texts: Design a simple circuit to generate variable +5V to -5V signals

texts:
I want to design a simple circuit that takes 12V from a battery and generates two signals each of range -5V to +5V. These signals are input to a 2-Channel ADC.

I want to be able to change the voltage through the whole range using a pot to test the dynamic performance of the ADC.


texts:
I was calculating ESR for this ceramic capacitor, Samsung P/N CL21A226MQQNNWE.

Per the datasheet, DF is given as 0.1 max at 120 Hz.

Per formula, ESR = 0.1 / (2 * Pi * 120 * 22uF) = 6 Ohms.

What am I doing wrong, or is the ESR really 6 Ohms? That just seems way too high for a ceramic capacitor.

I feel a bit silly asking this, but hey, if I am confused someone else probably will be, too.

ADDENDUM
Basically, the ESR for MLCC capacitors is surprisingly high at low frequencies. However, in my application, the ESR at higher frequencies is what was of interest. The graphs provided by several answers were super helpful and show how much the ESR changes with frequency. This is not something I knew about when I asked the question. I just knew that MLCC's supposedly had very low ESR (everybody knows this, so it must be true, right?). Anyway, now everything makes sense.


texts: Switching a 1mm JST header to 2mm / adapters

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I had a number of custom PCBs made using 7 way JST headers, however the hardware that plugs into them arrived today using a totally different pitch measurement than what was described..
In an ideal world I would just ship them back and look for a replacement but they've taken weeks to arrive, so I just want to make use of them.
My boards use a 1mm pitch however the female connections from the external hardware use a 2mm pitch - are there such adapters that I can create or purchase to fix this?
Just to clarify they are single row 7 pin headers with a 1mm pitch.


texts:
So, here's the circuit:

How can I make phasor diagrams for the circuit in case when $$I_C<I_L$$ and $$I_C>I_L$$

Edit: What made me confused is the current conditions, it's actually voltage $$U_C<U_L$$ and $$U_C>U_L$$


texts: 5 volt regulator not getting desired output

texts:
I have been trying to assemble a simple 5V regulator circuit using the L7805CV and have had no luck at all getting the output to 5V. I have tried many circuits and multiple L7805CV regulators, thinking that maybe it was the regulator itself that wasn't doing its job.

So far the closest I've come to 5V is 6V, which won't work for what I'm trying to power.

First, I tried the simple circuit with a 10uF cap from input to ground pin and 1uF cap from ground pin to output, and was getting 3.8V output with an input of 9V. I was getting 11V out with a 12V input.

I tried another one that was similar but with a 1K resistor connected to an LED on the output, which gave me 6V. I thought maybe the capacitors were the cause so I tried  going with 100uF from input to ground and a 10uF from ground to output and another 100nF on the output for filtering and still no luck. I basically played with cap values all the way up to 2200uF and didn't get anything close to what I needed. I either got really low (about 3V) or really high (close to 12V) on the output and also tried different input values of 6V, 9V, 12V, and even 18V and nothing worked.

I used a heat-sink on the l7805CV and am stumped how this is happening. I eventually went back to one of the first designs that had the output of 6V and tried using a diode on the output for its voltage drop and was getting almost the exact reading on the output (actually a few mV higher) and am stumped at this point. After a while I got bored and tried out a few different transistors I had around to see how they would affect the circuit and was surprised to find almost exact results.

What am I doing wrong? How can I successfully achieve 5V on my output?


texts:
This is an inverting op-amp with closed loop gain \$A\$. The question is theoretical, so op-amp is ideal.

simulate this circuit – Schematic created using CircuitLab
I was trying to find the input impedance \$Z_i\$ of this Op-amp. Let \$i\$ be the current coming out of \$V_i\$. Then \$Z_i = \frac {V_i}{i}\$
In the  first case, assuming inverting terminal is at virtual ground \$V_i -0 = R_i \times i\$
$$Z_i = \frac{V_i}{i}=R_i$$
But when I apply KVL along \$V_i - R_i- R_f- V_o\$ assuming no current is entering the OP-amp.
$$
V_i - i.R_i - i.R_f -V_o=0
$$substituting \$V_o = A.V_i\$ $$
Z_i = \frac{V_i}{i} = \frac{R_i +R_f}{1-A}
$$
Which \$Z_i\$ is correct


texts: How to select LEDs for use as colour selective photodiodes?

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When selecting LEDs for use as photodiodes, are there general guidelines that one can use to increase the odds that a more suitable LED is selected?
For example:

Does diffuse or clear impact efficiency as a photodiode?
Does a brighter or dimmer LED tend to correlate to better performance as a photodiode?
Can the output spectrum of the LED be directly taken as the sensitivity spectrum of the photodiode?
Does the LED output field of view correlate with the field of view when used as a photodiode?
Are there any characteristics of an LED that would tend to correlate towards larger die-size for increased sensitivity when used as a photodiode?
Would a monochrome LED with a transparent, untinted, clear resin package be sensitive to only its output spectrum when used as a photodiode? Or would it be different?
Would a monochrome LED with a tinted resin package only be sensitive to its output spectrum when used as a photodiode? Or would it also be sensitive to near-IR that can easily pass through the resin?


texts: Does resistance decrease over a resistor?

texts:
If ohms law pertains to voltage, current, resistance across a resistor, in order for voltage to drop, and current to remain the same, does resistance drop as well across the resistor?

To explain what I mean, if we have the circuit:

The voltage across the first resistor drops linearly from 5v to 1.667v. Let’s say we picked a point around the middle of the resistor and read that the voltage at that point was about half of the difference across the resistor, so 5v - [(5v - 1.667v) / 2] = 3.3335v.

From what I as told, current across resistors in series is constant/equal.

So if the voltage at that point is 3.3335v, the current is fixed at 1.667A at that point and every other point across the resistor, does this mean that resistance is dropping throughout the resistor as well to compensate for the voltage drop and so ohms law remains valid?

Because at that point if voltage = 3.3335v and current is 1.667A, resistance at that point would have to be 1.999700059988002 ohms, given by V=IR.

At a point somewhere between the middle and end if we measured the voltage and got 2v for example, R = 1.199760047990402 ohms.

Overall, this would show a downward trend in voltage, a constant current, but also a downward trend in resistance.

But is this correct? And if resistance is also fixed, how is it possible current can remain constant when resistance is also fixed and voltage is dropping while obeying ohms law?


texts:
Here is my hand cranked generator for charging a high voltage capacitor. How the system is designed to work is shown in the following image:

It is designed to charge the 10 mF capacitor to upto 50 V and to provide 5 V at 100 mA. While testing the output of the circuit by connecting an LED with a resistor in series, a strange behavior is noted: When the capacitor voltage is 50 V and discharged through the 3.5 V LED and an 82 ohm resistor, the current through the LED is limited to around 18 mA which is what I am looking for until the voltage drops to around 34 - 35 V when the current shoots up to 150 mA and stays that way till the cap is completely discharged. When it is again charged to around 30 - 31 V, it exhibits the same behavior when voltage reaches to 26 - 27 V. The similar behavior can be seen at different voltages of charge-discharge cycle. What is this strange behavior? Can it be something to do with the inductor?

Thanks.

Add1: Image edited. Here is the datasheet link. While it is mentioned in the datasheet to use ferrite pot-core inductor or toroid type inductor, I managed to get DR type inductor of 470 uH value which just looks like this:

.

Add2: I am not having oscilloscope so I don't know the exact behavior. But, I have noted the following.

Condition: Capacitor is charged to about 30 V.

Case 1: Nothing is connected at the output. Almost same voltage as that of the capacitor.

Case 2: Only resistor at the output. I see only 1.5 V at the output with the current remaining unchanged at around 18 mA. When the voltage drops below 26 - 27 V, the output current rises to more than 150 mA and the voltage rises to more than 15 V.

Case 3: Resistor with LED at the output. Around 18 mA at 5 V. Similar behavior when voltage drops below 26 - 27 V.


texts:
I am using a Texas Instruments CC1110, which is based on the 8051 microcontroller. I'm programming it using the IAR Embedded Workbench.

I have written a function named sendChar that sends a 8-bit char over the UART interface.
Running the following code:

sendChar('H');
sendChar('e');
sendChar('l');
sendChar('l');
sendChar('o');
sendChar(' ');
sendChar('W');
sendChar('o');
sendChar('r');
sendChar('l');
sendChar('d');

Results into the expected behavior of Hello world being sent over the UART channel. But then defining the sendString function as:

void Serial::sendString(char *str) {
  unsigned int i;
  for(i = 0; i < strlen(str); i++) this->sendChar(str[i]);
}

and running the following code:

sendString("Hello world");

results in 0xFF being sent more than 100 times.

I have noticed that sending the strlen output with the sendChar function reveals that the wrong string length is being generated. For example, if I run the following code:

char str[100] = "Hello world";
sendChar(strlen(str));

I receive 101 instead of 11 as one would expect.

What am I doing wrong?

Edit

If I run the following code:

char str[100] = "Hello world";
sr.sendChar(str[1]);
sr.sendString(str);

one would expect to receive eHellow world, but instead I receive 101 dots . (0xFF).

Edit 2

Complete code:

#include <ioCC1110.h>
#include <ioCCxx10_bitdef.h>
#include <math.h>
#include <string>

void sendChar(char c);
void sendString(char *str);

void main(void) {
    CLKCON = 0; // Crystal oscillator, no pre-scaler

    U0CSR |= U0CSR_MODE; // USART0 in UART mode
    P0SEL |= BIT3 | BIT2; //P0.2 and P0.3 as peripherials

    // Baud rate = 9600 (9597)
    U0GCR |= 8;
    U0BAUD = 131;

    // Enable Rx and Tx interrupts
    IEN2 |= IEN2_UTX0IE;
    URX0IE = 1;

    while(P0_4); // Wait for P0.4
    char str[100] = "Hello world";
    sr.sendString(str);
    while(1); // Wait so main() never ends

}

void sendString(char *str) {
  while (*str) sendChar(*str++);
}

void sendChar(char c) {
  U0DBUF = c & 0xFF;
  while(!UTX0IF);
  UTX0IF = 0;
}

Edit 3

I ran a simple main:

int main( void ) {
  char str[] = "Hello world";
  CLKCON = 0; // Crystal oscillator, no pre-scaler
  P2DIR = 1; // P2.0 as output
  P2 = 0;
  char l = str[2];
  Serial sr;
  while(P0_4);
  sr.sendString(str);
  while(1);
}

and debugged it. Here is a screenshot of the value of the str array.

Its full of dots, as I reported previously.

Any idea on what's causing that?


texts: How did we count this open circuit voltage?

texts:
I am supposed to solve (to find voltage and current on resistor R2) this circuit using Thévenin's theorem. How did we get the formula for open circuit voltage? And why are we treating resistances as conductances?

Moreover, I don't seem to be able to find generally applicable way to calculate Ui. I'm really new to circuits and the formulas for Ui seem to be significantly different for each different circuit.


texts:
I am working on a PFC for a final project.  The PFC is based on several sources and runs in CCM, currently have it working with a very noisy current waveform.  My original design was to use a 60kHz PWM frequency, but as I am using C functions as opposed to assembly, the platform (C2000 Launchpad) I am using is not fast enough and currently running at 25kHz for the PWM.

