texts: Current sensing relay with delay on break for dust collection system

texts:
I am in the process of planning our a new workshop in a single car garage.  I have a large 20A Dust Collector that needs to be on its own circuit or else it will trip.  I also have a ceiling mounted air cleaner to get any fine particles that get airborne.

I want to setup a system where if I turn on any of my individually switched tools such as my Table Saw the air systems will turn on automatically and remain on for some time  after. I also have them switched so that they can turn on manually.

As a lowly Civil Engineer I'm a little bit out of my depth clearly, but I tried to do a schematic for this.  Can you gentleman tell me if I am on the right track?

I also made an album with some parts pulled from Amazon for the project.
https://imgur.com/gallery/hV7RzMW

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to simulate the circuit posted here, which looks like this:

I'm running a transient analysis and have the following settings:

I expected to get the output as a square wave, but I'm getting this instead:

Does anyone know why I might be getting a zigzag wave rather than a square wave?

Here is the definition of LM339 used:

EDIT:

If I use a time step of 0.055ms and the stop time to just 5ms, I get the following:

which is still not a square wave.

The amplitude of the input signal is 5V.


texts: Can a voltage divider be used for (input) jack detection?

texts:
I would like to detect when a jack is plugged into my connector. The circuit looks like this:

One end of the jack is connected to a speaker, and the other to an audio source, such as a phone or mp3 player.
Basically what is drawn is what I'm making. The main thing here is to connect the phone and the speaker, with the goal being to either use bluetooth or the jack connector in question based on whether the jack is connected or not.
So, a cable goes from phone to jack, jack is connected to speaker. Arduino needs to see whether jack is connected to phone or not.
Will this work for detecting if a jack is inserted, without damaging any components, particularly the audio source and speaker?
Note: I would use a jack connector with a detection pin. But with a 4 pole (TRRS) jack, I haven't been able to find any (or they don't exist...). PCs seem to use the codec for this purpose, and phones don't seem to have a detection pin either. I have a 7 pole jack connector for example, and it doesn't have a microphone terminal, it shorts ground and mic.


texts:
I'm back with my basic questions.

I'm trying to answer some questions, using Thevenin, for this circuit:

simulate this circuit – Schematic created using CircuitLab

I must answer:

\$R_{th}\$
\$V_{th}\$
Find short circuit current on A-B

For \$R_{th}\$ it is quite simple ( I hope...), and can be done calculating the total resistance of the following :

simulate this circuit

Which results in 0,75 ohm.

Now my problems comes. To calculate \$V_{th}\$, I started using superposition calculating the voltages for \$A_1\$ and \$E_1\$.

For A1 I calculate:

simulate this circuit

Considering that the current in A-B is the \$A_1\$ current source, the voltage is:
$$V_{ab}'=A_1\times R_{th}=2A\times 0.75\,\Omega = 1.5V$$

To calculate voltage using \$E_1\$ source. My problem is that the point \$A\$, from the \$E_1\$ point of view  i in between of a \$\Delta\$ resistors connection (\$R_1\$, \$R_2\$, \$R_3\$).

I tried to do \$\Delta\$ to \$Y\$ like:

simulate this circuit

Which is most probably wrong, 'cause it means that voltage on A-B is the same as \$E_1\$, that gives
$$V_{ab}=-E_1+V_{ab}'=-16V+1,5V= 14,5V$$

That is wrong, 'cause I know the result is \$-12.5V\$

I did something from or need I a different approach?


texts:
For the second picture below, how to derive the expression for Vo ?

I suppose there is some in-betwen maths that I missed out.

Note: 41.44 ohm is the parallel equivalent for (50 ohm + 8.56 ohm) || 141.8 ohm


texts:
I am trying to send data between an Arduino Uno and a Mac.

The Arduino Uno is running this simple sketch to print data to serial:

int redButtonState = 0;
int redButton = 4;

void setup() {
    Serial.begin(19200, SERIAL_8N1);
}

void loop() {
 redButtonState = digitalRead(redButton);
 String x = "Hello";
 if (redButtonState == LOW) {
  Serial.print(x);
  delay(1000);
   }
}

I have a USB to Serial Cable plugged into the Mac. The Serial Cable Tx and Rx are connected to the Tx and RX on the Arduino Uno.

I expect to see "Hello" in Cool Term, instead I get this:

I have also tried goSerial with Similar results, both were setup to 19200, 8 data bits, no parity and 1 stop bits.


texts:
First, thank you to anyone taking time out of their day to read this and answer. Resources like this are incredible for amateurs like myself.

My question is based around power supplies, Arduinos (clone board), and LEDS. My device will use an Arduino to interface with a strip of 160 5VDC RGB LED's. Each color for each LED pulls 20 mA for a total of 60 mA at full bright, full white based on the datasheets that I can find. Total power consumption 9.6 A (this seems very high). The datasheet also makes reference to 3 to 9 W per 32 LED's so 45 W max. I'm going to consider the power consumption relatively negligible for the Arduino (20mA at most I believe, very small sketch running it).

I would like to power all of this from one supply so my question is: What do I need? The one supplier has an accompanying 5v/6A supply they say can power 200 LED's which is feasible if they are not all on simultaneous (which they rarely will, but I'd rather be safe).

The next question is what isolation do I need between the Arduino and the LED strips. I obviously won't hook the strip to the Arduino 5V pin, but could I share with one line directly to the Arduino, one line to the LED strip from the supply and a shared ground?

Finally, based on the previous two questions, could this be powered with a rechargeable battery? And no, not a car battery. Something like a NiCad or Li-Ion battery pack.

Thank you in advance for any insight you can provide.

Thank you again.


texts: My Firebird electric guitar's bridge pickup is operating at a very low volume. What could be causing this and how can I fix it?

texts:
I have a Firebird electric guitar with two mini humbucker pickups.
Both pickups have been good since I got it, but suddenly the bridge pickup stopped working. The neck pickup is fully operational, but the bridge pickup is barely audible.
If I turn the amp up to 10 I get a very faint signal through the bridge pickup, but it is nowhere near a usable volume.
It does this on every amp too, so I can rule any amplifier issues out.
Does anybody know why this kay have happened, and how could I repair this?


texts: How do I build and simulate a T Flip-Flop without a reset in SystemVerilog?

texts:
The problem I'm facing is closely related to this: https://electronics.stackexchange.com/a/540545/238188 . I found I could not simulate a T Flip-Flop without a reset on Multisim Live.
I found that I could not get a T Flip-Flop without a reset to simulate in SystemVerilog either, but I could get a JK Flip-Flop without a reset to simulate. This is because I can set a JK Flip-Flop to a known state using J = 0, K = 1 or K = 1, J = 0.
The design code:
module t_ff(input logic t, clk, output logic q, q_bar);
  parameter HOLD = 1'b0,
            TOGGLE = 1'b1;

  always_ff @(posedge clk)
    case (t)
        HOLD: q <= q;
        TOGGLE: q <= ~q;
        default: q <= 1'bz;
    endcase

  assign q_bar = ~q;
endmodule

I tried using bit in the testbench, but that did not work either (just as I expected). I understand that a reset is important for a Flip-Flop in IC Design, but can't we build a Flip-Flop without a reset? I think the T Flip-Flop can be used without a reset in applications when the input for the flip-flop comes from another digital circuit.
I also came across this question and answer:
Is there a right way of implementing a T flip flop in verilog wrt using reset signal?
But that answer does not mention what should be done if we don't use a reset.
My question arises from this conversation I had with user "Elliot Alderson"

@ElliotAlderson if you design a T Flip-Flop where the only inputs are T and the clock, then there is no way to set the output to a known state in simulation that supports 'X'. Further reading: sutherland-hdl.com/papers/… – Shashank V M Jan 3 at 16:32

@ShashankVM I think you can, with an initial block in Verilog for example. Sutherland writes very useful papers...did you read the first sentence of the second paragraph in Section 7? – Elliot Alderson Jan 3 at 17:42 (Why can't I make flip-flops in logic simulators?)

"Elliot Alderson" says we can use an initial block to set the output to a known state. I followed that comment and read the section of that paper by Sutherland. I found it seems possible according to the paper, but how is it done?
Link to the paper: https://sutherland-hdl.com/papers/2013-DVCon_In-love-with-my-X_paper.pdf
How is this problem handled in Gate-level simulations?


texts:
This is a 2 different cold junction compensated thermocouple smplifier circuit.

I just don't understand why it needs 1.5MOhm (OP291 Figure 70.),  R4 6.04k (OPA335 FIGURE 3.) and how to calculate the resistor value.


texts: What is the best interface circuitry for using FSR sensors?

texts:
Force Sensitive Resistor (FSR) is a sensor which lowers its resistance when there is force upon it. If there is no force acting on it, the resistance is ~10MOhms.

Looking at Interlink's guide (here) and FlexiForce's A401 datasheet (here) here are interface circuits which are recommended:

1- Simple Voltage Divider
Pros: simplicity
Cons: ADC impedance introduces distortions in measurements

2- Voltage Follower via OpAmp (buffer)

Pros: Input resistance of OpAmp is near-infinite
Cons: There is offset error due to OpAmp

3- Adjustable Buffer

Pros: Gain and offset can be tweaked
Cons: Rather complex,IMO

4- Transimpedance Amplifier
Pros: Conductance/Force of FSR seems to be more linear that Resistance/Force
Cons: ???

Note that there is a limit on the current flowing through FSRs. The circuit should also take that into account.

1- Are there any other circuits for this application?
2- What is the best configuration for (A) Calibration and (B) Normal Use?

Here are my other questions related to FSRs:
What is meant by "adjustment of the output gain and offset" of a Force Sensitive Resistor interface circuitry?
What is the maximum force that a FSR sensor can detect?

FSR sensors have both creep and hysteresis. That is one issue. The other issue is a good interface circuit which both limits the current and produces zeros offset and noise.


texts:
I’m charging a Li-ion 3.7 V, 3500 mAh using a TP4056 charge controller IC and feeding a 6 V, 9 W monocrystalline solar panel to charge it.

When I connect the solar panel at good sun light at 2 PM in the noon, though what ever the programmable resistor I connect Rprog, 1k, 2k, 3k or 4.7k, the 4056 IC is heating very badly, at times my skin got peel off. What is the mistake we are doing?


texts: How can I parallel a battery supply and AC supply?

texts: How can I proceed if my battery does not supply all the charge I need and want to compensate by supplying the rest with an AC source connected in parallel with the battery?


texts: Tools used to manufacture entire digital systems

texts:
I am new to electronics and am trying to wrap my head around the various tools used for producing various digital components.

My understanding of HDL languages like VHDL and Verilog is that they describe the behavior of chips/ICs and are ultimately used to fabricate FPGAs and ASICs.

