texts: Voltage/Frequency characteristics as a motor dies off

texts:
So, hopefully this is a simple enough answer for someone.  I was recently posed a question concerning the coastdown characteristics of a pump as they pertain to the trip setpoints of a breaker.  One electrical bus supplies two water pumps, similar in design.  They're both 6900V, 3-phase motors.   The load breakers do not interlock directly with the feed breaker, rather, they are designed to trip on either low voltage (5300V, 0.8s delay, or immediately upon reaching 4900V) or low frequency (57Hz, 0.4s delay).

The question posed was whether the load breaker would first trip on voltage or frequency, in the event of a feed breaker trip.  My thought is that once the supply voltage is gone, the pump will, in effect, act as a generator and power the bus during coastdown.  This is mostly irrelevant, obviously both pumps are coasting down, but it will influence which trip setpoint is reached first.  I understand the frequency characteristic will be proportional to the speed of the pump as it coasts down, but I'm not sure of the voltage response.

I realize this isn't nearly enough information to do calculations on, but I'm not looking for a full engineering analysis, just a prod in the right direction.  Thanks for any insights!

Edit:  In response to Brian Drummond:  Yes, it is a squirrel-cage induction motor.

Edit:  In response to Charles Cowie:  This bus has only the two pumps attached to it, nothing else.  There would be some minor capacitance from the wires themselves, but probably insigificant.

Edit:  The motor is 7,000 HP and has an 8-ton flywheel to extend coastdown time on loss of power, so I imagine connecting it to a grid without regard to phase would be quite dramatic.


texts: Motor Control with PMW or RPM on heavy robot

texts:
I'm going to try to explain my problem as clearly as I can.

I have been building a robot that has four wheels, 2 motors and 2 free wheels.
Its a differential drive system.

O --- O Motor Wheels
|     |
-o---o- Free Wheels.

The objective of this robot is to follow something/someone. I have cameras that give me a 3D point I use to define a position, and based on a setpoint, I correct the Front Error and Side Error with two PID controllers.

1 - Basic calculations to adjust robot are

Left Wheel = ( FrontError - SideError ) * Acceleration;
Right Wheel = ( FrontError + SideError ) * Acceleration;

Side Error and Front Error are results of Two different PIDs. One for each axis of a 3D coordinate space. Front is error on Z ( distance ), Side is error on X ( deviation from center ).

Q1: When I test the two PIDs independently, if only testing for front correction, or only side correction, everything works. But when I use the two PIDs I lose control of the robot. Any Idea why? Higher the speed the less control I have.

2 - I am controlling this through software on a computer, and sending those values to a board that controls the motors. What I am sending is PWM values. My problem is: since two motors are never equal, and depending on the load/weight the robot has on top of it, I need different PWM values for EACH wheel, for the robot to go forward. Sometimes, on a scale of 0-1023, if I set 150 PWM to one wheel and 400 to the other wheel, the robot doesn't turn as my calculations predict it would turn and goes straight forward.

Leading to my second question.

Q2: When dealing with this kind of robots and control. What are the best way to solve this problem? I'm thinking of encoders. Controlling through RPM rather than PWM, and having a PID on each wheel on the motor controller board. Which leads to another issue. Lattency. I have a loop of 175ms. Taking that into account, what's the best solution for me?


texts: Simple CMOS switch with weird voltage in LTSpice

texts:
I am new to all this, so please forgive me, as I feel the answer to this must be so simple.

I tried to build a basic CMOS switch. It has a supply of 5 V. There are periodic pulses of 5 V supplied to the input.

I expected the output to alternate between 0 V and 5 V. After running the simulation, I was surprised to find out that it alternates between 0 V and 620 mV.

Either I am not understanding things correctly, or there is something wrong here. Why am I not seeing 5 V on the output?


texts: What does "Cycle \$\mu\$s" mean in this context?

texts:
I'm reading a paper about the architecture of the IBM system/360. There is a diagram which lays out the machine structure and implementation in the storage and control tables there is a metric which I don't understand which is Cycle \$\mu\$s:

What is this metric referring to ? Thanks for the help.


texts: microcontroller current supply - noise minimisation

texts:
I'm building an Arduino-based quadcopter. I already built a partially working prototype and now I'm preparing the second version, which will probably be the definitive one.

Instead of the the whole Arduino (UNO) board (actually it's quite a small quadcopter, and the board is too big for it), I'm going to use only the microcontroller, ATMEGA328. I set it up on a breadboard following this tutorial on Arduino's site and it works fine... if I don't use my 4 motors simultaneously (but of course in order to run a quadcopter I need them to work together).

My quadcopter is powered by a single cell LiPo battery (3,7V; 600mAh; 2,22Wh): a unique battery for the 4 brushed motors, the microcontroller and some sensors. If I connect the ATmega328 directly to the battery, just like the motors, it sometimes fails and reset for example because of some current spikes, too big for the battery, when the motors start.

So my question is: can I set up a "stable" circuit, with as little noise as possible, to run the Arduino and the sensors first of all without risk of failure in case of current spikes in the motor's circuit, and secondarily to get the best ADC results etc.? How can I do that?


texts:
I am in the process of building a simple IMU for an autopilot. I am using Sparkfun, 9 Degrees of Freedom - Razor IMU. It is surprisingly user friendly.

I was able to get accelerometer, gyro and magnetometer data right out of the box. After calibration of the sensors and a simple complementary filter i have reliable roll and pitch values.

Now I have a problem with the yaw...

I found here http://www.pololu.com/file/download/...?file_id=0J434 the equation to get the yaw out of the magnetometer value:

$$X_h = X_m\cdot cos(Pitch) + Z_m \cdot sin(Pitch)$$
$$Y_h= X_m\cdot sin(Roll)\cdot sin(Pitch) + Y_m\cdot cos(Roll) - Z_m\cdot sin(Roll)\cdot cos(Pitch)$$
with Xm, Ym, and Zm are magnetic sensor measurements

$$Yaw = Heading = arctan( \frac{Y_h}{X_h} )$$

It sound be simple, but I can't do it. I hope that someone who already worked on IMUs can help me solve this problem.

Here (http://diydrones.com/forum/attachment/download?id=705844%3AUploadedFile%3A1327110) is an excel file with IMU data and equations.

The graph (in Excel file) shows results (first i rolled 90 degrees, then I pitched 90 degrees then I yawed 90 degrees).

Roll and pitch are calculated by the IMU (programmed with Arduino IDE), they are good.

Yaw is calculated in Excel using gyro (good but drift over time) and I also calculated Yaw using the equation above (green line) and it is totally wrong (it should follow the gyro line / purple).

Any help will be appreciated.


texts: What is the function for F exit in this scheme?


texts: Solder joint only working while solder is still liquid

texts:
I am wiring an electric guitar.

Part of the wiring process is a tone capacitor (0.022 µF) which is attached to a linear taper potentiometer, when the potentiometer is turned, the capacitor is brought into the circuit and takes away the high end treble of the signal, essentially a low pass filter.

I have wired a few guitars and am comfortable with the basic circuitry, I have never had this problem.

I have the guitar wiring hooked up to an amp and I am listening to it, when I heat the solder, the capacitor to one of the arms of the potentiometer I have about 5 seconds of it working as it should, rolling off the treble, being active in the circuit, until it cools down and blam it stops working.

Mind you the cap has two arms, one grounded to the outside of the pot and the other going into one of the arms of the pot, it’s only the one attached to the arm that needs to be warmed.

Other things I have troubleshooted:

I have tried four different capacitors, all behave the same way, two of the four are 0.047 µF and the other two are 0.022 µF. One is rated for 400 V the other for 100 V although this doesn’t mean anything in guitar as there is no voltage running through the circuitry.
The 400 V one seems to last the longest but my guess is because it can retain the most heat as it is physically the largest and allows the solder to stay warmer longer.
I have tried the capacitors in each orientation (if there is an orientation to the capacitor)
I have replicated this behaviour of only working when warm dozens of times.

I guess it has to be a cold solder joint problem. Is that suspicion right?
The solder I am using is lead free.

Is it possible the solder is creating an oxidation later as it cools? All other connection in the wiring are working as normal. None of the parts are damaged.

I can provide sound and video and pictures as needed.


texts:
With a circuit of a charged capacitor, a resistor, and an LED, I can create a lighten up LED that gradually dims until the capacitor run out of charge.

With a combination of a battery, capacitors, resistors, and LED, is it possible to create the opposite effect, that is an LED that gradually lighten up? If not, what kind of components that I might need to produce this effect?


texts: Need help with understanding the pros and cons of geometric and stochastic based channel models. Which one s preferred under which conditions?

texts:
https://www.adv-radio-sci.net/9/165/2011/ars-9-165-2011.pdf

https://ieeexplore.ieee.org/document/7794648

https://pdfs.semanticscholar.org/c301/8463116117ea64f69638e15aa78fe9e84093.pdf

https://www.springer.com/cda/content/document/cda_downloaddocument/9783642174957-c1.pdf?SGWID=0-0-45-1113975-p174079771

The above links are papers that describe the different channel models. My question specifically is that are there any scenarios where using one is advantageous than the other one. I read that it is preferred to use geometry based models as it can distinguish between LOS and NLOS in vehicular network scenarios.


texts: How do I deal with Seebeck Effect while measuring resistance with 4-lead ohmmeter?

texts:
I'm trying to measure the DC resistance of an inductor I made out of AWG 11 wire.
From my calculations its impedance should be around 0.0012 ohm, and the ohmmeter measured precisely 0.0012 ohm.
But that at ambient temperature (which was 18ºC). But I had to measure its impedance at different temperatures too.
Then I tried heating the inductor with an hot air gun from a distance, at the lowest power. It heated to mere 30 ºC and stabilized at that temperature, but the resistance went up to 0.0041 ohm. That sure was impossible, it's too much of an increase due to such a small heating.
When that happened it occurred to me it should be some thermoelectric effect. Without removing the hot air I inverted the polarity of both pairs of leads and read again. Now a negative resistance appeared while it was being heated, but after cooling down the resistance went back to positive 0.0012 ohm (as it should be, cause inverting both pairs should not make a difference).
The 4 leads are all very close together in inductor (all like 2-3 cm apart at max) and being roughly uniformly heated. There's no reason for a difference in temperature to arise in there, but there's a difference in temperature from all of them at the inductor and the other ends in the ohmmeter.
I can't heat the ohmmeter together, what can I do to compensate for the seebeck effect?
I imagine that, If the seebeck effect voltage is being added in one way and subtracted in the other, adding the resistances measured in both ways (the negative one and the large positive one) should give me the correct value.
Am I correct?


texts:
Lets consider for instance this voltage doubler:

