texts: What happens when Schottky diode is protecting a pin from overvoltage?

texts:
If you are using a Schottky diode to protect an input pin from a voltage of greater than +5V, where the diode is connected (in the appropriate direction) between the pin and the +5V Vcc, doesn't that mean that you're dumping current into Vcc when (for instance) +7V is being applied to the pin?

If that is the case, could this result in damaging a battery or anything else?  If so, under what circumstances?

(Note: I'm aware that there is usually a resistor in such a circuit as well, but what I'd like to know is why I've seen schematics with these diodes using Vcc as a dumping ground for current).


texts: The metallic plate behind >2010's CPU's heatspreading plate is the actual chip die substrate?

texts:
I'm trying to find a formal document about the packaging of modern Intel's CPU's to learn about CPU chip construction. But explanations are quite basic and informal sources differs whether the metallic looking plate behind the heat spreading plate are the die package or the actual silicon substrate.

I expect to find that the metal plate is like the metal interface of TO-220 transistor package, since I guess a <1mm silicon waffer is quite fragile by itself.

I would like to find formal resources since there's a lot of opinions that differ out there.


texts: No I2C ACK from Honeywell HIH-6120 humidity sensor

texts:
There is an Arduino library for the HIH-6130 which has exact same I2C protocol as the sensor I am using which is the HIH-6120. I am using the same two lines of code to tell the sensor to take a reading:

Wire.beginTransmission(0x27);
ret = Wire.endTransmission();

ret is 2, which means master received NACK on transmit of address. Looking at this on my analogue scope it appears the sensor makes an attempt to let SDA rise to 1 but it is late and too weak:

(about 10us per div, 2v per div, sync on falling SDA)
A delayed by B gives

(1us per div)
Pullup resistors are 2k. Sensor address is 0x27 according to HP. Min clock frequency is 100 KHz which is what Arduino is giving.

What on earth is wrong?


texts: Driving led matrix with SN74LS595N instead of SN74HC595N

texts:
I worked out how to drive a ledmatrix (8x8) width monochrome leds with 2 SN74HC595N on a STM32F103C8 over SPI. It works. (Un) fortunately I got my hand on a free a bag of SN74LS595N's.
I tried to drive the leds with that, because I think that should be possible.
However, when I simply replace the SN74HC595N with the SN74LS595N, things "do not work". That is, no led will power on. However, in the datasheet, I cannot find any difference in pinout, but only in clock speed. I tried to lower that, but still no led startded.
Googling etc. is really hard, since google cannot distinguish SN74LS595N from SN74HC595N, and goes mostly for usable results for the SN74HC595N.
So my question is: what are the differences between the SN74HC595N and the SN74LS595N in respect of the STM32F103C8, and what are specific settings to keep in mind.


texts: how can I generate Output 2 to give a fixed delay pulse on a rising and falling edge of Input?

texts:
how can I generate Output 2 to give a fixed delay pulse (about half a second or less) on a rising AND falling edge of Input?

                     ________________________
Input    ___________|                        |___________________
                     ________________________
Output 1 ___________|                        |___________________
                     __                       __
Output 2 ___________|  |_____________________|  |________________`

Specification: Input / output: 2.5 - 3.3 V DC at < 40 mA.

I need a board or PCB or something that makes Output 2 possible. this board can be powered by anything, from an wall outlet to a micro usb power supply. does not matter that much.


texts:
I have an ISR that increments a counter every 5ms if the switch is pressed.

If the counter becomes 200 then do Reset. I plan to add more functions to be called from the counter value.

After a few encounters with ISRs, I have got the expert advice from this site to keep ISR short.

Then how should I keep the ISR properly or near to perfection.

Is it about keeping flags?

I trust calling ISR that do long routines is a bad architecture. But then how can I call long routines from the value of flags in ISR if it is kept in another source files other than main.c?


texts: What are these small stubs on the USB data pins of this device?

texts:
When disassembling a failing USB 2.0 flash drive, I noticed a feature on the USB data pins, that I do not understand from the perspective of a student just getting started with PCB layout:

They're definitely traces and not a hole in the solder mask (it's more visible on the phyical device than in the picture), and are much thinner than the actual D+/D- traces running to the ICs on the flash drive itself. I was under the impression that stubs of any sort, and any unnecessary trace length on the D+ and D- pins would be poor in terms of EMI/EMC/noise, due to reflections at the ends of the stubs, and the fact that they appear to be radiators, yet they're included on the drive (produced by a major flash memory maker). This flash drive doesn't have a metal shield around the USB port, as it's one of those connectors where just the PCB fits into the area between the receptacle's body and the receptacle's pins. The only part of the drive not pictured is a plastic body that protects the PCB itself and wraps around the sides and back of the connector for correct physical dimensions for a snug fit.

Could someone enlighten me as to the benefit of these traces?


texts:
What is the definition of apparent power?
How to calculate apparent power for three-phase circuit? Is it S = S1 + S2 + S3 or S = sqrt(P^2 + Q^2)

where

P is total active power P = P1 + P2 + P3

and

Q is total reactive power in system Q = Q1 + Q2 + Q3?


texts: How to add red led light to my white led lights

texts:
What’s the best way to wire the red led to this system? I have it now hooked up to 1 300 ohm resistor & each two white led lights out of 4 hook to 200 ohm resistor. The entry unit is powered by 3 x 3 V coin cell batteries n controlled by on/off switch but when all connected all the  lights are very dim! Please help.

Should I use a complete different power source just for the red Led? Or is the resistor values not correct? It worked fine when just powering all 4 white leds but now it seems to not get full power across each led!


texts:
I was going through some questions on Transient Response of circuits. Then I encountered this question! Though, I was a bit confused at first, I initially approached in an intuitive way. My first approach was as the circuit looked symmetric horizontally, I reduced the circuit to an equivalent circuit with a single capacitor of 2 Farad and a resistance of 0.5 ohm in series with the capacitor. Then I could easily find time constant = (1.5 Ohm) * (2 Farad)= 3 Second. Then, I could write the expression of Vx(t) as [1 -  (2/3)exp(-t/3)] V. But at this time, I was a bit confused because can we really reduce the circuit in that manner just because it has symmetry and further the capacitors have different initial voltages. So, I proceeded to systematically analyse the circuit. I wrote differential equations and solved for Vx(t). But, surprisingly I got the same answer as before. Moreover, I got a first order differential equation for Vx(t). Is it because I could reduce the circuit into one capacitor format? Also, what is the order of the circuit? It looks like this circuit has order 2. But, then, while solving for Vx(t), why am I getting a first order equation? And what will be an elegant method of finding the expression for Vc1(t) and Vx(t)?

Edit:- I simulated this circuit in LTSpice and here is the waveforms. Red, Blue and Green curves are for Vx, Vc2 and Vc1 respectively.


texts: How can I draw the diagram using few decoders for this truth table?

texts:
For the truth table above, abc is the input and xyz is the output.

I do know how to draw the diagram using a decoder in case of when I have only one output.
How can I draw the diagram using a decoder when I have 3 outputs for this case?

This is what I am guessing

After I apply the advice, here is what I have


texts: Do I need to consider shunt admittance for line losses doing load flows?

texts: If I have a long transmission line (Pi model) the current just go through the equivalent impedance of the line, but I've seen demonstrations that include this shunt admittance as if the current flows through them as well.


texts:
We have an NIC (computer A) connected to Marvell 88e1116R via Ethernet cable, the Marvell chip is then connected to Xilinx FPGA, the FPGA connected to ADSL Analog front end (AFE), the AFE is connected to a phone grade twisted pair cable. At the other end of the cable there is another ADSL AFE, followed by FPGA, then Marvell PHY chip which finally connects to another NIC (computer B).

The problem is summarized in the following manner:

Data flow from NIC to PHY = ok,

Data flow from PHY to NIC = nothing!,

Data flow from PHY to FPGA = ok,

Data flow from FPGA to PHY = ok,

It's important to note that when the two NICs try to talk to each other, everything seems ok except of two issues:

1- Marvell PHY (on both sides) receives data coming from FPGA with no problem, but does not re-transmit the same data to NIC (on either computer A, or B). We tried many solutions with no luck.

2- it was noticed that both NICs try to broadcast at the same time.

If we attempt to connect the two NICs directly together (just to check our network settings) everything works fine.

We're hitting a brick wall with this issue. Your kind assistance is highly appreciated.

Checklist:

1- Marvell PHY crossover register set (checked).

2- Marvell reset pin (checked).

3- link status between NIC and PHY (checked).

4- loopback testing (checked).

5- PHY MAC address (not applicable in our scenario. PHY is acting as pass through device).

6- computer/NIC network settings (checked. Direct NIC to NIC link works fine, but when we add the PHY/FPGA block in between; the above problem arises).

Please help..

Best wishes,
F. Sulaiman


texts: current density value for inductor used in boost converter

texts:
I am designing boost converter. I need to select inductor for the same. As a new bee i don't know the criteria for selecting the same.
(1)what is the maximum current density of copper bare wire for inductor used in boost converter?
(2)what is industry standard for the same?


texts: Can't recognize circuit element in old clock mechanism

texts:
I am spending my free time thinking of how to make an old clock in my hometown working again. Here is a picture of the mechanism. I can't recognize the marked parts. Hope somebody of you can.

In this photo one can see two unknown elements of the same type, as well as element marked with an arrow. This looks like a metal pin that makes contact with unlnown part.


texts: Is there a minimum mosfet drain current?

texts:
Most people spec mosfets based on their maximum drain current capabilities. I'm looking to use a mosfet to switch a load of 25nA. Is there a minimum drain current specification?

I can use a parallel resistor to increase the current through the mosfet, but I'd like to know if I can get away with not doing that.


texts: Correct Term for "shorting a resistance to start a diesel motor"

texts:
I'm currently translating some German technical terms for my English-speaking co-workers. The terms all relate to the Mercedes-made flame-starter for a diesel engine.

I've come across the term "Startanhebung", which (from my understanding), describes a process in which an in-series resistance is shorted to trigger an amplification circuit to increase its power output in order to start an engine. For example, this process is supposedly necessary when attempting to start an automobile engine with a low battery voltage (e.g., 10 V).

I have a background in electrical engineering and a minimal understanding of technical German, but engines - especially diesel engines - are foreign to me. Does anyone know what the correct English term would be for the process I've described? Or does this process even make sense?


texts: Stable dc voltage for raspberry pi connected with Truck power outlet

texts:
I have an IoT project with the raspberry pi as the microcontroller. Now my device connects with the power supply of a truck i.e. via the 24-volt cigarette lightning adapter.

The device has few push buttons which need to be detected once pressed. To power down the 24 volts - 5 volts I am using the lm2596 based buck converters. Push-button is detected once the GPIO pin is set high i.e. by default they are set low.

