texts: Can I add to the wire length of C9 LED Christmas Lights?

texts:
I've found plenty on the topic of shortening C9 LED Christmas Lights, but have not found anything about lengthening a string. I don't want to add any additional bulbs, but rather add some additional wire to transition between areas that I don't want lights (between windows, gutter/facia transitions, etc.).

I plan using the same wire (22 AWG) and the longest run would be about 10' of additional wire on any given strand. Light strands being used are the EcoSmart
50-Light and EcoSmart 100-Light LED Multi-Color C9 Light Set from Home Depot.

Any problems with this? Thanks in advance.


texts: power supply noise measurement with 1Mohms input + 50 Ohms feedthrough termination

texts:
We need to measure power supply noise measurement for 0.82V,1.0V,1.2V,1.8V rails.
Setup will be:
50Ω, RF176 Co-axial probe directly soldered across output capacitor, configure oscilloscope input to 50Ω and with lowest vertical division to measure the ripple.
Low end scopes like DSOX3024A have offset ranges up to ±2V @ 50Ω, but new scopes can't offer more offset with 50Ω impedance. With AC coupling impedance is 1MΩ which is not matched.
I am planning to use MXR104A(this is common scope which i can use for other measurements also) to do the Power supply noise ripple measurement, But with 50Ω Input impedance offset ranges are as below
≤55 mV/div: ±0.8 V,
≤120 mV/div: ±1.6 V,
≤260 mV/div: ±3.2 V.
with 1MΩ input impedance
<10 mV/div: ±5 V,
≤200 mV/div: ±20 V.
I am thinking to use 1MΩ input impedance on MXR104A so, that i will have more OFFSET range of ±5 V, but to have 50Ω input impedance for impedance matching use a 50Ω feedthrough termination(Fluke TRM50 Coaxial Feed-through BNC Male to BNC Female Cable Terminator) before MXR104A input.
I don't have option to use high cost Power rail probes/differential probes, only this Option i have.
Do you see any issue with this setup for measurement of ripple.


texts: Monitor clock cycles for code on arduino/AVR?

texts:
Is it possible to monitor a block of code and determine the number of processor clock cycles that code took on an Arduino and/or AVR atmel processor? or, should I rather monitor microseconds passed before and after code run? Note: I'm not concerned with real time (as in, how many real seconds passed) as much as I am in "how many clock cycles does this code require from the CPU"

The current solution I can come up with is from time.c:

#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
#define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() )

wiring.c adds:

#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() )

By this account i could calculate clock cyles passed by monitoring microseconds passed and then pass that to microsecondsToClockCycles(). My question is, is there a better way?

sidenote: are there good resources for performance monitoring of the AVR. lmgtfy.com and various forums searches do not provide any obvious results, other than exploration of timers

thanks


texts: How do car remote control work? On what medium do they communicate? How do the transmitter and receiver communicate?  Is it blue tooth, infrared or any other kind technology?


texts: Battery Pack Management: need to balance during discharge?

texts:
I'm looking into the fault detection and monitoring subsystem of out unmanned vehicles (airborne and ground-based) batteries. We employ LiPo-battery packs of various configurations which are charged by cell-balancing chargers. Only properly charged and balanced battery packs are put to service. During operation, only the total pack voltage is monitored.

I figured that monitoring the individual cell voltages and temperature will help us detect battery deteriation early in order to avoid catastrophic losses in-flight.

I wonder, whether cell-balancing during discharge would do any good, or basically would only waste energy without much effect on battery health or reliability.

