texts: Control a 12 v circuit using wall plug 220v ac timer

texts: I want to use a standard supermarket 220v ac timer to switch a 12-volt circuit. I was thinking about letting the timer run on the outlet, and just desolder the relay separating it from the ac, keeping the 24 v line needed to drive the relay and hooking my 12 v line on the switch contacts. Is it a good idea?


texts: Confusion about what EM fields really look like, and how that relates to data transmission, waveguides etc

texts:
After a discussion at work a few days ago, I realized I don't have a very good understanding of what RF energy is truly like. I've always thought, via physics and EE classes, that all EM waves (including RF) was a nice set of electric and magnetic fields oscillating perpendicular to each other, with the direction of propagation in the third axis like the picture below shows.

Well, after reading this thread

I realized it is not so simple. I understand the last answer in the thread, how the EM waves actually look like they are 'ballooning' out of the antenna and the frequency is actually the flux-density, that is where the 'sine wave' comes from. That makes perfect sense. Check out this simulationvideo

What doesn't make a lot of sense to me is how to visualize the amplitude with this simulation. The reason for my confusion is this:

Take a microwave oven for example, where the outer mesh holes are essentially acting as a waveguide and blocking the microwaves from escaping. This is said to be because the wavelength of the RF is too large. Ok.

In the picture below, I've tried to illustrate my confusion. I've always thought the waves travel like picture 1, and in that case the amplitude would cause the wave to not pass through the hole. My coworkers are telling me in reality it is like picture 2, where the sine wave is actually moving to the side and that is why the wavelength is what causes it to be blocked.

I just don't understand how #2 could be true, based on the simulation video above. If the frequency is based on the flux density, it would seem the sine waves are 'in-line' with the direction of propagation just like picture 1 in my drawing. I also don't understand how a receiving antenna could make sense of any data if the sine wave component is perpendicular to it, to my understand the data must be in-line, with each bit moving towards the antenna like picture 1.

I hope this makes sense, I am awfully bothered by my confusion and would love some clarification. Thanks!


texts:
First off, I know nothing about electrical engineering. So please bare with me.

I'm designing a faceplate for a moto360 smart watch that has a small area that overlays the bottom edge of the screen. Set into that area is 3 buttons made from a clear orange resin that act as a stylus.

These buttons correspond to tabs programmed into the on screen watch face. Pressing these buttons should trigger the software to switch to the corresponding tab and cause a patch of the screen that is hidden by the plate to turn bright white just below the contact point. This illuminates the clear resin button, giving the illusion of a tiny LED.

As you may have guessed, I didn't realize that simply adding a drop of rubber from an old stylus to the bottom of the button wouldn't be enough to trigger it.

I've done some reading and I feel confident enough to know why. Basically, not enough of a draw to pull any electrons from the screen? (Not really the point of this post either way.)

Anyways, my question is, is there a type of affordable space age material that I could attach to the bottom of the 2mm diameter button that would work? Or maybe some kind of clear conductive resin or additive that my caster could use?

Here is a picture of the tiny tiny button assembly as currently planned. The orange pieces are the clear resin and slide into the green pla section. The black dots represent the now useless stylus material.

http://puu.sh/iwnnB/b586ae5189.jpg

This is a very rough picture of how the final plate should look when assembled. This is not an item I have made, but it is a decent representation of how the item should sit around the watch.

https://goo.gl/photos/E2dc9jmBQumnRcdcA


texts: Notch Filter with high Q easy to realize on breadboard

texts:
So I have to get rid of two frequencies in an audio signal. I use for that two notch filters.

According to my spice simulation I should get pretty good negative gain:

The problem is the two frequencies already have a gain compared to the audio signal of around 15 dB and I loose some gain in practice when I get the frequency response of the physical filters on the impedance analyzer. I still get an audible buzz. Any clues on how to get rid of those two frequencies?


texts:
I am novice in electronics, so please bear with me.

I am searching for a small distance sensor (as small as possible) that I can use to measure a distance between 0 and 30 cm precisely (precision less than 1 mm). This sensor must be able to communicate the distance data wirelessly (wifi or bluetooth) with a PC. Could you please tell me if there is any sensor that satisfy these requirements.


texts: Amplify PWM output from 3v3 to 10v using an amplifier

texts:
Actually I'm already using an amplifier to convert from 3v3 signal to 10v signal. Since different consideration like pin and board constrains, I'd like to use the same amplifier circuit to output also a PWM signal. So from 3v3 PWM get a 10V PWM.

Main problem is, when I generate a PWM from 1kHz to 10kHz (teorically maximum that I'll need) I've a very strange output.

I've tried two amplifier models:

NCS20074DR2G

OPA4196ID

Both of them acts in a same way (Yellow is PWM and Purple is Amplifier output):

Schematic that I'm using is:

simulate this circuit – Schematic created using CircuitLab

You can see a gap between R5 and R2, actually this two resistor are directly connected. But I've some pads where I can put a capacitor or a resistor + led that are not mounted during test.

Are this two devices that I've tried suitable for this porpoise? Maybe I've too big resistors?

Another doubt that I've is why the output is cut in 4 steps? My 10V output is cutted in 2.5v steps.


texts: What is the ground port on an analog oscilloscope for?

texts:
I just bought my first analog oscilloscope (GoldStar OS-7020A) and noticed it has a port on the front labeled "ground". What exactly is this port for?

I thought it might be for plugging in a ground clip for probes that don't have one included, but there are two channels and only one ground port, so I'm not sure. Is it simply for providing a convenient ground connection for other devices?

Could I, for example, attach my anti-static wrist strap to it? Would the oscilloscope have to be on for that to work? (Electronics newbie here, so please forgive me if this is a stupid question.)


texts:
I have a built a simple voltage doubler. the circuit is as below:

simulate this circuit – Schematic created using CircuitLab
This represents only one stage, and my circuit has 4 stages. The capacitors are 1nF 1kV ceramic capacitors and the diodes are  BY228GP-E3/54 (2.5A Iavg 1500V silicon diode with max 1.6V forward voltage drop) the circuit is shown below:

So this circuit is supposed to be connected to mains (230V) to generate about 2.6 KV open circuit output voltage.
Before doing so, i tried connecting a 24Vrms 50Hz sine wave to the input to make sure the circuit is working fine, and I simulated this in Ltspice to have sth to compare my results with.
The circuit acts completely different! The first capacitor in my circuit and the following diode (C2 and D1 in the schematic) form a voltage clamp. the voltage across C2 in the simulation was as follows (as one would easily guess):

the voltage measured across the first cap on the proto board is shown below:

This cap seems to consume all of the energy of the injected signal somehow!
I am a bit lost, and could use some help, thank you in advance.


texts: Measuring total energy used by a project

texts:
Is there a cheap/simple way I can empirically measure the total energy used by my project over a sample time of several minutes?

It's a microcontroller based system which repeatedly wakes up, does some work then sleeps. Typically it will be awake for < 10ms. Looking at the voltage drop across a 1Ω shunt resistor with an oscilloscope, I've measured the energy consumption of each work period by calculating the area under the curve. Using an ammeter I've found the quiescent current during sleep.

In theory, knowing the sleep period I could calculate an energy estimate. But, I'd like to test the system as a black-box without making assumptions about the firmware.

Is there a device or method for accurately measuring the total energy usage of a device over a long period? (preferably something cheap).


texts: Calculate time it takes for a capacitor to discharge, when it is applied to VGS of a transitor

texts:
I want to usea 1uF capacitor to create an electric field between Gate and Source (VGS applied to dielectric) of a transitor.

simulate this circuit – Schematic created using CircuitLab

Since no current is flowing can i assume the eletrci field persist for very long time (years)?

If not, what do i need to calulate the discharge time?
I'm guessing the dielectric leakage?


texts: We know that current is passed through a circuit if there is a potential difference between the two terminals of the conductor. But in the case of a short circuit, we say that there is no potential difference between the two terminals and a large amount of current is passed through it. It's a violation of Ohm's law. Isn't it wrong to say that there is no potential difference between the terminals?


texts: How do you regulate a car battery down to exactly / not more than 12V?

texts:
My problem:
I want to light up the inside of transporters with a 12V LED strip. But I don't think powering it with the 12V car battery directly is a good idea. Although the name implies 12V, a car battery does not deliver exactly 12V, but between 13.5V and 11.5V depending on the level of charge and rate of (dis)charging.
So with that, I fear overvolting the LEDs. The forward voltage of LEDs grow very little with the current passing through them, so overvolting can easily increase current by a lot and therefor reduce their live time massively.
My solution so far:
Can't be that hard to regulate the voltage down to 12V, right? ... wrong.
First I tried a KA7812 12V Voltage Regulator [PDF] that I had laying around. But turns out these types of regulators only work for input voltages higher (at least 2V) than the regulated output voltage. (so ≥14.5V→12V, but 13V→11.1V, 12V→10.2V, ...)
Then I tried to design my own voltage regulator that can regulate voltages down to 12V, but lets voltages lower than 12V pass (more or less untouched). I started with the basic op-amp design:

But I soon discovered that this design has also a minimum voltage drop of at least 0.7V because the base-emitter junction not allowing the op-amp to regulate Vo=Vi. When Vo is the emitter of the transistor and the op amp can only output it's supply voltage (=Vi) as a maximum to the base pin, a reduction of 0.7V is given to satisfy the BE forward voltage and CE current can flow.
And it's getting worse: Assuming Vi is near 12V, then Vo will be even lower than Vi-0.7V. An op amp provides an output voltage floating between it supply potentials with a padding of ruffly ±2V. So 12V as Vi makes 10V as a maximum op amp output, that with the 0.7V forward on the BE ... so Vo can't be more than 9.3V!
So after more hours of trial and error than I am willing to admit, I ended up with his design:

It works in simulation: The voltage drop on Vi≤12V is minimal (on a weak load) and at no point strip± gets bigger than 12V.
But I have never seen such a design before. At this point I'm not sure if this circuit works well in practice or if there are better ways of doing this. So my question is: Should this for me be the way to go?


texts: Signal distribution, buffers, rise times and EMC

texts:
I am designing a DSP based audio mixer. There are 4 AD/DA converters (AD1939 and AD1974) and a DSP (OMAP L138), which is on a carrier module. I am distributing the frame clock (48kHz) and the bit clock (~12.3MHz). I have not buffered the TDM digital audio signals as they are point to point.

The frame clock and the bit clock are generated by the master converter and is sent to another slave converter and two inputs in the DSP. The bit clock is sent to two DSP inputs.

I am using a IDT5T30553DCGI to distribute the signals but the rise times in the specs look ridiculously short, with a maximum rise time of 1ns for Cl=15pF. The boards material will be FR4, the lines will be 50Ω and 6-10 cm long. They have been back terminated with a 33Ω series resistor, close to the driver.