Now what I have observed is sometimes the push button gets automatically detected without any pressing. This happens very less but still, it's a major drawback for me. How can I solve this? What is the issue here? Because if my circuit was wrong then this should happen regularly but it doesn't. If this is a voltage ripple problem, how can I solve it?

EDIT: Added the schematic diagram(I have not attached the resistors as shown in the diagram).  I have a basic layout for the push buttons with a total of 6 push buttons attached. The input pins for receiving the signal from the push button on the raspberry pi are set to LOW(GPIO.pul i.e. button callback function will activate once the pin goes from low to high. This is the code written for that

GPIO.setup(dumpbutton,GPIO.IN,pull_up_down = GPIO.PUD_DOWN)
 GPIO.add_event_detect(dumpbutton,GPIO.RISING,callback=dump_button_callback,bouncetime=500)


texts: I assume that AOZ1280 buck converter misses datasheet specs

texts:
I have tried setting up this cheap AOZ1280 buck converter to give output of 3.3V from input of 3.5V to 4.2V without success. Please check my schematics below.

What happens is that I can not achieve an output of 3.3V unless the input voltage is at least 4.2V. If my input voltage is at first 4.2V and then I reduce it to 3.9V, for example, the output will stay at 3.3V. But if I initially connect 3.9V to the input, I will get only around 1.95V at the output. The output voltage will slightly increase with increasing input voltage, but at 4.2V there will be a bump and 3.3V at the output would stabilise.

At that point, while 1.95V can be found at the output, feedback pin gives 0.5V - where should be 0.8V (page 3 of datasheet) and LX pin frequency is around 800kHz. Where 3.3V is at the output, feedback pin is at around 0.8V, and switching frequency is around 1.3MHz, all as it should be.

According to my understanding, this misses datasheet specifications in two points:

Page 3, Input Under-Voltage Lockout Threshold for VIN raising is 2.9V. In my case it seems to be at the voltage I receive some output voltage, but not what is desired
Page 3, recommended operating conditions; Output voltage range: 0.8V to Vin

I even tried replacing with higher inductor with bigger one rated 3.3uH 4A, but with no change (as you could guess). All testing done with 1k resistor as a load. I can not understand at which points my circuit is (partly) failing. It should be quite simple and I stuck closely to datasheet recommendations.


texts: Finding Current in Parallel RLC Circuit with 2 voltage sources?

texts:
I've spent sometime learning about step responses for series/parallel RLC circuits, but this problem takes things a step further, since C seems to be in parallel with a series combination of RL and a voltage source. I'm trying to find out what i(t) is for t≥0, since the switch has been closed for a long time before opening at t =0.

My understanding is that for the step response, the solution calls for a second-order differential equation that takes into account both the forced response and the function for natural response. So when I focused on the t=0- condition, I set the inductor as a short circuit and the capacitor as a open circuit. From there, I also set i(t=0-) = i_L(t=0-). I used KVL to solve for i_L(t=0-):

i_L(t=0-) = (20V + 10V)/(5Ω + 5Ω) = 3 A = i_L(t=0+) <-- (I believe this is the initial current across inductor and R2?)

As for finding v_c(0-), I did a voltage divider to end up with:
v_c(0-) = (5Ω)/(5Ω + 5Ω) = 5V = v_c(0+) <-- (I'm assuming this is the initial voltage of capacitor?)

Now what I don't completely understand is the t≥0 condition. With the switch open, the left side of the circuit is ignored, leaving only the right side of the RLC circuit as the circuit reaches steady state. The problem is:

From the way I modified the circuit, it seems to represent a series RLC circuit. Which would lead to the neper frequency (α = (R/2L) = 5 and resonant radian frequency, ω = (1/sqrt(LC)) = 5, leading to a critically damped response. From here, the general solution of the step response for series RLC circuit is:
x(t) = Xf + D'1te^-at + D'2e^-at, with x either being v or i, and "Xf" being either the final voltage or final current
At t=∞, it's readily known that capacitor acts as a open circuit again, and the inductor as a short circuit, and because V2 is included in the reduced circuit, my understanding is that the final voltage, or v_c(t=∞), is 10V, and that the final current across R2 is ~ 0 A at the steady state. I even verified this with the use of the Falstad online circuit simulator shown below:

I am quite lost on this issue on finding i(t). What I do know is that I am dealing with a series RLC circuit for t≥0, and that the general solution for i(t) takes the form of:

iL(t) = I_f + D'1*t*e^(-at) + D'2*e^(-at).

Does anyone have any ideas as to how to solve for i(t) for t≥0?


texts:
A function generator is hooked up to two resistors in series.

The voltage across the function generator changes over time, shown by the different graphs

The questions asks to find the output voltage at points w,x,y,z with respect to the ground.

I have a few points of confusion: how does the current behave? If d is grounded, doesn't current just leave the loop? What does the voltage output actually mean?

I know only have a very basic understanding of circuits: Ohms Laws and Kirchhoff laws so this question is giving me some trouble.


texts:
I am trying to design an rf mems switch whose conpcept is shown in the image.

I am thinking to use microstrip for transmission of signal. Is there any recommendation for minimum width of ground plane of microstrip? Something like 5*w


texts: Huge drop in voltage when connecting output to pin of microcontroller?

texts:
I have an electret microphone pre amplifier and peak detector circuit that's working great. The microphone picks up sounds and I get a steady DC voltage that, depending on the volume of the sound the microphone is listening to, is somewhere between 0 and ~3.5v

I need to feed this into an ADC pin on a AVR microcontroller though so that I can read in the relative volume that the microphone is getting.

The only problem is that when I connect the circuit to the ADC pin on the microcontroller, my peak voltage drops from 3.5v to about 100mV.

I'm connecting the pre amp and peak detector circuit to an STK board that the chip is running off. When the board is powered off the peak voltage I'm reading with an oscilliscope (and with a multimeter) is correct but it massively drops down when I power it on. I still does exhibit the same sort of behaviour as it should though (the peak rises when there's noise) but I need the peak to be around 3.5v (not 100mV) as I need to a great resolution in the ADC value I read in in my software.

I have connected the grounds of both circuits to the STK board's ground so I don't think that that is the issue.

Can anyone give me any sort of idea about what might be going wrong? Is it something to do with the internal resistance of the microcontroller? Am I perhaps putting too much current into the ADC pin? I'd really appreciate any help.

edit: I'm using pin A7 on an atmega16.

edit 2:

This is the pre amp circuit I'm using: http://www.zen22142.zen.co.uk/Circuits/Audio/lf071_mic.htm

and this is the peak detector/rectifier:

and the code to get the ADC value:

unsigned int ADC_read(unsigned char ch)
{
    ADMUX = 0b11000111;

    ADCSRA|=(1<<ADSC); // start conversion

    while(!(ADCSRA & (1<<ADIF))); // waiting for ADIF, conversion complete
    {
        ADCSRA|=(1<<ADIF); // clearing of ADIF, it is done by writing 1 to it
    }

    return (ADC);
}

I can't see how the code would have any effect though.


texts:
What is the simplest way of generating 42.8 [MHz] square (or sine) wave? I want to clock fast ADC  for SDR purposes. I thought about wideband opamp and 10.7 [Mhz] cystal 4th harmonic. Is there any other solution?

Edit:
I did search for specialized ic's but without success. I am looking for one piece device available for hobbyist. I live in EU and I don't want to import.

Edit2:
For more clearance:

Simple solution: power in, clock out
Constant frequency
Reasonable stability (for radio purposes)
PLL is an alternative
If you want to recommend device please do it only if it's available in mayor European retail distributor.
Most companies do not send samples to Poland (unless you are a company which I am not) so samples are out of option :(


texts: Accuracy of a single to differential ended circuit

texts:
I have single-ended senors/transducers which are hooked up to a DAC in single-ended configuration. The transducers are calibrated by another company with certificates and they can output from -10V to +10V DC.

For mitigating common mode noise issues I want to convert these transducer outputs to differential ended. Currently I'm using coaxial cable with BNC connectors in single-ended earth referenced configuration and the sources/transducers are floating. I want to switch to diff. ended configuration and plan to use twisted shielded cable with BNC connectors. Below illustration roughly shows the current and planned cases:

After some research I found the following topology for single to differential conversion. LT1054 is just there to create negative supply for the opamp rails.

My questions are the following:

1) Now the voltage measured by the DAC which is Vo+ - Vo- is two tiimes the transducer's output voltage. I can see this is expected because of mirrored outputs. In this case should I reduce R3, R4, R5, R6 to 5k or simply divide the voltage by two in software end? Which is more common or convenient? (edit: I forgot to mention the DAC range is -10 to +10V so for 7V transducer output it will be in trouble to measure 14V)

2) My concern is that in this topology one solders the resistors himself. So the resistor tolerances and accuracy would effect the output. I mean if the transducer outputs 1V the diff output is 2V in simulation. That's alright and expected. But in real those resistors together with wires will not be exactly 10k. So instead of 2V it might read 2.1V which is quite large error. So Im wondering: Am I in wrong direction when trying to convert accuracy important single ended sensors to diff. ended myself this way? Or should I use a ready chip? When trying to mitigate common mode noise I dont want to introduce offset error to the transducer output by this circuit.


texts: Electron concentration in an intrinsic semiconductor at room temperature

texts:
For a Si atom, band gap energy is around 1.1 eV which means that an electron in valence band needs at least this much energy to jump to conduction band.
Also, at room temperature, typically energy of about 25 meV is 'readily' available. This implies that at room temperature no electron should make the transition from valence to conduction band. Still experimentally it is found that electron concentration of about 1.5*10^10/cc is present in conduction band of Si at room temperature.
How is this possible?


texts: What exactly is or how does a weak signal come into play in VHDL?

texts:
I'm diving into VHDL and I couldn't really grasp the idea(?) of weak signals.
I understand that '0' and '1' are (strong) signals. This is quite common knowledge from my point of view.
How do weak signals now enter the arena?


texts: The correct formula for the frequency of a kacher brovin circuit?

texts:
I was planning on building an kacher brovin circuit
Now, I know for a regular tank circuit
Frequency \$f=\frac{1}{2\pi\sqrt{L1C1}}\$.
However I read that the frequency of a slayer exciter is using L2 and its self capacitance as the terms for the frequency formula.
Which makes sense because L2 is wired to the base of the transistor.
So is that the same case for the Kacher Brovin circuit?
Does the capacitor just act as a voltage boost to the inductor, with the frequency being a function of L2 and its self capacitance?
What is the frequency?


texts: What is the use of pull-down networks in CMOS gates?

texts:
Below you can see the basic CMOS inverter. What I don't understand about this particular design is the purpose of the n-channel mosfet which is the part referred as pull-down network.

What if we didn't put a NMOS in there? In low input voltages, we would have Vdd as expected but we would have ground voltage, which is zero, on output when we provide the network with high input voltage as well since p-channel mosfet would act like an open circuit hence blocking Vdd from reaching output cable.

