now, I quite understand the schematic, it isn't something too complicated. What I do not understand is the solar cell choice.
Looking at the 74HC240 datasheet (http://assets.nexperia.cn/documents/data-sheet/74HC_HCT240.pdf)
I see the following data:
Input Clamping power: +/- 20mA
Supply Current: 70mA.
What happens if I use a solar cell with a lower current intensity?
I found one with Isc=13.5µA.
Does this suits the circuit or it will be a bad choice? Maybe I can use two solar cell with that specs in parallel?
Thanks
Ale


texts: Li-ion Battery pack not charging, but batteries have voltage

texts:
My robot cleaner stopped charging after a week of not being used. I gave the same error as when I removed the battery.
I then measured the voltage across the battery terminals, which is 0.01VDC.
I then pried open the case and measured the voltage across each battery, which is 4 VDC, so the batteries seem OK.
So I suspected the circuit is malfunctioning, and when I search for help, all I can find is how to revive dead batteries, nothing about the circuit.
Any tips on attempts to troubleshoot this or determine if the circuit is dead? It would be a shame trash the entire device its fixable.


texts: Suppress Certain Overtones In A Musical Instrument's Sound Wave

texts:
So, just like the title suggests, my college professor and I are trying to suppress certain overtones of an instrument's sound. I have a microphone hooked up to an oscilloscope, and I'm using the oscilloscope to perform an FFT analysis of the sound. I am trying to come up with a way to pass the signal through a hardware device to suppress certain overtones in the FFT analysis, and then record the result so we can hear what it sounds like when all you have are just the odd or just the even overtones, or even just the fundamental frequency.

I'm pretty sure I've heard somewhere that you can implement this in hardware, but I'm not entirely sure where to begin. Oh and this isn't a homework assignment. My professor and I are doing this just for the hell of it.


texts: Superposition principle: Dependent sources treated as independent sources

texts:
Since I began studying, I was taught that when analysing a circuit using multiple sources, independent sources could be turned off, meaning that I could transform a voltage source into a short, and a current source into an open circuit and analyze the circuit by how each individual source acts on it.

However, regarding dependent sources, every electric circuits book I've read says the same thing:

  "Dependent sources should never turn off when using the superposition principle analysis, they should be left intact since they are controlled by variables somewhere in the circuit".

However recently I've noticed that I can get the same results if I treat the dependent source as a regular independent source. Ive simulated this, compared to the end-of-chapter problem solutions and it all turns out the same. Take the following problem from Alexander/Sadiku's Book as an example, which states:

  "Find Vx using the superposition principle"

simulate this circuit – Schematic created using CircuitLab

Normally I would leave the dependent source on, turn off the 4A current source and find Vx1, then I would turn off the 6A current source and find Vx2, add them up and find Vx.

However, if I treat the dependent current source as an independent current source, I get the same results, Here's the procedure I followed:

Turning off both current sources:

simulate this circuit

Finding Vx using Ohm's law results in:

$$Vx1 = -(4Ix / 10) * 8$$
$$Vx1 = -3.2Ix$$

Now I shut down all sources (including the dependent voltage source like if it were an independent source) and leave the 6A source on:

simulate this circuit

Using the current divider formula and multiplying by 8 I get Vx2

so:

$$Vx2 = (2 / 10) * 6 * 8 = 9.6V$$

Finally, I turn off all sources but the 4A current source:

simulate this circuit

Using the same procedure as above, by current divider I find Vx3:

$$Vx3 = (2 / 10) * 4 * 8 = 6.4V$$

Finally, the total voltage Vx is the sum of each individual voltage Vx (Vx1, Vx2, Vx3):

$$Vx = Vx1 + Vx2 + Vx3 = -3.2Ix + 9.6 + 6.4$$

I can find Ix by Kirchhoff's Current Law, the currents in the top node of the circuit are:

$$Ix + Vx/8 = 6 + 4$$

Solving for Ix

$$Ix = 6 + 4 - Vx/8$$

Using the above equation to eliminate Ix from Vx:

$$Vx = -3.2(6 + 4 - Vx / 8) + 9.6 + 6.4$$

Solving for Vx:

$$Vx = -26.667V$$

And this is the simulation I made on Multisim:

So my question is: What is going on? Why is it "prohibited" to treat dependent sources this way when the results are the same?


texts: The KR512 is claimed to be equivalent to the MK5009, but it clearly isn't - the pinout is different, for a start. Does anyone know what the internal logic looks like? The thing clearly has a RC oscillator and some counting circuitry, but is it selectable, like the MK5009, or fixed? The published diagram is far too vague to be useful, and I have not found a specification. For comparison, the Mostek MK5009 is at https://datasheetspdf.com/pdf-file/612322/Mostek/MK5009/1


texts:
The watchdog of an ATMEL ATXMega128 should have been enabled with fuses. It triggers a reset, if the timer was not reset within the configured time span.
I want to be sure, that it is enabled and working properly.

