texts: Convert AC grid to DC and back to AC grid same phase

texts: I would like to execute long time running transistor switch tests with high currents. I would like to source AC power from grid, convert it to DC, pass through my transistor switch, after that I want to convert left power (some of the power will be radiated as heat from transistor and wires) back to AC and push it back to the grid. Simply I do not want to waste that energy into heat on some resistive load for example. In my opinion ordinary AC/DC converter on input and grid tie DC/AC converter (this converter have to follow sine wave from grid, I call it grid tie, I do not know whether it is proper name for such) will do the job, but my friends, which are more electrical engineers than I am (I'm software engineer actually), said that it will not work, but they are unable to explain why. I do not want to interfere with existing building electrical installation, I just want to connect to socket in wall with both my converters. What can you say about that, will it do the work, and if not why, and may how can I execute my tests in different way?


texts: The RX and receiver circuit is not working

texts:
I was working on a IR emitting and recieving circuit with the help of RX/TX and a SM0038 IR receiver and observing the flow of current in a LED but the problem is the LED never gets lit.
If the circuit diagram helps...


texts: Linear Voltage Regulator Quirk Using the TL072/4

texts:
I recently designed this simple voltage regulator circuit using a TL072 on LTspice (and multisim)

And the circuit worked as expected: it output 5V.

But when I built it on the breadboard, something weird and counterintuitive happened. The output of the regulator was actually 0V! When I checked the output of the op amp, it was around 14V. Now here's the funny thing. The inverting input was at 2.495V, as expected, but the non inverting input was at 0V. Despite this, the output of the op amp was 14V!
Next, I replaced the TL072 with an LM358. And guess what happened? It worked!!
Now what I want to know is why this circuit worked with the LM358 (but not the TL072) on the breadboard when LTspice and Multisim simulations clearly showed that the circuit works with the TL072.
Please let me know.
PS to get the circuit working with the TL072, I actually had to temporarily short the inverting and non-inverting inputs to get the circuit going. But that is not a proper solution. Also, the LM358 is inferior in performance to the TL072, which is why I want to find a solution and make the circuit work with the TL072.


texts: Getting the right frequency from an oscillator circuit

texts:
I have constructed an oscillator circuit using the resistor and capacitor values shown in the diagram above (from the Proteus ISIS simulator).

I run the circuit and use a switch to trigger the oscillator. I get the following waveform.

Using cursors in the oscilloscope I observed the time for each cycle of the waveform was around 7.6 microseconds which was considerably lower than the required frequency.

Could someone tell me why I'm not obtaining the required frequency? I understand that that it will never be exact, but this is a pretty large difference. Also, is there any way to obtain a more sinusoidal output?


texts: Simulating an RF remote control using an Arduino

texts:
I have a remote control for a video light, it's called 'Godox RC-A5'. The most detailed documentation I could find for it is here https://fccid.io/2ABYNRC-A5/Test-Report/Test-Report-2708894.pdf. The remote has 16 'channels' you can choose between and claims to operate in the 433.92MHz band.

I have an Arduino Uno with an RF receiver (https://components101.com/433-mhz-rf-receiver-module) and transmitter (https://components101.com/433-mhz-rf-transmitter-module). The documentation I linked to in the previous paragraph says that the remote control uses ASK modulation, so I tried using this but it didn't detect anything.

When I log raw input values from the receiver, I can tell it definitely goes high when I press a button on the remote control.

Is there any way in which I can look at the radio being sent from the remote control and decode it so that I can then replicate the signal and send it from my transmitter?


texts: Is electrical impedance at its maximum or minimum, at the acoustic resonant frequency of the material?

texts: For example, if piezo disc has lowest resonant frequency of 4kHz. At that frequency, would the electrical impedance be at its maximum or minimum?


texts: Why circuit from antenna datasheet is like this?

texts:
I'm designing circuit with nRF52810 BLE SoC and I have decided to go with ceramic chip antenna because it seems easier than designing printed antenna. The problem is that I'm just a 1st year student trying to design something like this for the first time. From SoC datasheet I understood that I need to find antenna with 50ohm impedance if I want to use the reference matching circuitry (QFN32, page 396) with 3.9nH inductor and 0.8pF capacitor. Please correct me if I'm wrong.

  All reference circuits are designed for use with a 50 Ω singleended antenna. A matching network is needed between the RF pin ANT and the antenna, to match the antenna
  impedance (normally 50 Ω) to the optimum RF load impedance for the chip. For optimum performance,
  the impedance for the matching network should be set as described in the recommended package
  reference circuitry in Reference circuitry on page 396 above.

Antenna matching circuit is on the bottom-right.

Then, in my understanding, every antenna has 1 terminal connected to signal source and second terminal floating, like on reference scheme above.

Let's take that antenna for example. It it 50ohm and 2.4GHz, so it seems like it fits. The problem is that I can't understand the circuit on page 3, it conflicts with SoC reference circuit and my understanding of antennas. Antenna on this design is connected to the ground with both terminals (one terminal is connected through matching component), and feed line is cut.

In my understanding, first terminal of antenna should be connected to the feed line through matching circuit (in my case from SoC reference circuit), and then to the SoC ANT pin, and the second terminal should be floating. Can you explain to me why circuit in this datasheet is like this and correct my assumptions?


texts: Why are there convex and concave resistor arrays?

texts:
I was wondering what is the history for having convex and concave resistor arrays.

Out of this EEVBlog entry and this Stackexchange question, the advantages of convex resistors are clear to me.
What makes me wonder and is also the reason for my question:

Why are there 2 variants developed in the first place?
And why do they continue to co-exist if, apparently, convex has mostly advantages over concave ones?

  Summary of convex resistor array advantages from the EEVBlog article:

  5-sided vs. 3 sided termination gives better solderability
  A larger gap between terminations reduces solder bridging
  Better view for visual inspection
  Larger terminations increase reflow soldering self-alignment
  Better part availability (70% of the market)
  Lower cost in general


texts: NE555 timer not working - how to identify the element at fault?

texts:
background

Im a beginner in the field of electonics, and I have been trying to put together a IR remote control / laser tag system using Arduino Nano. I am using a TSOP4840 receiver and a TSAL6100 as the emitter, so I need a modulated signal at 40kHz. To do that, I tried to use a NE555timer and use and "and it" with my arduino output pin using a 74HCT08 IC. I made a breadboard circuit. Here's a photo of it:

Unfortunately, the timer does not work. Its output pin is always at 0V compared to the GND. I tried a few different timer IC's, none of them worked. I made a second circuit, on another breadboard and using another 555 timer, wiring everything up as in the first circuit, none of it helped.

question

Following the NE555 timer datasheet, I tried to create a test circuit
 for it, but it didn't work, always having 0V between the output pin and GND. I used different breadboards and timer IC's. How can I identify my mistake/the faulty part of the circuit? I'm quite sure I wired up everything as it was shown in the datasheet. Here is the timers pin layout, the schematic from the datasheet and a picture of my circuit.

edit the mistake on the photo (yellow wire connected to pin 3 instead of 2) has been corrected, but was not the source of the problem. In the original circuit (top photo) I didnt make that mistake.


texts: MOSFET drain current equation vs on resistance

texts:
I have a very simple circuit. It’s just an n-channel enhancement MOSFET where Vgs is being driven to 9V and a relatively small 9ohm resistor sits between the 9V battery and drain terminal.

The way I went about the analysis was to assume the MOSFET is saturated and then use:
Id = Kn(Vgs-Vt)^2    where Kn is the transconductance parameter (W/LμC_ox) and Vt is the threshold voltage. For a Kn in the order of 1mA/V^2 and Vt approximately 1V, we get a drain current in the order of 8mA. These are all relatively standard values (I think).

When I simulate the circuit on LTSpice the current is in the order of 1A and it appears the simulation just treats the MOSFET as having a low on resistance between drain and source terminals so that the drain current is essentially just 9V/9ohm.

These two answers are two orders of magnitude apart, so it cannot be the case that the parameters I used in the simulation/calculation were just off (I simulated with a bunch of MOSFETs on LTSpice). To me it seems like there is something more fundamental that I’m not understanding in my calculations. When is it correct to use that above drain current equation and when should I rather treat the MOSFET as just being a small resistor between drain and source terminals (when turned on)? I’m assuming the drain current equation isn’t used that often because I can’t really find a value for Kn in datasheets.


texts: How to measure current on low voltage/current brushed motor driven by H-Bridge?

texts:
I have a gearbox which transforms the rotational movement to linear movement. It drives a pin which moves back and forward using a DC motor.

I need to know when the pin reaches the two "end-stops" (full back/full forward).

The motor is a simple brushed one and there're no sensors to detect pin position (and not enough space to add them), so I though to measure the motor current and when I read a fast increment it means the pin is full forward/backward.

The motor is 3V low speed and the current (free movement) is around 11.8mA.

How can I measure the current and read by a microcontroller to drive the motor via H-bridge? It will be cool to have an IC (eg. controlled via I2C) which act as H-bridge and current meter.


texts:
I am interested in masking my PCBs and I have a few questions about the process:
Using a dry film solder mask seems more straight-forward, but it is more expensive.
If I use UV solder mask in a syringe, I have seen that there are often problems when removing the transparent film. My question is, would it not be a good idea to use a laminator or an oven to heat the UV solder mask, before exposing it to UV?
Would that help to prevent it from coming off together with the transparent film (since that is the process that is followed with dry film solder mask as well, in order to achieve good adhesion)?
Any help?


texts: Linear operating range of an amplifier as a function of frequency

texts:
How does the linear operating range of an amplifier (the linear part of the function that describes Power Out vs. Power In), both in theory and in practice, vary with frequency? In other words, if I apply two CW of differing frequencies, will they begin to saturate the amplifier at the same power level or different?

I'm not well versed in the specifics of how an amplifier is made, but am trying to put together a report section to describe at a higher level some of the phenomenon of some RF equipment we are using.

Thanks!


texts: Flyback diode and MOSFET rating vs DC motor stale current

texts:
I'm trying to determine a suitable flyback diode for a DC motor controlled by a N-channel MOSFET. The specs the motor read:
Rated current: 2 A
200 mA no-load current draw @ 12 V
12 A stall current @ 12 V
No load speed of 5,500 RPM

The MOSTFET I have is IRF520.
Should the flyback diode have a "Maximum average forward rectified current" above 2A, 200mA or 12A?
(EDIT: The motor will only be spinning in one direction, so there is no H-bridge.)


texts: Is this AN on comparator with hysteresis wrong?

texts:
Reading this datasheet of the LM94022, chapter 8.3, where is shown the following example:

I don't know how they get the formulas. I more agree to achieve something like this:

taken from this answer.

