texts: SOT23-5 Package vs SOT23-5L...Differences?

texts:
I'm designing a board which uses an LDO that comes in the SOT23-5 package. I have these parts in my possession, and on the part label (from Digikey) it displays that it is a SOT23-5, which makes sense. However, the part datasheet lists it as a SOT23-5 L, and I can't find any documentation on the difference between the "standard" package and the L suffix. I'm thinking that the L might be for low profile, like in LQFP packages, but for all I know, there isn't any difference, and it's just a manufacturer anomaly.

I'm only concerned because in Altium, it appears that there are two distinct footprints for the two. Is the "L" just the same size package with larger pads (in Altium), or is there some other minute difference between the two?

This is the part I'm using, and here is the datasheet.


texts:
I've been working on a Shielding Effectiveness system of 120dB according to IEEE299-2006 standards. The frequency range covered is 9kHz to 40GHz.

I've designed it using an analog signal generator, power amplifier, antennas (varying antennas for varying frequencies), pre amplifier and spectrum analyzer. I would like to know how to choose a cable for the system. I figured RG213 would be a good choice, however if it necessary to use it through out the system all the way from signal generator to spectrum analyzer.

Any ideas or suggestions would be good. In fact, guiding the way on how to select an appropriate cable that would meet the aim of 120dB for the frequency range of 9kHz to 40GHz would be much appreciated.


texts: Where should I connect power ground and control ground for a switched power regulator?

texts:
I'm trying to wrap my head around the concept of separating control grounds and power grounds for a switch mode power supply. I'm trying to use this TI chip in a design for regulating 3.3V, and I've kinda got stuck on the PCB layout recommendation (page 20 of the manual). I'm confused regarding how I should ground everything.

So I've got a couple questions:

Why must there exist a control ground and power ground? How are they different?
Since these grounds eventually have to be tied together, where should they be tied together?
How are ground loops relevant to this? It seems like when I try to understand ground loops, all the examples point to interfacing devices that contain different paths to ground (e.g. a receiving and transmitter connected via a 400 meter cable are grounded in two separate buildings). Relative to a long distance scenario, it seems like I'm only dealing with a single path to ground.


texts: Understanding driving a relay with a transistor

texts:
For an embedded application, I'd like to drive a relay using a transistor. At the moment I'm experimenting with a BC547, but only because I've still got some of them lying around.
The transistor I am using is rated at a max of 100mA continuous for the collector (or collector-emitter) current (if I exceed that it gets really hot and would eventually get destroyed, I guess). A typical relay that I'd probably use would have a coil resistance of e.g. 225 Ω and a nominal switching current of 53 mA at 12 V (I'd opt to use a 12 V relay, because I already have 3.3 V and 12 V in my circuit).
I'd guess that the nominal switching current simply equates to the voltage devided by the resistance, am I right? Hence I assume that it would be safe driving the relay with the transistor, because the current should not exceed the 53 mV, which is well below the maximum current the transistor can bear. Am I correct?
(I am aware that the description only holds for the static state when the relay is shut. I do know that there will be spikes induced by the coil when the relay switches, that have to be buffered using a diode.)


texts:
I am building a coil winding machine and I've already set up something that works. I used two nema17 stepper motors and tb6600 stepper driver cards. The problem is that motors are seems to overheating when I make them work at low speeds.  Internet says it is okay for steppers to overheat but they smell like burning circuit and vibrate too much. I am planning to use dc motors with encoders but I am not sure if I will be able to get accurate results, since I am winding really small coils. So, I have two questions;

1- Is there any way to use step motors without these problems? Something like changing steppers or drivers?

2- Can I use DC motor with encoders at high precision? If I want to turn it 200 step, can I achieve something close to 200 steps?


texts:
I have the following question regarding directional couplers. Below is the question.

My solution was to multiply the scattering matrices of both couplers as in the following

\begin{pmatrix}0&-\frac{i}{\sqrt{2}}&-\frac{1}{\sqrt{2}}&0\\ \:\:-\frac{i}{\sqrt{2}}&0&0&-\frac{1}{\sqrt{2}}\\ \:\:-\frac{1}{\sqrt{2}}&0&0&-\frac{i}{\sqrt{2}}\\ \:\:\:\:0&-\frac{1}{\sqrt{2}}&-\frac{i}{\sqrt{2}}&0\end{pmatrix}\begin{pmatrix}0&-\frac{i}{\sqrt{2}}&-\frac{1}{\sqrt{2}}&0\\ \:\:\:-\frac{i}{\sqrt{2}}&0&0&-\frac{1}{\sqrt{2}}\\ \:\:\:-\frac{1}{\sqrt{2}}&0&0&-\frac{i}{\sqrt{2}}\\ \:\:\:\:\:0&-\frac{1}{\sqrt{2}}&-\frac{i}{\sqrt{2}}&0\end{pmatrix}

Then I get the following matrix

\begin{pmatrix}0&0&0&i\\ \:0&0&i&0\\ \:0&i&0&0\\ \:i&0&0&0\end{pmatrix}

So does that mean that the resulting phase and amplitude for port 2' and 3' relative to port 1 are zero! Please help me with this as am really doubting that this is correct.


texts: are there any differences between referencing signal to VCC or GND planes?

texts:
In my first high-speed PCB design, I have an LPDDR3 RAM and my PCB have 6 layers with the below sequence:

1-Signal

2-GND_Plane

3-Signal

4-Signal

5-VCC_Plane

6-Signal

the region between the SOC and RAM is totally covered by VCC-DRAM in the VCC_Plane layer. Considering all requirements of impedance controlling of all layers is truly fulfilled, My questions are:

Could I route my tracks in any of signal layers? aren't there any differences between referencing my tracks to GND or VCC?
Is there any special signal group for example differential pairs or data groups that I should exactly reference them to GND(routing only in layer 1 and 3) or to VCC(routing only in layer 4 and 6)?
If there isn't any difference between them, what is the fact behind that which makes VCC plane and GND plane behave the same in referencing signals?


texts: cannot receive the right data of NONIN OEM III using PIC32

texts:
I am looking for a solution for my project. I am using PIC32MX270F256B from Microchip,nonin oem III module and UART. I have connected the serial out pin from nonin (pin number 12), to U2RX pin of PIC (pin number 22)
This circuit consists of accelerometer, nonin oem sensor, and temperature sensor. Only the nonin oem sensor did not function well. I use red led as a confirmation LED for U2RX receiver interrupt in programming, but the led does not light up which means the U2RX interrupt does not functioned well.

When I checked the data transmission at the terminal, 3 bytes of data [status, Heart Rate(HR), SPO2] were sent but in state of 00, 00, 00, which means the sensor could not read user's heart rate and SPO2 at all.

I have made the same circuit but using a different communication unit and different PIC before ( bluetooth instead of Xbee, and dsPIC33 instead of PIC32) and it works well. Thus, i do not think that there is any problem with the nonin oem sensor.

Could anyone recheck my schematic diagram? (i want to post other pictures like the real board diagram, the result that are shown at the terminal and some programming part here but I am allowed to post only one link) Those who wants to help and in need of more details/pictures/links, do drop your emails here and I will contact you privately later.


texts:
There was ambiguity in my initial question, and my overall circuit schematic was not provided which led to misunderstanding. I have rephrased my question below, hoping to make it more straightforward and providing more detail.

Basically, I need to discharge my filter supercapacitor bank for smoothing the high current output from a rectifier. After getting some comments it seems like the best way to do this would be to use a bleed resistor in parallel with the supercapacitors (please correct me if I’m wrong).

What is the best way to safely discharge the capacitors after the circuit has been turned off? If I use 2kΩ bleed resistors will the capacitors be discharged quickly enough or will they take a long time to discharge?

To be clear of the context the filter supercapacitor bank takes place in (also see diagram below):

The output from the full-wave rectifier can be adjusted (by changing the Variac setting) in the range of 0-200Amps and 0-10v (high current, low voltage)
The full-wave rectifier output divides into 10 parallel circuits each with one supercapacitor rated at 2.7v, 100F
The current given into one of these supercapacitors will therefore be between 0-20Amps (I will start at 0 and gradually increase, they may not be able to handle full 20Amps)
The voltage given into one of these supercaps will be below their rated voltage, probably around 2.5v
The idea behind this is that the supercaps will each smooth the DC waveform individually (at lower currents), and when the parallel circuits are recombined again there will be the high current output like before, except smoothed, not hitting the 0v at 120Hz
Note: I understand there are better ways to smooth a high current output (these options are too expensive and complicated, ex. using a three phase power supply)

This bank of supercapacitors needs to be discharged after the circuit is turned off. The current and equipment being used is of course VERY DANGEROUS, and I am well aware of that (which is why I am asking questions here and talking to other electricians).

The polywell, in short, is a device that uses external magnetic fields to confine electrons and deuterium ions for fusion reactions. To create the magnetic fields a high current power supply is needed. It is a novel fusion concept that is underfunded and has great potential for growth (and I’m definitely in a useful position to do useful experiments with it once my circuit is worked out- I have 3d printed a polywell frame, have vacuum chamber set up, have a thermionic emission set up, and have a high voltage pulsing power supply… @Russell McMahon).

The outputs of the entire circuit described above are ideally a somewhat smoothed DC waveform, high current up to 200A and low voltage ~ 2.5v. This output is going to be used alone for some experiments with the polywell. However, in other experiments, I am planning on lowering the output current for this circuit for the use of charging eight capacitors in parallel rated at 450v and 1500uF. This bank of capacitors will be used to provide a single pulse of very high current (~2.5kA) with a SCR and trigger pulse circuit (circuit provided below). Protection diodes will be used (they are placed backwards in parallel) for protecting these capacitors. In theory, this bank of caps does not need to be discharged like the filtering supercaps because it will be drained with the SCR pulse already. But to be extra safe, it is best to have a discharge circuit set up for these caps in case the SCR does not give the pulse we need or they are not fully discharged for some reason.