Edit: We build our batteries ourselves from basic unprotected cells. Cells are not specifically matched as far as I know. However, we generally use cells of a single batch for one battery only.


texts: How might the Lecroy HVFO High Voltage Fiber Optically Isolated Probes Work Internally?

texts: I've been looking into these fiber isolated probes that Lecroy makes (http://teledynelecroy.com/probes/probeseries.aspx?mseries=537), and I'm curious how they're sending the signal over the optical fiber. I was thinking maybe you could make a probe with a sigma-delta converter in it and then send this 1-bit ADC digital signal optically. The manual/datasheet claims however that the signal is carried as FM (note "frequency modulating optical transmitter"). I'm curious how you might design a voltage to frequency converter with high linearity and 60 MHz of modulation bandwidth, if this is how it indeed works.


texts: Using GNU/Linux as an Electronics Engineer?

texts: Are there many companies that provide a GNU/Linux environment for their electronic engineers?


texts:
I've created a simulation on Matlab of amplitude modulation. After demodulating the signal I need to add a low-pass filter to remove the high frequency components.

I'm confused as to why this is? I though it was to get smooth out some of the additive white Gaussian nose I added, but surely that noise is added across all frequencies as its 'white' noise.

What is the need in filtering the demodulated signal and why is this needed before we can recover the signal?


texts:
For this question in my view the the output power should be \$1 mW\$ since the antenna is lossless,and so no ohmic power should be dissipated and the radiated power should equal the power fed.

\$\eta_r=\frac{P_{rad}}{P_{in}}\$,here antenna is lossless so \$\eta_r=1\$ so \$P_{rad}=P_{in}=1mW\$

But the answer is \$4mW\$.Why is it like that can anyone explain please?


texts: Calculation for input bulk capacitor of a buck converter: Needs help in understanding equations

texts:
Below diagram shows the calculation for input bulk capacitor of a buck converter.The bulk capacitor prevents the input voltage from dipping too much during a sudden load change(load step).

Iam struggling to follow the theory behind the derivations followed. I have studied that in a second order RLC circuit, if we apply a step voltage at the input, it takes roughly tr seconds to reflect the change at output (case 1).The rise time equation exactly matches that of in the diagram.

But the present scenario is slighly different from the previous case. A load step (sudden current change) occurs at the output side (Vin side) of RLC circuit (Case 2). This additional load requirement is catered by the host after tr seconds.

Is there any theorem (duality or bidirectional ??) which justifies the usage of the same equation for both cases?


texts: Atmels AtSAM3s gets a bit warm running a test code on my dev board. Is there a problem?

texts:
I have a dev board developed by myself. I was using At91SAM7S256 but now I'm migrating to it's successor ATSAM3S8B. The MCU on the dev board for SAM3S gets warm.

I am searching for someone with experience of working on this specific chip to tell me if this is normal for ATsam3S8B to get warm up to 36-40 degrees of centigrade(the ambient temperature is 23), or I should investigate a hardware design fault?

:


texts: Difference between a flared and not flared rectangular waveguide antenna

texts:
Someone can explain to me the difference in terms of performance between a flared  rectangular waveguide antenna (precisely a pyramidal horn) and a not flared rectangular waveguide antenna?

In horn antennas, is there is a better impedance matching with the free space?

In some books I found only the explanation of horns, but I didn't find anything about the reason to make a flare on a rectangular waveguide to improve its performance. The only thing that I found is that flaring is mostly used at high frequencies, like microwaves.


texts: Can we reduce power consumption of digital interfaces by using high impedance transmission lines?

texts:
Transmission lines must be terminated with the same impedance as the transmission line has itself to get an impedance matching and avoid reflections at a high impedance end point. This termination resistance closes the current loop between two differential signal lines and creates a decent amount of power loss so that low voltage amplitudes are required to reduce power consumption.

But still digital interfaces use quite low impedance transmission lines like 100 Ohm in Ethernet communication.