What am I missing to get to the same formulas of the application example?


texts:
I was following this example of implementing a pole-placement with an Integral controller.
Matrices A_star=[-5 -3 0;1 0 0;0 -1 0]
B_star=[1;0;0]
desired poles -100,-8+i*11,-8-i*11
I know the procedure manually is to compare coefficients of det{sI-(A_star-B_star*K)} and charcteristic polynomial of the poles.
I have done this and arrived at the answer of K=[111,1782 ,-18500]
Even using MATLAB place command, I got the following result, K=[111.000000000005    1782.00000000008    -18500.0000000005]

from videoThe correct answer is K =

1.0e+04 *

0.0111    0.1782    1.8500

My Last coefficient is differing by a sign and I have spent a day on this. I have verified my matrices and poles, but his end result yields a different value.
Note:The video's values for K are correct as they give the stable response in simulink as compared to mine.


texts:
I have always been interested in electronic circuits since 3rd
grade when we lit a bulb up. I then always wanted to learn more and more. I'm a soft-more in high-school and  it seems like i've it a dead end now. Every thing I build seems to break right after I get it to work and nothing seems to work right. I spend
so much time tweaking one little
thing just for failure over and over
again. My whole room is just a pile
of broken stuff that broke/could never get to work. I just seemed to reach a peak. I see a small, fairly simple electrical circuit and trust them that it works, but I don't get what's going on. I get a transistor amplifies but when I see a bunch together to make a circuit, I don't get it and my mind blanks out. I would hope to design my own circuits from ideas, but that I'm even farther. I do have a bunch of books, but those don't even seem to help. I really am passionate about electronic circuits and understanding how everything works but it just seems like my brain has reached a limit and I all of the sudden got stupid and unable to get any more information in there.
I spend day after day working on my circuits but It just seems like I am digging on granite with a spoon.

What should I do next electronics wise to go up and increase my knowledge of electrical design? How can I keep my inspiration up and not give up ( it's really getting annoying having a 99% failure rate).

Thanks for any advice and I know this question will get closed, but I am really desperate for help.


texts: Finding Norton voltage and resistance and max power

texts:
My directions for this problem are to find the power delivered when RL=3 and then find the maximum power.

simulate this circuit – Schematic created using CircuitLab

I found Rth = R1//R2 = 1 Ohm. Then I used Vth=InRth to find that Vth = 6V.

After doing this, I used P=RL*(Vth/(Rth+RL))^2 to get P=27W when RL=3.

From here I set RL=Rth to find the maximum power, then used Pmax=Rth*(Vth/2Rth)^2 to find that Pmax= 9W.

I know this can't be right since the maximum power is less than the power I found before, but I'm not sure where I'm going wrong.


texts: I've come across a spec for 1.5 pair cable and wondered if it's just three conductor cable. It would be nice to have this confirmed, as well as have an explanation for why it's called in such a roundabout manner. Is the word pair a specific terminology in this context which somehow conveys something "(un)shielded 3-conductor cable" does not?


texts:
Unknown symbol in motor diagram
What is this marked symbol, please?


texts: Lithium-ion rechargeable battery, shelf life

texts:
For Lithium-ion rechargeable batteries, that have never been charged, or been charged like 2-3 times at most, some 2-3 years back, and having since-then been in packaged condition, what should I expect their condition to be ?

Reading this wiki entry, I understand the thing about self discharge-rate and durability in terms of recharge cycles, but haven't found much credible information about unused cell's shelf life. Do they degrade over time, if not used ?

PS> Reason for asking is because someone is offering me a small cache for such batteries (to used within RFID readers), for what appears to be a very good bargain.


texts: How to Choose Proper Components for Class D Amplifier Circuit

texts:
Hi I am designing a class B amplifier PCB using the TPA3122D2 amplifier chip. I am planning to base my circuit on the schematic from the evaluation board (see below).

I have tried building out this circuit on a breadboard with components of the values given below, but could get no output despite rechecking the circuit several times. I believe this might be because there are requirements beyond the values given on the schematics, specifically for the output inductors and capacitors (e.g. series resistance).

Can anyone advise me on how to select proper components for the output circuit?


texts:
I'm trying to understand what's the function or R2 resistor in this transdiode log amp configuration. I suppose I've to match the right value to give in order to minimize the effect of input bias current. In a simple inverting configuration I'd put the value of the parallel resistors in the feedback loop, but I don't know what to exactly do in this case. I'm using both OP27E opamp (so really low bias current) than uA741C. I've done some simulations in TINA with and without R2 and I noticed some differences that advise me to understand more deeply which R2 value I've to use. Someone can help me to figure out?

Update:
According to Hope consideration, I tried to place a R2=0, R2=2k (parallel of 2.5k Rpi // 10k R1) and R2=10k.
Seems that the R2=2k works good at very low voltages, and V_out decrease a bit according to the fact that the resistor is nulling the bias current. Isn't it?


texts: How do you calculate the output voltage swing in an amplifier?

texts:
I have already calculated the DC values and the downswing of the circuit. I am not sure on how to calculate the no-load voltage upswing.

The values already calculated are:

$$I_{C} = 4.416 mA$$
$$V_{E} = 5.3 V$$
$$V_{C} = 10V$$
$$V_{B} = 6V $$
$$A_{vo} = 0.995 $$

My attempt:

$$V_{CE} = 0.3$$
$$(V_{C} + v_{c}) - (V_{E} + v_{e}) = 0.3$$
$$v_{c} = \frac{v_{o}}{A_{vo}}$$
$$v_{e} = v_{o}$$
$$\frac{v_{o}}{A_{vo}} -v_{o} = 0.3 -V_{C}+V_{E} $$
$$\frac{v_{o}}{0.995} -v_{o} = 0.3 -10+5.3$$
$$v_{o} = -845.6V$$

The answer should be \$9.7V\$.


texts: What is the percent concentration of doping in n and p-type regions of typical solar cell?

texts: I have heard that you need a very small percentage of boron (p-type) and and phosphorus (n-type) in each respective region in order to achieve the desired concentration necessary for the workings of a solar cell. What exactly is the composition of silicon vs. boron (for example 99% silicon vs. 1% boron) in the n and p-type regions of a typical solar cell?


texts: Derivation of output impedance of emitter follower or common collector amplifier (using Thevenin's Theorem ?)

texts:
I was going through the AC equivalent circuit of Common Collector Amplifier from ELECTRONIC PRINCIPLES BY MALVINO 3RD EDITION and I came across the analysis for the output impedance of the circuit. Now if we look intuitively in the diagram from FIG 8-4(a) we can easily reach figure 8-4 (b) no problem at that...

Then from Figure 8-4(b) we reach 8-4(c) by Thevenization at the base...

But we cant get the diagram of (d) from (c) by Thevenization at the point Vout ....

where am I wrong? please correct me or show me the logic. They have applied KVL in the base emitter loop and then from the expression of the current they have constructed the circuit of figure (d) which has the beta-ac.

But Thevenization gives (Rs||R1||R2 +re')||RE ....

Please help me...
I am new to electronics.
Do i need to apply Zout=Vout/Iout...
What is the problem in applying Thevenin's theorem?

Update: I felt that due to the approximations of ic nearly equals ie and hence ib nearly equals ie/ß, we need to remodel the circuit of figure 8-4 (c) a bit as shown

simulate this circuit – Schematic created using CircuitLab

The modified version is:

simulate this circuit


texts:
I am working on what I hope is a simple project as I am dabbling in this field. I am trying to create a target (in the shape of a box) roughly 1m by 0.5 meters into which soccer balls will be shot (diameter of between 10 and 25 cm).  I want to be able to detect any ball which passes through the opening of the goal. I have looked at PIR sensors but am not sure if they will be able to detect a fast moving object (potentially up to about 3 cm per sec). Another concern I have is that it may be possible for a ball to remain in the sensor(s) field if it hits the edge of the goal and does not pass cleanly through and exit the sensor field.  If this happens I would want to make sure that the sensor(s) could pick up the motion of another ball which passes through the goal on either side or above the stationary ball.

The idea is to connect the sensors so that each "goal" is detected and that any miss (default if no goal is scored within a set time frame) is also detected.

I have read some similar questions regarding moving bullets and even soccer goals but these issues were not addressed.  Also, I would like this to be outdoor usable, meaning weather resistant.  I have looked at some weather proof ultrasonic range finders, although with any sensor I am concerned with dirt and other materials from obstructing the sensor(s).

Any help would be greatly appreciated.


texts: Digital equivalent of a double-throw switch?

texts:
I'm designing a circuit that would switch between stereo-jack inputs. Source audio would be plugged into one end, and on the other two ends, two different audio outputs. I want to be able to switch between one of the two outputs.
Physically, I know how to do this, it is very simple using a double throw switch.
However, if I want to do this digitally, using a micro-controller board to control the switching, what type of component would I use?
I know that the digital equivalent of a SPST is an NPN-transistor. What is the digital equivalent of DT switch? Any support multiple poles?
A poor diagram of what I want to do.


texts:
Noob here, I remember back in school learning how to code a Mealy next state transition table and deriving this equation using k-maps and then coding the actually equations for all the outputs rather than coding states with a bunch of if-else statements.

I found here how to setup the tables and kind of derive the equations but what's next? How do I implement these into the current_state and next_state's and program the output logic equations?

I've searched far and wide online and I can't find a thing on it. Is there a certain name for this? Maybe I'm Googling the wrong thing?

Any info, examples and guidance will be appreciated.


texts:
I am trying to create a gps application but dont get good data. I have heard that the most common fault is to use a invalid baud rate but so I have tried to look at it but without success. The PIC I am using is a pic18f45k20 with the internal oscillator. The problem is that the variable rx in the getPosition function dont get a good value. I also tried to change the ReadUSART to getcUsart but I get the same value with those two functions. i am using MPLAB X with the xc8 compiler. Also the gps module is http://www.servicepunkten.com/downloads/GlobalTop-FGPMMOPA6H-Datasheet-V0B.pdf

My code for init:

#define _XTAL_FREQ 16000000
void initUsart(){
TRISCbits.RC6 = 0; //TX pin set as output
TRISCbits.RC7 = 1; //RX pin set as input

CloseUSART();
UART1Config = USART_TX_INT_OFF & USART_RX_INT_OFF & USART_ASYNCH_MODE & USART_EIGHT_BIT & USART_BRGH_HIGH ;
baud = 103;
OpenUSART(UART1Config,baud);

//compare with the table above
RCIF = 0; //reset RX pin flag
RCIP = 1; //High priority
RCIE = 1; //Enable RX interrupt
PEIE = 1; //Enable pheripheral interrupt (serial port is a pheripheral)

ei();       //remember the master switch for interrupt?