It was told that a practical limit of this circuit is the fact that we cannot absorb too much current from it. But I wanted to verify (if it is true) this by analyzing the circuit. Intuitively I may think that, since the maximum power which can be provided by the voltage source V1 is fixed, double voltage will mean half current. But I wanted to have a more precise idea of how much current a load can absorb with respect to that provided by V1.


texts: CW Doppler probe for fetal doppler and blood flow velocity

texts:
I am currently working on a microcontroller based project to measure the blood flow velocity using ultrasound doppler.
I have purchased two Spengler 8 MHz continuous mode probes in order to measure the doppler shift.
I have disassembled one of the probes to test it.  It is formed of an 8 MHz crystal, which outputs a 2 V ppk 8 MHz sine wave (as viewed on the oscilloscope.) It also has an MC1496 modulator/demodulator chip to remove the carrier frequency followed by an LM324 chip for amplification.
The final probe output are two wires, sig1 and sig2.
I have tested the outputs on the oscilloscope and compared them to the RX and TX signals of the sensor after breaking the probe open.
My experience in analog circuit design is very limited, especially in piezoelectric crystal signal conditioning and fetal doppler.
I have exported the signals to Matlab with the hope of detecting the blood velocity using FFT. I performed AM demodulation as well.
I am sure it is based on AM because when I hit the probe head the sig1 amplitude changes and rises, but I am not understanding how the CW doppler probe circuit works.
Based on what I found, this is a common and standard circuit used in probes and devices to detect fetal heartbeat.
How does it work? I do not see any shift in frequency in the heartbeat range using FFT.
I have finally found the probe circuit, my outputs of interest are output2 and output3, from the final stage it seems they are using output3:

(This circuit is taken from https://patents.google.com/patent/CN203970415U/en)
I have attached the simulation outputs:


texts:
I'm new for PIC32MX and would like to ask the following.
Does the oscillator or resonator generates waves when the micros is not programming i.e. is empty
Tony


texts: Splitting Audio Out - are there any issues I am not seeing?

texts:
first post, so I hope this isn't TOO stupid a question. I am planning on building this circuit:

https://github.com/trash80/Ym2149Synth/blob/master/Ym2149SynthSchematic-V29082016.pdf

which eventually outputs 3 audio signals from three pins on the YM2149 chip (see top right).

On the original I think these are just wired so that one is on the left of the stereo signal, and the other two on the right (? - correct me if I'm wrong!)

Ideally  would like to complete the circuit with one 1/4" jack that outputs all three signals in mono, and then three separate jacks that output each pin separately.

Is there any issue with simply "tapping off" the signal from each pin post resistor to a separate output, before they go to the "all in" jack?

Would I need to add anything else?

thanks in advance for any help offered - I think other questions on here suggest it should be fine, but these mostly involve "Y splitter" cabling rather than actual circuit building.


texts: Core-less transformer for Zero-crossing detection

texts:
If possible, what are calculations and precautions involved in making a simple transformer without core? The only purpose of this transformer is to trigger an opto-coupler for zero-crossing detection of mains supply.

simulate this circuit – Schematic created using CircuitLab


texts: Drive transistor harder for more distortion

texts: I've been working on a distortion circuit for a guitar pedal and so far I like the tone but I was wondering if I could get some insight on how I might drive the transistor (T1) harder, increase gain to get a stronger distortion sound. Right now it's a bit too mellow. Is it about getting higher voltage to the base? Where would be a good starting point for swapping out components to experiment? I'm still learning the basics and starting to experiment with transistor distortion. Thanks!


texts: Input power rating on power supplies - how does max amp draw apply to 220V

texts:
If a power supply says the input power is 100-240V, ~1.5A, I'm assuming that the "1.5A" draw would be at 100V, not at 240V, right?  I.e. would the total max watts be 150W regardless of the input voltage?

The context of this is trying to determine the maximum draw for something based on the input power specs on its power supply to ensure a circuit doesn't get overloaded if too much is on it.

I want to make sure to get the max draw correct whether this is in the US at 110V or Europe at 220V.

As a side question, the output rating on this supply is 19V, 3.42A.  Does that mean that it's pretty inefficient?


texts: Can I use dimmer voltage regulator for single phase multi speed AC motor?

texts: I have a swamp cooler motor which is single phase 3 speed motor, 1/7 HP i.e. 106 watts. I wish to reduce its speed (rpm) by 50%. Can I use this dimmer circuit to do so? This dimmer regulator is rated for 1000 watts exhaust fans. I only have school level electrical knowledge. I was thinking of connecting this dimmer regulator in between live (positive) wire, kinda like a ceiling fan regulator.


texts: Low power circuit that powers an LED but should not shock the human user

texts:
Need help making a circuit that requires very low current  so that in case a human comes in contact he/she should not be shocked. Also a small buzzer or Led needs to powered through this circuit. The aim of this circuit is that when two components on the machine come in contact with each other the user must become aware.Something that is similar to the continuity mode on a multi meter.I need to use a 5V 3A supply as it will be powering another component.

There is a possibility that the user of the machine may touch one of the components, the current should be so low that the resistance of the body should be enough. I would also like to know if I need to add additional resistors to drop the current further and also add a fuse so that in case anything goes wrong the fuse can break and the user is always protected.


texts: There is no math for adding the functions of two parallel filters. Or is it?

texts:
I want to add two "parallel" functions. Each of them describes the frequency response of that individual filter.
Put in other words, I want to see what the frequency response looks like when the two parallel filters are summed together.

Filter 1 is f(x) and filter 2 is g(x). So I go f(x)+g(x) must = the frequency response of the filters in parallel. No. Ofcourse not. Instead I get the frequency response of the filters added together like they were in series. Which they are, according to the math. Is there a solution for calculating (and graphing) filters that are in parallel?

I must be looking at the problem in a completely wrong way. The solution feels obvious and simple, yet, I cannot find it.


texts: Why does wire insulation have a working voltage and peak voltage?

texts:
I understand the concept of a wire having a working voltage and a peak voltage. My question is, physically why is this? What is happening?

I was under the impression insulators had a dielectric strength and when the charge across the two became greater than this strength it broke through? Does the peak voltage take longer to produce charge across the insulator?


texts:
I try to use IP core in Xilinx ISE 14.2. When the simulation done with ISim it works fine. Now I need to do the simualtion with ModelSim SE-64 10.7.

I compile HDL Simualtion Libraries Fig.1.

I run the simulation with ModelSim but it give me the error :
# Model Technology ModelSim SE-64 vcom 10.7 Compiler 2017.12 Dec  7 2017
# Start time: 18:17:16 on Sep 03,2020
# vcom -reportprogress 300 -explicit -93 ipcore_dir/CoreAdder.vhd
# -- Loading package STANDARD
# -- Loading package TEXTIO
# -- Loading package std_logic_1164
# -- Compiling entity CoreAdder
# -- Compiling architecture CoreAdder_a of CoreAdder
# ** Error: (vcom-11) Could not find xilinxcorelib.c_addsub_v11_0.
# ** Error (suppressible): ipcore_dir/CoreAdder.vhd(66): (vcom-1195) Cannot find expanded name
  "xilinxcorelib.c_addsub_v11_0".
# ** Error: ipcore_dir/CoreAdder.vhd(67): (vcom-1105) Name (indexed name) does not denote an
entity name.
# ** Error: ipcore_dir/CoreAdder.vhd(66): Unknown expanded name.
# ** Note: ipcore_dir/CoreAdder.vhd(108): VHDL Compiler exiting
# End time: 18:17:16 on Sep 03,2020, Elapsed time: 0:00:00
# Errors: 4, Warnings: 0
# ** Error: C:/modeltech64_10.7/win64/vcom failed.
# Error in macro ./tb_MYAdder.fdo line 23
# C:/modeltech64_10.7/win64/vcom failed.
#     while executing
# "vcom -explicit  -93 "ipcore_dir/CoreAdder.vhd""

The name of the toplevel is: MYAdder.
The name of the testBench is: tb_MYAdder.
The name of the ip Core in my project :CoreAdder.

Fig.1


texts:
I am working on a system similar to a 3D printer, which works with stepper motors, heated bed and an hot air fan. This system will work inside a chamber, with a temperature around 4 degrees and around 50% of relative humidity - These variables are concerning to me. I am wondering what measures should I take to avoid the condensation of droplets and effects related to ESD due to the humidity of the environment, which affects to the PCB integrity and can cause short-circuits.

Thank you very much for your answers,
Antonio.


texts: How to interpret a schematic in terms of input/output

texts:
I am programmer who studies electronics for hobby (but a serious one, not just for fun). I consider myself to have a reasonable knowledge on digital electronics. For instance, I already described processors, simple GPUs, network cards, RAM controllers etc in VHDL and then to a FPGA. Regarding digital electronics, this is the kind of knowledge that I have so far.

Now, I want to improve my knowledge in analog electronics. So far, I have studied: transistors, bjt amplifiers, opamps, RLC circuits, passive and active filters, simple linear fonts and some classical ICs such as 555 for instance.

But what I still missing is the ability to read and understand an anolog circuit schematic in the following sense: when I see a digital circuit schematic, it is easy to identify where are the inputs and the outputs, how data flow through the circuit and how each stage transforms the input signal. For instance, the following image is easy to reason in terms of inputs and output.

But when reading an analog circuitry schematic, I can't, yet, divide the schematic in blocks/parts by myself even with careful studying. For instance, the following schematic (a SPMS):

Because of so many in series and parallel conections and because current can flow in both ways in some parts of circuits it is hard to me reason in terms of input and output.

So here is my question: is there a way to read and interpret analog circuit schematics in terms of input/output in the same way that is possible to digital schematics (logic gates, for instance)? Or for analog circuitry there is another way of reasoning about the circuit? In other words: is there a systematic way, an algorithmic way, to read and interpret analog schematics or each circuit requires an ad-hoc analysis? Is there an abstraction that electrical engineers use?

What I have tried so far: to reason about a circuit using the abstraction of signals; try to split a circuit in terms of buffers (because of the input/output impedance) but this hasn't worked well so far because: not all circuits have buffers or work with signals. I've also tried to split a circuit by first looking at the IC's and then the discrete components around it. Then I would go on the IC's datasheet and read for instructions there. But this also didn't work for all cases because not all circuits have ICs.

My goals are: given a schematic, try to identify functional blocks: filters, amplifiers etc and; to be able to design (for me this is the most important goal) schematics of such complexity as the SPMS above. So for both cases I need to understand how one stage is connected to another.

I beg your pardon if my question is a little vague. As I said, I am a programmer, not an electrical engineer and I still lack keywords and concepts. If possible, please help me to improve my question.


texts: Chipquick SMD291 No-clean Paste Flux - Conductive?

texts:
I'm using this brand and type paste flux, and it works very well... except for one small problem. After assembling 5 prototypes, most had bizarre issues, which were resolved when the flux was removed via 91% isopropyl alcohol bath, soak, scrub, and dry.