Can we reduce power consumption of digital interfaces by using high impedance transmission lines with high impedance terminations? Because I don't know of any examples I assume that it is not a good way to go. If that is true, why so?


texts: How to reduce the beep noise coming out of an MP3 module for my TDA2030 amplifier circuit project?

texts:
After making a stereo circuit board with a TDA2030 and mobile aux as input, I wanted to connect an MP3/BT module to my own indigenous audio amplifier circuit which would make every action easier I supposed, but things went wrong.
In mono circuit, the Bluetooth does not output that highly annoying noise but I want it to be stereo.
Below are the pictures of my MP3 module:

The module has 5 modes which are:

Bluetooth mode
AUX mode.
Pendrive Mode
SDcard Mode
FM Radio mode.

In Bluetooth mode, the noise is produced much more than others, unbearable Bluetooth spike frequency sound, in AUX and Pendrive mode, the noise is quite low (bearable.)
In FM Radio mode, there is almost no noise.
Here is my circuit:

simulate this circuit – Schematic created using CircuitLab
I also tried connecting some filters to the output of the MP3 module which were supposed to reduce noise.
Like this:

simulate this circuit
That did not work at all.
When I connect the stereo circuit input directly to my mobile stereo output using headphone jack, it works very well until I connect the module again.
Any suggestions or helps please?
Please point me my errors using a proper schematic which will make it easier to understand for me.


texts: Sometimes when soldering, it sorta "pops" and leaves tiny droplets of clear, hard substance on my PCB. It seems to be able to melt away with a brush of my iron, and isn't too bad. I'm ironing at about 260 degrees C (510 F) with "44" rosin core .80mm.


texts:
I am planning to buy inverter.
I finalized one model; however, I was told that it uses aluminum windings whereas the other model has copper windings. They recomended I should buy the one with copper windings because it will have more longetivity and efficiency.
Is this true? What about heating?

I found this link on the web but it does not say anything about aluminum, just copper and silver winding comparison.
http://upsinverterinfo.com/is-microtek-silver-winding-inverter-better-than-luminous-copper-winding.html


texts: Resistor Noise - What it will have effect on, in a circuit?

texts:
Reading the article resistor noise  and knowing that resistor noise is in the form of Voltage (is that thr right expression?!) leaves me wondering that this generated voltage will have only eefect through the circuit tracks and enters the components in its way, or if it is in form of EMI and can have effect on nearby sensitive components even if they are not connected to the noisy resistor?

If the second one is correct, would remedy be capping the resistors with a metal shield (like the cpa in the analog section of old PC video cards or TV cards?)


texts: Skewed frequency response of RLC circuit

texts:
I built a simple RLC circuit:

I'm using a signal generator as input, and I'm reading the voltage across the capacitor with an oscilloscope.

I've calculated that the resonant frequency (where I will also measure the highest voltage across the cap) is around 73kHz. This was verified to be approximately correct.

Now, I understand that the bandwidth of such a circuit is defined to be the difference between frequencies where the output voltage drops to 0.707 of the maximal value. Here the maximal value is at resonance, around 2.38V. The cut-off frequencies should be therefore where the voltage across the cap is 0.707*2.38=1.68V. I found the corresponding frequencies by turning the frequency higher and lower:

(the voltage peak-to-peak voltage given by the oscilloscope drifted around slightly, but stayed mostly at the 1.68V)

So, the high cutoff frequency was around 135kHz, and the lower one was around 45kHz. This is strange, should the cut-off frequencies be equal distance from the resonant frequency? But here 135kHz - 73kHz = 62kHz and 73kHz - 45kHz=28kHz. So the higher cut-off frequency seems to be over twice as far from the resonance frequency as the lower one! What could be the reason? What am I doing wrong?