My understanding of tools like Eagle CAD is that they are used for designing circuits like PCBs, motherboards, etc. So, say I am using a breadboard to design a circuit. Once I am satisfied with the way the breadboard is wired, I would then use Eagle CAD to model a PCB using the same wiring as my breadboard prototype, and Eagle CAD produces a file. I then hand that file to a PCB manufacturer, and they produce a nice, sleek PCB for me.

My first concern is this: are my assertions above correct? Is my understanding of these tools spot on, and if not, can someone please rectify or clarify anything for me?

Assuming I'm more or less correct:

What tools are used to design entire systems? Say I have a device that has:

An custom ASIC chip/processor
Flash memory chips
EEPROM memory
Peripherals (LEDs, servos, etc.)
All of these connected via "motherboard"/PCB

I'd imagine HDL tools would be used to design the ASIC, and something like Eagle CAD would be used to produce the motherboard/PCB connecting everything, but what about the memory chips and peripherals? And are there any tools that design all of the above?

I ask because, ultimately, the entire system has to be integrated into a single PCB. That means a single manufacturer/assembler is ultimately responsible for putting all the parts together. So what I'm really getting at is: what types of files/specs are handed to a manufacturer to produce/assemble an entire system like the one above?


texts: Identifying the capacitor polarity from a Samsung 2333SW LCD Monitor

texts: There are no marks on the sides or the bottom, Only the top is marked by a half moon.(See Picture) How do I determine the negative side of the capacitor. wires on the bottom come from the half moon side and opposite of the half moon


texts: What is the relationship between field strength and efficiency in a DC motor?

texts:
This refers to a DC motor with permanent magnets.

What is the relationship between the efficiency of the motor and the magnet field strength?


texts:
In super small low power devices, where space is a big premium, complicated passive networks can take up a lot of space. Is it possible to get a passive or mostly passive ASIC fabricated? If it is possible, how much would it cost? Obviously it would never approach the tiny cost of discrete passives, but when you really need that space it might be worth it.

In terms of costing for ASIC manufacture, this question was really helpful, but it's talking about more traditional ASIC's where the main thing is the active components.

I'm also wondering, maybe ASIC is the wrong word? Is there another word for this kind of thing?


texts: 12v PWM Fan Seems to Be Running Inversely of What It Should Be

texts:
I have a 120mm 12v Fan that is used on an Antminer S7. There are two fans on the antminer, and they both are controlled by the software built in.

I had one fan break, so I replaced the fan with a similar model. It's the exact same size as the original, 4-pin connector and all that (the connector does not exactly fit the header on the board). But this replacement fan never runs at the same speed as the other fan.

For example, when booting, the antminer performs a self test, where it will ramp up the fans for about 30 seconds, and test that it is receiving an RPM signal. It may do this multiple times if it does not detect a signal.

What I have noticed during this boot cycle is that the two fans do not run at the same speed during the tests. The one fan I replaced starts at 100% speed as soon as it gets power. The other sits at idle speed (something like 15%). Then after approx. 30 seconds, the first fan ramps up, but the replaced fan does the exact opposite. Now, some of you may say that maybe the antminer is purposely ramping up only one fan at a time during the tests. Well, the reason I don't think this is correct is that I notice the same trend happening when the miner is running. On automatic fan speed mode, I will notice that as the first fan ramps up, the other one ramps down. And even when I manually set the fan speed to something like 15%, the replaced fan stays at a high RPM, while the other one does what you expect.

And like I stated before, the header does not exactly fit the connector. It's 4 pin, but there is a keyway on the header that is narrower than the one in the picture of the item above. But the connector on the item pictured is definitely the correct one. It still kinda fits the header, but you have to force it.

I somehow doubt that the connector size has anything to do with the RPM issues because the pinout doesn't seem to change from the traditional connector. But i'm open to ideas here.

Another little tidbit I would like to include is that the antminer does not reliably receive a tach signal. Occasionally it gets an RPM reading, other times it doesn't. THIS could be due to the connector, but re-seating it doesn't change much.

Sorry if this post is super rambly, I wanted to ensure I got as much info in there as possible.

Ideas are greatly appreciated!


texts: AVRDUDE throws "target doesn't answer." with USBASP and ATMEGA48PA

texts:
So far, I could reprogram a circuit with an ATMEGA48PA without problem. Until I got (after apparently was programed successfully):

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
         0x19 != 0x00
avrdude: verification error; content mismatch

Now every time I try to program it, I get:

avrdude: warning: cannot set sck period. please check for usbasp firmware update.
avrdude: error: programm enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

On that last unsuccessful program (the one with the verification error) I had pulled down the reset pin manually. Could that have made such harm?
According to my multimeter, the reset PIN is pulled up by default (so it is supposed that it is still configured as reset).


texts: How do you draw a DC equivalent circuit of a circuit which has an AC voltage source and a diode?

texts:
I am studying analog electronics now and I have encountered this problem for my assignment which I have some serious problems solving, wondering if anyone can provide some help. i have searched around the internet and my notes for days but could not really find any real help so thought I turned to this platform.

  Draw the DC equivalent circuit and determine the DC output voltage VR and current IR through the resistor RL by means of successive iteration method.

Some info for the problem:

Vdc = 10v
Vs = 0.1 x cos(5000t)
r1 = 10 ohm
rL = 100 ohm
Vd1 = 0.6v @ Id1 = 1.9mA
Vd2 = 0.8v @ Id2 = 210mA

Update:

For the updates, I found out that to get a DC equivalent circuit, AC voltage sources will be replaced by ground connections. so I tried it out and got the image below:

Is anyone able to help check if it is correct?

Update 2:

I shorted the AC voltage source and proceeded with the successive iteration method. the following picture is my method, and I did arrive at an answer but not sure whether it is correct or luck.


texts:
I've been experimenting on Half Bridge converter and there is something that I can not understand. what is the purpose of the capacitance and extra winding in gate base driver?

The extra winding is magnetically coupled with other winding of driver transformer.


texts: How does a chip interpret different opcodes?

texts:
I have learnt in school about opcodes and how it works with the ALU to add numbers and such, now is my question how the computer is able to understand this, because it is codes and the computer needs something to translate that to actually doing that, in't it? (correct me if I'm wrong plz)
I also want to, when I understand that, make my own processor so I can learn the computer bottom-up and become a good computer engineer.


texts: I took apart a weighing scale to get the load cell from it. The weight scale was capable of measuring up to 85 pounds with 5 grams precision. The voltage drop of the weight scale, however, is too small. It is about 0.4 to 1.5 millivolts. I need to read this somehow. I tried amplifying it with op-amps and did not work. I read about high resolution ADC like HX 711. What would the simplest way for reading and feeding the signal from the load cell to microcontroller without compromising the accuracy or precision?


texts: Localized Brownouts in micro-controller reasons

texts:
In "An Embedded Software Primer" book, I read that

  if a chip must change many of its outputs signals from high to low or
  low to high at the same time, that chip will need a lot of power to
  change these signals. They are going to need more power so we need the
  -decoupling capacitors- , otherwise a localized brownout can occur for a few microseconds.

..
I need a sample code in C or Assembly that shows how can a chip change its output signals at the same time !
..
book link: http://www.staroceans.org/kernel-and-driver/An%20Embedded%20Software%20Primer%20(Pearson-1999).pdf chapter 2 page 20


texts:
I want to calculate the maximum offset voltage of this circuit:

Here's what I did so far:

Ib is the bias current and Av is the op amp gain.
My question is, how can I do what is asked without knowing the values of Ib+ and Ib-? I also know that the voltage source Vos can be in the reverse order.


texts: Linear output voltage using a potentiometer

texts:
I would like to use a linear 10K potentiometer to have a variable voltage output between 0 and 5V using a 5V input. The idea is to have the output voltage increase in a linear way as I'm turning the knob.

If it's turned 0% I need 0V output.
If it's turned 100% open I need 5V output.
As I'm turning, I need to have a linear voltage output

If I hook up the left pin of the potentiometer to a 5V power supply and the middle pin to GND via an LED (to avoid a short when there is zero ohm between the 2 pins), I noticed that the output voltage is not linear.

I get high accuracy in the low range (0-2V) and it takes about a 70% turn to reach 2V, leaving only 30% to cover the remaining 5V.

So if I have 10 imaginary positions on my pot, the voltage doesn't jump with 0,5V on each position.

Can something like this be achieved with a 5V power supply ? And if not, what would be the simplest way to do it ?


texts: How do I modify a DC electric generator to get the same power at a lower speed?

texts:
This will be a theoretical question.

Suppose that I have a DC generator, and I'm getting 300VA power from it when it rotates at 2000rpm.

I want to make it run at a lower speed of about 700rpm, and I still want to get 300VA power from it.

What mechanical modifications should I do on it? I mostly prefer only modifying its rotor and doing no modifications on the stator side if possible.

Does increasing the number of turns in its rotor windings do any good? If yes, at what ratio should I increase the number of turns? Does increasing the number of turns by \$ \frac{2000}{700} \$ do the trick?

Assumed that the load is a fixed 100\$\Omega\$ resistor.
Permanent magnet used as for stator.


texts:
I have been working on migrating a through-hole circuit design that works to a surface mount version.

It is a preamp designed by an engineer named Ritter. Here is his schematic:

www.ciphersbyritter.com/RADELECT/PREJFET/JFETPRE.HTM

We have made a through-hole circuit board that works perfectly, but when we migrate the design to use SMT parts the DC output voltage becomes much higher. This is an issue as we are trying to impedance match the preamp so it will be accepted as a mic into smartphones. (FYI the preamp still sounds great)

We have throughly compared the thru hole and smd boards and cannot see any significant difference except size, the smd board is much smaller, and that we are using different components (smtd versions of the thru-hole parts).

The Electrical Engineer on our team says that perhaps it is radiation occurring from the traces being too close to each other. Could this be a factor? Is there any thing else I could be testing for to find the difference between my seemingly schematically identical boards?

UPDATE

We have built two through-hole versions to see if they consistently output with the same DC bias of around 1.2V. Two of the three boards have a 1.2V output bias. The third has an output bias of 3V.

We then removed the transistors from the board putting out 3V and setup a breadboard system so we could substitute in different transistors. We tried about 3 different sets of transistors, and none of them affected the boards DC bias. We didn't substitute resistors, but we tested all of their resistance to see if they were any different from the working board and they were not.

We are now collecting as much data as we can from board to board. We have made a diagram of the lines we are testing between. We are testing the voltage and resistance between most traces of the board and comparing the results from Board A (1.2V bias) and Board B (3.0V bias).