Thanks in advance.


texts: I2C communication with different power sources

texts:
Will I have some trouble if I try to establish a I2C communication between 2 µC powered from two different source?

Both µC run on 3,3v but this voltage is provide from a different regulator (LM317). Exact 3,3v isn't guarantee due to resistor tolerance. Since both regulator have same ground, there is no big voltage "gap" between the µCs.

I'm pretty sure it's gonna work but I'd like to have the EE community acknowledgment.

simulate this circuit – Schematic created using CircuitLab


texts:
I Followed The Following Circuit For The Logic NOT Gate from This Website http://www.northdownfarm.co.uk/rory/tim/basiclogic.htm

Here is My Circuit Which is Intended to Perform The NOT Function and Drive the Motor on Low Voltage (0).

simulate this circuit – Schematic created using CircuitLab

But Its Not Working , I Don't KNow What's Wrong ??


texts: How to find voltage in this circuit by superposition

texts:
The problem:

  When the switch SW1 is in left position, ammeter AM1, with negliable inner resistance, shows current IA1=0.1A. When the switch SW is in right position, ammeter shows current IA2=0.15A. Find E2 by using superposition.

What I tried:

Try #1:
When I try using superposition and shut down the generator E1, I get U23=E2. When I shut down E2, I get U23=0. So by using superposition I get U23=E2+0=E2 but that doesn't help me find E2...

Try #2:
I tried compensating serial connection of E2 and ammeter with an ideal current generator Ic.
$$Ic=\begin{cases}IA1&SW1\leftarrow\\IA2&SW1\rightarrow\end{cases}$$ Then I tried finding the voltage between the nods 2 and 3 by using method of contour currents but all I get is U23=E2 or U23=0 as in previous case which is true but that doen't solve the problem.

How do I find E2 by superposition? When I try finding it, I constantly get E2=E2...

simulate this circuit – Schematic created using CircuitLab


texts: Best way to compare value in register with constant assembly AVR

texts:
I am new to assembly and AVR. What is the best way to compare two values like in C:

#define SOME_VAL 55
int current_counter = 0;
...
...
if(current_counter==SOME_VAL) {

}

In assembly I have the following code:

.EQU SOME_VAL = 55

.def current_counter = r19

What is the best way to compare the current value with a defined constant?


texts: How a Computer Represents a Number Electronically

texts:
I understand how computers represent decimal numbers using binary. I have yet to absorb this video on how computers add numbers, which looks helpful.

Before understanding that though, I would like to understand at a deep level how a computer stores and represents a number (8 bit, 16 bit, 32, 64, 128, 256, not sure if they can store above that). There are multiple aspects of this:

How it is stored on disk.
How it is stored in memory.
How it is stored in the CPU / ALU / etc. to actually use to manipulate / perform calculations.

I don't need to know all the details of it, just something to point me in the right direction / an overview. I understand a little about flip flops, which store 1 bit in main memory. I am only interested in here in how numbers are stored in memory and in the CPU / ALU, not the disk. But if the disk is simple enough would be nice to know about that.

In terms of main memory, maybe there is somehow 8/16/32/etc. connections of flip-flops, or perhaps no, main-memory is just bits and you point to locations in these bits. I am thinking in terms of the x86 mov instruction, e.g. mov edx, [ebp + 8], which might move bits between memory or between memory and registers.

In terms of the CPU / ALU, it seems to just boil down to registers, so the numbers would be in the registers. But here they do make the distinction between 8/16/32/etc. bit integers, so maybe there is some electronics structure that implements this.

So this question is about knowing how the following works, at a high level / overview:

How integers are stored / represented in main memory electronically.
How integers are stored / represented in the CPU / ALU electronically.


texts: How to correctly bond two 200 amp main panels on a 400 amp service

texts:
I currently have a 200 amp service with a single 200 amp meter. That meter feeds a 200 amp main panel on the other side of the wall that the meter is mounted to (think standard residential installation). I then have a 100 amp sub panel fed off of that 200 amp main panel. The bonding screw is removed from the sub panel.
I'm going to upgrade to a 400 amp service, replacing my 200 amp meter with a 400 amp meter and replacing the 100 amp sub panel with a 200 amp main panel. This new main panel will be fed by an external disconnect next to the new 400 amp meter and the old 200 amp panel will continue to be fed how it is now.
Do I leave the bonding screw in this new panel or not? What other bonding consideration do I need to account for?


texts:
I was just thinking that when we have
$$
\overline{|v(t)|^2}=\frac{1}{2t}\int_{-t}^{t}|v(\tau)|^2 d\tau
$$
we couldn't apply Parseval theorem, for it is normalized. For applying Parseval Theorem, we would have to write
$$
\lim_{t\to\infty}\int_{-t}^{t}|v(\tau)|^2 d\tau = \int_{-\infty}^{\infty}V(2\pi f)df
$$
But in this way we are accessing the whole quantity that was dissipated by the signal. Then, when we want to do a noise analysis and use
$$
\overline{v_{T}^2}=\int_{f_1}^{f_2} 4k_{B}\,T\,R\,df
$$
which is the Thermal Noise, we are referring ourselves to the WHOLE dissipated voltage on those frequencies, and not the MEAN dissipated voltage on those frequencies. Is this correct?


texts: What is DC resistance of the Wi-Fi antenna?

texts:
What should be the DC resistance of an external Wi-Fi antenna (when measured between center and shield of the SMA connector)?

In case of:

DIY "Pringles" antenna
Consumer grade antenna, connected to external USB WiFi adapter

I believe there should be no difference between #1 and #2, right?


texts: Op Amp's Negative Power Supply to Ground

texts: I am using a standard 741 Op Amp from TI. For me to amplify any signal, I am required to set +Vs = 15 Volts and  -Vs = -15 Volts. I am now concerned as to what will happen if I connect -Vs to 0 (ground) instead of-15Volts. Will the Op Amp work as it does normally ? How is the gain affected ?


texts: 3 Phase motor changing rotation on startup intermittently

texts:
I have a total of three 3-phase floating fountain aerators.  Last year they functioned properly.  This year when I connected them, two of them were running in reverse and 1 was running forward.  All motors have submersible plugs, so the wiring cannot be changed upon hookup.  The hookups are keyed so they can only hookup one way.
I shut off the system, swapped wire 1 with wire 3 in the panel on the 2 motors that were running in reverse.  When I started them up again.  1 of those motors was running in reverse and the other forward.  I then swapped the wires on the one running in reverse and it began running forward at that point.
So now, all three fountains are running normally, but I am afraid to leave them running in case the phases switch on startup and them running in reverse causes the impeller to fly off.
This seems impossible from my understanding 3 phase motors, does anyone have any ideas?


texts: Calculation vs. simulation of DC output voltage from full wave bridge rectifier, through voltage divider, with no transformer

texts:
I'm designing a circuit using an Arduino to measure / monitor US line voltage; single phase 120VAC (170v peak) @ 60Hz.  The circuit itself is a simple full wave bridge rectifier using 1N4007s.  The output is fed into a voltage divider with a 10k R1 and a 1M R2, then into one more 1N4007.  There is  a 100nF filter cap after the diode.  I've simulated the Arduino's ADC with a 100M load.
The simulation shows the DC output across the 100M load peaking @ 1.55v after about 300ms.
This is fine if it's real, but with no real load, I would expect it to be closer to 1.68 (170 * (10k / 1010k)).  Is the simulation correct?  If so, what am I missing in the calculation?
Here's a link to an online simulation of the circuit: simulation
And the schematic (pardon the nonstandard rectifier layout):
If there's a better/cheaper way to do the voltage measurement, I'm open to that too.


texts: Are the building blocks of complex circuits built of gates or transistors?

texts:
I can probably rattle off the design of a full adder off the top of my head, as a network of gates. And given a few minutes, I can probably give circuit diagrams for all the gates involved.

But is this really how building blocks of larger designs are put together? As a programmer, I spend most of my time in a high-level language, but I've been known to drop down to assembly for tight inner loops, simply because the abstractions cost a little bit of efficiency and in some areas every cycle counts.

So similarly, I could imagine a situation where an adder would be designed not out of discrete and separable gates, but as a more complex amalgamation of individual transistors, to improve power consumption/latency/whatever.

Is it potentially worthwhile, and is it done in practice, to design modules such as adders on a transistor level, or is everything just gates?


texts: What is the exact definition of propagation constant of a two-port network?

texts:
Wikipedia says that the propagation constant of a lattice network is

$$\gamma = \ln\left[\frac{\sqrt{\frac{Z_a}{Z_b}}+1}{\sqrt{\frac{Z_a}{Z_b}}-1}\right]$$

Wikipedia also says that "In the context of two-port networks and their cascades, propagation constant measures the change undergone by the source quantity as it propagates from one port to the next."

This definition is not particularly clear to me. What is meant by "source quantity"? As far as I know, for a two-port network, we can give a certain input current and a certain input voltage at one port and get an output current and output voltage at another port i.e. the output port. By change undergone by the source quantity, do they mean something like \$V_{\text{out}}-V_{\text{in}}\$ or \$I_{\text{out}}-I_{\text{in}}\$ or \$\frac{V_{\text{out}}-V_{\text{in}}}{V_{\text{in}}}\$ or \$\frac{I_{\text{out}}-I_{\text{in}}}{I_{\text{in}}}\$? The word "change" seems really vague to me.


texts:
What will be the gain of circuit
1) We dont include channel length modulation?
2) we include channel length modulation?
If we include channel length modulation  will the gain be 1? as vds should remain constant as current source is ideal so increase in vg should have increase in vs and same increase in vd? Moreover why we bias at constant current then if vgs cannot be changed? How will gmvgs current increment gets generated?


texts: Need help to find replacement for power mosfet IRF7303

texts:
I have to design a voltage regulator circuit using DC-DC controller MAX1655.
Required voltage output from the circuit is 3.3V at 2A (circuit is shown at page 10 of datasheet).

According to the datasheet for MAX1655 (at page no- 11) i have to use IRF7303 or NDS8936 as mosfet in the circuit.

After looking up on the internet i found that NDS8936 is obsolete/not manufactured anymore.But i am unable to confirm whether IRF7303 is locally available at my place.

Questions:
1)I would like to know if any functionally equivalent mosfet for IRF7303 exists so that i can use in this circuit(for output 3.3V at 2A)?

2)Does the complete  circuit using DC-DC controller MAX1655 work as a voltage regulator(Can it handle changes in input voltage)?


texts: Difference between reading data from fifo and the register

texts:
I am currently working on a hardware design as a part of my project in verilog.
I am fully aware that we usually use the registers to break the datapath which in turn helps us achieve timing closure. However I am not really sure if reading data from the fifo has the same effect.

So basically if I am reading data directly from the fifo and sending it some other module, do I need to register the data to break the datapath or fifo will take care of this ?