So I am looking to improve my algorithm and hopefully increase the PWM in the process.  Which brings me to the Texas Instruments Application Report SPRA902A.

At the top of page 10 there are 3 equations, and I am able (95% sure) to identify all the parameters except for 1, which is \$U_s\$ which forms the term \$Epi\$.  The equations are below:

$$U_{CA}(n) = K0 \times E(n) + I(n-1)$$
$$I(n) = I(n-1) + K1 \times E(n) + K_{corr} \times Epi$$
$$Epi = U_s - U_{CA}(n)$$

I can see \$U_s\$ in the expression, but how is it derived?


texts: Transistor as switch in variable voltage environment

texts:
I'm using a 3.3v arduino pro mini to make a solar-powered "garden bot." All the bot does is use a capacitive moisture sensor (which can accept a supply voltage between 3 and 20v), and turn on a solenoid if necessary. This project uses a solar LiPo management circuit that supplies power to the arduino from either the battery (a 3.7V LiPo, that can realistically vary between 3.4V and 4.2V), or, if there is a surplus, directly from the solar panel (5-6V, depending on conditions).

One thing that's critical here is being able to put the whole thing in as deep a sleep as possible when it's not checking things. When sleeping, the whole thing eats about 300uA. The sensor, when energized, eats about 7mA. Since this is a relatively large amount, I'd like to disable the sensor when not in use.

I'm a transistor newbie, so I've been following various tutorials on this. I'm using a BJT to control supply current to the sensor, following this design:

sample transistor as switch circuit

The problem is that Rb is a function of both the base voltage and the collector voltage, and that value may fluctuate depending on power conditions. I can't use a regulated arduino rail because it would be at a max 3.3v, and by the time the transistor takes away its .7v, i'm left with less than the sensor's minimum 3.3v. Is there any way to make this work without involving some sort of step-up transformer? It's not a huge deal to do that, but ends up being more components and more power consumption when the sensor is powered.


texts: How to troubleshoot this bandstop filter circuit....?

texts:
Circuit is for 2nd order band stop filter...from 1.2 kHz to 6.2 kHz....
But the circuit is not working as shown in bode plot...
Cutoff frequency is also not coming right at -3dB .......
What changes are required....?
I have tried by varying resistance at load....but nothing happens...


texts: convert momentary switch to toggle switch using 555

texts: this circuit diagram is used to convert a momentary switch to toggle function , how can i extend the diagram to get three output stats to switch between two LEDs and an off state if it possible


texts:
I am working on a idea. The idea is to measure current from a current source, which transmits 3 levels (ex: 10 20 30mA). Which if possible should be logged, representing 3 states with 3 different variables ( ex: 0= 'A', 10='B', 20='C', which these may be used for someother processing).

The approach I have in my mind is to use
1) Current sensor for Arduino interface --> From Arduino the output (But I need to collect (mostly live data) the data in digital form depending upon the current level, as mentioned above(with some help of C++ libraries I will be writing and using in the arduino source code))waveform to be logged as digital data (May be txt or csv representing current levels in 10 20 30 as A B C etc).

My doubts-

1) Am I missing any logic here?

2) Should I have to be aware of any challenges that I have not counted for!

3) Any tips for data data log from the arduino.

I have worked on arduino, but I am not a expert. Any kind of help or directions will be helpful.

(Edits- the input current will represent a encoded value in the form of current sink, which I am planning to decode)

Thanks,

Ray


texts: Time Synchronization between stations over WIFI 802.11n

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I'm working on a wireless (2.4Ghz WiFi 11n) project where multiple nodes (ESP32) send very small data to the AP, something like 40 bytes every minute or so. I need to maintain an accurate coordinated clock between them, absolute accuracy doesn't matter, but they must match with each other to at least 1ms (or better).

As GPS signal is not guaranteed at the location, I prefer not to include it in the design and I was thinking using the server (laptop wired to AP) to send a UDP Multicast timestamp every, let say, 2 seconds. The nodes are in constant movement (with vibration) so they may drift faster, anyway, I have doubts if this alternative would be able to work as I expected and I would like to know any other alternative or improvement of this system

At the moment, I have these unknowns that I would like to get an answer to:

Expected delay if AP is already busy sending / listening in the very
exact moment it must emit the timestamp
Is there any physical reason (Multipath, bad signal, whatever)
that one or more nodes doesn't receive the UDP at the exact
moment? With exact moment I mean between a millisecond
Is there any chance of ESP32 slowdown or hang by another task and
receiving the UDP packet pretty later?


texts: Rules for Block Diagram Reduction, how to do this

texts:
I have to solve, to reduce this block diagram:

But I don't know how to do it, I know somthing about the rules to do it, but its to basical, this complex. I tryied to do this :

And now?


texts: Lithium discharger with what I have laying around the house. Review pls?

texts:
I'm trying to MacGyver my way around discharging some lithium ion cells down to a set voltage I can safely store them for maximum life.
My main issue was I don't have a decent voltage reference as low as these 1865 go such as a linear regulator or Zener so I used a LED.
Basically I compare the drop across the LED with the voltage across a trimmable voltage divider using an opamp with no feedback, feed the signal to a n-mosfet which drains ~350mA over a 7.5ohm / 5W resistor.
First issue: Thermal stability
Using a hair drier to test thermal stability shows I can set the device to discharge the cell down to 3.5 V, but apply heat and the cutoff point goes to 3.3V. I think the main culprit is the LED. Does anyone know any way to make this more stable? Like using a similar LED to balance things out? Got to say: I don't expect hairdryer temperatures on my led any time soon. But I'm no expert in thermal runaways
Second issue: Safety
Should I be able to sleep while I have this thing working? Does it come down to implementation or is this simple circuit intrinsically unstable toe to thermal run-off potential?
Third issue: Do I need to cool that 5W resistor? Is it safe if it goes up to 60*C as long as it's rated to 5W? Gotta say, it's pretty close to maximum rating. I have two of those. I could use both in series, but I'd rather pull more current. I also have a 1ohm 100w resistor, maybe 8.5ohm  (the two combined) is the sweet spot? Or maybe I should limit the base voltage in the mosfet.
Thank you.
Circuit:
Forgot to say: I used this mosfet
And measured

VBE = 1.5v
Rds 1.1ohm
temperature: 43*C


texts: Are Schmitt trigger and peak detector comparator the same?

texts:
Here is a peak detector comparator schematic ,its symbol,and its simulation.I have some question about them.

First,we all know the Schmitt trigger symbol is the same as the second picture,so are Schmitt trigger and peak detector comparator the same ?

Second,If they are actually the same,its simulation seems strange,i know the process of Schmitt trigger,the reason i think strange is that why is that two input are rising,but the output become low.The output become high,only at the red line rise rapidly

(1) peak detector comparator schematic

(2)Symbol

(3)Simulation


texts: Im not sure in how the Distributed RAM is implemented using LUTs. Would the inputs be used for both address, control write/read and data signals?


texts: Isolating BNC connector from test shield

texts:
For my project, I need to have BNC connectors on the test metal shield. So what I did so far is drilling holes, and mounting BNC connectors on it:

I used some hot shring on the part which passes through the hole. Those washers are normal fibre ones. I don't have something better at my arsenal now. This will not be a good insulator, because I measured the resistance from outer bnc connection to the metal shield and it happend to be around 1.4 GOhm:

The problem is, the signal LO (the outer connector of coax cables) should be totally isolated from the metal shield. The best thing I can think of is some sort of teflon washer (shoulder washer) that can pass through the hole of the metal shield and then I can insert the BNC connector through it. Unfortunately I was unlucky to find what I need. What I have found is made from nylon and I think it can not provide a resistance as good as teflon, also it has the problem of absorbing water (humidity) :

Please let me know what you think, and would be nice if you know a place that I can order the required stuff!


texts: wall warts: constant specified current though universal input voltage?

texts: How come the input drawing current be constant (1.5A) even though it shows that the adapter is universal input (100-240V)? I mean that the power supply voltage varies in different locations still how come the current be same.


texts:
I suppose this is simple one, but for me as first time reader of STM32F769 datasheet it is confusing. Memory map in this datasheet declares ITCM RAM at zero address, while this programming manual (pg. 32) declares that zero memory is code space (which by my opinion must not be RAM).
My expectation is that's all about some kind of aliasing, however didn't find confirmation in datasheets. What am I missing ?


texts: "Old FM" vs. Modern FM radio signal. What's the difference and can I adapt?

texts:
I have a vintage radio that I managed to get all circuits and tubes back into original spec. The AM stations tune in fine but I get nothing on FM. I am told this is because it's tuning in "Old FM" - which I can only assume was part of the APEX broadcast band (42mhz - 50mhz)? Or, is this a reference to some band of UHF/VHF? It's not clear to me.

Depending on the answer to the above, might it be possible to put a line-level adapter on the antenna so I can use all the vintage hardware to tune in a few modern stations?

update
Model is 1947 Magnavox Georgian. Schematics to come


texts: Can the DS1052E be used for reliable NTSC measurement?

texts:
I'm in the market for an oscilloscope.  I've read that the infamous DS1052E from Rigol is a great beginner scope due to the price/performance.

However, I know I have a lot to learn and simply don't know if it's the scope I need.

My intentions are to build circuits such as audio cards for 8 bit computers, Ntsc video cards for 8 bit computers, etc.

Generating an NTSC signal (accurately) would probably be my biggest goal.  However, I may dabble with standard VGA generation.

I've done this in the past but never had a scope to measure.

So my question is would the DS1052E be good for this kind of work?  VGA as well?

BTW, I'm not really interested in hacking the scope for higher bandwidth.  I've read you can brick it and I'd hate to risk it.

EDIT
I removed the reference to my budget.  After that, I'm not sure if this really warrants being put on hold as I am not asking for a scope recommendation.  I am asking if a particular scope will handle a valid use-case.  And since I am very new to EE and oscilloscopes in general, hopefully this will fit the requirements of the site.


texts: Dotstar Light Strip Low Update Frequency

texts:
I've built the start of a persistence of vision display. The rotation platform itself is built and I have just mounted the LEDs. After doing some testing, I can only get very slow update speeds of the lights themselves. I am using a very simple for loop in Python3 on a Raspberrypi 3B+ using GPIO 10 and 11 to control the strip. The strip is managed by the Adafruit Dotstar library and is controlled by the SPI bus. I choose this  Light Strip as it is a clone of the APA102c and is ideal for Persistence of Vision displays. The code below works as design it will travel down the strip and update each LED but quite slowly. Could this be a limitation of the Pi's speed? I feel as if it would have more than enough power for a list update of this nature.
import board
import time
import adafruit_dotstar as dotstar

#Reversed Order
dots = dotstar.DotStar(board.MOSI, board.SCK, 72, brightness=.2)
#Default From Adafruit
#dots = dotstar.DotStar(board.SCK, board.MOSI, 72, brightness=.2)

n_dots = len(dots)
for dot in range(n_dots):
        dots[dot] = (0, 0, 0)
#time.sleep(1)
start = time.time()
for dot in range(n_dots):
        dots[dot] = (255, 255, 255)
end = time.time()
timetoloop = end-start

print ('Finished %.2f'%timetoloop + " Seconds")


texts: how to wire NPN to switch DHT22 temperature humidity sensor on arduino

texts:
I am using the arduino with DHT22 temperature, humidity sensor, but i don't want to constantly power the sensor, so I would like to have a NPN 2N2222 transistor to control when to the give the power.

but i am a bit puzzled how to wire them together, which how the collector and emmitter should be wired to DHT22 sensor


texts:
I've been messing around with a noise circuit utilising a zener diode.  As I understand it, the white noise is (effectively) of infinite bandwidth, from 0 to a Gazoogle Hertz.  It's going through a LT1011 comparator which is rated to 10 GHz.