Here is a link to the spreadsheet where are collecting our data:
http://tinyurl.com/zyctqm7

Schematic:


texts: Calculating resistor end-of-life drift in the worst case analysis

texts:
How is it possible to calculate the tolerance of the end-of-life based on this datasheet?
https://www.vishay.com/docs/53046/pfrr.pdf
My specs are -30°C to 60°C and I want to estimate the drift/ tolerance of the 221 Ohm resistor from the Vishay PFRR series. I researched and found some links, however, I still do not know how to use the datasheet for my goals.
I found this link
https://www.vishay.com/docs/28809/driftcalculation.pdf
however, I still do not know how to use the datasheet to calculate it.
I also found this link
http://escies.org/ftp/ecss.nl/TMs/ECSS-Q-TM-30-12A(12October2010).pdf
but they categorize everything as far as I understood and refer to 1) Time law: the cubic root of time and 2)Temperature law: Arrhenius, Ea= 0,28 eV.
How can I use this one for three years tho based on the datasheet?
As far as I understood there are several methods to calculate the drift /tolerance and I do not know how to do none of them.
To be more clear, I want to see how to calculate the aging drift so I can make a table like Table 2 in https://les-electroniciens.com/sites/default/files/cours/wcca.pdf
Please let me know if you are aware of it.


texts: The AC signal generators in my university's laboratory are such that whenever I turn them on and connect them to a multimeter to read the input voltage, I notice that the input voltage changes as I change the AC signal frequency by turning the knob for the frequency. Is this supposed to happen? In our experiments, we are asked to do things like plot graphs showing how voltage across a capacitor/inductor changes with frequency, etc. But if you want to get the desired graph(linear/inverse proportional form) you'd have to assume that the input voltage is always constant, right? Or am I missing something? My professors won't say anything on this matter(they're not very responsible, I'm not really in a decent university) and some of my classmates claim that they fake the data, while other claim that they actually get the desired curves. I get weird results and I think the signal generators are to blame, but I'm not sure. So I need to know if this is normal for the input voltage to change with frequency(and if so, why?), and if so how does this not affect my experiment? And if it does, am I expected to use some sort of potential divider trick?


texts: Connecting transformer with single input and secondary two outputs

texts:
So I bought a transformer VC16/1/18 and it has two outputs.

I want to get the full output on a single output. Does this look correct?

The updated one

Corrected not

Final


texts: Basic shielding practice for simple passive audio project in an enclosure?

texts:
I'm a tinkerer but not an electrical engineer. I'm constructing a stereo->mono summing box for my stereo (to listen to Beatles LPs properly, natch). I'm using the design & schematic here for this. Essentially it's two pairs of panel mount RCA jacks (input and output) for stereo signal, running through a 4PDT switch with a couple resistors to prevent feedback. Here is a copy/paste of the schematic from that blog:

What I am a little fuzzy on is what the minimum and/or reasonable conventions would be for "shielding" of this component. Ie, against RF interference from outside the box or stupid wiring ideas inside the box.
The web page linked there suggests just using plain 22AWG hookup wire inside the box for the +ve signals and just linking all four of the RCA sleeves (-ve) together. I have a few questions:

I was planning on using an ABS plastic enclosure for this, but then realized that I might prefer a metal enclosure to help with shielding but honestly I don't really know how this works?

Is basic hookup wire reasonable here? Or is there like some kind of single-conductor shielded wire that should be used for audio signals? Or something else? I know that two-conductor shielded wiring is often used for audio internals and carries signal/ground with the shield connected to ground at one end. But the circuit I'm building is really all signal lines and no ground, so even if shielded-single-conductor exists (and it's certainly not common on e.g. amazon) I don't know what I'd connect the shield to-- unless figuring out how to wire it all out to the RCA sleeves.

What do I need to think about, if anything, about physical layout of the wiring inside the box? If I use some two-conductor wires I happen to have handy either leaving one conductor unused or using the conductors for two different things (ie not the +/- of the same signal) is that a problem?

Any other obvious gotchas or obvious best practices that I should be aware of?

I am sure that using the plastic box and the radio shack hookup wire would "work" just fine most of the time, but I'm trying (a) to learn what I should be paying attention to for this sort of project and (b) my stereo is nice enough that I'm trying to not actively degrade the signal through basic incompetence. :)
Thank you so much for any insight.


texts: 3.3V interface on arduino is only giving 0.23V

texts:
I just received an Arduino ATmega2560 (GEEKCREIT).
The 5V interface is giving exactly 5V as expected.

But on the 3.3V interface I could only measure 0.23V.
What could be wrong?


texts: I need to calculate the average power spectral density after passing packets through a butterworth filter using MATLAB

texts:
I am trying to generate 100 packets(row vectors each of size 8192) of random bits(1,-1),filter them using butterworth filter and then plot their average power spectral density. I have to do this using MATLAB.My o/p should be a filtered sinc with a very sharp peak with small sidelobes. I can't get the desired output. I want someone to review my code for modifications please.
I have attached the image of my output as well(which is wrong).

%generates a random square matrix of 8192x8192
n=rand(8192);
%initiates a row vector of 64 zeros
B=zeros(1,64);
%makes a butterworth(lowpass) filter
[num,den]=butter(20,.6);
%two for loops to generate 100 row vectors(packets) each of size 8192 that
%give 1 for any value greater than 0.5 and vice versa
for c=1:100
for k=1:8192
if n(c,k)>=0.5
n(c,k)=1;
else
n(c,k)=-1;
end
%filter the generated vectors and calculate average power spectral density
x=filter(num,den,n(c,:));
A=fftshift(fft(x,64));
psd=A.*conj(A);
B=B+psd;
end
end
plot(B./100)
xlabel 'Frequency', ylabel 'Average Power Spectral Density'


texts: How to calculate d-axis and q-axis inductance from line to line current?

texts: I'm wondering how to calculate the d-axis and q-axis inductances for a BLDC motor given the line to line inductance L. My hunch is to use the Park and Clark transforms that are used for current, but I wanted to double check.


texts:
How do I plot power in LTSPICE ?

I browsed a few tutorials. Acc to them, you click and ALT on the element you want to find power of.

But my problem is I do not have a schematic. I prefer to build circuits with netlists. How do I plot power now ?

Also there is this strange problem that .plot statement generates an empty plot pane and we have to manually add traces. How do overcome this problem ?

I am including a simple inverter netlist for reference.

***Inverter***

M1 pdrain pgate psource psource PMOS_1
M2 pdrain pgate 0 0 NMOS_1
C1 pdrain 0 100f

Vin pgate 0 PULSE 0 3.3 10ns 1ns 1ns 20ns 41ns
Vdd psource 0 DC 3.3

.model NMOS_1 NMOS (LEVEL=2 W=2.88u L=1.44u VT0=6E-01 KP=20E-06    GAMMA=5E-01 LAMBDA=5E-02)

.model PMOS_1 PMOS (LEVEL=2 W=5.76u L=1.44u VT0=-6E-01 KP=7E-06 GAMMA=5E-01 LAMBDA=1E-01)

.tran 0.1p 50n
.plot tran V(pdrain)

.end


texts: How to estimate motor current under load

texts:
How do you estimate the average current under a typical load of a brushed DC motor?

I'm trying to size the right motor, motor driver and battery to propel a small two-wheeled platform using this guide, and that's allowed me to calculate the minimum unloaded RPMs and minimum stall torque I need, but when I go to find motors that match these specs, they only list unloaded current and stall current, neither of which will be my typical use case. The platform will never be weightless but neither will it have so much that it'll be stalled.

Since my specs require a motor that's both fairly fast and high-torque, the only motors I'm finding that satisfy that are usually high-current, some with a stall current of 6A or more. Now I'm trying to pick an h-bridge motor-driver and battery, and there's a pretty big cost difference between those that can power 500mA motors vs 6A motors. Even batteries rated at 10Ah or more usually can't source that for more than a few seconds, and batteries that can will typically cost hundreds of dollars, which is over my budget.

Since I don't need the motor to source the stall current, I'm hoping to use a small driver and battery and halt the motors if I detect a current spike that lasts for more than a couple seconds, indicating a stall.

Is there a formula, or at least a "rule-of-thumb" for estimating typical motor current under load given the free-run and stall current? e.g. If unloaded motor current is X mA and stalled motor current is Y mA is it fair to approximate that the typical motor current under load will be (X + Y)/2 mA?


texts: To what extent are semiconductors used in high voltage and power grid electronics?

texts: I'm thinking of silicon controlled rectifiers and HV thyristors. Why have vacuum tubes been phased out or have they? I believe that in some countries, power grid electronics is entirely tube-based because of their superior electrical robustness and vastly lower sensitivity to electromagnetic interference(in form of EMP attacks or geomagnetic storms).


texts: I have a small (300 W) kettle that just plugs in and is on. It really needs a simmer setting so I could cook soup in there. Is there a simple way to do this? I thought of adding some kind of power reducing switch but don't know what that would be called or how it would work in electrical terms. It would need to be variable so I could find the right setting to simmer.


texts: Why are two-port networks able to use a dependent source but not an independent source?

texts:
A two-port network can be modeled as black box with two-port parameters provided the two-port network consists of no internal independent sources.

This restriction does not apply to a two-port network with dependent sources, why the difference as both are sources?


texts: simple way to send addressable RGB signal wirelessly

texts:
So my electronics knowledge is pretty limited, But I'm hoping there is a simple way to do what I want. Also I'm sorry if this question is answered somewhere else as I'm probably not using the right search terms or something.
I have an addressable RGB LED strip controlled by an Arduino. It has a 4-wire connector. Basically I want the strip to be wireless. Is there a simple RF transmitter and receiver I can buy where all I need to do is connect the TX to the Arduino and the RX to the strip (and a battery)? The distance would only need to be 3 to 6ft. Obviously I retain the ability for the LEDs to be individually addressable and RGB.
Would something like this work? I'm guessing I'd only need to connect the LEDs to 2 of the pins? since, of the 4 wires, 1 is ground and an other is the 12v input. And I'd need to provide a separate 3.3v for the transceivers. But I wouldn't really know which pins I'd need to connect.
Thanks!


texts: Understanding reference application of LM3404

texts:
I'm looking at LM3404 to drive a 10W LED (900mA, 9-12V) with PWM. The reference schematic they give is the following:

I'm trying to de-structure the diagram, and I'm struggling with the purpose of L1 and D1. D1 is a 2A shottky diode, and due to its position I believe that it might act as protection should SW get shorted out? Why shottky and not zener? Speed?