Thanks.


texts:
I had bought a couple of ESP8266-01 chips a while ago and decided to use them.

I just found out that they only have 2 pins for GPIO, and I'll need more for a project.

I was thinking, is it possible to extend the GPIO so I can get at least 6 pins or more? A friend recommended me to buy a CD74HC4067 Digital/Analog Multiplexer, but I'm not sure if it'll work, so I prefer to not take the risk.

If it works, how can I hook it into my ESP8266?


texts:
I was wondering if it would be smart to control a power H-bridge, with light. Imagine an opto-isolated power stage, where the opto-isolators are sawed in 2 parts connected by an optic fiber.

I think it would avoid close proximity of potentials we would like to avoid radiating into each other (and long electric cables). The idea sounds quite simple, but my googling didn't turn any ready made components (it might be a keyword problem), like finding an array of pin diodes with integrated optical connectors, or a complete readymade optical gate driver (laziness is good right?).


texts: Do buck converters/voltage regulators change max amperage?

texts:
I'm interested in dc-dc buck converters and voltage regulators. I want to know if the maximum amperage changes when you adjust voltage or if amperage is affected at all when changing voltage.

Thanks


texts: Logic circuit equivalent of modulo function with fixed-size inputs and output?

texts:
Let \$q\$ be a \$Q\$ bit integer (with bits \$q_1 q_2, ..., q_\text{Q}\$)

Let \$p\$ be a \$P\$-bit integer (with bits \$p_1, p_2, ..., p_\text{P}\$)

\$Q > P\$ and \$q > p\$

Given \$P\$ and \$Q\$, how would one go about implementing a logic gate circuit to calculate the bits \$[r_1, r_2, ..., r_\text{P}]\$ of \$r = q\mod p\$ ? i.e. what is the circuit-equivalent function with \$P+Q\$ binary inputs and \$P\$ binary outputs, i.e

$$[r_1, r_2, ..., r_P] \leftarrow \text{moduloCircuit} \left([q_1, q_2, ..., q_Q], [p_1, p_2, ..., p_P]\right) $$

Does the circuit exist? If not, why not?

Note: We know that \$r\$ is going to have at most \$P\$ bits because the modulo forces \$r < p\$.


texts:
I'm trying to find which diode in a charger is bad. I took the 1N5819 diode out of the electronics board and tested it with my multi-meter set to "diode".
What I got was 0000 in both directions. Shouldn't this diode (or any diode for that matter) only give a reading in one direction?
Does getting 0000 reading mean that this diode is bad?
What should the reading be?


texts: FPGA boards with high clock speeds (hundreds of MHz)?

texts: It appears that most FPGA boards, such as the Mojo and Papilio, have built-in clocks on the order of 50 MHz, even though the FPGA chips themselves can go up to several hundred MHz. However, I need to be able to control another device with a signal on the order of 150 MHz. Are there FPGA boards that might be suitable?


texts: Desoldered Resistors on rotary encoder breakout can I just short them togather

texts:
Someone gave me this rotary encoder breakout, but they unsoldered the SMT resistors for some other project. Now I don't have any SMT resistors on hand and can't justify buying a roll of them. So would it be all right if I just shorted those pads together?

I know that this rotary encoder came from sunfounder and that the resistors were 10K. Based on the PCB layout I can't tell if they were essential or not.

In the picture, above I drew where the traces go as far as I can go. The main reason I'm asking is they appear to connect across the traces.


texts:
I like to build a laser pointer driver circuit that I can drive from an 8 bit uC. However, I like to get light output fairly constant. This requires for me to look at the photo detector (these lasers come with 3 pins, gnd, laser cathode, pd cathode) current and adjust laser input current to stabilize light output.

Ideally, I need to drive this from a GPIO of 8bit uC so that I can make it oscillate at different frequencies at different times. (100-300Khz range nothing very fast) I looked around and the analog circuits that are available are for DC, I couldn't come up with a way to drive them from GPIO.

I want to ask masters here, is there a way to do this with a few transistors etc. if not, what type of ICs I can use for this purpose. (A simple current driver with some feedback perhaps?)


texts: Question about mixing battery sizes and quantities

texts:
Ok. I have searched everywhere and can't find a definite answer on this:
My first question, Is, Can you mix 2 lithium batteries of different sizes together? (Like mixing an 18650 lithium battery with a 3v coin cell lithium battery). would that be be damaging? What effects would it have?
My second question is if it would be ok to mix 4 lithium batteries of the same size and brand together. What about NiMh batteries? How many of the same brand and size of that battery type are ok to mix?


texts:
Consider the circuit below:

I'm assuming ideal diode model(\$V_{ON} = 0V\$). If \$V\$, \$A\$ and \$B\$ are all 5V, the diodes will be reversed biased and no current will flow through the circuit. Therefore, \$V_{OUT}\$ = 5V.

However, for either of the diodes, the voltages across them will be

\$V_{A} + V_{D} = V_{OUT}\$.

Since \$V_{A} = V_{OUT}\$, \$V_{D}\$ will 0. Since we're considering an ideal diode, wouldn't that mean that the diode is actually forward biased? What am I missing here?


texts: Timing/buffering issue with Digilent's EPP on Basys2?

texts:
I have a Digilent Basys2 FPGA, and I'm implementing the EPP interface described in http://www.digilentinc.com/Data/Products/ADEPT/DpimRef%20programmers%20manual.pdf.  This allows a program called Adept to send and receive bytes from an FPGA design over the USB cable.

After following those instructions I had something that seemed to work.  I could send bytes from Adept and they would be successfully displayed on the seven segment display.  Unfortunately, when I sent a 100 byte file to be stored in register array, only 83 bytes arrived.  (It's a bit tricky to debug in this situation, because there are only so many simple outputs on the FPGA, and using Adept to read the bytes back from the FPGA opens the possibility that it's the read implementation that's buggy.  I ended up adding the ability to step through the array showing each byte in turn.)

I've rewritten my implementation a few times and looked at other people's examples (they were mostly in VHDL) but still it's not reliable.  Some writes, even single bytes one at a time, are just not picked up by the design, though Adept does not report any error.

Update -- tried VHDL sample design

I've now managed to run the code and design here:  http://hamsterworks.co.nz/mediawiki/index.php/Digilent_EPP_Performance

It works, but a simple counter I added shows slightly more writes are performed than expected, in a few repeated tests I ran (reload the design, then send a file using Adept):

Expected    Got
  50        51 to 55
 100        105 to 108
 200        206 to 215

For the compiled C++ program from that tutorial, 1440000 = 0 (mod 256) bytes were sent, but the number written was 32 (mod 256) (I only have 8 LEDs!).  In another the numbers were 1430000 = 240 (mod 256) vs 253 (mod 256).

So I still think there's a timing thing going on.  Can anyone with a Basys 2 try the same experiment?  My slightly altered VHDL is at https://gist.github.com/ejrh/6ba768499319e9945bd0

Small testcase from before I learned VHDL

I ended up with a small test case for EPP's WRITE signal:

input wire usb_write;  // in constraints file: NET "usb_write" LOC = "C2";
reg prev_write = 1;    // assume initially high
reg [9:0] write_count = 0;

always @(posedge mclk) begin
    if (usb_write != prev_write) begin
        write_count <= write_count + 1;
    end
    prev_write <= usb_write;
end

// display write_count on SSD
// display prev_write on LED 0

Usually when I send a byte using adept, write_count is incremented by 2, as expected.  (WRITE goes low to write an address byte and a data byte, then returns to high).  The LED stays lit between operations, indicating that prev_write is high.

But sometimes, the count is only incremented by 1, while the led still returns to high.  It's as if different parts of my always @(posedge mclk) block were using different values of usb_write.

Is there some kind of buffering I need to do on these input/output wires?  I haven't found any examples for this.

Later today I'll update the question with some of the actual EPP code I'm working with.  I also mean to try one of the VHDL examples, though I'm new to VHDL.


texts: 230V AC Wave forms in an analog ocillocope

texts:
I was doing a project on AC Phase control using triac,and I needed to see the phase controlled waveforms in a scope.But the scope that I am using has maximum volts/div as 5V (found on many scopes as well), which means I can get about 25V peak to peak (there are a total of 10 division of units on screen) peak to peak voltage wave on the scope.

Is there any way to see the 230V 50Hz AC and it's phase controlled waves in a scope?
If not what is the normal procedure to observe the AC(more than 25V peak) outputs of power electronics circuits in scope?

P.S. Max peak voltage at channel input of scope is written as 400V.


texts:
I want to solve the following inrush current (DC):

There is a switch, which will be closed at time t_0. So that I can redraw the graph.

I want to calculate something like that Example. But I do not know, how to set up the equations. for R_3 and L. Does anybody can give me a hint?


texts: PCB antenna track and SMA connector controlled impedance

texts:
I designed a pcb for GSM module, using all the specifications given by the manufacturer, to have a controlled impedance. But there is a small detail that escapes me and that is not documented. When the trace of the antenna arrives at the SMA connector, should the ground plane be opened or should I continue to keep a distance as for the whole trace? Some manufacturers, with the same module, open the ground plane to the maximum, others keep it constant.
What is the correct solution?
I add a photo to explain better.
Thank you all and sorry for my english


texts:
Under the following tutorial:

http://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/biasing-techniques-bjt/

They explain push pull operation. But should't negative terminal be separate with the ground? Dont we need +Vcc and -Vcc

Here is the push-pull from the tutorial:

EDIT: here is my simulation:

Green is input, red is output.


texts: I am working with a bluetooth audio circuit. I am facing noise problems in the mic input so I used B0505S DC DC isolated module. It worked but now when I printed a PCB of the same circuit and I am using it I am getting the noise problem again. Now when I power my circuit from the laptop USB port there is no noise problem in the mic input but when I power it from a battery I am getting noise problem again. It is really strange that when the supply is from USB port of the laptop there is no noise but when I connect a battery to power he circuit I get lot of humming noise. The bluetooth is getting its power from the 3.3vout of the LDO from Teensy arduino board. I read online that someone used a REG711 switching regulator Switched-Cap DC/DC Converter because when he used it his noise problem went away. I tried to power my circuit through a stepup regulator Polulu 3.3V step up voltage regulator but still there is the same noise problem. I read online that using LDO also might not be a good option. Please let me know what should I do?


texts:
I have drawn a schematic for a simple LED-driver.
It is nothing special, but how can I try circuit out?
Some parts are only available in SMD.
So my idea is that some one looks it over before I send it to the manufacturer.
With the MOSFETs in SMD, how big must be the thermal pad of each MOSFET be if it must handle 5 amperes? The final MOSFET is an IRLZ44ZSTRLPBF.


texts:
I'm shopping for some AC relays to hook up a thermostat to a bar fridge for my homebrew setup (I like beer).