}

void setupClock()
{
OSCCONbits.IRCF0 = 1;
OSCCONbits.IRCF1 = 1;
OSCCONbits.IRCF2 = 1;
}

#define PMTK_SET_NMEA_OUTPUT_RMCONLY "$PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29"
#define PMTK_SET_NMEA_UPDATE_10HZ "$PMTK220,100*2F"
#define PMTK_SET_BAUD_9600 "$PMTK251,9600*17"

void initGps(){
for(int i = 0; i < 16; i++){
    WriteUSART(PMTK_SET_BAUD_9600[i]);
}
for(int i = 0; i < 15; i++){
    WriteUSART(PMTK_SET_NMEA_UPDATE_10HZ[i]);
}
for(int i = 0; i < 49; i++){
    WriteUSART(PMTK_SET_NMEA_OUTPUT_RMCONLY[i]);
}
}

code for reading:

void interrupt interrupts(){

if(PIR1bits.RCIF == 1)
{
    handleUsartRx();
}
if(INTCONbits.TMR0IF == 1)
{
    handleTmr0();
}
}

void handleUsartRx(){
struct Position position = getPosition();
//do stuff with position
PIR1bits.RCIF = 0; // clear rx flag
}
struct Position getPosition(){
struct Position position;
position.fixed = -1;
rx = ReadUSART(); //read the byte from rx register

if(rx == '$'){
    rxIndex = 0;
    for(int i = 0; i < 50; i++){
        receivedData[i] = '\0';
    }
}
receivedData[rxIndex] = rx;
rxIndex++;

//Dont know which is the end string
if(strstr(&receivedData,"<CR><LF>") == NULL && strstr(&receivedData,"<CR> <LF>") == NULL){

    return position;
}

//EndString is found, start parsing;
char *parsedString[9];
splitNmeaString(parsedString);
position = createPosition(parsedString);

return position;
}


texts:
I have a difficulty with Altium giving me an error when I try to create a differential pair. I have placed my signal into blanket and created a net in the schematic. I also added differential pair directive pointing the two signal named with _N and _P

When I generate the ECO, Altium tells me this: "number of nets in differential pair is 1 instead of 2"

Those are the screenshot of how the parameters are input.


texts: Voltage Amplifier circuit for PWM amplification

texts:
I am using the raspberry pi to generate a PWM signal to feed the servo motor. The output voltage (Max) from a Rpi GPIO is 3.3V whereas I need it to be 5V for my specific application.
So I am thinking of using a Voltage amplifier, I have two choices:

1)A non-inverting amplifier like this:

Where Gain Av=Rf+R1/R1

2)A Transistor voltage amplifier something Like this:

Questions:

1)what would be the best choice?
2)considering the PWM frequency to be somewhere from 20-200KHz, Which one of those will provide the better output response?

Thankyou.


texts: Digital data coming out of a cell phone headset mic?

texts:
I want to connect a sound board / mixing console / whatever-you-prefer-to-call-it to the headset jack of my Motorola Android phone.  I know the typical TRRS pinout of Left/Right/Ground/Microphone, and I know about the mic being phantom-powered by the phone and using the external impedance to detect:

speakers only (long-duration short, could be fooled by direct connection to a line-out)
play/pause button (short duration short)
prev/next buttons (2 different impedances < 1kohms)
microphone present (impedance > 1kohms)
unplugged (open)

So I know I need an attenuator (probably a pot) followed by an RC highpass with R ~2k before it goes into the headset jack.  Not a problem.  What I can't figure out is, what's this on an unconnected mic?:

Kinda looks like a digital byte, doesn't it?  It repeats the same thing at this rate forever.  With a "bit" width of ~10ms (100bps, 50Hz) and a cycle time of ~250ms (4Hz), it sounds terrible.  Probably not intended to be heard directly.

This adapter is intended for cameras, so the color code is wrong.  A continuity checker says that the red plug is [S]leeve, which is mic for me.

Update:

I finally got around to adding a 2.2k termination to the mic plug and now it does this:

(same scale as before, just a different color)

I start an app that uses audio in, like an oscilloscope, spectrum analyzer, SPL meter, or call my voicemail, and it changes to this:

I don't have a good way to put a signal into it right now, but it looks like it works.  I'll just need to add a series resistor to make it play nice with whatever it's plugged into when there's no app running to use it.  I'll probably put it between the mixer's line out and the pot so as to guarantee a certain amount of attenuation.  (it's still a mic in, not a line in)

The weird thing though, is when I remove the 2.2k termination, I get this instead of the original:

Almost like it saw the resistor, configured itself to use a mic now, and didn't go back.  I'm still curious to know what it was doing before, but it looks like my project will work.


texts: AUX input or microcontroller in a musical tesla coil?

texts:
Alright so I am making a musical tesla coil. I have seen some online tutorials and what I noticed is that some people are giving the audio input using a microcontroller and programming it to produce notes at the required frequency which is the ideal method. But some kits that are available online provide an AUX port to give music input. I dont want to buy a kit as I have everything else figured out already.

I just need to know what would would be the advantages/disadvantages of using AUX input or a microcontroller so that I can decide what is best.

My goal is not to play single single notes but a whole song via the tesla coil.


texts:
I want to communicate with a microSD card with an ATmega32 using SPI.
I make a simple SPI loopback, and it works fine.

Now, how can I communicate with the microSD card to write and read simple bytes or strings?

I am using a custom board, ATmega32 on a breadboard and an SD card module from eBay. I was looking for if ATmegas are compatible with FatFs and if they can open, read, and write text files with ASCII characters. How can I use FatFs?


texts:
I'm new to SMD, and was thinking of using the SO-8 package for the LD1117V33, which I'm using to step down from 6v to 3.3v, running at about 50mA max.

I was noticing that while the other packages offer heat sync tabs, the SO-8 just has the center four pins (2,3,6,7) all as Vout. Should these just be connected to one large pad running under the IC, or just use a normal SO-8 footprint? I didn't see any specific footprint information for the SO-8 in the datasheet.

Please note that I'm not married to the LM1117; if there's a more suitable regulator for the given load, please let me know.


texts: What is the full form of PAR in terms of IEEE documents?

texts: Every IEEE standard has a PAR document, like I found CSD to be Criteria for Standards Development. PAR is a similar document which is approved before working on a standard. Apologies if the question is not fit for this site.


texts: Looking for two position right-angle vertically stacked wire-to-board connectors

texts:
Here's an approximate side view of the connector I'm looking for:

the leads extend out from the back, then drop at a right angle into the PCB.
I know they exist, because I have an old board with them in it, but it is locked in a lab indefinitely, so I can't look for a part number. I've tried a lot of searching, mostly with combinations of the classifiers two-position, right-angle, vertically stacked, wire-to-board, through-hole, etc.
They are fairly large connectors and should be rated for high amperage. I think 40A or more, but they might be rated for smaller.


texts: How to increase the power of an electric motor?

texts:
What's the difference between a 1HP and 2HP electric motor?
Slightly different dimensions:

They look almost identical:

Here are the specs:

Same top speed (RPM). Same Voltage. Difference in current required. What is physically different between the two? What causes one to draw more current than the other? Is it simply more winds on the coil? Thicker gauge wire? Larger stator/rotor? How is it they have the same max RPM? Shouldn't more power mean higher speed in the absence of other variables (e.g. weight)? What is the extra current spent on if not speed? Torque? Or is the extra current only drawn under load; in response to a physical resistance (i.e. drag) on the driveshaft?
These might seem like seperate, unrelated
questions but really im just trying to determine: what's the same, what's different; and to understand: why.


texts: MOSFET diffusion to substrate capacitance

texts:
in order to eliminate body effect one way is to connect the substrate to source when the well is for a single device (PMOS with a well in a CMOS for example) , but i read that it increases the source to substrate capacitance to connect them together , i don't really know the reason why would that increase the capacitance Csb ?
Thanks


texts: Power supply filtering RCL-filter vs alternatives (for LF-RFID driver)

texts:
simulate this circuit – Schematic created using CircuitLab

This schematic is the manufacturers dev-board design for the RFID-IC power Supply, using a large power inductor at 4A I_RMS and 22uH.

Calculating this design as an RLC filter, yields fc~2kHz (low-pass). Since for this design the power supply noise is superimposed on the antenna signal, any noise in the range of up to 20kHz (per datasheet) is critical for high read sensitivity. The RFID-tag modulates the Antenna field at ~4kHz, which to me seems the most critical frequency range.

The current rating of the inductor seems excessive, the antenna driver has a maximum at ~250mA which is well below the 4A rating of the inductor. Can a smaller inductor be chosen? I think the I_RMS rating is only relevant for maximum power handling and doesn't take into account effects of saturation. As far as I understand, the filtering properties will be lost when the inductor reaches saturation (however not very clear on this, if someone can recommend some literature I'd be grateful). The ripple on the input is in the range of +-150mV.
Is there a better/smaller/more elegant way to achieve comparable or better filtering between, let's say 200-20kHz?


texts:
I'm searching for a boost converter to convert up small voltage (min 0.5V / max 81mA) to 5V.
(the smaller the better)

Can you recommend a special type number?


texts:
I'm trying to pick the correct amplifier for the following circuit:

Rref is 1 ohm, Vref is ground, and RL is anywhere between 0-30 ohm which voult mean that Vout would have to be around 30ohm *250mA at max. The D/A converter will input 0-250 mV. The DAC I am using is the MCP4921 and it works really well.

However, I tried using the LT1206 as an amplifier, and it didn't work so well.  I have a stable 12V supply to the amplifier but I am unable to get the amplifier to work.

Any suggestions or other recommendations for amplifiers?

Using this circuit, I am unable to get V+ = V-. I've tried to implement a voltage follower circuit as well to test the amplifier, setting V+ to 5V, and I would achieve a 4.4V at V-  when the supply is turned off and a 10.6 V when they supply is turned on. Again, doesn't make sense to me.

The goal of the circuit is to control the current accross the load to vary between 0-250 mA by using the DAC. Also, The output of the DAC is a DC voltage.