Now this flux claims to be "no-clean" and "non-conductive", however the behavior was such that it was at least partially conductive. Some of the signal paths are very high impedance (10M ohms) but ironically, most of the problems centered around SOIC-28 and 100+ pin LGA components at less than 5 volts.

What's your experience with no-clean paste flux? Do they become at least slightly conductive after heating?


texts:
As a project for my electronics 101 class, I've been assigned to design a three stage amplifier using bjt transistor to achieve a gain of 150 and input resistance of 100k and output resistance of 50 ohms .I have tried to do so, but the result is less than satisfactory, I really need the help of an expert.(The question might sound basic to you,so sorry that I'm a beginner.)

I know for a fact that this circuit has many flaws. First of all the output resistance is not 50,It's 90. Secondly,The 200k resistance that I've used at the beginning of the circuit to make the high input resistance,dampens the signal,so in a sense, my circuit dampens the signal at first and then amplifies it. Thirdly, my dc sources are too many, I can make use of only one dc source,so this last problem is not really something that I worry about.And my gain is something about 105 which is not satisfactory.

1.I would really appreciate it if you help me on this.I think I should use a Common Collector stage as the last stage,but I have trouble configuring/understanding the output resistance of a common collector stage.

I have no idea how I should make the input resistance as high as 100k without dampening my signal.

3.Do you think the correct configuration to achieve gain of 150 is CE-CE-CC?

As I've said before,I would really appreciate your help.I'm pretty much clueless on how to even begin improving my design to match the specifics of the assignment.So any help, big or small is needed.


texts:
I am conditioning the input of a slowly drifting analog input sensor.

The sensor is a phototransistor that will sink a small amount of current when "dark" and 50x more current when "bright," but the ambient brightness will vary, so a pre-set "trigger threshold" is not good enough.

Based on this I have an incoming voltage with source impedance < 10 kOhm. I want to detect when the voltage falls "quickly" to less than half what it was before, within reasonable range for "previous" value (say, 1-2.5 Volts with 3.3V supply.) Let's say that a typical value of "quickly" is "10 millisecond fall time."

Would an opamp with a RC filter on the negative input, and a moderate feedback resistor to avoid overdriving it, plus a Schmidt trigger for conditioning the output, work alright? See the schematic in the picture.

(Note that the calculated corner frequency for the filter assumes a 0 Ohm source impedance, and the corner frequency will go down if source impedance is higher, which would be fine by me!)


texts:
Why does the automotive industry sticks with 5V sensor outputs instead of something like 4-20 mA? Wouldn't it be a solution less prone noise?
What are the advantages in using a 5V output instead of a current signal?


texts:
Question: Is Quad SPI really a serial interface, a parallel interface or both?

The image below depicts that independent databyte may not be able to send over individual lines (I see databits spread over multiple lines) making them "not 4 independent serial interface".

Another image from STM MCU below.

last snapshot of serial interface tag in EE.SE

EDIT: The question here is different from mine. The question deals with the different topologes of SPI while my question is on Quad SPI in particular and to identify clearly the interface nomenclature.

It is only to gain better understanding on how we classify the serial and parallel interface in case of Quad SPI. This is a discussion which has arised many times but could not be answered well enough by me.


texts: Phase control up to 40A with TRIAC and DIAC (Optocoupler)

texts:
I'm projecting a phase control to control the power given to a resistive load of 6 Ohms using a PLC, TRIAC (BTA40-400), DIAC (Optocoupler MOC3023) and a zero crossing detector (4N25).

I've simulated the circuit on Proteus Isis (circuit bellow) and I get an error. This error disappears if I set the resistor R2 upper to 5k Ohms but I did not get the expected current and voltage at the load (around 37A and 220V).

simulate this circuit – Schematic created using CircuitLab

After that I realised maybe the answer is: The current through DIAC is higher than supported by it. (Is it?)

What's the current passing through this DIAC when the TRIAC is disabled? (37A?)

How could I make it working at the simplest way?


texts: Does propagation delay in an opto isolator sum with switching time in a FET?

texts:
Optoisolators such as the Vishay VO3120 list a "propagation time delay time" of 0.4 microseconds. Common FETs such as the IRFZ44N list a "Turn-On Delay Time" of 12 nanoseconds.

Normally I use the turn on/off times of a transistor to determine the maximum permissible switching frequency for the component, as well as the appropriate dead time.

When doing such calculation for a FET driven through an optoisolator do I need to sum the values from both datasheets? Or does the signal from an optoisolator just get time shifted? If the signal is time shifted, can I ignore the time shift if all switching components are driven through equivalent optoisolators?

Datasheets:
http://www.vishay.com/docs/81314/vo3120.pdf
http://www.infineon.com/dgdl/irfz44n.pdf?fileId=5546d462533600a40153563b3575220b


texts:
I got this broken Varistor from an Eaton3S 550VA 300W UPS.
Marked TVR 20471*
I have tried my best to find a replacement but I can't find a similar one. Any tip or recommendation for a similar one that will work for a UPS would be very appreciated.


texts: Matching a transformer to one in a video balun - Vertical sync is off

texts:
I building an interconnect board which will hold one side of the video balun pair (plus power and rs485). The other side will be a commercially available video balun which connects to the camera.

Right now I am having trouble matching the two sides.

I ordered three coils from coil craft - PWB3010LB, PWB-1.5-ALB, and WB1010-SMLB

All of them transfer the video, but the vertical sync is off by ~40%. the colour is slightly off (a little bit pink), but otherwise the video is fine! :)

What does the vertical sync problem indicate?

Thanks!


texts: Why does the solution to the wave equation define two directions?

texts:
I've been studying transmission lines recently and I'm struggling to reconcile my intuition with the derivations.  Take the form of the general solution to the wave equation given on this page antenna theory (a great resouce, by the way) and here it is:

You'll find these formula in many texts and all over the web.  A particularly good derivation is given by the (equally suave) Roger Moore (https://www.youtube.com/watch?v=ayrbIgq_5Ck).

However, when I think of waves travelling down a line, I think of them travelling in a single direction.  I understand that they can be reflected and travel in the opposite direction and so, are free to move in either direction.  In the initial part of the derivation given by Roger, the assumption is made that "the total displacement from equilibrium" is given by

$$f\left ( x - ct \right ) + g\left ( x + ct \right )$$

and the general solution simply falls out of this initial assumption.

But, I'm struggling to see this.  How can the wave be defined to travel in both directions at once?  Or is it that the solution allows for the possibility of one direction or another, in which case V- or V+ is zero.  I can see how the solution might work for waves crossing (superposition), but then aren't they two separate waves??  Confused!


texts: PIC32, XC32, timer interrupt vector not entered

texts:
I have the below timer 5 interrupt vector that is not entered, even when both the corresponding Interrupt enable bit for timer 5 is set, and the corresponding interrupt flag for timer 5 is set.

Here is my interrupt vector handler:

void __ISR(_TIMER_5_VECTOR,IPL4SOFT) _T5Interrupt(void)
{
    PORTDbits.RD2 = 1;  // << -- LED will light when here.
    T4CONbits.ON = 0;
    TMR4 = 0;
    TMR5 = 0;
    Global_TimeOut = 1;
    IFS0bits.T5IF = 0;
}

My global interrupts are set to accept multi-vector interrupts and is initialized as follows:

void Init_Global_Interrupts(void)
{
    // Initializing Global Interrupts
    //INTCON
    // 16 Single Vector is not presented with a shadow register set
    INTCONbits.SS0 = 0;
    // 12 Interrupt Controller configured for multi vectored mode
    INTCONbits.MVEC = 1;
    // 10 - 8 Disables interrupt proximity timer
    INTCONbits.TPC = 0;
    // 4 External interrupt 0 falling edge interrupt
    INTCONbits.INT0EP = 0;
    // 4 External interrupt 1 falling edge interrupt
    INTCONbits.INT1EP = 0;
    // 4 External interrupt 2 falling edge interrupt
    INTCONbits.INT2EP = 0;
    // 4 External interrupt 3 falling edge interrupt
    INTCONbits.INT3EP = 0;
    // 4 External interrupt 4 falling edge interrupt
    INTCONbits.INT4EP = 0;
}

Timer 4 and timer 5 is being used in 32 bit mode. As the data sheet states, in this configuration, it is timer 5 interrupts that is used:

void Init_Timer4_5(void)
{
    // 15 - Timer 4 is off
    T4CONbits.ON = 0;
    // 13 - Continue operation when device enters idle mode
    T4CONbits.SIDL = 0;
    // 7 - Gated time accumulation is disabled
    T4CONbits.TGATE = 0;
    // 6 - 4 - 1:8 prescale to achieve a 1uS unit time
    T4CONbits.TCKPS = 3;
    // 3 - Timer 4 and 5 set for 32 bit operation
    T4CONbits.T32 = 1;
    // 1 - Use internal Peripheral clock
    T4CONbits.TCS = 0;

    // Setting Timer 5 priority to level 4 of 7
    IPC5bits.T5IP = 4;
    // setting timer 5 sub priority to level 1 of 3
    IPC5bits.T5IS = 1;
    // Clear timer interrupt flag
    IFS0bits.T5IF = 0;
    // Enable timer interrupts
    IEC0bits.T5IE = 1;
}

The timers are started with the following function:

void Time_Out(unsigned int uTime)
{
    T4CONbits.ON = 0;
    TMR4 = 0;
    TMR5 = 0;
    Global_TimeOut = 0;

    PR4 = uTime;

    T4CONbits.ON = 1;
}

As far as I can tell, I have done everything necessary.

Let me know if you require any additional information.


texts:
Sometimes it cannot be avoided to run traces over a ground plane (bottom layer) in a two layer PCB.

I have two questions regarding this:

In the (simplified) example below, what is preferred? To use two small vias, minimizing the interruption of the ground plane (R1 to R3), preventing ground loops, but having more vias, or using a large line via the ground plane (r2 to R4)?
In most cases I can chose to have either a VCC line (5 or 3.3V) or a signal line (MIDI, DMX, 31-250 kbps) run over the ground plane when needed. Is there any preference?


texts: Use of UC3843BD1G for current measurement

texts:
I was trying to develop an accurate current measuring circuit. So I opened up a multimeter for some reference. In which I found this UC3843BD1G Current Mode PWM Controller. Can this chip help me in building the current measuring circuit?

I am not able to understand the precise use of this  UC3843BD1G Current mode PWM Controller chip. The datasheets also confuse me.
Here's a link to the datasheet. UC3843BD1G datasheet.

Can someone explain to me what is its actual use?


texts:
According to this document, I need to:

 assign 0 MHz toggle rate to Toggle Rate assignments for the pin in the Assignment Editor

to place a non-differential pin close to a differential one. However, when in the Assignment Editor, I cannot find "Toggle Rate" as an appropriate Assignment Name. (There is a long list of possible assignments, but none is called "Toggle Rate".)