I've come across some suspiciously cheap items on eBay, like this this one. Normally when it comes to cheap electronics I'm willing to give it a crack but since I'm going to be passing 240v through it I'm a little bit more skeptical.

Having said that, I know nothing about the internals of relays or their failure modes. What is the risk here? Could it,

Just stop working, or
Burn the house down?


texts: How to make cables for 0.1 in. pitch pins?

texts:
I'm trying to make a cable for a 4 wire interface to a stepper.
The intention is to have a short cable attached to the stepper, a male piece on the PCB board, and a bridging cable that can be replaced for different lengths.

I was thinking of connecting the stepper cables to a female piece, then making a cable with female and male on each end. Then the PCB board will have a male piece.

So far, I've only noticed these headers fit the description. So I was wondering, is it normal to use these kinds of headers to solder wire, and make a cable for PCBs with 0.1 in. pitch?
then connect the other side with one of its mating parts?


texts: Does battery voltage actually get lower when connected to a load, or does it just appear to do so?

texts: Sorry if Im wording this question strangely. I am using a 3.7V battery and my microcontroller monitors the voltage and goes to sleep if my battery voltage is too low. The issue is that it reads a lower voltage than the battery shows if I disconnect it and check it with my multimeter. For example, my microcontroller would read 3.65V when my multimeter would read my disconnected battery at 3.8V. Is my microcontroller reading the voltage incorrectly or should I treat the with-load voltage that my microcontroller is readings as the actual voltage?


texts: Is there a wrong way to wire a potentiometer?

texts:
I'm using Circuit Wizard to simulate a circuit and I'm trying to understand how to wire a potentiometer.

While trying to learn how current flows through the pot, I found that it works in both directions as it's just a variable resistor. But when drawing a schematic, which is the RIGHT way that current should flow through the component?

See the following two schematics:

I have the following questions:

Is current supposed to flow in the direction of the arrow or away from it?
Is it unusual to wire a potentiometer what appears to be reverse as I've done here?
Is there any problem with not using the third lead in this circuit?


texts: Needed PCB surface to cool a SOIC-8 EP package

texts:
I have got a part in a SOIC-8 EP package. The "EP" indicates it is a package with a exposed pad which can transfer heat to the PCB. I would like to have a better understanding how much pcb surface I need to cool the part at different power consumption levels. Lets say 1 Watt 1/2 Watt and 0.1 Watt.

I did read some white papers. They basically tell:

PD = (TJ − T A)/θJA

Where
θJA = theta ja (junction to ambient) in C/W
TJ = junction temperature rating in C
T A = ambient temperature in C
PD = power dissipated in watts

θJA can be split into three parts which add up:

θJA = θJC + θCS + θSA

Where:
θJC = theta JC (junction to case)  °C/W
θCS = theta CS (case to heatsink)  °C/W
θSA = theta SA (heatsink to ambient)  °C/W

The datasheet of the part tels me:
θJC = 10 °C/W
TJ  = 150 °C

I can think of a ambient temperature lets say 22°C

But then I am still missing the following: θCS and θSA. I could imagine that θCS is negligible, is this true? θSA I find difficult I plan to use via's to get the heat to the other side of the PCB but I can not find any data giving me a idea what number I can use for θSA. I also find it hard to figure out if I need 35um (1oz) or 70um (2oz) PCB.


texts: I've been looking into converting a MIFARE (Oyster card) into a ring. I found this NFC ring on kickstarter, will that work as an Oyster card? Or are they different technologies?


texts: Use high-speed optocoupler with slow input signal

texts: As known, a slow input is usually not good for CMOS digital circuit design. I wonder, if the high-speed optocouplers such as 6N137, HCPL-060L, etc, can be used with slow input signals, such as to detect a zero-crossing event in a 50Hz AC input? (I know it's a waste of money to use high speed with slow input, but that's another question.) What I should take care of? Do I need a signal conditioning before the optocoupler?


texts: GSM/3G SoC reverse engineering for GSM/3G Layer1/2 PacketAnalyzer

texts:
I want to develop a GSM/3G Packet Analyzer for study purposes, a somewhat more simplified version of OsmocomBB but without any TX modules.

As some of you may know, even though OsmocomBB is open source, it has not been ported but to some very old Motorola and Sony-Ericsson phones. I would love to be able to do something like OsmocomBB on a newer phone so I can link it with a modern android OS system like Cyanogen.

I've read that Broadcom is one of open-sources Gsm baseband processor manufacturers out there, so - sorry if I have passed some of the information accumulated over here.

Is there any way I can find any open source RTOS (Real Time Operating System) that is compatible with say Broadcom's BCM28155 so I can modify it and be able to read all GSM/3G stack and transfer this layer 1/2 data to android OS? And also be able to re-flash the BCM with a high success rate?

If not, what would be a starting documentation on reverse engineering SoC (System on Chip) chips developed by the main main GSM baseband chip manufacturers so I can start from there. Maybe some books that delve into this specific issues?


texts: Can I convert usb-male device to usb-female pluggable device?

texts:
I have an external audio card, it's small and it has usb-a male to plug it anywhere, well anywhere you have usb-female of course :)
I've been using it on the few mobile phones I have. (some are on micro-usb, some are on usb-c. some are on apple lighting)
Now the way I get it to work is always using that phone adapter cable that is pluggable to mobile device and has ucb-a female adapter on the other side. I have 3 of them.. one for apple, one for usb-c, and one for micro-usb.

I tend to lose them around the house all the time so I thought.. What if I resolder the usb-male on the card to USB-female so I can always plug it with either of the charging/data cables, which I always seem to have laying around. Basically I'd love to convert that usb-male to something more like that..

I tried a few usb2usb (both female ends) adapters but they don't seem to work. I tried to resolder the usb jack to the female and followed the order all well and even tried it reverse but neither of the phones seem to detect the device this way.
Does anyone know what is missing?
I'm thinking my next try would be to resolder that usb-male to usb-c female, maybe this way it will work but other than that I'm clueless
Thanks in advance!!


texts: Switching 3 different voltages with one input

texts:
I have a VU meter project I am working on using an LM3916 chip and a series of 4 RGB LED's.  Each set of colors is varied in intensity by varying the voltage from ~0-15V.  Each set of colors draws about 30mA so when all are fully illuminated it exceeds the maximum rating for the LM3916.

So I need to come up with a "relay" of some sort that can be triggered by 12 or 15 volts (preferably) and light up all three colors of LED's each with their independent voltages.  For instance R=3.5V G=12V B=15v - but they should all come on at the same time when the "relay" is triggered.

The easy solution is 3 solid state relays - one for each color - but as there are 10 segments of 3 LED's I would need 30 SSRs which is just too expensive (not to mention needing a second 30 for stereo).

My second thought was transistors but I'm not sure how to get them to work correctly -  especially with varying voltages.

What I'd like is a SSR with one input but three isolated outputs but such a thing seems not to exist.  Ideally I could find a single chip with 10 inputs and 30 outputs but again I can't find anything.

Thoughts?

Thanks!


texts:
I'm building a signal generator for my electronics project, and to generate the triangle wave, we're required to use a relaxation oscillator (we can add other circuits around it to improve the quality, but the minimum is to use the relaxation oscillator).

\$R\$ is a pot (\$8\Omega\$ to \$51k\Omega \$),

\$R_1 = 1k\Omega\$,

\$R_2 =23k\Omega\$

\$C\$ is selected using a dip switch depending on the desired frequenecy range:

\$6.8\mu F \$ for 18Hz to 1.1kHz
\$0.1\mu F \$ for 1.2Hz to 61kHz
\$27 nF \$ for 4.5kHz to 200kHz

Op-amp : Data sheet

Supply voltage : \$\pm 15 \ V \$

2x Electrolytic decoupling capacitors : \$100\mu F \$

At low frequencies, the oscillator produces a very nice triangle wave, but at higher frequencies, there's noise that appears at the peaks.

Anyone know what could be causing this, and what I could add to clean it up?

We're not allowed any dedicated ICs, except for Op-amps.


texts:
The application that I want to use it for is 5V. However it could potentially have a future iteration where the reference voltage could be as high as 15V.

The plan is to run the ATmega48 at 3.3V.

I have been researching for what the maximum AREF reference voltage could be and it appears that it is 5.5VDC or so. Am I understanding this correctly? I would prefer to not have to use voltage dividers so that my voltage levels are exact and I do not lose precision in resistor tolerances. Am I over thinking this? The reason why I am worried about this is that I am looking at the input voltage and output voltage of mosfet transistors and knowing the Rdson value of the resistor then calculating the current flowing through the transistor.

If this is the case, then I will plan on just using voltage dividers on my pcb so that I can switch out resistor values to be able to use AREF values from 15V to 5V and not need a pcb change.

What AREF voltage input level should I design to?


texts: How accurate is a DC fuse's voltage rating?

texts:
I understand that a DC fuse's voltage rating is determined by the possibility of a connection-sustaining plasma arc. However, unlike the current rating, which is based on the very well understood principles of resistive heating, the voltage rating is based on the likelihood of plasma creation, and this seems to be much more stochastic. I expect that as a result, the current rating is very precise, but in contrast the voltage rating is very conservative.
I'm interested in how much excess voltage is actually required in typical circumstances to see plasma arcing. I'd also like to know what factors affect the likelihood of plasma creation, and how do they play into the fuse's real-world behavior.
UPDATE: Another way to phrase this is that I'm looking for an understanding of DC fuses' design safety factor and how environmental factors affect the real-world safety margin.


texts: Tradeoffs when choosing the op-amp package: quad vs dual vs single

texts:
Let's say as an example that I need to use four op-amps in my project. I don't have any super strict requirement of space and price.

Which are the parameters to take into account when choosing the package to use, beside the space occupied on the board and the total price?
What are the tradeoffs, and what are the differences in using two dual packages or even four different single packages instead of using a quad package?

Thanks in advance for every answer.


texts: Distributing a 40MHz clock to several PCBs

texts:
I need to run four PCBs with a very accurately synchronised clock.

The source clock is 40MHz, but each PCB contains a 1GHz PLL, and will be timing events in the analogue domain with a final resolution of about 15ps! I will be measuring the difference in event time between the four boards.

I will be using a 1.5ppm source clock, which is enough stability.
Any difference in cable length can be calibrated out.
What I can't cope with is any change in clock skew over time between boards, because I can't for calibrate this.

I can think of two ways to transmit the clock to the four PCBs.

Use a clock buffer to drive the clock into four coaxial cables. This will surely rule out any change in clock skew over time, but perhaps the clock won't have enough drive to inject into 4x 50R lines. An ultra-low skew quad clock buffer chip, like the NB3N551 lists an output impedance of 20R, which is greater than the 12.5R of the cables.
Use four clock buffers, which will have enough drive, but can the buffer-buffer skew change with time? The NB3N551 lists an output-output skew of typically 50ps and max 160ps. But it doesn't explicitly state the stability of that skew.