L1 is a 33uH inductor; coupled with CO1 seems like a low-pass LC filter? Would that make sense?


texts: Wires under diodes on a PCB: distancer, radiator, ground return loop, or something else?

texts:
I recently watched a video by bigclivedotcom and there's one unusal (at least for me) thing on the PCB he presented. That's a switched power supply for a flat TV panel:

Under three parallel power diodes, there are four wires, also parallel, both ends connected to ground blob on the underside. Author of the video suggests that these are distancers that are used to make sure the diodes are not touching the PCB, and/or that these also may be a form of heatsinks.
That doesn't sound right to me. Sure, a proper heatsink is not cheap, but these wires won't take much heat off the diode's body, area of "touch" is like, a point. Times four, but still a point. Worst way to transfer heat (am I right here?). It may be a distancer, to prevent the PCB from heating up, or to provide better airflow? Ok, that makes at least some sense, but then, elsewhere I've seen standing diodes that achieve that as well:

(random unrelated pic from quick google search http://www.lampizator.eu/lampizator/REFERENCES/Philips%20DAC-960/Philips%2520DAC-960%2520CD%2520DAC%2520with%2520TDA1541A%2520DAC.html)
I understand that "standing diodes" may be harder to mount via standard process in a fab, but then, placing wires beneath diodes means that the board also had to have a nonstandard process (am I right here?).
I think that since that's a switching power supply, then those wires may be "additional ground path loops that reduce overall noise generated by switched high current flowing through diodes". My initial thought was that the wires are much closer to the diodes than the ground plane, and induction varies with distance, so the net potential difference induced in the wires will be different than on the ground plane, it will be not balanced, and the wires may actually form a loop for flowing/returning current.
Then I noticed that those wires are actually perpendicular to how I imagined the flow. Any magnetic field around the diode's conductor, is, well, around, so the wires are in parallel to the magnetic lines. That reduces induction in the wires down to zero (or almost zero). So the possibility of a ground loop forming is not due to the difference of distance between wires/ground and diodes, but rather due to no induction at all in the wires. Does that make any sense?
Can you confirm bigclivedotcom's explanation, my ground-loop hypothesis, or explain what is the actual purpose of those wires under diodes?


texts: OP AMP fabrication technologies impacts on design

texts:
I am referring OP AMP selection guide for implementing it in medical application where it involves optical sensing using photo diode then I/V converter and ADC for data conversion.

My question is how OP AMP fabrication technology like BJT, FET, CMOS makes impact on design. I want to have more insight of fabrication aspects and its impacts (pros/cons) while implementing it in design.

Thank you.


texts: Changing the torque and excitation in an alternator

texts: What is the effect of changing the input torque of an alternator with excitation kept constant? and what is the effect of changing its excitation with a constant torque?


texts: Blocking cell phone interference on LM386 amp

texts:
I built a small amplifier using an LM386 on a protoboard. The problem I have however is that it makes those typical cell phone sounds if my mobile phone is close to it.

Since I want to 3d print an enclosure for it I was wondering what the most efficient way of getting rid of this interference is?

Installing it inside a box with aluminum foil on the inside? Should connect the foil to ground?

Will the holes that I need to make in the box for the buttons and leds not cause any leakage?

This is what I built:
http://www.instructables.com/id/Tales-From-the-Chip-LM386-Audio-Amplifier/


texts: Frequency selective preamplifier at 10-20 kHz

texts:
I'm looking for a way to amplify microvolt AC signals generated in an induction coil.  I want to use 5 V single supply rail-to-rail opamps to amplify the signal at least 100 times in the range of interest 10-20 kHz, while suppressing noise at other frequencies.

After some background reading I simulated to following design in SPICE.  The first opamp amplifies the signal 100-fold.  Then follows a 2nd-order passive high-pass filter and finally the second opamp which adds another 10x amplification.  The simulation suggests the design will work, but perhaps someone with more expertise can suggest improvements or alternatives.

Before making a PCB and building this circuit I'd like some comments from the community.   Is a similar results possible with only one opamp?  What are sources of electrical noise to consider?


texts: How to read this schematic involving potentiometer?

texts:
I'm trying to hook up my LCD on a breadboard and a schematic diagram involving a potentiometer is a bit confusing.

Full Data Sheet: http://www.lcd-module.de/fileadmin/eng/pdf/doma/dip203-4e.pdf

I guess the easiest way for me to see this is, if that potentiometer is replaced with an actual resistor (say 2K), how would this schematic look?


texts:
I just upgraded a MCU from STM32F407VG to STM32F429VI or 1MB to 2MB When I looked at the linker script I found they allocated 512K for the program. To me that means 16 bit access to memory; 1MB of 32 bit words / 2 = 512K. But, everything I see shows 1MB of 32 bit access for the F407VG! I've looked in the Reference manual and it does not say the access path size just that an instruction is 32 bit and runs in one cycle. If the memory is measured by BYTE and it has 1MB / 4 for 127KB? Are ARM memory locations accessed 4 bytes at a time? As in 0 then 4 then 8 for three 32 bit double words?

Please reference any documentation, I GoogleFu it to death.


texts:
Hi,
in my circuit I made ground plane and inside of it I need clear area without copper for anthena. So I have created polygon in tRestrict layer and used Ratsnest for reconection. It worked, but not correctly. Copper was gone, but it took more copper than it should. It took 0.2mm more copper around each side of the polygone. I need ground plane align precisely around the polygon.

I think the isolation around polygon was created because ground plane polygon has column for isolation set to 0.2mm. How can I change isolation just for restrict polygon and keep it for other objects? If I think wrong and the problem is somewhere else, how can I fixe it?


texts:
I'm trying to use the timer (TIM4) to log rising and falling edge times from an external sensor.
I need to set the timer so that it ticks every 1µs and has a period of 40ms (so counts 40, 000 ticks before overflowing).
TIM4 has a source clock speed of 84MHz.
The datasheet says:

  "16-bit programmable prescaler used to divide the counter clock
  frequency by any factor between 1 and 65536".

However in most tutorials divide by 84 - 1 to obtain 1MHz. Can someone provide the exact formulas to calculate the parameters? Thanks in advance


texts: Load impedance simulation of buck converter

texts:
I would like to design a buck converter that will feed a printed circuit board that contains an inductive load like a DC motor and a relay, and some capacitive circuits like RLC filter. I have started from designing the SMPS with a resistive load and the simulation using Simplis showed to me the buck is really robust. Than I have connected in parallel a DC motor model (an inductor with a series resistor), I performed many simulation by changing the value of the inductor and I have verified that my buck is stable till 100mH with a series resistance of 1ohm and a parallel resistive load of 1ohm. I have done the same thing for a capacitive load, by connecting a capacitor in series with ESR of 20m, so the converter is stable till C=550uf, than it starts to oscillate.

My objective now, is to study the effect of the load impedance (Inductive, capacitive, another DC-DC converter) on my DC-DC converter stability (The loop gain), I have tried to built an equivalent circuit to simulate the output impedance of the power supply with different load, but I have failed and my circuits do not generate a correct bode plot.

I undergo the book intitled "Switch mode power supplies -SPICE Simulation and practical design-",by CBASSO where the other explained deeply the effect of the input filter on input impedance of a buck converter, but I could not understand how the simulation is performed

Can anyone explain to me how to set a circuit that is feed by a voltage source from the input of a load and inject a current source at the output to get the impedance of a circuit ? (Using Simetrix/Simplis), because I think there are some tricks on how to set the circuit, inject a current source from one side and voltage source from another!


texts: Latching push button with electronic reset

texts:
I'm looking for a latching push button switch that can be reset electronically.

After much searching I managed to find this post: Resettable mechanical switch?

which links to this switch:
http://www.digikey.com/product-detail/en/A8GS-S1305/SW1533-ND/4248837

which is really close, but I'd really prefer a push button instead of a toggle switch. Bonus points if the push button has different physical states (like the on state is pushed in further or lit up or both) and the physical state gets reset when the switch is electronically reset (button pops out, light goes off).

Has anyone ever run across this particular type of button? I know I can put together a circuit to achieve what I want pretty easily using a momentary button but it would save me some headache if there was a nice contained package that does what I want. The one I linked is so close!


texts:
I have to insert some wires into several electrical connections and have been getting conflicting information on whether or not they should be tinned before inserting.  I'm sure this is a quite simple question to answer with a picture so I have included one below.

To be clear, the screw itself does not make the connection here, but pulls the flat conducting plate on the bottom of the connection toward the flat conducting plate on the top.

Regardless, the connection is still supposed to be a friction fit held together by the force that you apply from tightening the screw.

I suppose the root of what I'm unsure about is whether making an electrical connection under mechanical pressure would suggest you should not tin the wires or if it is specifically the rotation and grinding on a tinned wire that would be caused by the screw that makes tinning these wires a bad idea.

I'm obviously no expert on this topic so any additional explanation on the thought process behind the answer is very welcomed.


texts: I am searching for any type of guides for pcb design for SDR (software defined radio) application without luck. I am planning to design pcb board with Zynq-7000 and AD9364 onboard. Any recommendation and useful links? Thanks.


texts:
I have a LT8330 Boost converter issue. As the output load decrease, this boost converter will use a burst mode, switching between sleep and activity, and thus decreasing the switching frequency.

The output load at which the LT8330 reaches the fixed 2MHz frequency varies based on input voltage, output voltage, and inductor choice. However, I can't figure out the relation between those parameters and how to predict the switching frequency based on those parameters.

Any idea? Thanks!


texts: Supply power to mini-ITX from car battery

texts:
Two related questions have been combined here as the answers and concepts overlap:

(Q1)  We are building a robot that will be controlled by mini-ITX PC. The power source for robot will be detached car battery. Question is how to power mini-ITX mother board (and HDD) using this battery? What devices are needed?

Edit: I think I need DC-DC converter that converts from battery voltage and converts it to 12V and stabilizes it. Right?

(Q2) Originally from here

I have a linux box powered by a "deep cycle" battery, and I"m wondering, would it be more efficient / possible for me to convert (or replace) the AC power supply in the unit with a DC one so that I don't lose energy in the conversion from AC power to DC, optimizing the use of power from my battery.

DIY link: http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/


texts: Discharge of a coil powered by parallel transformers

texts:
I have the following circuit:

I basically have 2 transformer, one is 230V-8V the other one has a ratio of 1:1, so 230V on the secondary.

I'm rectifying the two signals with two full bridge rectifier, and I'm controlling the two signals through the two switches, which are solid state relays.

In principle I need to feed the coil (which is a big mechanical switch) with the 230V half sine waves signal in order to close the contact of the switch. The pulse of 230V has to be very short, in fact once the switch is closed, I feed the coil with the 8V half sine waves in order to mantain the contact of the big switch closed.

My idea is to activate the SSRs simultaneusly, in order to have the shortest time possible between the commutation 230V --> 8V once I turn off the SSR SW2.
The two transformers share the same AC source at the primary.
The diode and varistor in parallel with the coil are used to dump the energy of the coil when a high spike of voltage occures.

My question is:

Due to the very large inductance of the coil, once I want to turn off the system, or simply switch from 230V to 8V, I'm afraid that the big voltage spike could damage the SSRs and the transformers. How can I improve the circuit in order to prevent breaking down of the SSRs or of the transformers due to induced high voltage, and how can I be sure that my varistor network will dump all the energy stored without any leakage?

Thank you.