Clearly a wire wrapped (or point to point wired) circuit board won't manage the GHz range, but what will it manage?  I know they used to wire wrap mainframe computers.  Those photos are total rats' nests, and must be loaded with parasitic /stray capacitance everywhere.  An estimate of magnitude would be useful.  Might you get a meg?


texts: Please help me understand modbus communications

texts:
I'm just starting out with understanding how modbus works over a rs485 protocol.

I've received a communication protocol document from a company that makes solar inverters.

I want to send a command to the slaves but the documentation notes that I need to send a command + a sub-command.

I'm given a table of protocol characters and a communication table.

Since I'm new to this I'm having a hard time understanding this.

The protocol table:

And this is the communication table:

How would the packet look in hex if I would send the following details:

Slave address: 4
Command: 32
Sub-command: 3

I do understand I need to start the package with the STX, ENQ hex codes. But I have no idea how to construct the rest of the package. Especially the (N, N + 1, N + 2, N + 3) part.

Is there any tutorial that will explain how to construct a package?

I don't understand how I need to provide a value for all the bytes (since I don't know exactly what they mean).

Could somebody give a good example of a packet with these details and please describe each field?

A good tutorial/explanation will also do the job.

I just started studying this for 2 days, so please excuse me if I sound like a complete noob.

Thanks in advance!


texts: Can I use cumulative winding in common mode chokes?

texts:
I have been designing a common mode choke for common mode noise filtering at the input of my SMPS. I have chosen the capacitance value to be 6.6nF on both Line to Ground and Neutral to Ground.
I am following this equation to set the cut-off frequency of the filter:

Fc = 1 / (2pi * sqrt(L*2C)) = 39.025KHz

Using a T28 toroid core, I get an inductance of 1.26mH at 1KHz when I use an insulated wire  with 18 turns per winding, with the windings placed seperately on both sides of the core (sectional winding). The choke is not placed on the PCB, but placed inside the case connecting power input connector to the SMPS board.

I am trying to get a much higher inductance from the choke by winding it such as the windings are cumulatively coupled (so that effective L = L1 + L2 + 2M). When I tried it out, as expected, I could get an inductane of (1.26mH + 1.26mH + (2 * 1.26mH) = 5.04mH) of inductance. I hope this would give me a much better filter performance from the same core as now the cut-off frequency comes down to 19.435KHz.

But, now since the winding is bifiliar, I wonder if there would be more parasitic C or L effects that would create problems. I know that leakage inductance would be lesser in bifiliar winding, but since I have a separate differential filtering stage onboard,that shouldnt be a problem.

Can some one share your experiences? I always see only sectional wound common mode chokes online and makes me surprised!


texts: The proof of \$PF_{p}=cos\theta_p=sin\theta_s\$

texts:
There is a  Series RC circuit ,which power factor is \$\frac{\sqrt{3}}{2}\$,now if i modify this  "Series"  RC circuit to "parallel" RC circuit,then what is the value of power factor of this circuit?

The answer shows me that

\$PF_{p}=cos\theta_p=sin\theta_s=\frac{1}{2}=0.5\$.does anyone know its proof?Why can this ,\$cos\theta_p=sin\theta_s\$,theorem hold?

\$PF_{p}\$:power factor of parallel RC circuit

\$\theta_p\$ : \$\theta\$ of parallel RC circuit, \$\theta=\theta_v-\theta_i\$

\$\theta_s\$ : \$\theta\$ of Series RC circuit, \$\theta=\theta_v-\theta_i\$


texts: Combining 1, 2 or 3 audio signals so the output always has the same amplitude. LM3900

texts:
So I am outputting up to 3, 0-5V signals from three separate DACs. The issue I have come into is that I would like to combine all three signals to form a single output of the same amplitude. Currently the only way I have been able to achieve combining them is with a Summing amp with 1/3 gain on each input so that when they are combined the output is the same amplitude again. As you would expect though, when only one source is provided the output is 1/3 of the needed output amplitude. (inverted)

I then also looked at the LM3900 multi-channel audio mixer IC (http://www.circuitstoday.com/multi-channel-audio-mixer-using-lm3900)
But I am not sure if this accounts for the issue I am trying to fix. Does anyone know if the LM3900 outputs a constant signal amplitude irregardless of the input signal strength?


texts: Should a grounded case have voltage across it?

texts:
Ok so simple question though it might seem stupid. I'm wiring up a simple metal enclosure with a control unit inside. AC current from the wall, 240v~ to the unit.
I'm containing it in a metal case specifically so I can ground it (and the frame it is connected to).

With everything wired up, (and not grounded) its all good. voltage across the box are where they should be, not shorts. if I place my multimeter on any point of the case no voltage, as you would expect.

However when I plug the ground wire from the mains onto the box in order to ground. The box reads a voltage of 240v~. (when I put the probes from the multimeter on the box it reads voltage where there wasn't before.)
TO CARIFY. If I put the probe on the metal casing anywhere on it, back front inside outside both probes on the grounded box. Not the components I read a voltage. This occurs when the ground is attached.

Am I having a brain fart here or should the box have no voltage so long as there are no shorts?

{EDIT}
Thank you for the information, I will try a different outlet. and probing the case with a resistor when I get a chance. will update when I do.

[Final Edit]
So after testing it seems to have been stray currents. By shifting to a different power point and checking with a resistor it shows no voltage. I also double checked with a pen to be safe, all seems good.
Also tested all the circuit breakers and safety circuits in the house because the electrician who did it was a bit of a bodge, job safer to double check.


texts:
Like resistance for DC, Impedance is for AC. But what is load resistance. How does it used in a circuit.

Had this doubt when reading a line from the book foundations of electronics by D Chattopadhyay

  "A voltage amplifier is one that is designed to amplify voltage
  waveforms in applications where almost no power is drawn by the load
  impedance"


texts: ADC output of 2 sine wave with equal amplitudes and different phases

texts:
In using ADC how to discriminate between 2 sine wave with equal amplitudes and different polarity ( I mean 0 and 180 phases) ?

There is a sine wave that it's apmlitude is changed over the time and i want to track it for further processing ( it is not the case) . Unfortunately for every amplitude there are 2 phase ; 0 and 180 which it means for example there are Asin(wt) and -Asin(wt) and I want to detect this to different cases.


texts:
So,
I need to measure the concentration of Benzene in air. I have an Arduino Zero to read analog or digital value.

I found out the sensor MQ-135. The problem is that, if I'm right, the sensor reacts also to different gasses as NH3 and alcohol.

Is the sensor reliable for such a measure or do I need to look somewhere else? Adapting sensors to the Arduino analog input is not a problem nor power supply of the sensor. My project measure temperature and humidity so, I can also adapt the measure to these two factors.


texts: Is my cache hit rate calculation correct?

texts:
I study cache memories. I'm supposed to calculate the data hit rate for a function call with a 1024 byte direct mapped data cache and block size 16 byte.

sum(0x55aa1000,10);

The function is in MIPS 32 assembly

sum:
    xor $v0, $v0, $v0

loop:
    lb $t0, 0($a0)
    add $v0, $v0, $t0
    addi $a0, $a0, 1
    addi $a1, $a1, -1
    bne $a1, $zero, loop
    jr $ra

My attempt at solution:

The set field is 7 bits because 1024/16=128=2^7 and the byte offset field is 4 bits because the block size is 16. Therefore the tag field is 32-7-4=21 bits. The tags are the same for all data accesses(?)

Since the loop increments data offset by 1 byte and decrements the counter by 1, it will be run 10 times, the first time will be a miss and the rest will be a hit because it is within the same block.

Therefore the hit rate will be 90 %.

Is my solution correct?


texts: How to set NACK on bad PEC in TWI used for SMBUS (ATMega8)

texts:
I want to implement the SMBUS protocol in my AVR device (ATMega1284P), which will have the role of slave. I need to support the PEC (Packet Error Code) feature, which means that the master device (which is not mine) will send a "checksum" byte after the last byte of its command, to which I need to respond with ACK or NACK depending on its validity.

I have some experience with I²C/SMBUS/TWI as I used it before, but it seems I can't solve this particular problem. Apparently, with AVR's TWI implementation I need to decide for ACK or NACK in the byte received prior to the PEC value; i.e., in response to a previous TWSR = 0x80 (data has been received). The problem is, I don't know in advance if the PEC I will be receiving next will be valid or not! Apparently setting or clearing the TWEA bit is only effective for the next byte to be received. Example:

1 - ME     = Prepare for TWI slave operation; set address and ACK
2 - MASTER = Writes SLA+W (gets ACK from step #1)
3 - ME     = INT with TWSR 0x60; Sets ACK/NACK for next byte (ACK)
4 - MASTER = Sends Byte (gets ACK/NACK from step #3)
5 - ME     = INT with TWSR 0x80; Sets ACK/NACK for next byte (ACK)
6 - MASTER = Sends Byte (gets ACK/NACK from step #5)
7 - ME     = INT with TWSR 0x80; Sets ACK/NACK for next byte (ACK)
8 - MASTER = Sends PEC Byte (gets ACK/NACK from step #7)
9 - ME     = INT with TWSR 0x80 (PEC); too late to ACK/NACK PEC value!

As you can see, I should decide for ACK/NACK in step #9, but the master's already got an ACK set at step #7!

As much as I digged into the docs, I cannot find a way to respond with NACK "on the fly" because the ATMega sets the interrupt AFTER sending the ACK (or NACK). TWSR will be either 0x80 or 0x88, which means "byte received, ACK sent" and "byte received, NACK sent" respectively.

Aside from implementing a bit-banging SMBUS library, is there some way to solve this?

Thank you.


texts: I need to measure small changes in the force applied by two fingers holding a force sensor. The changes are in the order of the micro-Newton. The commercial system for making these types of measurements cost several thousands of dollars. Do you know if there are cheaper alternatives that can be used?


texts: Measuring Quality Factor of an Ideal Inductor

texts:
For my lab work, I have to design a method to measure the quality factor of an ideal inductor between 1MHz to 5MHz, away from resonance frequency. We know that an ideal inductor has the form (with a series resistor):

simulate this circuit – Schematic created using CircuitLab

The quality factor is defined as Q = wL/R, but the challenging part is we cannot take measurements between L1 and R1, since it isn't existed in real, I can measure only from node A and node B? I am allowed to use standard values of capacitors and resistors with a digital oscilloscope. Any ideas?


texts: What is the common name for this seal-in relay?

texts:
I'm trying to build a hysteresis water pump system with 2 water level switches. Please see the diagram and explanation of this setup I've taken off the web:

The first switch (L) is set at the minimum liquid level desired in the tank. The second switch (H) goes at the maximum desired level. When the liquid is below both switches, they are both closed; the pump runs, filling the tank.  As the liquid fills past the first switch, it opens. However, seal-in relay A has been activated and closed, bypassing the now-open switch L (effectively “sealing it in”), so the pump continues to run until the high-level switch H opens. When the high-level switch opens, the motor relay P opens, stopping the motor, and seal-in relay A opens.