Is there anything which rules out one of these two solutions? Which is the best approach for achieving ultra low skew drift?

If I used method 2, would it be better to use series termination instead?


texts: Can anyone identify this two pin locking plastic low voltage plug and socket?

texts:
This is a plug/socket from a reset button on a gas heater. I need to extend the cable because it requires the heater facia to be removed to access it, so I wanted to create a new plug/socket to add an additional extension button.

The only problem is I have no clue what kind of plug/socket/connector it is. I originally thought Molex, however this doesn't appear to be the case as the pins are not shielded on the plug side. It seems to be more JST style, but my google-fu is lacking right now with this one.

Any suggestions would be appreciated. I guess if I cannot find what kind it is I could always replace the original plug/socket, but I'd rather avoid changing the OEM parts or splicing into the wires destructively.

Thanks!


texts: Miniature flow sensor for detecting breath movement

texts:
I've been looking around for a sensor that is capable of detecting the presence of a person's breath. It needs to fit inside a tube that a person will blow on. Detecting the force of the person's breath is not important at all, I just want to detect movement of air caused by someone blowing on the tube.

Is there a sensor that can help with this that will run on a 3.3V circuit? I can't seem to find something online, that's small enough to fit inside a tube around just below 1" in diameter.

Any recommendations. I've been searching catalogs for our local vendors till I'm blue in the face, but just can't seem to find something suitable.


texts: Unexpected drill hole behind voltage regulator in EAGLE

texts: I am designing a PCB in EAGLE and I want to use an 7815 TO-220 voltage regulator. When I check the top or bottom layer mask of my PCB I can see that there is a hole (with no copper I think) behind the voltage regulator. Is this normal or I am using the wrong model?


texts: I'm doing a little university project in which I'm projecting a small PV plant of 50 kW. When I produce more power than my load need, I want to store the solar power inside the battery. Should I consider both the efficiency of the inverter and of the battery in order to calculate the net power stored?


texts: How to reduce the current of a battery with an unknown maximum amperage

texts:
I'm currently trying to heat a wire to a certain temperature and tests showed that the amperage needed is in the range of 3-4 A.

However, I'm having a problem with how to supply such current to the wire.

I have an Arduino Nano with a max current of 40mA, and a weird battery with 7.4V and 1000mAh. I'm not sure how the battery works but directly connecting it to the wire instantly snaps it, so I need to limit the current somehow.

I was trying to make a simple circuit with a resistance and a transistor (as a switch. Maybe a SS Relay instead?) but when I was browsing for transistors they all limit the Collector current and I'm not sure how much the battery will give. The resistances available to me will fry instantly with a simple 1A current.

I'm not sure what to do, I'm seriously considering buying a new battery, but that comes at a cost.

Maybe I'm just dumb and it isn't possible with this battery

Tl;Dr: Have a battery with "unlimited" current that will fry everything that I have. Need to reduce it while keeping a ~4A current


texts: Techniques for measuring the ripple current of SMD electrolytic capacitors

texts:
I am currently creating a test plan for an AC/DC converter (90VAC...264VAC -> 12VDC) I've been working on. Since the output electrolytic capacitors are of SMD type, I am trying to come up with possible solutions for reliably and safely measuring the ripple current through them, in order to estimate the lifetime of the power supply.
Preferably, it would have to be scalable because the measurement will be carried out inside of a temperature chamber as well.

Any ideas how it could be accomplished?


texts:
I ordered some graphene off ebay to test on some applications and I am unable to get continuity.

I applied a layer of graphene on some two sided tape, made sure the adhesive was completely covered, then removed the excess with cello tape.

Is there something else you're supposed do to graphene in order to get continuity response?  Or did I get fake/contaminated graphene?


texts: I have a Baldor DG6E generator.  It must produce 120V/240V but I bought it and it has three wires as outlets - every one produces 120V.  I want to combine two wires to produce 240V. How can I combine two wires to produce 240V or is there is another way to make the generator produce 120V/240V?


texts: Acceptable designing two clock generators using single package?

texts:
The circuit I usually use is Pierce oscillator:

(pic source)

I have always had single system clock in the system, built on single HCU04 chip. Now I need two: 6*NTSC and 4*PAL - frequencies not related to each other. It is possible to build both using 6-gate HCU04 chip.

I have 3-rd party design, which has its NTSC clock (3.579545 MHz) passing through the 74LS04 chip, with its other gates used for "less intensive" purposes. I was astonished to see all other gates picking up considerable noise of the NTSC carrier, with ground pin of this chip being also affected by this frequency. Noise was easily seen on the scope, and propagated down the circuits.

I can not find definite discussion or answer for the phenomenon (probably because it is simple and assumed):

building two clock circuits on single chip will save money and probably space on the board, but gates may suffer from crosstalk through internal power connections within the chip;
building two clock circuits on a number of chips (e.g. 4 chips 1G each) will minimize crosstalk, I will be able to put decoupling on each chip and optimize their power connection, but it will cost more in terms of components and board space.

Do I understand the situation properly? Is it really beneficial to not use single chip for two generators? What is the best practice in various conditions?


texts: How to find the dynamic energy of a processor without using capacitive load?

texts:
I have the following question:

A cell phone performs very different tasks, including streaming music,
streaming video, and reading email. These tasks perform very different
computing tasks. Battery life and overheating are two common problems
for cell phones, so reducing power and energy consumption are
critical. In this problem, we consider what to do when the user is not
using the phone to its full computing capacity. For these problems, we
will evaluate an unrealistic scenario in which the cell phone has no
specialized processing units. Instead, it has a quad-core,
general purpose processing unit. Each core uses 0.5 W at full use. For
email-related tasks, the quad-core is 8 as fast as necessary.
a. How much dynamic energy and power are required compared to
running at full power? First, suppose that the quad-core operates for
1/8 of the time and is idle for the rest of the time. That is, the
clock is disabled for 7/8 of the time, with no leakage occurring
during that time. Compare total dynamic energy as well as dynamic
power while the core is running.
b. How much dynamic energy and power are required using frequency and voltage scaling? Assume frequency and voltage are both reduced to 1/8 the entire time.

Now for part a. I did the the following which I think might be right:
I divided the new dynamic energy and power by the new ones so I did [1/2xcapacitive-loadxvoltage^2x1/8]/ [1/2xcapacitive-loadxvoltage^2] which gives me 1/8 so the new dynamic energy is 1/8 the old one.
However, for part b I did (for dynamic power) the dynamic power is proportional to: capacitive-load(1/8)^2x1/8x1/2=capacitive-loadx1/1024
So my final answer was in terms of the capacitive load, how can I get a final answer that is just a number representing the dynamic energy?


texts: Bad Reflection from SMA Board Connector at 4-8 GHz

texts:
recently I have tried to design a simple SMA-to-microstrip connector PCB intended for 4-8 GHz. The connectors used are vertical with surface-mounted centerpin (link).
The design idea was to simulate the connector and the transition to the microstrip on the board in CST Microwave Studio and match the transition by finding the best size of a cutout in the groundplane below the point where the center pin meets the microstrip, see pictures (click for higher resolution).

Within the simulation this approach works well, a solution with S11 < -25dB from 4-8 GHz is easily found.
Single connector:

Full board (connector - microstrip - connector) sims with acceptable S11 around -20dB:

So I had a prototype manufactured on 200um FR4 dielectric, the thought being that the S21 losses would be large, but evaluation of the S11 performance should give an idea of how well the design works out in reality.
Sadly the measured reflection is horrible, around -13dB at the worst point:

My questions are now:

Can I expect a better agreement of simulation and the manufactured board by using a proper HF material instead of FR4?
Did I do some rookie mistake somewhere?
Or is this high reflection just unavoidable with these type of right angle connectors? Its surprisingly hard to find any reliable data on this.


texts: Switching power supply toroidal heats more than 100ºC. Is it normal?

texts:
I’ve got this 48V 10.4A generic chinese switching power supply to power my mini lathe’s controller and stepper motors.

The two steppers draw when working just 1.5A max each. And the controller 0.5A.

This supply turns on its loud fan a couple of minutes after it’s on and never turns the fan off, even if the steppers/controller are in standby mode.

The supply’s vendor told me the fan is not temperature aware, so it stays on forever.

I wired a small temperature control circuit to turn the fan cooler on and off depending on the temperatures inside the supply.

But I noticed that the more it stays on, and when powering actively the steppers, this toroidal coil (don’t know its proper name) heats a lot. It slowly got to almost 120º C. In the picture I attached a temp sensor to this coil, to turn on and off the cooler.

But with a laser thermometer, i checked the temps of most components and nothing ever reached 50ºC, but this coil gets too hot.

The supply works normally, outputs it’s 48V properly, the lathe works normally.

Is it normal for this component get so hot?? Is there anything I can do to fix it?

Thanks for reading]1

The output choke measures 40mm diameter, aprox. 23 mm width, the hole measures 12mm aprox. The wire is 1mm thick and appears to be three wires wired in parallel.
It’s green core is not one whole unit, but two half width kept together by the wiring.


texts: I came across this decoupling capacitor arrangement on the evaluation board for the AD5791.  It decouples the IC AD8676 with 10 caps!  I suspect its related to the AD8676 driving the reference inputs and thus requiring significant changes in current draw as new values are set on the AD5791 DAC.  However, it seems like a bit of overkill to me and I'm just wondering will I see any significant performance difference between this setup and an alternative with just a 0.1 and 10 uF on each power rail to GND?  If the answer is that the extra caps will help in this situation, then what is the optimal placement of the capacitors C28,29 in this diagram between the two voltage rails?


texts: Implication of \$s \to \infty\$ in a transfer function

texts: For a strictly proper transfer function with no poles/zeros at infinity, I understand that it gives \$G(\infty) = 0\$. What does it do for a proper transfer function?


texts:
I am trying to use LM317T as a current regulator and the setup is from its data sheet. I couldn't get it to work.

I want a constant output current of 10uA when input voltage is changed from 3V to 2V. Since the internal reference voltage between output and adj is 1.25V, I put a resistors of 125kohm from adj to output.

I am getting very high currents like 3mA and I can't figure out why. I appreciate all your help.

simulate this circuit – Schematic created using CircuitLab


texts: Audio hack: replacing electret mic with phone audio output

texts:
I'd like to feed a module with audio output from a phone's jack instead of the mic the board cames with.

As I said the board is designed to operate with an electret mic with the following specs:

Sensitivity -38dB
Load Impedance 2.2K
Operating Voltage 3V

The schematics:

The mic produces a signal that is 20mV peak-to-peak, centered around 1.5V, but anything in the [0.5V,2.5V] range should do according to the manufacturer.

I want to take out the mic and instead connect a phone's audio jack to the module.