The nano second edges are going to create radiation around the 350MHz and multiples. I have been looking for other IC options but their rise time specs are in the same nano second range.

The audio board has also ethernet and all the analogue audio I/O amplifying stages. The mixer board is sitting in a tray with other boards like HD analogue video.

I do not need to pass any EMC compliance tests or similar. Should I worry about EMC aspects in the audio board or adjacent?  Should I worry for those ultra short edges? Am I being too paranoid and it is just fine? Am I creating a problem by distributing signals with those ICs and I should not use anything at all?


texts: I just started learning this in class and am not understanding how to answer.. A parabolic trough has an active area of 18.1 m2, and produces 2960 W of power. The average solar power that falls on the active area of the parabolic trough is 1195 W/m2. Calculate the efficiency of the parabolic trough.


texts: is it possible to use the CD4013 IC inverted output while in frequency divider setup ?

texts:
I am not having success with using the "not Q" output of the CD4013
http://www.ti.com/lit/ds/symlink/cd4013b.pdf
when the CD4013 is connected for frequency dividing as below:

I need both Q and "not Q" to drive an H bridge, and I'd save adding a "not gate" if I could  use the "not Q". So how could I do it ?
When I wire the "not Q" to my mosfet driver (IR2184) the whole CD4013 stops working (even if I put a 10k resistor in between the 2 ICs), but I can get it to work at low frequency when my finger touches the CD4013  and my feet touch the ground.


texts: Variation of the BASE Current with the COLLECTOR Current in CE config?

texts:
So can anyone explain me how the collector voltage(V (output)) will vary with variation in base current with respect to the following figure?

simulate this circuit – Schematic created using CircuitLab


texts:
I was asked to draw over the given graph in this question the output resulting from the SR.

Could it be something like this?


texts: Strange switching behaviour when using bipolar stage to drive mosfets

texts:
This circuit is intended for inverter application and i wanted to simulate it using proteus but the problem is It behaves strangely when i use bc547 to drive the mosfets.

(I didn't have a proper transformer model for proteus so i just put a resistor R8 for just a quick simulation)

When I removed BC547 and put the input signals(10 khz) directly to the gate resistors I got good waveforms:

Is BC547 really that bad, Or that is something wrong I did?
And what other solutions do I have (Mosfet current will be 10A.)?


texts: My circuit is almost identical to the Wikipedia but with 5V in, 1pF cap, 4 pieces of IN4004 diodes. I am not certain whether it is AC or DC here and there (actually I do but not want to break my multimeter). Is there some safe way to test its type? My multimeter has only separate modes for AC and DC but not a common mode for both of them. So how to find out unknown voltage type?


texts: What are some good Electrical and Electronics blogs worth following?

texts:
This is a soft question. I am newly admitted to Electronic and Electrical engineering . Under this branch there are multiple domains from which I may work in one of them in the future.

For knowing where is my particular interest in one of such particular domain, first of all I should know what are they (each domain) what are do's and don't. What is its scope and new technologies? And from the related blogs, sites I think that I could get such information.

So I want to ask about some good sites, magazines or blogs where I can get more info on the various fields and the latest trends about Electrical and Electronics research.

Or, should I just check out "classical" providers like Springer , IEEE Transactions , Elsevier etc ?


texts: A fundamental question about filter phase response effects

texts:
This is a fundamental question about the idea of filters. As an example lets assume we have a passive LP filter with 1uF cap and a 100 Ohm resistor. Now lets assume our input signal is composed of addition of a 1V 4Hz signal and a 1V 400Hz.

Now if I plot the Bode diagram, the filter amplitude response is unity both at 400Hz and 4Hz.

But there will be a 15° phase difference between these signals at the output. We know that adding two sines with same amplitude but with different phases will yield a sine with less than twice the one of the two amplitude.

So even a filter is extremely flat in passband, the phase response seems will corrupt the output signal shape in time domain. I guess this will have no effect in frequency domain.

So what is that phenomenon called? And seems no filter has flat phase response in passband. Can we say this is important only if we are dealing the shape of output signal in time domain? Is there a rule of thumb for the maximum phase shift of a filter in passband?


texts: Behaviour of capacitor discharging through a transistor's base

texts:
I have the following circuit which attempts to turn on and off LED in a gradual manner (instead of having abrupt change between states).

So when I press S1, LED1 will light up gradually, thanks to C1's charging. My eye can observe a 1 second period till the LED fully light up. This works as expected. However, If I release S1 afterwards, LED1 will gradually turn off, but it take very long, like 30 seconds or so till the light completely vanishes.

So C1 discharges really slow, and I don't understand this behaviour. I thought C1's discharging process should be fairly fast, since there is only a 220ohm resistance (plus the diodes' resistance) between its two poles? Can someone explain to me what's happening here?


texts: Need 300mA current to drive a transducer

texts:
I am working on a project in which I need to use a preloaded value to vibrate a transducer.
So loaded required values into Arduino Uno, converted into analog values using R-2R DAC and buffered values using ua741, all should work in 5 volts.
Now the problem comes:

I need around 300mA current to drive the transducer (resistance is 10-20 ohms) can you please suggest me a transistor (preferably BJT) which gives particular current in 5 Volts power supply?


texts:
After some primer reading on jtag it looks to be a nifty means to test a FPGA logic design in a consistent and sustainable way.

Let's use altera max 10 as an example. I've read this MAX 10 JTAG Boundary-Scan Testing User Guide. My reading is, to be able to access the user logic the jtag tester (a host pc most likely) will send USER0 or USER1 instructions.

Questions are:

How do you implement some logic in the user logic design to catch the commands and parameters, and return some results? Examples?
On the host, how do you send those commands, preferably with a low-cost or open-source tool? With some experience, I know Olimex produces some good jtag adapters, and also altera usb blaster is a popular tool. Openocd may be a popular software candidate.

It will be great if somebody can shed lights on any part of the questions.


texts:
i need change 5v to 12v that it use to supply a device;
for this use MC34063A step up voltage converter;
this site can calculate the parameter.

i have problem all thinks is OK but i have same voltage at output!

how to find my mistake ?


texts: Time to Frequency Transform - Where are the Initial Conditions?

texts:
In a circuit with sinusoidal source and charged capacitors and inductors we have initial conditions:

$$u_{C}=u(0)+\frac{1}{C}
\int_{t_{0}}^{t}i(\tau)d\tau$$

$$i_{L}=i(0)+\frac{1}{L}
\int_{t_{0}}^{t}u(\tau)d\tau$$

and when we work in time domain we account for those in the equations.

If instead of phasors we use Laplace transform then we account for those initial conditions too

$$U_{C}(s)=\frac{1}{Cs}I(s)+\frac{1}{s}u(0)$$

$$I_{L}(s)=\frac{1}{Ls}U(s)+\frac{1}{s}i(0)$$

But when we move from time to frequency domain using phasors then I don't understand where those initial conditions appear. In the transformed equations I don't see initial conditions anywhere.


texts: Concern about bypassing capacitors on other side of the board (Current Flow)

texts:
I am designing a board with the usual layer stackup of

Signal
GND
VCC
Signal

On it I am placing a STM32F446VE which is 100 pin lqfp. As I am routing to every single pin on the package, and the pins are quite fine, the faning out of the pins is quite challenging.

To free up some space I toyed around with the idea of placing the many bypass capacitors on the other side of the board.

My first idea was to route it like this (a little tighter of course, this is just an example!):

This would ensure that all the current passes by the capacitor before it reaches the power pins on the processor.This however would not work as the vias connecting the capacitor to the processor are still part of the VDD and GND net and would therefor still internally connect to the power planes meaning some of the current would still pass through those vias directly and to the pins, not past the capacitor.

Is there a way in KiCad to ensure the vias would not connect to the inner power planes? Define the power planes around the vias?

I was not able to come up with anything simple, so some other routing ideas I had where the following. They still would not have all of the current past the capacitors but would be a little  smaller IMO:

What is the proper way to route this? and does this matter? Also, are vias on pads like in the 2nd picture a problem?


texts:
I would like to reach zero potential difference between me and my laptop
(to avoid ESD) before opening the back cover.

I'll connect my wrist strap to a common ground point, thru a resistorized coil cord.

I'm considering to connect the ground of the DC-jack to the same point.
Luckily, i have a spare power cable, which i can cut thru.

Is this a good plan?
Is it a good idea to also connect V+ (from DC-jack, not from adapter) to the common ground point?


texts:
Can someone explain the following telephone hold-on music circuit in throughout manner because I am still learning how to simulate circuit using gnucap?

When TR2 does not conduct, it switches off TR3 which also switches off TR4 in a domino effect? Besides, TR2 switches on, then TR3 is on which switches on TR4.

Why?

What are the purposes of diode D4, diode D6 and 10V zener diode ZD1 respectively in the circuit ?


texts: 12V - How to activate an electric item if battery is full

texts:
I have a solar system 12V connected to a PWM controller 20A and a lead-acid battery 80Ah deep cycle.

What kind of setup should I make to activate a pump (12V) if the battery is full ( >13.8V ) ?


texts: Is it possible to generate a sine wave formula using values from an array?

texts: so we have an Arduino code which includes an array, is it possible to make those array disappear [in the code] and instead formulate a sine wave formula for those [array] to make the output in sine waveform? Yes or No? if yes, how can I make it possible? Thanks!


texts: Sprague Vitamin Q High Voltage (25 kV) Power Capacitor

texts:
Might any of you know more details about these high voltage capacitors? Specifically:

What are they used for?
How are they constructed? (e.g. glass-sealed paper in oil)
Are they of value, and if so, to whom?
Am I correct that the labeling implies 2F and 25,000 volts?

My father recently passed away, and I would like to sell these two units. He has an array of incredible equipment and parts, much of which I'm keeping (we built a Tesla coil together, a bank of smaller caps used to vaporize thin copper wire....an old science project when I was in 8th grade, etc), but I'm having a hard time finding out more about these units.
My intuition is that they are intended for power/utility use, perhaps for reactive power compensation, but that's really outside my area of understanding.
Also, I am aware of how dangerous these units are - they are always stored with a short wire across the terminals.
Grateful for any insight from folks.


texts: 1-Wire DS18B20 on mighty 1284p can't find my sensors, same sensors work w/ Duemilanove

texts:
I have uploaded the DS18x20 Temperature example sketch (unaltered, except I tried multiple pins for the I2C communication) to my proven Duemilanove and my mighty 1284p.

On the Duemilanove my two DS18B20 temperature sensors are found and read correctly:

ROM = 28 36 6D 51 4 0 0 75
  Chip = DS18B20
  Data = 1 D6 1 4B 46 7F FF A 10 43  CRC=43
  Temperature = 29.37 Celsius, 84.87 Fahrenheit
ROM = 28 19 6 51 4 0 0 86
  Chip = DS18B20
  Data = 1 A7 1 4B 46 7F FF 9 10 E0  CRC=E0
  Temperature = 26.44 Celsius, 79.59 Fahrenheit
No more addresses.
(...)