My question is, what is a seal-in relay in the consumer market?

I can buy water level switches on ebay for like 5 bucks, but I am finding it hard to find what a seal-in Relay switch is that is needed for this schematic. And i'm looking at something very basic and cheap to be just enough to do the task. My problem is I can't buy this item because searching for seal-in relay gets me no where.

Thanks!


texts:
I am studying the 8284 clock generator and see how it works with the 8086.

But before I connect the two chips together, I want to verify the 8284 first.

So I placed the 8284 on the breadboard as follows:

Here are my questions, any help is appreciated:

I want to verify if the chip is working.  If I measure the output of CLK pin using multimeter, it always give me 2.1v.  (I know I need an oscilloscope, but I don't have one.  The only thing I tried is using arduinoscope, but it shows a constant 2.1v too).  Is it true buying a oscilloscope is the only way to "see it is working"?
I also tried to measure other pins, but they are all showing 2.1v or around 1v.  Which makes me wondering if my connections are actually wrong, is there any problem in my diagram above?


texts: How can I get/calculate simulink bldc parameters

texts:
I tried to get the parameters for a bldc simulation https://de.mathworks.com/help/physmod/sps/ref/brushlessdcmotor.html

I tried to find a similar motor to the I need (500 W, 20-25 Nm, geared bldc)
However I can't get either flux linkage or the rotor-induced back emf, the options there.

Could you help me how can I get the data needed from a table like this?
https://www.semanticscholar.org/paper/Mathematical-Modeling-of-Permanent-Magnet-Brushless-Shetty-Subramonium/7bd32a8ef2049ede79ef2eb6af7609d4ca5701dd/figure/0
table1

Any help or literature is appreciated.


texts:
I want to add a factory reset onto a PCB design I am working on. Basically, I want it to be a switch (or combination of) that will never be "accidentally" closed and therefore accidentally factory reset the uC.

My initial thought was to add a switch you can only press with a needle that you see often in consumer products, except this PCB will not be inside an enclosure and I believe the "needle" requirement comes from designing the enclosure to have a small opening that only a needle can penetrate.

My next idea is to use an 8PDT switch (or similar) where only 1 combination of the 8 switches (1 / 2*8 = 1/256 = 0.4%) will output a "1" to the factory reset.

Anyone have any experience with this, or suggestions for alternate methods?

Thanks.


texts:
I am struggling in trying to put a UART Port working (no flow control and no parity bit) in a PIC32MX in order to comunicate with a Fingerprint for too long, so I decided to get back to you guys. I just can put the fingerprint reader in digital I/O's because I have no more UART PORTs available. There's no problem for the TX pin but when it comes to enable RX pin (CN interrupt) I am seeing a problem.

This is the Fingerprint Reader I am using an this is the datasheet for the PIC.

I am using the CN4/RB2 Port for the Interrupt (Rx) and the RB0 to transmit.
The compiler is XC32.

#include "NVMem.h"
#define Baudrate        4800   //bps
#define OneBitDelay     (1000000/Baudrate)  // microseconds
#define DataBitCount          8             // no parity, no flow control
#define UART_RX               TRISBbits.TRISB2  // UART RX pin
#define UART_TX               LATBbits.LATB0    // UART TX pin
#define UART_RX_DIR           TRISBbits.TRISB2 // UART RX pin direction
#define UART_TX_DIR           TRISBbits.TRISB0 // UART TX pin direction

int volatile readB = 0;
unsigned char UART_Receive(void);
void UART_Transmit(const char);

void __ISR(_CHANGE_NOTICE_VECTOR, ipl5) ChangeNoticeHandler(void)
{
readB = PORTB;      // Read PORTB to clear CN4 mismatch condition
if (readB){
    UART_Transmit(UART_Receive());
}

LATDINV = 0x0F;     // PORTG = 0xff;    // Toggle outputs.
IFS1CLR = 0x0001;   // Be sure to clear the CN interrupt status
}

unsigned char UART_Receive(void)
{
unsigned char DataValue = 0;
    unsigned char i = 0;

while(UART_RX==1);
delay_us(OneBitDelay);
delay_us(OneBitDelay/2);
for (  i = 0; i < DataBitCount; i++ )
{
    if ( UART_RX == 1 )   //if received bit is high
    {
        DataValue += (1<<i);
    }
    delay_us(OneBitDelay);
}
if ( UART_RX == 1 )       //Stop bit should be high
{

        return DataValue;
}
else                      //some error occurred !
{
        delay_us(OneBitDelay);
        return 0x000;
}
}

void UART_Transmit(const char DataValue)
{
/* Basic Logic
   TX pin is usually high. A high to low bit is the starting bit and
   a low to high bit is the ending bit. No parity bit. No flow control.
   BitCount is the number of bits to transmit. Data is transmitted LSB     first.
*/
// Send Start Bit
UART_TX = 0;
delay_us(OneBitDelay);
unsigned char i;

for ( i = 0; i < DataBitCount; i++ )
{
    //Set Data pin according to the DataValue
    if( ((DataValue>>i)&0x1) == 0x1 )   //if Bit is high
    {
        UART_TX = 1;
    }
    else      //if Bit is low
    {
        UART_TX = 0;
    }
    delay_us(OneBitDelay);
}

//Send Stop Bit
UART_TX = 1;
}

void FingerprintRun(Task * task){
 CNCON = 0x8000;                 // Enable CN module

 CNEN = 0x00000010; // Enable individual CN pin CN4
 CNPUE = 0x00000010; // Enable weak pull up for pin CN4

 UART_TX = 1;           // TX pin is high in idle state
 UART_RX_DIR = 1;       // Input
 UART_TX_DIR = 0;       // Output

 readB = PORTB;

 IPC6SET = 0x00140000; // Set priority level=5
 IPC6SET = 0x00030000; // Set Subpriority level=3

 IEC1SET = 0x0001; // Enable Change Notice interrupts

UART_Transmit ('H');
UART_Transmit ('i');
UART_Transmit ('\r');

while(UART_RX==0){
    asm("nop");
}

while(1)
    {
    }
}

While debugging the Program Counter never goes to the interrupt.


texts:
I am working on a prop for a film -- I have to make a sign spin in a circle (simple attachment to a motor) and have variable speed.

I know enough to wire the thing, but am having a hard time getting and answer on what size motor to use. The sign will be 20x30 in and made of coroplastic--so light weigh. I can not puncture the sign to attach it to the shaft of the motor, so will have to rig an attaching mechanism. Seems to me the load should be no more than 2 lbs.

Any recommendations for size of motor or which equation I should use to suss it out would be a great help. Thing is due on Friday...


texts: Understanding a simple circuit containing multiple op-amps

texts:
I'm trying to learn electronics on my own. I got this circuit from an old audio amplifier device I had lying around. I'm trying to understand how it works. I have some questions about it. Could you help me?

This point has a DC Voltage of +6V, and it oscillates in the range of a few mV in response to Audio In. Then the DC offset gets removed by the directly next capacitor. Is all of this correct? What's the point of all of it?
If I short this capacitor, the amplifier stops working. Why? Current through Audio In is still flowing, right? Is the capacitor there to remove some DC offset?
I don't think I understand what exactly the op-amps are doing and how they do it. I assume the transistors simply take the heavy work of providing the current needed to drive the Speaker once the input signal is completely amplified.

Edit:
I have redrawn the schematic. Also, I think I found the explanations by experimenting in Falstad Simulator:

The DC Offset at the output of OA1 is slightly above +6V because of R2; C3 removes that offset. The output of OA1 oscillates by more than a few mV. The job of OA1 is to increase back the voltage of the input, since the input got lowered its voltage by the load it is put through.
Through AudioIn is the path of least resistance to ground for the output of OA1 to go through, so C1 is there to remove that DC offset.
Explained in the comments: "OA2 and OA3 are driving the two outputs to be opposite from each other, plus they reduce the effect of the class B outputs."

simulate this circuit – Schematic created using CircuitLab


texts:
Based on CST website, they claim that CST PCB Studio can import Altium files.

But when I open Import on CST , it gives me just these options :

I tried to Export Altium to HyperLynx and Import it to CST PCB Studio,but it gave error too.
I also tried converting to AutoCAD and use ODB++ , but still gives error for importing.

I'm using CST Suite Studio,Release version 2014.00 - Feb 24 2014

Do you have any solution ?

Thanks.


texts: Non-pushbutton supervisory IC with interrupt and enable outputs, kill input and adjustable power down timer

texts:
I'm looking to build a supervisory circuit which monitors a single voltage rail. When the monitored rail goes from HIGH to LOW, the supervisory IC asserts an interrupt signal to the system MCU to allow it to power down. The MCU can then assert a kill command to the supervisory IC, which turns off the enable output.

Unfortunately the only suitable ICs I have come across thus far have been for pushbutton input, which isn't suitable for my use case, as the monitored input is a static voltage rather than a momentary pulse. The following schematic for the LTC2954 offers the exact functionality I'm after, if the pushbutton input (PB) were replaced with a static voltage monitor input. Note the adjustable power down timer (PDT) which can be used as a back up in case the MCU never asserts the kill command.

Can anyone recommend a suitable IC or family of ICs? There's any number of similar pushbutton ICs, as well as a range of watchdog timer and reset-based voltage monitoring ICs, but I'm struggling to find an IC which provides the described functionality for non-pushbutton input.

EDIT: How about using a schmitt trigger XOR circuit to simulate a pushbutton press when the state of the monitored rail changes (taken from this post):

If my understanding is correct, I could then utilise a standard pushbutton controller IC with a non-pushbutton input?


texts:
Could someone tell me where this diode (highlighted part) would be added and the orientation?

https://www.maximintegrated.com/en/app-notes/index.mvp/id/287


texts: Possible error in schematic; unrealistic capacitor

texts:
I am trying to get the parts for this electromagnetic coilgun, and I have gotten almost all of the parts. I cannot seem to find the 1,000 uF 1.5KV capacitors (C3 and C4) for the voltage ladder, and from my experience with electronics (and a little research) this is a ridiculous value. From the picture in the above link, it  looks like a ceramic cap, but I don't know what it is. Is it a typo? If so, what do you think the right value is?