I have two questions:

Are audio jack signals standard? What would be a normal signal coming out from an standard smartphone?
Assuming an average phone,  what would be the minimum required circuit able to convert (most likely attenuate?) the audio jack output to the above mentioned levels?

Thanks.


texts: Transient voltage noise in 240 V AC mains detection circuit MSP430FR2311 gets RESET

texts:
I am detecting 240 V AC mains using optocoupler. Here is my circuit.

When I am doing this my microcontroller resets every time I on/off the 230V AC circuit.
I've seen response of the on & off switch in oscilloscope. It is looking like below image

Because of this transient my controller gets reset as the same transient is being seen in the reset pin and power pin of the controller.

Can anyone help with how to reduce this transient. I've tried low pass filter at output side by adding 330Ohm resistor with 10uF capacitor. Did not worked.

I've tried same thing with Arduino ATmega328P which does not reset with same transient.

Any help would be appreciated


texts: ploting the recombination rate in a forward bias depletion

texts:
I'm trying to figure out how to plot the graph in b.
I know I need to go according to the recombination formula in a, and Ei is linear, but for some reason something won't work.

is there anyone who can help me out with this?

by the way, I have solved a, but it would help to see if I got it right.

Thanks!

about part b : I think the fuction looks something like f(x) I worte here, and after plugging in the values the ends of the depletion I've gotten the this plot.
does anyone know if I'm on the right path here?


texts:
This is the output of both track and hold and sample and hold.

But when I searched for its circuit I am getting the circuit I have shown below for both. So my question is if the circuit for sample and hold and track and hold are the same then how is the difference between the two getting reflected in the circuit? Is the control signal input different for both and if it is, then how is it different?


texts: PIC: UART transmit corrupted after watchdog sleep

texts:
I have a PIC16 (datasheet here) for which UART transmit works, except right after a watchdog sleep, where the first few characters are corrupted.

I have posted my reduced code below. What could cause corruption of the first few UART transmit characters right after a watchdog sleep?

// Baud rates
#define BAUD_115200 0
#define BAUD_9600 1

// Watchdog sleep times
#define WATCHDOG_SLEEP_4S 0b01100

/* Note: The watchdog operating mode configuration is done in configuration word 1 */
void watchdog_configure(char interval) {
    // Configure the watchdog interval (e.g. 10010 for 256 seconds)
    WDTCONbits.WDTPS = interval & 0b11111;
}

void watchdog_sleep(void) {
    WDTCONbits.SWDTEN = 0b1;
    SLEEP();
    WDTCONbits.SWDTEN = 0b0;
}

void UART_setBaudRate(const unsigned char type) {
    // See table 25-5
    if(type == BAUD_115200) {
        SPBRG = 68;
    } else {
        SPBRGH = (832 >> 8);
        SPBRGL = 832 & 0b11111111;
    }
}

/* Configure the UART for full-duplex asynchronous transmission */
void UART_initialise(void) {
    UART_setBaudRate(BAUD_115200);

    // Configure the RX/DT pin as an input
    TRISCbits.TRISC4 = 0b1;

    // Enable the asynchronous transceiver
    TXSTAbits.TXEN = 0b1;
    TXSTAbits.SYNC = 0b0;
    RCSTAbits.SPEN = 0b1;
    RCSTAbits.CREN = 0b1;
    TXSTAbits.BRGH = 0b1;

    // Use 16 bits for the baud rate
    BAUDCONbits.BRG16 = 0b1;
}

void UART_write(const unsigned char character) {
    // Wait while the transmit shift register empties
    while(!PIR1bits.TXIF) {}

    // Indicate the character to be written to the Transmit Shift Register
    TXREG = character;

    // Add a one cycle delay to ensure that the TXIF flag is valid
    _delay(1);
}

void UART_writeString(const unsigned char *string) {
    unsigned char i = 0;

    while(*(string + i) != '\0') {
        UART_write(*(string + i));
        i += 1;
    }
}

void main(void) {
    // Perform initialisations
    watchdog_configure(WATCHDOG_SLEEP_4S);
    UART_initialise();

    watchdog_sleep();
    UART_writeString("UART TESTING");
}


texts: Dual tracking PSU: how to derive set voltage for second "half"?

texts:
I'm fiddling aroud trying to design a dual tracking PSU, based on the LT3080-based design by eevblog/Dave Jones. The general idea is to use a microcontroller obtain \$V_{set}\$ in the range of 0-2V, and then amplify it with an opamp, and use this as set input to the LT3080. Source power is provided by a simple 24V SMPS, and we get a regulated \$V^+\$/\$V^-\$.
I am trying to extend this design with a second, tracking, power supply. So, get a second 24V SMPS, and a second LT3080, and we get an additional output. Let's call these \$V_2^+\$ and \$V_2^-\$, and the outputs of the first half \$V_1^+\$ and \$V_1^-\$. To get parallel tracking is fairly easy I think: tie \$V_1^-\$ and \$V_2^-\$ together, and use an opamp to buffer \$V_{set}\$ and use the same architecture to scale it using an opamp.
Where I am struggling is how to switch this configuration to series tracking. The first step is to now tie \$V_1^-\$ and \$V_2^+\$ together. To get the correct set input for the second LT3080, we now need to invert \$V_{set}\$ relative to \$V_2^+\$. This led me to the following inverting opamp configuration:

simulate this circuit – Schematic created using CircuitLab
On the face of it, this seems like it should work. However, \$V_{set}\$ will be higher than \$V_2^+\$, since this is tied to \$V_1^-\$. Will the opamp allow this, or will this lead to escaping magic smoke?


texts:
I'm going to try and generate black and white NTSC video, using a micro-controller. According to this:

https://instruct1.cit.cornell.edu/courses/ee476/video/

It is possible to do it using two pins of Atmel Mega644. I looked at the datasheet and noted that the IO is 1.8 V. For NTSC you just need three voltages sent at the correct time, 0V, 0.3V, and 1V.

What I don't understand is how does this circuit generate the 0, .3 and 1V. When I do the calculations it doesn't really add up.

I simulated this using TI TINA simulator, 2 batteries and switches inplace of the IO ports, and trying all four combinations of the IO, I can get 0, .3V but not 1V.

Can someone using math explain how you can get 0 V, .3 V, and 1 V using the circuit shown in the link above. I also, I guess what I don't understand is the uC IO equivalent circuit for simulating in a SPICE program, is it just a battery set to the IO voltage? Or maybe an OP AMP with the output set to the IO voltage can someone please explain this.

Any help is appreciated.


texts:
I am programming a PIC16F877a with 3 toggle switches and a 20 x 4 LCD. The 3 switches are soldered to pins B0 - B2 on the PIC. The other end of the switches is connected to +5v (PortsB have internal pull up resistors). I am programming using CCS and the problem I've met is that for some reason, ports B0 - B2 always read true and ignores the buttons. The problem might be a software issue so here's my program:

#include <16f877a.h>
#fuses XT,NOWDT,BROWNOUT,PUT,NOLVP
#use delay (crystal=4000000)

#include <Flex_LCD420.c>
#include <7segDisp.c>

#define btn_A PIN_B0
#define btn_B PIN_B1
#define btn_C PIN_B2

int i;
void main() {

   output_low(LCD_RW);

   lcd_init();
   printf(lcd_putc, "\fPress Any Button");
   while(1){
      if(input(btn_A) == 0 || input(btn_B) == 1 || input(btn_C) == 1) {
         break;
      }
   }
   printf(lcd_putc, "\fChecking Btns..A");
   while(1){
      if(input(btn_A) == 1) {
         break;
      }
   }
   printf(lcd_putc, "\fChecking Btns..B");
   while(1){
      if(input(btn_B) == 1) {
         break;
      }
   }
      printf(lcd_putc, "\fChecking Btns..C");
   while(1){
      if(input(btn_C) == 1) {
         break;
      }
   }
   printf(lcd_putc, "\f\nEnd Check");
   while(1);
}

I need help urgently as this is for a project that is due today.

Thanks in advance.


texts: Meaning of temperature coefficient for resistors

texts: Is temperature coefficient of a resistor about the temperature of the resistor or ambient temperature or are they the same thing? What I mean to ask is that: Lets say I have a resistor and I have no data sheet about it and I want to find the temperature coefficient. Can I use the ambient temperature in calculations? Is the resistor temperature same as the ambient temperature after a while or is that always much higher?


texts: Is it okay to connect 80 LEDs parallel or in series in pair of 10 LEDs per pair?

texts:
I'm working on a project with 80 WS2811 LEDs.  The power will be supplied by 12V 100W power supply.  The distance between every LED will be 1m and total circuit distance will be around 80m (80 Leds * 1 m (1 LED per meter)).  I am thinking to connect 80 LEDs in pair of 10 LEDs parallel or in series to overcome the Voltage drop problem and provide them power with an another external wire coming from the same power supply.

Will this work or there are some other cost effective ways?

LED Link: https://www.ebay.de/itm/100x-WS2811-RGB-Full-Color-Pixel-5050-LED-Module-Point-Light-16mm-20mm-26mm-30mm/202034762524

I am from a programming background so I do not have much knowledge about electronic stuff.

1) Parallel

2)Series


texts: What does zero voltage or negative current mean in H-bridges?

texts:
I have looked around in the internet, but could not understand what does zero voltage negative current or positive voltage negative current mean. All that confused my mind.

Can anybody explain shortly about all these operating modes?

Thanks in advance.

My thinking for respective modes:

i) positive voltage is when the voltage difference between the motor is in such way that voltage on the left(according to the picture) is higher than the voltage on the right of the motor. So Q1 and Q4 open.

ii) have no idea

iii) I don't know how voltage on the right can be higher than voltage on the left. (assuming my thinking was correct for part i)

iv) if voltage is positive, how current flows in negative way?

v) have no idea


texts: How can I make a decent ground plane in Eagle?

texts:
I've made a couple of simple PCBs as a hobbyist, and for the first time now I want to add a ground plane pour but I'm having some issues.

As I have currently understood I need to:

Create a polygon along the outline of my board with the polygon tool
Rename it to GND
Set a clearance
Turn on thermals for easier soldering
Click on ratsnest after manual/auto routing

The problem is that I'm getting empty spaces after doing an auto-route test and clicking ratsnest and the inner ground planes don't seem to be connected to the outer ones

Image:

What am I doing wrong?


texts:
I am currently using a MCP73831 to charge my Li-Ion battery. Once the battery is charged I can use a switch to turn on my circuit.

So right now : USB-B -> MCP -> Li-Ion -/-> Circuit.

It means that when my battery is charging, the rest of the circuit is turned off. What I'd like to do is to do both at the same time: charge the battery and power the circuit. So that when the USB cable is not connected, the circuit drains the battery. And when the USB cable is connected, the circuit is powered directly from the USB while the battery is charging.

Ideally I don't want to use any manual switch, so that everything is automatic.

