texts: What does "AC frequency response : (60-1000)Hz" mean for multimeters?

texts:
I'm considering to buy a multimeter. The following is its specs as listed at Amazon:

Size:KT6666

Featuring a wealth of functions, it is intended for troubleshooting various electrical issues arising in household, industrial and automotive devices.

Features:

Fast, accurate measurements at 3 readings per second update speed;

Backlit LCD Screen with perspicuous readings display;

Overload protection in all ranges;

Heavy duty build, suitable for indoor & outdoor use;

6000 counts display with TRMS , Large LCD size at 6.2*3.8CM

Rubber holster to protect the meter dropping when use.

Multi meter Specifications:

DC Voltage: 600mV ±(1.0%+10)
DC Voltage : 6V/60V/600V/1000V ±(0.5%+3)
AC Voltage (True RMS): 600mV ±(3.0%+3)
AC Voltage: 6V/60V/600V/700V ±(1.0%+3)
DC Current: 600uA/6000uA/60mA /600mA /10A/20A ±(1.5%+3)
AC Current: 600uA/6000uA/60mA /600mA/10A/20A ±(1.5%+3)
Resistance: 600/6k/60k/600k/6M/60 MΩ ±(0.5%+2)
Resistance: 60MΩ ±(1.5%+3)
Temperature: -20~1000℃ (-4~1832℉) ±(1.0%+5)
Capacitance: 10nF ±(5.0%+20)
Capacitance: 100nF/1uF/10uF/100uF/1000uF ±(2.0%+5)
Capacitance: 10000uF ±(5.0%+5)
Frequency:99.99/999.9/9.999k/99.99k/999.9k/9.999MHz,±(0.08%+2)
Duty Cycle:1-99%,±(0.8%+2)
Range Selection: Auto / Manual Ranging
Max Display: 6000 counts
Sample Rate: 3 times/s
Diode test: Yes
Continuity buzzer: Yes
Low battery indication:Yes
Data hold:Yes
Auto power off: Yes
Restorable Fuse protection: Yes
Shock proof protection: Yes
AC frequency response: (60-1000)Hz
Battery: 2x1.5V (INCLUDED)
Dimension: 180*90.5*45mm
Product Net Weight: 343g
Working environment: 0~40℃, relative humidity < 80%"

From:

https://www.amazon.com/KASUNTEST-Multimeter-Capacitance-Resistance-Transistor/dp/B01L9F09NM/ref=s9_simh_gw_g469_i1_r?_encoding=UTF8&fpl=fresh&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=&pf_rd_r=QCNF28ZDGZC93PVZTEE3&pf_rd_t=36701&pf_rd_p=1cded295-23b4-40b1-8da6-7c1c9eb81d33&pf_rd_i=desktop

====================================================================

Question:

This meter is advertized as a true RMS multimeter. What does "AC frequency response (60-1000)Hz" in the specs mean? Is it this meter's sampling rate to calculate RMS? If so, how does it compare to other true RMS multimeters'?

After writing the above, I just noticed that there's "Sample Rate: 3 times/s" in the specs. Is this the sampling rate to calculate RMS? Isn't this pretty low?


texts:
Sometimes when encountering an opamp or comparator input I see an RC network topology similar to the following one:

And in this case let's say we know everything but the value of C2, and we want to set C2 to a value to obtain the right low-pass filter effect.
But to calculate the cut-off frequency one needs to know the equivalent resistor value of all the network before C2 (only at the left side of C2 the equivalent resistance matters since the signal is coming from left?).

Only after knowing this approximate equivalent resistance one can set C2 to obtain a desired low-pass filter.

First of all for simplicity the unknown output impedance of the input signal is neglected(even-though it might have a big impact if it is big).
Here are the steps I followed to thevenize this circuit.

To thevenize the circuit, Vcc is shorted and C3(DC blocking capacitor) is shorted as follows(R2 and R4 becomes in parallel):

Thevenizing R7 and R9 the circuit becomes(Thevenin voltage becomes Input/2):

Now second thevenizing yileds(Thevenin voltage becomes 5*Input/32):

So the final RC circuit simplifies to:

And now I want to compare the frequency response of the original and thevenized circuits:

Here is the freq. response of the original circuit:

And here is the freq. response of the thevenized circuit:

My questions are:

The cut-off frequency definition is where the ouput is 3dB less than the output at DC. Following this definition yileds very similar cut off frequencies.
The cut-off freq. in both are very close. One is around 7.8Hz the other is around 9.3Hz. I think that's the effect of neglecting C3 at the beginning.

1-) The resistors in the original network drops the input voltage at each stage until the output.
But in the Thevenin circuit we have no similar loss.
The final Thevenin voltage is 5/32 of the original one. So I would expect a power ratio (5/32)^2 which is around 32dB. But the difference at DC is around 18dB. What could be the reason?

2-) Is my way of using Thevenin here correct for practical rough estimate? And similarly can I use the Thevenin with R7 R9 C3 (ignoring the circuit after C3) to see the high-pass filter effects roughly?


texts: Analog computing vs Numerical simulation

texts:
Does the electronic circuit equivalent of a mathematical model have any inherent advantage over numerical simulation of the same model ?

For instance, if I numerically simulate the Navier-Stokes equation and obtain a time-series of the velocity field and compare with the time-series of the voltage from an electronic circuit equivalent of the Navier-Stokes equation.


texts: Understanding a "state variable" RC-active filter

texts:
I have the following "state variable" RC-active filter:

If the input is a square wave, then when measuring the output I get a sine wave (channel 1 is the input and channel 2 the output):

And I don't understand why that happens. Could you try to explain it to me?

Edit:
The values are:
R1=11000;
R2=11000;
R3=7960;
R4=100;
C=10nF


texts:
When I'm trying to output something using DAC the voltage appears on pin A3 not on A4 as expected. Am I missing something?
#include "main.h"

DAC_HandleTypeDef hdac1;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_DAC1_Init(void);

int main(void)
{
    uint32_t DAC_OUT[4] = {0, 1241, 2482, 3723};
    uint8_t i = 0;
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();
    MX_DAC1_Init();
    HAL_DAC_Start(&hdac1, DAC1_CHANNEL_1);
    while (1)
    {
        DAC1->DHR12R1 = DAC_OUT[i++];
        if(i == 4)
        {
            i = 0;
        }
        HAL_Delay(50);
    }
}


texts: Multiplying signed to unsigned binary numbers in verilog

texts:
How can I multiply a signed number to unsigned number in verilog for example:

a = 6'b111111 ; //which is means -1 as it is signed

b = 6'b111111 ; //which is means 63 as it is unsigned

I want the result be -63 which is 1000001 which is signed number


texts: What is the characteristic of piezo transducer?

texts:
I want to detect the tap/sound, I am using piezo transducer (circular) and connected it to raspberry pi using ADC (MCP3008, SPI communication). When I tap on the transducer the output value should increase somewhere between 0 to 1023 depending on the tap vibrations. But I am getting reverse output values, the output value read is 1023 when I do not tap and when I tap it continuously the output value reaches to 0(Zero). Could anyone tell me the reason for this? I have connected red wire (+ve) of transducer to the CH0 (channel 0) of ADC and black wire of transducer to GND of raspberry pi. I think the connection is perfect. Is that characteristic of Piezo transducer, to send output low signal when tap is detected and high signal when no tap? Below is the code

#!/usr/bin/python

import spidev
import time
import os

# Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)

# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7
def ReadChannel(channel):
  adc = spi.xfer2([1,(8+channel)<<4,0])
  data = ((adc[1]&3) << 8) + adc[2]
  return data

# Function to convert data to voltage level,
# rounded to specified number of decimal places.
def ConvertVolts(data,places):
  volts = (data * 3.3) / float(1023)
  volts = round(volts,places)
  return volts

# Define sensor channels
piezo_channel = 0
piezo_level = ReadChannel(light_channel)
piezo_volts = ConvertVolts(light_level,2)

  # Print out results
  print "--------------------------------------------"
  print("Light: {} ({}V)".format(piezo_level ,piezo_volts ))

  # Wait before repeating loop
  time.sleep(delay)`


texts:
For a project I've been building, I've been using the (overused) ZVS oscillator that can be found online. So far it's been working great transferring power wirelessly, but I'm interested in understanding the schematic.[

I understand that the frequency of the oscillating wave in the lc tank is given by f=1/(2pi*sqrt(LC)).

I also understand that in the ZVS configuration, mosfets only switch between on and off right when their gate voltage is 0.

What I'm having troubles understanding:

1.) What exactly are the paths of the currents? I think one path is from L1 to the LC tank, and out to the drain of M1, but since now the current is in the opposite direction, what exactly is the other path?

2.) Why does the switching effect occur? Is there current on the gates of the mosfets?

3.) Are the chokes used to suppress any AC from coming back to the bench supply?

I've looked online and while I've run a spice simulation, I'm still having difficulties understanding it. Thank you in advance!

What I think happens (and I'd appreciate corrections):

Let's focus on gate of transistor M1. Current follows from the top resistor, and most of the current will flow towards D2 since the resistance at R3 is very high. Since the Vgs on the mosfet is the voltage on R3, and most of the current is flowing through D2, then M1 will shutoff.

If I remove M1 from the picture, the only path remaining is from L2 to the top of the LC tank, and that current meets the current from the diode and goes down the drain of M2.

Now that M1 is off, and it's ZVS, it will slowly switch to being on, and slowly the current from gate of M2 will go to the drain of M1, and the new path, if we take M2 to be off, is from L1, through the bottom of the LC tank, and through the drain of M1. The current thhrough D1, from gate of M2 to drain M1 also goes through the diode to the drain.

Does this seem correct? I'm still not sure as to what the RF chokes are for (L1,L2)


texts:
Before someone complains about my crappy design I should tell you that my knowledge on antennas or RF is near zero.

I recently worked on a project that required a GSM module. After testing it on a PCB using an external antenna that apparently seamed fairly simple, I made a new PCB with a built in antenna.

It worked well but I noticed that the signal was significantly lower than the one with the external antenna. I also noticed that if I touched the antenna connection with a wire the signal increased in strength close to the one with the external antenna.

My board is a double sided board with a ground plane with a clearance distance of about 2 mm from the antenna on one nearest side. The antenna is located near the edge of the board as can be seen on the picture.

Is there something that I could do to improve my antenna performance? Currently the antenna has solder mask on top of it, can this degrade its performance? Is it better to have it plated instead?

Full board


texts: I wonder if it'd be a relatively straightforward exercise to read data from a 3.5mm audio jack using an Arduino and a raspberry pi. The communication will be one-way only: raspberry pi transmits data to Arduino, so the Arduino will do the reading. Does anyone know how this could be accomplished without using a modem?


texts:
I have seen the Cyclone III datasheet and it claims DDR and DDR2 compatible PHY.
But was looking some good LPDDR chips for my design.
Could I use the PHY inside of Cyclone III with LPDDR ic?
Do you know other FPGA compatible with LPDDR?


texts:
If there is one RF source with a known characteristic impedance, and there are multiple loads connected in parallel with each other, each with their own matching circuit, and if the electrical distance between the loads is negligible, then: would an ideally perfect match require that the equivalent total parallel resistance of the loads equal the resistance of the source? This is a theoretical question but I would eventually try applying it to a system with one antenna and three receivers. (there is no transmit.)