Relating back to my question above, what is the best way to safely discharge these capacitors (after the SCR discharges them initially)? And what is the best way to discharge the smoothing supercapacitors?


texts:
I want to connect a car antenna (FM radio) to a phone's jack sleeve to provide a good antenna signal to the phone (for its FM radio part).
As the car might add some supply DC to the antenna, I decided to isolate it with a 100nF series ceramic capacitor.
However it doesn't really meet my expectations: reception is better than without any cables in the jack socket, but I would like to see a similar reception, as with the original radio (if I plug the same antenna without the cap into it).
Did I make a mistake with the 100nF cap?
To be more exact: can I (is 100nF a good value) isolate DC current from an FM antenna wire which shall function as antenna in the 88.0-108.0MHz band with a series 100nF ceramic capacitor?


texts: How does Shift+Turn off disable the circuit of the calculator?

texts: How does it electronically work that in a basic Casio calculator, shift+ ac turns off calculator, is it a comparator that compares these two button states then triggers a transistor?


texts: Dealing with different voltage needs on a battery driven low-power board

texts:
I'm going to design a small wireless sensor box for a weather station project. This involves:

A sensor running at 3.0-3.6V (1mA)
A MCU, running at 3.0-5.5V
A 433MHz transmitter which takes about 6-12V. The higher the voltage, the wider the range. Maybe, 9V is enough. (unknown power consumption)

As the power consumption should be as low as possible, the MCU will sleep most of the time (consumes <1µA) and wake up from time to time (consumes in the order of mA or 10mA). It will power-on the sensor and the transmitter, do its job, and go to sleep again.

The point is how to power this. My ideas:

A high voltage battery directly powering the transmitter, and a regulator generating the MCU / Sensor power. This is cheap and simple, but I doubt it's a good idea: Is a regulator for this low currents efficient/feasible? Pro: works from a single battery.
A low voltage battery to power the MCU. But one needs to step-up this voltage for the transmitter, which makes the circuit more complex.
A high voltage and a low voltage battery to power MCU and transmitter separately. Could also be two low voltage batteries, and the transmitter uses both in series. But this needs a larger number of batteries...

So my question is: what's the best / standard way to power several parts with different voltage needs in a low-power device?


texts: FAN NOISE issue in triac phase angle dimming

texts:
I have successfully dimmed a light bulb using a triac & phase chopping method,but when I tried dimming an inductive load (for e.g. ceiling fan) then it made a humming noise at DIMMING, however it worked fine when full power is supplied (no dimming, ON state).I understand this is because of the sharp edge due to sudden voltage rising and this adds harmonics to the motor. It's been a week and I have tried many filter configuration with triac as I read online that using inductive choke would solve the problem but it doesn't seem so. Using an RC filter has so many drawback for my project so I cannot use RC filters as it decreases current to the load.

If someone can suggest me a better filter configuration or any other method to smooth that curve or reduce the noise I'll be grateful.

You can see, in waveform obtained after using inductor, the sharp edge becomes more sharp. I know that the curve that I am getting is a typical inductor behavior. To solve this, as seen in some circuits, a capacitor is used in parallel making it kind of an LC filter or Pi-filter. But even after adding the capacitor the sharpness of the rising stays the same.

Please suggest what values to be used to solve this problem.

(Waveforms) 1.waveform at triac firing/dimming(steep rise),
 2.waveform to be achieved after smoothing,
 3.waveform with inductor(150mH) in series configuration(not correct)


texts:
What tools would you use to easily simulate surge protections ? I am looking for a tool to simumate transient in zener diodes, PTC fuse, Gas Discharge Tube and the like.

I am a beginner in circuit simulation, and I have no clue on how to simulate things like a PCT fuse or a gas discharge tube properly. Let's say I have a very basic overvoltage protection consisting of a zener diode and a PTC fuse. I would like to properly simulate the behaviour of this circuit when using PCT fuse A or B. In other word, given the usually available technical characyeristics of a component, is there a software that has a good library or easily modifiable predefined components targeted at circuit protection elements ?

I could find a lot of simulator targeted at switching power suppy simulation, and I wonder if there is a software that would be ideally suited to overvoltage, esd and other circuit protection.


texts: The Piezoelectric Effect on Natural Quartz Crystals

texts:
Background
I have recently started doing a lot of research on the piezoelectric effect with the hopes of gaining a better understanding of the topic. When I can I like to do experiments on top of reading because it helps cement the knowledge I learned more effectively. The main topic I am looking into right now is quartz crystals. I have researched the molecular structure of quartz and what causes the piezoelectric effect but I am having a hard time finding out how the shape effects the frequency. I have mostly found resources on what makes small perfectly made factory quartz crystals oscillate but I have not been able to find any information on the processes of natural quartz.
The main thing I hope to gain from your knowledge is the understanding of how natural quartz crystals behave when a force or voltage is applied to them. I have a collection of quartz crystals ranging in sizes but I cant complete any successful tests with them on a larger scale.
Questions
Question 1- What effect would a force have on a cluster of natural quartz crystals? I ask this because the molecular structure would be intertwined so I wonder how it would be polarized when a force is applied and what kind of oscillation would be caused. Also how much would the efficiency drop by when compared to a perfect set of quartz crystals?
Question 2- When I have a single quartz crystal that is not uniform how can I determine its internal lattice structure to best predict its poles for any possible experiments I may conduct? I have been unable to read any voltage being created when a force is applied to any of my non uniformed crystals.
Question 3- I know that irregular quartz crystals with deformations will be less efficient but is it even possible to apply a force and read a return voltage with conventional tools and if so how would this best be done with that larger set of crystals.


texts:
Upon review of the design below, I noticed that the MOSFETS are in fact P-Channel and utilize a pull-up resistor. That orientation will only provide a current path when the signal from the WS2811 goes low. This means that the LEDs will be powered on while the output from WS2811 is low. Does that seem incorrect if I am trying to turn on the LEDs by sending pulses to WS2811? Maybe the outputs from the WS2811 do in fact go low when they receive Din.
Any input is appreciated!

Updated design:


texts: does the temperature of ambient air affect the power consumption of an incandescent light bulb

texts: With its filament held within a vacuum, does the temperature of ambient air surrounding the bulb affect the power consumption of an incandescent light bulb.


texts: Understanding a tuner Circuit with a reverse biased diode

texts:
This is a circuit extracted from the book "Electronic Circuits Analysis" by Phillip Cotler.

simulate this circuit – Schematic created using CircuitLab

The potentiometer R1 can be adjusted to control the polarization voltage across the "Si Capacitor". My question is how can this circuit work if the voltage E is connected to the positive input of the diode and not to the negative (direct polarization)?

I'd also like to ask how does C1 restrict the coil to put the DC tension in short circuit through Cv ?.


texts: get many different signals through one wire

texts:
I am new here. I want something done, and I strongly believe there is an IC for this job, but I don't know what it is called and I can't get the right words into google. What I want is to take many electrical signals and have them pulse in a single file line, sort of to speak. This is for sending information to a computer via USB, I would also like to know of a way to separate singles by time, like chop up a 1 second pulse into 10 bits, with the idea that I will be sending 10 signals per second.

I plan on hooking up a bunch of Potentiometers to a usb port on a computer. The Potentiometers will be attached to a skeleton figure and will tell me the rotation of a bone at any given time. I will be making the software reading the Potentiometers.


texts: Difference between regulator's tab and pin?

texts:
Take the classic LM1117 linear regulator http://cache.national.com/ds/LM/LM1117.pdf

Pin 2 is Vout.  The tab is also Vout.  From a component layout perspective, it would be nice if I could connect the output capacitor to the tab instead of the pin.

What is the functional difference between the tab and the pin?  Does one have less current carrying capability than the other?  Can I leave the pin floating and instead connect the tab to the output capacitor?  Must I hook the output capacitor to the pin?  Can I just short the pin to the tab?


texts: Internal Programmable ROM of CP2102 (USB to UART)

texts:
I am using CP2102 device (USB to UART) in my project. It has internal programmable ROM t0 configure product ID. I tried in there tool via USB and it works.
Now, I want to programming the ROM via my MCU. Has anyone tried this?

Thanks and regards,


texts:
I need to connect 15 ceiling fans. Each bay has 3 ceiling fans that will run of the same speed controller, so 5 controllers in total. They will be wired from a separate circuit from the DB box. Here's the schematic below that I drew up:

Since each fan pulls about 0.5 amps, that's about 7.5 amps total, so a 15-20 amps circuit breaker should be fine. For the fan controller though, i'm guessing I'll have to buy one that can control 3 fans, since the capacitors in the fan controller are gonna see roughly 1.5 amps, hence the voltage drop across them will change compared to when connected to a single fan ?


texts:
I am trying to create an electric tuner using a piezo (so it can be used to detect vibrations rather than a mic which is subject to ambient noise)

I have the schematic below using a voltage regulator to create 5v (5.09V is the closest I could get)

The battery then powers the ADC and the op-amp and the 10-bit data is sent to the SPI pins of the Raspberry pi.

I am attempting to create a 3.3V bias so the negative voltages generated by the piezo can be read. (3.3V is the simplest implementation as 3.3V is all ready to go)

I have recently changed the design because the 5V from the RPi was unstable and giving me erroneous result but I am still getting bad results from my current setup.

The code I use reads the pin and converts the data into it's correct voltage the data is then displayed as a graph and created as a .wav file (the .wav will be used when I can get the setup right to listen to the note played)

Here is the code:

import spidev
import time
import os
import matplotlib.pyplot as plt
import wave
import numpy as np
from scipy.fftpack import fft, ifft
from scipy.io.wavfile import write

spi = spidev.SpiDev()
spi.open(0,0)

def read_spi(channel):
    spidata = spi.xfer2([96,0])
    data = ((spidata[0] & 3) << 8) + spidata[1]
    return data

def ConvertVolts(data):
    volts = (data * 5.09) / float(1023)
    return volts

ADC_channel = 0
samples = []

print "Starting detection..."
start_time = time.time()
try:
    while(True):
        samples.append(ConvertVolts(read_spi(ADC_channel))
except KeyboardInterrupt:
    pass
readTime = time.time() - start_time
print "Detection complete."
print("%s seconds" % (readTime))
time_axis = range(1,len(samples)+1,1)
print "Generating graph..."
plt.plot(time_axis,samples)
npSamples = np.asarray(samples)
scaled = np.int16(npSamples/np.max(np.abs(npSamples))*32767)
write('audio.wav', int(len(samples)/readTime),scaled)
plt.show()

Using the code above I generate a graph which looks like this:

This is the results for just under 1 second of reading.

simulate this circuit – Schematic created using CircuitLab

Can anyone explain why I am not getting a constant 3.3V displayed on my table?

Thank you.

EDIT:

When I remove the op-amp and connect the ADC input to the positive rail (5.09V) I get a reading of 768 or 3.8 Volts. So the code must be slightly out. But I don't get why the 3.3V on the RPi is inconsistent unless I'm sinking too many milliamps and it's unstable.