Schematic:


texts: Block current flow out of powered USB hub when supply is off

texts:
I have a custom computer setup with a standard 5V SMPS module powering many attached devices: an Ethernet hub, USB hubs, Raspberry Pis. (To eliminate the need for 6+ wall-warts) I have a basic eBay volt+current-meter module on the output of the SMPS, to see how much load I'm pulling, and ensure the voltage is good.
I've noticed a weird behaviour when the SMPS is off: the volt-meter reads 3.8v. I've traced this to the USB hub: it has a 5v barrel connector input, but if it's connected to a PC which is on, it's sending power out of the barrel-jack 'input'. (And presumably slightly loading the USB bus)
This doesn't really matter, but I wondered what kind of circuit might prevent this behaviour, i.e making the power input truly input only. I'd prefer not to modify the USB-hub; I'm hoping for something I could install between the SMPS and the barrel-jack plug.


texts:
I was reading some code to use an on an arduino ATMEGA328P and I can't figure out what this line of code does.

ASSR &= ~(_BV(EXCLK) | _BV(AS2));

I know that ASSR is the Asynchronous status register and that EXCLK are AS2 are bits in that register.  I'm pretty sure that _BV() is used to set that bit, correct me if I'm wrong.  What I don't know is what this code actually does?  It seems like that this code uses bitwise operations to compare the register ASSR to a single bit (~(_BV(EXCLK) | _BV(AS2))) and then sets that register to a single bit, one or zero.  This doesn't make any sense to me since this register is 7 bits large and can't be compared to a single bit.  Any help is appreciated, thanks.

Relevant documentation:

ATMEGA 328P datasheet

AVR Libc page


texts: Best soldering practice for through hole only manufacturing

texts: I have a power adapter PCB with through hole parts (only).  The board itself has two external copper planes (3 oz) routed to the through hole parts without thermal reliefing (this is for a reason).  At the assembly level, it is nearly impossible to fill the barrels of these through hole parts.  I have a soldering iron and a IR reflow oven.  Is there an efficient means of assembly using these two tools, to ensure 100% barrel fill.  If not, are there any practical solutions for completing such a task?


texts:
Could someone help me with something like this? I wanted to add DS18N20 thermal sensor (http://datasheets.maximintegrated.com/en/ds/DS18B20.pdf) via 1-wire interface and when I'm trying to connect it to ATZB-24-A2 (http://www.farnell.com/datasheets/1738045.pdf), which is using ATMEGA 1281 processor, this way
(source: tushev.org)
or this way

I'm receiving random bytes on COM terminal (I'm using FTDI chip). What could happen and how to fix it?
EDIT: I'm not even configuring anything in my software, it just starting mess without my interfere.


texts:
An ADC (ADS1015 with n=12 bit resolution) is connected to 5V DC power supply. So its V_ref=5V.
However, if I set gain=16, then full-scale-range = +/-0.256V i.e peak to peak voltage= V_pp=2*0.256=0.512V  (as given in data sheet Pg 10, Table 3: Reference https://cdn-shop.adafruit.com/datasheets/ads1015.pdf )
In such a scenario, which formula out of the two mentioned below should be used to convert raw data from ADC into equivalent voltage:
(1)       V_in = (Raw data from ADC) * (V_ref/2^n)  = (Raw data from ADC) * (5/4096)
(2)       V_in = (Raw data from ADC) * (V_pp/2^n)   = (Raw data from ADC) * (0.512/4096)
Also, in the above two formula, where do we substitute "gain=16" factor?
If somebody could please explain this I would be very much appreciative.


texts: What did the manufacturer mean by asking if an angle should be made for the fingers?

texts:
I sent in Gerber files designed by someone else to PCBWay. It's a cartridge for a Commodore 64.

They responded today with this question, and I'm not 100% sure what they are asking.

  Ref attached screenshot, please advise if we should do 30° degree for finger places.
  If yes, we will chop copper to reach 1mm distance from copper pad to outline.

When I loaded the design in EAGLE it did say that the card edge connector pads were too close together. Do they mean 1 mm distance between the 'fingers' or 1 mm distance between the 'fingers' and the board edge?

I know it's a 50/50 chance whether I say yes/no, but I'd like to be correct. It's weird, because the person who designed this said he had no issues getting it made.


texts: Does LRCK have to oscillate in an I2S system?

texts: I'm working on a audio function generator using the PCM 1795 DAC. I only need a single output channel for my design. Can I just pull LRCK low or high permanently for the sake of maintaining design simplicity? Much thanks.


texts:
I am working on a 2 layer Teensy 2.0 clone.

What is a recommended way of connecting GNDs on the top layer to the GND layer (bottom layer)? Should I use through-hole for every GND pads or can I do a GND pour on the top layer (and as well as on the bottom layer)?


texts:
I've selected 230/400V motors (delta/star) and corresponding 400V VFDs for pump motors. Now I've been asked why I haven't selected 400/690V motors (delta/star), that are the standard and usually connected in delta. The manufacturer says there that the both motors types will consume (approx.) 8A at 400V and there is no special requirement for the torque.
Is anyone seing an advantage to have the 400/690V motors instead of the other ones?


texts:
I have a Gateway HP-AN235D43 power supply that is 12 V and supposed to output up to 19.6 A. I want to use it to power two 55 W car headlight bulbs, adding up to about 10 A. However, it works only with one bulb, drawing about 4.6 A. When I put two bulbs in parallel, the PSU would not turn on, measuring 0 V on its output.

Is this another symptom of the failing capacitors? I would like to have some idea before opening it up.


texts:
I am trying to simulate the following circuit in PSpice, but I face the this warning in base of the transistor. changing the transistor didn't solve this issue. Please help me fixing it!

WARNING:  [NET0093]
No PSpiceTemplate for Q3, ignoring

ERROR -- Less than 2 connections at node N00711
ERROR -- Node N00740 is floating
ERROR -- Node N00711 is floating
ERROR -- Node GND is floating


texts: Spikes in Inductor Current : Buck Converter

texts:
What could be the reason of such spikes in inductor current at each Switch ON-OFF. ??

This spikes are also getting affected in load current.

Please help me to reduce / remove this spikes.

( waveform of inductor current with spike are shown in image file )


texts: Can I use an RIBU1C to switch a 110v fan?

texts:
I recently set up a millivolt switched gas heater with an Ecobee3 thermostat. I used an RIBU1C relay to accomplish this (Ecobee wants to switch a 24VAC circuit, and the gas heater wants a millivolt circuit switch). That all works great. (I followed this guide.)
Now I have the bright idea of turning on a 110v fan every time the heater turns on, to better distribute heat from the heater. I'm looking at the 110V leads on the RIBU1C and it seems like I could just wire that up like a 110V light switch inline to the hot wire on the fan?

I would appreciate advice on whether I am misunderstanding how the 110V lines on the RIBU1C work (maybe they are for 110V signal input and not designed to switch on/off 110V lines?)
I have decent/safe household 110V electrical knowledge (I can safely install light switches, direct wired overhead fans, etc), and a smattering of electronics knowledge. So I'm comfortable making the 110V wiring from the wall to the fan safe. I just want some external input to make sure I don't let the magic smoke out of my relay, or the Ecobee, or otherwise do something dumb.


texts: Is there an open source USB to JTAG circuit I can include in my PCB design?

texts:
Im trying to find out if it would be possible to build/include a USB to JTAG circuit on my experiment circuit board I'm designing. My aim is not to reinvent the wheel, but use something that is already out there, and simple/small enough to add to my PCB design.

I want to be able to program and debug my Atmel SAM3S chip using JTAG, via USB.

I've seen devices like the USB to JTAG programmer from Modular Circuits, and it looks like this can be fairly easily integrated into my design, however, I'm not too sure if their license allows this.

I've tried to Google around a bit for alternative more open sourced designs, but couldn't really find something. Can anyone refer me to a Open Source project for USB > JTAG circuits, that are available online?


texts: How many inputs can a single mcu output drive?

texts:
I am planning a project that will have many ATTiny chips connected together. The idea is that a master node will send various control signals that every slave node will listen to. My system could potentially grow to several hundred nodes.

I am a little worried that if I add too many slave nodes listening to the same output pin, that the current requirements will start causing problems with the master node not being able to drive enough current.

How many chips can be connected to the same output pin before I have problems? What specs should I look for to help me know the limits?

I will specifically be using ATTiny2313 at 5v.


texts: How is oscillation condition fulfilled in this oscillator circuit?

texts:
I'm rather curious as to how oscillating conditions are achieved in this oscillator. My attempt at an analysis follows.

The BJT is operating in common base mode. As the base resistors are equal, the base is biased to half of supply voltage - \$3V\$. Let's say \$\beta=100\$: then current into the base is \$I_{b}=\frac{3V-0.7V}{\beta * 2.2k\Omega} \approx 10\mu A\$ and \$I_{C} = 100 * I_{b} = 1mA\$. At room temperature \$V_{T} = 25mV\$, so \$r_{e} = \frac{25mV}{1mA} = 25\Omega\$. This is negligible compared to \$R_1\$, so we can say that \$V_{EQ} \approx 2.2V\$.

The capacitors \$C_1\$ and \$C_2\$ are in series and their equivalent capacitance is \$50pF\$. The resonant frequency \$f=\frac{1}{2\pi \sqrt{L_1C}} \approx 58MHz\$. At this frequency the impedance of the inductor is \$Z_{L_1} \approx 55\Omega\$. The open gain of common base amp is \$A=\frac{Z_{L_1}}{r_e} \approx 2.2\$.

The input impedance of the amp is just \$r_e\$. At \$58MHz\$ a \$100pF\$ cap has an impedance of about \$27\Omega\$. Therefore there is \$27\Omega\$ between the output and input of the amp (\$C_1\$). The input impedance of the amp in parallel with \$C_2\$ to ground gives \$r_e||27\Omega \approx 13\Omega\$. So if we image a voltage divider from the BJT collector (amp output) to BJT emitter (amp input) to ground, we get circuit attenuation of \$\frac{13\Omega}{13\Omega+27\Omega} = 0.325\$. This attenuated voltage is amplified by \$2.2\$ to get \$2.2*0.325 = 0.715.\$

But to oscillate, the loop gain should be slightly over one. So by my analysis, the circuit should not oscillate. However, I have built this and it does oscillate. So what is the flaw in my analysis?


texts: How to optimise something when multiple parameters change the output

texts:
This dilemma seems to occurs all the time in so many different engineering problems. It seems impossible to optimise something with multiple parameters, for three reasons:

There are too many possible combinations of these parameters to be able to simulate them all
You optimise one parameter at a time, but then you don't know if your final result is the best possible result. E.g: You start with a neural network with 5 layers, and 4 neurons in each layer. You perform a sweep on the number of layers in the neural network, plotting the accuracy of the network vs number of layers. You find that the optimum number is 3 Layers. You then optimise the number of neurons in the first layer, and find that the optimum is 10 neurons, then you optimise the number in the second layer and find 7 is the best, and then the number in the third and find that 6 is the best. However, this might not be the best overall solution: For example the accuracy of the network might be better if you start by using 3 neurons in the first layer, which is not the optimum, and then optimise the number in the second and third layer, finding that you get a different number of neurons but a much better accuracy compared to the first method.
You optimise parameter 1 that governs property X, and then you optimise parameter 2 that governs property Y, but then this has changed property X, so you go back and optimise the parameter 1, but then this changes property Y.