How can I assign the toggle rate in Quartus II?


texts: Rc crawler - make it faster/longer range?

texts:
Apologies as I am on a phone at work - but obsessed so here we go hah.

I bought a rocksta crawler, from hobby king. Cool for what it is. But it's deathly slow. Like 25cm/second. Its a great crawler but is there any way to make t faster?

https://hobbyking.com/en_us/basher-rocksta-1-24-4ws-mini-rock-crawler-rtr.html

I'm assuming it's either the motor, gearing, or battery maybe that would need to be upgraded. Or all three. I would really like to see if it's possible to make this faster. It doesn't need to be massively fast. But I'm interested to see what options there are.

Also, if I wanted to extend the range on the transmitter - after some quick phone googling it seems I need to upgrade antenna and a transistor to increase power to antenna / rx?

I'm fairly new to hobby rc / electronics and any advice is appreciated.

Links or even direct advice or anything I can research or to look into specifically later this evening.

Thanks


texts: ( How-To ) Ultra Low-Profile PCB Stacking

texts:
Recently I found myself needing to stack two small circuit boards on top of each other for a modulation project. The problem is that the areas I want to connect together on the two boards have no components or traces on them, and traditional pin-style stack ups (even machine headers) leave an unwanted gap between boards.

How can I stack the boards flush with on another and have a minimal gap between them?

I have seen This Question which shows an approach to stack boards permanently flush together, but I need a solution that is removable.


texts: Problem with simulation of a n- mosfet in pspice

texts:
Im trying to make a simulation based an a DC sweep from this circuit

But at the moment of simulation I receive this warning

WARNING:  [NET0093]
No PSpiceTemplate for M4, ignoring

And it does not plot any data or traces, Indeed the simulation runs as for the parameters given, but how can be corrected the warning.
The model is from the EVAL.lib for spice. IRF150 a n channel mosfet.


texts: Why are ground pours isolated from each other on the top layer?

texts:
I am reading the application note from TI about the LM3409 evaluation board.
In the board layout (Figure 3) the bottom layer is a single GND pour.

But top layer has also some copper pours which end up being connected to ground, such as the ones at LED-, C5, D1 and C1.

What I don't understand is: why are they all not connected to each other on the top layer, since they are all the same net ?


texts:
I want to know the purpose of connecting a resistor in parallel to an LED. the schematic below is a part of microchip's Explorer 16/32 Development Board. Full schematic can be found here

The LED's partnumber is QBLP631-IG. the nets P91_LED9 and P92_s5_LED10 are connected directly to the microcontroller's input/output pin and is driven at 3.3V. The jumper is used to isolate the LEDs circuit if needed and use the input/output pins for other purposes (the nets mentioned before are connected to an expansion header).

My thoughts are: maybe the parallel resistor is connected so that if the microcontroller's pin is not configured, the default state is to be used as an input, and hence the resistor is to prevent this pin from floating and connect this pin to ground (by the 36k+2K resistors). floating inputs are unhealthy for a microcontroller.But again, who knows...


texts: What is vector potential in magnetic field?

texts:
The vector potential in magnetic field (represented by A), what does that physically mean? I have serious problem in understanding it intuitively.

$$\nabla^2\text{A} = -\mu_0 \text{j}$$

I read that the above equation can be derived using continuity equation. Can it be derived? if possible how? Thank you.


texts: How to solve resistance in this circuit?

texts:
I need to find R(AB). It is resistance across terminals A and B.
I really do not know how to solve this kind of circuits. Maybe I have to use transforming from triangle to star? But it is quite inconvinient.
I noticed that on the right side 1 kOhm and 2 kOhm resistors are series. We add them and get 3. But what's next step?


texts: How to write the transient analysis ltspice directive with a stop time and start saving data time?

texts:
How to include 0.9m start saving data in spice directive?

.trans 1m


texts:
I want to toggle the LED3 of the microcontroller when the button SW0 is pressed. I developed this code but it is not working and I dont know what is wrong. I search in the documentation and many foros trying to find the error but I still dont know what is wrong. I think the problem is in the confguration of the interrupt, but I am not sure about this.Can someone help me? Thank you.

int main(){
    EIMSK = 1<<INT0;                    // Enable INT0
    EIFR = (1 << INT0);
    MCUCR |= 1<<ISC01 | 1<<ISC00;   // Trigger INT0 on rising edge
    DDRB = 0x04;//Set port B LED3 as output the other pins as input
    PORTB = 0x04; //Pin3 that is output/led turn off, input pull up

    DDRD &= ~(1<<PIND2); // Set PD2 as output (Used for interrupt INT0)
    PORTD = 1<<PIND2; // Enable PD2 pull-up resistor

    sei();  //Set global interrupt flag, to allow SW0 interrupts

    while(1) {}; //Infinite loop to wait for the interrupt
    return 0;
}

ISR(INT0_vect) {
    PORTB ^= 1 << 3; //toggle LED3
}


texts: Meaning of dB units in periodogram (FFT)

texts:
When I calculate spectrum of a voltage signal using FFT and then I calculate periodogram using
$$S_k=10\cdot log_{10}(\frac{1}{N}|X_k|^2)$$
where \$X_k\$ if the result of FFT and \$N\$ is number of samples, the resulting graph usually has "dB" on vertical axis. But what is the meaning of dB in this context?
Decibels usually refer to either power (dBm) or amplification/attenuation or multiple of some reference value. But in this case, it seems to me that it is neither of these.
It linearly depends on the number of samples (Because the result of Fourier transform is linearly dependent on \$N\$, then I square it, but only divide by \$N\$).
So is it somehow proportional to the energy of the signal? If so, how is voltage converted to energy/power? It would require some impedance value to get power from voltage. Or should it be somehow normalized (is there a definition of what 0 dB should mean)?


texts: Why do they put some optocouplers in 6-pin packages?

texts:
Example:

It is obvious that an optocoupler which provides a pin for the base of the internal transistor (e.g.; PS2621) cannot be in a 4-pin device. My question is not about this kind of optocouplers. But, an optocoupler which gives out only the collector and emitter pins (e.g.; PS2622) can be implemented in a 4-pin device. Yet in electronics, it is important to make the smallest possible design to save space and material cost. Why are 6-pin optocouplers so common in the market? Is there a reason for putting them in 6-pin packages?


texts: A device like a Peltier cooler which transfers heat to another surface not in direct contact with the cold side?

texts:
Back when I was a kid and first learned about Peltier coolers, I mistakenly thought they had the ability to transfer heat remotely from one surface to another via wires.  I didn't realize the heat transfer took place within a set of PN junctions in a substrate, and basically just moves heat from one side of the material to the other.

I was wondering if the concept of "transferring heat to a remote surface via wires" is valid?  In other words, like a split thermoelectric cooler with the cold side at one location and the hot side at another location, connected by wires, using electrical current to "push/pull" heat from one place to another

Or is this a better question for the physics site?

Or is this just stupid? :)


texts: coding using Arduino, two 74HC595 and two RGB LED, problems with shifting out database

texts:
the whole point of this was to be able to send 8 bits of color code to 2 rgb leds through 2 74hc595 registers. if i can get the default color for each led to be sent out then the next part of code is to have a user interface to let someone select which led and what color they want. so now trying to shiftout default colors to these 2 leds. when it compiled i got no shifting leds did not change. like i said i am a noob at this stuff.

#include <arduino.h>
const int ledred = (char)0x80;
const int ledgreen = 0x20;
const int ledcyan = 0x28;
const int ledyellow = (char)0x0A0;
const int ledwhite = (char)0x0A8;
const int ledblack = 0x00;
const int ledvoliet = 0x44;
const int ledblue = 0x08;

#define step1 1
#define step2 2
#define step3 3
#define step4 4
#define step5 5
#define step6 6
#define step7 7
#define step8 8

#define led1 1
#define led2 2
#define led3 3
#define led4 4
#define led5 5
#define led6 6
#define led7 7
#define led8 8

char display_step;
char i;
char c;
char str[80],sstep,lamp,color;
int done;
char colors [8][7]={
  "Red   " ,"Green"   ,"Cyan  "   ,"Yellow"  ,"White "  ,"Black "  ,"Voliet"  ,"Blue  "};

char database[56]={
  8,ledred,ledgreen,ledcyan,ledyellow,ledblack,ledwhite,
  7,ledvoliet,ledblue,ledwhite,ledyellow,ledcyan,ledred,
  3,ledred,ledred,ledred,ledblue,ledblue,ledblue,
  5,ledred,ledwhite,ledblue,ledred,ledwhite,ledblue,
  9,ledgreen,ledblue,ledvoliet,ledyellow,ledcyan,ledblack,
  4,ledblack,ledblue,ledblack,ledyellow,ledblack,ledcyan,
  6,ledwhite,ledblue,ledgreen,ledvoliet,ledcyan,ledyellow,
  10,ledgreen,ledyellow,ledblue,ledred,ledblack,ledblue};

char numberlamps=2;
char numbersteps=8;
const int data = 9;
const int clock = 10;
const int latch = 8;

int main()
{
  pinMode(data, OUTPUT);
  pinMode(clock, OUTPUT);
  pinMode(latch, OUTPUT);
}

void loop(){

    int index;
    int i;
    int updateLEDs;
    int lampvalue;

      display_step = 1 + display_step%numbersteps;
      index = (display_step - 1)*(numberlamps + 1);
      time = database[index];
      for( i = index +1; i < numberlamps  ; i++);

      lampvalue = database[index];
      digitalWrite(latch, LOW);
      shiftOut(data, clock, MSBFIRST, lampvalue);
      digitalWrite(latch, HIGH);

  }


texts: How to do a specific task after some time

texts: I have to switch on one relay after some specific time, but at same time I have to do continuous polling for controlling other relays, I am already using interrupt for multiplexing purpose (7 segment display). How can I accomplish this?


texts: Trigger input with varying input voltages

texts:
Currently I am trying to build a circuit, with the goal of triggering a pin of an ESP8266 from varying input voltages (in the range of 5 to max 15 volts it should get triggered). Also the input should be seperated from the ESP.

What I was thinking to do was:

Use an optocoupler for the input voltage (currently thinking about the pc817)
Calculate the resistor so that min voltage and max voltage would work (current range of the pc817 is 20mA - 50mA, and Voltage Range is 1.2 (standard) to 1.4):

15V: (15V - 1,2V) / 0,05A = 276 ohm (already calculated for absolute max current)
5V: (5V-1,2V) / 0,02A = 190 ohm

So which resistor should I use to allow 5-15V in this optocoupler? Or is there any better circuit option/better optocoupler that allows something like this to be achieved?


texts:
I'm often confused what the meaning of 'speed' is in analog circuits. To me it seems that the higher the cutoff frequency, the 'faster' the circuit is. In other words, a higher frequency input signal can be processed.