I thought of two options that obviously don't work:

Removing the switch on the schematic above. But the battery would not be charged properly. (And I'm not even sure the circuit would work because of the battery charger behavior).
Using a parallel branch from the USB but it would short-circuit the battery charger. (Unless I keep the switch...)

Some technical details:

The supply voltage can be anywhere between 3.7v and 6V.
The switch between Battery supply and (USB supply + battery charging) should be automatic (Unlike on this schematic).


texts: Do I need buffer inverter for a Crystal Oscillator?

texts:
I want to be able to select between two clock signals, 16MHz and 1MHz, using an analog SPDT switch. Do I proceed correctly, by buffering these oscillators? Or is there a better way to do this?

The clock goes to the MCLK input of an AD5934, whose input capacitance I do not know, but I'm assuming it drives multiple circuitry inside the IC.

The analog switch has an input capacitance of 17.5pF, while the oscillators specify a maximum load of 15pF, that's why I assume a buffer is needed.

Is this the correct way to do such a clock switching?


texts: What standard plug and play connector is used for an STP cable in electronic instrumentation?

texts:
It seems to me that BNC connectors are only used for coaxial cables. These coaxial cables with BNC connectors are very practical when it comes to plug and play quickly.

But for a balanced signal chain STP cable is used not coaxial. But what equivalent connector is common in electronic instrumentation for STP(twisted shielded pair) cables. Is there a standard plug&play conventional connector for STP? (By plug and play I mean not screw terminal sort of thing but indeed a connector which is similar to BNC or a jack one can easily remove and plug in a second)


texts: can i interface profinet protocol to ethernet interface?

texts: i have a profinet device and an Ethernet port which is dedicated for KNX protocol. can i connect my profinet device to this Ethernet port?


texts:
Hey, electronics people:
A few months ago, I cleaned a spot on an LCD flat screen. Whatever it was, it was stuck on there pretty good and I guess I pushed down on it too hard (actually wasn't hard at all, to be honest). Anyway, next time I turned it on there was a huge blob of dead pixels in and above that spot. It's taken a few months, but the size of the blob has significantly reduced in size and continues to fade.

Here are two images taken less than 24 hours apart. It doesn't usually happen so quickly; I think it was just a lucky coincidence that I happened to take the first photo at the right time. It's still only marginally noticeable, but when it first happened (I'll try to find an older image) all three dead spots were all bridged together as one and the outside edge has gradually receded. First (if you look closely), they tend to go from black, to blue, to cyan (sometimes?), before fading back to normal.

Can anyone explain this? I actually expected the dead spot to do the opposite; slowly grow bigger until the display was rendered useless.


texts:
Good day guys. This is my first time posting, hope you can help me a bit with this.

My Sony Vaio laptop from 2009 has two damaged AO4433 MOSFETS near the power supply connector. I want to replace them, but I can't find this exact model in my city. I have an old laptop motherboard (for spare parts) that has some FDS6679 MOSFETS that I can use.

Can I replace the damaged AO4433 with the FDS6679?

Thank you very much in advance for your help.


texts: Safest way to trigger camera shutter using arduino

texts:
I'm working on a prototype where I'm controlling my DSLR using BLE module.

I found many tutorials to trigger shutter release using Arduino on the internet.

So far, I have found optocoupler to be the safest option.

Is there any Better than optocoupler ?

How does original intervalometers/remotes for Canon & Nikon work ? Even they use optocouplers ?

As I'm planning to release my prototype in the near future as product, I don't want to endup damaging users cameras.

Note : My board works on 3.0 V


texts:
I've been working on this TB6600 design (schematic shown here). Q1 ensures that the motor remains within the current limits. The TB6600 drives the ALERT pin low when the current limit is exceeded. Q2 and Q3 are for the torque control. IF there is a step of continous pulses the TQ pin is held high and hence maintain 100% torque. Current sense resistors are 5 x 1R 1W resistors. VCC is 24V and stepper resolution is set at 1/16.

However this does not seem to be working. The motor moves a little and stops.

Here is the code I'm using to test the motor (a NEMA 23 stepper motor rated at 2.8A). The code is supposed to drive the motor through 200 steps and hence make one full circle. However, that does not work. I also tried driving this with grbl but I get the same results. What am I missing?

// defines pins numbers
const byte dirPinX = 5;
const byte stepPinX = 2;
const byte enablePin = 8;

void setup() {
  // Sets the two pins as Outputs
  pinMode(dirPinX, OUTPUT);
  pinMode(stepPinX, OUTPUT);
  pinMode(enablePin, OUTPUT);

  digitalWrite(enablePin, LOW);
}

void loop() {

  digitalWrite(enablePin, HIGH);

  digitalWrite(dirPinX, HIGH); // Enables the motor to move in clockwise direction

  for(int x = 0; x < 200; x++) {
    digitalWrite(stepPinX, HIGH);
    delayMicroseconds(500);
    digitalWrite(stepPinX, LOW);
    delayMicroseconds(500);
  }
  delay(1000); // One second delay

  digitalWrite(dirPinX, LOW); // Enables the motor to move in anti-clockwise direction

  for(int x = 0; x < 200; x++) {
    digitalWrite(stepPinX, HIGH);
    delayMicroseconds(500);
    digitalWrite(stepPinX, LOW);
    delayMicroseconds(500);
  }
  delay(1000); // One second delay

}


texts: What would be the output voltage of the full wave rectifier output when center-tap is removed?

texts:
This is the circuit I have been analyzing.

My intention is to calculate the output voltage at the resistance RL when the center tap is removed.

With center tap connection, output voltage VRL(DC) is calculated is given below,

When center-tap is removed, my understanding,

Secondary output voltage will be the sine wave with peak voltage = 1.414 * 12V = 16.968 V.
At the positive voltage diode D3 will conduct and negative cycle D2 will conduct. So each output would be equivalent of half-wave rectifier.

Output (VRL(DC)) voltage (DVM reading) would be = 16.968 V - 0.7 V = 16.268 V

( Note: The reason I am taking the peak voltage as the output voltage is due to the high output capacitance (470 µF). That is why I am not using the average voltage equation Vp/π)

Can you please review the output voltage calculation when the center-tap is removed?


texts:
The question is as shown below:

The answer from the book is as follows:

However, below is my attempt, is my approach accurate?


texts: I want to build some type of electrical circuit to detect alpha, beta , theta etc. waves from the brain and maybe even show the frequency in hertz . Or at first, generate a higher power wave for my scope to read. How can this be achieved? And what would I use to pickup the waves?


texts:
I'm working on a transimpedance amplifier for a phototransistor in order to create a sensor that counts objects falling down a pipe.
This is the sensor: https://www.digikey.it/short/0vq01q7h
Datasheet: https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Optoelectronics/Datasheets/OPB708-709-740-748.pdf (Model name: OPB742)
And this is the opamp: https://www.digikey.it/short/zjbbjrj0
Datasheet: https://www.diodes.com/assets/Datasheets/TL072.pdf
The power lines available on the board without adding another buck converter are +12V, +5V, +3V3 and of course GND.
I basically need to translate the current flowing through the phototransistor into a readable voltage that will be fed into a binary counter or any microcontroller (passing through a Schmitt trigger before). When there is no object in front of the sensor there will a current I_min, and when an object is present a current I_max because of the increased reflectivity.
The circuit needs to map I_min to GND (or +5V) and I_max to +5V (or GND) so that it can be treated as a binary state.
Keep in mind that I need to improve the response time of the phototransistor as much as possible in order for the system to have a good bandwidth.
This is the circuit I've come up with:

simulate this circuit – Schematic created using CircuitLab
In the schematic I've treated the phototransistor as a current source for simplicity.
In a steady state condition:
V_out = V_plus - I_c * (BASE_GAIN + VARIABLE_GAIN)
The idea is to calibrate it in this way:

While the sensor is in a "no-object condition", so I_min, regulate the trimmer OFFSET such that V_OUT is set to +5V (or the maximum the opamp can handle, a bit less)
Put the object in front so that the current rises to I_max, and regulate the trimmer VARIABLE_GAIN in order to have the sum of the feedback resistors high enough to bring V_OUT to 0V

Here are my doubts:

Is it a good choice to connect the transistor collector to the highest available voltage (12V)? My knowledge about phototranistors is not deep enough, but as far as I understand, the response time sould improve with a higher collector-emitter voltage (?) which in this case is held constant at around +7V by the op-amp. Without reaching the breakdown voltage of course.

How do you think I could improve the stability of the system? For sure capacitor C1 is needed, but should I do something more?


texts: I know somehow it combines different harmonics to synthesize notes, but I don't exactly know how this is implemented.


texts: Calculating charge entered into a circuit element for a given time

texts:
Looking at p 1.2-4 in Introduction to Electric Circuits by Dorf (See top of p16)

I don't understand why the charge for 4 < t < 8 is 8- t.

The current for that time is given as -1. So getting charge by integrating that gives -t, over the period 8 to 4.

At the lower bound, it will be -4, so I thought the answer should be:

integral upperbound - integral lowerbound

and if upperbound is taken as an aribtrary point t, within the range, 4

it would be = -t - (-4) = 4 -t.

So why does it become 8-t?


texts: The rate of change of magnetic flux linkage with a rotating coil

texts:
When does the rate of change of magnetic flux linkage with a coil rotating in a uniform magnetic field equal zero?

I think the answer would be:

  when the coil completes one revolution.

as the the the change in the magnetic flux in the first half of the revolution is in opposite direction to the change in the magnetic flux in the second half, or I am wrong? Because someone told me that it will be when the coil is parallel to the magnetic field lines, so what is correct?


texts:
I am studying Arduino ADC and I have not much background in micro-controllers. Excuse me if this question is too basic.
I found that people use external ADC for better resolution as compared to the built-in ADC of Arduino. One thing which I could not understand was the bit resolution. I saw people using ADS 1115( 16 bit) with Arduino ( 10 bit). How does Arduino measure such resolution when Arduino Mega's resolution is 10 bit itself?  What would be the point of using an external ADC with a resolution higher than that of Arduino Mega's ADC?


texts: How to find out which end of a dead battery is the anode, and its voltage

texts:
The battery pack for an old rc car I played with as a kid, has died.  Salt crystals everywhere, smells like vinegar.  The pack consists of 8 batteries of AA-size connected in series.  The red markers in the pic below are mine.

Both sides of the individual batteries look identical.  Tried to measure the direction of the voltage, but my multimeter is only getting brief, spotty measurements I dont think I can trust.  I´m unable to find info from the manufacturer, and there are no labels with relevant information.

cf. also
attempted voltage measurement
attempted voltage measurement #2
closer view of single battery

I´m hoping through the clever use of duct tape and paper clips to make a new battery pack.  Is there any way to be reasonably sure of the magnitude and direction of the voltage so as not to destroy the car?  Also, would it help if I knew what the battery salts taste like?