Here's an example. It's not optimized but it illustrates the point. Each of the matching sections is seen by the source as 900 ohms.


texts: What size/kind of diode to use for a lawn tractor charging circuit

texts: I have a lawn tractor which is not charging properly.  I only see 25-28 V AC out of the engine to charge the battery.  I can't seem to locate where the diode or rectifier is.  When this fails, is it common to see the AC pass through?  Can I just add a diode into the charging circuit and if so, what would be the type/specs of such a component?  Thanks for your help.


texts: Increasing the PWM voltage level from 1.8V to 3.3V

texts: I need PWM pulses of 3.3V, and my micro-controller is giving 1.8V PWM signals. I have a voltage source of 3.3V. One way I am thinking is to use two cascaded inverters(like NOT-GATE) using MOSFETs. Is there any other good ways to do this?


texts: Determining if mystery PCB with barrel jack power connector is center positive or center negative

texts:
I lost the power adapter to the module used to drive a LIDAR sensor I have. I am planning to make a new adapter but one problem I am running into is that I can't figure out if the module's PCB sources positive power from the center of the barrel jack or from the outer of the barrel jack.
What are some strategies I can use to figure out which the PCB uses?
Edit: thanks for the help everyone but I took the easy way out and emailed the manufacturer. I thought this would be a total shot in the dark but figured it was worth a try before I break something. To my surprise they actually wrote back and told me what was what.


texts: Atmega328P Watch Dog Timer - Delay Issue

texts:
I am trying to give delay of 0.5 seconds on 13 pin of the arduino using Watch Dog timer interrupt, the code complies and works fine but the led  is blinking so rapidly that it seems like it is blinking at a delay of 50ms not with a delay of 0.5 second. Please help.
Thanks in advance.

#define F_CPU 16000000UL
#include<avr/io.h>
#include<avr/interrupt.h>
#include<avr/wdt.h>

int main(void)
{
  cli();
  wdt_reset();

  WDTCSR |=(1<<WDP2) | (1<<WDP0);

  WDTCSR |= (1<<WDIE);
  WDTCSR |= (1<<WDE);

  sei();

  DDRB |= 0b00100000;

  PORTB |= 0b00000000;

  while(1)
  {

  }
}

ISR(WDT_vect) {

 PORTB ^= 0b00100000;

}


texts: Frequency vs. Amplitude modulation in a circuit?

texts:
I'm trying to create two circuits that will eventually be added to a larger circuit in a custom PCB. A basic radio transmitter needs to hook into my computer via USB, and transmit data to a rudimentary radio receiver, which connects to the UART of a micro-controller. (As far as I understand, I should be able to send, receive, and translate serial data this way.)

I've done quite a bit of research, and even discovered a post on this site asking a similar question here...

How exactly are radio waves produced from a current in a circuit itself?

I would LIKE to know exactly how RF propagation works, but I'll settle for at least knowing how to build the circuit.

I found a site here that was the most helpful...

http://www.intuitor.com/resonance/circuits.html

But, it leaves some things to be desired. As far as I understand, a capacitor is charged, and used to store and release energy into an inductor. The inductor then builds up its electromagnetic field gradually until all the current is out of the capacitor, then releases the energy stored in the field back to the capacitor in the opposite polarity, forming one wave. Unfortunately, the capacitor and the inductor MUST have a resistance value, so the current will gradually diminish with each wave.

Is amplitude of the waves modulated by the amount of current? Frequency is modulated by the frequency of the capacitor release of energy, correct? That would mean that using a capacitor with a lower farad rating should produce a higher frequency?

How would one go about keeping a sustained current to the inductor since it's constantly losing current without messing up the cycle?


texts: How dangerous are utility poles for the average person?

texts:
There are quite a few utility poles along the sidewalks outside my house. They all seem to have ground wires , and some of them also have guy wires. (i'm getting these names from the diagram here)

For the average person walking on a sidewalk, are any of the wires (particularly the ground and guy wires) dangerous in normal circumstances - as in, if someone were to accidentally touch either of the wires, would they be electrocuted? If these aren't normally dangerous, are there special circumstances in which these are dangerous? How cautious do I need to be around utility poles?


texts:
Here is the circuit.

Now what would be the voltages at Node Y on the positive edge of the clock, if Switching Time from on to off and off to on of Transmission Gates are : 0.5ns, 1ns, 2ns


texts: How can I show a tied-off output on a digital logic schematic?

texts:
Combinational circuit that takes 3 bit binary numbers as input and its output is 2's complement of even number and 1's complement of odd number
Hey,
I have this assignment that I'm supposed to do. I've tried it myself but I'm stuck. Please help me complete if my process is right.
First, i made a truth table with 3 inputs and 4 outputs:

On Drawing the K-Maps, i found that:
A=x'y'z'
B=x y'z' + x'y + x'z
C=y'z+yz'
D=0
I then drafted out the circuit diagram, but i'm not sure how to show D's diagram since D=0

How do i show the D circuit?


texts: Replacing a LM741 op amp with higher quality op amp?

texts:
I am a complete novice with electronics...but i'm looking to build a replica of a discontinued TC Electronic Integrated Preamp. Its a basic line booster with Volume, Bass and Treble but sounds great when you feed it with 18-32volts. The schematics are out there and i'm looking to just copy it and try to build a basic one using a breadboard to begin with.
I was wondering though would it be possible to use an op amp from something of much higher quality. I wondered if it would be possible to experiment with putting an op-amp from hi end audio gear into it. Something like this for example:
http://www.sonicimagerylabs.com/products/product_images_docs/990Enh_Ticha_Docs/990Enh_Ticha_Datasheet.pdf

Heres the details for the TC Preamp:

http://www.aronnelson.com/gallery/main.php/v/slackers-stuff/tcpreboardfinal.jpg.html


texts: Is it possible to use a heatsink without a peltier plate?

texts:
At the moment I am working on a project which implies LEDs for street lighting. I need to dissipate around 24 W of heat. In order to do so, I calculated how much heat is dissipated into the air, and now I am considering using a heatsink and maybe a peltier plate. The problem is that I would like to use only the heatsink without the peltier plate, due to high power consumption of the plate. Is that possible?

OK. I will explain more detailed the problem that I have. We as a group, are trying to develop an LED street light powered by a solar panel. The project is build for Denmark and its weather conditions.

We did some testing on different types of LEDs (modules with different light output and energy consumption). The result of the test is that one of the LEDs used is, of course, the most efficient compared to the other ones. But in the datasheet is stated that it should use 14W, while during the test it was using 40W. This gives us a low efficiency, so I assume that the rest of 26W is transformed into heat.


texts: THS4521-HT: Op-Amp giving negative differential voltage

texts:
Can someone help to explain where I get wrong with this schematics? I use a differential op-amp THS4521 and want to measure the differential signal coming from a pressure sensor (transducer).

The sensor is powered from 5V and it has a range of 0-1000bar. Without connecting the op-amp at 0 bar it gives differential voltage (between P+ and P-) of 0.14mV and 1000bar it is 14mV.

Therefore I used this op-amp to amplify the voltage and measure it with an ADC.

The ADC has no internal gain, therefore it must be like this.

Problem is that when the sensor is connected to the op-amp it gets an offset of ca 3mV.

After reaching 25bar the values on the output of op-amp go below 0mV. Since I cannot measure negative differential voltage with the ADC, I have a problem.

I could swap P+ and P- but then I cannot read anything below 25bar.

Sensor is powered from 5V source, the op-amp from 3.3V. Rest is on the attached picture.

Does anyone has experience with this op-amp and could tell me some hints?

I hae got some inputs like apply some voltage to Vocm to get rid of the offset. I tried to apply 2.5V as I had a reference voltage available near the op-amp. I pulled Vocm up with 10k resistor. Unfortunately, the circuit still does not function as it should.
As a result, offset is still there, only it occurs in different place, at 37 bar. Vocm, instead 2.5V is going down to 2.4226.

Sensor input (voltage between P+ and P-) is however not going negative, as it was before. So I observe a strange behaviour that the input voltage is rising with rising pressure but output is going negative above 37bar.
In the end of testing I have disconnected the 2.5V, leaving Vocm floating, so similar to initial case, only without two 100nF capacitors coupling to ground. Then the voltage on that pin was 1.72V, almost the same as on output ADP+ and ADP-.

Was the 10k pull-up resistor too big? Was the applied voltage too high?
I am out of ideas so far. Does anyone here have a suggestion what can I try next?

Thanks in advance.

Comment:

I cant change the Op-amp right now but i am considering it to change in the next design.I am thinking INA128 Op-Amp from texas would the job since we need high temp component. Is there any way to improve with existing design.


texts: Confusion Between Dual Capacitor/Inductor Circuits

texts:
I'm trying to physically understand the responses of this pair of (dual) circuits: a step current source driving a capacitor and a step voltage source driving an inductor.

simulate this circuit – Schematic created using CircuitLab
The capacitor output voltage is a ramp and the inductor output current is a ramp, as expected. I understand fine how to mathematically derive these responses, what I'm trying to do is physically explain them.
What I have for the capacitor is that if we assume zero initial charge on the capacitor, then its initial voltage is zero because there is no charge difference. At time t = 0 the current source steps to some \$I_0\$. This means that, by definition of current, the source is now transferring charge onto the plates of the capacitor such that a charge separation develops on the plates over time. Assuming an LTI capacitor such that \$ q = CV \$, the voltage ramps up since the charge difference on its plates is being increased at a constant rate.
I can't quite articulate an equivalent description of the inductor circuit. I have a basic understanding of the phyiscal origin/operation of an inductor but I'm struggling to put it together here. My understanding is that, assuming an LTI inductor, it is defined by the relationship \$ \phi = Li \$, where \$ \phi \$ is the total flux linked through in the inductor. I also know that by Faraday's law, \$ v(t) = -\frac{d\phi}{dt} \$, so we can differentiate the inductor relation to get \$ v(t) = L \frac{di(t)}{dt} \$ (dropped the minus sign). From here I can mathematically derive current as a function of voltage, but why is this constant (step) voltage source apparently causing a constant change in magnetic flux that causes the finite change in current?
When I think of a change in magnetic flux through a current loop that induces an EMF and a current, I think of something like this:  I don't see how the voltage source creating a constant voltage across the inductor's terminals does this.


texts: How can PAL (TV) encode 3 colors in 1 phase?

texts: As I understand it luminance is the amplitude of the signal, and color is the phase. You need 2 color signals (the third one can be derived from the other 2, like B = 1 - R - G). How can 1 phase signal encode 2 colors?


texts: Does Apple or Qualcomm do product binning for their SoCs?

texts:
It's well known that Intel does product binning with their CPUs — essentially selling the same chip as multiple different chips with different specs and prices based on the tested properties of the chip.