Edit:

I forgot to mention that I couldn't find the varistor symbol, so I used the resistor's one. The varistor I'm using is the SIOV-B32K275  from Siemens


texts: Drawn current of heating elements in parallel won't add up

texts: I have three heating elements (12, 40W) that I want to connect to a single power source (12V, 16A). If I attach one of the heating elements directly, it draws 2,3A @ 12V. But If I attach 3 heating elements in parallel, they draw only 4,3A @ 12V. Can you tell my why its not 2,3A x 3 = 6,9A and how I could achieve that? I am using these heaters. Thanks for your help, appreciate any hint.


texts: What is a valley current in a regulator?

texts: Can someone explain what is a valley current in a regulator?


texts: How to select rated voltage of a RF capacitor

texts: For example, GSM low band PA output around 33dBm, I need to put a dc block (33pF) on my design. The cap vendor has rated voltage 6.3V, 25V, 50V. How to choose it? Is 6.3V ok for the design?


texts: What's the max discharge (in "C") of a Pb-acid and LiFePO4 (lithium iron phosphate)?

texts:
I know that lead acid batteries can handle massive loads, and they are even used to power houses with solar panels, but what is the maximum safe discharge for one of these?

I've done some Googling but I can't seem to find a number.  And, of course, it's not going to be the same from battery to battery but I'm sure they're all in the same ballpark.

Lately I've been seeing more and more LiFePo4 batteries come into the market as competitors for Pb-acid batteries.  I personally don't own any because they are about 4x as expensive, but what sort of discharge rates can these handle?


texts:
What is the role of a Network Interface Device in a ADSL connection?

Why the filter is not enough? What is the difference between them?


texts: Multimeter, measuring current calculates less. Can I calculate meter's internal resistance this way?

texts:
I have set up the following circuit in order to measure current.

simulate this circuit – Schematic created using CircuitLab

Of course, Ohm's law tells me that I should get a measurement of about 0.3A (300mA).

3V / 10 Ohm = 0.3

However, my meter shows me a value that is much smaller?  Actually, it's about half that at 157.7mA

Other Things I've Considered

Since I've tested my battery voltage and it is 3 to 3.01 volts I'm assuming it is fine.  I also tested the 10Ohm in resistor with the meter and the meter measures it at 9.8 to 10 Ohms which seems correct.

Meter's Internal Resistance

After a couple of searches I believe this is due to the meter's internal resistance.
If that is true then I'm calculating the internal resistance at about 10 Ohms also since:

3V / 0.157(mA) = 19.10 (Ohms)

Raises A Few Questions

But I still have a few questions.

From now on when I measure current with this meter should I just consider that I have about 10 Ohms of extra resistance? Will this value be consistent?  Is that a valid assumption?
If this is a known value why didn't the meter maker/designer just subtract that value from the calculation they do every time so the meter would display the correct value?
Am I missing some other piece of vital information (i.e. this is not the meter's internal resistance)?
Is it possible to buy a meter which would measure the current accurately* -- closer to 300mA?  Would it be cost prohibitive for a hobbyist?
If you can buy a meter like that, what might the description show that would help me to know it could measure current without being affected by internal resistance?

*I know this is somewhat ridiculous because once you know, you know.  However, I'm attempting to teach Ohm's law to early electronics students and attempting to show them that the meter will confirm their calculations.

EDIT
Because there were some questions about my initial voltage measurement I did some more investigation.

My original voltage measure was on the two AA batteries with no load.
I then measured approx 2.2 volts across the 10 Ohm resistor in my circuit.
I'm assuming that would mean something like:

2.2 / 10 Ohm = 220mA

However, I know when I measure that I only see 157mA of current.
So...

220mA - 157mA = 63mA (which are missing somewhere).

I plug in the missing 63 in the following way:

.8V (voltage drop) / .063 = 12.69 Ohms

So I'm still seeing a extra ~12 Ohms that I can't account for. That is obviously higher than my 9-10 Ohm extra I was calculating but could be due to rounding.

Does this add some additional valuable information?  I think so.

EDIT 2

Here's a zoomed in snapshot of the meter panel because a helpful post(er) thought the meter was in AC mode.  As you can see, the meter was in DC mode during the measurement.


texts: Why aren't quartz crystals' pin pitch aligned to the inch grid?

texts:
This is most probably stupid question, but I would love hearing the story. Can not find anything relevant in the net.

The spacing between the pins of HC-49 is 4.88 mm, there're some other variations like 12.3 mm and 3.75 mm, all of them are not exact multiple of 0.1" (or even 0.01").

More to consider - the pitch is even not aligned to the metric grid...

I found it out after drawing the crystal gasket and putting it onto the crystal device on the board, being astonished to see that my assumption about 0.2" pitch being wrong.


texts: Can a PWM fan be turned on and off with the control pin voltage?

texts: Can a PWM fan be turned on and off through the control pin?  Or can it only adjust speed?  Is it just a fet that turns the 12V on and off?


texts: Receive same GPIO input signal on multiple raspberry's from one source

texts:
I'm having 7 raspberry Pi's 3 connected to 7 screens, running an python 2.7 app to download different images from google drive, every raspberry has different images. Geeqie is displaying those images in an slideshow. The idea is to have one hardware scrolling mechanism (like an rotary encoder), providing the same input at the same time to all 7 Raspberry Pi's their GPIO input pin (or pin's in case of the rotary encoder). The python script handles the input. This is required so all images switch at the same time in geeqie.

Any idea's how to provide the same input signal at the same time in all 7 Raspberry Pi's 3 their GPIO input pin('s)?

It's not really clear to me how this circuit would look like. With keep in mind the max input current.

My idea's so far:


texts: 1GB single DDR3 Chip for ZYNQ(XC7Z020-2CLG400I), is it possible?

texts:
I'm putting together a PCB and I want to use single 8Gb (512*16) DDR3 chip (MT41K512M16HA) but the DDR3 address bank is less than the DDR3  chip.

Is it possible to use single 8Gb chip for this IC?


texts: PLL vs Higher frequency crystal oscillator for fpga

texts: I need 100MHz clock frequency to implement my HDL design on an FPGA. Is it better to use an FPGA board with 100MHz crystal oscillator or use PLL to increase the frequency? What are the advantages and disadvantages of them?


texts: Incorrect amperage readings, possible faulty meter?

texts:
I have a very simple circuit: a 9V battery is connected to a 1500ohm resistor, which is connected in series to the multimeter and back to the battery.

simulate this circuit – Schematic created using CircuitLab
According to Ohm's Law, I should get:
I = V/R = 9.15V (measured) / 1496ohm (measured) = ~0.00612A = 6,12mA
I set my multimeter to 200mA reading and I get 30.2mA.
Then I set my multimeter to 20mA reading and I get 7.89mA.
Why do I get two different amperages when I set a different limit?
Why are the readings so off compared to the theoretical amperage?
I just don't get it.
I don't have another multimeter right now so I can't verify whether my unit is faulty or I'm doing something wrong.
The same issue occurs when I add a led diode to the circuit (which draws approximately 2V, so I consider a difference of voltage of 7V instead of 9V): the readings are off.
I just started with electronics, so maybe this is a stupid question, but I can't wrap my head around it.
Thanks.
Edit: I attach two images showing the readings. I switched batteries several times, both the one powering the multimeter and the one used for the circuit.


texts: How to identify branches of root locus from figure/plot?

texts:
How can we identify the branches in a root locus

For example How many branches do we have in this below root locus(i feel from its appearance to have one branch)

And how many branches in this below root locus(i feel from its appearance to have two branches)


texts:
I'm trying to study an electronic schema based on a LM3914 but I can not find the same threshold voltage, can you help me?

Source of the schematic

Components :
--------------
IC1=LM3914
D1=1N4007 or equivalent
LD1-LD10=LED
R1=22K, 1/4W
R2=3K9, 1/4W
R3=1K, 1/4W
R4=680 ohm, 1/4W
R5=18K , 1/4W
R6=1K8, 1/4W
C1, C2=10uF/63V

Here is my approach

DETERMINING SIG_IN (Pin5) VOLTAGE
R1 et R2 is a voltage divider so VSIG_IN depend of VBAT (Car Battery)
I substract the 1N4007 forward voltage (1V) I found from the 1N4007 datasheet before applying voltage divider coefficient :
VSIG_IN = (VBAT - 1) * (R2 / (R1 + R2))
VSIG_IN = (VBAT - 1) * (3900 / (22000 + 3900))
VSIG_IN = (VBAT - 1) * 0.150

DETERMINING RHI (Pin6) VOLTAGE
Voltage on RHI is the voltage across R3 plus the voltage across R4 :
VRHI = VR3 + VR4
Internal reference voltage VREF (1.25V) supply constant 1.25V across REF_OUT (Pin7) and REF_ADJ (Pin8) :
VR3 = 1.25 V
We can calculate the current into R3 :
IR3 = VR3/R3
I neglect the current going into REF_ADJ (Pin8) so voltage across R4 is :
VR4 = R4 * IR3
VR4 = 1.25 * (R4 / R3)
So we can calculate VRHI :
VRHI = 1.25 * (1 + (R4 / R3))
VRHI = 1.25 * (1 + (680 / 1000))
VRHI = 2.1 V

DETERMINING RLO (Pin4) VOLTAGE
The internal 10x1K network and R5+R6 is a voltage divider, VRLO depend on VRHI :
VRLO = VRHI * ((R5 + R6) / (10000 + R5 + R6))
VRLO = 2.1 * ((18000 + 1800) / (10000 + 18000 + 1800))
VRLO = 1.39 V

DERTMINING VOLTAGE ACCROSS INTERNAL COMPARATORS
The internal 10x1K network is a voltage divider, the voltage across is :
VRNET = VRHI - VRLO
The voltage across each resistor is :
VR = VRNET / 10
VR = (VRHI - VRLO) / 10
VR = (2.1 - 1.39) / 10
VR = 0.071 V
The voltage across positive input of first comparator (Pin1) is :
VC1 = VRLO + VR
VC1 = 1.39 + 0.071
VC1 = 1.46 V
The voltage across positive input of second comparator (Pin18) is :
VC2 = VC1 + VR
VC2 = 1.46 + 0.071
VC2 = 1.53 V
The voltage across positive input of third comparator (Pin17) is :
VC3 = VC2 + VR
VC3 = 1.53 + 0.071
VC3 = 1.60 V
And so on...

DETERMINING CORRESPONDING BATTERY VOLTAGE
Now we can retrieve the battery voltage corresponding  comparators threshold :
VBAT = (VSIG_IN / 0.150) + 1
Where VSIG_IN correspond to threshold VCx
VBATx = (VCx / 0.150) + 1
Like
VBAT1 = (VC1 / 0.150) + 1
VBAT2 = (VC2 / 0.150) + 1
VBAT3 = (VC3 / 0.150) + 1
A so on...
If the voltage on VSIG_IN is upper than threshold (VCx) the corresponding LED is glowing.