Whereas the 1284p only says

No more addresses.

No more addresses.

(...)

I have not changed the wiring of the sensors; they are connected +5/GND, Data is pulled to +5V with a 2k7 and also to the reading pin, respectively. I have tested multiple pins for I2C communication - they all work on the Duemilanove, none work on the 1284p.

I am assuming some issues with I2C with mighty 1284p, but maybe someone else has another idea.

Here's the code (the unchanged example sketch, I have been taught to "include the used code, always!", so here it is):

#include <OneWire.h>

// OneWire DS18S20, DS18B20, DS1822 Temperature Example
//
// http://www.pjrc.com/teensy/td_libs_OneWire.html
//
// The DallasTemperature library can do all this work for you!
// http://milesburton.com/Dallas_Temperature_Control_Library

OneWire  ds(0);  // on pin 10

void setup(void) {
  Serial.begin(9600);
}

void loop(void) {
  byte i;
  byte present = 0;
  byte type_s;
  byte data[12];
  byte addr[8];
  float celsius, fahrenheit;

  if ( !ds.search(addr)) {
    Serial.println("No more addresses.");
    Serial.println();
    ds.reset_search();
    delay(250);
    return;
  }

  Serial.print("ROM =");
  for( i = 0; i < 8; i++) {
    Serial.write(' ');
    Serial.print(addr[i], HEX);
  }

  if (OneWire::crc8(addr, 7) != addr[7]) {
      Serial.println("CRC is not valid!");
      return;
  }
  Serial.println();

  // the first ROM byte indicates which chip
  switch (addr[0]) {
    case 0x10:
      Serial.println("  Chip = DS18S20");  // or old DS1820
      type_s = 1;
      break;
    case 0x28:
      Serial.println("  Chip = DS18B20");
      type_s = 0;
      break;
    case 0x22:
      Serial.println("  Chip = DS1822");
      type_s = 0;
      break;
    default:
      Serial.println("Device is not a DS18x20 family device.");
      return;
  }

  ds.reset();
  ds.select(addr);
  ds.write(0x44,1);         // start conversion, with parasite power on at the end

  delay(1000);     // maybe 750ms is enough, maybe not
  // we might do a ds.depower() here, but the reset will take care of it.

  present = ds.reset();
  ds.select(addr);
  ds.write(0xBE);         // Read Scratchpad

  Serial.print("  Data = ");
  Serial.print(present,HEX);
  Serial.print(" ");
  for ( i = 0; i < 9; i++) {           // we need 9 bytes
    data[i] = ds.read();
    Serial.print(data[i], HEX);
    Serial.print(" ");
  }
  Serial.print(" CRC=");
  Serial.print(OneWire::crc8(data, 8), HEX);
  Serial.println();

  // convert the data to actual temperature

  unsigned int raw = (data[1] << 8) | data[0];
  if (type_s) {
    raw = raw << 3; // 9 bit resolution default
    if (data[7] == 0x10) {
      // count remain gives full 12 bit resolution
      raw = (raw & 0xFFF0) + 12 - data[6];
    }
  } else {
    byte cfg = (data[4] & 0x60);
    if (cfg == 0x00) raw = raw << 3;  // 9 bit resolution, 93.75 ms
    else if (cfg == 0x20) raw = raw << 2; // 10 bit res, 187.5 ms
    else if (cfg == 0x40) raw = raw << 1; // 11 bit res, 375 ms
    // default is 12 bit resolution, 750 ms conversion time
  }
  celsius = (float)raw / 16.0;
  fahrenheit = celsius * 1.8 + 32.0;
  Serial.print("  Temperature = ");
  Serial.print(celsius);
  Serial.print(" Celsius, ");
  Serial.print(fahrenheit);
  Serial.println(" Fahrenheit");
}

Thank you.


texts: Would a high temperature heat resistant tape be able to insulate a heating wire (heated at maximum 80°C)

texts:
I want to build a quick cheap heating pad using a non-coated electric wire (such as Nichrome, or Kanthal).

Would a high temperature resistant electrical tape could work as an electric insulator? (It would prevent shortcircuits from moisture)

The tape (or any other material suggestion) must of course let the heat pass through.


texts: Using generic packages with protected type in Modelsim 10.xy

texts:
I am trying to use generic packages with a protected type in Modelsim 10.0a. The technote vhdl2008.note states:

  a basic generic package and its instantiation with some noteworthy
  restrictions:

  generic lists on package can contain constant generics and package
  generics
  the generic package can be instantiated as a design unit, but not in
  any local declarative region.
  Generics cannot depend on other generics in the same generic list

  It is reasonable to use this to instantiate the generic fixed and float
  packages from IEEE.  You can write your own generic package, instantiate it,
  and use it.  Just keep within the restrictions.

Now I have a generic package test_generic_pkg.vhd:

library ieee;
use ieee.std_logic_1164.all;

package test_generic_pkg is
    generic(
        WIDTH : natural := 16
    );

    type test_type is protected
        procedure set(d : std_logic_vector(WIDTH-1 downto 0));
        impure function get return std_logic_vector;
    end protected;
end package test_generic_pkg;

package body test_generic_pkg is
    type test_type is protected body
        variable data : std_logic_vector(WIDTH-1 downto 0);

        procedure set(d : std_logic_vector(WIDTH-1 downto 0)) is
        begin
            data := d;
        end procedure set;

        impure function get return std_logic_vector is
        begin
            return data;
        end function get;
    end protected body;
end package body test_generic_pkg;

An used by an entity/architecture tb.vhd:

package test_pkg is new work.test_generic_pkg generic map( WIDTH => 16 );

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

use work.test_pkg.all;

entity tb is
end entity tb;

architecture behavioural of tb is
    shared variable test : test_type;
    signal clk : std_logic := '0';
begin

    clk_gen: process is
    begin
        wait for 50 ns;
        clk <= not clk;
    end process;

    test1_p: process(clk) is
        variable cnt : unsigned(15 downto 0) := to_unsigned(0, 16);
    begin
        if rising_edge(clk) then
            test.set(std_logic_vector(cnt));
            cnt := cnt + 1;
        end if;
    end process;

    test2_p: process(clk) is
    begin
        if falling_edge(clk) then
            assert false report to_string(test.get) severity note;
        end if;
    end process;

end architecture behavioural;

This two files can be tested with the sim.do file:

vlib work
vcom -work work -2008 -novopt test_generic_pkg.vhd tb.vhd
vsim -novopt work.tb

When executing this do file Modelsim compiles both files and while loading the libraries for the simulation it fails with:

...
# Loading work.queue_pkg(body)
# Loading work.queue64
...
# ** INTERNAL ERROR: pkgref: export lookup failed for package #0
# Error loading design

I also tried to put the package instantiation in a separate file but the results stays the same. What is the solution to get generic packages with protected type working with Modelsim? Using generic packages works fine without a protected type and protected types in a normal package also.

P.S.: Modelsim 10.0a seems to not support this feature although it is not mentioned in the technote. What version of Modelsim added this feature?


texts: Why are USB power and ground connected at the same time?

texts: Building off this question, why are the USB power and ground lines connected at the same time?  Wouldn't it be better to connect ground first, then power, the way Serial ATA power cable does?


texts:
I've just got hold of a nice little PCB etching kit, which uses ferric chloride as the etchant. I know it's re-usable for at least a few etches (though the kit doesn't actually specify an estimated re-use count) but after that I'll need to dispose of the used chemical.

I've read the accompanying safety sheet thoroughly, which states that I should use add sodium carbonate to form ferric oxide, which can then be disposed of. It's not very clear about the details though.

It seems to indicate that a 1:1 mixture of Na2CO3 and FeCl3 should be achieved, but (from what I can tell) the Na2CO3 is usually sold as a powder. How do I measure a 1:1 mixture between the two?

As a side question, I see a lot of people here using boiling water with their ferric chloride etchant, but the instructions for this kit state 21°C - 24°C is the optimal temperature. Are they just trying to cover their asses in case someone gets boiling hot corrosive liquid on themselves, or am I missing something?


texts:
I read flash device ID as following:

Manufacturer: c8
Device: 4013

Is this enough information in order to uniquely identify the IC?
Is there some web repository where I can check which device I have in hand, based on that ID?

Update:

Thanks to @RespawnedFluff answer below I found out this list.

Is there some standard way to identify IC by Manufacturer/Device ID?
Otherwise, how do manufacturers prevent ID collisions (same ID to different devices) when they allocate these IDs?


texts: How to synchronize TI high precision ADC and DAC via SPI?

texts:
I am working with DAC80504EVM and ADS8920BEVM-PKD from TI. I am trying to design a system which uses TMDSEVM6657EVM processor board to communicate with these converters via SPI.

However, I am trying to figure out how to synchronize the converters and I would really appreciate any suggestion or direction in research.

Here are the datasheets:

ADS8920B ADC - ADS8920BEVM-PKD
DAC80504EVM
TMS320C6657 DSP home page

Edit:
I am building a system for 3D ultrasonic distance measurement. Three outputs of DAC would drive three transducers, which then transmit three signals. These signals would be received via hydrophone, which then sends signals to ADC. I want to transmit the signals, receive them and process in DSP. I would like to do matched filtering in order to compute time of arrival for every transmitted signal. That is why I am trying to figure out how to synchronize transmission and reception.


texts: Via in between differential traces - how bad is it?

texts:
I'm working on a board that has some LVDS 2.5 signals.  All the guides I've read about board layout say not to put vias in between the differential traces, eg this guide

In a few cases it would be a lot easier to route the differential pairs out like this:

Looking at B5 and B6, they go around a power pad (with a via right next to it) and then continue together.  I'd want to do that with a few ground pads also.

If I don't do that, I'll need either 3 mil trace and space instead of 5 mil, or a 6 layer board instead of 4 layer.  Ouch.

So the question is, how bad is this really?  Should I expect 10 mV coupled into the LVDS lines, or 100 mV?

The BGA is 1.0mm pitch, the traces are 7.7 mil spaced 5 mil apart for 100 ohm differential (but probably 5/5 while escaping the BGA). The top layer is signal, then ground 0.23 mm below that, then power.  The BGA is an Artix-7 XC7A15T.

UPDATE The LVDS signals are clocked at 600MHz DDR.

UPDATE I'm more worried about current spikes on the power/ground coupling into the LVDS lines in different directions on each line, ie driving one line higher and the other lower, enough to cause the receiver to read the wrong (or indeterminate) value.  Not so much about impedance discontinuity or reflections.  But I really don't know... that's just intuition.


texts: Choosing between relays and MOSFET driving multiple loads

texts:
I am working on a project, which may eventually be used commercially, so I want to ensure that it is safe.