My understanding is that this has to do with the fact that there's a lot of variation in the cutting edge IC manufacturing.

So how does a company like Apple deal with it? They don't have 10 different products with same generation CPU but different specs. They have just one, say, A10 chip that's in at most two-three different products (often just one), and they all have to work.

So how does it work? Do they purposefully build chips that are driven lower than they could perform to smooth out the variation? Do different iPhones have differently-performing CPUs? Does the same version of the chip put in iPhone/iPad/iPhone Plus actually have different specs (therefore allowing for some binning)?


texts: Meaning of TV Backlight LED strip details

texts:
I am learning electronics and I just disassembled a broken TV with the purpose of reconverting it into a smart light lamp.
The issue is that I don't understand the details of the backlight LED strips. Could I get some help? I cannot get to find the manufacturer datasheet.
I would like to understand every detail, but the critical questions are:

What voltage should I input?
Can I dim the light?
What's the current being used?

I did some measures with a multimeter and got that when the TV is OFF there is 39.5V and 0A and when it is ON, 44V and 1.91A, but I wanted to double-check it with the specs.


texts:
I'm trying to make my own Arduino based board. I need to have at least 25 digital I/O and no less than 8 analog in pins. I decided on the Atmel ATMega2560 because of its large capacity for both of those. My problem is that I can't find a solid way to burn the Arduino bootloader onto it. From reading online, it seems it's either a hit or miss.

So my solution is to buy a "fake" Arduino board that has the ATMega2560 onboard already, and then desolder it off and use it for my project.

What method would be best for removing the IC without damaging it?

Thanks!


texts:
I have been doing some research on this question and, while I found a number of questions here asking something similar, I don't quite get the side-by-side comparison I am looking for. Therefore I decided to ask my own version of the question.

I am designing a PCB which will eventually be fitted inside an aluminum enclosure and used outdoors exposed to the elements. A number of other devices are connected to this box through potentially long lengths of cable. Since this device will be exposed, I need to do my best to protect the PCB from nearby lightning strikes and similar events. The enclosure itself has a large copper ground lug to which an external earth ground strap is attached. The ground strap is connected to a large grounding rod pounded deep into the earth. My question pertains to the connection between the PCB and the aluminum enclosure.

There are two options that I would like to compare:

A heavy-duty wire about 3-6 inches long is soldered directly to a large earth ground pad on the PCB which connects to a copper pour covering the top and bottom layers of the board. This wire then connects to the back of one of the ground lug mounting screws with a large ring crimp connector.
Earth ground contact is made between the PCB and the aluminum enclosure using four large copper-plated mounting screws which secure the board in the box via the provided tapped mounting holes. The mounting holes/pads on the PCB are plated through and connect the PCB to earth ground by way of the copper-plated screws.

Which of these two options is preferred to ground the PCB and protect against EMI and/or large surge events? Obviously I am looking for the lowest-impedance option, which intuition would tell me is the one where the ground connection is made through the mounting screws, but there has been some discussion of the opposite being true.


texts: How does energy dissipates in a purely reactive circuit?

texts:
Suppose in a home, power factor drops to zero. It means that the circuit becomes purely inductive.

If the energy meter is connected at incoming power supply point,will the energy meter still keep on increasing? If yes, then where is this energy being consumed?

We know that reactive power keeps on oscillating between source and load, so in this case, how does the reactive power fits into picture?


texts: How to limit current for voltage regulator/decrease power dissipation?

texts:
I need to power a 5V device that needs more or less 1.2A in order to work correctly. I'm using a 13.8V power source with two diodes in series (1N4007) to limit the voltage to roughly 12V. I tried using the voltage regulator AZ1084T, since it has 5.0A of maximum output current, but even with a large heat sink attached it was heating up a lot, like 117°C (and the maximum admissible temperature on the datasheet is 125°C).

So, just to test, I replaced the AZ1084T by the old and good LM7805CV, which has 1.5A of maximum output current. It worked just the same, heating up just the same (and that's a good thing, because this one is much cheaper). But how can I avoid the heat? I'm pretty sure it's the power dissipation from 12V to 5V that's causing it, but this voltage regulator was supposed to work with that input voltage.

I tried this scheme, using TIP127 to "split" the current, but my device won't even turn on (the measured output current was showing peaks of 2A~3A, which kept turning off the power source which limit current is 1.7A).

Anyway, any suggestions on how to split the current while maintaining the output voltage or on how to decrease the power dissipation are welcome.


texts: Multiplexing RF Sources to a Single Output

texts:
I have two wide-band VCOs, one 800-1600 MHz and the other 1600-2700 MHz which I would like to multiplex so that they can share the same output (SMA jack). (They are both configured to produce ~5 dBm signals) That is, to achieve the following:

simulate this circuit – Schematic created using CircuitLab

I tried using two "RF Switches" in the following fashion, to achieve this effect, but the setup doesn't seem to work. The result is that both sources are significantly attenuated (about 10 dBm), no matter which source is selected. (Removing one VCO and switch, however, allows me to connect and disconnect the other VCO from the output as expected)

simulate this circuit

What component/circuit/method should I use instead? I would eventually like this to scale to 4 or 5 sources.


texts:
I have a square wave the oscilates at 25khz from 0 to 30v.  I would like it to oscillate from -15v to +15v.  Is there a SUPER DUPER SIMPLE circuit to do this?  Keep in mind it's going up and down at 25khz.

Here's the circuit.  The square wave I want to shift is going into the PiezoSpeaker at the lower right of the circuit.


texts: Use of backwards facing diode next to motor

texts:
While tyring to figure out how to best control a 12V device from a raspberry pi or arduino I ran into the following image:

Now I'm wondering, what is D1 doing there? What's the use of that one?


texts: Differential communication, VCC and GND recovery

texts: modern MCUs are consuming so little power that I started thinking about using only two differential data transmission lines for sending not only data but power also. I made a simple schematic below of the idea. I am sure it is nothing new, but how to do this properly? I would like to achieve proper 5V TLL output range on the data line (opamp output). If you would like to play with it in the online simulator here is the link.


texts: Making a notch filter fo 500Hz frequency

texts: I am trying to make a notch filter which blocks 500Hz, I beleive it should look like the circuit below. Any idea how can I find the proper values to make it not to pass 500Hz? I tried to give random values in LTSPICE but no success yet!


texts:
I was looking at M851 motherboard schematic to learn something from these documents and saw an interesting circuit for microphone. look:

1- What are the purpose of those resistors and capacitors network before the mic jack? for filtering? How do they work?

2- which one of these lines bias the capacitor microphone?

Looks like the gain of the both Op-Amp isn't so high? am I right? why? because I've worked with these kind of Microphones, you need a gain around 200 to amplify the output of the Mic.


texts: ReqForHelp: Understanding Vf relationship to supplied V and A

texts:
Context:
I am a beginner tinkerer at electronics. Conceptually a lot of this is hard for me. But, I plod on. I very much like to use free salvaged components for all sorts of projects, and continue that by salvaging parts for electronics learning/projects.

I have what was a solar-charging sensor-activated LED light. It is not intact, the housing is destroyed, but it works. It has in it an LED panel. I want to re-use this panel in other stuff, but have hit a conceptual wall about how to use the vF I measured.

The Solar Light uses a 3.7 V rechargeable LiPo as its storage. It has three settings via a click button. The first of these settings will send 53.9 mA at 2.57 v to the LED panel (measured on the wires between the board and the LED panel). The second sends 54.5 mA at 2.57 V. The third sends 11.75 mA at 2.28 V.
The first two are "bright" and the last is "dim". I can't see any brightness difference between the two 2.57 V settings even though the A is different.

The LED panel has 28 white LEDs wired in parallel. They are the sort that is flat, square, and has no wire leads. Soldered right to a circuitboard with only the tiniest bit of metal showing on two opposing sides to get probes onto. Luckily I can see the traces through the paint to know it is parallel connected.

In the highest current setting (54.5 mA at 2.57 v from the board to the entire LED panel)
I measured the Vf across multiple individual LEDs, getting a measurement average of .985 V (not mV) with a variance of .015 +/- either side that value. It was starting to get pretty damn hot by the end, since I had to tape over the LEDs to be able to see anything at all as I worked.

But now I am confused, unsure, whatever about whether a Vf measurement at 54.5 mA and 2.57 V is useful if I want to have a 5v supply. I tried using a couple of online calculators for parallel LEDs but they will not accept Vf numbers below 1.

Request:
Could someone help me understand if the Vf I measured is a 'static' thing? I mean, is Vf just Vf no matter what or is Vf dependent on what voltage is supplied to the LED or what current is being supplied? Did I measure a Vf number that is useless to me if I want to use a 3.3 V supply or a 5  V supply? Apologies ahead of time for my thickheadedness, but I just can't make sense of all this.


texts: Why do some WS2813 Ledstrips shift/randomize colors?

texts:
The Problem
I have a project using multiple WS2813 ledstrips, one variant which uses a white PCB and one that uses a black PCB. When setting the colors of these ledstrips multiple times, I noticed that the black PCB strips frequently show an incorrect result. Most of the times it shifts the colors by a few leds but it will also change the colors or shift the leds by 10+.
The PCB
The strips are both WS2813 (at least they were advertised as such). I've attached an image of both the strips below.

Video Example
The following gifs demonstrate the problem I'm having. Both strip types got the command to set leds 25 to 50 to Red.
Gif of Black PCB shifting

Gif of White PCB not shifting

Gif of White & Black PCB on the same data pin. Data is coming from the right, so the shift is always later on the strip.

Connections
The strips are connected as follows:
Strip -- Teensy 4.0
+5V -- External 5V
D0 -- Teensy Output pin (i.e. 19)
B0 -- External GND
GND -- External GND
The Teensy is also powered by the external power supply.
The ledstrips are connected in parallel, with every strip on one of the following pins: 19, 18, 14, 15, 17 and 16.
The strips are only connected at the front, not the back.
Edit: Connecting the back to the power supply does not seem to have any effect on the shifting.
The external power supply is an RSP-200-5 (5V, 40A).
Voltage Measures with only 5 leds active
Led #0: 4.99V
Led #60: 4.97V / 4.98V
Led #110: 4.95V (Sometimes drops to 4.84 on the White PCB)
Datasheets
White PCB Led Datasheet
Diagram


texts: Why the input resistance of a common emitter amplifier is like this?

texts:
I am trying to find the input resistance of this BJ common-emitter amplifier:

I replace the transistor with the hybrid-pi model

It appears clear to me that the input impedance will be

\$ R_{in} = R_1 // R_2 // (R_E + r_\pi) \$

but some authors say

\$ R_{in} = R_1 // R_2 // h_{FE}(R_E + r_\pi) \$

What is the correct value?


texts:
I know that the maximum charging voltage for lithium ion batteries is 4.2v. I also know that charging a lithium ion battery involves a constant current and constant voltage phase.