EDIT2:
Updated the design. I have two 9V batteries and 2 LMT317. One generating 5.09V and one with 2.46V.
2.46V is connected to the input to the ADC and 5V is powering it. I'm still getting bad results fluctuating between 768, 256, 96 and 0. (3.82V, 1.27V, 0.47V and 0V, respectively)

Really don't understand at the moment.
Also, if CH0 is unplugged entirely it fluctuates between 0 and 256.

simulate this circuit


texts: How can I implement regenerative braking of a DC motor?

texts: I know that many electric cars are able to convert the momentum of the car into stored energy in batteries, rather than convert it to useless heat at the brake pads. How does this work? How can I implement it myself?


texts: Is a flyback supposed to have infinite resistance on the secondary (arc) coil?

texts: Previously, I was able to get nice arcs with the 555 timer and irfp450 MOSFETS. When they died out I thought it was just the FETS but when I went through the proper test procedure for the FETS, I noticed that they were OK. I was puzzled by this and I am now thinking I have a bad flyback. When I redid the whole circuit, I was able to make very TINY arcs (<2mm) and when I tried a ZVS, I got the same results. I then measured the primary and secondary coils with an ohm meter, and got strange results. The primary seemed o.k. with 1 ohm, but when I measured the secondary (where previously got arcs) , the ohms were at lest greater then 2 mega ohms (my meter goes up to 2M), and the only resistance i was picking up was my finger. Is this normal to have the arc coil (secondary) to have no resistance? Or is something wrong with my flyback, and what could've happened? All I know is I was running my arcs for 15 minutes straight before everything broke and I just want to confirm it is a bad flyback!


texts: Why is it bad to have an inductive load (context: dc-dc converter)?

texts:
In the book I'm studying from Power Electronics - Mohan he says:

  (...) has two drawbacks (1): In practice the load would be indictuve.
  Even with a resistive load, there would always be certain associated
  stray inductance (...)

This is in reference to a basic buck converter where for the sake of simplicty he explained the operation using a very basic circuit:

Then, he said what I just quoted. He said that an inductive load is a drawback. Not only here, but in previous chapters they speak contemptuously about inductive circuits in general. So, my question:  why is it so bad to have an inductive circuit or an inductive load in general (they can't be bad always, can they?)?


texts: Error in final launch sequence Failed for OpenOCD (Olimex) for ARM (STM32fxx)

texts:
I am using openOCD in eclipse for the arm STM32F10x series. After writing the whole code and  building everything without error in the program, I am going to debug it and I am getting an error after completion of 99% of the process. The following error is generated and I am not able to debug my program.

Error in final launch sequence
Failed to execute MI command:
-exec-run
Error message from debugger back end:
Error creating process


texts:
I am trying to build a PWM signal with 555 timer. I am following this website to build my circuit.

simulate this circuit – Schematic created using CircuitLab

I have placed my components in my breadboard as shown in the schematic I have placed above. I am trying to observe the intensity of my LED at different duty cycles. But I am not being able to find the correct resistor value for R1 to get the duty cycle of 25%.

Some maths I have done:

I fixed the value of R2 to be 330 Ohms. I have my capacitor rated 1 microfarads.

If T(on) is the on time of LED then: T(on)=0.693*C*(R1+R2).

If T(off) is the off time of LED then: T(off)=0.693*C*R2.

So, total time period of the signal = T(total)=0.693*C*(R1+2R2).

The duty cycle is now T(on)/T(total)=(R1+R2)/(R1+2R2).

Starting from the lower duty cycle, I wanted 25% duty cycle first. The calculation gives me the value of R1 to be negative. Note that I have the R2 value to be 330ohms.

What's the thing that I am missing?


texts: How do Circuit Simulators actually work?

texts:
I recently had the opportunity to play around with LiveWire, which is a circuit simulator and began wondering how exactly they computed the voltages across each component and the current going through each track of wire.

I have only been taught basic circuit analysis skills (such as Mesh analysis and Nodal analysis) so far, and I'm not entirely sure that they would be generic enough to implement in a 'fits-all' way within a circuit simulator.

As a programmer this has intrigued me and I'd love to see what techniques are commonly employed when building circuit simulators such as this one.

My apologies if this does not belong here, it was a choice between here and StackOverflow and I felt that although it is a software-development oriented question, the question is more applicable to this site and it's userbase.


texts: VHDL: Is alias only used to refer to subset of std_logic_vector?

texts: I have seen alias declared to control subset of a big std_logic_vector. What are other applications of it?


texts: What is the best battery topology for my inverter-charger application?

texts:
Background:

I have a Magnum Energy MSH3012RV 3kw inverter-charger that runs on 12VDC and I'd like to be able to discharge around 250 to 300 AH between recharges (from 120VAC input) without the batteries experiencing much more than 30% depth of discharge. Rates of discharge will be around 20-30A continuous with periodic short (~5 minute) bursts of up to 250-300A. Originally I had planned to purchase four 200AH/12VDC AGM batteries and put them in parallel, but upon further reading I've come to understand that batteries in parallel have a tendency to eat each other from charge oscillating back and forth between them due to slight differences in battery voltage. Now I'm looking at instead putting six 2V batteries in series.

Questions:

1) Is this inverter/battery topology sound? Is there a better way?

2) The particular batteries I am looking at are these. I need sealed/VRLA batteries for this application and my sense of things is that AGM batteries will serve me better than gel, but my understanding of battery technology is limited. Assuming my topology is good to go, are these batteries likely to be a good choice, or is there another type of battery or even a specific manufacturer I should  consider (or avoid)?


texts: What is the current draw during load on the LM1117 3.3v

texts:
I am looking at using the LM1117 3.3v voltage regulator.

I would like to determine the current draw to power the regulator's function, during output of something near 650mA.

All I can find is entries such as :

Quiescent current: 10mA

Is that my draw figure? Is there a better way to calculate it. As far as I understood, quiescent current was the draw under zero load. If this is the case, will this chip draw more current to output a higher 3.3v current? If yes, how do we know how much?


texts: How to drop the voltage slightly (~100mV) for a MCU mostly in deep sleep?

texts:
How to drop the voltage by a low value (let's say <150mV) without wasting current to supply a microcontroller that spend most of its time in deep sleep mode?

I'm working on a board with a microcontroller that will accept up to 3.6V as supply voltage but LiFePO4 and Li/SOCl2 can go slightly higher when fully charged (or during charge for LiFePO4). The microcontroller uses ~10μA during deep sleep and can use up to 500mA (mostly spikes) when active and transmitting over WiFi (ESP32).

I know that I can use an LDO with a low quiescent current but I am curious if there are better/cheaper alternatives. For example, I thought about using the drop voltage of a Schottky diode.


texts: Selecting low power mosfet for battery monitor

texts:
I'm trying to implement og test the results discussed in the linked JeeLab post in a low power battery powered device.
http://jeelabs.org/2013/05/18/zero-power-measurement-part-2/#comments

The post describes a method for monitoring the battery voltage through a voltage divider that can be switched off by a P-channel and a N-channel mosfet.
Similar solutions are discussed here:

Low Current Battery Monitor Detail Question

Low current battery monitoring

The question is how do I select an optimal N-channel og P-channel mosfet for this application? Which electrical parameters should I base the component selection on?
If anyone have experiance with this method and/or selection of components sharing would be appreciated.


texts: Preventing op-amp output fluctuation at power-off event

texts:
What methods exist to place the outputs of an op-amp in a fixed state when power is removed? I have a circuit that uses an LM324 to process an analog input signal. As shown below, the input signal changes state about 4 ms after the power-off event, but the op-amp is still responsive despite the decaying supply voltage (it's powered from a 12 V rail and will operate down to about 3 V). I'd like to eliminate this output blip but I'm not sure how to do it.

I've considered using a supervisor to monitor the supply line and shut off the op-amp after the voltage drops below a certain threshold, say 8 V, which would occur before the input signal begins to decay. However, adding another IC seems like a drastic measure when I'm thinking this could be solved with some sort of RC delay circuit. Is there a simpler way?

EDIT: Here is my schematic. It's based off an answer to one of my earlier questions. \$V_{ref}\$ is 5 V and \$V_{cc}\$ is 12 V. The circuit converts a 0-5 V input signal (\$V_{in}\$) from an APEM HF Series joystick to a 5-0-5 V "vee" shape. At power off, the joystick output decays down to 0 V, which results in the op-amp circuit trying to hit the 5 V rail.

EDIT #2: Schematic of the logic that's fed by the op-amps:


texts:
I'm new to verilog and HDL, so please be patient with me.

In a code, I have an input variable clk, two input 16 bit samples, that are stored into [31:16] ddc_out_sample and [15:0] ddc_out_sample and an input strobe called ddc_out_strobe.

What I want to do is take the 8 MSB bit of [31:16] ddc_out_sample and [15:0] ddc_out_sample, having a 16 bit sample instead of a 32 one. Then combine 4 of those samples to feed them directly to the output [31:0] bb_sample. The output strobe is bb_strobe.

I had thought of the following implementation to achieve this:

reg count = 0;

always @(posedge clk)
     i_msb <= ddc_chain_out[31:24]
     q_msb <= ddc_chain_out[15:8]
     assign bb_strobe = 1'b0;
     if(count % 4 == 3)
        assign bb_strobe = ddc_out_strobe;
     end
     count = count + 1;
end

I know that asynchronous conditions should be avoided, but I don't see how to implement this otherwise.

Any comments and thoughts will be appreciated.


texts: Problems with using 20Mhz crystal withPIC18f2420

texts:
I am using PIC18f2420 to generate PWM. I am using Timer 2 with 4MHZ crystal, which works perfectly by giving me PWM. I need to get 100KHZ of frequency for PWM, for which, 4MHZ crystal is not enough as it will reduce my resolution to an unacceptable level. I changed the 4MHZ crystal to 20MHZ without changing any of the configuration bits, hardware or program, as I do not know what do I have to change. Can you please give me advice what should I change? My crystal is connected to two 27pF capacitors, will they work fine for 20MHZ crystal too?

Current configiration bits:

#pragma config OSC = HS //HS oscillator
#pragma config PWRT = ON, BOREN = OFF //power-up timer on, brown-out detect off
#pragma config WDT = OFF //watchdog timer off
#pragma config LVP = OFF //low voltage programming off
#pragma config PBADEN = OFF //Configuration setting

Port B all digital I/O


texts: Controlling DC motors and servos with a single pca9685

texts:
I have a Raspberry Pi project (robot with wheels and servos) and I'd like to control both motors and servos at the same time.
I'm trying to use PCA9685 + L298N for driving the motors.

The problem I'm facing is that it seems like the PCA9685 has s single clock, so I can only set PWM frequency once for all pins.

So far my understanding is that if I want to drive DC motors with PWM I need to set PWM frequency to at least a couple of 100Hz, let's say 500Hz

However if I want to drive a servo (SG90) it needs the clock to be set to 50Hz

Does it mean that I can only use the board either for servos or DC motors?