Datasheet for LT1206: https://www.analog.com/media/en/technical-documentation/data-sheets/1206fb.pdf


texts: Efficient voltage auto-selection using MOSFETs - does it make sense to make an auto-select between battery power and external power?

texts:
I want to design a voltage-auto selector for a battery powered board that I am designing.
First Question
Now I could just connect the LDO of my board to the battery output of the battery charger IC, and that would work perfectly fine. However for better optimisation, I would like to bypass the circuitry for that, if external power is connected. The first question is if it is worth trying this, or is the gain by doing so, so insignificant that it makes no sense to attempt it.
If it is worth it
In my research I came across an article that showed the circuit below as a reference design for such an application in mind.

You can find the whole article at "https://www.edn.com/use-op-amps-to-make-automatic-oring-power-selector/"
Now I absolutely love the idea of using op-amps and PFETs to reduce power waste. But is there another way to do something similar? Perhaps something that uses a comparator configuration? Otherwise I will just copy that circuit. In any case all sharing of thoughts and expertise would be much appriciated.
Below you can find the results of a small simulation I ran as requested by the accepted answer's author. The resistor symbolises the load attached.


texts:
I have a Wemos D1 Mini that has no analog outputs, it only has digital outputs at 3.3V.
I need to power a laser with an analog signal 0-5V to engrave pictures on wood. The laser is moved across the image, and needs to adjust the power pixel by pixel. The time spent on each pixel is about 1ms.
The PWM frequency has not been decided yet so I am somewhat flexible with it.
What options do I have to convert this PWM signal to an analog signal? It has to be fast and relatively precise to avoid differences in pixels, so a RC setup is not an option due to strong fulctuations in the signal. (As far as I understood from reading, happy to find out that it is not the case.)


texts:
I was looking into building a battery powered USB charger for camping. It occurred to me that car chargers are pre-built and run off 12 V. If I made a battery pack out of 8x 1.5 V batteries in series and wired them to the electronics in a car USB charger would that work as a simple cheap and effective solution?

Also can I calculate the charges from the pack by summing the mAh of the 8 batteries and dividing by the mAh of the unit to be charged or is the efficiency of the device non negligible?


texts: How to control a blower using the analog output from a PID controller?

texts:
I built a biomass burner which is powered by a blower. For precise control of temperature I am using a PID controller PID500 from a company called selec . I passed the PID analog outuput to a VFD which in turn controlled the speed of a blower powered by a 3 phase motor. Everything is working as expected.

Now I am progressing with building a smaller version of this burner. In this case I am going for a centrifugal blower powered by a single phase motor. The specifications of this blower motor are

Voltage 230 volts
Frequency 50hz
input power 100 watts
current 0.4 amps
speed 2400 rpm
capacitor 2 mfd

I think using a VFD will be an overkill for this small project. As of now I am  controlling the blower speed manually using a voltage regulator but we overshoot or undershoot the required temperature.

I want to control this blower motor with analog PID output as in the previous case. I don't want a on/off kind of solution-Please correct me if my understanding is wrong. A proportional modulating control is required as it is good for precise temperature control.

I did my search and was suggested to use a electric digital dimmer control.

Would like suggestions and pointers which will let me get the right solution.


texts: Sensitivity of half and quarter wheatstone bridge

texts: Could anyone help me determining the different relation for sensitivity of wheatstone half-bridge and quarter-bridge using transfer function? How differently varies the sensitivity between diverse wheatstone bridge configurations and the implementation of strain gauges as replacement for fixed resistences?


texts:
I'm a little new to this, so bear with me:

I am working on a hobby-related project that involves the operation of two DC motors in parallel, powered by a NiMH battery. (Crappy circuit diagram included)

Part specs:

-Battery- NiMH 4000mAH @ 8.4 V DC

-Microswitch - Rated 15A SPDT to toggle motor operation

-Motors - Rated ~6V operation, 11A stall and 0.9A idle

-Wire 16AWG (if relevant)

Circuit:

Problem:

The battery I have for this project is rated @ 8.4V, whereas the motors are rated for 6 V. I've been looking into finding a way to reduce the voltage to prevent motor damage and remembered PWM from a class I took (I'm an EE undergrad). I figure I could use a PWM circuit to vary the duty cycle in order to prevent motor damage, while conveniently allowing me to alter motor speed with a dial (altering the duty cycle %) without the massive power dissipation a potentiometer would create.

However, I am at a loss as to how to implement such a circuit; the only background on pulse width modulation I have had involve the creation of a basic PWM controller, not on selection and designing one around a circuit.

The circuits I have found online seem like they would work voltage-wise, however when I look at the current ratings they always fall short of the motor stall current. (Example linked)

PWM 1

PWM 2

PWM 3

My question to you is either:

a) How can I make a PWM that is suitable for such a build, or

b) How can I select the right PWM controller to add to the circuit?

Thanks for any insight you can give, please let me know if any more information is needed.

EDIT:
It is worth noting that stall current is transient, as the motors reach max rpm, and thus the idle current, fairly quickly. There is occasional slight load on the motors, however it's not enough to be an issue. My only concern would be the hypothetical PWM motor controller having issues with the initial stall current.


texts: BJT : Why is collecter called collector and emitter called emitter?

texts:
In a mosfet transistor, we call the source the source because it is the source of charge carriers (electrons for n-channel and holes for p-channel) and the drain because it is the drain of the charge carriers.
Why is emitter called emitter and the collector called collector in BJT? is it for the same reason? Because in npn the charge carriers are the electrons and in pnp the charge carrier are the holes so emitter would be the emitter of the charge carriers and collector would be the collector of the charge carriers?


texts:
I have a device absorbing up to 12 amps that is powered by a 3S 12.6V lipo battery. Every time I have to start this device, I need to plug-in the battery and this is quite annoying. I would like to keep the two connected and have a MOSFET which does the job. But I don't know where to start.

Can anyone suggest me a possible circuit layout and eventually a MOSFET to do that?


texts: can I also use phasors/concept of impedances for non sinusodial signals?

texts: I know that phasors are great to solve circuits driven by sinusodial input signals but I was wondering if I can incorporate phasor concepts(like impedance) to circuits driven by input signals not necessarily sinusoids and get an intuition for what is going on at certain nodes. Guessing what a capacitor acts like is very difficult to me so I try to make my life easier with some tricks like this but I am not sure if it helps any. Does it work in any way?


texts: I need to simulate a 2:4 decoder on LTSpice however the component does not exist. Does anyone know of a way to simulate it?


texts: Getting negative pulses from avalanche mode transistors

texts:
Using a BJT in avalanche mode is a known way of generating very fast short pulses. Rise times and fall times can easily be sub nanosecond and amplitudes of many volts are possible.
Orthodox circuits like my work associate has built and tested produce positive going pulses. For our application we want negative going pulses. I built a 1:1 transformer to negate the positive pulses produced and it works plausibly for our application. Sure I could do or buy a better transformer but is not the best transformer no transformer?
If I used a PNP BJT instead of the normal NPN BJT and run a negative power supply voltage then on the face of it I would get our wanted negative pulses.

Will PNP transisters work as well as NPN transisters given similiar VCE and Ft specs?
What specificationss should one look for when selecting a BJT for avalanche service?  This application is for a test jig so cherry picking BJTs would be acceptable but never desirable which brings me to the third question.
Is it still true that avalanche operation of BJTs it too unpredictable for production where cherry picking is not allowed?


texts:
The antenna is constructed from copper tubing. The circumference of the hoop is less than a tenth of the wavelength of interest. The tubing is closed on all ends, except where it is penetrated with connectors for the coax. The penetrations are done with bulkhead connectors, such that the coax shield is connected to the tubing in both cases.

I think this is not unlike a "king type" B-field probe I've read about. Unfortunately I've not yet read about that probe beyond the linked description, so I'm modifying the design based on my own understanding of how it works. Usually this antenna is constructed with just coax, letting the coax shield be the antenna as the tubing is here. I want to use tubing for structural reasons. I believe that any common-mode currents that would be on the outside of the transmission line will instead be on the outside of the tubing wherever the coax is covered by the tube. Thus, what happens inside the tubing is not relevant to RF currents, and electrically, this is identical to an antenna made from coax alone. The red arrows indicate where I expect RF currents would flow.

The goal here is to make a coax-fed loop antenna that is well balanced in order to obtain close to the ideal small-loop radiation pattern, in particular the deep nulls perpendicular to the loop plane.

Clearly there will be some losses due to the lack of impedance matching between the \$50\Omega\$ coax and the antenna at the top gap. And as an electrically small antenna, it will not be efficient. For the receiving application I have in mind these problems should be acceptable.

Have I achieved that goal?


texts: What is the error in my circuit in Simulink?

texts: Please see the image below. I get this error when I try to run the circuit on simulink. Series RLC branch and Series RLC branch 1 refer to the two DC-Link capacitors of the inverter on the left side of the circuit. I have already tested this circuit on PSIM and it worked, so I don't understand what is wrong with it in Simulink. (I am new to Simulink).


texts: Voltage source for single transistor audio amplifier

texts: Here is a simple audio amplifier with an npn transistor. What should be the value of voltage source V2? How can I calculte it?


texts: How can a voltage follower's output have any current through it?

texts:
Voltage follower circuit is used to create isolation between two different kind of circuits. Due to high input impedance,, so the input current is much lower than the output current while the output voltage follows the input voltage. So the voltage follower provides large power gain across its output. Due to this behavior, Voltage follower used as a buffer circuit and can be used to isolate stages while building multistage filters or some other multistage circuit.

This quote is from this webpage.
I think I understand clearly the purpose of a voltage follower circuit, and this quote explains it pretty well.
There is one key aspect that I can't seem to grasp and I can't find the info anywhere:
The part of the circuit which is connected to the output consumes current.
Where is this current coming from? Since the battery is connected to the input of the op amp, it is hi-z and there is no current possibly flowing out of the battery.
How can a current form from the battery to the output stage of the circuit?
To my understanding, the output load would have the battery's voltage, but should not be able to operate because of the high impedance input being the only connected component to the battery.
It doesn't seem to make any sense.


texts:
For a low dropout regulator, what does the worst-case PSRR (power supply rejection ratio) mean?

I know what PSRR is, but I am not sure in what case the PSRR of LDO is the worst.

Thank you!


texts:
I bought a flyback transformer recently, 5908-05008, CF68A. However, when I try searching online for this model, there seems to be no pin out diagram or any information at all. Most of the FBT I saw had either 10 pins or 13 pins while this flyback has 9 pins.