But what will happen if I continuously charge a lithium ion battery with a maximum of 4.0v at 100mA? Will it destroy the battery?


texts:
I am using VS1053 audio recording IC with a microphone.There, I found some filter circuit.How do they help the IC?
https://www.sparkfun.com/datasheets/Components/SMD/vs1053.pdf


texts:
I am trying to connect a USB relay to actuator, so when I press button 1 , motor goes up, when i press button 2, polarity is switched and motor goes down.
I am trying to achieve this with a DPDT relay. Someone gave me this diagram, however, when i press button 1 motor goes down, but nothing happens when I press button 2. What did I miss ?

Useful info :
Actuator = Motor, connecting 2 at the same time so they both run together
USB Board = USB Relay, but has physical buttons. I have a 4 channel relay, only 2 are used. When I Press button 1 in front of channel 1, motor should go forward, when I press button 2 in front of channel 2, polarity should reverse, thus motor moving backward.


texts: LM741CN Wired as Voltage Follower Will not Output less than 2V

texts:
I have designed a circuit to measure 0-12.2V and Scale it to 0-10V from a PLC input to read. I have put an LM741CN in the circuit as a voltage follow to isolate the test circuit from the measurement circuit.

All is well except that when I input less than 2V into the op amp it stops following the voltage and continues to output about 2V I have input 0V into it and I still get about 2 volts out.

I can't find anything on the spec sheet about there being a minimum voltage output. What am I doing wrong?

simulate this circuit – Schematic created using CircuitLab


texts:
I am currently having problem understanding the basic circuitry of AND gate using diodes and how it works.
As we know, the basic AND gate circuitry using two diodes is something like this.

And we know, that when we connect both diodes to GND (logic 0) , the current flows from Vcc to the two diodes as both are forward biased , and there will be no current passing through the output terminal because all of the current is flown through the diodes for the greater potential difference. If we connect any one of the two diodes to Vcc(logical 1) then there will be no potential difference between the diode connected to Vcc and the main Vcc, so the current will flow through the other diode and again no output current will be got. and if we connect both of them to Vcc(logical 1) then no current will pass from both diodes , hence we will get a current flow(logical 1) in the output pin. (If i am mistaken in this part then please correct)
now, if we connect an LED with the output pin and connect the cathode pin is connected to GND. Just like this following schematic.

here comes my question. When both of the input diodes are connected to GND, there is a flow of current through the two diodes but why not through the LED? because the LED is connected to GND as well. Also when any one of the input diode is in logic 1 state(01 and 10 combination) , then also current can flow through the LED because the LED is also connected to GND , hence there is a potential difference between the Vcc and the cathode of LED. Why is it that only when the two input pins are in logical 1 state , only then the LED will light up?

For a more generalized way, if I use a diode instead of the LED in the output , what will happen?

simulate this circuit – Schematic created using CircuitLab

If there is any problem understanding my question then I sincerely apologize. Thanks


texts:
I am running a simulation in Multisim.  I am currently capturing data with the generic 4 channel oscilloscope component and manually saving the results to file after a short run.  I would like to let my simulation run for a long time, but after a period, the oscilloscope discards all of it's data and starts over.  I've increased the number of samples it will save in the simulation settings, but this only delays the problem.

How can I directly log voltage levels (or other data) to file in Multisim? Or alternatively, what is a better way to capture data from a long running simulation?


texts:
According to the FCC:

  The following devices are subject only to the general conditions of operation in §§15.5 and 15.29 and are exempt from the specific technical standards and other requirements contained in this part. The operator of the exempted device shall be required to stop operating the device upon a finding by the Commission or its representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected. Although not mandatory, it is strongly recommended that the manufacturer of an exempted device endeavor to have the device meet the specific technical standards in this part.

And one of the following items is:

  (h) Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines or contain provisions for operation while connected to the AC power lines. Digital devices that include, or make provision for the use of, battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, do not fall under this exemption.

(emphasis added)

My question is why 1.705 MHz?  That seems like just a random number to me.  Where did they get it? (ie. What maths if any did they do to come up with that number?)


texts: How Could I Implement a Fusable Safety Switch

texts:
I am looking to design a low-level safety override. This override can be represented as a three terminal device that is electrically a switch.

simulate this circuit – Schematic created using CircuitLab

In normal operation, INPUT and OUTPUT are shorted together and OVERRIDE pin is floating. It is important that there is complete isolation (Up to 1KV) between OVERRIDE and OUTPUT as the voltages present on INPUT is 400VDC. A blocking diode may not be sufficient.

During a rescue/safety event, the user applies an override pulse to the override port when the device is turned off. This should permanently connect OVERRIDE to OUTPUT. Allowing an external device to take over the OUTPUT device, and not allowing any further normal function. It is important that there is total non-resetable isolation of INPUT and OVERRIDE/OUTPUT, as the circuit may interfere and damage the rescue box.  (However, a resetable solution can be considered if it is a significantly simpler design)

Is there a circuit that I can use as an example for this type of functionality, or is there a discrete device that serves this fusable purpose.  I would appreciate any input on how to approach this design.


texts: Lamp Test circuit for LEDs with an Arduino

texts:
So I'm designing a project that will have about 75 LEDs and will be controlled by multiple Arduinos. I want to have a lamp test push button so I can light all the lights at once and see any that are broken. So I've been looking around and what little on lamp test I been able to find is to use a diode between the LED and lamp test buss so that power doesn't feed back into the lamp test buss and go places it shouldn't. The question is should I put a similar diode between the Arduino output pin and the LED, so that lamp test buss power doesn't feed back into it? The lamp test buss will be +5V just like the Arduino output. It will be a separate power supply that can deliver enough current to run all the LEDs at once without getting unhappy.

Anyone with lamp test experience that can enlighten me?


texts:
I'm trying to produce a PWM signal for an ESC (electronic speed controller) in a Raspberry PI.

According to my logic analyser, the signal is fine.

I can use the signal to drive a servo, so I'm happy that the signal is good.

When I feed this signal into the ESC, the motors do nothing, until the pulse width is increased from 1.5ms (neutral) to 1.57, when the motor runs fast.  Increasing the pulse width further makes the motor run ever faster.

Changing the pulse width to values less than 1.5ms does not cause the motor to run backwards.

Should an ESC be correctly driver by signals which correctly drive a servo, or is my understanding faulty?


texts:
I am trying to switch a pair of 12v relays with approx 750r coils using a circuit and pre-fabricated pcb that I was given. The idea is that one relay is on when the other is off. The control comes from a signal from an arduino nano. Unfortunately it doesn't seem to like working. I have one relay that it works fine with but another that it doesn't (replacing one with the other in the same position of the circuit). I have tested the relays and they are fine. I'm guessing the transistor is not completely shutting off or something of that ilk (could it be due to the control signal from the arduino being 5v and the relays being 12v?) I have little knowledge of transistors. Can anyone suggest a solution, preferably one that I could try without having to get a fresh pcb made? Would using an npn and pnp mosfet solve my problem? Would I have to change any part of the circuit?

Many thanks!


texts:
Below is my calculations so far:

From this \$Z=110.777\ \Omega \$, with \$U=230\ V\$ gives \$\frac{U}{Z}=I=2.07623\ A\$.

However in the solutions the answer is \$2.4\ A\$. Where did I go wrong?
The answer also specifies the phase angle of \$48.5^\circ\$, but I am am uncertain as to how to find the find the phase angle of a parallel circuit. Is it the same as a series circuit where you simply take \$tan^{-1}\frac{\Im(Z)}{\Re(Z)}\$?


texts:
I am trying to collect data from analog sensors (temperature and relative humidity) with a PIC microcontroller (PIC18F14K50).
In order to save battery, the supply voltage of the sensors is turned ON when data have to be collected and turned OFF after. The supply voltage is controlled by the pin RB7 of the microcontroller.
The problem is that when the pin RB7 of the PIC goes high, the PIC is reseted, I have tried several software and hardware modifications but the problem remains. I am out of ideas now, may you have any suggestions ?

Note :

If RB7 is turned ON at the very beginning of the program and remains ON, there is no reset.
The 4MHz crystal and two 15pF capacitor connected to RA4 and RA5 are not shown here
I am using a switching voltage regulator to provide the +5V from +9V battery


texts: Why do so many IC's have a max temp range of 125C? Is it due to packaging material tolerances, ie the black plastic enclosures and/or the bonding epoxy that holds the die to the package and/or something else?


texts:
What are all the different types of lenses available for LEDs? I'm looking for a lens that would result in an effect similar to that of a 7-segment where a single LED creates a line segment of light.

Also, to make the question more general, and probably a little more useful to other people, how do you go about finding a lens for any LED application? I assume lenses are different based on size of led, surface mount/through-hole, viewing angle, desired diffusion etc.


texts:
simulate this circuit – Schematic created using CircuitLab

I found the above circuit at:

http://www.eleccircuit.com/a-lamp-flasher-circuit-using-transistors/

with a slight variant at:

https://hackaday.com/2016/08/19/books-you-should-read-basic-electronics/getting_started_in_electronics_04_flasher_circuit/
http://unitecnickie.blogspot.fi/2012_05_01_archive.html

and finally with the capacitor polarity swapped (and different R1 resistance, Q1/Q2 BJT type) at:

http://darsi.org/6-volt-inverter-circuit-diagram

According to my undersanding and the simulation I've done, the polarity of C1 should be reversed according to the last circuit version above. Otherwise C1 is reverse biased when Q2 is open pulling C1's minus pin close to 7V, while C1's positive pin is close to 0.7V. If this isn't true, could someone explain how the curcuit is supposed to work?

Also if the above is true and C1's polarity needs to be swapped, C1 would still be reverse biased when Q2 is closed, albeit at a smaller absolute voltage (~0.7V vs. ~6.3V). If so, is this 0.7V reverse bias acceptable considering that this is the normal way of operation, that is it's not an occasional event? If so, is there an ideal type of capacitor for this purpose?


texts: How do LCD displays with passive 3D polarize light?

texts: I understand how this works with projectors but I cant find any explanation for LCD displays. From what I understand 2 images are interlaced and displayed at the same time. How is it possible that 2 interlaced images are displayed at the same time and yet each are polarized differently?


texts: Differential amplifier with a current source

texts:
How to change the current source in the emitter here, so that the whole thing can be biased from a positive power supply (without the need for negative rail Vee) keeping all the other parameters more or less the same (like quiescent point, gain of 50 etc.)?

Here is the scheme:


texts: Test UART send and receive without a physical device

texts: I know how to transmit and receive using UART, but is there a way to test a simple send/receive app while only having openMSP430?


texts: Switching between backup battery and main power supply

texts:
I have this GPS which requires a back up battery to achieve warm start. I noticed in the schematics that V3.3 and VBAT is internally connected for this GPS board. Therefore, I connect a 3.3V battery to the JST in order to power the board. A microcontroller is used to read from the GPS. However the 3.3V pin on microcontroller is not connected to 3.3V pin on the GPS. They only share a common ground. The reason for this is that I want to use a switch to turn off the power to the microcontroller but leave GPS running in low power mode(off the battery). However, When I turned off the power supply to the microcontroller, the LED (attached to 3.3V of the microcontroller) was flickering weakly. As soon as I unplugged the battery on the GPS, the LED went off.