This seems like a very fundamental problem when designing any system in any area of engineering, and I thought that there may be a standard method of approaching this problem, or at least a few known methods that do a pretty good job. If there is a solution to this dilemma, can somebody please tell me?

Additional Details

The neural network example is the problem I am currently having, but I'll give another example of this problem I have had in the past. I was trying to design a patch antenna that will have a resonant frequency of 2GHz. The resonant frequency is mainly dependant on the width of the patch, and the gain of the antenna was mainly dependant on the insertion depth. In CST, I performed a sweep on the width and picked the value that gave the lowest s parameter at 2GHz, I then performed a sweep on the insertion depth and picked the value that reduces the S parameter to the lowest value (I decided that -40dB was acceptable). But this then changed the frequency at which this gain happens, so I did a sweep on the width again, and I picked the value that gave the lowest s parameter, but now the s parameter is too high again, so I optimise the insertion depth... and so on.


texts: Have a 5mm diameter cable entering a small enclosure. What's the best way to seal it? I was thinking neutral cure silicone. Are there better solutions? I know cable glands are a popular way of achieving it, but they're quite bulky and would prefer to try something else even if it requires a bit more labour.


texts: Voltage lower than expected with Nema 17 stepper motor and L298N

texts:
I am using an L298N motor driver with a Nema 17 stepper motor. I am trying to use the motor to turn a valve, but there is not enough torque so the motor is skipping steps.

I am controlling the motor driver with an Arduino and am powering the motor driver with a variable DC power supply.

In attempt to supply more voltage to the motor, I have now removed the 5V_EN jumper and am inputting 5 volts from the Arduino to power to driver circuit.

I have set the variable power supply to 18 volts. Before turning on the motor, the variable power supply is outputting (based on the display) 18 volts and 0.01 amps. When turning on the motor, the power supply is outputting around 6 volts and 2 amps. After turning the motor on once, the power supply continues to output 6 volts and 2 amps even when the motor is off.

How can I increase the voltage to increase the torque of the stepper motor?

If this is not possible, what motor controller drivers (compatible with Arduino) would be appropriate for this task?


texts: How to automatically position designators in Altium?

texts:
Is there any way to automatically place component designators in Altium such they are all visible and doesn't overlap other components?

A clear example is described here but it seems it is a separate piece of software you have to buy. Is there any built-in feature to achieve this?

What I want to achieve is this:


texts: I know you're not supposed to rectify mains because it's "dangerous" but if I use a 1:1 transformer and ground it to earth how exactly am I any "safer"? I ask because it would save me $130 to simply rectify mains and get the same voltage.


texts: I have a plan to make a solar charger for battery and at the same time power a load.I want to use lm317t to keep constant current.I can not find any reference on how a lm317t effects a solar panel charger with a load.the battery I am charging is 2000mah 7.2 volt battery with a 9volt solar panel.I want the panel to charge the battery and send excess current to load.What would schemetic be how would lm317t fit in this situation.


texts:
I am pretty new to electrical engineering, so please bear with me.
I am trying to activate a 5V relay when it detects sound coming through a 3.5mm jack. Can anyone help me figure out how to do this?


texts: How to amplify both phone audio channels in this case (infrared remote)

texts:
I'm a photographer and have limited knowledge about electronics.
recently I saw this circuit:

which is explained here
I tried to Build it, it works fine on my laptop jack, but does not work on my android smartphone jack. I guess it's because of low output signal voltage (less than 0.6V) as explained in this case.
since I only have lm386 IC in my stuff an it's important to keep circuit size as small as possible, I am wondering if there is a way to use just one lm386 IC to amplify both channels without any change in output infrared signals?
please guide me how to design my circuit.(with one or two ICs)
Thanks


texts: ESP32 WROVER IB auto program not working

texts:
first question and first circuit ever, i designed a custom esp32 board and used the esp32 worver for its big capacity and the IB version for it's already soldered ipex connector. so i tried adding an auto program circuit in the v2 pcb but was never able to make it work unfortunately here's the circuit in the photo i understand that it's not very well arragned but the auto program circuit is supposed to be very simple, any help would be appreciated thanks
EDIT 1: added a simplified version with only the auto program circuit and reset/boot buttons, the autoprogram circuit is based off espressif schematics


texts:
I am using a PIC18f25k80 microprocessor and I want to transfer data on an SD card over SPI. The compiler I am using is MPLAB X XC8. Could you please provide an example of how I can initialise the SD card and SPI and how I can create a file where I can store the data. Even a pseudo code would be really appreciated if the task is too complicated!

I have already tried to find examples, but I am really confused on how to put all these together.

Thank you


texts:
I don't understand how amplitude of incident and reflected voltage of wave equation comes out with
\$e^{j2\beta z}\$ next to reflection coefficient. What is the meaning of it? Why is it part of the amplitude? How can I derive it?


texts: visible light communication data reception

texts:
My project is on visible light communication. I use a 555 timer circuit to modulate data with 200 KHz signal using a 3 watt LED.

At the receiver I use a photodiode (PS100-6-CER2PIN First Sensor Photodiode), a trans impedance amplifier (using LM358), a high pass filter (LM 358) with cut off frequency 200 KHz, and a Notch filter(LM 358) of 100Hz.

At the output of trans impedance amplifier, I can recover my transmitted data at a distance of 20 cm (checked using laptop with hyperterminal). But I get noise at the output of filters when data is transmitted. I checked using Oscilloscope, where I get the signal over a distance of 100 cm. Is it possible to recover the data at 100 cm? Why am I not able to recover the signal at a distance of 100 cm, though I can see a clear signal in oscilloscope at 100 cm?

 enter image description here


texts: How do I tell what sort of solder I have?

texts: My soldering iron came as part of a kit and I have really not used it very much at all in all the years I have had it. (Read zero meaningful uses). I cannot remember who gave it to me or why. The kit came with some solder but I have since learned that there are different types including leaded and lead free. Is there a way of figuring out what type I have?


texts: Is it bad to connect multiple electrolytic smoothing capacitors in parallel?

texts:
I'm making a power supply using a transformer and bridge rectifier, and I'm wondering whether it is a bad idea to put multiple (5) capacitors in parallel for smoothing.

The output should be capable of drawing 1.1A at 10.7V. I'm allowing for a ~2V peak to peak ripple, as this is fed into a boost converter.

$$
 C = \frac{I }{2 f V_{p-p}}
$$

$$
  = \frac{1.1 }{100 *2}
$$

$$
  = 5.5mF
$$

Further, what if I was to use different valued capacitors (e.g. a 4.7mF and 1mF)?


texts: L7805CV - Circuit not pulling expected current when powering from Voltage regulator

texts:
I am using a linear regulator to step down the voltage for my microcontroller circuit, however, I noticed that when I power my microcontroller circuit from my laptop (at 5 volts) it pulls around 76 milliamps, but when I try to power the circuit with a 9v battery (or my 12v car battery) and the voltage regulator (L7805CV), then the current being drawn is only around 20 milliamps (instead of the 76mA that I get from my computer when powering without the regulator).

The voltage regulator output is 5volts as I would expect, but the current is being limited or something when the max should be 1.5Amps. I thought that maybe I burned out the regulator accidentally or something, so I swapped it for another one but am getting the same results.

(TOP VIEW)
--------|====== Output (5v)
|       |====== Ground
--------|====== Input (9v)

When I'm powering from the regulator I am getting 5 volts, but the circuit is only able to draw .20mA and the circuit is not working properly. When I am powering from the USB power supply, I am also getting 5volts but at 76mA, and the circuit works as designed.

EDIT
I am not using the .33 uf or .1uf capacitors. When I get a min, I will try adding those, but I have a hard time figuring out how that would limit my current to .02amps when the max should be 1.5 amps.


texts: Inexpensive solid-state variable resistor

texts:
I have an analog audio project I'm playing around with designs for and it will need about 150 solid-state variable resistors. I plan to control these from a micro controller so a digitally controlled pot would work but all the ones I've found are way too expensive ($1.00-$1.50).

My original plan was to use something like a MOSFET with a small capacitor and another transistor to hold a voltage on the gate. I would then update the voltages of each in turn via a DAC and some GPIO. However I haven't found any transistors suitable for my application (i.e. something that behaves enough like an ideal resistor).

Any ideas?

FWIW: the project is a variant on this (discontinued) EQ design: Designing with the LMC835 Digital-Controlled Graphic Equalizer.


texts: ARM Debugging - Cortex M0 debugger gpio changing while halted in SysTick_Handler

texts:
I've been trying to figure out this one for hours and I can't see what I'm missing. I currently am debugging my program on hardware and I have set a break-point inside of one of the functions called by SysTick_Handler(). Despite having the CPU halted, my LEDs, which are controlled by the CPU on the low side, are "blipping" about every second. I tried setting a break-point in the function that controls these and nothing happens which I would expect since my only core is halted.

Shouldn't my device be stable when halted since the gpio registers are not being modified by my code? Does the timer interrupt continue to fire even though I'm at a breakpoint or something?

HARDWARE DETAILS:

MICRO: XMC1302-T016X0032 AB

TYPE: ARM Cortex M0


texts: What does inverted triangle in this schematic mean?

texts:
I'm trying to make this circuit but I'm unable to understand what the inverted triangle is and how to connect them all together.
Here is the schematic, what does the inverted triangle represent?

And how can I build this circuit, can I use wires to solder to the capacitors, diodes and resistors? Will it reduce it's effectiveness?
I have Capacitors with 102pF, 103pF and 104pF, among the ones I have, which are suitable for this circuit?
I was asked to connect a thin copper wire of 12 inches as antenna, I'm planning on soldering one such wire to one 103pF capacitor and other end of this capacitor to 1n34a diode(D1) and other end of the D1 to another capacitor(C2), and another end of 103pF capacitor to 1n34a diode(D2) and this one's end to D1, below the C2, between both wires of C2, I'll solder 10k resistor, and to these ends I'll solder wires which I can insert in multimeter.
Am I doing this right? Will adding wires reduce it's effectiveness?


texts: How is correct to interface an MCU (Arduino)'s UART with this RS232 TTL device?

texts:
I am trying to interface a bill acceptor which provides RS232 (TTL level) with the Arduino's UART.

The manual of the bill acceptor provides the I/O circuit below.

I have tried two ways to no avail.

In the first way, I make the connection with the 2 x 1K resistor and 2n2222 transistor with a breadboard like this:

The RS232 interface of the device has 4 wires: TX, RX, Download VCC (which I connect to Arduino's 5V - I also tried not connecting it, still a bit confused about this wire) and GND (which I connect to common GND with Arduino).

I also tried the following to no avail:

Upon starting up, even from the beginning when not connected with the Arduino, the device flashes in a way that it means its RS232 is not working (by checking with the trouble shooting part of the manual)

Connecting like above also gives the same result.

It's a bit weird to me that the guy who sold me this acceptor, after asking me to try so many ways (checking wires, re-check DIP switches etc.) finally told me that the RS232 interface of the acceptor has to be connected in order for it to work, which is kind of weird to me. I made the above attempts following his claim.

Could anyone tell me where I went wrong? Or is it a defective unit?