I understand that there is 2 potentiometer for tuning Focus and Screen but other than that, I have no idea how to test it for it's winding, turn ratio, inductance value and KVA.

I was wondering if there is anyway to test and find out which pins are for what purpose and how to check the parameters for this flyback. Thanks!


texts: Efficiency of obtaining differential signalling from a single-ended manufactured transducers

texts:
This will be a conceptual question. I'm sometimes dealing with data-acquisition of transducers, like strain gauges, accelerometers ect. sort of sensors.
Most of these sensors have their own precision amplifiers. So what I mean by the transducer output is the amplified sensor signal.
These signals then go to data-acquisition's input amplifier which is simply a differential amplifier ect.
But most of the time the transducer outputs are single ended.
Sometimes I encounter all sorts of noise, common mode noise ect.

Since differential signalling is more immune to noise, I thought about converting a single ended signalling to a differential signalling as below(I want to implement Figure 2):

So here are my questions.

1-) Some transducers are manufactured and sold as differential signalling transducers. So they are ready to be wired to a differential amplifier.
But if one has a transducer and want to use it as differential signalling as in my Figure 2, would that be a wrong treatment?
Im asking because If I invert the signal myself to obtain a differential signalling as in Figure 2, then I might introduce noise to the inverted input by interacting it with the inverting opAmp circuit,
and that will not be common on both signals.
So my first question is: is it a common practice to convert single ended signalling to differential ended signalling(in the aim of noise immunity) where the transducer was actually designed for single ended signalling?

2-) If this method makes sense. Here is the typical inverting opAmp configuration:

I would choose R1 and R2 10k. How does the input impedance of the data-acquisition's differential amplifier have affect on choosing R1 and R2 here?
I want the inverting as precise as possible. Is there an opAmp category for that, an example would be great? I dont want use LM741 for instance.


texts: How to modify DS1307 RTC to use 3.3V for Raspberry Pi?

texts:
I bought DS1307 RTC but it is 5V so it can't be connected to the Pi. I know it can be modified to use 3.3V by removing 2 resistors. This sensor is different than the adafruit kit so I am not sure which resistors to remove. It also has 2 sets of pins. What are the extra pins for and which should I use and which pins do I remove?

Here is the image of the RTC:

Here's the datasheet for the DS1307 RTC.


texts: Does someone have a non-textbook analogy to explain elements of a circuit?

texts:
I was wondering if someone could explain with analogies what inductors, capacitors, transistors, diodes, and op amps do?

I understand the basic idea; I'm currently an Electrical Engineering student. I already know the textbook definitions, but I was just wondering if someone had some sort of analogy to sum up everything that isn't something from a textbook. :) I'd like to further improve my understanding, but to be honest, just learning stuff from classes and books is hard and painful and boring, because as a student it's still a challenge to see the BIG picture.


texts:
I'm in the napkin-sketch phase of a project that will be ~100 custom devices in a big mesh.

Each device is an ATMega328P on a custom PCB with 16-40 'mini' neopixels.

I plan to power the whole installation with something like this 5V, 10A supply (keeping my use of the neos subtle) or possibly a 20A supply if I need to, say, run the neos a bit brighter.

What I'd like to do is distribute the power through each board to the next, so that the whole installation has one connection to the power supply, rather than one per board.

My thought is to have two JST connectors on each PCB, one for +5VDC in, the other for +5VDC 'thru' to the next board.

Is this possible/dumb? This is more power than I'm used to, but I don't think it's so much power that I'd need bus bars, solder islands or a ridiculous (4+ oz) pour on the PCB. I'm thinking just a gigantic (~1.5cm) trace from the "in" connector to the "thru" one (and placing them close to each other).


texts: I'm trying to connect my mouse to my phone but I broke my otg cable. So I split a slimport wire that fits my phone and matches the mouse wire and wired it together but when I plug it into my phone the mouse doesn't turn on or work at all. I checked both of them before spliting them and they both work. Instead of buying a new otg cable I want to figure out how else I can make it work by rewiring it somehow. Can anyone help on how to fix it or different ideas? I also reconnected the usb port.


texts:
I got a old RC car + controller, I would like to increase it's range. I did a research and I found a idea here. The idea states:

  Here's what you do. Parts: one (1) NPN transistor. Tools: Soldering
  iron, wire cutters, wire.

  Idea: After going over my RC remote with a multimeter I've found that
  the amplifier(transistor)  inside the remote only runs at .2 volts
  So... using that as a first stage amplifier is a good start. Then,
  when you connect the 3v from the batteries to your
  amplifier(transistor) it'll be a   15x gain. So, your transistor has 3
  pins C B E connect C to the + terminal either on the PC board or
  straight to the batteries. B to where  the antenna used to connect.
  And E to the antenna wire. This tripled the range of my  New Bright
  remote control mustang. Also, remember your remote converts it all to
  a serial  message that gets decoded at the end point so it doesn't
  have to be all that great of signal  quality. It can be noisy as hell
  and it'll still get the message across. Good luck!

So I'm beginner and still I have no idea what I'm doing so I would like to ask about little explanation how I can wire the circuit.

I found in my house a TIP120 transistor.
If my schematic is wrong can somebody explain me how to get it working?

PS: Sorry for the bad schema, I wasn't sure how the components between the antena and the transistors are called.


texts: How do I amplify a dc voltage that is too weak to trigger the base in a transistor?

texts: I'm trying to take the voltage output from a 3.5mm audio jack and have it light up an LED according to it's voltage.  I was going to attach the left audio cable to the base of a 2222n transistor which would act as my amplifier to trigger the LED to light.  Unfortunately, the voltage reading off the wire is like .2 or .02 and isn't high enough to trigger the flow.  Is there any way to increase the voltage to trigger the transistor or would I have to use a transformer of some sort (or an op amp??)


texts: Elegant structure for coding embedded systems in C

texts:
Some questions regarding efficient coding style using C:

I'm working on 8-bit PIC controllers using C. I would like to know certain things about coding style and structure.

I have read that keeping one header file is good programming style. But for segmenting functions rather easily for debugging and future development, can we keep more than 2 header files? Or, is it error prone? I trust creating header files and declaring function prototypes will remove the extern declaration in each related source files by doing so. (i.e. eeprom.h,  data.h)
Is it a good practice to keep all variables in a separate header file? Also, how do you deal with variables that are needed in more than one source file?


texts:
I used circuit shown in this instructable to make an AC dimmer but everything goes fine if not dimmed much but then it starts flickering because of voltage fluctuation.

http://www.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit/?ALLSTEPS

EDIT - embedding circuit


texts: The current in the inverting amplifier circuit

texts: When we have an inverting amplifer circuit using opamps, we have resistor R1 which between the voltage input and the opamp, then we have resistor Rf which is between the input of the opamp and Vo.  If we assume that V- of the opamp and V+ of the opamp are both zero, doesn't this mean that we should have a constant I1 current.  For example if R1 is 100 ohm and the input voltage is 5V, we should have a constant current of 0.05A I1?


texts: What is the difference between an array and a bus in Verilog?

texts:
I have been learning Verilog and Vivado at school, and I am now very confused by the usage of busses and arrays. Can anyone clarify the following?

What is the difference between an array and a bus?

During declaration, a bus would look something like reg [9:0]data while an array would be reg data[9:0]. Is there a subtle (or not-so-subtle) difference in how the language handles these cases?
Why are is a bus declared with and index in front of the variable name, but referenced with an index behind? For instance, data[3] would work regardless of whether data is declared as an array or bus.

I have found it is possible (although confusing) to create declarations such as reg [4:0]busArray[3:0], which would create 4x 5-bit registers.

Is this bad practice?
How is this different from 2d array declared reg arrayArray[4:0][3:0]?

When should I use a bus and when should I use an array?

I have a few other related questions as well...

When you have a declaration like reg [7:0]data[1023:0], is is possible to access individual bits and ranges?

I have had trouble accessing ranges of bits. For instance, data[7:0][4] seems to work, but data[0][255:0] or data[3:1][512:64] results in a syntax error. Are there rules about how you can access elements in busses and arrays?

Is is possible to declare a multi-dimensional bus? (something like reg [15:0][8:0]data)
Is there a way to type cast an array so that it is treated like a bus? This could be useful in order to pass an array into a module designed to accept a bus.


texts: How does power dissipation for surface mount components work?

texts:
I know that with usual through hole components we can attach heatsinks etc. But how does it work with surface mount components? Is having a copper plate around the component the way to go? How do we go about calculating the area required?

In particular I am looking at this SO8 package surface mount switching power MOSFET IRF7452(datasheet). I am sure that it requires an external form of heatsinking other than its case. But I don't seem to see it written anywhere on the datasheet? How do you know how much maximum heat energy can be dissipated using the case of the MOSFET itself? How does one go about designing the heatsinking for something like this? Would the copper plane be connected to the ground? Which part of the chip will contact and transfer most of the heat?


texts:
I'm going to use a microcontroller to read 80 digital inputs (push button switches).
I'm wondering (just to understand, I don't have any critical time constraint) if it would take less time using multiplexing over a 9*9 matrix (but using one shift register on the rows to reduce used pins on the uC, and columns directly connected to the uC) or using 10x chained shift registers (74HC165).
I'm having hard time calculting that, so I'm asking for some clarification. Also, how does that change if I use SPI.
Other assumptions:
- uC: arduino uno
- I'd like to consider also the time needed in software to provide the data in a "clean" format.
Thanks


texts: Schottky Diode disadvantage as compared to usual diode

texts: Schottky diode have a low forward voltage drop (typically \$0.15-0.45V\$) and very fast switching action, as compared to traditional diode, which typically have a \$0.7V\$ voltage drop (Silicon diodes). What is then the advantage of traditional diode as compared to Schottky diodes?


texts: Is it possible to solder the back pins of an Arduino board?

texts:
To ensure a more stable connection to the arduino board, would it be possible to directly solder the wires to the pins below the board? Is there any risk of interference between the pins?

It may be an obvious question, but I wouldn't like to ruin an Arduino board :)


texts: Reason why polarized electrolyic on audio line doesn't blow up

texts:
I've seen the low-end IC audio amp datasheets recommending a simple (polarized) electrolytic on signal input, even for a split supply circuit that doesn't DC-bias the input. For example the datasheet of TDA2030 does that.