I also calculated the Q factor using the formula:

$${\displaystyle {\begin{aligned}B_{\mathrm {f} }&={\frac {1}{\,R\,}}{\sqrt {{\frac {L}{C}}~}}\\Q&=R{\sqrt {{\frac {C}{L}}~}}\,~.\end{aligned}}}$$

With my values of resistance of 10kOhm, capacitance of 47nF and 100uH, I get a Q of 216. As Q is also defined as the ratio of resonant frequency and bandwidth, I can divide the resonant frequency by 216 to get a bandwidth of about 300, which also isn't anything close to reality. So what am I doing wrong?


texts: Analog PID controller (transferfunction questions)

texts:
I have to build an analog PID controller (with op-amps), I've made a schematic:

My questions:

Can I build my PID controller this way?
My PID tranferfunction (in the s-domain) looks like:

$$\text{H}(s)=\text{K}_{\text{r}}\left(1+\frac{1}{\tau_is}+\tau_{d}s\right)$$

But what in my schematic represents the variables from my transferfunction?


texts: Why is the slope of output characteristics of transistor in CE configuration more than that of CB configuration??


texts: one antenna working as receiver and transmitter

texts:
I want to know, if an antenna which transmits and receives the reflected signal can be modeled as an impedance.
For example, the antenna is coupled to a Collpits oscillator and sends out an electromagnetic wave which is reflected by, for simplicity, a wall of a conductor. So it receives something which superimposes the sent signal.
Can this configuration be modeled as an impedance?

The idea is to model this configuration as a "kind of lossy transmission  line" where a transmission line (tl) has a certain impedance depending on its length.

If so, the impedance varies with the distance of the reflecting wall and tunes the oscillator to a slightly different frequency, which is what I want to find out about.
The goal is to have a function of frequency vs. distance.

I can simulate the S-Parameters of the antenna (not done yet), if this is helpful for you to know.

Edit:
Today I simulated the antenna and the software returns Z-Values and S-Parameters that vary over exciting-frequency and distance of the reflector.
So it shows, that the antenna can be modeled as a complex impedance which varies with distance of the reflector. So we can use this impedance shift to tune the oscillator by putting it into the feedback loop.
But:
As said above the impedance varies also with frequency. So imagine we change the distance of the reflector and get a different impedance, then the oscillator changes its frequency which also changes the impedance. So we have a self-backcoupling massively non-linear equation and I don't know how to get around this problem.
Am I at least on the right track? Is there a way of solving this interrelatedness?


texts:
This may be the an unspeakably stupid question for an electrical/computer engineering student to ask, but I ran across a few parts I didn't recognize (which, after some research, I found out were glass tube fuses and automotive fuses), and they made me wonder...

So, a mechanical or thermal fuse I get; enough current, and a switch gets thrown or a piece of solder attaching a spring to a pad melts and the connection essentially ends (ignoring arcing).

But I am holding a glass tube with two metal terminals, probably some gas internally, and a glass body. There are multiple ways I could see that the thing might work (e.g. the gas or the glass is conductive, but highly susceptible to temperature changes, shattering the body in high current), but since I can't seem to find the exact mechanism anywhere online, how do they work?

-- Additional, more general question --

If they are designed to shatter at high current, well...
Why are they still in use? It seems potentially dangerous, or at least fantastically annoying, to have components which leave broken glass everywhere in an expected use case.

edit: It was a very thin wire, and I have awful vision, but it now makes sense.


texts: Does anyone understand where 2.5v , 10 v, and 5V ( highlighted in yellow) are coming from? I know that Vcc=5V, and the two resistors R1 and R2 are in parallel so Req=0.5Kohm, and the voltage divided by 2 which makes it 2.5V . How did they find IE=2.59 mA ? Also, if you can explain the obtained KVL too, it would be great. I can see it but still cannot wrap my head around it.Thanks


texts: I need to know the process for packaging a diode such as inserting the die on the package or case, what is that process like.