Are there better approaches for driving DC motors from RPi?
I'd like to keep sound output while driving, so I don't want to use PWM pins from RPi directly :)
I'd like to keep CPU usage as low as possible, so also not sure if I should use software PWM for that.


texts: What is the best general purpose variable resistor in a battery discharge circuit (10V < Vbat < 50V)?

texts:
this is a very specific question and i'm unsure if this is the right place to ask.
I am constructing a battery discharge circuit.
The discharge circuit specifications:

To be able to discharge battery's (voltages ranging from 10V batterys to 50V batterys)
To be able to support a discharge current between close to 0A and 5A

Because of the wide range voltages and currents i'm having a hard time finding the right variable resistor element. The solution I've arrived to is using a transistor (with high power dissipating capabilities (which i can further enhance by attaching to a heat sink)) with a high precision DAC placed at the base/gate effectively giving me digital control of the respective resistance between the collector-emitter/drain-source.

I understand operating the transistor in this non-linear region can be difficult, however if i correctly apply the mathematics inside the PIC which controls the DAC via SPI, and if i take into account the voltage across the resistor, it may be possible to map the gate/base voltage to the resistance between the two terminals (collector-emitter/drain-source).

Circuit Diagram Attached.

Is this a good cost-effective method of solving this variable resistor element problem?
If so, i don't know enough about respective transistor families (BJT, MOSFET, JFET) to know which would be the best to use. Furthermore, temperature variation in the transistor could greatly change the desired resistance and i'm unsure how to tackle this.

Notes: regarding the circuit diagram attached:
- Q1 is the transistor (variable resistor element) controlled
  by a precision DAC at the base/gate respectively.
- R8 is a high side current shunt element
- V2 is the battery to be discharged (ranging from 10V - 50V)
- U16A is a non-inverting rail to rail single supply amplifier with the purpose of copying the voltage with attenuating it 10. The voltage follower (U17B) then copy's the signal with respect to a 5V power supply while ensuring U16A draws an insignificant amount of current.


texts: How to get a high precision sine wave not available from standard crystal?

texts:
I am considering for a RFID transmitter, which just send power with no data. However, my frequency is not standard 13.56MHz not 27.12MHz, it is 27.095MHz. Can I use the block diagram shown above? If yes, where can I get the 27.095MHz signal source?

I have two ideas now, first use a MCU and a PLL chip to derive the accurate frequency. Second, use the programmable crystal oscillator(which is also based on pll, with factory programmed) like SG8101 from epson. However, the output from SG8101 is a square wave, so I have to low pass it before it is send to amplify?


texts: How many functions can I put into an arduino uno?

texts: Is it realistic to put the following: GPS module, GSM module, SD card slot and about 4 analog sensors into Arduino uno? (have not yet goten an Arduino in my hands).


texts: Equivalent circuits in case of equipotential nodes

texts:
I have the following basic questions about circuit theory.

1) Consider a generic circuit. Suppose that, because of symmetry or other reasons, we conclude that two nodes A and B of it have the same potential with respect to GND (VA = VB). Are we authorized to put a short circuit between that node and analyze the circuit we get?

2) Suppose that, for instance because of symmetry, we conclude that no current flows on a certain resistor. For instance, no current flows on the central resistor of a Wheatston Bridge when all its 4 resistances are equal:

Since no current flows on RL, are we authorized to replace it with a short circuit, or with an open circuit, and then solve the resulting circuit?


texts: How to pick resistor values for voltage range with potentiometer

texts: How do I pick resistors for a 12v-30v boost circuit using an SDB628 IC; Vout= 0.6(1+R1/R2). I am using a 50k pot for R1. How do I get that 12v-30v output voltage range? To get 30V, my calculation of R2 is 1K; to get 12v, R1 has to be 19K, but since this pot can go down to 18K ohm, even 0 ohm, so many precision range of the pot is wasted. Then let me assume that the 50K pot is at its 0 ohm position, then I need to add another resistor to get 12V. My calculation is 19K for R0 to get 12V. (R0+R1)-(R2); but the problem is when the position of the pot went up to 50K, Vout will be much higher than 30V. doesn't work either way.


texts: ATmega ADC input channel analog vs digital power

texts:
The data sheet of the ATmega48A/PA/88A/PA/168A/PA/328/P states that ADC input channel 5 and 4 use digital power, while ADC input channels 3-0 use analog power.

Does this mean that ADC 5 and 4 use Vcc and ADC 3 to 0 use AVcc?

Are ADC 3 to 0 then less subject to digital noise than ADC 5 and 4?

And if Vcc and AVcc share the same power source (which according to Atmel AVR126 should be done via an LC network), does it still matter which ADC input channel is used?


texts: Is charger with USB C connector and 13V output in line with standards?

texts:
I have bought cordless rotary tool. The charger which is included in the package is equipped with USB-C connetor, and the charger has rated output at 13V @ 1.5A.
Is this "legal" according to USB specification? This does not seem to be a smart charge so I think it cannot vary it's output according to the downstream device preference.
Am I correct that this charger would damage an USB-C device (tablet, phone, earphones, ...) which would be expecting 5V and only then negotiate higher voltage according to USB-C PD standard?


texts: How would I find the transfer function of this circuit?

texts: I know that I can take the inductor and resistor and find the impedance from them in parallel. But what do I do with the resistor, R3? Do I need to do a nodal analysis and solve for the Vout? Or can I say that no current flows through R3 because the circuit is open, and then use just the R1 and L || R2 values in my calculation of Vout?


texts: RJ45 Split, one part Ethernet other part telephone.

texts:
I have a patch panel and some ports that allow me to patch telephones lines.

So, I use this patch panel to give a wired connection to some devices and I also use it to provide a telephone point.

The problem I have, I only have one socket at the location that I have our phone and I want the phone along with Ethernet to connect a Wireless Access Point eg :

I already have these :

And I do this

They work a treat and give me two network connections along one Structured cable. But they don't work for the landline.

I apologies if I am using all the wrong words, I work in IT and I understand a little networking, if the landline only uses a few cables I guess I could make something, but I would rather buy something.


texts: I have a STM32F427 micro controller with 2.5 V power supply. Some input signals are 3.3 V. Does it cause any damage on GPIO or can the STM32F427 tolerate 3.3 V logic?


texts:
https://www.hunker.com/12606720/how-to-remagnetize-an-electric-generator
Seems plausible (though I’m still skeptical) for a permanent magnet drill motor.  But is it true?
And if it is, would it also work for a motor in which the magnetism is produced by the power input?


texts: spice representation for mechanical problems

texts:
As a mechanical engineer, for my work, I need to compute some displacements which are represented as a summation of frequency dependent admittances on a structural system and I would like to use this summation representation in SPICE to find the input output behaviour of my system.

This looks like an extension of 2-port network theory(which I am reading about at the moment) to a system with N ports actually, I believe(since I do not have the proper background.).

I read that SPICE generates netlist for the circuits and these can be directly used for the simulations.

I was wondering if that is possible to generate, somehow, automatically the netlist of this N port system which is an approximation of the input output relation of the modelled structural system? I could make it for a two port system where there are really 2 inputs and 2 outputs already but my goal is to transfer my sum of admittances to an N port network representation where N could be an arbitrary number, 12 in this case, which represents the number of displacements and forces in a generic structural representation.

So my goal is to accomplish this for a 12 port network. But as the port numbers increase, the connections are becoming more complex. Is there a source that could guide me on this matter?


texts: Distributing power to varying resistance

texts:
Can a regulator be built to divide the output of  a DC power source to supply identical amperage, in the range of  1 to 5  Amps, to 16 individual conductive parts in an electrolytic solution

Said parts are connected to the system with varying contact resistance.  It will be required that voltage to each different location will be controlled to assure the amperage to each part is constant

The parts would be plated in an electrolytic solution.
The desired end result will be the delivery of the same amount of charge (number of coulombs) to each part.


texts:
The below image shows the circuit schematic:

simulate this circuit – Schematic created using CircuitLab

I wanted to check the turn off time for the mosfet switch varying the pulldown resistance.

resistance=2ohm
Resistance=100kohm

But in both cases there wasn't any noticeable difference in the turn of time . theoretically increasing the resistance should increase the time constant (RC) therefore increase the turn off time .

what do you guys think is happening here ?

Mosfet :IRF 1405PbF(sorry I couldn't upload the image showing the electrical characteristics of the mosfet)


texts: Change in transformer efficiency (leading power factor) with increasing load current

texts: Does efficiency increase or decrease when the load current increases (assuming copper losses equal iron losses along with a leading power factor load)?


texts: Is 12V or 240V more efficient for a domestic solar powered lighting circuit?

texts:
I'm about to buy a house with an existing solar system, with 12V batteries and a 240V inverter driving the mains and lighting.

I will be installing new smart lights throughout. My question is, should I stick with a conventional 240V lighting circuit, or is it more efficient to go for 12V lights, bypassing the inverter? So I guess it's the payoff between voltage drop on 12V circuits vs power loss through the inverter.

The house is on 3 levels with a 80m2 footprint.

The house has no mains supply, it's solely solar with a backup generator.


texts:
There are a lot of PCB trance impedance calculation tool available on internet, for example :
http://www.eeweb.com/toolbox/microstrip-impedance

Trace impedance can be calculated by entering parameters "Trace Thickness", "Substrate Height", "Trace Width",and "Substrate Dielectric", but not the length of the trace.

My questions :

Does the above calculation calculate "characteristic impedance", not the real trace resistance ?
Do I need to concern trace resistance during PCB design ? For example, is there any performance concern to send a 100MHz clock through a trace as long as 10cm, compare to only 1cm ? If so, is there any calculation tool to for the trace resistance ?

Thanks a lot.


texts: High efficiency buck-boost converters for 3.3V and 4V power rails up to 3A peak current

texts:
I need a buck-boost converter to power a 3.8-4.5V GSM module and a 3.3V controller from batteries. So I need a boost-buck converter that can give me a stable voltage over the lifetime of the batteries. Normally I'd use TPS61021ADSGR but it seems it's nowhere to be found - globally unavailable until November.
So I'm looking for alternatives with similar performance. Any ideas?


texts: Inverting (Buck-boost) converter polarity problem

texts:
I have trouble understanding something in the circuit below. It is inverting converter, seems quite easy, but the part I don't get is when the switch is OFF we have forward-biased diode, i.e. plus on anode - minus on cathode. Why then we have minus on the output pin that is THE EXACT SAME wire that is plus on the diode's anode? I don't get how can we state that anode is positive at the same time as other part of same wire is stated to be negative.