I've actually built that circuit out of curiosity if the capacitor C1's anode might get (significantly) DC biased by the opamp input, but I've measured a rather insignificant 1.7mV in my circuit at C1's cathode. Looking at the datasheet, the max input current for this IC is 2uA, so going through 22kOhm would max at 4.4mV. So neither theoretically nor in practice is it enough to ensure that the electrolytic capacitor is always biased the right way on sound/AC signals. My guess is it doesn't matter because the AC swings of the typical audio line are below the 1.5V reverse voltage usually needed to make electrolytics blow up fast enough to be entertaining/detectable. Am I correct or is there something else going on?

I've also connected C1 the "wrong way around" (on purpose, as a 2nd experiment) in this circuit, to see if anything bad might happen, and... nothing.

I've even put on it the max AC signal my sound card can dish (which exceeds my phone etc.), at a respectable 1.7V RMS, which is way more than what's needed to make the TDA2030 output clip like crazy, because it has high input sensitivity. Still nothing measurable/observable happened to the input cap.


texts:
I am currently looking into setting up a DALI system with my own programmable DALI master and (over time) a multitude of DALI (LED) lights.

The general idea is to use an already existing DALI python library to program the setup; basically I'd like to use something like MQTT to send / capture events and translate those into DALI commands.

The first issue I'm looking into is how to know which lighting fixture I'd be addressing. As I understood it, for the initial (short) address assignment / commissioning, first a series of random addresses are given and then the master just tracks back on those addresses and assigns the short addresses. All OK, but I was just wondering whether it's possible to choose the addresses in a deterministic way, i.e. based on the type of device / some unique identifier ...

The main issue I would see is that in case the master would lose power, it basically would lose all the short addresses, right?

I'm just not sure whether the backward frames (/the response the slaves send back) do actually contain any other distinguishing information, to base this on ...


texts: Are there any standard patterns for wiring a breadboard/solderboard?

texts:
My breadboard wiring is disorganized and this makes complex circuits hard to debug and so on.

Are there any standard rules for how to arrange the wiring?

Something like "always leave x holes between components" or "always put resistors before switches rather than after".

Or does everybody just make their own rules as they go along?

Any links to resources would be helpful.


texts: How will wire wound resistors affect the synth's sound?

texts:
I am soldering up Music from Outer Space: Noise Toaster synthesizer. The guy who designed it said that carbon resistors should be used ("The resistors should be carbon composition or carbon film"). But I have only wire wound ones.
Searching on the internet answers lead me only to confusion. Some articles say carbon resistors are noisy, but googling images on modern guitar/synth gear PCBs I see they use carbon resistors even today.
My question: how will wire wound resistors affect the sound of MFOS Noise Toaster?
Moog Delay:

Fulltone OCD v1.7 (2012):

This image is uploaded in addition to answer in the comments:


texts: Where can I get a microcontroller board for TI Stellaris?

texts:
I'm Looking at using one of the TI ARM chips (see list below) and I'm wondering what I should be looking for to do experiments with, the computer equivalent of breadboarding. I've seen Development boards, Evaluation Kit and a few others. I've also seen price ranges from $50-$5000 (clearly I'm more interested in the $50 end) so I' guessing some of these are WAY more than what I'm looking for. Mostly what I want is a board that wires the chip to power and IO connectors.

The chips I'm look at are TI's Stellaris serise:

LM3S{6618, 6753, 6911, 6918, 6938, 6950
     6965, 8730, 8733, 8738, 8930, 8933
     8938, 8962, 8970, 8971, 9781, 9790
     9792, 9997, 9b81, 9b90, 9b92, 9b95}


texts:
What "affordable" voltage and current calibrations tools are available? I'm specifically looking for

Voltage (and preferably current) metering
0.05% Accuracy minimum (preferably 0.01%)
14 bit+ reading (preferably 16)
Preferably 24V tolerant, though if it has a precision resistance meter too, I could scale it down sith some resistors.
1k samples pr second
Exportable to a PC (preferably real time)
Preferably with a DAC with similar performance.
Retails for less than 1000$

Edit:
Forgot to add what I consider affordable (1000$ max!).
And by precision I'm really thinking of the ADC max out of the box sample errors. I mean you could theoretically have a 22 bit ADC with 10% off samples. I want to use this to calibrate other ADC/DACs.


texts: How was this equation derived for a L-C negative resistance oscillator?

texts:
I'm looking over some old notes and saw this series of equations for a L-C oscillator. The first step is just writing a KCL equation for the circuit:
$$
\frac{V}{-R}+SCV+\frac{V}{SL+r}=0
$$

Where \$S=j\omega \$

The next step shows:
$$
S^2LC+S(Cr-\frac{L}{R})+1-\frac{r}{R} =0
$$
How was this equation derived from the original KCL equation?

simulate this circuit – Schematic created using CircuitLab


texts: What is difference between step-up voltage regulator, DC-DC converter, boost regulator

texts:
The more I searched throughout the internet the more confused I became.

Imagine I have 13 batteries, each of them 3.7V, 20A, 3000mAh and I want to power 1000 W 48V DC electric motor.

If I connect the batteries in series I will have 48V but only 3000 mAh.
If I connect them in parallel I will have 39 000mAh, but only 3.7V

However there are a lot of current being unused and I figured I could use some step-up DC-DC voltage regulator, but I am unable to see how they work and what kind of it will I need. I assume they will decrease the current, hence decreasing the capacity in order to increase the energy.

What voltage regulator is best for this, how much of the amps/mAhs will it affect?


texts:
I have a circuit like this.

Input of circuit is PAL signal.
Output of circuit whose AC coupled version.
Input

Output

But HSYNC part in the output looks like mirrored. It should be more negative than burst part.
Where is my problem? Why signal distorted?

I scoped again the signals:
Before the C1 capacitor & After the C1 capacitor

Both signals have same 1V magnitudes. But DC avarages are different from each other.
This is HSYNC zoomed:

This is CAMERA just hasn't connected to PCB(disconnected from PCB)

There is no "inverting property" on oscilloscope channels.

PCB image


texts:
I am finishing off my Atmega32u4 development board. Essentially a Teensy 2.0 clone.
I have little background knowledge, but I see boards with pours all the time.
Here I have made a GND and VCC pour underneath the MCU.

Is there anywhere else I should also pour?


texts: EMC-BCI. Coil injection and probe were calibrated at 100 ohm

texts:
As the title says my coil injection and coil probe were calibrated into 100 ohm loop line Impedance and it resulted an insertion loss (dB) for the coil injection.

and transfer impedance (dBΩ) coil probe.

To be able to use them in my system I need the insertion loss (dB) and transfer impedance (dBΩ) to be calibrated at 50 ohms and my question is:
Is there a way to calculate and to find out the insertion loss (dB) and transfer impedance (dBΩ) for the 50 ohm line based on the files/graphs that I have?
I am trying to find a way to use the following formulas but I don't have the complete information (always missing a variable).

All would be easy if I new what power (W) they used.


texts:
I've been looking at a few power input circuits and quite a few of them suggest an inductive choke with a large bypass capacitor followed by smaller bypass capacitors.

In theory this is what I interpret the target effect is:

Bypass capacitors provide low impedance at high frequencies, and the inductor prevents current surges from entering/leaving.

Essentially, in using an inductor inline and a decoupling capacitor it's creating essentially a series LC circuit. Now one of the properties of LC circuits is they have a resonant frequency. I modeled a LC circuit with an attached purely resistive load to simulate what the circuit did under different kinds of loads:

VG1 is a voltage source to simulate noise and VM1 is a product of the simulation software for measuring voltages (I'm using TINA-TI).

Here is the resulting Bode plot for this circuit:

As expected high frequency noise is very effectively reduced (if I'm not mistaken, outside the peak region it should decay at 40 dB per decade). However, there is that ominous spike at around 20 kHz where noise is actually being very effectively amplified from the resonant frequency.

Is this typically not a factor when it comes to regulating power to a board? Why isn't the RC filter created using bypass capacitors enough? Is it because the capacitor size required for an effective RC filter is too high? Or am I missing something in my model?

The example recommended power filtering schematic comes from Atmel for their AVR micro controllers.


texts:
I am looking into using a MOSFET in the ohmic region at a given VGS. However I am having trouble interpreting the typical I-V curve of a MOSFET.

Surely the y-axis parameter, i.e. the drain current, is generally the parameter that is changed by the x-axis parameter. But in this case, surely it is the y-axis parameter that is changing the x-axis parameter. Or to ask it another way, how can I accurately model the VDS change in a circuit?


texts: What is the true circuit behind an opamp?

texts: So, first year EE student, and I just learned about op-amps. I understand the ideal model, and know how to analyze them, and understand the idea behind them/the circuit that we were shown that is inside them. Except, that's not the real circuit, it has a dependent source. My question is, what is actually inside an op-amp? If we were to replace the dependent source with real sources, what would we see? (I guess this is also more of a question about 'What are dependent sources, really?'). I have searched everywhere, and I always find the same answer 'Dependent sources are useful tools to model a circuit'. But what are they really?


texts: Safely discharging large value capacitor without blowing it up

texts:
This is related to my previous question. I have this circuit in which I discharge the capacitor by turning ON M2. The ON resistance of the MOSFET I have in mind (the picture shows the wrong MOSFET in an earlier design) is 0.0035 ohm. I've placed a 1 ohm resistor in the discharge path to limit the current. The 40 mF capacitor (4 X 10 mF) will have a voltage of 0.6V when fully charged. So I'd have 0.5979 A current during discharge. Is this safe? Will my capacitor spark/blow up? Will its lifetime decerease if this is a repeated operation? What would be a safer option for discharge? I could increase the resistance, but I'd like to know exactly how much current is safe.

I need the charge\discharge process to be controlled by an MCU, so any manual discharge methods\removal of capacitor is not an option.


texts: Are there conventions for representing hierarchical components on a schematic?

texts:
Say I'm designing a device with a lot of repeated elements, like an 8-channel audio mixer. Each channel will have functional units that are identical and repeated, for example, an amplifier.

To keep the top-level schematic readable, my schematic capture software allows schematics to be hierarchical, where the top schematic has symbols which represent subcircuits.

An example:

simulate this circuit – Schematic created using CircuitLab

What conventions are there for visually representing this? Are there conventions to give the reader of a schematic a hint that A1, A2, and A3 are not discrete components or ICs, but a circuit defined on another page?

What conventions exist for naming (for printing on the PCB) the discrete components that compose these sub-circuits? Would it make sense to concatenate the name of the symbol and the components, so in the example above I'd end up with A1R1, A1R2, A2R1, A2R2, ...? Is there a conventional prefix for the names of the symbols, A1-A3 in the example, which hints at their nature? (As C1 suggests a capacitor, etc...)


texts:
When using the virtual ground concept to analyze op-amp circuits, the sign of the inputs (inverting/noninverting) don't seem to matter. Is this also the case in actual circuits? I also tried to simulate a circuit in the everycircuit android app and I can't see any effect of interchanging the inputs on the output.