It has a 80Amp 12v power supply. It is controlled by a touch screen, with switches to control different systems.

It needs to control 4 separate LED panels, each of which draw 7.2 Amps.
It needs to control 6 linear actuators.
4 of the actuators can be tied together, and draw 5 Amps each.
2 of the actuators can be tied together, and draw 4 amps each.

LED Zone 1-4:    4 @ 7.2A each, 28.8A total

Actuator Zone 1: 4 @ 5A each,   20A total

Actuator Zone 2: 2 @ 4A each,   8A  total

Total: 56.8A

For this project, I see two main options, component wise. I could either use SSRs, or MOSFETs to drive the LEDs/actuators.

I also could have a separate MOSFET/SSR to drive the 6 actuators, and tie them together in software, or, two MOSFETs/SSRs to drive the two groups together.

Which approach would you recommend, and why?

Also, since this is my first time with this high of current loads, i'm not sure on fuses. Should each bank of MOSFETs/SSRs have its own fuse?


texts: Micro controller programming with bluetooth dongle

texts:
I have this USB bluetooth dongle . I want to know is it posible to active this dongle with PIC 16F628a micro controller and communicate with PC. I know this micro controller support serial communication, but I don't know is this application is posible.

Thanks.


texts:
I am trying to build a coil gun that will pull a magnet half through the coil, then reverse the current and repel the magnet out the rest of the way.
I want to use 4 transistors as 2 sets of 2 to control the current. When one set is on it will cause the battery to flow current through the coil in a direction, then when that set is turned off and the other set is turned on current will flow in the opposite direction. Using the coil connected to the current sensor I will determine when to switch between sets. The arduino will supply voltage to the base of the transistors using up to 5V. I want to know if this circuit is actually able to work how I want it to. I have tested the circuit using BJTs because that was what I had at the time (also because I misread a datasheet and thought they were NMOS), but that was me just assuming that I could apply a voltage to the base and it would work.

As for the transistors I planned on using NMOS mainly because that was what I was learning about at the time, but i'm not sure if they are the best choice anymore. If it is possible for the circuit to work what type of transistor would be best? I'm currently learning about MOSFETs and BJTs so I am still new to them.
*EDIT : Schematic has been changed to show correct symbols...I think. Also Va is the voltage to one set and Vb to the other set.


texts: How to find cutoff frequency with more than one resistor

texts:
I have the above circuit and I want to find the cutoff frequency. Z_eff,in is my load. I have created a transfer function:

How is it possible to find the cutoff frequency? Let me know if more information is needed.


texts: Why is a MOSFET in series with a power rail, with the gate connected to ground?

texts:
I am a novice studying a circuit board I did not design, to better understand how electronics work. Here is an image of the main power for the entire board:

The +12V and +24V in the P1 box are each connected to a Mean Well power supply.

I understand that the 100uF capacitors are there to source current for the quickly switching ICs on the board. I cannot understand why this MOSFET is here, in series with the 12V rail, with its gate connected to ground. From the little I've learned about power MOSFETs, I expect that the Drain and Source should be connected with a small resistance. I expect that because the Gate-Source voltage is -12V, plenty to turn on the MOSFET.

Why is this MOSFET here? Is it something to do with the body diode in the MOSFET, maybe to prevent reverse current? If this is the case, would you use the MOSFET instead of a different type of diode because of its low resistance?

Thanks very much for all answers!


texts:
I'm creating a board which takes an external power source to drive motors which are controlled by a ULN2003A connected to the Raspberry Pi GPIO.

It would be nice if when the external power source is connected it could provide power to the Raspberry Pi itself through the 5V GPIO pin.

I appreciate this would require a voltage regulator, a polyfuse (to replace the one I'm bypassing that would normally protect the Micro B USB power input) and an ultrafast rectifier for reverse polarity protection.

My question is whether or not it is possible to detect that the Pi is already powered through USB and therefore block the back powering feature (to avoid having two sources connected).

Ideally if the user were to yank the Micro B USB cable the back powering would just kick in and take over. And likewise if the Micro B USB cable we re-inserted to disable it again. I don't really see how that could be possible so maybe it isn't!


texts: How does this circuit read 4-20mA current loop input through Op-amps?

texts:
I am a software guy working on coding a control system on a board whose hardware designers are all gone. While i have got everything else working, there is one piece (a 4-20 mA current loop input) which i am not clear enough to start coding for. Attached is the picture.

J12 (pin 2 is not used) is the input from potentiometer. I have this working by reading P1.3 in my code (0-3 V mapped to 0-1023 range via 10-bit ADC). However i don't understand the circuit from J11. Am I supposed to read P1.0? What is the voltage range to which the 4-20 mA is mapped to? I need to know this since i can then configure my MCU (a Silabs c8051F850) appropriately for the 10-bit ADC.

Edit 30/6/17: Multisim simulation of relevant circuit (pointed out by @jonk) below


texts: What kind of oscillator is used for CMOS CPU clocks?

texts: Do they usually have a mono/bi-stable multivibrator that is activated a schmidt trigger when the computer is powered up? Or do they use ring oscillators? Or perhaps crystal oscillators.


texts:
Is it possible to control the output torque of a brushed DC motor using PWM?

From my understanding the speed is directly proportional to voltage applied and torque is proportional to current drawn. So if the load of the motor increases it will just simply draw more current (if the load is within its torque limit). Since I do not have any current controller in my motor driver board there is no way I can control the output torque of the motor. How can I solve this problem? I read that a hardware feedback loop using an operational amplifier can be used to keep the current proportional to the reference voltage. Is this correct? And is it possible to make such a circuit for a 90W, 24V DC motor?


texts: If I have a small signal, does routing it through vias to different layer introduce any significant noise on the signal compared to routing it within same layer without any vias? Considering all other parameters like track length, width constant.


texts: "Voltage source is shorted" simulation error

texts:
Take a look at the image below,

Why is that bottom voltage source is shorted? (http://everycircuit.com/app/) give me the response as voltage source is shorted, why is that?

As far as I know, If an element is shorted , two terminals of that particular element should be in  the same node, but here it does in different nodes, then how it can be a shorted one?

This is a screen-shot what (http://everycircuit.com/app/) says


texts:
My current electronics project is to build a very simple customizable "phone". It is my own idea, with as ultimate goal to learn about microcontrollers and basic electronics.

This is my set-up so far

I managed to interface with the microcontroller, and the voltage transformation circuit seems to works (how do you call this?). The issue is with the Neoway M590 GSM modem. It reboots every couple of seconds. I think this is because the modem draws a peak current when trying to connect to the network a few seconds after starts-up, and automatically shuts down because the voltage drops too low for safe operation. This is why we need the big capacitor there (1000 uF). I power the board with a PSU that can supply more than enough amperage. Communication is via a USB-TTL converter which I connect to a computer.

Please note that in my set-up I have completely eliminated all dependence on the microcontroller and voltage transformation circuit, in an effort to isolate the problem.

The Neoway M590 came with a pre-designed PCB

I have soldered one of these PCBs with a Neoway M590 and had no modem restart issues (after I put in a heavier capacitor).


texts:
I was going through a Verilog code, and came across this:
assign a= (b==c);

Can someone tell me what it does?


texts: Right power supply for DC motor with load

texts:
I am trying to turn a disc of 10" of 20kg with a DC motor. I would like to get at least 1200 RPM. The motor is an Ampflow A28-400 and the power supply I am using is an adjustable power supply by Versatile Power called BENCH 30-33 XR.

Although the power supply is rated at 600W, up to 30V and 33A, the V caps off at around 3V at 33A. Can anyone explain to me what this is happening? What is the correlation between the power supply and the load which I am trying to turn?
The RPM at 3V and 33A is near or below 150 RPM.


texts: How do you calculate the VA value of a relay?

texts:
For my capstone project I am building an outlet which can be controlled using WiFi signals.

I am having trouble finding a suitable relay for this device. The relay I first used was a latching relay (399-11009-1-ND).. but it only had a maximum switching power of 125 VA. I am unsure of how this VA value was determined at the maximum switching current is 2A and the maximum switching voltage is 220 VAC. By multiplying the two I expected a value of 440 VA. Why is the VA value 125 VA instead of 440 VA?

https://www.digikey.com/product-detail/en/kemet/EE2-3SNU-L/399-11009-1-ND/4506461


texts:
I read this on another site:
 "In a properly designed circuit, if a fault were to occur on the 120-volt outlet between the hot-wire and the ground, the current will flow through ground wire back to the main panel, where it will move to the neutral wire via the neutral-to-ground bond, up to the utility transformer, back down the hot wire to the circuit breaker, tripping the breaker."

So now I'm thinking why have a ground rod at all if it goes to the neutral wire at the panel and not the ground rod.

This question is not specific to a fault condition. If the neutral and ground are tied together at the panel what prevents current from the neutral wire flowing to earth through the ground rod?


texts: Internal thermal limit of LF00 voltage regulators

texts:
Reading the datesheet of the LF00 voltage regulator series leads to a basic question to myself.

The basic facts at the beginning of the sheet telling me, there is a logic with an

  INTERNAL CURRENT AND THERMAL LIMIT

inside the component. I was very interested in this thermal limit and tried to find out the concrete behaviour of this function. Unfortunately I found only a two relevant information of some temperature behaviour in the whole datasheet.

Operating Junction Temperature Range -40 to 125 °C

None of them helping me to understand the thermal limit of the voltage regulator. I also expected a strong surge of the voltage dropout at higher temperatures - but figure 2 is telling a different story.

So how is this thermal limit defined and how is the expected behaviour? Am I allowed to use the component without any heatsink and without need to worry about overheating (If a accept a shutdown at overheating of the regulator)?


texts: MAX471 current sensor minimum current measurement

texts:
I'm trying to use a MAX471 module (no brand) with arduino (5V) following this tutorial.

I measure the current with my multimeter of a motor with a 200Ω resistor and i get ~14.84mA. The sensor displays ~13.8mA and some times it drops to ~8.6mA

I power the motor with Arduino as power supply via the module.

When I connect instead of a motor a LED via a 1k resistor, i get 2.80mA in the multimeter the sensor displays 0. Does it have a minimum range and can this be fixed so to get current sensing for low current?


texts: How tight can I mount a TO-220 to a bus bar?

texts:
I'm building a small switching circuit consisting of 8 MOSFETs (bi-directional blocking, 4 in each direction), which should switch 100-200A at about 1kHz.

I've concluded that since PCB with a thick copper layer isn't readily available, a much better solution is simply mounting the MOSFETs directly on a bus bar, to which the power cables are also mounted.
Thus, I only need to solder the Source-pin between the MOSFETs (in open air).
This solves several problems: good thermal dissipation, low voltage drop from cable to MOSFET and easy mounting/replacement of all components with very little soldering.