I am suspecting that the battery is supplying power to the LED but how is that possible? The LED only shares the ground of the battery.

There are couple 0.1uF caps between the 3.3V and GND on the microcontroller side. Also, it uses UART(TTL) to communicate with the GPS.


texts: What's the maximum possible power output of this RF CATV amp?

texts:
please tell me what is the maximum possible output wattage that this RF CATV distribution amp (see below for specifications) would likely output with maximum possible input before damage?  ~13 mW is only for the amplification of the original signal, correct, but what would the absolute power in watts for all output irrespective of frequency (inclusive of all harmonics and distortions). Basically, from the 20W power consumption what is the maximum it could put out in Watts? could it output 3W or maybe 4W possibly? irrespective of usefulness of the signal. This is more of a power efficiency question, that is, from 20W power consumption what can it turn into RF and what will it turn to heat loss in watts?
Thank you so much,
amp specifications:
Input Frequency Range: 40 ~ 860 MHz
Output Max Level: 60 dBmV
Gain: 50 dB maximum
Gain Control Range: 0 ~ -18 dB adjustable
Tilt Control Range: 0 ~ -16 dB adjustable
Noise Figure: 7 dB
Flatness: +/- 2 dB
Input Return Loss: >13dB
Output Return Loss: >14dB
Input/ Output Impedance: 75 ohm
Input/ Output Test Port: - 20 dB
Dimension: 498mm (W) x 360mm (D) x 280mm (H)
Connectors: All F type female connectors
Internal AC Fuse: 1 Amp
Operating Temperature: 0 ~ 50 degree C
Power Supply: AC 110V +-10%
Power Consumption: 20W


texts: What signals can be probed with an oscilloscope on an Arduino board?

texts:
I got my hands on 35 MHz analog oscilloscope. I'm trying to learn how to use it. Is there something that can be seen with a scope like this on an Ardiuno board? Clock signal maybe?

The board I'm using: http://arduino.cc/en/Main/arduinoBoardDuemilanove


texts: Choose impedance value of ferrite beads at any frequency

texts:
For example, in my PCB I want to use an SMPS IC but Vout will have noise.
The SMPS works with 2.5 Mhz. What should be the impedance value? How can I choose this value?


texts: Quantitative analysis of capacitive pickup of 60 Hz by an oscilloscope probe

texts:
I was recently looking at a couple of Q&A's on this site for a description of capacitive pickup of 60 Hz by an oscilloscope probe:

My scope detects a 50Hz signal when the probe is not connected to a circuit, is this normal?
50 hertz sine wave in oscilloscope when I touch it

I wanted to do a quantitative analysis of this, so I made the following model:

V is 110 V. V1 is the voltage measured by the scope. Z2 is the capacitive impedance of the coupling of the probe to the power lines. For example, if I'm touching the probe, then this is coming from the capacitor consisting of my body as one plate and the wiring inside the wall as the other. Z1 is the impedance of the probe. I take Z2 to be made out of a capacitance C=1 pF, while Z1 is a resistor R=10 MΩ in parallel with a 10 pF capacitance.

So if I analyze this as a voltage divider, I get V1/V=1/(1+Z2/Z1)≈Z1/Z2. At 60 Hz, the probe's impedance comes out to be almost purely its resistance R, so V1=iωRCV, or ~400 mV, which is the right order of magnitude compared to what I observe.

The reason I'm posting this as a question is that I got into a discussion in comments where we don't seem to be agreeing on the analysis, and it doesn't seem like the kind of thing that is going to be easy to clarify within a comment thread.

In this answer, wbeaty says:

  You're seeing a capacitive divider effect. One capacitor is within the scope probe and essentially is connected from the tip to the scope ground. The other much smaller capacitance is across empty space: from the probe tip to any distant 220vac wires in the walls. The empty space around the probe is the dielectric of this capacitor.

In a comment, I said:

  I could be wrong, but it seems to me that this is not really a capacitive divider. The scope probe acts like a 1 Mohm resistor in parallel with, say, a 20 pF capacitor. So at 60 Hz, the probe is acting like a resistor, not a capacitor.

Wbeaty replied in a comment:

  The Thevenin Equiv of the capacitive divider is 20pF in series with distant 220VAC source, all in parallel with 10Megs as you say ...AS WELL AS THE DIVIDER EFFECT. Perform calcs for three components. Suppose there is 0.01pF between the distant 220VAC line and the probe tip. That gives a 1/2000 divider effect, in addition to a highpass-filter attenuation of 1:15.9 at 50Hz. (In other words, what's the Thevenin equiv. for a capacitive divider using 0.01pF and 20pF? Then place 10Meg on its output, to create a hipass.) Apply 220VAC, and the scope w/floating probe will measure 6.9mV

I don't understand this comment. Can anyone clarify whether one of us is the right and the other person is wrong? Are we using different models, or the same model? I can't tell from wbeaty's verbal description whether he has in mind the same schematic I do.


texts: How can I generate a logic pulse from a broken IR beam?

texts:
I would like to trigger a [7]555 timer when a phototransistor stops receiving light from an IR led, more precisely when the (expected to be smallish) signal from the light-sensitive voltage divider, consisting of a phototransistor and a resistor, changes quickly. How should I wire the timer? I expect if I decouple the light sensor from the timer with a capacitor I might be able to get a sufficient voltage swing to trigger the timer from a small but quick change in the signal?

I would like to implement a version of the LED staircase. The project idea is to build a number of as-cheap-as-possible photodetector-triggered lamps on one side of a 3-foot gap opposite IR LED throwies on the other. When someone passes by they break the beam and trigger an entertaining trail of lights that slowly turn off, one by one, a couple of seconds later.

I was overthinking the problem. After some experimentation it appears all I need is a photodarlington (a phototransistor by itself is not sensitive enough) in series with a resistor. This forms a voltage divider with a usable signal. If a potentially long low pulse is a problem then merely decouple the photodarlington from the logic with a capacitor differentiator.


texts: Tool for measuring the frequency of a crystal oscillator

texts:
I am building a digital clock from sequential logic. I’m using a 32.768kHz crystal with a CD4060 IC.

I’m looking for a tool to measure the output frequency. I currently have it hooked up to an LED and it’s blinking somewhat irregularly.

Could a rough estimate also be read using a basic multimeter with a Hz function? I have a klein MM400. Would an oscilloscope be a good choice?

Edit: If anyone else is confused about how to select resistors and caps for these circuits I found this guide on CMOS oscillators
http://www.ti.com/lit/ds/symlink/cd4060b.pdf


texts: L6491 half bridge gatedriver is destroyed regularly

texts:
I'm trying to build a power supply - combined  step-down converter and the inverter using only a single H bridge and power LC member (C91, C92 = 2 pieces of 1.5uF foil capacitor in paralel and coil 1,2mH connected between ST1, ST2). I have problem with L6491 - bootstrap half bridge gatedriver. When I turn on L64941 for the first time, everything works. After the second or third turn on, the L6491 circuit is regularly destroyed and act as short circuit on 12V rail.  I designed this power supply for 300V input voltage, 20kHz switching frequency, 8,4 A output current with 1,2A ripple. This power supply feds 24 Ohm power resistor. L6491 is driven with PWM signal to create AC output 50hz trapezium signal (almost rectangle with 1ms rising edge). At first I tried to power my supply from 120V supply - it didn t work succefully and L6491 was destroyed. I also tried to bring 120V supply first and after I turned PWM signal a nd L6491 was destroyed. I also tried reverse order (pwm first and after a bring 120V supply) and L6491 was destroyed. All STP24N65M2 power mosfet (16A Id) in H bridge with 3.2 ohm gate rezistor survived. These 3.2ohm gate rezitors limits current to 3.5A with 11V rail. (L6491 is 4A gatedriver).

I suspect that the cause of the problem could be internal comparator (pin CP +, CP-) in 15A (maximum) overcurrent protection. Pin ~SD are connected with external pull up to 5V rail. When overcuurent is acticve, it should set logical 0 on ~SD pin. SD pin is alwazs high, i can see only very short spikes to 0V (interference ? )

Especially when output AC voltage is changing polarity, I measured with oscilloscope short spikes of high-voltage (I do not know whether it is not only measured interference ) and the negative overshoot on 20 miliOhm current measurement sunts R58, R132. These spikes (filtered with RC elements R15, C25 and R16 C28) would probably have caused activation of 15A overcurrent protection and disconnects gatedriver from MOSFETs.

Has someone had a similar problem with high-side bootstrap gatedrivers? Can someone tell me whether these impulses could be the cause of repeated destruction L6491? Or does anyone have any idea what else could be causing destruction of L6491 or how to proceed? When I will receive a new gatedriver L6491 (i hope this week), I will try to disconnect the comparator.

Detail: +DC_menic is input pin for max 300V DV voltage of my power supply.
ac1_MENIC AND ac2_MENIc is output for AC voltage from my power supply.
Pins ST3 and ST4 are interconnected and intended for future improvemnets.

Thanks for answer.


texts: How can I 'stretch' a signal in time using analog components?

texts:
How can a signal (e.g. an analog radio signal) be 'stretched' in time, so that the frequency is halved and the signal takes twice as much time? It's straightforward to do in a computer, but can it be done with analog components?

The transform I'm looking for is the same as recording an audio tape and then playing it at half the speed, so translating an input signal of for example

to

(This is different from what a heterodyne radio receiver does: it shifts a signal from a high to a lower frequency, but the signal still takes up the same amount of time.)

Recording and reading back at a slower speed would be one way to do this, but that would require slow mechanical components and not be able to deal with faster signals.

Background: I'm not building anything for which I need this, but I'm wondering if something like time division multiplexing could work in the pre-digital age or what it would take to create it. That is also why a method like recording to tape and slowed down playback would not work. If the multiplexed pieces of signal are short, the mechanical systems of a tape would not be able to keep up.

Edit The relation with time division multiplexing: I was thinking that tdm could be implemented with such a technique. Take two continuous signals, split them up into (say) microsecond intervals, squeeze each microsecond into half a microsecond (increasing the frequency), then interleave the squeezed segments of signal from both streams. To demodulate, reverse the process by stretching the odd or even intervals.


texts: Can all USB Type-C to Type-C cables themselves handle 100 W?

texts:
I am designing a machine and trying to make it look aesthetically pleasing.

Could I use off the shelf USB Type-C to Type-C cables to handle both power deliver and encoder data to/from a motor?

The DC motor is about 80W (@24 V) and uses 2 leads for power and 8 for the encoder. Could I technically use just one USB type cable to achieve this? I would not use the type-c connector, just the cable. The encoder has differential wires so hoping interference would not be an issue.

I understand that passive type-c cables are rated for only 3A but is that limitation due to the cable or the connectors and electronics in them?


texts:
I'm trying to write my first program to ATmega16A but I have an error:

  avrdude: AVR Part "atmega16a" not found.