This is not a typo obviously, since it is popular circuit and everywhere it is like that.


texts: Buffer between high pass and low pass filter when making a bandpass filter?

texts: For a passive filter stage, I want to combine a high pass filter with a low pass filter to create a bandbass filter. Can I just make a simple RC circuit for each and connect them together? Or would we need a buffer between the two. The low and high cutoffs are 625 kHz and 1.535 MHz. This is for the front end of a simple AM receiver tuned to one frequency of 1.08 MHz.


texts: Infrared Receiver - Simple questions regarding data sheet and basic electronics

texts:
I've purchased a 36 kHz IR receiver (TSOP38436) but I'm still learning about electronics and I'm not sure how to connect this to my micro controller (Arduino).  (Also, I'm using 36 kHz instead of the standard 38 kHz for my project because it requires 36 kHz)

1) The data sheet shows a Supply Voltage of 2.5 V - 5.5 V.  Do I need to limit the current?  The data sheet also shows a Max Supply Current of 3 mA, and a typical supply current of 0.35 mA (at 3.3v).

Does this mean I should use something like a 3.3k ohm resistor with 3.3v to supply around 1 mA to the receiver?

2) The Application Circuit shows a resistor and circuit (R1 and C1) but I think they are only recommended for supply voltages less than 2.8v.

How would I know what values to use here?

3) Stupid question, but if I directly connect the receiver to an Arduino 3.3v with no resistor, then will that short circuit and blow the resistor sending too much current?


texts: Basic questions about transistor amplification

texts:
Can anyone explain how a transistor can amplify voltage or current? According to me, amplification means - You send in something small, it comes out bigger. Say for example, I want to amplify a sound wave. I whisper to a sound amplifier, & it comes out say, 5 times bigger(depending on the amplification factor)

But when I read about Transistor Amplifying action, all text books say that since a small change in the Base current ΔIb but a corresponding large change in Emitter current ΔIe, there is amplification. But where is amplification? What is being amplified as I've defined it? Is my understanding of the term amplification wrong? And how is current being transferred from a low resistance area to a high resistance area?

I think I've understood how the transistor is constructed & how the currents flow. So can anyone explain the transistor amplification action clearly & relate it to what I understand about amplification.


texts: LTSpice IV: How to vary input Voltage and measure the frequency?

texts:
I am getting started with LTSpice IV and I have a couple of beginner questions:

In the following circuit, I want to do the following (separately for each simulation):

Vary the amplitude of V1 from 20 volts to 200 volts in steps of 10.
Vary the frequency of V1 from 60 Hz to 300 Hz in steps of 10.

In both cases, I want to measure the frequency of the voltage across R2.

Please suggest me how to do this.

simulate this circuit – Schematic created using CircuitLab

Thanks.


texts: This is what i've drawn...assume that switch is working rapidly.the first figure shows the direction of magnetic field due to current from battery. Which is proper.but i get confused about second figure below it. Is it the correct polarity of self induced emf ? What will be the direction of magnetic field due to self induced emf...i am stuck..please explain me clear concept about it.


texts: Cheap effective proximity sensors for detecting people?

texts:
I'm building a small device that will be mounted on the ceiling (along with many other identical ones), facing downwards. I'd like to detect when someone walks underneath it. Due to the constraints of my system, the sensor needs to be:

Cheap - the whole device needs to cost about $5, so I'd rather not spend more than about $1 on the sensor.
Compact - the whole device is about 3cm diameter, so the sensor needs to be significantly smaller than that.
Reasonable range - when someone is standing under the device, their head may be 50cm - 1 meter away.

The sensor doesn't need to be fast - a few checks a second ought to be sufficient.

Cheap pretty much rules out 'passive IR' pyrometers, and compact and cheap rule out ultrasonic transponders. I tried an eletrostatic detector, but while it does a great job of detecting charged plastic objects, it doesn't respond to a person standing on a wooden floor at all.

Thus far, the best option seems to be an IR LED as a photodiode (I tried an actual phototransistor, but weirdly got a poorer signal than the LED). Using a setup with one LED emitting IR, and another reverse biased LED connected to an Arduino's analog in, I'm able to discern a useful return reflecting off my hand at anything up to half a meter. While this is usable, it's right at the edge of the range, and I'm concerned it may not work in the finished system. It does have the major advantage that I can put just one LED on each board, and use one board in sensing mode while another provides the illumination.

Can anyone suggest a better option for proximity detection, or a refinement to the active IR option to extend its range?


texts:
I’m reimplementing a certain proprietary USB cable. The other end of the cable among GND, VCC and data lines also features ID line

I implemented that identification protocol on a FPGA, but according to what I sniffed from the original cable, after handling one of the requests from master on ID line, the cable turns off VCC line for like 20 ms, then turns it on again. While this little gap, I believe, it switches to a full available current, because as far as I could investigate, this cable only allows 10-15 mA in an idle state (with 5V still though)

So to complete my task, I have to implement the same mechanism - being able to switch current on VCC line from 10 mA to full current USB can provide (so up to 2-3 A) on demand from FPGA/MCU

What would be the easiest solution for this?


texts: How to obtain the moment of inertia of the rotor?

texts: I need to measure or calculate the moment of inertia of the rotor in order to simulate a DC motor in computer simulation. Is there a procedure that can be followed to measure or calculate the moment of inertia without special lab equipment? Thanks


texts:
I am reading on DDR2 memory from past few days and have got confused with some of the terms involved.
I am mainly confused from discrete memory (single DDR2 memory IC) rather than DIMM module which consists of many such discrete ICs.

I understand that double data rate means the data is clocked on both rising and falling edge of clock signal. So, for example, if a 16-bit wide bus DDR2 memory IC is interfaced to a microcontroller (with built-in memory controller) at a clock speed of 200MHz (i.e. clock output from memory controller to DDR2 is 200MHz), how would one calculate the data rate?

As per my understanding, 16-bit bus has 16 data lines, and two data bits are transferred per clock cycle for one data line (for double data rate), meaning effective data rate would be: [No. of data lines (16, bits) x Data bits transferred per data line per clock cycle (2, bits) x Clock rate (200, MHz)] / 8 = 800 MB/s

(of course, I am talking of theoretical calculations only)

Have I got it wrong?

I would really appreciate if someone could please clear my confusions. Thank you.


texts:
I'm using a DSO-5200A from Voltcraft and noticed the voltage measurement represented incorrectly (it is doubled).
Any ideas how to reset this?

Channel 1 (green) measures a (noisy) 5V and has a Vmean measurement of 10V.
Channel 2 (yellow) measures the DSO's own calibration square wave. Frequency is measured correctly, but the mean value is again wrong.
The cursors correctly indicate a voltage difference of 2V.


texts: Preventing opamp from possible saturation maybe

texts:
I am trying to simulate a gyrator circuit for implementing capacitor as inductor in LTSpice. While simulation I am encountering the following problem :
 It seems that top left opamp undergoes saturation, as it gives clipped output blue one is the output green one is the input, like this below :
Please some one look and explain what's the problem, if I remove the top left opamp, I get sinusoidal waveforms.
I think this maybe due to saturation, but how to prevent it?
Some one explain.
UPDATE: when I tried with 1uF capacitance instead of 0.01uF, it works fine.(why?)


texts: Soldering questions - recovering data directly from eMMC via microSD adapter

texts:
My understanding of electrical engineering is pretty much non-existent, so please forgive any obvious oversights on my part.

I am currently trying to recover the data from an eMMC chip from a dead phone through soldering direct connections from the chip to a microSD adapter. This example shows in pictures what I am trying to achieve. As I cannot afford an eMMC socket (cannot post more than two links so you can find it on Amazon with product number B01LYUHB33) and the data I'm trying to recover is of sentimental value for my partner's grandmother, I am very keen to try to do it myself.

As it is one of the few times I'm actually soldering my questions are:

Is this wire that I bought appropriate? If not, do you have any recommendations?
Do I need to somehow strip the (possibly) very thin coating? Could I use a knife to do this?
It is my understanding from the example above that the VCC and VCCQ pins should be connected to each other on the chip. Is this necessary? I'd like to avoid as much soldering as possible (lacking both microscope and steady hands), so I'm already skipping connections DAT1-DAT3.
I'm assuming that I do not need solder balls if the wires are directly connected to the chip (as this is a BGA chip). Is this correct?

If there's any other tips that you can give me, they'd be greatly appreciated. Many thanks in advance.


texts:
first of all, let me apologise for my inexperience with electronics.

Now that's over with, I'm trying to follow a guide that specifies the use of a specific temperature sensor with an output of 5v DC. The problem is that the sensor I currently have provides different values and that a resistance of 14.2k ohms is required. The problem I have is that this step provides no further information. The actual step is as follows: -

  The outlined box above, which currently is set to 14.2, represents the resistance in to be added in parallel

I'd like to know how to obtain this specific resistance to place between the sensor and the controller that reads this value. I assumed I could build the resistance in a series.

I am under the impression that resistors can be placed in series, i.e. I could add a 10k ohm resistor and a 4k ohm resistor and then a 0.2k ohm resistor. Forgive my ignorance here, please, if this is completely idiotic. So I went to http://www.crownaudio.com/ohms-law.htm and entered 14200 and 5 into the respective fields and it specified that the watts was '0.00176'

Does this mean that when shopping for resistors, I can buy: -

http://www.maplin.co.uk/p/metal-film-06w-22k-ohm-resistor-m2k2

2.2k - 0.6w

http://www.maplin.co.uk/p/metal-film-06w-10k-ohm-resistor-m10k

10k - 0.6w

http://www.maplin.co.uk/p/metal-film-06w-2k-ohm-resistor-m2k

2k - 0.6w

I assume I need the same wattage for all but as above, adding all the resistances in series will create 14.2k ohms but they look so flimsy.

Thank you!


texts:
I was experimenting with capacitor voltage divider circuits but something unusual happened. Circuit is really simple , I connected 100uF 16v capacitor into 13.85V 50hz AC supply Xc is 26.5 ohm So I expected current will be 0.5A but multimeter showed 1A-1.2A then capacitor exploded.

I assumed capacitor overheated and that caused the explosion but why current is twice than it supposed to be ?

I made similar circuits with 47uF and 1uF capacitors and everything was right , why 100uF acts differently ?

Capacitors are radial electrolytic


texts:
I am designing a flyback converter using the PA3855.004NL transformer. Now, the datasheet screenshot is as shown below -

.

There is a value of 4.33 in the primary of the transformer. Is it the number of turns in the primary ? Now, suppose the number of turns of the primary is required to be 1.41, is it safe if I use one with 4.33 ? If not what will be the impact if I use one of higher or lesser turns.