I tried solving for the voltage gain \$\frac{V_o}{V_1}=\frac{A_dV_i}{V_1}\$ by finding the limit of the ratio as \$A_d\$ approaches infinity. I got the same expression for both circuits, which is \$-\frac{R_f}{R_1}\$.


texts: can't send characters using fpga cyclone iv

texts:
I'm trying to connect my FPGA Cylone IV (CoreEP4CE6) with Raspberry Pi 3 for communication through UART. The process (uart_rx) for receiving data is working fine, however, when I place another process (uart_tx) for transmitting data both process fail. I don't know why, in simulation everything works fine. Can I connect the Raspberry pins tx and rx directly to FPGA in/out pins?

library ieee;

use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity uart is
generic(
    freq: integer := 433 -- 50000000/115200
);

port(
    rx: in std_logic;
    tx: out std_logic := '1';
    data: out std_logic_vector(7 downto 0);
    clk: in std_logic
);
end uart;

architecture uart_arch of uart is
begin
-- uart rx process
-- receive bytes through rx port
uart_rx: process(rx, clk)
    variable start_recv: bit := '0';
    variable timeout: integer := 0;
    variable count: integer := 0;
begin
    if rising_edge(clk) then
        if rx = '0' and start_recv = '0' then
            start_recv := '1';
            count := 0;
            timeout := 0;
        elsif start_recv = '1' then
            if count >= freq then
                count := 0;
                timeout := timeout + 1;
                if timeout <= 8 then
                    data(timeout-1) <= rx;
                elsif rx = '1' then -- wait for idle
                    timeout := 0;
                    start_recv := '0';
                end if;
            end if;
            count := count + 1;
        end if;
    end if;
end process;

uart_tx: process(clk)
    variable start_send: bit := '0';
    variable timeout: integer := 0;
    variable count: integer := 0;

    constant message: string(1 to 5) := "hello";
    variable buff: std_logic_vector(7 downto 0);
    variable p: integer := 1;
begin
    if rising_edge(clk) then
        if start_send = '0' and count >= freq then
            if p > message'Length then
                p := 1;
            end if;

            tx <= '0';
            buff := std_logic_vector(
                        to_unsigned(character'pos(message(p)), 8));
            start_send := '1';

            count := 0;
            timeout := 0;
        elsif start_send = '1' then
            if count >= freq then
                count := 0;
                timeout := timeout + 1;
                if timeout <= 8 then
                    tx <= buff(timeout-1);
                else
                    tx <= '1'; -- put in idle
                    p := p + 1; -- next char

                    timeout := 0;
                    start_send := '0';
                end if;
            end if;
        end if;
        count := count + 1;
    end if;
end process;
end uart_arch;


texts:
I know just enough about electronics to do the occasional Arduino or Raspberry Pi project, as long as I don't have to understand too much of what's going on. I am a software guy who dabbles in hardware a tiny bit. So, I'm not even sure I can form a good question, which is why I haven't been able to Google an answer to this question.

I have made a small wearable device (about 30mm x 30mm x 10mm) that has one simple job. There is a magnet clipped onto the device. When the magnet is removed, it tells my phone (via BLE). Think of a sort of personal alarm device.

My first prototype uses a NC reed switch and works perfectly ... except that the reed switch is quite susceptible to false activation when jostled around too much. The device should only activate when the magnet is removed. As an improvement, I figured the solution was probably to use a hall effect IC. I've also read a little bit about MEMS. Cost is not an issue, within reason (i.e. sub-$20), but size and durability are absolutely important.

My questions:

First, is a hall effect IC an appropriate solution, or is there something else that would work better?
My assumption is that I must use a NC switch that is open when the magnet is nearby. This makes a digital IO pin go HIGH only when the magnet is removed. My reasoning is that if the switch is NO, then it will be closed when the magnet is nearby, making the IO pin HIGH most of the time. I believed that this would be an unnecessary drain on the battery. But, I recently read something to suggest that digital IO doesn't work like this. So, my question is ... does it use more power to maintain HIGH state than LOW?
Am I thinking about this all wrong? Is there a simple way to accomplish the same thing in a very tiny package? I am using a 3V logic Arduino derivative with plenty of pins. The device currently uses just about 50uA, on average, and I'd like to keep it that way.


texts:
I'm designing a circuit to take two load cells as inputs, and make their sum.
I'd like to know your opinion about the design.

Each cell is connected to one instrumentation amplifier (INA122P).

The supply will be a car battery, so I think there shouldn't be a lot of disturbance.
Please consider that the output will be connected to an ADC, but the cable will be long, so I don't know if I have to take into account some more issues.

It's not written, but the regolator is the 7805, so everything will work at 5 V.
For the summing part I found the AD8271 that seems interesting.

Any idea/correction/suggestion?
It's one of my first designs and I don't know if I miss something important..

Thank you

EDIT:

thank you all for your comments. Here is my updated schematic with your suggestions:

Some questions:

1.by connecting one output to the Vref of the second amplifier, I loose the adjustments (calibration) that I could do on the second load cell, don't I?

should I take into account some filtering for the supply or it's ok as it is?
why the ina122 is not a good amplifier? I could use it with the same configuration?

thanks


texts: What's the use of the bypass capacitor on the LM380 amplifier?

texts:
I've read the LM380 amplifier data sheet and application notes, and they show a power supply ripple rejection number that's based on the size of the bypass capacitor. There are also a few designs that use trimmer potentiometers into the bypass pin. Other than that, there's no actual mention of what this pin does or what the requirements are. (This is pin 8 on the DIP-8 package, pin 1 on the DIP-14.)

Here's the data sheet and application note link: http://www.ti.com/product/lm380

The data sheet also talks about a 100 nF decoupling capacitor on VS / GND, as usual for most ICs. But what is the bypass pin really for? Will the voltage ever swing negative, or can I use a regular electrolytic/tantalum on that pin?

Here's my proposed circuit (I'm learning KiCAD, so it's not all that great; apologies in advance for the vertical labels!) if it helps answer the question:

Also, regarding capacitor polarity: I'm assuming the output AC coupling capacitor can be a regular polarized capacitor, even though the charge of the capacitor and inductance of the speaker will temporarily reverse the effective potential when the output goes close to ground in a waveform swing?


texts: Connecting a Camera Hot Shoe to a homemade strobe

texts:
The Situation

simulate this circuit – Schematic created using CircuitLab

I need to trigger a strobe from a Sony Hot Shoe.

A 3.5mm jack lead comes out of the hot shoe.  Using a multimeter I measured 6V across the tip and sleeve of the jack, and when the camera triggers the ring and tip become connected like a switch closing.

Two wires come out of the strobe. Using a multimeter I measured 12V across them. When you touch them together, the strobe triggers.

If I connect the hot shoe to the strobe, it all works fine. When the camera triggers the ring becomes connected to the sleeve completing the circuit and effectively shorting the strobe trigger to ground and firing the strobe.

The problem is that when I plug the camera into to a PC through USB, the strobe stops working. Cutting the power wires on the usb does not fix this, but cutting one of the data wires does. We have assumed that the hotshoe circuitry must be somehow connected to the USB circuitry.

Off-the-shelf flashes work with the USB connected, but they also have 12V across the trigger leads, so we assume that off-the-shelf flashes are opto-isolated. We are hoping that opto-isolating the strobe trigger will fix the USB issue.

The ideal solution

simulate this circuit

Because there is normally 6V out of the hot shoe, and this goes to 0V when the short is created, the LED in the opto-isolator will normally be on. Therefore I need a opto-isolator that lets the phototransistor allow a current to flow when the LED is off, and stops current when the LED is on. Does this type of "dark on" opto-isolator exist, and what should I search for to find one?

Alternatively

simulate this circuit

If a "dark on" opto isolator doesn't exist, my idea is to use two optoisolators. The opto-isolator 2 will be powered from a separate 5V voltage source, that will be shorted out when opto-isolator 1 is closed. (i.e, no current will flow through R1 because there is a short to ground through opto-isolator 1). The problem is this requires a new separate power supply, and i'm unsure if it will work. Will this work and is there a better way to do it?

Thanks!


texts: Current Sensing problems in PWM-switching circuit

texts:
I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

A simple voltage source is connected to a resistor. The current flow is controlled via an NPN switch. I also have the INA169 current sensor (Here is the datasheet).

The current measurement from INA169 is driven to my my microcontroller's analog in, and the ground signal of INA169 is connected to my microcontroller's analog ground.

The NPN mosfet is driven by a pwm signal generated from my microcontroller. To effectively drive the mosfet I am using the ICL7667 Mosfet driver. In order for the circuit to work, I have connected the controllers ground to:

the mosfet drivers ground
the source of my NPN mosfet.

When the PWM duty cycle is either 0% or 100%, the current measurement is perfect. However, when the duty cycle is between 0% and 100%, I get a completely wrong current reading from my sensor. Is there something wrong with the circuit above or something that is overlooked?


texts: Interfacing memory to papilio fpga board

texts:
A while ago I asked this question about using a ram chip for generating VGA signal from an fpga. After reading the replies I realized there were considerable practical difficulties with doing that, and that my knowledge as a hobbyist was insufficient to make this work.

I now have a papilio fpga board and although I've for now abandoned my previous project for now I would like to interface this to an external static ram as a learning exercise.

So I was thinking of getting a static memory chip something like this one and making a small breakout board pcb for it (probably using seeed studio or similar to get it made), bringing out the pins to a female header row. I can then connect to my papilio using simple wires.

Now, assuming my soldering is up to actually making such a board, is there any reason why such a board wouldn't work? I realise that having 30 or so wires connecting the two boards probably  limits the speed I'd be able to use the memory at, but was wondering if it would work at all and if so what access speed I'd likely be able to get working?

The purpose of this is mostly because I want to try it even if there are better solutions I could just buy... and to give me the hardware I need to understand making memory access controller in verilog. I don't expect this to be fast enough to generate video signals from but wondered what kind of speed I might expect to work with such an arrangement?


texts:
I am experimenting with electrospray ionization.  The setup has a 4kV power supply connected to an electrode that is separated from a return lug (or ground plate) via an air gap, followed by an inline pico-ammeter and finally ground.  The way this works is that a small drop of solvent is applied to the electrode, the 4kV power supply is energized, and the solvent forms an aerosol electrospray "Taylor cone" between the electrode and return lug.  When this is occurring (it is not especially visible except via laser light) the inline pico-ammeter reads somewhere on the order of 20-100 nA resulting from the ion transfer.