texts:
I am trying to write code for a cyclic code encoder in VHDL, but I am not able to visualize how to approach the problem. Right now all I have is an entity and a few diagrams showing my approach as to how I want to build it. If anyone could help me out or point me in the right direction it would be really helpful.
Code for the entity I've written
-- generator matrix is 1 + D + D^3
-- g0 = 1
-- g1 = 1
-- g2 = 0
-- g3 = 1

library IEEE;
use ieee.std_logic_1164.all;
use ieee.std_logic_signed.all;

 entity cc_7_4 is
 generic (
           n            : integer     :=7               ;-- CW length
           k            : integer     :=4               ;-- message length

 port(
      message_input     : in  std_logic_vector(k-1 downto 0)                ;-- input data
      clk               : in  std_logic                                     ;-- input clk
      D                 : inout  std_logic_vector((n-k-1) downto 0):="000"  ;-- pipo shift register to generate the parity bits
      Q                 : inout std_logic_vector((n-k-1) downto 0)          ;-- pipo shift register to generate the parity bits
      rst               : in  std_logic                                     ;-- input reset
      output            : out std_logic_vector(6 downto 0))                 ;-- output data

 end cc_7_4;

How I think I should proceed


texts: alternative fix to: How can I calculate a Joule Thief

texts:
This is based on the original question: "How can I calculate a Joule Thief.

  How Can I calculate a Joule Thief.

Since the gain of common emitter voltage amplifier and it will depend widely on the
dynamic frequency of the LC unit, either way it's not simple to calculate the output
voltage precisely, I wants to know how could I regulate the output voltage to run my
AVR.


texts: 12V Sealed lead acid battery level sensing

texts:
I know that you can easily determine the percent capacity remaining in a battery using an arduino by dividing the voltage down to something that the ADC can read. What I'm stuck on is how the voltage will vary as the battery discharges. I've looked at multiple datasheets and tried to look on Duracell's website for one (I'm using a Duracell Ultra SLA battery), but I couldn't figure out how the voltage behaves as the battery discharges.

The main thing I need to figure out is the voltage at which the battery is considered "dead." But I think I also need to figure out how to read the voltage curves in the datasheets because (from what I can tell) the voltage does not vary linearly with the battery's capacity remaining. Can anyone point me in the right direction for information about this?


texts: The offset voltage of a saturated transistor, makes bjt less attractive as a switch than mosfet. Why? Is there any other logics aside this?


texts: What would be the truth table for the following inputs with a positive edge triggered D flip flop?


texts: PWM Ground Modulation: is this circuit going to affect my other ICs?

texts:
I have designed a fan controller circuit based on the MIC 502 fan management IC:

UPDATED SCHEMATIC

QUESTION #1: The schematic (for the top part) is basically the one available here:
https://bit-tech.net/reviews/modding/pwm_fan_controller/1/
I understand how most of it works but I just can't tell if the PWM signal (when mixed to GND at Q2) is going to affect the main ground and the other circuits on my board? That "GND" sticker is the only GND used for the entire computer.
-> Answered For such a small "contribution" (frequency + current consumption), it shouldn't be a problem.

QUESTION #2 (VOLTAGE COMPARATOR):
The box on the bottom "Overheating Indicator" is basically a LED controller. It checks if the temperature (or voltage) reported by the thermistor TH1 is larger than the "temperature" preset by R5/R6. If so the LED lights up. So basically, R8 is R5 and R6 is TH1@80°C. Is this new schematic correct?

Thanks in advance for your help.

NBs: "Controller+" and "Controller-" are the going straight to the fan.


texts: dc motor positive (RED) and negative (BLACK) terminology/notation

texts:
Is there a standard wiring notation of a permanent magnet dc motor terminology ?

in other-words if 12v is applied to the red terminal and ground to the black terminal does this cause rotation in CW in ALL motors for example and vis-versa ??

i have tested 10 different motors so far with success , but i don't know if this is just by chance !


texts: Understanding SAW filter from optical image

texts:
As i know ladder type filters comprised by series and parallel resonator arrays. I suppose dark blue areas are series and light blue areas are parallel arrays(or opposite) in the below figure. I wonder if this structure contains reflector. Also i wonder which parts series and which parts parallel if i think right. Is there anyone who has worked on this before can help me to understand this structure?
This structure is a 1575MHz filter.