Also, the datasheet gives only the primary DCR ,saturation current and inductance. Will these parameters of the secondary have no impact ?


texts:
I want to replace my relay with a high side MOSFET switch. I am a new to all this and I don't know how to choose the components.

The load needs around 200mA at 3.3v with the control coming from a open collector pin on a microcontroller. After some searching I found the following circuit. How do I modify this to run at 3.3v instead of 12v?


texts: Arduino died when grounds got disconnected

texts:
Alright bear with me since English is not my first language and it's my first time posting here.

So I was using my Arduino Nano (not genuine) to drive a single phase full bridge rectifier. The Arduino itself was being powered by an USB wall adapter. I used the 5V pin of the Arduino to power a 16x2 LCD and a LM358 Op Amp.

The LM358 also used an external -5V power supply since I was using it as a zero crossing detector for the sine wave. The 110V sine wave came from the mains to a 1:1 isolation transformer then to voltage divider to get a 5 V wave and then into the non inverting input of the Op Amp.

The SCRs where being triggered by the Arduino trough 4 MOC3023 optoisolators and a Snubber circuit. The Arduino, -5 V power supply and the 110 V sine wave all shared the same ground.

Everything was working fine until randomly, the -5V and 110 V ground cables got disconnected from my breadboard and the Arduino died.

The CH340C and ATmega328 chips get really hot now so I assume they are the ones who took the hit.

My question is, what could've caused the damage? and what can I do to avoid it?


texts: Connecting Three 12V DC Water pumps to the same power source

texts:
I am new to all this and I am sure this is a very basic question, but wanted to ask before I fry some pumps up.

I have a relay, which is controlled by my raspberry pi, switching the pump on and off. However, I would like the pump to pump 3 times more, can I just connect the other two in a serial fashion? So I do not want to control them individually, but basically treat them as one.

The pumps are 3.6w, 12V DC and pull roughly 0.4Amps. Power adapter outputs 12, 2 A. Max power is 24W.

Here are the links to the components:

Power:
https://www.amazon.de/gp/product/B019IHQND8/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

Pump:
https://www.amazon.de/gp/product/B07KJK6S4H/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

and

https://www.amazon.de/dp/B0721JLQG9/ref=dp_cerb_3

Relay:

https://www.amazon.de/gp/product/B07CNR7K9B/ref=ppx_yo_dt_b_asin_title_o09_s01?ie=UTF8&psc=1

Thanks for the reply, every little helps, even just pointing out how basic this is:D . I did a search, but nothing with this exact example, so I wanted to make sure.

I did consider a more powerful pump, but I am uneasy with having a powerful AC device submerged in water in the house without me there.

Thanks again!!! Happy Weekend :D


texts: Differentiator Op-amp with a triangular wave

texts: I’m trying to create a differentiator op-amp. The input signal is a triangular wave of frequency 100Hz and amplitude 1V. The circuit I have designed features a series resistor (Rin) and capacitor. Through trial and error, I calculated Rin to be 100 but I do not understand why it has to be 100. Please can someone help?


texts: An RC phase shift oscillator is a sine wave generator. It only needs a DC power source. No input is provided for circuit. What is happening inside the RC phase shift oscillator? How is a sine wave being generated there?


texts: How do I build a system for localizing sound source?

texts:
In my apartement I have the problem that when I am in my bedroom I can hear the neighbours in their bedroom exactly above me talking. Luckily I can not hear what they are saying but still pretty annoying.

First I thought that the sound travels directly trough my roof, but now I am not so sure since it is made of solid concrete. Our apartements are connected via 2 ventilation pipes that goes trough the concrete. My theory now is that the sound travels trough these pipes and trough my bedroom door.

I am looking to test this theory with some simple electronic equipment. I was thinking maybe a microphone outside my bedroom dor and one inside. By comparing timing and sound strength I should be able to tell if the sound travels trough the door or trough the roof.
I have a raspberry pi zero and an arduino kit that I have not used yet. Maybe I could use these. What kind of microphone should i use? I want to use something small. Would two smallish PC speakers work? Are there any small high sensitive microphones that are not too expensive that I can use with the Raspberry or Arduino? First I thought that I should have a radiocontrolled button in my bedroom turning the system on but now I am thinking maybe the system should just record continuously and when I hear the neighbours I look at watch and note the exact time. Later I playback the sound from the SD cards on the two boards and make sure it is the neighbours and not myself snoring.

Any ideas on how to do this?

Are there some prebuilt systems like sound recorder that I could use?


texts: Dipole Sleeve Antenna design in fresh water - Transmission frequency and emitted power?

texts:
Hello dear antenna enthusiast,

I would like to receive and emit EM signals with a dipole antenna in the range of **433.9 to 434.5 MHz in fresh water.

So I chose a half-wavelength dipole sleeve-antenna design that I made by myself out of coax cable (part of the coax is folded back and acts as the counter pole.
So one pole is the inner conductor of the coax cable and the counter pole is the outer layer of the coax stripped back and soldered onto the coax cable in the middle of the antenna. Similar to the one in the video...
https://www.youtube.com/watch?v=hK0KX0YcvH0

However I calculated the 433 MHz half-wavelength in fresh water as round about 19mm, but when I compare several antennas of the same type with different pole length, the one that has a peak in the reflected power plot (SWR in dB) at 433 MHz has a pole length of 80mm and with shorter poles the peak moves to the HF-area (as expected). You can see one of the reflected power plots in dB below, the antenna was in the middle of a 4mx8mx2m fresh-water tank connected to a VA by a 4m thin coax cable.

So I have now following questions...

Why is one antenna pole 80mm instead of 19mm, what would you expect?
Do I have to look at another physical value with my Network Analyzer or other gadget to be able to judge the performance of my antenna (max. emitted power), how does normal values look like?
Is it typical for a Dipole to have only one SWR peak at one frequency?


texts: Why are the Resistance/Resistivity Equations Formulated as they are?

texts:
The equation for temperature dependence on resistivity:

$$
\rho(dT) = \rho(0)(1+\alpha dT)
$$

where \$dT\$ is change in temperature from some reference and \$rho\$ is resistivity.  This leads to temperature dependence on resistance:

$$
R(dT) = R(0)(1+\alpha dT)
$$

This seems terrible to me.  I would much prefer something like:

$$
\rho(dT) = \rho(0) + \alpha_1 dT\\
R(dT) = R(0) + \alpha_2 dT
$$

This way seems much simpler to me.  It looks like a constant offset plus a slope.  This way, the slope doesn't depend on the initial value, which is mathematically more pleasing.  Why isn't it this simpler, more natural way?


texts: Impulse Response of a series RC filter where the output voltage is taken across the Capacitor

texts:
I am finding it difficult to understand the steps to derive the impulse response of a series RC filter where the output voltage is taken across the capacitor, the equation to derive is:

h(t)= (1/RC) e^(-t/RC)


texts: What's wrong with this Phase Shift Oscillator?

texts:
I am trying to design a phase shift oscillator, using a CE Amplifier.
I have a Vc of approximately 6V, gain of approximately 40(>29, as required).
I aim for an oscillation frequency of 1.5 kHz.

But whenever I feedback the CR network, no oscillations take place. Can anyone tell me what is wrong with the circuit?

simulate this circuit – Schematic created using CircuitLab


texts:
I have created a design with an STM32L07xxx and an ATtiny that communicate with each other through UART.

Unfortunately I forgot to include a pulldown resistor to the BOOT0 pin of the STM. The result is that the STM mostly starts in bootloader mode. A redesign nor rework are an option at the moment.

My initial strategy was to use the ATtiny to make use of the bootloader commands to jump to the application code with help of the 'Go' command (as described in AN3155)

Unfortunately the binary I've been provided with enables RDP level 1 which stops me from using 'Go'. (I've tried, it only responds with nACKs)

My final option seems to be to set read protection to level 2 to ensure the bootloader jumps to either bank1 or bank2 (AN2606 42.1.2)

My question is; How do I ensure that the bootsequence jumps to bank1?

Other alternative suggestions that result in the application code being executed are also welcome!


texts:
Sorry if this inquiry is it a little bit basic and boring, but I need some sort of help with this, and I am really not sure where to look online. I need help identifying several different electrical parts for a waste treatment build I am making a CAD draw up for, and as I am working remotely, my very busy employer has not had enough time to actually tell me what the exact parts are. Sorry for my ignorance, as I am actually a Mechanical Engineering student, and my experience with circuitry is relatively limited.

I don't really need to know the exact model number or anything, just the general name for it, as all I really need is to get a 3D model that looks SOMEWHAT like the object in question. Alternatively, if anyone could point me to a resource that I could somehow use to answer these questions on my own, then I would also appreciate that! Alright, here we go!

First photo:  First of all, what is the name of the... HUB, so to speak, in the middle of this photo? Also, what are the two things just under it?

Second Photo:  What is the name of the two hubs in this photo?

Third Photo: What is the name of the two socket outlet?

Thanks!


texts:
I have a Raspberry Pi and I want it to control DC motor speed. I make the pi output 3x3,3V for controlling the speed. I need circuit that works like this; when one output gives 3,3V motor have 6V, when two output pins gives 3,3V motor have 9V and when all output pins gives 3,3V motor have 12V. Can this be archieved with one mosfet and some resistors or do I need to buy three transistors and 6V and 9V regulators. Input voltage is 12V. I hope you guys get what I'm trying to achieve.

Ihave this mosfet now, I can use it for on/off switch to my motor when outputting 3,3V from one GPIO pin to the Gate. If I use three of these, one with 6V regulator, one with 9V regulator and one without any will it work? My motor is Lego XL motor so it does'nt draw so much current.


texts: Why am I having "Time step too small" error for this circuit in LTspice?

texts:
When I run this circuit I get the following error:

Unless I set R4 to around 1 Ohm the problem persists. How can I fix this issue?


texts: What causes old power supplies to start humming?

texts:
I have a number of mains-powered devices that have begun humming (I assume at 50Hz, though I haven't measured it). These include clock radios, a speaker system, a lamp (20W halogen with a transformer before the switch), and a temperature-controlled soldering iron. With some of these devices, it can be really annoying (like the radio and lamp and the speaker that vibrate the floor, and my bed, and make it hard to get to sleep). I assume it's also wasting a small amount of energy. I have tried taking one of the clock radios apart, and cleaned some dust and crap off the PCB (I couldn't see any other obvious problems), and it did reduce the hum a little, but not much, and it started getting worse again.