Many thanks!
Dave


texts: Mosfet as switch for high output current

texts:
I'm working on an android controlled input/output/gauges manager for cars based on a pic24 micro controller. I'm really not an electronics expert so I had someone working on the schematics but he has no time anymore. It's mostly done and functional but I'm having trouble with the output schematics.

The idea is to be able to drive various loads (leds, solenoids, dc motors, etc) and turn them on/off from the pic micro controller.

Pin43 on the schematic is a pic pin that is 0v-3.3v, Vin is 12V and Pos_Out1 is connected to a load that is grounded.

The issue I'm having is that testing it with a light for example, there is always current even when the pic pin is floating or grounded. When I send 3.3v on the pic pin, the light gets brighter so more current flows but there should be no current flowing when the pin is grounded or floating.

Is something wrong in the schematic?

Thank you for your time!


texts: Is there a way to terminate a two conductor cable to a BNC plug?

texts: I have a device with a two conductor cable that I need to interface to a signal conditioner with a BNC input (same as that on a standard oscilloscope). I would rather not use a hacky solution like a screw terminal to BNC adapter and directly terminate the cable with a male BNC plug.


texts:
Suppose I have a device that utilizes a supercapacitor.

How long will it take to wear out the supercapacitor so that it needs replacement?


texts: Wiring two separate circuits with separate loads (one with mosfet and Arduino) with a single bench PSU

texts:
I have a cheapo bench PSU with one pair of terminals on it and I am trying to wire the pictured circuit correctly and in best possible practice. As my description on the schematic says, one LED device will be under the control of Arduino/mosfet/buttons combo, while the other LED device will be wired in a plain manner, straight to the power source, with a basic toggle switch to turn it on/off.
I tried to wire it as best as I know, since this is workbench environment I don't have anything but crocodile clips, but there was a mistake on my part because the "Arduino controlled" LED didn't shut off completely when Arduino said it should, it would turn off to 50% brightness, and the MOSFET got superhot. Also, I do have to say it, in my Arduino code every pin is used with "INPUT_PULLUP" rule applied.
So, before I smoke something here I'm asking for some help, maybe some of you can scribble the proper wiring approach on this diagram. My understanding on how to properly ground things in this scenario is not the best. Thanks for help!


texts:
I am an artist looking to experiment with generating schematics with various machine learning techniques and am looking for a large (ideally 10,000+) publicly available dataset of schematic files. The techniques that I am looking to employ requires that these files be .sch (or similar file format that can be opened with KiCad or EAGLE. Are there more common or interoperable schematic file formats that I should be looking for?) and not simply images of schematics.

A bit of Googling around led to rather unsatisfactory results and I am not actually much of a hardware guy myself (I've got a basic understanding of circuitry but thats about it). The exact purpose/content of dataset is relatively unimportant provided there are enough files in a format that I can use. For instance, if NASA were to have a database of schematics from certain missions that would suffice.

Thanks in advance!


texts: Macrocell and Function Block optimization ISE XILINX

texts:
I get the following result when I compile my code in ISE. It says the CPLD is full, but I can't help but notice that the optimizer should be able to move elements from different function blocks to optimize having full macrocell and function block inputs.

How do I maximize the optimization to allow this to fit? (The following picture is what it looks like when it's compiled for the next size up


texts: RF Narrow bandpass filter (crystal ladder)

texts:
I am currently designing a narrow band pass filter at around 8Mhz, using the crystals having a  resonance frequency of 8Mhz.

Using the tutorial from :http://www.giangrandi.ch/electronics/crystalfilters/xtalladder.html
we manage to get a crystal ladder filter having a passband at around 8Mhz, bandwidth of 400Hz.

However, at high frequency (anything above 70Mhz), the filter response rise up and anything above 70Mhz can pass through.  (see the picture)

We do see the response of the filter looks something like the picture below around 6~10Mhz.
However, after the 70Mhz, the entire response is different. Is this normal?

How can we make a filter that ONLY pass through 8Mhz and not above 70Mhz?


texts: What will be the output voltage graph of the following circuit if output voltage is considered across the resister?

texts:
The circuit is given below.
I know that until the Vin reaches the first peak, the voltage across R (output voltage) will be 0 since capacitors draw current to charge.
After that, I couldn't figure it out.
Please help me understand.


texts:
I was trying to solve a simple electronics Thevenin/Norton equivalent problem, and I understand the concept as I solved many others correctly. However, I seem not to understand how this one can be solved, since my 3 approaches return different results.

I tried to explain the question and my reasoning as clearly as possible, as you can see in the image below. I am hoping you can point out what is wrong and right about those reasoning.


texts:
I am searching for a tiny board to that accepts an usb-c cable and outputs 5v.
To my understanding, for the few hundred milliamps two 5k1 resistors on the board would suffice. PD is not needed.
I already bought this, but sadly it's too big. Also, I don't need any data pins, just 5v and -.
Can anyone recommend such a board to power a tiny circuit?


texts:
Sorry if this isn't the right place for this.

I have a Uniden UH015SX (https://www.uniden.com.au/resources_main/pdfs/uh015sx_OM_2yrWarranty-Updated.pdf) which requires 13.8v of DC power, but I'd really like to run it from my 12v DC aux power point in my car.

Is there any way to make this happen?

The only solution I can think of (and it's far from elegant) is to run an inverter and then a switchable DC supply set to 14v.


texts: Is it possible to double the resistance of a potentiometer?

texts:
I'm starting a circuit-bending project using the rhythm PCB from an old Viscount electronic organ. The idea is to make a portable rhythm box by adding some extra controls and processing. What this question is about is my plan to add a half-tempo switch, in addition to the existing exponential fader that controls tempo.

My initial thought is to add a switch that will double the resistance when activated.

I assume this isn't possible except by placing another variable resistor on a circuit path, as so:

simulate this circuit – Schematic created using CircuitLab

This would require a design that forces keeping the two potentiometers physically aligned, though. If there's some trick to do this where one potentiometer will automatically 'track' the other one, I'd like to use that.

Edit: Per questions, here's a photo of the PCB:

And relevant part of the circuit diagram:


texts: What's the difference between typical and maximum forward voltage for an LED?

texts:
The datasheet for some LEDs I'm considering lists the forward voltages as 2.7V typical and 4.2V max.  (I'm looking at the "warm white" version.)

In the past, I've only ever looked at the typical forward voltage for figuring out the resistor value.  But I've never used an LED where the maximum value may be so different from the typical.

What factors affect the actual forward voltage?  Manufacturing variation?  Temperature?  Current?  Something else?

Suppose I have a 3.3V supply and that I want to drive one of these LEDs at 20mA. Based on the 2.7V typical forward voltage, I'd use a 30 Ohm resistor.  But if I end up with an LED that actually has a forward voltage of 4.2V, it won't light because 4.2V > 3.3V.

How do you design a circuit to accommodate such a wide range of forward voltages, or is there a reason I don't have to worry about the max forward voltage?


texts: Where is the memory inside this RFID tag

texts:
I dissected a RFID tag (Omni-ID). What I found is basically two components (wrapped in white plastic), a metal strip , and PCB having a wire:

I want to understand where is the memory to store stuffs? I was expecting a digital IC somewhere, but I could not find it any where.


texts: If resistors overheat and melt, like the one in series lights, will it cause fire?  I bought a LED Christmas lights. When I plugged in, the resistors started to melt and burn.  What happens if I keep them on?  Will it cause fire?


texts: Characterizing Photodiode's angular response

texts:
I like to make a simple experiment to characterize the angular response of a particular photodiode. (SFH206K). Current thinking is to use a flat table, use a red laser, turn off the lights, point  the laser to the photodiode at various angles and look at the current passing through with a multimeter.

I have done this test and find out my results correlate with datasheet nicely if the orientation of the photo diode is 0 degrees. However, if I change the axis of the photodiode, results do not match datasheet. (for ex. 45 degree, the photodiode's angular response is spherical, so this angular change should not have impacted the measurements).

I think my test set up is too rudimentary. Any ideas to measure what I am trying to measure more precisely? I am open to buying profesional equipment as well (needs to be very low cost though, say <1K)


texts: Thévenin's theorem exercise, resistances

texts:
I've some problem identifying the \$R_{th}\$

simulate this circuit – Schematic created using CircuitLab

Removing the load and short circuiting the Voltage source we get :

simulate this circuit

I've drawn the equivalent to better state my thought process :
First of all, in both cases \$R2\$ doesn't matter since it is short circuited.
For the first picture, if we consider a current in the circuit it wouldn't flow towards \$A\$ right? (Since it is an open circuit) And hence we'll consider \$R1\$ and \$R3\$ in series?
In the equivalent though, it somehow feels like a current will go from \$A\$ to the circuit. But I guess it's the same thing, it's an open circuit so current only inside and thus \$R1\$ and \$R3\$ not in parallel right?Or do we imagine a wire between \$A\$ and \$B\$ as is the case with Norton?
In the process of finding \$E_{th}\$ I separated the circuit in two :

simulate this circuit

\$R_{th}\$ is \$R1\$ but I couldn't figure out \$E_{th}\$
$$E_{th}+R_1i_1-E=0 \Leftrightarrow i_1=\frac{E-E_{th}}{R_1}$$
$$E-R_2i_2=0 \Leftrightarrow i_2=\frac{E}{R_2}$$
And that's it, can't go further, The \$C\$ -> \$R_1\$ -> \$R_2\$ -> \$D\$ -> \$C\$ KVL is not useful. (I've 0 current values btw)
Thank you for your time!


texts:
Greeting friends
I am having some trouble to calculate the capacitance equivalence in this circuit due to the short circuit? Calculate the capacitance equivalence in the circuit across terminals A and C: -

My solution so far: -


texts: What microcontroller can connect directly to a USB port?

texts:
Essentially, I just need to send some data to the microcontroller via USB, then the microprocessor decodes the data and drives an LED light strip, which runs at 5V. I'm having trouble finding the right microcontroller for the job.

The microcontroller just needs to have 2 serial in ports for USB communication, two serial out ports for communication with the LED strip, and be able to operate at 5V. It seems unnecessary to have a dedicated IC for USB communication when all I need is a serial COM port set up.

For example, here is the snippet of Arduino code that writes a byte to the LPD8806 strip:

void write8(uint8_t d) {
  for (uint8_t i=0; i<8; i++) {
    if (d & _BV(7-i))
      digitalWrite(dataPin, HIGH);
    else
      digitalWrite(dataPin, LOW);
   digitalWrite(clockPin, HIGH);
   digitalWrite(clockPin, LOW);
  }
}

To latch the data you send zeros to the strip.


texts: OK to wire shift register latch and clock together?

texts: The circuit diagram for the LED driver in this datasheet shows the shift register latch and clock being wired together. Will this work? I would assume so since TI has it in their datasheet. However, the description for the SCLK pin says that "A rising edge on SCLK is allowed 100ns after a rising edge of LAT". If that's the case how is it okay to wire the latch and clock pins together?


texts: How to increase amplitude in given oscillator circuit?

texts:
I am building a water atomizer using 1.65MHz piezoelectric transducers by this circuit. I am able to get desired frequency and am able to have water vibrating but unable to  atomized it. I think amplitude of waves is not high enough as it is withdrawing 0.2 amp only. Can someone help me increase power of this oscillator ??