But actually I've changed the chip with a similar ATmega16A and I'm sure that the chip is powered by measuring the voltage on the IC GND and Vcc pins; power is driven from the AVR pocket prog (I bought one a programmer like this one) and I'm trying to apply what is described in this video. The only difference that I'm using ATmega16A; is there any solution for such thing?

#include<avr/io.h>

int main(void)
{
   DDRB = 0b00000001;
   PORTB = 0b00000001;
   while(1)
   {
   }

   return 0 ;
}


texts:
I am trying to follow this guide to make a curve tracer with an ardunio: http://www.instructables.com/id/Arduino-BiCMOS-Curve-Tracer/

If I use this these op amps: http://www.ti.com/lit/ds/symlink/opa2341.pdf with the 5v supply will it still work? Also If I wanted to supply the transistor 12 volts how would I do that, couldn't I supply that to the op amps then on the inputs to the ardunio step it down to 5v?


texts: Controlling multiple 4066 from single output

texts:
I'm working on a circuit where I have two 74HC595 in parrallel. (2 serial to parrallel 8bit shift register with latch)

The outputs of the registers are connected to 2 40174 (D type flip flop)
So that allow me to keep the signal up or low until I ask the flip flop to update, even if the register value change and give me an extra control on when I want to apply the changes from the registers.

The flip flops outputs are connected to 4066 switchs. They allow me to "multiplex" 12 data signals.

My question is, can I use a single 40174 pin to control multiple 4066 switchs ?
Do I need to do something special ? (resistor ? capacitor ?) Or can I just wire them as-is ?

40174 Datasheet : http://www.ti.com/lit/ds/symlink/cd40174b.pdf

4066 Datasheet : http://www.ti.com/lit/ds/symlink/cd4066b.pdf


texts: Is this transformer-less power supply a good idea?

texts:
This is based on a design I found somewhere , I just wanted to know whether this is a good idea ,I intend to use this to power a microcontroller  and a 70 ohm 5 V relay . The cap c1 limits the current to about 200 mA , well below the 500 mA rating of my zener diode  . Without the zener diode , it looks like there would be about 7 volts across r1 which the zener should regulate . Ripples might be a problem though but I don't think it should affect switching that much , I'll also add a flyback diode to this .

Also , I get it that no insulation is a bad idea in general but I need this to be cheap and small .  If anyone has got any better idea , I'll be happy to hear  .

edit: C1 should be 3 uF


texts:
I'm looking at this verilog code and it asks me to do a state transition table

This is the answer, but it's using x=a and z=b and q=y.

the thing i don't understand is why in the code does it say assign q = state 1 or state 3, but in the transition table shouldn't it be y=1 in state 1 and 3? they have y=1 in state 1 and 2.


texts: Can I get constant current at the output of a buck convertor (to drive a LED)?

texts: I want to drive a LED with a buck converter circuit as shown in the schematic below. In order to keep the circuit simple, the system will run open-loop (i.e.; there won't be any voltage or current feed-back). Is it possible to set the LED current to a fixed value by means of calculating the appropriate \$D\$ (duty cycle) value? Or, in this circuit model, will the LED current theoretically approach to infinity because of lack of a resistive element in the path?


texts: different current readings with a multimeter between the 200 mA and the 10 A slots

texts:
I have a cheap multimeter, which gives me different readings between the two inputs. I would like to set 100 mA using a potentiometer in a circuit, which runs from two AA batteries. If I measure the circuit using the standard slot which works up to 200 mA, it shows about 80-90 mA. In the same circuit, if I plug the cable into the 10 A slot, and switch the multimeter to the 10 A mode, it shows 0.11 A.

Could you tell me why is it happening and how should I know that:

is my multimeter actually modifying
the current, or just showing it?
if not, then which measurement is the
correct?

As a small question: if I buy a new multimeter, what should I look for if I want to buy a better one? Should I buy one from a known brand? Is there any way to identify the ones I should avoid?

Update:
I think I should tell you what is my circuit:
2xAA batteries ---- 10 Ohm ----- IR LED (specified at 1.35V/100mA) --- multimeter ---- batteries

Thank you for all the detailed answers! Based on markrages' answer, I think in my case the multimeter is indeed modifying the current, because

without the multimeter its 10 Ohms
with the multimeter in 10 A mode its 10.1 Ohms in total.
with the multimeter in 100 mA mode its 12.5 Ohms in total.

Which would prove the fact why am I seeing 80-90 mA vs. 110 mA in the two modes, as thats the same 25% difference as the difference in resistance between 2. and 3.

Even more extreme was when I tried to run the 1.35V LED from a single AA battery. In that case I used a 1 Ohm resistor, and the two readings in the multimeter were 35 mA vs. 100 mA. Now I understand why, because the multimeter + 1 Ohm acted as a 3.5 Ohm resistor.


texts:
We are using BCM5482SA2KFBG PHY for ethernet link in SGMII mode by selecting INTSEL = 2'b10. The PHY was supposed to establish a link upon power up using Autonegotitation without any management configuration. PHY auto-negotiates to 10Mbps half duplex, though the PC and the PHY are capable of 1Gbps. The same 2 PHYs establish 1Gbps link with each other. Is there any other setting that is supposed to be done??

This is how we have connected the interfaces as shown in the schematic.

Test cases:

In this test, 2 different Broadcom PHYs in different boards(identical boards but not in the same board). The PHYs link up at 1Gbps (Autonegotiation - Autonegotiation done bit is high). We even created data traffic from one board and the data was received correctly in the other board.

Test 2: This is what we aren't able to understand. The PHY does not connect to PC most of the times. We have to disable the SGMII interface for the PHY to link-up with PC (at 10Mbps with Autonegotiation). How does the SGMII interface affect the working of PHY ??

Test 3: We have another board with Marvell PHY which links correctly (1Gbps - Autonegotiation). Same PC, same ethernet.


texts: How to add items to Schematic and BOM without footprints in the PCB in Altium

texts:
As part of the documentation for an Electronics project generated in Altium designer 17, I would like to add part number for items the project need, but are not part of the PCB.

For example in the schematic and PCB i have added :
Molex Mini Jr PCB mount Receptacle , However i am asked to include the mating Plug, Crimp and wire which is not a part of the pcb, but a part of the whole assembly.

1. What is the Standard (and neat) way of doing this kind of documentation?

2. Is it possible to add these parts in the schematic but make altium understand they don't have footprint ?


texts:
I'm using a 4DSystem 5" display with Arduino MEGA 2560.
Normally Arduino is powered through a wall power supply but, in some conditions, I need to power the Arduino + LCD with batteries (for not more than 10/15 minutes).
I've tried with a series of two 320mAh LiPo cells (7.4V nominal voltage - max discharge current 640 mAh) but after only 2/3 minutes the display turns off.

From the data sheet, the display consumption should be 440 mAh so, theoretically, with a 320 mAh batteries the display should stay on for 40 mins.
I understand 40 mins is not realistic but 2/3 mins is very little time.

Can anyone help me in solving this problem?


texts:
I've been trying to interface an i2c Oled display on pic18f26j50 microcontroller but i can't get it to work.

I'm using mikroC pro for pic.

#include "ssd1306.h"
#include "font.h"
#include "bitmap.h"

void main() {

 ANCON0 = 0x1F;
 ANCON1 = 0x1F;

 SSPSTAT=0x80;
 SSPADD=0x18;                                     //100khz baud rate
 SSPCON1=0x28;                                    // Master mode in I2c.
 SSPCON2=0x00;
 TRISB4_bit=1;
 TRISB5_bit=1;

 I2C1_Init(100000);

 Oled_Init();
 Oled_Fillscreen(0x00);
 Oled_Image(image,7,40,0,2);
}

I've used the exact same code(with obvious register value changes) on a pic18f2550... and it works like a charm....

as a last resort i've changed all of the code to work with software I2C... it works but its very slow. So obviously problem is not with the display but with the microcontroller code.

Can anyone point me to the right direction?

Oled_Init() consists of the following code.

void Oled_Init(void){
TRIS_RES = 0;
OLED_RES = 0;
Oled_Command(0xAE);                     // Set Display OFF
Oled_Command(0x81); Oled_Command(0xCF); // Set Contrast Control
Oled_Command(0xA4);                     // Entire Display ON
Oled_Command(0xA6);                     // Set Normal

Oled_Command(0x20); Oled_Command(0x02); // Set Memory Addressing Mode
Oled_Command(0x00);                     // Set Lower Column
Oled_Command(0x10);                     // Set Higher Column
Oled_Command(0xB0);                     // Set Page Start

Oled_Command(0x40);                     // Set Display Start Line
Oled_Command(0xA1);                     // Set Segment Re-map
Oled_Command(0xA8); Oled_Command(0x3F); // Set Multiplex Ratio
Oled_Command(0xC8);                     // Set COM Output
Oled_Command(0xD3); Oled_Command(0x00); // Set Display Offset
Oled_Command(0xDA); Oled_Command(0x12); // Set COM Pins Hardware Configuration

Oled_Command(0xD5); Oled_Command(0x80); // Set Display Clock
Oled_Command(0xD9); Oled_Command(0xF1); // Set Pre-charge Period
Oled_Command(0xDB); Oled_Command(0x40); // Set VCOMH Deselect Level
Oled_Command(0x8D); Oled_Command(0x14); // Charge Pump Setting

Oled_Command(0xAF);                     // Set Display ON
Oled_FillScreen(0x00);                  // Clear screen
}

and Oled_Command() function

void Oled_Command(uchar cmd){
I2C1_Start();
I2C1_Wr(OLED_12C_ADDRESS);
I2C1_Wr(0x00);  // Co = 0, D/C = 0
I2C1_Wr(cmd);
I2C1_Stop();
}


texts: Ground loop noise goes away when heater comes on

texts:
I have a ground loop or something in a stereo wiring. I have 3 stereo's connected all with the same inputs(fanout).

One stereo several feet away from the other two has an annoying amount of hum. (sounds like outside crickets)

What is very odd is that when a small heater comes on the noise on the stereo completely goes away(along with the lights dimming slightly). I'm sure there is some noise but the high frequency buzz goes away.

How could a heater, which I think is even on an alternate circuit, cause the stereo to stop humming? One would think it would be the opposite problem?

I guess the voltage lag might have something to do with it.