Is there a common cause for these hums? And is there anything that can be done about it?


texts: How to calculate total impedance of two parallel conductors

texts:
I am trying to calculate the total impedance of two parallel copper wires under the following conditions:

The copper wires are thick
I want to include all relevant effects, including (but not limited to):

Skin effect
Proximity effect
Internal self inductance
External self inductance
Mutual inductance
Any capacitive reactances

For now we can ignore wavelength as it pertains to cable length as my specific question pertains to frequencies less than 100kHz and wire lengths less than 100m so these effects can be ignored.
The copper wires are parallel to each other, like zip cord.
The copper wires form a return circuit, i.e. current in conductor A is the same as the current in conductor B but in opposite direction.
Assume an AC voltage source at one end of this circuit with a frequency of f, and f being no more than 100kHz.
Assume no load on the other end of the circuit - I merely want to model the impedance due to the wire, not due to the load.
Assume solid cylindrical copper conductors in a PVC isolator just like zip cord, and the two conductors being very close together (approximately 2 - 6mm).
Assume the wire is between AWG10 and AWG28

I have done tons of research and know how to calculate AC resistance due to skin effect, I think I understand how to calculate the internal self inductance due to skin effect, and I have some other calculations for external self inductance.  What I do not have is a complete picture of

which of above mentioned phenomena I need to consider
which of those are duplicates, i.e. different names for the same phenomena
which formulas to use for the rest of those phenomena

In the end I want to consider ALL phenomena that would have an effect of at least 0.001% in the given frequency range and wire specifications above.  So I want to solve:

Zac = Rac + j(Xl - Xc)

where Rac includes all resistances, Xl all inductances and Xc all capacitances.

Ignore the environment for now (i.e. any dielectrics / objects in the vicinity except for these two conductors).

I have reviewed these papers:

http://g3ynh.info/zdocs/refs/NBS/Rosa1908.pdf
http://g3ynh.info/zdocs/comps/Zint.pdf

And many others but get confused as per above.


texts:
I've read that flash memories can "only" be reprogrammed 100000 to 1000000 times, until the memory storage "deteriorates"

Why exactly does this happen with flash and not other memory types, and what does "deteriorate" refer to, internally?

EDIT: Since it's not only flash that this happens, I'd like to generalize a bit and inquire about the memories that have this problem. Also, does the wearing out between these memory types occur due to the same phenomenon?


texts: Calculating power emitted from electronics

texts:
I am trying to figure out how much "thermal noise" electronics may produce as I am trying to detect the cosmic microwave background radiation, but the electronics surrounding the detector will obviously pick up noise from the equipment.

I wanted to know if there was a way to calculate how much to expect.

I am attempting to use a signal to noise ratio of \$\frac {power of signal} {power noise}\$ to see if I get near the golden 1:1 ratio.

The issue is I don't know how to estimate the approximate power of the noise from electronics.


texts: Good way to affordably manufacture low-quantity PCB?

texts:
I am thinking about making an open-source development board for a specific field in power conversion.

If there is interest from local universities, I will manufacture a few hundreds of these boards.  Is it better to engage a manufacturer or buy a small pick-n-place machine?

EDIT:  It is assumed that the PCBs will be sourced out.  The number of components should fall in the <20, 50> range.  The DSC/MCU could have ~200 pins, TQFP package.

EDIT2:  The answers so far indicate that it is very costly and time demanding to make PCBs at home.  But what is the approximate cost to get the minimum viable production line for a few hundred boards?  To get done ~20 per hour (e.g. 2" by 4").


texts: Programmable FGMOS’ simulation model using Virtuoso

texts: I know that one can introduce programmability in FGMOS transistor using Fowler-Nordheim Tunneling and hot electron injection, but am unable to implement this idea in cadence design tool virtuoso. I would like to know how to generate this equivalent model of programmable FGMOS in virtuoso? What are the circuit components that need to be added in order to achieve tunneling and injection in a FGMOS?


texts: Draw the maginitude as function of frequency

texts:
The circuit is this one, it consists of two common emitter transistors

simulate this circuit – Schematic created using CircuitLab

Some of the components where given but the others I had to find out by myself.

The next step was to find the transfer function for AC for \$\frac{U_{C1}}{U_1}\$ and \$  \frac{U_{C2}}{U_1}\$, with \$r_{be}=2 k\Omega.\$
And I got the following expression,
 $$\frac{U_{C1}}{U_1}=\ \frac{\beta R_{C1}}{r_{be}}$$
 $$\frac{U_{C2}}{U_1}=\frac{\beta^2 R_{C1} R_{C2}}{2 r_{be}}$$

This is where I am confused and need some help

I have to draw the magnitude of \$\frac{U_{C1}}{U_1}\$ and \$  \frac{U_{C2}}{U_1}\$, and in the solution it is supposed to look like this

This is the result, but I just don't know how it came to be like that, so I would really appreciate some help, since it took me a lot of time to make this question.


texts:
It is clear to me that the resistor represents a physical obstruction to the passing current I do not know how exactly it works and I will try to show what I was really interested in the diagram.

In addition to this I actually wanted to ask how the resistor limits the current across the circuit when only one part of the DC current passes through it. diagram below.

How the resistor affects the other side of the wire. How the resistor limits the current and on the other side of the wire when the electrons do not pass through its resistance.

enter image description here


texts:
Possible Duplicate:
  How much does it cost to have a custom ASIC made?

I'm wondering, just out of curiosity, what it might cost for somebody to have their own integrated circuit design fabricated. I know next to nothing about any of this, so a good breakdown of ballpark figures for different technologies would be nice.


texts: Why the intersection points in SPWM define the width of the pulse?

texts:
After my previous question Why the triangle reference wave is used in PWM for sine modulation I still have some troubles on one particular point of natural sampled PWMs or more precisly SPWM.

My question is: Why the intersection points between the carrier and the reference wave are the "hot spots" where the width of the PWM is calculated?

In all the literature that I read no one mentions why the comparison works and what is the core meaning behind it. In fact every paper and PWM related article states something on those lines:

  The output \$V_0\$ of each comparator has a "high" level whenever the instantaneous input reference level exceeds the timing wave level and a "low" level when the reference is exceeded by the timing wave, resulting in a PWM waveform,...[1]

  When the reference waveform is greater than the carrier waveform, the phase leg is switched to the upper DC rail. When the reference waveform is less than the carrier waveform, the phase leg is switched to the lower DC rail... [2]

I'm searching meaning behind those types of statements and the only thing that comes to my mind is that:

1) integrating a square (on it's period) produces a half triangle
$$ + $$
 2) the technique behind PWM is to reproduce the average value of the reference wave in small \$\Delta t \$'s (over and over)
$$\Downarrow$$
intersecting the reference wave with the carrier (that represents the area of a full pulse (1)) produces the point where the width of the pulse has to stop to represent the avg value of the reference wave for that period (\$\Delta t \$ (2)).

$$ $$

[1] "Pulsewidth Modulated Inverter Motor Drives with Improved Modulation" IEEE Transactions on Industry Applications Volume IA-11 issue 6 1975 Zubek Jacob; Abbondanti Alberto; Norby Craig J.

[2] D. Grahame Holmes, Thomas A. Lipo "Pulse Width Modulation for Power Converters Principles and Practice"-Wiley-IEEE Press (2003)


texts:
I have a gadget that does contain a 12V AC synchronous gear motor (2 Terminals) that i want to hack.

I want to supply the gadget with 12V DC (among other changes).

Up to now i use tiny AVR and a LB1641 motor driver to feed the motor with voltage of alternating polarity.
Everything between 20 and 60 Hz with Pulses between 70% and 100% seems to work well.

L1  _____---_____---_____
L2  _---_____---_____---_

But the motor does not run as quiet as from the wall wart supply.

How can i transform the output of the Motor driver into something that is more pleaseant to the motor and my ears?


texts: How connections should be made and what kind of capacitor should be used in these circuits from 4000 series?

texts:
I am trying to test this circuit from below but I a not sure which kind of capacitor should I use and how should I use it.

My question begins here, as I found two contradictory schematics, one is from ST and the other is from On Semiconductor. Although ON seems 'clear' on what to connect and where, ST makes it seem dubious. See the pictures as a reference.

ST seems to point that pin 1 and pin 15 should be only tied to one end of the capacitor while the other should be connected to the resistor in series. But on the following page it seems to indicate the contrary, in other words that pin 1 and 15 by extension should be tied to GND. Am i missing something?

In order to clarify or settle any doubts i referred to ON Semiconductor which can be seen below in the same picture from above.

However they do not seem to 'clear' my doubts regarding the correct connection of the capacitor as i am not familiar with the notation or drawing of the capacitor with one curved end. Mind somebody explain this part?

Now the second part of my question and that it includes the first one as well is that I am trying to test out this circuit.

However once again I am not sure which way should that capacitor be connected, since what I want to try out are capacitors of let's say 1uF and beyond, those seem to come as polarized varieties, like aluminum or tantalum. Wikipedia article states tantalum have low leakage and that they are good for sample and hold circuits and applications where timing is not critical. Overall what type of capacitor is recommended for both circuits?. Because I am confused on the right connections as I dont want to destroy or damage any component I would like to get that clarification first.


texts:
Reading the report here, they use 'Log-Domain Integration'.

It is said to be a type of 'Log-Domain' Filter, but googling it, there is just a bunch of reports/articles on it.

Can anyone explain what Log-Domain filtering is and why we might use it over?


texts: Finite State Machine (FSM) bit sequence detector for a stream of several bits

texts:
Typically, drawing out a FSM is the solution to this problem. However, my question here is its implementation.
I thought of two ways but i am not sure if they were correct.

typical FSM, truth table for current states, next states and 1-bit output. Develop the logic function for each output and implement the logic function with and gates and etc.
5 consecutive flipflops connect to a single mux as its control signal. Each stage contribute 1 bits to the control. Until the control signal from these flipflops matches the required pattern, select and output 1.

Which way is correct since most often I see people use the 1st method.

Which method is best to design a sequence detector for a stream of several bits? For example: 10110


texts: 3 Input XNOR gate made with XOR and not gates

texts:
hi i have implemented this equation with XOR and Not gate but i'm not getting the correct answers
(A.B.C)+(A'.B'.C')

What is the Problem ?
thank you


texts: Can Altera GPIO pins read the input voltage?

texts: I have ALtera DE2-115, and I have a light sensor module, the output of the light sensor is a voltage, how can I use the Altera GPIO pins to read the coming voltage? Thanks


texts:
I want to build an electric bike and i need some sort of control over the motor ( i want to build it myself):
It doesn t have to be a throttle-like control (as the ones on actual motorcycles), it just has to control the speed of the motor. What is the best way to do so? Would a transistor be ok (1kw - maximmum power of the motor that i will chose - 220vAC)?
I can use an Arduino to control it. Is there a better alternative to this ?


texts: Power design for active car antenna: Directly from battery or voltage regulator?

texts:
I'm designing a circuit that should be able to connect to two active radio antennas. The antennas are phantom powered, 12V, and has a current consumption of 25mA each. It should be possible to turn phantom power off with 3.3V logic in case a passive antenna is connected.