My question is: how tight should I tighten the TO-220 package to the bus bar? Am I correct to assume that all the electronics are within the black plastic part, and that I can therefore tighten it as hard as I would like? Are there any potential problems, e.g. heat-warping causing poor connection etc?

Here's my schematic for the curious:

simulate this circuit – Schematic created using CircuitLab

Edit: Added link to MOSFET datasheet. Datasheet from manufacturer showing package details, but not showing D connected to tab.


texts:
I'm interested in increasing the transmission rate over Cat5 for a personal project. (Cat5/5e/6 will be chosen because of it's properties and obtainability but will not be used in the standard way)

In any case what I'm interested in using a "multi-level bits" per clock of transmission. Digital communication almost always uses a single bit per clock.

For example, using a single bit(0 or V) in cat5 at 100MHz allows only for a 100Mbits data rate. Using 4 bits allows for and effective rate of 400Mbits/TP(or over Cat6a, 2GB/TP). For my project this is significant.

Obviously adding more bits per clock increases complexity and decreases the noise immunity but I feel that it could be done with a few logic gates and will work for my particular application.

Since the signals will be differential it seems it may be pretty easy on the tx side by actually not having one of the lines being the mirror images but independent. Noise immunity will still be retained due to the differential nature.

Essentially on each end of the line we will have 4-bit DAC(for tx) and ADC(for rx) to convert to and from the multi-level representation.

My question is, besides the added cost and complexity(which doesn't seem to be all that great?), are there any other reasons why it is bad.

I conclude that there seems to be no loss of noise immunity:

Asymmetric differential signaling is used. External noise will be canceled out in exactly the same manner when symmetric different signaling is used(assuming that the noise does not depend on the voltage in the wire)
The noise margins can be kept the same by simply amplifying and attenuating the signal before and after transmission. e.g., normally 0-3.3v are used. We can amplify this to 0-26.4V which will give the same distance between each level(3.3V). Of course, the cost is 8 times the transmission power but this would probably be similar to when using a single-bit/clock rate that is 8 times larger.

Therefor, best I can decern, the real cost in achieving around an order of magnitude in throughput is a few dollars in parts. (a monolithic tx and rx ic would reduce the complexity to near 0).

Is there any real downside besides what I have listed. Basically what are the practical drawbacks?


texts: Identify this [Molex Minifit Jr] low voltage electrical connector for lighting

texts:
On the other end of the wires from this connector is a MR16/GU5.3 Socket with Retaining Clips for a bulb.

My clips need to be replaced so I am looking to replace the entire part with both connectors. But, I cannot identify this clip plug. The male components are exactly 9mm long.


texts:
I need help with connecting this module with USB cable or serial cable. What do I need to connect? What channels?

EDIT:

Okay guys I see that you think that this gps in not so good. How about this one? I just need a gps module to connect it to my pc. I have tried searching a gps module with usb but I have found nothing because with usb port we are not talking about module anymore only about gps unit which I don't need.

What about this gps module and this cable?

I really just want to make gps for vehicle tracking. So I need module and I will make car-pc. Don't worry about program. I am programmer so that's not problem. But connecting all those ports get me confused.


texts: How to write a big text on Eagle schematic?

texts:
When you choose a text from the tools bar, and put it somewhere, it will create a text that appears on the pcb.

I would like to create a text just to mark things on the schematics only, and I want it big and clear.

How do you add a big text to mark things on the schematics ?
How do you add a shape, for instance a square, to mark things on the schematic, not pcb ?


texts:
Originally I wanted to setup a simple curve trace circuit to measure the characteristics of a BJT I salvaged. This circuit operates by measuring the voltage and current through the transistor for different applied voltages on the base and collector. For this, I found a simple tutorial which uses the same USB oscilloscope that I have (https://www.instructables.com/id/Semiconductor-Curve-Tracer-With-the-Analog-Discove/). The hitch arose when trying to implement the circuit on the breadboard; I found that their circuit measures the differential voltage across the collector resistor to determine the current. This wouldn't have been a problem for me until I (rather permanently) connected a BNC probe adapter to my USB oscope, which ties the negative inputs of all BNC probes together. So as a simple remedy I figured I could just build a differential to single-ended converter to avoid the issue of ground loops in my probes.

For even more background, I did a quick google search on the terms 'differential to single-ended converter' and it gave me this article as a top result (https://www.analog.com/en/analog-dialogue/raqs/raq-issue-145.html). In my haste to get to my primary project, I threw this circuit together on a breadboard.

My results were decently accurate for differential signals, but I found the common-mode signals weren't completely attenuated.

Great, so I guess this has something to do with the non-idealities of the opamps. Then I got to thinking back on what I know about circuits, and I realized that an OPAMP is essentially a differential to single-ended converter itself. I quickly found a 'differential amplifier' circuit that would essentially achieve the same thing with only one opamp (https://www.electronicshub.org/differential-amplifier/).

So my question (finally) is, what advantages does the dual opamp circuit offer versus the single opamp solution? Furthermore, would either one be better for simple (near-DC) current measurement? Thanks in advance


texts:
I am trying to drive a Linear Actuator (stepper motor with a lead screw) to drive until a force of 15 pounds is reached then stop.  I am having trouble finding a good method to do this (I am new to stepper motors) can anyone point me in the right direction?

I am thinking of getting the motor with an encoder and adjusting a voltage/current until it will stall at 15 pounds and detecting that it did not move using the encoder then stopping the motor, is this a good way to go about this?


texts: Turning on electric devices by plugging them in rather than pressing their on/off button

texts:
Weird question, I hope it has its place here: is it true that electric devices like washing machines, computer and so on, should be (1) plugged in, and then (2) turned on, rather than the contrary?

In other words, is it OK to have an electric device on, and then you plug it in the wall plug so it starts, or should you first plug it on and then turn it on?


texts: Control multiple Schmitt Trigger oscillators from a single current sink

texts:
I'm playing with an idea for a VCO (Voltage Controlled Oscillator), and would like to make something a bit out of the ordinary. My idea is to run multiple sawtooth oscillators from a single control voltage, with the possibility of de-tuning the frequency of each individual Oscillator core to some degree.
I was hoping to make this quite simple, and was thinking of using a 40106 Hex Inverting Schmitt trigger for the oscillator cores, and a Voltage controlled Current Sink as the control for this (oscillator schematic in picture, where the sawtooth waveform is taken from the Schmidt trigger input).

Making a single such oscillator was not hard. However, once I want to combine 2 or more of these cores, I cannot figure out a reasonably simple way to share the current sink between them. As I would like to be able to slightly tune their individual frequency, just connecting them directly causes them to sync up to the fastest one.
I could of course create one Current Sink for each, but the circuit for this is quite complex and also temperature dependent. So it would be a lot simpler if I could share one sink for all cores.
Does anyone have any good suggestions? I am aware that this may be trivial (or impossible), but I am sadly not that fluent in electronics (especially analog circuits).


texts: add run capacitor to capacitor start motor to increase efficiency

texts: Can I add a run capacitor to a capacitor start motor to increase its efficiency? I remember doing this 20 years ago and the run current dropped 20% or so, but I didn't measure the power consumed. The motor was quieter and cooler. The run cap value was 0.1 x start cap value, connected across the start cap and start switch. This is an offgrid water pump application.


texts: I would like to universal stepper motor driver circuit. Is it possible for one circuit to be able to drive unipolar and bipolar motors with only a firmware change or do they require much different circuits? I know that bipolar motors use 4 wires and unipolar uses 6 so if i use a connector with 6 pins would it be possible?


texts:
I am trying to make a circuit using a 3V3 Arduino and other modules working on 3V3, but I have a problem with an analog water sensor I need to use. The output is a voltage range is from 0.5V to 4.5V.

I think I cannot use 4.5V signal on an analog pin of an Arduino working at 3V3.

So I have a basic idea like solution.
- Use a 5V step-up voltage regulator from 3V7 li-on battery for the water sensor
- Then using a voltage resistor divider to convert from 5V (sensor output) to 3V3.
- Then connect to the Arduino and inside make line code with a simple equation where I can recover the 5Volt value.

For example

Will I will lose resolution doing this? Is it a bad idea?

EXTRA QUESTION

To ensure that I will not lose resolution, what do I need to check? Maybe the minimum step voltage in the ouput of sensor? For example 5mv minimum of variation, then 5mv*voltage_divider = 3.3mv ... Then 10 bit of resolution of ADC in Arduino is enough? I got a 3.22mv resolution (3.3/1023)


texts: Why can't generators with different frequencies supply the same transmission line?

texts:
I am thinking of the issue that

  the TEPCO electric transmission
  networks cannot be taken over by other
  electric companies because of
  frequency difference.

TEPCO is the electric company having the nuclear crisis.

Why cannot generators having different frequencies supply in the same transmission line?

Edit

I think most electric equipments can work at either 50 OR 60 Hz. So what is the problem?


texts:
A flip flop is a sequential circuit and it stores a 1-bit value,
but it is designed using only basic, universal gates and a feedback circuit. How then is it able to store or handle a 1-bit value?

I thought that it is due to clock usage but I don't know the exact reason.
Is my assumption is correct or not?


texts: Protecting PCBs from ESD charges outdoor

texts:
I have ESD charge vulnerable PCBs and I am going to use them to make some tests outdoor. I am thinking of a way to protect them while doing the test since they are going to be touched by hand and maybe laid on floor or conducting surfaces. Because that the test is outdoor there is no way for me to use ESD wrist strap and be connected to ground.

For the time being I am not able to afford buying plastic boxes for protection. I have got an idea to make a box from cardboard and put a flipped aluminum foil inside of it (like the anti-static bags). I do not know how much effective the cardboard box is but it should work to some extent.

What are the disadvantages of this way? Are there any other ideas to protect the PCBs?

EDIT:

The PCBs are for wireless communication and each one has a 6.5 cm whip antenna. Each PCB is powered by a 12V battery.


texts: In a two input diode AND gate, when both inputs are low, both diodes conduct and pull the output down to a low voltage. How can the electrons flow to the input of the AND gate, when the input is connected to the - side of the battery?


texts:
I am wondering what is the criteria for selecting diodes TVS, for example my circuit runs at 36V and I want protect my circuit from spikes

But I am little confused about the Breakdown Voltage (VBR) if it select a value just a little above 36V and Reverse Stand-off Voltage (VRWM) at 36V.