PIN   VCx    VBAT
------------------
 10   2.10   15.00
 11   2.02   14.47
 12   1.95   14.00
 13   1.88   13.53
 14   1.82   13.13
 15   1.74   12.60
 16   1.67   12.13
 17   1.60   11.66
 18   1.53   11.20
  1   1.46   10.73
------------------
PIN  : Is the associated internal comparator
VCx  : Is the corresponding threshold on positive input of comparator
VBAT : Is the corresponding VSIG_IN battery voltage at the threshold

As you see i found about 0.5 V upper than on the schematic and i dont understand why, can you help me ?


texts: using potentiometer for tuning high voltage at very low current

texts:
Background Story:

my application involves in sensing low light, as low as intensity as 1mW/m2 so i have picked an APD than a normal PIN

usually after reading some APD science i have came to know if you want to increase the gain and operate at maximum, one has to change the bias to very high voltage as specified by factory specified spec for that APD, that too when operating at higher voltage one has to very careful with temperature and the bias voltage should be changed according to the temperature to maintain the gain

to be brief observe the effect

importantly an APD of same design(discrete APDs) may have different breakdown voltages, if you see the datasheet of APD i have shared the very first table shows you that the breakdown voltage of APD may varry from 315 to 490, which clearly means every APD will have different breakdown voltage and different operating voltage for same gain, one observation is the

  dV = Vbreakdown - Voperating

this dV is same for same design of APDs

Problem:

now my application needs 10 APDs to be used, i was initially thinking i can happily gang them to a single power source as in case of PINs

simulate this circuit – Schematic created using CircuitLab

but after knowing some APD science, its clear that it would be a flaw in design to gang APDs, so should i have to use 10 power supplies for 10 APDs ? :/
, makes design bulky, noisy and costly

An Idea :

i want the circuit to be something like this

simulate this circuit

the voltage at P1 would be temperature compensated maximum voltage(i feel all APDs would have same temperature coefficient - correct me), the digitally configurable block should be able to take 450V maximum and based on requirement should be able to provide a voltage between 350-450V, this kind of approach would really help in achieving my task of using a single power supply and biasing them,

here i am clueless about what can be this configurable block, i didn't see any buck converters or regulators with such a high drop voltage and really skeptical about this concept, this is just a idea

EDIT:

i have changed my mind, its even OK for primary design to go for non programmable version of P1

  a new thought came in my mind is why don't i use a simple
  potentiometer ?

the maximum current the dc-dc voltage source can give is 1mA so even though the voltage applied is 450V, if i need 400V at output i would put a potentiometer in place of P1

but will this bring a performance degradation ? because i am trying to process 100ns pulses falling on APD diode repeating at a rate of 20us, so a 50K resistor after power supply is going to add up capacitance ?


texts: Propagation 'speed' of EM waves in air versus through conductive material

texts:
This paper I was reading said: "At a high level, the propagation speed of EM waves through conductive materials is SLOWER than their speed in air".

Don't conductive materials intrinsically have less impedance than air as propagation mediums, to be conductive in the first place. Wouldn't the ray flow through this conductor faster with less 'resistance'?
Do EM waves only travel at the speed of light in a vacuum?

Or am I Stupid??


texts: Transistor Inverter - when does excessive small wattage become a problem?

texts:
I'm trying to choose the best values of resistors given the stock I have so that I can deliver sufficient power and current to an HM-TRP radio module.

In this circuit, I used the 100K resistor instead of the 8051 microcontroller because I'm trying to simulate the microcontroller impedance when the port is not set low in software. If I set the port low in software, then the left-most transistor emitter is grounded.

The main problem I have here is that when I used a simulator to measure current, Its registering between 197mA and 203mA, yet I want to provide the HM-TRP radio module enough current so it can function.

The problem with those current values to me is when I calculate wattage, it (according to the datasheet I found) exceeds the maximum value by approximately 25mW.

I can understand that if I exceed the wattage by a large amount, I might get a melted transistor, but what about by a small amount? Does it matter?
And what if the wattage is exceeded for under 100ms at a time?

For my circuit, the 15 ohm resistor is 1W, and the other resistor is 1/4 watt. Both are carbon film 5% tolerance. The transistors are both PN2222 and the 3.3V supply is fed from 5V (that directly feeds the 100K) through an LM1117-3.3 regulator.


texts: Converting a string of LEDs that were powered by 3 AA batteries to a switching power supply

texts: In addition to the switching power supply, I connected a buck boost converter.  The batteries provided 4.5 V to the LEDs.  However, the switching power supply would deliver 5 V with 3A. I adjusted the buck boost converter to deliver 4.5 V. I reused the original resister but when I turn on the lights, the resister quite quickly heats up to a point that I need to shut it off. I would believe the resister needs to be replaced with one that can resist the increased current.  What resister do I need to use so that it won't overheat and of course protect the LEDs.


texts: Measuring pwm output from low side FET with oscilloscope

texts:
I have a n channel MOSFET controlling a high current LED panel. The FET is driven by a FET driver, which is itself driven by a MCU pin. I am using PWM to control the LED brightness.

I want to double check the PWM with my scope, to ensure the duty cycle is correct. I can check all along the circuit, and I get proper readings from my scope. If I check the outputs from my FET, I get a garbage reading.

This is because, I believe, when the FET is off, the ground clip is disconnected from the ground reference, and it is left floating.

How can I check the FET output with my scope, since whenever the pulse is low, the ground reference is no longer connected?

EDIT: PWM should be 0-12vdc square wave, 5khz, 10% duty cycle. Also, when I use with the LED, it dims properly as would be expected with PWM, so I'm almost positive it is outputting correctly.

Scope probe is at 12v, grd clip is at OUT_LED_GND

Scope output

Scope connections, output LED


texts: Ground loop when measuring in process pH

texts:
I have been experiencing a very difficult to solve ground loop problem with my pH measuring system.  My basic setup is a standard pH electrode running through an op-amp to an ADC which communicates through I2C to a Raspberry Pi.

Calibration of the probe proceeds as expected and testing various liquids in glasses works perfectly.  The purpose of the pH meter is to measure the pH of a fish tank.  When placed in the process fluid I get very strange reading (sometimes ph of < 1 or > 14).  The calibration of the probe also quickly becomes altered.  If I have the probe suspended in the process fluid and scoop the probe out with a cup the reading returns to the expected value as soon as the cup breaks the water.

I assume this is a ground loop issue.  I have shut off and removed all heaters and pumps however this does not fix the issue.  I have noted that plugging and unplugging a monitor into the HDMI port of the Raspberry Pi changes my reading significantly, although it is still wrong either way.  The Pi is being powered from a standard cell phone charger.

Do I need to attempt to fully isolate my signal or are there other potential suspects causing the ground loop?

I am using a Ti LMC6001 Op-amp.  My circuit is taken from the datasheet   http://www.ti.com/lit/ds/symlink/lmc6001.pdf  The only changes are some resistor value changes to change the scaling of the voltage.

Update: Instead of using the raspberry pi I hooked the ADC (communicating over i2c) up to an arduino I had laying around.  The problem I described has disappeared.  Any ideas on why?

Update2:  The problem seems to be at least partially solved.  I mocked up a quick power supply with an old wall wart and a 5v linear regulator.  Using that to power the raspberry pi directly to the 5v bus gives me very stable readings for in and out of process fluid.  Use of the HDMI port reintroduces the problem but it is not needed.


texts:
I am trying to make nixie clock and I use MC34063 for buck/boost converters. The nixie tubes require 180 V to operate and the microcontroller and LEDs need 5 V. I use external 20 V power supply as a source. Here are the circuits:

5V

180V

When the circuit is powered I can hear an annoying audible noise. The sound comes from all small SMD capacitors. It sounds something like 13 kHz sine wave. I power the raspberry pi from the 5V line and it's capacitors become noisy too.

I have tried to change 100 uH coils to 220 uH, but it didn't change anything.
Please help.

Here is a link to full project and PCB design for more info

UPD1: The external power supply is not the issue. I tried to power the circuit from a different one and even from a 12V LiPo battery and the noise didn't change.

UPD2:
I measured the frequency of the timing capacitor charge/discharge:

The 180 step-up converter is running at 47 kHz

The 5v step-down is running at 49 kHz

I also noticed a weird behavior of 5V's timing capacitor when the LEDs are on

UPD3: here I found that capacitors used in switching power supply should be low-ESR. I am not sure, that my capacitors fit this rule. Here are the datasheets of my capacitors:

220uF: https://lcsc.com/product-detail/Aluminum-Electrolytic-Capacitors-SMD_220uF-35V_C3340.html

4.7uF: https://lcsc.com/product-detail/Aluminum-Electrolytic-Capacitors-SMD_4-7uF-400V_C88703.html

100uF: https://lcsc.com/product-detail/Aluminum-Electrolytic-Capacitors-SMD_100uF-35V_C88675.html

UPD4: I swapped all my electrolytic capacitors with low ESR ones, but the noise didn't change. I measured the voltage ripple of 5v line, it wiggles in 300mV window at approx 4kHz:


texts: Need help with configuration of a touch sensing lamp project!

texts: I am currently a design student in university, and am attempting to configure a large scale project for my final. The idea is that there would be a lamp, with one person holding onto either (wire? something? I have no clue how it would work) and it would turn on once two people touched their hands together to "complete" the circuit. Is there any insight into how this could work? I was thinking of using capacitive touch, or a touch sensor from a lamp, but need to somehow figure out how it could work that both touch sensors need to be touched in order to turn the lamp on. Any help or resources would be great!


texts:
I'm specifically talking about this:

I understand the difference between earth and ground, which is why I'm confused to see this being referred to both as "ground wire" as well as "earth wire".

Is this a American vs British English thing? Or maybe a common misuse of "ground"? Or..?

Also, asking this here seemed to make more sense than over at English SE. Or am I wrong?


texts: #2 L7809CV regulators, connected to #2 9vdc motors

texts:
I simply want to connect 2 motors as i show in the image, using a 12VDC power source and 2 #L7809CV, right now the circuit is this you can see in the image i made.
The GND its the same source for every wire connected to.

What happens:
When motor number 1 absorb power, motor 2 absorb the same power at the same time, and viceversa, if number 2 is on, number 1 power up too.

What i'm looking to do:
When motor 1 is absorbing power, motor 2 still off, and viceversa, if number 2 is On then number 1 still off, and the motors have to be powered on both, or turned off both.

Sorry my english, i think this its not hard to do so i post the image that can talk more than my english. I guess :)

Edit:

Here is an other image:

As you can see there are 2 pcb who command the input and output for each motor, those pcbs are powered on by a different 3,3v line but use the same GND of other components.