The reason I'm confused is that I just read about the 'speed' of an analog circuit being affected by the current. To my knowledge, the current doesn't affect the time constant (R or C) and as a result doesn't affect the bandwidth, so how can for e.g. greater current result in a 'faster' circuit? Is it something to do with the rate of change of capacitance voltage increasing i.e. \$I_c = C\frac{dV_c}{dt}\$ ? Is this related to the slew rate?

Could it be that a higher current increases the transconductance and therefore the unity-gain bandwidth?

In the digital world, the meaning of speed is very straight-forward but there seem to be too many different meanings of speed in the analog world.


texts: Looking for elliptical display or modular display to approximate ellipse

texts:
I'm not very fluent in electrical engineering so please bear with my imagination.

Requirements: Photo realistic display, touch screen, approx 7x3 feet (2.1 m x 0.9 m).

Option 1: Do elliptical displays exist? Whether it be a tv or monitor or whatever. I feel that it may be possible to build such a display but there being no demand they simply are not built. Is there a company I could approach that could custom build such a display?

Option 2: are there rectangular modular displays that I could interface together to approximate an ellipse? Preferably with as little separation between each display as possible to mimic a larger display. And so that the images on the 1 display can flow smoothly between all the displays?

Sketch below: Inner ellipse is desired display area. Rectangle represents a normal retangular display. The 4 corners of the rectangular display can be seen sticking out from a 4 inch bezel shown here. The bezel would have to be about twice as wide to hide the corners. Which is an option but becomes a fairly large bezel.


texts:
I am working on a project with two inputs and an output as shown. IN2/OUT are external connections, and IN1 is internal. Based on input from this forum and research I have come up with the following common-mode filter for placement between IN2 and OUT. (L1&L2 are actually the same CM choke, just drawn separate.)

I've calculated and simulated this as shown:

I'm happy with both differential and common-mode response, but I've only simulated the filter in common-mode without any load, as I don't exactly know what to use for a load when simulating CM filters. So my questions:

1) Does this topology look ok with the way the circuit is supposed to function (shunting CM cable noise from IN2 and OUT out of the circuit?

2) When simulating CM filtering, what is usually used as a load? I watched a youtube video where a current source was used to simulate the filter, but I didn't fully understand the reasoning behind it.

3) This may be a brain fart question, but is there any useful significance to simulating filter frequency response without any kind of load, since the source and load will change the frequency response? I was reading a post about PI filter analysis, where differential filter response was said to be meaningless without source and load attached.


texts: How to chose between 9V or 12V (or others) DC power supply

texts:
I see a lot of devices working either with a 9V DC input or a 12V DC input, usually provided through a DC jack connector. I was wondering about advantages and/or inconvenients of both voltages.

Indeed, most of the time, this input voltage goes almost directly through a regulator providing 5V or 3V3 to the rest of the circuit, supplying current for MCU and other components.

Then, why a standard has not been adopted to fix the input voltage to one of those two voltages and also, why is it 9V and 12V in 90% of the cases ? (I have never seen a PSU delivering 10V, 8V or others).

I do think there is something to do with efficiency and dissipated power in power supplies and/or regulators but I can't really answer the questions above.


texts:
Im building a project that does not involve any transformer.

Without using any transformer, what elements or components (in the question mark above) can you use that can reduce the voltage from say 120V to 85V after it?


texts: Best practices in making cable schematics

texts:
I would like to make cable schematics for manufacturing that would include:

cable lengths
connectors
pins
conduit length
heat shrink tube length

and have a BOM for that automatically generated in Altium/Eagle. That that would require every element to be a separate component. Is there a set of commonly used symbols for them? How do you produce such documentation in your projects?


texts: In this low side switching schematic does the 10k resistor play any role?

texts:
I've been given this schematic to review it (I'm working on a formula student team.) It is used for cutting off the power to a motor through a N-mosfet (NCV8402A).  The 12V are being supplied through a battery.  The motor will be connected to the connector on the right.
I had a disagreement with the team member that made the board about the use of the R6 resistor. He told me that he used that resistor as a "pull up" to avoid the situation of the pin number 2 floating when the transistor switch opens. I told him that I don't agree because you can't define a pull up resistor without having a ground at your circuit and that the main reason for using a low side switch is for the ground pin to actually "float" because it is an open circuit.  I also told him that in normal operation 1.2mA of current will flow through the R6 for no reason.
Who is right?


texts: Differential ADC and Common Mode Voltage

texts:
I am trying to understand a little bit more about common mode voltage. I am working with a particular MCU, the TMS320F28377S, and it has a common mode voltage requirement for its positive and negative input when using its 16-bit differential amplifier mode.

My V_REFCM is 1.5V (V_REFHI = 3V and V_REFLO = Ground) so according to this requirement table, I understand that my common mode voltage of my inputs needs to be 1.5V as well. I am wondering however, if my inputs to the ADC are not AC and for instances, DC. If I had for example, a negative input with 1.5V DC and then a positive input of 3V, would that mean that my negative input would satisfy my common mode voltage requirement and my positive would not? Would a 3V DC signal be the same as a 1.5V common mode voltage with 1.5V amplitude? I was wondering if someone could help point me in the right direction. I feel like I might be wrong because in the technical reference manual for this MCU, there is this note that states the common mode voltage is the average of the positive and negative input. This would mean that if I had 3V and 1.5V inputs, my ADC input signal common mode voltage would be 2.25V.

A bit more of specific question now, I was wondering would type of issues would I run into if my common mode voltage doesn't satisfy the electrical data requirements. I am assuming my reading will be inaccurate but I wondering why?


texts:
So I'm writing drivers for DMA for transmission for now and running into a few issues.

So I am transferring bytes from memory to UART peripheral with a threshold of FULL_FIFO so I reckon it would fire an interrupt upon draining the entire FIFO to UART's DR register, but the following is what I see:

My buffer size is 30, and hence NDTR register is set to 30. From what I've read in the reference manual, NDTR decrements after each byte transfer. The moment I enable DMA, I see NDTR's value is set to 13.
The moment right after enabling DMA, I see the first three characters sent out. So my buffer contains SENDING DATA, and I see SEN being sent out when I start the program, and another SEN after enabling the DMA.
After enabling DMA, I also see UART's TXEIE, and PEIE being set -- which I think makes sense since that's how DMA will talk to UART (transferring byte from a FIFO to UART's DR every time TXE is set) I reckon. But then I wonder how come the first 3 bytes were sent out with UART interrupts disabled?
I then see the program getting stuck in UART's IRQ Handler
Also, after DMA is enabled, I see DMAT gets reset. I didn't see anything related to that in the RM unless I missed it

I have spent quite some time reading up the RM but maybe I seem to be overthinking a lot now. Any help is appreciated.

STM32F401RE NUCLEO BOARD

Edit:

I now see NDTR getting set to 0 after DMA enable even though I don't see ALL the bytes being sent in serial.


texts:
I am asked to find the h-harameters for this op amp:

I found the gain to be 1.87*Vi (where Vi = the input source). However I don't know how to do two port parameters with op amps, we've only covered basic circuits (Resistors, inductors, and capacitors.)

How can I find the h-params of the circuit above?


texts: What is the risk in unplugging a USB device without disconnecting it in the OS?

texts:
I see people unplug a USB e.g. External drive from the port without flagging/ejecting it from the OS first.
What are the risks in disconnecting a USB device in the middle of a transfer? Could it damage my hub controller, or blow-up my motherboard or such?


texts: Calculating an First Order RC Circuit Time Constant

texts:
I apologize for the basic nature of this question, I am trying to figure out how to calculate the RC Time Constant of this circuit

I know you have to approach the circuit from the capacitor to find its time constant.
I think the Req would be R1 + R2 + (R3||R4) because when finding Req for the Capacitor you just open it, but am very confused and not entirely sure.

Any help would be huge!


texts:
I plan on using this 3.3v regulator

It has 4 pins on the SOT-223 package

I plan on doing the following ( but want to check )

Pin 1 - Gnd
Pin 2 - Vout - 3.3v -- Tied to pin 4 feeding my circuit
Pin 3 - Vin - 5v Supply
Pin 4 - Vout - 3.3v -- Tied to pin 2 feeding my circuit

Does this look correct?

The reason I act is that pin 4 is a bit 'odd'. This question has set me straight : LDO - SOT223 - What's the Fourth pin for?

Basically its a tab for heatsinking, but it is typically connected to Pin 2.

Can I therefore safely just have a pad for the Tab(pin 4) with nothing connected to it? And use pin 2 for the vOUT alone?


texts:
I've got bunch of spare HDA & AC97 codecs from mobos, is anyone was able to interface to them from usual ARM uC? Is it even possible?

Googling didn't helped me much. Any hints?


texts: State Machines - What happens to 'Don't Care's in the Output?

texts:
This is referencing the article about state machines on allaboutcircuits.com
In their state table, they have a 'Don't Care' listed under the output for the state 11.

However, in their k-map of the output column, they listed a '0' under 11, instead of a don't care. Why is that?

The article in reference: https://www.allaboutcircuits.com/textbook/digital/chpt-11/finite-state-machines/


texts:
I am trying to build a bldc controller.
I have the following schematic
I should mention that for the gate drivers I used ir2101 ICs. Everything works fine but when I connect the motor (350w hoverboard motor, the VBAT+ is 36 volts) the motors spins but I have to disconnect it because the mosfets get really hot. Without the motor the mosfets don't heat at all.
Any suggestions would be appreciated.
EDIT: the problem was because of low side gates didn't turn off fast enough. If you have the same problem try to put an "anti-paralel diode" on the low side MOSFETS. The diode should be a Schottky one (fast diode).


texts:
I need a circuit which outputs a LOW level on power-up state. INPUT stays LOW. Once INPUT goes HIGH I need to run a delay which will set OUTPUT to HIGH  after timed delay T (which is measured in seconds, should be configurable within 1-20s, accuracy aren't important). OUTPUT should stay HIGH until complete power-off. Rest INPUT level transitions are ignored. Like this:

TTL levels. I've did it this way in simulation with 7474 trigger and 4584  inverting Schmitt trigger:

The only difference that button LOW level triggers transition, but it can be inverted with other inverter IO on same 4584 I guess.

Will this work in real hardware or maybe someone could suggest a better circuit for my needs?

EDIT: Based on @elliot-alderson answer, I've modified my schematics to make sure both flip-flops will output LOW level at power on and no inputs are floating:

I've also changed button position to simulate original low-to-high transition input as drawn on my 1st diagram.

How about this version?


texts: Arduino UNO disconnects from computer when connecting it to a breadboard from specific holes

texts:
I am a complete beginner in electronics; I started learning using Arduino yesterday.

There is something strange happening with the Arduino UNO board.