My confusion in regarding to the Clamping voltage (Vc) because I see some graphs and the clamping is actually at Clamping voltage (sounds logic), but why is used the VBR widely instead of Vc?

for example: :http://www.protekdevices.com/xyz/documents/kb/tech/ta1004.pdf VBR = 6V, but it is clamping at 10V+

the actual max voltage input possible for my circuit is 38V, but the parts for 36V actually says clamping voltage 56V+ :/

for example this :https://www.digikey.com/product-detail/en/littelfuse-inc/SMAJ36A/SMAJ36ALFTR-ND/762298

Voltage - Reverse Standoff (Typ)    =36V
Voltage - Breakdown (Min)   =40V
Voltage - Clamping (Max) @ Ipp  =58.1V

my power requeriments are in wide range from 12V to 36V max:

36V/900mA Max or 12V/2.6A


texts: I have designed a Mealy FSM, that performs Divide by 5 operation on a binary number. How to implement control signal state for bitstream?

texts:
The FSM shown by both the table and state diagram perform Division by 5 on a binary input A. The individual states represent the remainders and the transition outputs are meant to be loaded into external shift register.

The FSM below takes an input stream of bits that are separated into chunks by a control signal c. When c goes from 0 to 1 it indicates MSBs and when it goes from 1 to 0 indicates LSBs, the FSM must remember this active high state where c=1 until control signal is set to c=0. How can I correctly implement a sixth state to my FSM that performs this control mechanism. I know that c needs to be an input to my fsm in addition to a0 and a1 bits(see problem statement below)

Edit: I added a few redundant statements here, but really all the information is already provided below. Please add helpful comments indicating what info is missing that would help you understand this question more.
]1


texts:
This is the circuit I'm given:

I'm using the Branch Current Method to determine the currents. Firstly I'm choosing the directions of the currents and the way I'm going to sum the voltages with the KVL:

Then I follow the algorithm from my textbook(it's not in English so probably it's worthless to mention it)
 1. Let the number of nodes be n, create n-1 equations from KCL. Here are the equations I made:
$$I_2 + I_5 = I_1$$
$$I_2 + I_6 = I_3$$
$$I_4 + I_3 = I_1$$
 2. Let m be the number of branches in the circuit. Create m-n+1 equations from KVL, here are the equations I made:
 $$I_1R_1+I_5R_5+I_4R_4=V_1$$
 $$I_6R_6+I_3R_3-I_4R_4=V_2$$
 $$I_2R_2-I_5R_5-I_6R_6=V_2$$
3. Solve the system. The whole system looks like this:
$$I_2 + I_5 = I_1$$
$$I_2 + I_6 = I_3$$
$$I_4 + I_3 = I_1$$
$$I_1R_1+I_5R_5+I_4R_4=V_1$$
$$I_6R_6+I_3R_3-I_4R_4=V_2$$
$$I_2R_2-I_5R_5-I_6R_6=V_2$$

When I replace the variables with value, I get following system. NOTE i'm replacing I's with X's because Wolframalpha thinks that I'm working with complex numbers or something.
$$x2+x5=x1$$
$$x2+x5=x3$$
$$x4+x3=x1$$
$$60*x1+116*x5+110*x4=82$$
$$94*x6+36*x3-110*x4 =56$$
$$78*x2-94*x6-116*x5=56$$

However when I plug this into Wolframalpha, I get results, which don't match with the ones I get from the simulation in PSpice.
WolframAlpha results:

x1 = 7225/6216, x2 = 821/777, x3 = 7225/6216, x4 = 0, x5 = 219/2072, x6 = 7333/48692

Results from simulation:

I'm failing to find my mistake. Any help is appreciated


texts: What is the difference between a DSP and a standard microcontroller?

texts:
I understand that a DSP is optimized for digital signal processing, but I'm not sure how that impacts to the task of choosing an IC.  Almost everything I do with a microcontroller involves the processing of digital signals!

For example, let's compare the popular Microchip dsPIC30 or 33 DSP  and their other 16-bit offering, the PIC24 general purpose microcontroller.  The dsPIC and the PIC can be configured to have the same memory and speed, they have similar peripherial sets, similar A/D capability, pin counts, current draw, etc.  The only major difference that appears on Digikey's listing is the location of the oscillator.  I can't tell the difference by looking at the prices (or any other field, for that matter.)

If I want to work with a couple of external sensors using various protocols (I2C, SPI, etc.), do some A/D conversions, store some data on some serial flash,  respond to some buttons, and push data out to a character LCD and over an FT232 (a fairly generic embedded system), which chip should I use?  It doesn't appear that the DSP will lag behind the PIC in any way, and it offers this mysterious "DSP Engine."  My code always does math, and once in a while I need floating point or fractional numbers, but I don't know if I'll benefit from using a DSP.

A more general comparison between another vendor's DSPs and microcontrollers would be equally useful; I'm just using these as a starting point for discussion.


texts: I'd like to know what is the difference between RAM ( data memory ) and the stack memory in PIC micro controllers if both of them is volatile( not sure about stack ) and the stack is temporary memory?


texts:
I am using one of the IC in my project and it needs -0.55V with maximum of 220mA. I will appreciate your recommendation for this solution,since i search a lot but unable to find any valid solution for this negative voltage.

How do I get a negative voltage of 0.55V that can source at least 220mA?


texts:
When programming hundreds of thousands (or more) MCUs or EEPROMs, it seems that companies need to add unique serial numbers to each programmed unit -- don't want two units with the same serial number.

How is this done in practice, especially for MCUs with internal FLASH?


texts:
What the title says. I'm curious how exactly a digital potentiometer works. Is it something like a pair of pass transistors like below?

simulate this circuit – Schematic created using CircuitLab

Or is it more like a series of switched resistors like below?

simulate this circuit

Or is it something else entirely, that I can't think of?

I looked around, and found exactly one source suggesting that it is the latter case, but I couldn't find anything else talking about the internals of a digital pot at all. Maybe there's more out there, though, and I'm just really bad at finding things.


texts:
I'm working on my own SLA charger that has MCU onboard, can regulate switching DC/DC converter to charge 12V battery in 3 stages and can do temperature correction.

Everything is fine except that I want to improve on battery voltage measurement.

Currently, I use simple voltage divider to reduce battery voltage range into MCU's ADC range of 0-1.8V. The thing is I don't care of battery voltage (let's say) less than 10V because that is a bad battery and I don't want to charge it at all. I would like to map 10-16V into 0-1.8V instead of 0-16V into 0-1.8V so ADC measurement could be done more precise:

What can be used to archive such mapping (price does not matter)?


texts:
A specific type of bit-level manipulation consists in setting or clearing one single bit in a multi-bit value, given its index and its new value. This operation can be implemented in hardware by a BitSet circuit with the following interface:

Input x is a 4-bit value representing the original value.
Output y is a 4-bit value representing the modified value, after the bit-set
operation.
Input index is a 2-bit value, ranging from 0 to 3, indicating the index of the bit to modify.
Input value is a 1-bit value set to 0 or 1, indicating the value that bit index should take in output y. Every other bit in y should match the corresponding bit in x.

Here's the code I have which I took from examples in class:

module BitSet(input [3:0]x,
         input [1:0]index,
         input value,
         output [3:0]y);
   always@(x,index,value);
   begin
      if (index = 2'b00)
        y[0] = value;
     if(index = 2'b01)
        y[1]=value;
     if(index = 2'b10)
        y[2]=value;
     if(index=2'b11)
        y[3]=value;
   end
 endmodule

and here's the testbench:

module BitSet_tb();
    reg [3:0]x;
    reg [1:0]index;
    reg value;
    wire [3:0]y;

    BitSet uut(
      .x(x),
      .index(index),
      .value(value),
      .y(y)
    );

    initial begin
        $monitor ("%d %b %b %b %b", $time, x, index, value, y);
           x=4'b0000;
           index=2'b00;
           value=1'b0;
       #10 x=4'b0001;
           index=2'b01;
           value=1'b0;
       #10 x=4'b1111;
           index=2'b10;
           value=1'b0;
       #10 x=4'b1111;
           index=2'b11;
           value=1'b0;
       #10 $finish;
     end
 endmodule

When compiling, I get the following errors:

bitset.v:10: syntax error
bitset.v:12: error: invalid module item.
bitset.v:13: syntax error
bitset.v:14: error: invalid module item.
bitset.v:15: syntax error
bitset.v:16: error: invalid module item.
bitset.v:17: syntax error
bitset.v:18: error: invalid module item.
bitset.v:19: syntax error


texts: Is a fully differential opamp subtractor possible?

texts:
I know how to subtract two single-ended voltages with an opamp configured as a subtractor.
I'm learning about fully differential signal processing and I'm wondering if it is possible to subtract two balanced fully differential signals without converting them to single-ended first.
Say I have two analog signals.
V1_D = V1_P - V1_N
V2_D = V2_P - V2_N
What I want is V3_D = V1_D - V2_D
By algebra this is V3_D = (V1_P - V1_N) - (V2_P - V2_N)
So, it looks like I could do it with three subtractor opamps. But would I run into a dynamic range problem?
Imagine I have a 5V VDD and my signals are rail to rail. So, V1_P - V1_N could be anywhere between 5 and 0. It doesn't seem to work unless I also scale the voltages down by 2. (which may be OK).
Is there an easier solution I'm missing here?
Thank you for your time.


texts:
I have a old PCB board and there are some connectors on it that I would like to use again.

Is there any possible method to remove the connector with plastic parts (say molex 53398-0271) without melting it? The PCB could be destroyed, but would like to save the connector.

The temperature rating for the connector is -40° to +85°C, for molex 53398-0271. So I guess hot air gun would simply melt the connector.

It may be best and most simple to buy a new connector. Just curious if the is possible as it might be handy at times when you just ran out of parts.


texts:
So I am given

u(t)=325sin(314t+90°)V

i(t)=14.14sin(314t+30°)A

I have to find the impedance Z∠θ, value for the resistor and inductor, inductive reactance

Urms∠θ = 325/sqrt2 ∠90°

Irms∠θ = 14.14/sqrt2 ∠30°

Z∠θ = Urms∠θ / Irms∠θ =22.98∠60°

Irms=I

Irms= Urms/R

1/R= Irms/Urms = 707/16250

R= 22.98Ω but that cant be right since Z=sqrt(R^2+XL^2) and that would mean XL is 0
XL=ωL=314L=...

L= XL/ω = XL/314...


texts: AC-bias in tape heads: could someone explain?

texts:
I understand that the purpose of AC-bias is to improve the quality of a tape recording by countering some otherwise adverse physical properties of practical magnetic materials.

I've had this explained to me in a number of different ways, often contradictory, always vague. Online sources like Wikipedia don't help because they're more muddled and vague than most!

Could someone who is eloquent and knowledgeable give the definitive answer as to the physical processes which are involved and how AC bias helps? Actual equations preferred to hokey analogies.


texts:
I'm working on a project that requires an pulse voltage with a frequency of 50 Hz and a duty cycle of 5 to 10%. How can I make that with analog circuits? I've a DC voltage input from 0 to 5 volts and the output has to give a pulse that varies between 1ms and 2ms

My work:

I've made a Relaxation Oscillator, to get the sawtooth voltage across the capacitor. But how do I proceed?


texts: Data bus between uC and SRAM: what happens when both are writing concurrently?

texts:
My understanding of interfacing a standard SRAM chip is the following: When the host wants to write, the OutputEnable# is driven high to bring the SRAM data bus to High-Z and the host is driving the bus. When reading, OutputEnable# is low and the SRAM is driving the bus.