Its important to let there only one 12v source line for both L7809.


texts: How can I measure the current, in a precise way, using an arduino?

texts: I designed a low noise current source for a project in my university and I would like to know if it is possible to measure the provided current using an arduino and a LCD.


texts:
Consider you have 50 Hz both square wave as well as sine wave put on to a same speaker at different time. Which signal is more audible and what is the reason behind that ?

We know that by taking the Fourier series of the square wave we get multiple periodic sinusoidal wave, each having the frequency as the multiple of the fundamental frequency. So which will be more audible, whether a sine wave having single frequency or the square wave?


texts: How can a manufacturer verify a circuit design?

texts:
Could anyone tell me what  means (other than reversing) available to manufacturer of integrated circuits (latest Intel PC CPU's) that would allow them to verify that the actual design on die is exactly the same and identical to the blue prints or design circuit code ? I have heard of JTAG but don't fully understand this technology.

[Why the Question] The basis of the question is how can a manufacturer confirm and verify that no say RF based backdoors have been added to their design by its own circuit designers or by the factories.


texts:
First of all, apologies for posting this here, but I couldn't find any stack exchange hardware website. While plugging the headphones to my laptop it touched the USB port and I heard (through the earpiece) a plugging flicker sound. Then after a while I discovered that this USB ports along with the one next to it are not working so I guessed that they're connected in parallel. My question is : So what happened seems like a short circuit to me and I know they will never work again, but what if I tried to simply change the USB cores, are they gonna work , or might that be an irreversible motherboard issue?

Status: Resolved.
Credits to "DoxyLover"
Solution: It was a kind of motherboard automatic protection. I had to reboot the computer, log into the boot setup, enable and disable the USB devices from the Boot Menu. Thanks very much.


texts: How to connect wire to multiple part in EAGLE?

texts:
I'm a newbie in EAGLE, so I'll try my best to explain myself.

I need to connect a micro controller (port 19 and 18 in the pic) to two different components (pinhead and usb).

So, for instance, I've proceeded with: right-click --> Name --> USB_DP and I placed a label on the net, but how do I create a functioning connection for ICSP_DAT? In the image ICSP_DAT is showed that way just because I've added a text with layer 95 Names.

EDIT

As suggested, I used label 91 Nets for ICSP_DAT and left USB_DP as wire's name. This solution produces this result using SHOW command on ICSP_DAT's text and selecting wire 19:

Is it ok, or should I use label 91 Nets for both?
ERC gives a warning: "Only one pin on net ICSP_DAT" (regarding to the example above).

(I had to re-upload images to stay in the 2-images limit for "low-reputation" users, also I needed to show images to explain myself, I couldn't just comment below)


texts:
I was studying about Droop characteristics.

I came across the following flow path for a thermal plant

Plant is working at 130MW and 50Hz
Due to some load increase, frequency of the grid drops say 49.9Hz
Now based on the droop characteristic decided, you are bound to supply 140MW
Due to some reason you are not in a position to supply 140MW
You will request the people of Load Dispatch Center/Power Grid to allow them you to change the droop characteristic
After you get the permission, you can lower your drooping characteristic and continue supplying 130MW at 49.5Hz

After going through this, I have a doubt

How will the drooping characteristic be for a Nuclear Power Plant which follows Turbine follows Reactor concept ?

Do they isolate their plant by opening GTCB(Generator Transformer Circuit Breaker) everytime the grid frequency goes up or down ?


texts: Calculate torque from current induced in a single phase of a 3 phase AC Induction servo motor

texts:
I'm looking to measure the torque or slip angle on an AC induction (asynchronous) servo motor given the current induced in one of its phases. The servo and drive is yaskawa. Example data is shown above, the scale is in bit count from and ADC in a microcontroller. The picture shows a rapid movement.

I assume there isn't enough information given to calculate this? I've actually got access to two of the three phases in the servo motor sampled at 1000Hz.

My research so far has shown that torque can only be calculated if given the slip angle (or frequency?). However I've added a load to the servo and can see the average RMS current increase. This RMS value is taken for every 128 samples. Does this increase because the servo drive control loop increases the current to reduce the slip angle?

I've also found a rated motor-torque constant, does this apply for all motor speeds?

Thanks for your time!


texts: What is the X3 header on the Arduino Duemilanove used for?

texts:
Just got my new Ardunio, was up and running with my first C program in just 5 minutes :)

Looking at the schematic, it looks like the X3 header goes to the hardware handshake lines from the USB interface chip.  Any ideas as to what these are typically used for in Ardunio projects?


texts:
I coded a 4 bit booth multiplier in Verilog. It is working fine for

Multiplicand          Multiplier
+ 0 to 7        0 to +7 &  -1 to -7

But it does not work for

multiplicand         Multiplier
-8                 +1 to +7 & -1 to -8

Even I'm not getting answer through the algorithm by hand
example            -8 X 1

                 A            Q           Q_0    Control Bits         Cnt
               0000         0001          0    10  >> Subtraction     4
               1000
               -----
               1000
      ASR      1100         0000          1    01  >> ADD             3
               1000
               -----
               0100
      ASR      0010         0000          0    00   >> ASR            2

      ASR      0001         0000          0    00   >> ASR            1

      ASR      0000         1000          0    00   >> ASR            0

           PRODUCT = 0000 1000 = +8    NOT -8

Is it true, that Booth has a limitation that it can multiply only in the range of
           0 to ((2N) -1) &&  (-1 to -(2N)-1))

Like in this example

       + range  >>  0 to  7  Multiplied by (0 to 7) || ( -1 to -7)
                   -1 to -7  Multiplied by (0 to 7) || ( -1 to -7)

and not by -8?


texts: How do I determine if the clock signal suffers from high speed effects

texts:
I need to determine if the clock signal inside a multichip module shall suffer from high speed effects i.e reflection and ringing. I have:

(1) IBIS models of the components inside the multi-chip module

(2) The IBIS models in (1) converted to PSpice Models

(3) length of PCB tracks of the clock signals and the propagation delay on them and their characteristic impedance

(4) Cadence Design suite with the following software:

Allegro PCB Planner
Design Entry CIS
Design Entry HDL Rules Checker
Design Entry HDL
FPGA System Planner
Library Explorer
License Client Configuration Utility
OrCAD Capture CIS
OrCAD Capture LITE
OrCAD Capture View-Only
OrCAD Capture
Package Designer
PCB Editor
PCB Route
PCB SI
Physical Viewer
Project Manager
PSpice AD
PSpice Advanced Analysis
SiP Digital Architect
SiP
System Architect

There are also some more directories

AMS Simulator
PCB Editor Utilities
PCB SI Utilities
PSpice Accessories

What do I do next to carry out this signal integrity simulation? If the clock signal starts from the oscillator and then after a few milimeters, splits into multiple tracks which connect to different components, does that cause impedance discontinuity and thus high speed effects?


texts: Powering several buck converters in series and parallel loading the outputs for extra current

texts:
I'm using a high voltage DC 84v ebike battery to power several functions on the bike that need considerably lower voltage. It's impossible to find high current and wide voltage DCDC down converters that are also very compact.

So I wondered

Can I use three widely available compact 36v buck converters and wire the input in series to create a voltage divider. Then
Can i connect the three outputs in parallel to increase the load current capability.

I'm using these:

https://www.ebay.co.uk/itm/5A-Dc-To-Dc-Cc-Cv-Lithium-Battery-Step-Down-Charging-Board-Led-Power-Converter/122658609704?ssPageName=STRK%3AMEBIDX%3AIT&var=423065381521&_trksid=p2057872.m2749.l2649


texts: Sample Application with LHI 778 PIR Sensor

texts:
For a motion detecting application I found a sensor with code LHI 778.

If you look at the datasheet in the link, the characteristics of its internal FET transistor is not specified and there is no information about its internal sensor element. There for this sensor is too vague for me for designing a practical circuit. My aim is to design a circuit for security purpose which detects people passing by a window or house gate, both at night and daytime.

Can you tell me more about this sensor and offer a practical circuit which lights a LED when there is detection of any movement.


texts:
I ordered a 5 to 1 HDMI Switcher with remote. I was looking for the lowest price way to switch analogue audio RCA/3.5mm stereo. At the time I ordered this my decision was based on the availability of hdmi to rca audio cables. I know they make cables that are useless.

Is it possible to use any of the connections on the hdmi cable to switch analogue audio?

Or any thoughts on a low priced solution to switch analogue audio with a remote?

Thank You for all replies! Kevin


texts: Help me to understand the working of induction cooker circuit

texts:
I am new to electronics So I need help to understand the working of the induction cooker circuit. I searched on the google but could not find the simple answer. Below is the attached circuit commonly found in home based induction stoves but it seems to be totally different from the theoratical circuit on the internet. In this circuit, as per my understanding, the ac supply is passed to rectifier that converts it to pulsating DC C2 capacitor is used to smooth the voltage and then this voltage is injected to the mosfet where low voltage signal can be used to control the mosfet(switch). If the switch is on then the induction coil starts. So its all the process is to convert AC to DC and then using the switch to on off the circuit.

My quetions are.

What are the purpose of capcitor C1 and C3 and inductor L1 in this circuit?
Does the induction cooker main coil is operated on DC Voltage?
Why the fuse blows when I directly provide the AC voltage to Main induction coil L2. Shouldn't Magnectic field arround the coil provide some resistance for the current flowing through it.

If I am getting something wrong, please correct me. Would be greatful for any help.
Thanks in advance.


texts: I have a lamp in my flat that can be turned on and off with two different buttons, how does a circuit look like to realize that?


texts: Does reverse biasing hold any meaning in case if both terminals are n type semiconductors?

texts:
When we talk about an n-p-n transistor in common emitter configuration, we often say that emitter-collector circuit (the one towards right) is reverse biased. In what sense it is reverse biased?
Here, both terminals are n-type, for such a thing to be reverse biased must not we put positive voltages across both the n-type terminals?


texts:
Ok, I feel like this question is a bit underqualified for this site but I couldn't find anything better. Anyways. I have almost no knowledge about electronics, so sorry for the stupidity.

I want to connect several RGB LEDs with a 3 way switch (state 1, state 2, off) so that on state 1 the LEDs are blue and on state 2 they are orange. I basicly don't know how to control the LEDs. How would I solder it together? I know that I need resistors, they shouldn't be the problem though.

My powersupply would be a 3V Battery.

EDIT: These are the LEDs,
I couldn't find any more info on them.


texts:
I am new to this site, so please bear with me.
here is plot of the step response of first order system given

Now, the question is to find time constant as well as DC gain so I can find it's transfer function.
here is my attempt, but I am not sure about finding the time constant.

I read somewhere that time constant for first order system is  t=5*tau where t is the time when system reaches its steady state value, so tau=3/5 ?
is this correct?


texts:
Speaker manufacturers often state crossover frequencies in the specs. What is the importance of this value?