The power supply section of the circuit consists of the following:
12V from the car battery -> TVS-diodes -> smart diode ic (LM74610) -> EMI filter before it is distributed to consumers through separate 3.3V and 1.8V converters.

My question is how to best provide power to the active antennas?

Take 12V directly after the EMI filter and use a high side switch with embedded protection circuitry. Like this from Infineon
Use a separate voltage regulator with ON/OFF and embedded protection circuitry. Like this from Semtech.
Something completely different?


texts:
I have a NUCLEO-F303RE board and try to send some data by one-wire UART with 57600 baudrate. But frames are sent broken (see images below):
How must to be:

What I get:

I've tried to use different clocks (HSE 32MHz and internal HSI 8MHz), change baud rate to 9600, but nothing helps and frames are broken the same way. I suppose I have a bad configuration of something, but I have no idea what is wrong. I have another UART connected which is used for debug and it works fine on 57600 baud rate (not in half-duplex mode) with same clock.
My UART configuration:
#define SERVO_PORT            GPIOB
#define SERVO_PIN             GPIO_PIN_10
#define SERVO_GPIO_ENABLE()   __HAL_RCC_GPIOB_CLK_ENABLE()

#define UART_INSTANCE         USART3
#define UART_CLK_ENABLE()     __HAL_RCC_USART3_CLK_ENABLE()
#define UART_AF               GPIO_AF7_USART3
#define UART_IRQ              USART3_IRQn
#define UART_IRQ_HANDLER      USART3_IRQHandler

static UART_HandleTypeDef huart = {
  .Instance          = UART_INSTANCE,
  .Init.BaudRate     = 57600,
  .Init.WordLength   = UART_WORDLENGTH_8B,
  .Init.StopBits     = UART_STOPBITS_1,
  .Init.Mode         = UART_MODE_TX_RX,
  .Init.Parity       = UART_PARITY_NONE,
};

/* Called later in HAL_UART_MspInit */
void Servo_UART_MspInit(UART_HandleTypeDef* h) {
  if (h == &huart) {
    SERVO_GPIO_ENABLE();
    UART_CLK_ENABLE();

    GPIO_InitTypeDef pin = {
      .Pin        = SERVO_PIN,
      .Mode       = GPIO_MODE_AF_PP,
      .Pull       = GPIO_NOPULL,
      .Speed      = GPIO_SPEED_FREQ_HIGH,
      .Alternate  = UART_AF,
    };
    HAL_GPIO_Init(SERVO_PORT, &pin);
  }
}

void initUART() {
  HAL_TIM_PWM_DeInit(&htim);

  HAL_HalfDuplex_Init(&huart);

  HAL_NVIC_SetPriority(UART_IRQ, 0, 0);
  HAL_NVIC_EnableIRQ(UART_IRQ);
  HAL_HalfDuplex_EnableReceiver(&huart);
}

bool servoSend(uint8_t* data, uint8_t size) {
  HAL_HalfDuplex_EnableTransmitter(&huart);
  return HAL_OK == HAL_UART_Transmit(&huart, data, size, HAL_MAX_DELAY);
}

And I send data like this:
...
uint8_t d[5] = {0x2B, 0x0, 0xD5, 2, 0xB1};
bool ret = servoSend(d, 5);
if (!ret) return DITEX_SERVO_CALLBACK_FAILED;
...

My clock initialization:
static void initSystemClock() {
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_BYPASS;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL4;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV2;
  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART2|RCC_PERIPHCLK_USART3
                              |RCC_PERIPHCLK_TIM2;
  PeriphClkInit.Usart2ClockSelection = RCC_USART2CLKSOURCE_SYSCLK;
  PeriphClkInit.Usart3ClockSelection = RCC_USART3CLKSOURCE_SYSCLK;
  PeriphClkInit.Tim2ClockSelection = RCC_TIM2CLK_HCLK;
}


texts: Data transmission : what is neutral current method?

texts:
I'm reading a book about data transmission inside a PC.

I'm trying to understand a phrase, translated from german, saying this :

  In a PC, data are transmitted almost exclusively using the so-called 'neutral current method', which could be for instance NRZ or RZ.

I'm not sure if 'neutral current method' is correct, as I didn't find anything relevant with google.

Does anyone know what this method is ?


texts: Problematic electronic volume control TC9176P

texts:
I found this site on google while looking for a palce where I could ask electronics questions so bare with me if I'm a bit fuzzy on details and articulation.

I have a vintage sony TA-158 stereo amp with electronic (+/- buttons) volume controls. The volume jumps high and then low and then back to normal within the lower third (1/3) of the volume range whenever I try adjusting the volume.

I purchased the service manual and from looking at the schematics I found there was a Volume Control (signal attenuator??) TC9176P and figured this was the right palce to start. So I ordered a handfull for these ICs and replaced the one in the amp. The problem still persists. From a quick scan of the schematics it looks like the TC9176P talks directly to the main power amp via some basic circuity components (no ICs between them both).

MY QUESTION:
Does anyone have any experience with volume controls / signal attenuators like this and can point me in the right direction as to what component might be causing the jumpy volume. What should I be troubleshooting next?? Dry/faulty Capacitors?? Resistors?? The amp is from the early 1980s so it's around 30+ years old. What components typically give-up at this stage??

Any insights would be greatly appreciated.


texts: Cache. MESI protocol for multilevel cache in Intel processors

texts: Now I'm trying to simulate the performance of Intel CORE 2 Duo processor (but I'll be very pleased with information about any other multi-core Intel processor) and it's work with the computer memory. As I understood, the main problem that exists with memory - is to support the coherence of cache. But how does the protocol MESI work with different layers? For example how does it apply to L2 and L3? I also would be very glad to know enything about non-exclusive write policy implementation and if the replascement algoritm of L2 is connected to the block being replaced from L1? Does Anyone know anything about this?


texts: How do two-leaded color changing LEDs work?

texts:
I have a few 3mm color-changing LEDs which I harvested from a toy. They fade in between all different colors, and then after a little while, they blink crazily between all the colors. After a few moments, the cycle repeats.

What is interesting about them (and what I wasn't expecting) is that they only have two leads, like a normal hobbyist LED.

I understand that, like an RGB LED, they have multiple elements (probably not the right word) inside. But how do they achieve the color changing and cycling?

Here is a picture of the LED in question:

Notice the little bit of black material inside the LED. Could this possibly be a tiny chip?


texts: How do I solder thick goldplated DIA pins?

texts:
I am struggling with soldering some pretty think gold plated DIA pins to one of my boards.

I've tried various things such as;

Increasing the heat of my soldering iron, but am afraid of burning my board.
Sand off some of the gold plating to try and make the connection easier.
Increase the amount of flux I use.
Increase the time I'm heating the pin/board.

None of the above have given me favorable results. I'm hoping some of you here can steer me in the right direction.

I think I might be too careful and need to heat the pins/connection much more due to the heat dissipation of the thick pins, but before I do that and break things I want to check with some of you.

Thank you very much, I appreciate any responses.


texts: Let's say I want the motor rotate to 21.73 degree, will servo motor rotate to the desired degree accordingly? Or maybe the motor will rotate to 22 degree?


texts: How do they read out HD, high frame rate CCD image sensors

texts:
Having little experience with CCD image sensors, I have learned that reading pixels via shift registers from a relatively large size CCD must be fast to achieve some reasonable frame rate. Let's say, for a 5M pixel CCD imager to get a 30fps rate, the pixel readout rate must be at least 150Msps. I thought that running the readout for each row/column separately would be about half of that, but this would require 2.2 thousand pins (for each row, if the imager was square shaped).

So, how does this readout is performed in cameras, smartphones and other devices that provide HD video? Can CDD imagers achieve such high pixel readout rate?


texts:
I am using LM2576T as a regulator in my design.
I made a circuit by the datasheet, but I haven't connected the diode (I haven't got any at the moment).
Could it be a reason for switching regulator to overheat? I've tried it with low load currents (100-200 mA) with heatsink installed and the regulator is still overheating.

Datasheet : Switching regulator datasheet


texts: Thevenin's Theorem: Why is there a \$R_{th}\$

texts:
Consider a linear mess present inside the box,

simulate this circuit – Schematic created using CircuitLab

If there's a voltage drop \$v\$ across the load, then why cant we simply replace the entire  linear mess into a Voltage source in series with the load,

Why do we include a Thevenin resistance? I mean I know this is absurd, but then, why not?
 If we introduce a resistor in the circuit, then the drop across \$a\$ and \$b\$ will no longer be the open circuit voltage, it would be lesser than that. So once we include a Resistance \$R_{th}\$ shouldn't we form a Thevenin's Equivalent, with a source accounting for the drop across \$R_{th}\$ so that the drop across the load remains same?

P.S: This question is closely related to this question of mine


texts:
I have made an application with 3 Omron IR LED Photo sensors. This sensor can't be bought anymore, but here is the datasheet.
I used a transformer 230 AC - 24 AC. Due to induction? the sensor output is 1.2V instead of 0 V. The sensor output is connected with a D-Sub 9 connector which leads to my computer where I made a program to run the setup.
What is the best and most efficient way to reduce the 1.2V to 0 Volts? Is using a Pull Down resistor the best solution, what kind of resistor do I need to use in that case?
This is the electronic schematic: I don't think the '3' and 'PE' are connected properly, right?


texts: Measuring a high dynamic range current decay with different amplifier gains

texts:
I would like to see a current decay from a photodiode with a high dynamic range. By saying "high dynamic range", I mean it decayed from about 1uA down to 100pA or 10pA. I tried with a linear preamplifier SR570 that had different transimpedance gains. The measurement circuit is shown below:

http://imageshack.us/a/img195/9854/measurementcircuit.png

My crude idea was to measure the initial fast and high current with low gain, then the later slow and low current with high gain (unavoidably I would get initial overload plateau with this high gain measurement), and somehow stitch them together to have a full picture.  The example measurement results are shown below:

However, I am not sure how to stitch them together. There is obviously some time delay between these two transients. For this specific case, the DC input impedance of the amplifier is 100 Ohm with 1e5 V/A gain, and 10kOhm with 1e7 V/A gain. The bandwidth is 20kHz and 2kHz for this two gains respectively. So it is not surprising to see a time delay. There may be other artifacts. Can anyone suggest any solution?