As a extra issue, anyone know of a quick way to kill ground loops easily? I don't want to have to buy some isolation boxes as they have gotten extremely expensive(100$+ for stereo). I think I do have some audio transformers that I might roll my own but it would be nice to find the issue. The one stereo isn't ground but all 3 are connected star(plugged into the same outlet). I'm thinking though I might have a bad wire somewhere.


texts: Using cellphone batteries to build a big power bank

texts: I'm working on a simple project where I'll purchase 8 rechargeable phone batteries, such as these. I think the right way to hook them up if I want to double the voltage is to hook 4 in parallel, doing the same with the other 4, and then hooking these two groups in series. What I'm wondering is how will I be able to charge them. Has anyone ever worked on a project like this and/or done something similar? What's my best option to charge them?


texts: Can I plug in too many LEDs (i.e. 26) on Arduino UNO?

texts:
So, I know Ohm's Law and that Arduino UNO R3 pins (digital 2 to 13) have a rated maximum of 40 mA, although it's better to consider that they have a maximum of 20 mA for safety reasons. If I put 2 LEDs (say red ones which have the lowest voltage of 1.8 V) with a 330 Ohm resistance to each one in parallel, meaning that (from Ohm's law) each LED needs 9,96 mA current.

mA = [ (supply voltage - LED voltage) / R] * 1000   --> mA = [ (5 V - 1,8 V) / 330 Ohm] * 1000 = 9,96 mA

That means that both LEDs draw 19,92 mA current from an individual pin (correct me if I made any mistakes with calculations or prallel and series connections). So, can I plug a total of 26 LEDs (2 to each individual pin of the 13 in total) without damaging my Arduino??? Otherwise, how can I plug in as many LEDs as possible?


texts:
I am building a 1-bit register using a DFF:

simulate this circuit – Schematic created using CircuitLab

The problem I have is that I think it should be saving whether D is high or low when the clock pulses and outputting that to Q.  How do I go about doing that?


texts:
Got few questions about the input/output pins of a crystal circuit.

As shown above, it's a common clock circuits.
My question is:
1. If we want to measure the waveform of the clock, which pin should we probe and why?
2. In the internal circuits inside the IC, which signal (IN or OUT) is used for the clock source of the internal circuits and why?

Thanks!


texts:
Currently when I work with microcontrollers, I use Microchip PICs and I'm happy enough with them. However, I decided to just take a look at ARM for a possible upcoming project. I wanted the pick the best (fastest at calculations at the cheap/low-power end) ARM. On the ARM website(here), the Cortex M0+ is listed at 2.46 CoreMark/MHz. I thought that CoreMark rating would apply to all microcontrollers with M0+ cores but on the Atmel SAM D20 page the microcontroller is listed as having 2.14 CoreMark/MHz. I read on some websites that the compiler affects the CoreMark score. I have also seen websites list an M0+ as having 1.77 CoreMark/MHz without talking about a compiler (element14). I also noticed ARM talks about the M0+ on a 40LP process while the element14 site talks about the ARM on a 90LP process. Unfortunately I am not knowledgeable about chip scale processor manufacturing.

So my questions are;

Do variants of the M0+ processor core exist? If yes, how do you spot which is which?
If programmed by assembly language, would all microcontrollers with ARM Coretex M0+ cores have the same CoreMark rating?

By the way, the micro I intend to use is of the MKL03Z family.
Any more info would be appreciated.

Thanks!


texts:
I am designing a circuit for the CHIP Microcomputer and I want to enable audio output using headphones OR a speaker. For clarification, when the user plugs in headphones, I want the speakers to be disabled. The CHIP has a headphone jack and provides access to the HPL, HPR and HPCOM signals, but doesn't appear to give me access to the Headphone detect signal from the headphone jack's detect switch.

How should I go about doing this? Can I use the HPL and HPR signals with an external amplifier for the speaker? If so, how do I set the SHUTDOWN signal to disable the speaker when headphones are inserted? Should I use an external audio codec? How do I know if an audio codec mutes the LINEOUT signals when the HPOUT signals are in use or how do I use the detect switch of a headphone jack to accomplish this?


texts: SMPS voltage drop in 230v ac to 5v dc flyback

texts:
I am building a SMPS circuit from a switching IC. This IC has feedback and enable pins for timing and current calculations respectively.

Transformer Data: (10 pin 1-5, 6-10)
primary: 1-3 - 60 turns, 3-2 25 turns (1-2 is total coil with 1.5 mH)
secondary: 6-10 - 7 turns
aux: 4-5 - 21 turns

When this circuit is operated in open mode (without load), it gives 5.2V (which is what i need). But when we start connecting load, voltage drops a little up to around 4.8V for some 1.4 A or 1.5 A need (10 ohm 10 W resisters in parallel to make load). If i take total parallel load up to 2.5 ohm, it should ideally give 2A at 5V. But happens is voltage start decreasing to 3 V as current raises to 2 A.

Why is that?

(I have tried using 2 1R0 or 2R2 instead of 2 1R5 for cs/enable but with no result, Also using 10 ohm in feedback after diode instead of 1 ohm)

IC: CT5503s

EDIT: Updated circuit Image


texts:
Hi all,

I found the following circuit on the internet and made it on the back of a business card as a fun project. The idea is that you ask a question, touch the naked wire, the lights shuffle and you end up with an answer highlighted by the one of the LED's. A poor mans magic 8 ball.

I've just got a couple of questions concerning the circuit:

What exactly is happening at pin 14? I know that pin 14 cycles through the output pins when the power changes high to low or vice versa, but how is touching the wire achieving this?
Why does the circuit only work when connected to actual ground or, oddly, when it's not connected to actual ground but near something electrical?
Finally, is there a way to get this circuit to work without connecting to ground? Or would I need to up the complexity and connect some sort of oscillator like a 555 timer and capacitors?

Thanks for the help.


texts: How do PID controllers effect time domain and frequency domain response

texts:
I have been asked to use sketches to show how varying P, I, and D settings effects an output response in both the time domain and the frequency domain.

I've have been taught how to, and done myself, graphs for varying the P, I, and D individually, however I'm unsure whether these were in the time domain or frequency domain. I used Wolfram Alpha to generate the graphs using a transfer function; an example of varying Kp can be seen below:

Can anyone please help me understand whether the plots I in created Wolfram Alpha were Time domain or Frequency domain plots, and the difference between the two types of plot?


texts: Are some CPUs implemented in standard cells and are others customized?

texts:
Explaining the question more, I see some die pictures which are implementing a Cortex-M0, with Bluetooth LE and so on, depending on the chip functionality, and are appearing like this (nRF51822):

While on older CPUs I cannot see much digital "fuzzy" logic implementation, like this (AMD386):

After googling a bit, it seems that today's ARM implementations are made with standard cells (creating the amorphous shapes on the die). So I can say that the "fuzzy" implementation on the first picture is the Cortex itself.

I understand that all the regular shapes may be memories and all the "hand-drawn" parts are analog. So I wonder, in the past were the analog designers to implement the digital parts under the guide of digital guys who were defining the architecture?

What am I missing?


texts: STM32F1 FreeRTOS osDelay (also vTaskDelay) make task stop running

texts:
I am using FreeRTOS with STM32F103C8T6 (code generated by CubeMX) and experiencing very strange behavior in my application while using osDelay or vTaskDelay functions.

Structure of my app is 3 tasks.
Task1: reads GPS data and provides location in queue.
Task2: reads location and sends it over uart to the outside system
Task3: reads GPIO pins and responds to that by changing some other pins

All works fine until I put osDelay value greater then 100ms inside, then task stops working.
As said if I put osDelay(100) all works without any issue.

I have checked stack overflow and there is none.
Currently monitoring for stackoverflow inside callback and high watermark with uxTaskGetStackHighWaterMark but none of them report anything.

Any hint ? What could be cause of such issue?


texts: Below given circuit, when given 24V DC supply for 30 seconds, the IN5408 diode shorts out at a rate of 1 in 5 cases

texts:
With circuit given below, when given 24V DC supply for 30 seconds, the IN5408 diode shorts out at a rate of 1 in 5 cases. This is an EMR circuit.
What could be the possible cause for this issue?


texts: which interface to use TBI, GMII or MII? (FPGA)

texts:
I am working with the SoC FPGA Smartfusion2 M2S010-MKR-KIT. It is intended to exchange some data between the SoC and the PC. For that reason, I aim to use Ethernet.

As far as I understood, in order to establish a proper communication using Ethernet, an interface TBI or GMII or MII should be programmed in the fabric in as means to communicate between the MAC and the Ethernet PHY.

Based on what should we decide which interface to use: TBI, GMII or MII?


texts: What is bulk diode?How will it affect the system?

texts:
i saw this explaination from a book,and it said this bulk regulation with switch can eliminate the bulk diodes.What is bulk diodes?where is it?it seems like bad thing,if there is a/some bulk diode,How will it affect the system?
Book from: https://books.google.com.tw/books?id=BfYkBAAAQBAJ&pg=PA97&lpg=PA97&dq=bulk+regulation+mos&source=bl&ots=U7dZRTe2T5&sig=fq2mSQ_9RGYh5kddbAvm9hH3N8g&hl=zh-TW&sa=X&ved=0ahUKEwi3mPyhyqbaAhWKy7wKHaskBRoQ6AEIJjAA#v=onepage&q&f=false


texts: PNP or NPN Transistor for this schematic?

texts:
I am quite new to electronics and hoping to build a voltage regulator using the schematic below. I will be using a 7806 regulator and a 7.4 Lipo battery (yes, the schematic is probably a little overkill for 6V regulation but never mind that). The transistor required is a TIP2955 which is a PNP transistor.

A website I came across says this about PNP transistors:

  Only when there is no current at the base will it turn on. And to ensure that no current enters the base, the base must be grounded (connected to ground). If any current goes into the base of a PNP transistor at all, the transistor will not conduct across from emitter to collector.

The schematic shows the PNP's base connected to positive, not ground. Will this schematic work and how? I'm rather confused as the preceding description seems to imply that it won't.

(source: zen.co.uk)


texts: Problem understanding transfer functions of second order filters

texts:
The transfer function of any second order filter can be found by analyzing the circuit using the Laplace transform.

For example the transfer function of a second order low pass passive RLC filter is :
\begin{equation}\frac{V_o}{V_i} = \frac{R}{s^2RLC+sL+R}
\end{equation}
For active filter there will be gain too.

But while doing simulation, I found the transfer functions are quite different. They are built using damping ratio and resonant frequency.

I can't understand how they have derived that transfer function. Can anyone explain me how can I get the transfer function of any filter just by taking resonant frequency and damping ratio into consideration?


texts:
Does anyone try to port ECB? I want to add additional device which will communicate with ECB via CAN bus but I can't find resources for that. I know that ECB is STM32F429 and here is some code (code for CAN communication) https://github.com/innfos/INNFOS_CAN_SDK_STM32. I need schematic of ECB and code for ethernet communication, does anybody try same or found up schematics or code for ethernet?
Does anyone worked with INNFOS devices (motors, hubs,..)? Any information is welcome


texts: How to find duty ratio of a PWM using input capture?

texts:
I have a controller PIC18F and it supports input capture peripheral. I understand it can be used to find the frequency of the incoming signal. How can the duty ratio of PWM can be obtained from the following details in data sheet? Is there any way of doing so?