Let's take for example two equivalent active powered 2-way boxes with crossover frequencies set to 900Hz and 800Hz. What would be the difference? I remember having read that lower crossover levels allow the woofer to reproduce better lower frequencies and/or extend its low end frequency response.


texts: is it possible to control the speed of a bldc motor using a direct connection to ATMEGA32 microcontroller? Or there should be an interface since motors need more voltages than the microcontroller (correct me if I'm wrong)


texts: Arduino UNO sensor works fine when connected to laptop but gives problem when connected to external power supply

texts:
I have encountered problem with Arduino UNO and water flow sensor. So here's situation:

I have connected a 12 V power supply from DC battery and then used 5 V regulator which output is used as input to 3.3 V regulator.

Ground of all power supply is the same that is ground of 12 V. It is connected to 5 V and then 3 V. I have a water flow sensor which uses 5 V from output of the 5 V regulator also this output is used to power the Arduino.

When serial port is connected to a laptop, the sensor works fine and gives accurate output. But when serial port disconnected sensor gives output even if there is no flow of water.


texts: Bridger rectifier producing non-equal voltages

texts:
I am making a bi-polar 12V power supply with a centre tapped (12-0-12) AC transformer. On inspecting the voltages after the bridge rectifier (KBU-4B), the negative side produces -26V and the positive produces +10V.
Both sides have a 470uF cap before and after their voltage regulators (L7812-CV and L7912-CV) for smoothing and a 4.7k resitor at their outputs to simulate a load. Their outputs after regulating are +9V and -12V.
As both sides of the circuit are identical I would assume their outputs should also be identical. Is there something I am overlooking here?

simulate this circuit – Schematic created using CircuitLab
The PCB below contains the + and - 12V outputs and a +5V output running off the +12V. I have disconnected the trace running to the 5V output whilst trouble shooting the asymmetry from the bridge rectifier. The output LEDs have also been replaced with 4.7k resistors


texts: How do you design processors / microprocessor [ not broad ]

texts:
Apologies for this vague title, but my question is a little specific.

I have two concerns :

During my digital electronics class, I was told that the design of the processor is first carried on an FPGA board and verified. Only then it is finalized. In order to design the processors on FPGA board, you use Verilog and VHDL, and then let the tools do the heavy lifting. These tools then infer or deduce a schematic / design from our program. Also, simultaneously, another team of engineers is busy programming test benches and carry out verification and simulation etc.

My first question :

If you let the tools do the designing portion of your processor (or microprocessor),
then wont it always infer the same circuit, or at least nearly same circuit
for your processor ?

For example, as one of lab exercises, we were required to program a 4 bit ALU on xilinx ISE in verilog. As long as we had the same instructions / operations/ functionality for our ALU , if we let the tools design ALU, wont it always design the same circuit ? I believe this because ultimately at the transistor level, an AND gate (just an example )will always be composed of, lets say 5 mos transistors (as provided in the library of components ). Also ALU will always contain same blocks / nearly same blocks like adder, subtractor etc ( In other words, same design will be inferred).

My second question :

If I am correct above ( which obviously I doubt ), then how would the designs differ ?
In other words, where lies the role of a human / engineer if everything is
done by the tools .

As another example, Intel produces processors. If we for the time being assume that they produce on 28 nm, and will continue to do so for another 5 years ( just an example) . Then how is it that they come up with fast processors every year or so ? I am confused because at the end of the day, Intel itself will obviously be using these kind of tools (verilog / vhdl) to design their chips. So as long as they have a functionality which does not change, they should always come up with same design.

Please understand that this is not a broad question. It focus on the automation aspects / designing using tools only. Also I am not concerned with advances in computer science concepts, such as introduction of pipelines etc which improved performance. I am only interested in above mention aspects.

I am asking this because I am little interested in designing a small microprocessor before my graduation. But programming a couple of lines in Verilog / vhdl and letting the tools do the job does not seem to excite me at all.

Thank you.


texts: AVR regulation brushless vs. brush alternator

texts:
I am currently looking for an AVR for a brush alternator. Today, brushless alternators seem to be more common and so is the supply for AVRs to work for brushless alternators.

My assumption is that the basis principle of an AVR is to sense alternator output voltage and to adjust excitation power.

So what is the difference in design principle of an AVR for a brush vs. brushless alternator?


texts: Can an RMII phy be connected directly to another RMII phy

texts:
I have some Microchip (SMSC) LAN9303 Ethernet switches in my system.  The LAN9303 is a 3-port switch which has 2 connections for twisted pair cables and one MII connection.  The switch chips are some distance apart and each is connected to an FPGA which in turn is connected to a very high data rate link.

The idea was to link the switches via their MII ports so that equipment plugged into switch 1 could talk to switch 2.  To do this one LAN9303 was set up as an MII Phy and the other as an MII MAC.  Thus one switch thought it was a mac talking to a phy, and the other switch thought it was a PHY talking to a MAC.  This worked ok.

Now, to save pins, the LAN9303s have been connected using RMII.  As the LAN9303 can only operate as a RMII PHY (not a MAC) I have 2 RMII PHYs connected together.  They're just connected with wires at the moment (about 20mm long), as I want to get them working like this on the bench before connecting into the larger system.

The LAN9303 allows the RMII clock to be an input or an output, so I have one switch providing the clock as an output and the other has the clock as an input.  This seems to be working OK.

I've tried to read up on this but I've had trouble finding out much what the data coming in to and out of an RMII phy should look like and whether the data it expects to see from a MAC looks like the data is sends out to an RMII MAC?


texts: Why does the current intensity decrease when I connect two voltage sources in series?

texts:
I actually connected lemons with batteries and I found that the voltage of lemon and the battery (i.e. the bottom left circuit) is 3.8V while the current intensity in the top left circuit is 0.1mA!

The question is why the current intensity in the top left circuit is 0.1mA while the current intensity in the top center circuit is 1.56mA and the current intensity in the top right circuit is 0.013mA?

simulate this circuit – Schematic created using CircuitLab


texts: Is MATLAB HDL Coder viable for complex FPGA designs?

texts: I'm building a feed handler for an FPGA and, having never done this before, I'm wondering if I would be OK using MATLAB (HDL Coder) as an alternative to VHDL. Is this generally a viable options, do people ship hardware designed in MATLAB?


texts:
I am a software developer who wants to learn more about how Computers work at a lower level.  I did GCSE Electronics 16 years ago.

I have bought an Electronics starter kit, which contains this component.  The shop assistant described it as a Breadboard but after a bit of Googling I believe it is a PCB as described here.

It was part of a starter kit.  Do I have to solder components onto this board in order to test circuits or can I just plug them in like with a breadboard?

I realise that this is a basic question but I have spent some time Googling.


texts: Light sensor detecting when the lights turns on AND when the light turns off

texts:
I would like to create a circuit using photodiode that detects when the lights turn on AND when the lights turn off.
The output should look something like that:

I want to create the simplest possible circuit. The precision is not important, only reliability. The minimum distance between voltage spikes will be in order of seconds. The duration of spikes should be about 100ms.
I would be grateful for at least some keywords to google the solution. So far I found only circuits detecting when the light is on.
Thank you


texts: What does this schematic symbol represent?

texts: What is this symbol from an automotive schematic?


texts: Confusion with TRIAC firing and zero crossing point

texts:
The reason for firing a TRIAC very close to the zero crossing point is explained as to avoid RF or EMI interference. Below is an excerpt from a book:

What I'm having trouble to understand is that, if one injects firings to the TRIAC very close to the zero crossing points, how then it is achieved the full control of the power delivered to the load?

I mean if the firing is always in the neighborhood of the zero crossing point how can one reduce the average power to lets say %50 or %60 ?

I'm really confused..


texts: How do I reset my registers on Digital Clock Manager output?

texts:
I am using a SPARTAN 3E and have used the DCM core to generate a 50 Mhz to 25 Mhz clock to drive the VGA PORT.
The reset logic I'm using is shown here.

DigitalClockManager instance_name (
.CLKIN_IN(CLK_50MHZ),
.RST_IN(rst_in),
.CLKFX_OUT(clk),         //25 Mhz
.CLKIN_IBUFG_OUT(CLKIN_IBUFG_OUT),
.CLK0_OUT(),
.LOCKED_OUT(LOCKED),
.STATUS_OUT(STATUS)
);
BUFG buffer (.I(CLKIN_IBUFG_OUT), .O(CLKIN));

RESET LOGIC :

    reg LOCKED_R;
reg [3 : 0] SR;
always @ (posedge CLKIN)
begin
    if(RESET)
    begin
    SR [3 : 0]  <= 4'b111;
    LOCKED_R <=0;
    end

else
begin
LOCKED_R <= LOCKED;
if(LOCKED < LOCKED_R | STATUS [1] ) // H to L on LOCKED | CLKIN UNSTABLE
SR <= {1'b1 , SR[3 : 1]};
else
SR <= {1'b0 , SR[3 : 1]};
end
end

assign rst_in    = ( (SR[2] | SR[1] | SR[0]) || RESET);

Now, I am not sure about how to implement reset for all the other registers in the design.

    always @ (posedge clk)
begin
   if (LOCKED && !STATUS[1])
    begin
           //GOOD TO GO
    end
    else

    begin
     //RESET
    end
end

If the RESET signal pulse lasts for a period shorter than what it takes to assert the locked signal, (which probably will be the case because of the OR gate at the rst_in), the registers will never be reset.

Does the always @ (posedge clk) trigger even when (LOCKED && !STATUS1) isn't high?If so, why doesn't the else part trigger and set registers to default values?


texts: Emitter resistor in common-emitter amplifier

texts:
I know that in common emitter amplifier, \$R_C\$ has effect on output swing and also on gain. and the two resistors \$R_1\$ and \$R_2\$ stabilize from \$h_{fe}\$ change.

simulate this circuit – Schematic created using CircuitLab

But the question for me is how to choose the best resistor for \$R_E\$. As it has effect on \$V_{CE}\$. When we increase \$R_E\$ the \$V_{CE}\$ decreases. And also it has no effect on voltage gain.

At the other hand we can have constant \$I_c\$ by choose appropriate \$R_E\$ and different \$R_1\$ and \$R_2\$.

What limitations should be considered in order to choose best \$R_E\$?


texts:
simulate this circuit – Schematic created using CircuitLab

We can easily implement transmission gates in Low voltage levels 5V maybe 12V but, when it comes to high voltage, like 100V many transistors can not handle  that voltage difference between Gate and Source. I've been researching this for a while and stilll can not find anything about high voltage transmission gates.

Transmission gates are very useful in many ways. They do not consume energy in static state, they are bidirectional, their ON resistance are very low. But, what I am wondering about is can I implement this structure in high voltage with same features as it has in CMOS process(low resistance, bidirectional and no static state power)?