I would like to test a very large number of electrodes by systematically switching the pico-ammeter & ground between the various return lugs.  My first thought was to use a multiplexer, but I'm not sure if this is even possible, and I have a few concerns.  Specifically, iIs there a mux that can switch a ground reference (through the pico-ammeter) to an open (high impedance) circuit, and has a low enough on resistance as to not substantially effect the 20nA ion transfer current?

Also, every so often the air gap gets a little too small and turns into a 4kV "spark gap" which results in having to change a fuse in the pico-ammeter.  What would be the best practices with regards to circuit protection for preventing this scenario from frying the switching circuitry?

For clarification, I already have a current measuring system, so I would rather not design one from scratch if it isn't necessary.  I am specifically asking about the identification of multiplexer transistor architectures (if any) that are capable of switching ground to a no load, high Z or floating condition. (like a mechanical switch or relay but much faster and more scalable)  Normally, low side switching with a low Rds(ON) would be the job of an N-Channel Mosfet except they generally won't turn on with an unloaded drain pin (to my knowledge).  Are there any solid state switching topologies that are capable of this?


texts: Understanding absolute value circuit operation

texts:
I'm trying to figure out how this circuit works:

It is a absolute value circuit; that is, the output follows the absolute value of the input. In the process of figuring out how it works, I am imagining a positive input voltage. If this is the case, then the first op-amp acts as an inverter, so the voltage above the diode is the negative of the input. So, I understand how the first part works. I then get stuck on the second part: The voltage at the non-inverting input to the second op-amp is Vin since no current flows through the lower resistor. If this is true, then the second op-amp tries to make the inverting input also equal to Vin. If it achieves this, then there is a voltage drop of 2Vin across the input resistor to the second op-amp, and hence a current of Vin/5000 flows through the feedback resistor. There is a voltage drop of 2Vin across the feedback, so the output voltage is either -Vin or 3Vin.
Can you please pick apart my logic and tell me why I'm wrong? I've been trying to puzzle it out for ages but I can't see the solution.


texts:
I am a novice to electronics, and I am currently building a home workstation. In this question on ESD chairs, the user Sparky256 said the following in his answer:

If you are wearing BOTH a wrist and a ankle/heel strap you take yourself out of the static-source equation, so you can pay attention to other static sources such as plastic containers and plastic tools.

For the ankle strap, can I just take a second wrist strap and wear it around one of my ankles? The problem with heel straps is that, if my understanding is correct, they are not connected to the ESD bench mount, and instead work by making contact with ESD flooring. Since I am at home, my flooring is hardwood -- not ESD flooring (since this is quite expensive and probably excessive).
I would greatly appreciate it if people would please take the time to advise me on this.


texts:
I am starting to learn transient analysis series RC which requires our own equations to be derived, but I don't understand how the voltage across the capacitor is given in the equation below from a KVL loop around the circuit (underlined in yellow):

I'm assuming it comes from the basic capacitor voltage/current relationship formula below, but would appreciate if someone would explain how it is given in this form mathematically.

Thanks


texts: Does adding a 22 Ohm resistor help in impedance matching?

texts: I read somewhere (sorry can't find the source) that adding 22 Ohms resistor on a digital line helps in matching impedance. Is it true? Is this a common value? Where should this be added? Near node A or B or on both?


texts:
This is kind of a simple question I haven't been able to find an answer for.

According to my notes, propagation delay increases as supply voltage decreases. While intuitively I would think it would decrease, this is reflected e.g. in this Epson ASIC features. I would like to know why this happens.

Thank you in advance.


texts:
i am working with tlp292-4 which is 4 array optical isolator ,i am trying to do the simulation of the component ,i have downloaded the simulation model from the manufacturers website but i am getting a unknown spice device type error .how should i resolve this arror?
site from which is downloaded the spice model:https://toshiba.semicon-storage.com/ap-en/semiconductor/product/optoelectronics/detail.TLP292.html


texts: I want to add a 74HC165 in schematic using Altium. But I'm unable to find 74HC165. Do I have to create own library for it ?


texts: How to manually create switches to light up a 7 segment display connected to ICs?

texts:
The circuit has been shown above. I have connected the ICs. Gave power to ICs using a 9V battery. I have got two questions:

How to simulate the inputs x, y, z using 'household' electrical circuit devices.
How to decrease the current from the 9v to a level tolerable by the ICs? Using voltage regulators?


texts: USB device with separate switch-mode supply. Do I just connect the grounds? Are ground loops an issue?

texts:
I'm designing a device which uses an FT201X USB I2C bridge for driving a series of LED controllers. The total LED current would far exceed the few hundred milliamps that a USB port will allow me to consume.

Figure 8.1 in the datasheet shows a typical usage diagram. If I wish to use a separate switch-mode supply to power the entire device, am I correct in thinking that I should just ignore the +5VDC rail on the USB device, and instead feed the 5VDC from my switch-mode supply into the VCC of the FT201X, and connect the switch-mode supply's ground to the GND pin on the USB connector?

My concern is that, since the USB port is going to be connected to an SMPS internally on the motherboard/PSU, I'd be bridging the grounds of two switch-mode supplies. I've read that this can be problematic, causing ground loop issues.

Is this likely to be a problem? If so, is there a standard way to implement galvanic isolation of the USB data lines?


texts:
Triac-based phase control of the mains power into resistive load.

According to this post,

https://www.physicsforums.com/threads/how-to-calculate-rms-voltage-from-triac-phase-angle.572668/#post-3737599

RMS voltage can be calculated as:

Vrms = Vpeak * sqr((2*pi - 2*angle + sin(2*angle)) / 4*pi)

I need the inverse of this. I need to solve this for angle.

I need to find the angle required to produce a required power level (specified as a fraction of 0.0 to 1.0 of full power).

While I can find the value of the angle by brute force, using the equation above, it would be better to have an equation that calculates the angle directly. My math is too rusty though.

Keywords: phase-fired controller, phase angle control.

--------------------------------------

C++ code, based on math done by Harry Svensson  below.

#include <iostream>
#include <cmath>

#define pi 3.1415926535

using namespace std;

float f(float power, float alpha){
    return 2 * pi - 2 * alpha + sin(2 * alpha) - 4 * pi*pow(sqrtf(power) / sqrtf(2), 2);
    //calculate f
}

float df(float alpha){
    return 2 * cos(2 * alpha) - 2;
    //calculate the derivative of f
}

float calc_alpha(float power){
    float alpha = 0.5;
    //starting point = 0.5
    float d, oldD = 1000.0
    bool again = true;

    while (again) {
        for (int i = 0; i < 20; ++i){
            d = f(power, alpha) / df(alpha);
            if (abs(d) > abs(oldD)) {
                // the equation is diverging; the starting point was bad;
                alpha = (rand() % 3000) * 0.001 + 0.005;
                oldD = 1000.0;
                break;
            }
            oldD = d;
            alpha = alpha - d;
            if ((d<0.001) && (d>-0.001)){ return alpha; }
            if (i == 19) again = false;
        }
    }
    return alpha;
}

float calculatePower(float alpha){
    return (2 * pi - 2 * alpha + sin(2 * alpha)) / (4 * pi) * 2;
}

int main(){
    for (int i = 0; i < 180; i += 5){
        float alpha = i / 180.0 * pi;
        float power = calculatePower(alpha);
        float calculatedAlpha = calc_alpha(power);
        cout << alpha << "\t" << power << "\t" << calculatedAlpha << "\n";
    }
    cout << "Press any key to finish.";
    cin.get();
    return 0;
}


texts: How could this circuit be reduced to first order low pass filter?

texts:
I was told that the bottom half of the circuit wouldn't matter due to having a corner frequency being significantly higher compared to the top half, or due to time constant (somewhere along this line..). Can you please help me understand why?

How would I go about reducing this to a first order low pass filter? (just one resister, one capacitor).

Thanks in advance.


texts:
I'm thinking way ahead about a possible future project which will contain, among many other things, a "DIY hearing aid" of sorts.  Microphones feeding earbuds with some DSP in between, all in a physically small space.  Not because I'm hard of hearing, but to account for an acoustic lowpass caused by a different part of the project.
I have some experience using digital live audio systems that claim about 1ms latency from the ADC's, all the way through the (quite involved) DSP, to the DAC's.  In other words, a stereo recorder hooked up to a Y-splitter at the ADC input for one recording channel, and the DAC output for the other recording channel, would measure about 1ms offset between them.  (see the test circuit below)
That's fine for a concert, where you can easily have more physical offset than that (~1 foot) between the mics and speakers, but for my project, I'm looking at several inches at most.
So, to get a feel for what I'm stuck with, and how much I need to optimize and overpower my DSP code to fit in the time remaining (small buffers, even down to a single sample just to get it out NOW!, which means I can't use SIMD instructions - increased sample rate, not for "audiophool" quality but just to shorten the turn-around time - etc.), what latency can I expect for a typical audio CODEC chip in this test circuit?:

simulate this circuit – Schematic created using CircuitLab
I expect a minimum of 2 samples, just because of how I2S works - latch and shift out from the ADC, then shift into the DAC and latch again - but I imagine that the conversions themselves aren't instantaneous either.
I've looked at a few datasheets and, at least for the cheap ones, I can't find a parameter that tells me the overall latency.  For their intended application of PC audio, I can understand that it's not important, but for this project, it kinda is.
What parameter(s) should I be looking for in a good datasheet?  And are there any rules of thumb / tribal knowledge that would be useful as well, in terms of realtime DSP where the output might combine with the original input, after a small speed-of-the-wave delay of the original input?  (1's of samples at 48kHz)

Of course, all of this might not even matter, depending on the acoustic lowpass that I end up with, for which this DSP needs to be a complimentary highpass with transducer-correction and peak-limiting.  I have no idea what that acoustic lowpass is going to be, so I'm looking for enough general information that I can evaluate it when the time comes.
(If the crossover frequency ends up being low enough and steep enough (overall latency is a small fraction of a single wave), this may all be a moot point; I'm not going to hear the original anyway, where it matters, so just throw some pre-fab code at it and call it good.  Or the crossover might be high or gradual enough that it does matter...)
Anyway, I'm looking for enough general information that I can evaluate it when the time comes.  Thanks!