The Arduino board is connected to my laptop and it's working fine (the green LED is on), but when I connect a breadboard with the Arduino's 5V pin and GND pin, the Arduino board disconnects from the laptop and turns off(green LED turn off), but the strange thing is that this problem only occurs if the Arduino's 5V and GND pins are connected to the breadboard from two columns:

If the breadboard is connected to the Arduino board from any combination of two row different than the one in the image everything goes fine, even if one of the wires is connected to one of the columns in the image and the other one isn't the problem doesn't occur.

So why is this happening? And why does it only happen with a specific combination of two columns in the breadboard? Is it even a problem, or is it just a normal thing?

Picture of another combination of columns:
(Notice the green LED is on so there is power and it's connected to the laptop)


texts: What are the typical uses for a non-inverting quad buffer IC?

texts:
Do excuse my lack of knowledge on the subject, but on the Opendous JTAG schematic there are two 74LCX125 IC's. The datasheet refers to them as Low Voltage Quad Buffers, but I don't fully understand what the purposes are of these chips in the Opendous JTAG circuit.

Also, what are other common uses for these ICs?


texts: What type of three-phase connection does my shop have?

texts:
Yesterday, I wanted to test some MCBs and power supplies that I had just received. Since we only have one 480V socket in the shop, I asked my coworker if I could use the power source he was using. He went with me and unplugged his (working) PLC system which used a 3 pole MCB powering a 24VDC power supply. His parts are nearly identical to the parts I'm testing.
I took an identical power cable we had and wired in three of the wires to one of my MCBs. I left the remaining green wire that had a ring terminal on it unconnected.
When I plugged in the cable and measured the voltages at the MCB, I was confused at the measurements. If we call the three phase wires A, B, and C, and the green wire D, then these were the measurements I made:

Probe
Probe
Voltage (VAC)

A
B
225V

A
C
475V

A
D
250V

B
C
246V

B
D
33V

C
D
238V

We're in western Canada, and I've heard that some systems use a "high leg", but I don't think that's what we have here. I also read about "corner grounded" and "open" delta systems, but I don't know if that's what we have.
What kind of distribution system is this?
Given that my coworker's system hasn't malfunctioned, it may be safe to say that I can simply treat it as a 480V three-phase connection and not worry about how it works. Is this stupid?


texts: How can a transistor amplify current in a circuit?

texts:
At 2:57 of this video, it is said that when we apply a small current to the base of the transistor, a large current is passed through. This is fine, but what bothers me is what he says right after: "If we now manipulate the base current in a certain change, the other current changes proportionally with much higher amplitude"
I just can not understand why it is that variations in the base current should amplify the current through the transistor. If I am understanding correctly, if we apply a current on a transistor, then we simply decrease the size of the depletion region and hence make it more conducting. However when we do this, the transistor didn't really amplify any signal, but rather let more of the current pass through.
So, why is it that we say a transistor is working as an amplifier here? Or am I misunderstanding?


texts: How can I make a two voltage source, 4-layer PCB in Eagle?

texts:
I would like to make 2 different voltage sources on one layer (layer 15).
In the picture, the left rectangular area is a 5V polygon and the right one is 12 volts.

Is it possible? How much distance should be between the two voltages?


texts:
I have two different boards, one from TI and one from ST Microelectronics.
Both these boards have one accelerometer of different brand.  These two accelerometer sensors have different sensitivity.

I take the boards and give each a sudden upward and downward motion, one by one.

I get two graphs for such motions, which shows me the point on time axis where the sudden motion was imparted.

Ultimately I have to find cross correlation of these two data.  In theory the cross correlation should have a high peak, because I gave same kind of motion to the two boards.

My friend says I should first normalize by energy. Can someone help me understand what do we mean by normalization with respect to energy? I guess it is something about making the two data  equivalent so that an apple::apple comparison can be made.

Can someone help me understand this normalization?


texts: Advice on cleaning up 5VDC from a wall-wart

texts:
Assumption: I think it's generally true that commercially available AC/DC wall-worts can be expected to be pretty noisy (e.g. you can't count on much better than 5% stability).

Background: I'm dorking around with an RF application right now, and I hypothesize that some significant subset of my headaches is coming from powering my RF receiver with 5VDC coming directly from an AC/DC wall-wart (i.e. no RF choke, no regulator, nothing).

Question: What's the simplest way (e.g. fewest parts) and cheapest mechanism for converting the "angry" 5VDC off a wall-wort into a "happy" 5VDC for my RF receiver? I think the other subsystems are more tolerant to noisy power.

Aside: I wish I could give more definitive characterization of the noise coming out of the wall-wart, but sadly I am sans o-scope.

Edit1: In response to the request for more detail on parts being used:

Wall-Wart
RF Receiver


texts: Light bulb and current limiting resistor

texts:
I am currently interning at a science educational center and for my project, I am creating a simple and educational circuit using batteries, resistors, and light bulbs. The purpose of this circuit is to educate elementary school kids on the concepts of series and parallel circuit. By flipping the switch, they can distinguish the the difference between resistors connected in series and parallel by comparing the brightness.

All 4 resistor values are 1K with 4.5V as input. The specification of the light bulbs are 1.5V @ 0.3A. I have tested all the light bulbs (without resistors) and they are all fully functional.  The schematics is shown below.

However, the bulbs that are connected to the resistor do not light up. When I used the multimeter measuring from B to point A, it reads 4.5V and when I tried to measure from point A with respect to the ground, it reads 0V.

I know this violates KVL as Vf = VR1 + VR2 + Vb. I cannot figure out why I am getting 4.5V drop through the 2 resistors instead of the 2 resistors plus the bulb. I also tried to up the voltage by using a 9V battery, but the results came back the same. Could it be because the light bulbs are not compatible with resistors?

Thanks in advance.

(Note: My supervisor prefers light bulb over LED even though I tried to convince him to use LED...)


texts: How to determine LV CMOS output impedance?

texts:
I've successfully been using this circuit:

to generate a +13 dBm sine output (the frequency is 10 MHz). The NB3N551 has an output impedance spec of ~20Ω or so, which means the input to the pi filter matches.

I've been trying to do the same thing, but instead of the NB3N551 using a 74LVC2G04W6-7 output. I've tried varying R1, but the output doesn't look at all like a sine wave. It looks more like a square wave, but with slower rise and fall.

What is the 74LVC2G04W6-7's output impedance (Vcc is 5v)? How can I figure that out from the datasheet? Is it just too high for this purpose?


texts:
I've been checking some online calculator (this one and this one) to determine the width of a PCB trace for a given current capacity, but I not sure if the value specified for current refers to direct or alternating current.

Do these calculators assume one type of electrical current or is the result applicable to both?


texts:
I wonder why debug probe can vary so much in price?

Here a example. You got probe ranging from 99$ up to 1500$. What are the functionnality that a 1500$ probe offer compare to a 99$. Sure, I saw that TCK can be higher on a 1500$ probe 50 Mhz compare to 1 Mhz on the 99$. But is it relevant? Do company use debug probe on manufacturing chain of electronic? Therefore, having a lot faster probe could result in potential gain of productivity?


texts: Voltage regulator vs. voltage controller

texts: I frequently meet the references to voltage-regulators and voltage-controllers. However, looking at the specs I find them to perform the same function. Is there a difference between the two, or regulator/controller can be interchanged?


texts: MCP73831 charger - how to control low voltage cell

texts:
Does the MCP73831 have a way to set a protection to shut down the main output if the supply voltage is too low?
I would like to implement (without coding) a protection which disconnects the cell if its voltage is below 3 V.
For example, in the TPS61200 (from TI,) this feature can be implemented by a special resistance divider.
I don't see this feature in the MCP7381's datasheet, but I see UVLO and I wonder how to use it to set a 3V threshold.
MCP73831 datasheet


texts: Are there any manufacturers of color image sensors who publish their datasheets?

texts: I need a 1/2.7" image sensor with MIPI interface for a project. After some research I thought OV2710-1E might be a good choice, so I tried to find a datasheet, and found nothing. So I requested their sales if I can buy these sensors, sign the NDA and receive the datasheets. Their response was that first I need to buy at least 10000 sensors (which I obviously can't afford), so I am now wondering if any of image sensor manufacturers are more open about their products?


texts: One of ten 74HC595 shift registers have wrong output state when clocking in data

texts:
I have a project that uses 10x 74HC595 shift registers to control a series of electromagnets (80x magnets in total), switched with transistors. My current situation is that when I pull the reset-pin of the '595 LOW and HIGH again, and thereafter clock the latch-pin, the outputs of all the '595s change to LOW, as expected. However, as soon as I start clocking bits in, one of the '595's output pins is also miraculously HIGH, whereafter it also shifts a HIGH bit as it would normally. The only difference is, it should be shifting only zeroes until the HIGH bit reaches that shift register and gets shifted through that particular IC. For some reason and by some means, that particular '595 gets a HIGH bit in its register and shifts that out. I have checked the serial input pin just before shifting, and there is certainly no HIGH bit being shifted in from the previous '595. So I have no idea where that particular HIGH bit is coming from.

Attached is a snipped from the schematic of how the '595 is connected. The outputs are connected to NMOS transistor gates for controlling the electromagnets. Below is a snippet from the code that controls the '595s:

void main(void)
{
    int i;

    /* Reset the shift register contents and latch new contents */
    shiftReg_reset = LOW;
    delayus(1);
    shiftReg_reset = HIGH; //LOW-to-HIGH transition
    delayus(1);
    shiftReg_latch = HIGH; //Move new outputs (all zeroes) to latches
    delayus(1);
    shiftReg_latch = LOW; //HIGH-to-LOW transition
    delayus(1);

    shiftReg_out_en = LOW; /* Output enables '595s (active-LOW) */
    shiftReg_reset = HIGH; /* Pull reset pins HIGH (active-LOW) */

    for (i = 0[![enter image description here][1]][1]; i < 80; i++)
    {
        /* Set data pin */
        shiftReg_data = HIGH;
        delayus(1);

        /* shift bit */
        shiftReg_clock = HIGH;
        delayus(1);
        shiftReg_clock = LOW;

        /* load '595 contents to output latches */
        delayus(1);
        shiftReg_latch = HIGH;
        delayus(1);
        shiftReg_latch = LOW;
        delayms(250);
    } /* for */
} /* main() */`

I have no idea what is causing this behavior. As you can see from the code, the shift registers' outputs are all zeroes initially, but once the second bit is shifted, it seems like the same bit gets shifted from another '595 in the sequence, giving the idea that there are two sets of shift registers being interfaced to which output the same data, instead of doing it in a cascaded manner.