What is a good method to verify that the watchdog is enabled and working on the finished PCB?

Is it common practice to prepare a spare input signal in order to trigger the watchdog artificially? Should the watchdog trigger, if I pull the external oscillator to GND, or will this stop the watchdog too?


texts: How to calculate motor specs for vending machine

texts: I'm trying to make a vending machine and I need motor to deliver the products. How can I calculate specs such as torque, rpm, power etc? Maximum weight would be 10 soda cans. Let's say each weigh 0.5kg it gives us total of 6kg and there is the spring as well but I don't know how much it weighs. How do I determine which motor to buy? I found one that's 60 rpm, 15 kg/cm torque, 12 V 100mA. Is it any good?


texts:
I am going to design a circuit that should have 2 inputs and 2 outputs.

when both inputs are low both outputs should be low

when input 1 is high and input 2 is low, output 1 should be a square wave alternating between 0(low) and 1(high) with duty cycle 50%. output 2 should be low

when input 2 is high and input 1 is low, output 2 should be high. output 1 should be low

when both inputs are high both outputs should be low.

I need some of your ideas on how this is to be done.

This is what i have done so far:

simulate this circuit – Schematic created using CircuitLab

I have done this is MULTISIM and both outputs works fine.

The issue is i want the period of the square wave form to be 0.5 seconds. I am using the equation f= 1/2.2R1C from this tutorial:

electronics-tutorials.ws/waveforms/generators.html

But i am not getting the desired period


texts: Can I trust these microwave power readings?

texts:
So I've got an old Hughes TWT that supplies roughly 20W across the Ku band (12.4 - 18 GHz) that has a waveguide output flange (WR-62). I am "gently re-purposing" it to be driven at a lower frequency (11 GHz) and running the power through a series of WR-62 directional couplers to measure the actual power output via some N-type coax adapters and power sensors.

11 GHz is clearly above the cutoff frequency for WR-62, but I am getting some strange power readings. I expect that from the amplifier; I'm not surprised that the gain or saturated output varies a lot once you get out of band. What's surprising is that the power output is reading higher than what the amplifier produces in band - from 40-60 watts! I'm fairly confident that I have the offset on the power sensors correct. Any idea what could be happening here? I'm fairly certain the output is not actually 40-60. For context we see around 30 watts at the lowest "known good frequency" (12.4 GHz).

My best guess was that we might have some non-fundamental modes in the waveguide that make the area where the coax transition probe penetrates the waveguide read higher. Just curious what any folks with WG / TWT experience think about this.


texts: Soldering a SMD sensor - options without etching PCB?

texts:
I would like to break out this sensor. I don't have the equipment to design and etch my own PCB.

Do most sensors come in standard dimensions, such that a pre-made break out PCB could be obtained?  How would I go about finding such a break out PCB?

The dimensions are listed in the datasheet (below), as well as a notation of 5-SMD, but I haven't been able to find an appropriate board.

Am I approaching this wrong?  It has no leads, but I assume the solder will flow under the pads just fine.

Thanks.

Update: I ended up doing both - the spacings were compatible with standard protoboard so initially I soldered to that.  But ultimately I learned to use Eagle and got a board fabricated for about 20 bucks.  Definitely recommended.


texts: Confusion about transistor circuit analysis and voltage divider

texts:
I'm not sure how to title this question, any suggestions are welcome.
I want to analyze this circut, it's a zener regulator and I am following this video that  does the analysis

The proposed method is to sum \$V_{zener}+V_{be}\$ and then use the voltage divider (I will make it equal for easy calculations) to  calculate the  output voltage.

I feel this is very arbitrary, since it does not seem to take the other transistor into consideration, if it where to be replaced with a resistor or a wire, this analysis will not work.
It seems there are some assuptions that are not clear, but I'm not sure what they are.
here for example I have substituted the transistor that was not used in the analysis with a resistor, changing the behaviour of the  voltage divider completely. while the new behaviour is not unexpected when analyzed separately it was not obvious at all  that this could happen on the first analysis, my guess is that something was assumed but I cant  quite understand what it is.

could somebody clarify it? what is the  assumption for the first analysis to work? why is there no mention of the other transistor if it's  so necessary?.
EDIT: I have had some awesome answers and thanks to them I have gained new insights to how this circuit works, however my question is related to this partcular analysis approach and the assumptions that have to be made to make this  approach viable, because I want to perfect my analysis technique.
However the answers here  so far are awesome and I REALLY appreciate them.


texts: Connecting copper wire to a nine volt battery

texts:
I don't have a cap for a nine volt battery so I am connecting to it with copper wire. Which connector is positive?