texts:
I'm trying to debug my dev board here, using LPCXpresso v7.1.1 [Build 125] [2014-04-01] , Manjaro linux (Arch based), and a J-link programmer. Every time I tried to debug my program, I got an error: connection refused. I've installed the 32 bit libs already.
Finally I was able to install the appropriate packages for the J-link and GDB. Now xpresso launches the debug session, but it looks like nothing happens. If I watch the GDB server in the terminal, while I launch xpresso's debug, I get this:

Resetting target Downloading 4096 bytes @ address 0x00000000
Downloading 2968 bytes @ address 0x00001000
Downloading 20 bytes @ address 0x00001B98
Writing register (R8 = 0x00000301) WARNING: Unsupported register (1)
Reading register (PRIMASK = 0x00000000) GDB closed TCP/IP connection

I'm using an LPC1769.


texts:
I have looked through some of the current limiting responses, but don’t see any close to what I’m working on for my project.

I have an EV system running in around 200 - 270V DC. I want to build a circuit that will allow me to connect an external say 280V DC LiPeO4 battery bank and charge up the internal DC system.

Obviously, I don’t want to dump the total current possible when the circuit is made. I have a Gigavac high voltage relay that can make the circuit.

I want something that will limit the charge to say 20A at 270V DC to the internal battery system to ‘top it up’ in real time.

I’m an engineer but more in thermal/mechanical with some electrical background, but not in ICs or design.

Any help is appreciated, but remember to keep it simple (e.g. pretend I’m a 10yo) :D


texts: Error communicating with GSM SIM900 with AVR.?

texts:
I am trying to interface GSM SIM900 with AVR Controller. Till now I have
done programming which transmit the command ATD and it makes a
call to my cell. GSM response to this command by sending OK. I want to
make a program which also receives this response OK and to do that I have
written my code but it is not working as it should be. I am attaching my
code please tell me where I am doing wrong.

CODE:

void serial_Init()
{
    UCSRB = (1<<TXEN)|(1<<RXEN);
    UCSRC = (1<<UCSZ1)|(1<<UCSZ0)|(1<<URSEL);
    UBRRL = 51;
}

void serial_Tx(char *str)
{
    for (unsigned int i=0;str[i]!=0;i++)
    {
        UDR=str[i];
        while(!(UCSRA&(1<<UDRE)));
    }
}

 char serial_Rx()
 {
    //Wait untill a data is available

    while(!(UCSRA & (1<<RXC)))
    {
         //Do nothing
    }

     //Now USART has got data from host
    //and is available is buffer

    return UDR;
 }

 void uart_put(char data)
 {
     UDR=data;
     while(!(UCSRA&(1<<UDRE)));
 }

int main(void)
{
    DDRA = 0x00;
    DDRC = 0xFF;
    PORTA = 0xFF;
    serial_Init();
    char data[2];
    while(1)
    {
        if(PINA==0xFE)
        {
            serial_Tx("ATD<number>;\r\n");
            for(int j=0;j<=100;j++)
            {
                data[j] = serial_Rx();
                uart_put(data[j]);
            }
        }
    }
}

Upate Current result on hyperterminal:


texts: Test device for capacitive touch screens?

texts:
Are there any (more or less) simple test devices for capacitive touch screens,
e.g. something which I can attach to a touch screen and which is able to do capacitive inputs at fixed locations (ideally, it contains a matrix of such locations)?


texts:
I'm using a power boost to convert a 18650 battery to 5V:

How to detect low battery (i.e. battery voltage under a certain threshold), and send this information to a microcontroller?

(I'm currently using a RPi, which has no ADC, but the question may be valid for other computers/microcontrollers).

Note: this question is interesting but the main answers use an ADC. I'm more looking for a simple electronic solution.


texts: How do security alarm systems measure zone resistance?

texts:
Recent security alarm systems use EOL(R) or DEOL(R) to terminate the line of the zones.

Question 1: What method is used to measure the resistance of a zone?