> bit 3-0
 CCPxM<3:0>: CCPx Module Mode Select bits 0000 =
> Capture/Compare/PWM disabled (resets CCPx module) 0001 = Reserved 0010
> = Compare mode, toggle output on match (CCPxIF bit is set) 0011 = Reserved 0100 =
  Capture mode:
  every falling edge 0101 =
  Capture mode:
> every rising edge 0110 =
  Capture mode: every 4th rising edge 0111 =
> Capture mode: every 16th rising edge 1000 = Compare mode: initialize
> CCPx pin low; on compare match, force CCPx pin high (CCPxIF bit is
> set) 1001 = Compare mode: initialize CCPx pin high; on compare match,
> force CCPx pin low (CCPxIF bit is set) 1010 = Compare mode: generate
> software interrupt on compare match (CCPxIF bit is set, CCPx pin
> reflects I/O state) 1011 = Compare mode: Special Event Trigger; reset
> timer on CCPx match (CCPxIF bit is set) 11xx = PWM mode
>

  data sheet page 257. PIC18F46J53.

Is there any way to calculate the duty ratio? I trust from this only frequency can be obtained.


texts:
I have to generate 2 5-bit random numbers and add them using structural verilog and implement it on FPGA. I have to design LFSR with 5 D flip flops and the 5-bit pseudo random number is given by the outputs of the flip-flops. The 5 flip-flops are connected in serial and the 5th flip-flop is xor-ed with the first.

This is the code I have written so far. I am new to verilog and electrical concepts.

module dff (Q, D, Clock);
 output Q;
 input D;
 input reset;
 input Clock;

 reg Q;

 always @(posedge Clock)
 begin
   if (reset)
     Q = 1;
   else
     Q = D;
 end
endmodule

module DFF_LFSR() ;
 input D;
 input clk;
 input reset;
 output Q1, Q2, Q3, Q4, Q5;
 reg Q;

 dff DFF1(Q1^Q5, D, reset, clk);
 dff DFF2(Q2, Q1, reset, clk);
 dff DFF3(Q3, Q2, reset, clk);
 dff DFF4(Q4, Q3, reset, clk);
 dff DFF5(Q5, Q4, reset, clk);
endmodule


texts: How to connect input and output on Bistable Multivibrator

texts:
I built the circuit below on my breadboard. I've checked every connection and it doesn't work. The thing I didn't know how to do was connecting the output (a LED) and the input. (a button) I did something pretty random and, no surprise, it doesn't work. My question is how do I connect the input and output and can I do it with a button and a LED?

I will use this as a SR Flip-Flop, I found it can be used this way here.

Also, I've used 3.3k resistors instead of 3.9k resistors. Is that bad?


texts: Can I simply connect two AC/DC converters for increased current?

texts: There is this product, an AC/DC converter which is capable of outputting 5V at 600mA. I have a circuit which might draw as much as 1000mA. Can I simply use two of these converters together with the outputs connected in parallel? What do I need to be aware of?


texts: 3.3V digital signal as input to Arduino mega 2560

texts: I am using arduino mega 2560. I know it reads digital input signal of 5V as high but could any one tell me whether it takes 3.3V digital input as high or not? And what is the minimum value it guarantees to read as high?


texts: Why use aluminum wire in an (old) TV degaussing harness

texts:
I used to take TVs apart for fun (and parts, and learn.)
Some of the degaussing coils were beautiful -- nice, thick copper.  Others were made out of aluminum wire.  If I were engineering it, though, I would not have even thought of aluminum wire.
Can anybody shed some light on the thought process behind this? (You might relate how you have used aluminum wire in your product.)
I think "light" might sometimes be a reason (but probably not in the case for TVs with the big and heavy legacy CRTs).
I am after the engineering (or design) thought process here.
For those beginners or young ones who don't know, a degaussing coil is a coiled loop of wire, I'm guessing 40 to 75 turns (technically around an air core) held tightly together with electrical tape. The old cathode ray tubes would slowly get magnetized and exhibit a bit of "rainbow" or discoloration -- or if you had a child (like me) with magnets. ;-) The degaussing coil would remove the magnetization by a slowly decaying AC pulse.
Here are some sample pictures:
Example picture #1:

Example picture #2:

(I took everything apart because I wanted to learn how to make my own products some day.)


texts: Car battery (lead acid) discharges much, much faster than it charges?

texts:
Let's assume a lead acid car battery (12V, 50Ah, 250A output).
According to BatteryUniversity article BU-403:

The charge time is 12–16 hours and up to 36–48 hours for large stationary batteries. With higher charge currents and multi-stage charge methods, the charge time can be reduced to 8–10 hours; however, without full topping charge. Lead acid is sluggish and cannot be charged as quickly as other battery systems.

So the charging rate is no more than C/12. But car batteries (usually 6 cells) can discharge at often beyond 200A. 250A in my example. For a 50 Ah battery, this would mean discharging at a rate of 5C.
Does that mean, that a lead-acid battery can be discharged at least 60 times faster than it can be charged?
Or have I misunderstood something?


texts: Explain to me this solved part of exercise please?

texts:
We have the exercise :

The figure shows an op amp connected in the noninverting configuration. The op amp has an openloop gain μ, a differential input resistance Rid, and an output resistance ro. Recall that in our analysis of op-amp circuits in Chapter 2, we neglected the effects of Rid (assumed it to be infinite) and of ro (assumed it to be zero). Here we wish to use the feedback method to analyze the circuit taking both Rid and ro into
account. Find expressions for A, β, the closed-loop gain , the input resistance Rin and the output resistance Rout. Also find numerical values, given μ = 104, Rid = 100 kΩ, ro = 1 kΩ, RL = 2 kΩ, R1 = 1 kΩ, R2 = 1 MΩ, and Rs = 10 kΩ.

Now,this exercise is already solved in the book.Here it is

Here is the second figure

My question is : We know that Rs=10 KOhm.Rif=777 KOhm. Now,Rin=Rif-Rs=777-10=767 KOhm.As I have underlined in the second picture,why is Rin=739 kohm?


texts: Help understanding pins on a stepper motor driver

texts: Hi I need to controls some steppers for a work project. I found this driver in the back and can't find a data sheet online. My main question is what are the out pins for? The rest seems straightforward but correct me if I'm wrong. I'm controlling with a raspberry pi and I'll attach gpio to all the enable step and dir. Then I can send out pulses to step plus while enable + is high and changing direction+ will change the direction.


texts: How does the iso work in ccd\cmos array detectors

texts:
I'm curious to know how exactly does the iso sensitivity work in ccd's or cmos detectors that DSLR cameras have? I understand this is a amplification of the raw signal that each pixel has, but is in amplified before digitizing it or after? Can this be accessed manually with a developer kit of some sort (say I want iso 75 instead of 100)? can it be assigned to spesific pixels or pixel lines?

I'd appreciate your insights.


texts: I get everything about this picture perfectly clear, but what I don't understand is where is ROM located? Isn't ROM part of BIOS? Where do we sort BIOS in this memory organization?


texts: Where can I send my 0.005% 1 PPM tempco calibration resistors to find out their "true" value?

texts:
edit: putting this at the top because people keep answering questions I didn't ask:

Where can I get this done cheaply by a place that is hobbyist friendly? I don't even know where to look.

I imagine there are plenty of labs that do this kind of thing, but any that I can find via google do not disclose pricing and seem geared exclusively towards volume / B2B and are not hobbyist friendly.

Are there any cheap-ish labs that are friendly to the hobbyist where I could send my precision resistors to find out their true value down to the PPM range or better?  PPB would be ideal.  I'm using these to calibrate my 5.5 and 6.5 digit multimeters.

Bonus question: I'm interested in getting a calibration report on my precision 5v reference and a few capacitors / inductors as well so a place that can do all of that on the cheap would be ideal.

edit: additional notes based on clarifying questions people have asked:

I don't have a specific need aside from just being able to calibrate my bench multimeters up to 6.5 digits
It was recommended that I send a multimeter in for calibration instead of the resistors and use it as a transfer standard. Fair enough, but whether resistors or a meter, this is the heart of the question: where can I get this done cheaply by a place that is hobbyist friendly? I don't even know where to look.


texts:
simulate this circuit – Schematic created using CircuitLab

Forgive me if it's a basic question, but I am stuck with this. Is this the correct way to do it:

Do voltage division between R1 and R3 to find the voltage on R3. Then do voltage division again between R3 and Vc to find Vc. I know this is wrong because I am ignoring Vc in my first voltage divider. I can't use loop analysis because I don't have currents.

Any help finding Vc?


texts: How to measure high DC voltage by micro-controller with an integrated approach?

texts:
Goal is to measure DC voltages in the 100-500VDC range, safely with a microcontroller (e.g. Arduino)

The particular application is to monitor the voltage of a large Lithium series parallel battery array with a total nominal voltage of 188 VDC.  Measurement tolerance within a tenth of a volt is suitable for the intended application.

The purpose of the measurement is to utilize a microcontroller to automate the ON/OFF cycle of a battery charger via a low-voltage trigger relay.

I am looking for suggestions to a solution with measurement circuit simplicity and cost as considerations. This should be an integrated approach and avoid the need for discrete components such as transformers etc.

edit; it would be preferable to avoid using a traditional resistance based 'voltage divider' approach.
While this method is suitable for lower direct current situations, when dealing with high voltages things can get messy.
edit 2; added more language to clarify that, the solution should be integrated.


texts:
I want to make a 3.3V I/O (UART) interface between a FT232RL and AVR which operate at 3.3V
For this configuration responsible it's VCCIO and must be connected to 3.3V supply. But what about VCC? Can it connected at 3.3V supply line with VCCIO together?
As the datasheet say for VCCIO

  +1.8V to +5.25V supply for the UART Interface and CBUS group pins (2, 3, 6,7,8,9,10 11, 21, 22, 30,31,32). In USB bus powered designs
  connect this pin to 3V3OUT to drive out at +3.3V levels, or connect to
  VCC to drive out at +5V CMOS level. This pin can also be supplied with
  an external +1.8V to +2.8V supply in order to drive out at lower
  levels. It should be noted that in this case this supply should
  originate from the same source as the supply to VCC. This means that
  in bus powered designs a regulator which is supplied by the +5V on the
  USB bus should be used.

This which i mean that it is necessary to connect 3V3OUT to VCCIO for get 3.3V level interface?
I mean: I don't want to use 3V3OUT for VCCIO supply, i want to supply VCCIO pin externaly with 3.3V line.
And since i work the FTDI with internal oscillator VCC limited at 4V MINIMUM.
So, VCC must be connected at > 4V supply for normal operation. Am i true?


texts: Can a controller consist of a single zero? -Control systems

texts:
I'm trying to solve a problem in which the transfer function is this : $$G(s)=\frac{2}{s^2+\frac{s}{3}+1}$$
I'm asked to make a controller to move the poles so that they have damping rato ζ=1. Drawing the root locus I see that I need to add a zero so that the poles meet on the real axis( with a proper gain k). However, can a controller consist of a single zero? Meaning it will be of this form $$C(s)=k(s+p)$$ Because I read somewhere that the controller has to be causal and this is not.


texts:
How can one drive a stepper motor and control its speed using PWM from a microcontroller, since the stepper motor has more than two wires?

I just want a confirmation because I'm still confused.