I have not yet connected any of the electromagnets to the circuit. For each transistor/electromagnet, I have also put in an LED to indicate the state of the shift register output. I am seeing the described phenomenon on the LEDs, so the phenomenon cannot be due to any effect caused by switching the electromagnets...


texts: Why input impedence is important factor for amplifiers

texts:
What I know about amplifiers is that its main objective is to amplify small ac signals and how much signal can be amplified is  known by calculating open circuit output voltage  (without load) or more accurately by calculating overall voltage across load  and higher the value of overall voltage gain higher will be amplification of ac signal .
But in all these things what I explained above has nothing to do with input impedence because Even if we increase input impedence  it causes decrease in voltage gain (for example CE with emitter resistance amplifier) and hence overall voltage will remain same .So that's why I don't understand how increasing input impedence is considered good ?although it adds nothing to amplification i.e overall output voltage remains same (compared to when input impedence is Less)  which is main purpose of amplifier .
I asked  almost similar question but I don't get much information from answer may be my question was not that well asked
How input resistance related to better amplification in transistor circuit


texts: Dynamic control of DC-DC converter current limit

texts:
I am interested in having dynamic control of the output current limit circuit of a DC-DC converter controller (the LTC3777 buck-boost controller in my case). This IC has a built-in current limit using an external high-side shunt resistor, which is monitored directly by the IC.

From looking at the datasheet, it appears that the two sides of the shunt resistor go directly to the inputs of a differential amplifier inside the chip, which is then tied into the rest of the feedback loop. What I would like to do is somehow modify that differential signal from the shunt resistor, so I can dynamically control the current limit setting using a microcontroller equipped with either with a DAC or digital POT.

My initial idea is to insert a differential amp (or current sense amp) in between the shunt and controller IC, and then adjust the gain of the amplifier to effectively control the current limit value. However, I'm concerned about this extra element introducing instabilities into the feedback loop due to the slight propagation delay said amplifier would introduce to the circuit.

Is the concern valid? Or are there other, more robust/simple approaches to do this (aside from controlling the current limit with a separate, independent circuit)?


texts: Converting DC Motor's Tachometer Output to DC Using Bridge Rectifier

texts:
I have a DC motor that its specification states that "Electric DC motor manufactured by Buehler. Sinusoidal Encoder Output: 11.5 VAC - 870 Hz @ 12 VDC input. No load speed: 6800 RPM. Runs in either direction"

The motor is connected in a NMOS MOSFET amplifier with 12V on the drain. The tachometer's two terminals are connected to a full-wave bridge rectifier which also has a smoothing circuit using a resistor and a capacitor.

My problem is the output of the bridge rectifier does not change when I change speed of the motor (I am measuring the output voltage of my smoothing circuit)

Does tachometer output value vary respect to its motor's speed ?

Is it possible to convert a motor's tachometer output to DC using a bridge rectifier?

Should my circuit work ?


texts: winding resistance measurement - thing from literature that i dont understand

texts:
There is a thing that i dont understand...
If i measure winding resistance of the transformer primary winding - will result depend if secondary is shorted or open?
If yes - why?
I also attach the sheet from a book.


texts: High/low order of the 4 select inputs of a 16-to-1 SN74150 MUX

texts: I'm looking at a Texas Instrument Data sheet for an SN74150 16-to-1 MUX but I can't find which of the select inputs (A, B, C, D) is the higher order and which is the lower order. Does anyone know which is which?


texts:
I am starting with a simple STM32 board that has only SWD (i.e., SWDIO, SWCLK, SWO, and NRST) and 3V power supply. (Yes, I have double-checked the connections of all of the above pins, both on the schematic, and with a continuity tester on the actual soldered board. But I don't think the configuration issue I'm running into has anything to do with these connections).
I compiled openocd with --enable-stlink and set up USB udev rules. When I run it, it makes the lights on my STLINK-V3 blink. Target current briefly drops from 13mA to 0mA, so maybe reset is working.
However, it appears that the SWD (or even reading target voltage) is not working.
I tried various transport select; here is my openocd.cfg:
# Should work with all STM32L4 Nucleo Dev Boards.
# http://www.st.com/en/evaluation-tools/stm32-mcu-nucleo.html

source [find interface/stlink.cfg]

#transport select hla_swd
# This causes JTAG access, not SWD access

transport select dapdirect_swd
# This SHOULD be the right setting, per the docs:
#     http://openocd.org/doc/html/Debug-Adapter-Configuration.html
# But causes "Error: Debug adapter doesn't support 'dapdirect_swd' transport"

source [find target/stm32l4x.cfg]

# use hardware reset
reset_config srst_only srst_nogate

How do I enable STLINK-V3 SWD?
Update I looked in the MCU manual again, and noticed that entering SWD mode actually involves a JTAG sequence on the SWD pins. So maybe hla_swd is actually trying to do the right thing. I might see if an EVB is offered that would rule out board issues.
The specific error I get with openocd -d3 and hla_swd in the config file is:
Debug: 252 12 stlink_usb.c:515 jtag_libusb_bulk_transfer_n(): ERROR, transfer 0 failed, error -9
Debug: 253 12 stlink_usb.c:515 jtag_libusb_bulk_transfer_n(): ERROR, transfer 1 failed, error -9
Debug: 254 1560 stlink_usb.c:515 jtag_libusb_bulk_transfer_n(): ERROR, transfer 0 failed, error -9
Debug: 255 1560 stlink_usb.c:515 jtag_libusb_bulk_transfer_n(): ERROR, transfer 1 failed, error -9
Error: 256 1560 stlink_usb.c:2882 stlink_usb_open(): read version failed

I see the reset pin toggling; I'm not sure about SWDIO/SWCLK (I should get a better scope). I don't understand why it's trying to do a bulk transfer without even reporting the target voltage first.


texts: Regulating 4s 18650 battery to 12V or use 5s instead?

texts:
I'm working on a power distribution board which is going to distribute to several other devices/boards.
Due to the high current requierment of the all the devices in total (about 29A - mix of 5V, 12V, 3.3V - mainly most current at 12V), I've decided to have 3 inputs to my board from the same battery. (my connectors were limited to 13A each)

Now, the 4s 18650s (not sure how many in parallel yet.) will have a nominal voltage of about 14.8V. Thus, I need to buck this down to 12V for each of my inputs.

Now the issue I have is that I can't seem to find many buck converters that will operate with an input of about 14.8 and give me 12V out, they're too close.

So I'm thinking, if I go with a 5s instead and then I'll have 18.5V nominal, I can easily buck that down with an IC such as the MAX20745. Would that seem like a reasonable solution?

MAX20745: https://www.maximintegrated.com/en/products/power/switching-regulators/MAX20745.html


texts: Although 8086 is a 16 bit processor, yet it deals with 8 bit memory. Why?

texts: Is it because of segmentation? If yes, then how? I don't see any problem using any 16-bit memory.


texts: Help Understanding How Long It Will Take To Heat My Wire

texts:
I am trying to find out how many Amperes I will need to reach a certain temperature in a certain time (Milliseconds)

I need a thick wire to slow the melting of the wire. "Nichrome is the wire I'll be using" now in the American Gauge. I want to use 12 as its thick but not too thick and on Wikipedia, when I was checking how many amps I will need to reach a specific temperature using that gauge type it said I will need around 39.03A to reach around 1400F but in what time period will I reach that? Thicker wires are much slower to heat up but smaller wires are very weak.

P S I am very new to the American Wire Gauge so forgive me if I'm wrong.

I need a thicker, more sturdy wire that can put in a high PSI environment and still reach temperatures of 2-4 millisecond. The problems i see is thicker wire don't have as much resistance and a smaller mutil-twisted smaller wire. Is there away i can change that and still reach my desired temp of 1400F?


texts:
I am working on a project which needs a Schmitt trigger. I designed it using IC UA741. I am using a single power supply of 9V. I am grounding the V-.

Here is my design.

The circuit works perfectly in this software as well as other software.

When I do the same in hardware it is not working. I was even getting 2V at V-  pin i.e 4 pin. Even though I had grounded it. And the output voltage is always 5.67 V at pin 6.

Can Anyone help me and highlight my fault?

Thank you

Edit...
This is my new circuit. Is there any visible erors here? I haven't tried it on hardware yet.

Thank you


texts: I found some information about general creepage and clearance distances here but it doesn't mention what is OK for inner layers, which are insulated and not subject to contamination the way outer layers are. Anyone know of a good reference for clearance rules for inner layers? I need to support 500V isolation.


texts: What kind of output does this sensor have?

texts:
I have encountered this sensor datasheet, and I couldn't figure out its output. Normally, a sensor should output voltage, current etc. and has calibration or sensitivity for us to translate it to what is being measured.
I couldn't figure out how this sensor is interfaced and measured.


texts:
My company have thousands of new Li Ion battery that is stored in ambient temperature for 3 years. Middle management then decided to manufacture products with these batteries.

I had already tested them, their current capacity drop to 85% rated. Then the management guys blurt out batteries can be recondition again and can be use as new batteries.

We have one of our product catches fire and the contract manufacture blame the batteries that we put in are too old. Which is why the management guys want to "recondition" them. Is there such thing as reconditioning batteries or is just a myth?


texts:
I need to design and build an embedded piece of electronics based on a PIC microcontroller.

I am assuming the process is:

choose chip (PIC16F690)
prototype code on PicKit breakout board
prototype on breadboard with associated electronics
create electronics design in software
send file to electronics company to make board and install electronics (or is there a step where I solder all this onto a PCB myself?)
test and order more

Does this sound about right?  What are the standard (free?) circuit design software packages for 3?


texts: How was the result of this SOP (sum of products) expression reached?

texts:
I have a boolean expression for which I have to get the truth table and standard SOP expression without using a Karnaugh map.

Here is what I got:

I do have the final answer of the SOP expression, but what are the steps that were done to reach it?

I tried solving it but I'm not sure of my answer:

Are the steps I took correct?

I'm really confused.


texts:
why does conductivity is calculated as:
conductivity = e.n.Un
e : electron charge
n : electron concentration
Un : electron mobility
but in intrinsic semiconductors
conductivity = e.n.(Un+Up)
Why does conductivity depend only on electrons in conductors but in semiconductors depends on holes and electrons?


texts: calculating the spectrum of digital modulation methods

texts:
I have just started studying the techniques of digital modulation. The book i am reading only has mentioned the psd of bpsk, bfsk , qpsk and msk. I would like to know, how the psd is actually calculated and I would also like to know, why the angles used in qpsk are (2m+1)pi/4
why cannot be one with a 89 degree and another with 91 degree instead of 90 degree and 90 degree. By these degree I indicate the angle between to signal vectors.


texts:
I am posting a small circuit I have found in a commercial power supply. It is a flyback converter transforming AC mains into 12V DC. I am having trouble understanding how transistor T1 is actually oscillating, that is switching between on and off state. I remember my brofessor saying that the auxiliary winding and R3 C1 form a positive feedback for the base of T1.