Edit :- I have updated circuit. Earlier I forgot to mention inductance connected to emmitter.


texts: I found this diagram in the TI TLV431 datasheet. The diode symbol looks like a zener, but has an addition input on the side. What is this supposed to represent?


texts: VHDL Aggregate on Left Side of Assignment : Error in Simulator

texts:
I'm designing a counter with a combinational carry out (not registered).  To do this I have a concurrent assignment to create the unregistered sum with carry by extending the unsigned input before incrementing and assigning the sum to an aggregate of the incremented value and the carry out as shown below.  Count_a, the register, is in a clocked process with a simple assignment of nxt_cnt_a.
  Carry_Out_a : out std_logic
...
  constant Cntr_Width : positive := 13;
  signal Count_a, nxt_cnt_a : unsigned(Cntr_Width - 1 downto 0) := (others => '0');

  (Carry_Out_a, nxt_cnt_a) <= RESIZE(Count_a, nxt_cnt_a'length + 1) + 1;

This synthesizes fine and produces exactly the adder with register plus a combinational carry output.  But it won't simulate in Active-HDL.  It compiles OK, but I get a run time error.
# RUNTIME: Fatal Error: RUNTIME_0046 VHDL_test.vhd (130): Incompatible ranges; left: (0 to 13), right: (0 downto 0).
The resize function should create an unsigned of the right length and the addition operator is supposed to convert the integer to the same width unsigned before adding, giving the correct size result.
So why is a run time message being generated?  Is this a bug in the simulator?  If the syntax is bad, why would it not be caught when the code is initially analyzed?
Do I need to post the entire design?  It's currently 142 lines, but I could pare it down to a couple of dozen.  The rest of the design is the same counter written in more verbose manners as test cases.  This form is the simplest, so I'd like to get it working.
Here is the full test code. In this one the error is on line 26.
-- Test synthesis of counters and carry out flags
library ieee;
use ieee.NUMERIC_STD.all;
use ieee.std_logic_1164.all;
-- use work.Common.all;

entity VHDL_test is
  generic(
    CLK_HZ : REAL := 33.554432E6 );
  port(
    Clk         : in  std_logic := '1';
    Cnt_En      : in  std_logic := '1';
    Test_Out_a  : out std_logic;
    Carry_Out_a : out std_logic
  );
end VHDL_test;

architecture TB_ARCH of VHDL_test is
  constant Clock_Half_Period : time := 500 ms / CLK_HZ;  -- 14901 ps;
  constant Cntr_Width : positive := 13;
  constant Cntr_Modulus : positive := 2**Cntr_Width;
  signal Count_a, nxt_cnt_a : unsigned(Cntr_Width - 1 downto 0) := (others => '0');
begin
  -- Clk_gen: Clk <= not Clk after Clock_Half_Period; -- comment out for synth

  (Carry_Out_a, nxt_cnt_a) <= RESIZE(Count_a, nxt_cnt_a'length + 1) + 1; -- error

  test_ag: process (Clk) is
  begin
    if rising_edge(Clk) then
      Test_Out_a <= Carry_Out_a;
      if (Cnt_En OR not Carry_Out_a) then
        Count_a  <= nxt_cnt_a;
      end if;
    end if;
  end process test_ag;

end TB_ARCH;  -- VHDL_test

This error has gotten worse, lol   I thought I had a work around, but trying to use this in a useful program it fails with the forms that were working in the test code.  The only difference was the test code was assigning the carry bit directly to the output std_logic.  So I added a test case to use a signal declared in the entity.
  signal Test : std_logic := '1';

  (Test, nxt_cnt_a) <= ("0" & Count_a) - 1; -- works
  -- (Carry_Out_a, nxt_cnt_a) <= RESIZE(Count_a, nxt_cnt_a'length + 1) - 1; -- fails
  -- (Carry_Out_a, nxt_cnt_a) <= RESIZE(Count_a, nxt_cnt_a'length + 1) - One_uns; -- works
  -- (Carry_Out_a, nxt_cnt_a) <= ("0" & Count_a) - 1; -- works

Of course it works in the test code.  In my work code I also tried making Test into an unsigned (0 downto 0) which also fails.  The error is a bit different now.
# RUNTIME: Fatal Error: RUNTIME_0046 MilliSec.vhd (52): Incompatible ranges; left: (0 to 0), right: (12 downto 0).


texts: Getting the wrong KCL equations in op-amp circuit

texts:
I have the following op-amp circuit:

simulate this circuit – Schematic created using CircuitLab
When I use and apply KCL, we can write the following set of equations:
$$
\begin{cases}
\text{K}_1:\text{I}_4=\text{I}_1+\text{I}_7\\
\\
\text{K}_2:\text{I}_7=\text{I}_2+\text{I}_3\\
\\
\text{K}_3:0=\text{I}_1+\text{I}_2+\text{I}_8\\
\\
\text{K}_4:\text{I}_9=\text{I}_5+\text{I}_{10}\\
\\
\text{K}_5:0=\text{I}_3+\text{I}_6+\text{I}_{10}\\
\\
\text{K}_6:\text{I}_5=\text{I}_4+\text{I}_6+\text{I}_8+\text{I}_9
\end{cases}\tag1
$$
In the system of equations, \$\text{K}_6\$ gives the KCL of the incoming and outgoing current from the sources to the ground.

Question: there is a mistake in my KCL equations, but where is it? Because I get the wrong answers.


texts: Can a smd aluminum electrolytic capacitor be replaced with a normal electrolytic cap?

texts: I have a JBL Charge 2+ amplifier that during dissasembly I missed a major step and accidentally broke off about 2 to 4 of the SMD electrolytic caps. Instead of buying replacement ones I already have some normal electrolytic caps that aren't surface mounted and I was wondering as long as I find one with the same voltage and µF can I just use them instead? I know the amplifier still works as when I power it up; everything lights up but there's no sound, the amp still connects with bluetooth but I still get no output to the speakers. Can I replace a SMD electrolyteic capacitor with a normal though hole electrolytic capacitor?


texts: Safely driving a high power h bridge with optocouplers

texts:
I was looking into some high power H bridges (I was hoping to make an induction heater or at least a high voltage power supply). Some I came across are: this, this and this, to name a few.

I noticed this related question about driving a mosfet with an optoisolator. However, I may wind up using IGBTs or SCRs, which brings me to the next related question about how to use IGBTs as switches. Based on the answers to those questions, I should be able to use 8 optocouplers (one on either side of of the gate of each IGBT/SCR) to drive one or more of these devices. I already have plenty of optoisolators with some 5000V isolation voltage.

I was wondering if I could safely use those to drive one or more of the above devices, or possibly a general class of devices.

I could infer an answer and I suspect it to be yes, but I wanted to be very sure of how to use one of these devices before I shell out the money or tinker with the voltages they can put out. If the answer is no, what would recommend using to drive these devices?


texts:
I have a microcontroller (ATmega328) powered by a single cell lipo battery. I would like to make the microcontroller know when the battery voltage gets under a given level (someting around 3.5V) to output some kind of "low battery" alert.
Can I do that without using another battery? Does the internal analog reference remains stable if the power supply voltage changes? If so, can I simply connect the battery positive terminal to an ADC pin and output the alert when the reading gets under a certain number?


texts: Can parallel addition of a bigger capacitor damage the smaller one?

texts:
I have connected big capacitors to the speakers to increase the bass. Now, after months of using, I notice that one of the speakers sounds 2x low. I ejected those big capacitors, still the same.
I don't know how to test the caps. So I'm asking theoretically, could those big caps have damaged the small ones?


texts: Generate Power off of several motors at once

texts:
So in working on a project, I am considering generating power using several small 12V motors (made for DIY toy cars, very cheap on amazon) or by using one bigger electric scooter motor (24V, 250W, generally expensive). I am wondering if I could generate the same amount of power from a few small motors as I could from the big motor in a similar amount of time?

If so, could all of the small motors spin off of the same wheel (might move this to another question later...)?

Thanks in advance!


texts:
If a transformer's thermal fuse is blown, would it show Open Circuit? (that's what I would expect)

I.e if you have a transformer, that is showing continuity and expected valid resistance on the primary coil, does that mean you can be 100% sure that the thermal fuse is intact?

(Trying to diagnose a transformer that passes all multimeter tests for continuity/resistance, but produces no output voltage)


texts: How do I make an incoming negative signal a positive one?

texts: I am looking for a way to make a negative signal to a positive one. A positive signal has to stay positive. Does someone know how it can be done?


texts: Only 3 wires in 3 phase motor terminal box

texts:
I have a 3 phase motor with the nameplate below

At the terminal box you have your standard 6 pins labelled u, v, w, u1, v1, w1. However, the u1, v1, w1 is not connected on the terminal block but instead hardwired for star configuration inside the motor.
Is it possible to have the motor sent away to engineers in order for the other points to be exposed so I can configure the motor in delta or star?


texts:
I have one transformer. Primary 230V and two secondaries 14V/3A, 15V/3A and ground between them. I am curious can I use that transformer as center tap transformer.

Here is the picture:

I know I can use it as 29V/3A without problem and 15V, 14V alone.

I would appreciate any help, thanks. :)


texts: phono preamp input stage - exotic design

texts:
I found a very exotic (at least for me) moving magnet input stage of a phono preamp. It's taken from an old cartridge measurement system from renown brand. I simply can't figure out the logic behind this circuit.
Applying "hot" signal to both inverting and non-inverting output? In what configuration does this op amp work?
Placing a large capacitor between the hot signal and the ground? Does it make any sense?
Any input and thoughts much appreciated.


texts: Synchronize Arduino times to a 20ms difference

texts:
I'm working on a school project where I need to synchronize the clock on two Arduinos to almost perfect timing. I liked the idea of using Bluetooth but it has certain drifts/delays in timing. I was thinking of using a direct connection between the two boards when initiating and then disconnecting when in sync. Will the Arduinos keep "perfect" timing for a long period of time? Will this do the trick or are there better solutions?

I'm not restricted to using an Arduino. I need a latency of less than 20 milliseconds.


texts:
I need to use this controller with an external applied voltage to control a fan:
Currently it is controlled manually by a knob. I need to see the internal circuit to interfere.

How can I find the schematics of this product?
Is this a DC to AC converter?


texts:
I have a PIC12F675 that I need to program. I'm using a Pickit 2 and the Pickit 2 software. Supposedly I should be able to program it using this circuit, but the Pickit 2 software is not detecting the chip at all.

What's going wrong?

EDIT: I've added an image of my circuit breadboarded out. And here is where you can find the datasheet for the PIC12F675. Skip to page 4 for the pinout.

EDIT2: I just actually looked at the chips (dumb, but I kind of assumed mouser would send me what I ordered), and I noticed they're actually PIC12C671's. How much of a difference would this make?

Final EDIT: Wow! Thanks to everyone that helped me with this! I was not expecting this kind of response. It ended up being a small stupid problem just like I thought it would be. It was my fault for not double checking everything when I received the package from Mouser.