What happens if I accidentially enable the output of the SRAM while driving the outputs on the host side at the same time? Will there be physical damage?


texts:
I'm trying to build a model rocket launcher circuit. So far I have
this

The igniter requires 12V and 3A, BAT1 is 12.6V 9800mAh.

The arduino input pin should read HIGH when the igniter is connected and LOW when it isn't provided that SW2 is closed.

The when the arduino output is HIGH, the FET should trigger and the igniter should ignite provided that both SW1 and SW2 are closed.

Various Datasheets (they're not links because I don't have enough rep):

M1: FQP30N06L 60V Logic N-Channel MOSFET
D1: 10A05 10 Ampere Rectifier
D4: 1n4148 Small Signal Diode
C1: No datasheet, 50V 100µF

Could someone please look over this schematic and make sure everything works? And additionally, I want to replace SW1 with an illuminated toggle switch that has 3 pins, POWER, ACC, and GND. Could someone please edit the schematic to use that LED toggle as I don't know how to wire it. I was told this might work but they weren't sure:

Additionally, this circuit can be simulated at this link (Falstad).


texts: Sensing AC high voltage to microcontroller

texts:
I'd like to sense if I have AC 220V 50HZ available, and convert it to some logical level.

I made such circuit, will it work?

I use C1 as a resistor.

Any recommendations what can be improved?

UPDATE:

Thanks for the great help.

I choose Russel's answer because he was first and the note about 1N4001 was very useful,
calculations show that D1 will be stressed to up to 70 volts while C1 charging, so Turpie head will be kept in place.
I will hold 4001 for lower voltage applications.

Olin's answer was like the same C: Olin 0.1 uF, Rusl 0.068 (or 0.05). Rseries Olin 1k. Russell 10k, but also helped me alot.

Here is the updated circuit with simulation.

As keen beginner sorry for noobish questions. I will add more details with datasheets next time.


texts: I have a IPhone wall charger. Can I plug my netduino into it to power it via USB?


texts: How to measure three resistors in a triangle

texts:
I have three unknown resistors arranged in a triangle (a delta) and need to determine one of them, which is on the order of 100x larger than the other two, in a measurement circuit. I'm wondering if there is a known best way to go about this practically.

Here's what I'm thinking. A brute-force way would be to set up a voltage divider to measure between every pair of nodes, one at a time, then solve the obvious system of equations. That's three separate measurement cycles and not so great precision. I don't think it's possible to get three independent measurements in a single measurement cycle (i.e., using three ADCs simultaneously) to solve the system, but maybe there is a clever way if I only need one resistor value and not the other two? Or, in terms of how to arrange everything for each measurement, is there a better way, using a bridge or somesuch, to make the measurement more precise (making best possible use of the ADC)?


texts: Calculating resistors for an optocoupler controlling a pmos

texts:
I want to use a pmos (SI7157DP-T1-GE3, datasheet) as switch - controlled by an optocoupler (TLP291(V4GBTP,SE, datasheet) which is controlled by a teensy 3.6 (3V3 output voltage).

Now I'm calculating the appropriate resistors and I wonder if I'm doing it correctly. I don't care much about switching speeds but I do care a lot about longevity of the components.

According to the datasheet typical forward current is 10mA at 1.25V (25°C). I'd like to reduce current to increase longevity.

It's a little bit hard to read but at around 1.17V current seems to be 2mA. So the appropriate resistance of R1 would be 1.065k -> 1.1k

At 2mA the CTR seems to be around 150% = 3mA. So R2 would be 1.666k -> 1.8k. As far as I understand it, this is the minimum value and I could use 10k as well as long as I'm ok with the resulting switching speed.

Am I doing it right? Are R1=1.1K and R2=10k reasonable values? Is there anything else I should take into consideration? Thank you in advance!


texts: Fuse 125V/4A can be replaced with 250V/4A?

texts:
I want to replace a blowed fuse 125V/4A but it is rare to find them. Can I use instead a 250V/4A ?

I read at https://www.mojotone.com/support/Knowledge-Base/Is-it-ok-to-replace-125v-glass-fuses-with-250v-glass-fuses-of-the-same-rating
that

  Fuses are designed to protect over-current, not over-voltage.
  Therefore as long as the fuse amperage is sized appropriately and as
  long as your fuse voltage meets or exceeds your application voltage
  the fuse will safely protect.

So, its ok to replace with 250V/4A ?


texts: How to request “GET” from an ASP.NET website using ESP8266?

texts:
AT+CIPSTART="TCP","zgrdataserver.com.azhar.arvixe.com",80

OK, works.

AT+CIPSEND=92

The response is ">". Works fine, but

GET /androidserver.aspx?param=esp8266 Http/1.1\r\nHost: zgrdataserver.com.azhar.arvixe.com\r\n\r\n

This code, no matter what, always returns either HTTP 400 bad request error or Wrong syntax error. Ironically, all the examples on the internet that I found use thingspeak.com API example. However I want to use my own server to log data. Thank you for any efford, in advance.

For those who wonder http://zgrdataserver.com.azhar.arvixe.com/androidserver.aspx?param=asdf request works perfectly fine.


texts: How can I test my multimeter's battery without a low battery indicator?

texts:
I a few months ago needed a multimeter, and I didn't have one. Not wanting to wait for one to arrive, and only needing it once, I went out to the hardware store and bought a cheap digital multimeter. I bought the cheapest one I could find that was digital, and I guess that's why you can't find it online anywhere. :P No problem getting a low accuracy and build quality (if this one breaks, I'm going to get a newer, better one).

I ended up using it more than I imagined, and it has enough accuracy for my needs (everything that I use is less than +-1.2%), and the only negative is it doesn't have a low battery indicator. If I knew I would be using it some, I would have bought a better one, but this one is sufficient for testing basic voltages, currents, and resistances to easily find the value of a resistor without reading the color codes. Is there a way that I can check the battery without opening it up and using a battery tester? I don't want to mess around with it too much, but I don't have a real need to upgrade besides this, which the money could be better spent on other parts that I want.


texts: Reverse audio jack for front and back speakers

texts:
My problem is a strange one. I have a computer connected to front and back speakers via 3.5mm audio jacks. Sometimes I use the computer with the monitor at my desk. Other times I'm using it to watch movies on a projector on the opposite side of the room.

Depending on whether I'm looking at the monitor or viewing the projector, the front and back speakers need to be switched, but it appears Windows does not provide an easy solution for such a simple task.

What I'm looking into doing is creating a box with two 3.5mm inputs, two 3.5mm outputs, and a switch on top that reverses the audio signal. This should be a simple task, but how can I construct this while insuring that I don't introduce a noticeable amount of static noise into the equation? Also how would I organize this on a breadbord?

Thanks for any input.


texts:
I have an idee fixe to make a clone of Sinclair's ZX80 computer.

So now I'm trying to find out which ICs I need for the basic prototype - and here are a few questions:

it seems Z84C00xxx is a modern substitution for original Z80 processor, right?
for SRAM, will UT62xx or LY62xx be the proper choice (I think of 6264 or 62256 chips, preferably in DIP, though it would not be hard to manage SOIC also);
what to use for ROM? FLASH-chips I can find usually contain megabits of memory while I only need few kilobytes - would EEPROM will do instead? Though it seems there are not very much with parallel interface, but I believe I can get along with Atmel's (like AT28C256)? I also had idea that I can use some MCU with enough pin count and internal flash instead, but I suspect it will not give good timing (unless I pump the flash content to RAM at first).
what series for discrete logic chips I should prefer, I believe 74HCxx or 74HCTxxx should be ok with the given CPU?


texts: When deforming a resonant circuit into an antenna, why can we cut the inductor in half?

texts:
The working principle and fields of an antenna can often be shown by considering a parallel LC circuit. The plates can be moved to opposite ends and the inductor can be stretched out, both of which decreases the capacitance and inductance of the circuit and increases the resonant frequency.

In the limiting case of a half-wave dipole, the antenna must be center-fed (if fed by a current source) and connected to the transmission line. To accomplish this, the inductor in the middle needs to be cut and there is no current flow directly through the inductor:

As can be seen in the picture above, the center is insulated, while this point in the LC circuit corresponds to the center of the inductor, which is conducting.

While in a regular LC circuit a current flows through the inductor, it now moves through the whole transmission line at each cycle. It seems to me that these circuits are not equivalent anymore, since that introduces all the impedance of the transmission line into the circuit.

It's not so clear to me what changes if the inductor is still connected (apart from presenting a short circuit to the transmission line), and does this "cutting" change the inductance of the antenna itself?


texts: How to alternate 2 LED strings using 555 IC?

texts:
I have one sensor that goes on/off at times, I want to flash 2 LED strings (RED, GREEN) every 1 second using a 555 IC.

So when sensor ON
1st second GREEN-ON,RED-OFF
2nd second GREEN-OFF, RED-ON

the 555 IC can sink and source, do I use a P and N channel MOSFETs to drive the LEDS?

Is this schematic correct? have I connected the MOSFETS correctly and also I'm not sure about the 555 timing if it is 1 second ON 1 second OFF

Can anyone suggest different approach

Please help


texts: Simple circuit for a single 10 ms pulse when closing a contact switch

texts: I have a simple circuit (see image below) that creates a single 10 ms pulse when closing a contact switch (SPST) but I also need that after generating a pulse the circuit will wait some time (500 ms for example) until being able to generate a new pulse. The pulse generation works fine but I'm having trouble implementing the wait time, my circuit will generate a pulse each time the contact is closed. Any clues on how to do this please?


texts: Where is the best place to tap into this broken USB flash drive with a new cable?

texts:
Looking for some advice on attaching a USB cable to a USB drive of which the original USB connector has snapped off. It has a bunch of my girlfriend's coursework on it and of course she has no backup...

I have a reasonable foundation knowledge of electronics but am a bit hazy on PCBs.

From what I can make out from the image below, there are 4 solder pads for the 4 terminals of a USB connector. The connector simply solders onto these pads. Normally this would mean that I can simply reflow the solder to reattach the connector.

However in this case, I think that the solder pads themselves have broken away from the PCB as the material exposed seems non-conductive. With this in mind, the next logical thing is to try and expose some metal from the PCB wiring and solder to that. You can see in the image that I have started to do that with the leftmost terminal.

Both this and the rightmost terminal will be okay in this sense but I can't actually make out where the PCB wire is routed for the middle two terminals to scrape away at it.

Was wondering what people would suggest as a means of connecting into this? It's not got to last, just needs to survive long enough to pull the data off of it.

I have also included side and back images for reference.