From my understanding R1 is a power up resistor to start the process of oscillation when the current is turned on. It drives a little bit of current throug the base of T1, therefore the pimary coil starts conducting and induces a current in the secondary auxiliary winding. Judging by polarity the current from the AUXiliary winding is now pushed through R3 and C1 into the base of T1 amplifying current flow. Once the inductor on the primary is fully loaded no current is induced in the auxiliary winding and therefore polarity switches and starts sucking out the current of the base of T1 through R3 C1? How does T1 ever start conducting again? I dont understand this, please give me some help, I need to pass my exam


texts: Does bidirectional impedance matching matter?

texts:
For my own learning, I derived the following relationships for basic two-element impedance-matching networks. Apologies that I cannot create diagrams; they are not supported by touch devices.

If \$R_S < R_L\$: put Ra in parallel with Rs; then Rb in series with Rl.

$$
R_A = \frac {R_S} {\sqrt {1-R_S/R_L}}
\\
R_B = R_L {\sqrt {1-R_S/R_L}}
$$

In the opposite case, if \$R_S > R_L\$, make Ra in series with Rs, and Rb in parallel with Rl, and in the equations exchange Rs with Rl and Ra with Rb.

In both cases, Rs will see an impedance of Rs looking forward, and Rl will see an impedance of Rl looking backwards.

But is the backwards criterion necessary if power is only ever transferred from source to load? Would this criterion only need to be enforced on a bidirectional line?


texts: High Precision Temperature reading, over a small range

texts: I'm looking to get a very high precision temperature measurement over a somewhat small range. Ideally, I want at least a 0.001 Celsius increment, over a -5C to 5C range. Searching Digikey doesn't seem to leave me with anything that could accomplish this. Is there a sensor that I could use to accomplish this?


texts:
I've got two questions:

What does a sync filter in a lock-in amplifier?
What are pros and cons of using it?


texts: How to convert a digital signal from 5V to 24V?

texts:
I have an industrial application where I have to interface a microcontroller output which gives a digital signal (0V to 5V) on its outputs and I want this signal to control a relay which takes (0V to 24V) on its input.

So I have to convert (0V/5V) digital signal into (0V/24V) to operate the relay. The microcontroller's pin output is 5 V 40mA for that I thinking I will use IC ULN2803 along with PC718 optocoupler to drive this 24 relay. My schematic as per my assumption is..

I am new to electronics design. Please check my design and let me know if it is correct or not. If not, then please suggest the best design that is suited to my application.


texts: Why are the input and the battery connected in a transistor amp?

texts:
I'm trying to make a simple boost pedal for my guitar using the simplest schematic I found. I'm wondering why the input is connected to the +9v battery in this schematic through a 430kohm resistance. There should be no such connection from what I understood in this video about transistors.

Here is the schematic for the boost pedal I'm trying to make.

What happens current-wise where the two different voltages meet at R1?

I found another schematic here that I understand better according to the video.


texts: Using multiple 4 input multiplexers to get an equivalent 16 input multiplexer

texts:
Here is my problem:

pretend each of the multiplexers are hooked up to the corresponding bit of each Byte. The first multiplexer is hooked up to the first bit of each of the Bytes (0 - 3). The second multiplexer is hooked up to the second bit of each Byte (0 - 3) and so on. My problem is, is that i don't have 16 input multiplexers. How can i take 4 input multiplexers and get an equivalent 16 input multiplexer?

edit (by Steven)
Given the comments and the three downvotes it seems that the diagram isn't clear for everybody. At the right you have an array of 16 bytes (ignore "program instructions"). John wants a way to multiplex all of the 16 LSBs to one output, all of the next LSBs to a second output, and so on, for all 8 bits. That's the 8 blocks on the left, 8 muxes. They only show 4 inputs and 2 select lines, because John's problem is that he can't find a 16-input mux. HTH.


texts: Altera has created EPCS and EPCQ devices, can only these be used to store FPGA configuration data?

texts:
FPGA configuration data must be stored in external non-volatile memory. Can we use just any flash memory or only specific types? What about EEPROMs or any other nonvolatile memory device?

Edit: I am referring to active configuration where the FPGA configures itself, by itself, without support of an external device like a microcontroller or microprocessor.


texts: The relationship between bit depth and SNR in ADC

texts:
An 8-bit audio signal has a theoretical maximum SNR of 48.16 dB (20log(2^8)).
My question then would be, does this work in reverse, i.e. would an analogue audio (or video) signal with an SNR of <=48 dB only be worth sampling at 8 bits? Or is this purely just a measure of SNR in the derived digital signal after quantisation?


texts:
I have a general question. I have a GSM module (adh8066 link to data sheet below) that I purchased from sparkfun. In the data sheet, it states that in tx mode, the module can draw up to 2 amps @ 12v.HOWEVER, the datasheet states that the module only needs 3.4V～4.5V (4.0V is recommended).

The BOB for this has a recommended voltage of 6-12v with 2 amps. I am curious about this because an iphone 4 battery is rated at 3.7 volts. Is there a major difference in these cell modules, or is a 3.7 volt battery able to provide a peak amperage for short periods of time or is the iPhones cell module a completely different technology? It's a little confusing since the data sheet stated 3.4-4.5 but the module can draw 2a from a 12v source.

The reason I am curious is because I wanted to power the adh8066 with a battery and receive 3-5 texts per day and have the battery last for 3 months (perhaps unreasonable). Is there a reasonable sized rechargeable battery that would power this GSM module?

EDIT- I have been reading a bit more. Would a 3.7 volt battery rated for 2500mah work to power the gsm at 1-2 second bursts of 2 amp?

ADH8066 BOB link

ADH8066 datasheet


texts: USB Interrupt and Isochronous transfer bandwidth concept

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I read in the USB spec and other USB materials on the web that interrupt transfer mechanisms (for devices like mice/keyboard) are guaranteed a 'bounded latency'.

Whereas the isochronous transfers (media device - camera/speakers) are guaranteed USB bandwidth and bounded latency as well.

If I have a high-speed device (480Mbps), then what does the 'bounded latency' and 'guaranteed bandwidth' mean?

I understand that for media devices, a guarantee of the USB speed should be there in order not to drop any audio/video frames/packets. But what does bounded latency offer over here that gauranteed bandwidth cannot?


texts: How to produce a highly accurate phase or frequency shift at 500 MHz?

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I currently have a couple of function generators that can be tied together in order to produce an arbitrary frequency or phase shift up to 20 MHz. Essentially I could say I want FN Generator 1 to be pi/8 ahead of FN generator 2. Or I want FN1 to be 19.99 MHz and FN2 to be 20 MHz.

Is there any easy way to do this at 500 MHz? I have been able to find function generators that can go up to that speed, but have yet to find one that can have an arbitrary shift from another signal.

So does anyone actually make function generators that do what I want? If not, is there a way that I could generator these type of signals myself? Ideal voltage out would be 0 to 5v and sin or square wave is acceptable.


texts: How to add lightning protection on a PCB?

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Currently, I have the PCB design ready, and I want to add lightning protection to the PCB. Can someone suggest a good, low cost solution for it? I am new to adding lightning protection.

One of the methods I have found is ESD diodes.

Currently the PCB is operating on 12v 1amp.  It's all digital signals only.


texts: Constant current or constant voltage supply? - Setting up LED strips with both series and parallel LEDs on the strips themselves

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Up to now, we had 2 COB LEDs ran in series (avoid thermal runaway of UF) driven by a CC power supply (elg-150-c1750b.)
We want to upgrade our setup because we found more efficient solutions in the forms of LED srips (SL-B8T1N60LAWW).
For this exact type I did not find schematics but looking at the parameters and similar strips I suspect the LEDs are used in a mixed arrangement on the strip itself.
The strip still does have a sensible "Uf" and typical current defined which I can use for constant current operation.
The min- max operating voltage is 11-13 volts, while other types are 20-25 volts, this kind of suggests these are for parallel operation (12V and 24V CV supplies,) but the datasheet does not clarify the mode of operation.
Is it safe to operate strips with mixed connections using a constant current supply?
We want to use 6 of the mentioned strips in series because normally it is better, but if we have parallel connections involved on the strips, CV drive sounds safer because if 1 LED fails the others parallel with the failed one will not overload.


texts: How do you perform circuit calculations for the darlington pair

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I need to know what formulas or set of calculations would be used to figure out the base resistor and load resistors when hooking up a darlington pair as my datasheet for the ds2003 does not provide a hfe.  The chip is 7 darlington pairs, and I am hooking it up to be controlled by my micro controller, to drive leds.  If I know the current I need for my led to be saturated, how would I know what base resistor value I would need to put on the inputs to keep the base current under 25mA

Essentially I want to know what formulas are used or what is the common practice for designing such a circuit (led driver)

Single transistor calculations seem to be well published and I always have a hfe to work with but this is missing from the datasheet for these darlington drivers.


texts: Lightning Surge Protector that complies with DO-160. Indirect lightning waveform, Gas Discharge tube or MOV in parallel with tvs

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Would it be wise to put Gas discharge tube in parallel with tvs diode?

OR

Would it be better to put MOV in parallel with tvs diode?

Also when deciding on tvs diode, how does indirect lightning surge waveform come to play?

I need to put a lightning surge protector in line with a power over ethernet cable. I am asking this question in order to build a lightning surge protection that complies with DO-160.


texts: Mylar Paste Stencils - Paste Mask File Conversion

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I want to cut some cheap mylar stencils from mylar for quickly assembling some fine pitch SMT designs. I have access to a laser cutter for this purpose. The laser cutter accepts various file types... unfortunately g-code or RS274x is not one of them. Does anybody have any options for converting output from Altium to a DXF?

Even better, with an option to offset the lines by half the kerf of the laser? Though I can always do this manually using a CAD program...

EDIT:

For extra credit :), a solution to go straight from RS274x to DXF (free) would be desirable as well. Sometimes I let the board house panelize and all I get back is the gerbers.


texts: Functional and Timing accuracy of an RTL Model

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I am sometimes really confused by the abusive use of jargon in EDA/VLSI design articles and books. With no precise definitions, its upto the reader to make interpretation which is very ambiguous and incorrect at times

Like,

What is the difference between Pin accuracy and Bit accuracy ?

Does pin-accuracy apply to communication interfaces and bit accuracy to computations. Can 't they be used interchangeably ?
Is it correct to say that an RTL model has

- Functional accuracy == Pin/Bit-accurate
- Timing accuracy == cycle-accurate ??

Which means that an RTL model when simulated produces precise results at each and every clock cycle. I have come across articles where author says Bit and cycle accurate models simulate faster than RTL models - which suggests that relatively RTL model simulations are slow because they are more precise in terms of functional and timing accuracy.

Can someone explain how(using VHDL or Verilog code) ?


texts: Does solder crack below some temperature?

texts: Does regular 60/40 solder have a practical lower bound on temperature that the solder joint can withstand?  That is, will solder joints become cracked below a certain temperature?