Have I wired these up correctly?


texts: Short between GND of Arduino and AC powered circuit

texts: Upper left corner is a simple AC powered circuit that can supply 15mA of DC current. Lower left is an Arduino connected via USB to desktop computer. The meter shows a voltage of 1.58V between the Arduino ground and negative of the DC output of the circuit. So there must be a potential conduction path through the USB, computer power supply. Shouldn't the transformer in my computer power supply isolate the USB ports?


texts: Relaton between IB, α and ICO near cut-off region for a bjt in CE mode

texts:
I am reading Electronics and Devices by Boylestad and it says:

$$
\begin{align}
I_E &= I_C + I_B  &(1)\\
I_C &= \alpha I_E + I_{CO}  &(2) \\
I_E &= \alpha I_E + I_{CO} + I_B  &(3)
\end{align}
$$
Is equation 3 valid for all regions of operation?

because if equation 3 is valid near cutoff region, if \$I_B\$ is decreased to zero,
either \$\alpha\$ has to increase or \$I_{CO}\$ should increase.
Also is there any relationship between \$I_B\$, \$\alpha\$  and \$I_{CO}\$?
How to connect the concept that, if there is no base current, no collector current flows in the transistor?


texts:
Is there any way to use a PICAXE  (08M2, to be precise) to play a small sound file (Not beeps and buzzes, but actual sound), perhaps loaded from an i2c EEPROM chip? I'm thinking something similar to the ThinkGeek EvilTron: two or three seconds of decent quality, mono-speaker sound. If not, is there a small/inexpensive slave chip that can accomplish this? I'm not looking for something fancy or complex, just enough to amount to a homemade EvilTron. Thanks for any pointers.

Here's a link to aforementioned EvilTron, just so you know: EvilTron

(also note I'm fully intending on using speakers well below the PICAXE's current limits, so no need for an amplifier circuit)


texts: Can I electronically trigger a PIR motion sensor?

texts: I would like to trigger a PIR sensor using an infrared LED.  Is that possible?  My goal is to simulate motion in front of the PIR, when there otherwise is none.  I tried using a handheld remote control, but that didn't seem to work.


texts: USART2 setting for stm32l micro controller

texts: Is there any default pin setting for stm32l micro controller?. Can we use PD5 or PD6 as txd and rxd instead of PA3 or PA4?


texts: Comparing an Arduino DC-DC boost converter with LM2577 modules

texts:
I have seen this video

with this code:
/*
 * This is an example code for a BOOST converter circuit made with arduino + feedback
 * I've used arduino NANO. We have to set the timer of the PWM on pin D3
 * The feedback is connected to A1 and we set the desired voltage with a
 * potnetiometer connected to A0.
 *
 * Subscribe: http://www.youtube.com/c/electronoobs
 * webpage: http://www.electronoobs.com/eng_circuitos_tut10.php
 */

int potentiometer = A0; //The input from the potentiometer is A0
int feedback = A1;      //The feedback input is A1
int PWM = 3;            //Digital pin D3 por PWM signal
int pwm = 0;            //Initial value of PWM width

void setup() {
  pinMode(potentiometer, INPUT);
  pinMode(feedback, INPUT);
  pinMode(PWM, OUTPUT);
  TCCR2B = TCCR2B & B11111000 | B00000001;    // pin 3 and 11 PWM frequency of 31372.55 Hz
}

void loop() {
  float voltage = analogRead(potentiometer);    //We read the value of the potentiometer, which is the desired value
  float output  = analogRead(feedback);         //We read the feedback, which is the real value

  //If the desired value is HIGHER than the real value, we increase PWM width
  if (voltage > output)
   {
    pwm = pwm+1;
    pwm = constrain(pwm, 1, 254);
   }

  //If the desired value is LOWER than the real value, we decreaase PWM width
  if (voltage < output)
   {
    pwm = pwm-1;
    pwm = constrain(pwm, 1, 254);
   }

   analogWrite(PWM,pwm);  //Finally, we create the PWM signal
}

I would like to know about its output quality for powering some IOT modules like ESP8266 by AMS117 regulator and ESP8266, in comparison with commercial the LM2577 XL6009  DC-DC boost converter, output quality for this kind of usage.


texts:
I want to power two heating strips. I have available to me a three phase contactor to pull power, which is activated by a temperature controller. I am hoping to split this power into two single phases to power two heating strips. The contactor itself definitely receives power and emits a large clicking noise.

However, my heating strips do not appear to be drawing power. I am unfamiliar with contactor setup schemes. I currently have the relay segment of my temperature controller connected to the power in of the contactor (denoted by connections A and B). Meanwhile, heater strip 1 is connected to C and D, and 2 is connected to E and F.

Do I need to bridge the middle connection to draw power from the contactor, or is there something else I am missing?