Any and all help would be appreciated, thanks!


texts: How to troubleshoot overheat/short of microcontroller?

texts:
The PCB I am working on somehow went terribly wrong. As soon as I power up the circuit, MCU(MSP430F6720) starts to quickly overheat and in one case literally smoked. I described this in TI's forum here, but in a general sense, what leads this overheat/short of MCU to happen and how can I troubleshoot the issue?

My understanding is: somehow, either by design or manufacturing of PCB, a short circuit was created inside MCU: 1) Some pin is illegally connected to power supply rail (VCC); 2) Some pin is illegally connected to ground; 3) Power supply voltage exceeds the maximum rating of MCU. Did I miss something here?

Funny thing is, the PCB had been working just fine till I changed the power supply circuit from AC adapter + alkaline battery to AC adapter + lithium ion battery. So now I am kind of back to square one. Any input would be greatly appreciated.

Edit: below is the power supply circuit I used in the problematic PCB. Because I only changed this part of circuit from previous revision, I believe the problem is in this part. The circuit consists of the following three parts:

1) LDO: xc6227, this IC is also used in previous revisions.
2) Lithium Ion charging IC: MCP73844. This circuit has been used in my other PCBs.
3) On/Off push button IC: MAX16054. This is used to turn on/off the power supply.

Update: the problem turned out to be feeding voltage of lithium battery into the analog input. The new PCB with this problem fixed works just fine. Thanks goes to everyone.


texts:
To start off I'm pretty new and have never used a LED strip before. I bought a meter of RGB LEDs off of ebay. The strip is based on the newer LPD8806 chip. I downloaded and tried to run the strandtest from adafruit's library. I can't seem to get it working correctly though. Any suggestions would be helpful.

Strip Wiring
Black  - Ground
Green  - Pin 3 On Arduino
Red    - 5v from ATX PSU
Blue   - Pin 2 On Arduino

Arduino Uno Wiring
gnd    - Shared Ground


texts: Looking for device that help me split a n bit input bus, or n analog lines into two or more bus at output

texts:
I looking for device that help me split a n bit input bus, or n analog lines into two or more bus at output

Please consideration concept diagram below.

At input there is n bit input bus, or n analog lines

At control there is 2 bit control:

00: input signal not routed to output
01: input signal routed only to output 1
10: input signal routed only to output 2
11: input signal routed to both output

I cannot think of any ready made digital logic device I buy at counted do this, hence need some help to realize this using ready made digital logic device.

Ready to use relay or logic ICs, anything is OK as long as parts easily available.

If digital logic used, must be able to support signals till 1Mhz, 0 to +5Vpp, low (like 100mA) current good enough

If analog drive like relay used, must be able to support signals till 100Hz, -50 to +50Vpp, 10Amp current

Important to keep the size compact. I am ready to use PIC microcontroller if it help


texts: Good board for DIY temperature control/readout

texts:
I want to do a project where the temperature of a device is controlled by toggling on/off a heating element (120VAC),presumeably by using a relay.  I would like a board that has an input for a temperature sensor of some sort and some form of a display and buttons to allow me to create a user interface.

Whether the board itself has the relay or not does not matter (I can use 5V to trigger a 'powerswitch tail' if I need to).  The board would definitely need a display of some sort (nothing fancy needed), some buttons, and the ability to measure temperature accurately (+/0 0.5 °F worst case).  Does anybody know of anything that fits the bill?


texts: The Joule Thief is what kind of oscillator? Armstrong? Relaxation? or what? Thanks!

texts: On Wikipedia, the Joule Thief is described as being an Armstrong oscillator, which I strongly believe it is not (because it has no capacitor).  But the Wikipedia article tries to back up this statement by citing a scholarly article, "Fun Examples for Teaching Linear and Nonlinear Circuits" which states that the Joule Thief is an Armstrong oscillator.  Please state why the Joule Thief is NOT an Armstrong oscillator, what kind it really is, and why.  (Even if it really is an Armstrong, then I'll be satisfied.)  If this is a mistake up on Wikipedia, then perhaps we can fix it and cite this page along with justification for changing it to a "relaxation oscillator", or whatever it really is.


texts: Why does this Verilog replicator statement produce a 64 bit long wire?

texts:
I'm attempting to capture the carry out of the addition of two N bit numbers with a carry in. My code is:

module alu(a, b, f, cOut, z);
   parameter size = 8;          // how many bits is each input
   parameter n = size - 1;

   input a;                     // operand a
   input b;                     // operand b
   input f;

   wire [n:0] a;
   wire [n:0] b;
   wire [2:0] f;
   wire [n:0] sum;
   assign {cOut,sum} = {(n+1){a + b + {n{f[2]}}}};

In my inner replicator, I'm trying to zero-extend the bit at f[2] to be the size of the operands (f[2] is the carry in). With the outer replicator, I'm trying to zero-extend the addition to fit in n+1 bits. Then cOut will be set to the MSB, which will represent the carry out.

Here's the error that Verilator reports:

% verilator -cc alu.v
%Warning-WIDTH: alu.v:22: Operator ASSIGNW expects 9 bits on the Assign RHS, but Assign RHS's REPLICATE generates 64 bits.
%Warning-WIDTH: Use "/* verilator lint_off WIDTH */" and lint_on around source to disable this message.
%Error: Exiting due to 1 warning(s)
%Error: Command Failed /usr/bin/verilator_bin -cc alu.

Does anyone know why Verilator thinks that the RHS will be 64 bits? And is there a better way to write this without nested replicators in Verilog?


texts:
So I need to demodulate the FM signal from a sensor with highest SNR possible, at least 70-75 dB. IF is 10.7 MHz, max. deviation is 200 kHz but I can change those values if needed. Baseband signal frequency range is 60-5000 Hz. There is a space constraint: PCB should not be larger than 18x40 mm. It also would be nice if the circuit could be powered from a 3.3-5V source.

Quadrature detectors I find have SNR of <60 dB which is insufficient. The only solution I found is NJW2311V but I can't find it for sale. Maybe there are other options?


texts:
My rowing machine is powered by batteries and is reading a REED sensor for activation/deactivation on 3.3v (console).
I did an other circuit on arduino 3.3v but plugged in USB and I want to read the same sensor at the same time.
One way or the other works fine but what about when the 2 circuits are plugged on the same sensor?
Here is a little diagramme.
Will this shoot 3.3v in my arduino?
Will this affect the reading of the sensor?


texts: Non-invasive current sensor noise problem

texts:
I'm working on a project where I'm measuring current with a split core CT and feed the signal to an Arduino analog input.
The problem I'm facing is that I get noise from nearby systems.
Example is when I wire up a small electrical pump (about 250mA), and hold my split core current transformer next to it (without clipping it onto the wire!) I still get readings on the analog input.

This will be a big problem as I'm planning on sensing current at locations where there will be other wires conducting current around.
The split core CT I'm using is the SCT-013-005.

Does anyone have any solution for this problem? Is it simply a poor quality current sensor that is not isolated from outside electrical noise?
I have not yet tried to measure current with the CT, and have another component nearby drawing current.


texts: Pressing one key in a button matrix reads all keys in that column

texts:
I'm using an MCP23017 IO Expander to make a button matrix (4x4).

//Defines for Matrix Rows/Columns
#define ROW0    0x10
#define ROW1    0x20
#define ROW2    0x40
#define ROW3    0x80
#define COL0    0x01
#define COL1    0x02
#define COL2    0x04
#define COL3    0x08

void bRead(){
    mcp_send_command(IObut1, MCP_GPIOB,ROW0); //Row0 High
    mcp_read_command(IObut1,MCP_GPIOB); //Read the Port, state stored in 'receive' variable
    k1 = (receive&COL0); //If the Col0 bit is set, then K1 was pressed
    k2 = (receive&COL1);
    k3 = (receive&COL2);
    k4 = (receive&COL3);
    mcp_send_command(IObut1, MCP_GPIOB,ROW1);
    mcp_read_command(IObut1,MCP_GPIOB);
    k5 = (receive&COL0);
    k6 = (receive&COL1);
    k7 = (receive&COL2);
    k8 = (receive&COL3);
    mcp_send_command(IObut1, MCP_GPIOB,ROW2);
    mcp_read_command(IObut1,MCP_GPIOB);
    k9 = (receive&COL0);
    k10 = (receive&COL1);
    k11 = (receive&COL2);
    k12 = (receive&COL3);
    mcp_send_command(IObut1, MCP_GPIOB,ROW3);
    mcp_read_command(IObut1,MCP_GPIOB);
    k13 = (receive&COL0);
    k14 = (receive&COL1);
    k15 = (receive&COL2);
    k16 = (receive&COL3);
}

Just to run through the logic, in case I'm missing something obvious:

Rows set to output, Columns set to input
Set one row high, and read the columns.
If a column is high, then the key in that column, on that row, is pressed.

The problem I'm having at the moment is that when I press a key, then any key in that column will read as pressed when I go through the rows. Eg: If I hold down Key1 and set Row0 high, then I read the key without issue. But if I keep Key1 pressed, then Key5 reads as pressed when I set Row0 high, then Key9 on Row2, and Key13 on Row3 (likewise for the other columns).
The previous row is set low when I move onto a new row, so there aren't two rows high at any given time. I've tried setting all rows to zero, adding a 10ms delay, then setting the next row high to ensure it's not just catching the result before the previous row goes low. I've also tried setting the internal pullups on/off for rows/columns/both.
Any help would be greatly appreciated - hopefully I'm missing something obvious.


texts: Several names for same/similar registers in PIC32MZ USB peripheral?

texts:
I am working on my first PIC-project for which I am utilizing a PIC32MZ2048EFH064. Right now I am struggling with some registers of the USB peripheral that are named differently in the datasheet than in the debugger.
For example, according to the datasheet, the USB endpoint 0 is configured by the registers USBIE0CSR0, USBIE0CSR2, and USBIE0CSR3. However, in some code examples in this forum the registers USBE0CSR0, USBE0CSR2, and USBE0CSR3 are used. These are also the only registers accessible by the debugger. In the datasheet (p. 213) it is written that both sets of registers are indexed by the same bits (see screenshot).

However, the registers contents differ (see additional screenshots from the datasheet (p. 225) and the debugger) which confuses me. The register USBIE0CSR0 is not available in the debugger at all.

Can anybody explain why there are these two sets of registers and tell me which to use?
Thank you!


texts: Component case size and spacing for ESD protection circuit

texts:
As im searching for TVS diodes, I see a 30KV rated diode array has pins RIGHT next to each other. Aren't they so close that a spark can easily jump between pins??

I read a few time that you need a certain case size for protection components so that Sparks don't jump the components, yet I see 30KV rated bidirectional TVS diodes with a 0402 case size!

I need to make my protection circuit as compact as possible and as high rated as possible. I'm having a hard time finding component size, and spacing guide. Anyone can help? Thanks!