I can think of two options:

It measures voltage drop on the zone using a current source
The zone is part of a voltage divider, voltage measured on the zone

Question 2: How good/bad idea is to use a simple voltage divider for that?

UPDATE

Since not too much answer arrived, I have done some experiment.

I bought 100m 6x0.22 shielded cable and tried out the voltage divider option. I had different scenarios, I tried to put noise on the line by coiling the cable on a 2000W electric heater's input line and switching it on and off. I used 5V and 0.9mA to drive the line. I was watching the line with an oscilloscope but did not notice anything. I did not even use a single capacitor as a filter, I used only the shielding. Without the shield, of course, there were very ugly peaks when I switched off the heater. Although, I think if I would have used a current source, that would also be affected by such an EMI.

Since there is no load on the voltage divider, there is only a very minimal current which allows longer cable without significant voltage drop. Despite of that, I don't think that is common to use a cable for a zone which is longer than 100m.

There were concerns about installation contractors, who don't care about specifications, noise supression etc.. These people are out of scope this question. If someone decides to use something improperly then he has to deal with the consequences. In our country the installer can be punished if the alarm system doesn't work correctly and the house get robbed because of that.

However, I'm not a specialist of this field, I just want answers, that's why I test and suppose.


texts: Why diameter of telephone cable is exactly 0.44mm and 0.63mm

texts:
I am wondering why telephone cables are having the diameter or exact 0.44mm and 0.63mm? Is that any special reason?

I have seen some of the cable have up to 2400 twisted pairs, could I know is the number of pairs will affect performance of cable?

Thank you.


texts: How to escape redundant stated when using J-K Flip Flops?

texts:
I've designed a counter using three J-K flip flops, but I have two redundant states. How can I ensure that the system has a way to escape these states if they occur?

I've tried searching for help on the internet, but all of the results I found either skipped around the topic or didn't use J-K FFs.

The states being counted through are 000, 001, 010, 100, 101, 111 (first digit = A, second = B, third = C).

The circuit is:

Ps, please ignore the AND gate leading to Z.


texts:
I was designing a product in which two USB Power Delivery ports are populated in the design so as to:

Provide power from wall charger supporting PD
Provide high speed communication with laptop

Now we are thinking of using this second port also with PD functionality, so it can consume power from laptop supporting PD in case power through PD port-1 is absent.
But this requires ORing circuit for these two USB PD ports.
So, does any one have any knowledge on ORing two USB PD ports or any such designs proven to be successful?


texts: How to visualize 3 phase currents vector diagram

texts: I want to visualize the 3 phase currents which are 120 degrees apart by vector diagrams and calculate the net current vector and hence the net magnetic flux vector. The application is the PMSM motor and what i want to do is continuously capture the stator phase currents and draw magnetic flux vectors on abc axis. Please advise on what tools can i use. What programming language i can use. This will be the first step in coverting from abc axis to alpha beta axis.


texts: How instruction skipping is avoided during procedure calls in pipelined architectures?

texts:
I have a question regarding a PC register (IP in x86 lingo). In most architectures it is updated during an execution stage and thus stores an address of a next instruction to be fetched. It seemed clear to me until I started to reason about a pipelined architecture. For example, imagine the following classic RISC pipeline with 5 stages (Fetch, Decode, Execute, Memory access, Write back) which is filled with the following instructions (designated as "a", "b", "c", "d"):

F D E M W
c b a - -

0x12 call [0x100] ; a
0x14 mov ax, 10   ; b
0x16 add ax, 2    ; c
0x18 nop          ; d <- IP

By the time an instruction "a" reaches the E (Execute) stage in the pipeline, it is already full with subsequent instructions and IP points to an instruction at address 0x18 (the next one to fetch). When "call [0x100]" executes, it saves the contents of the IP (a return address) on the stack. But it's obviously not the address of the instruction following "call [0x100]"! So, as we return from the CALL, we effectively jump over 2 instructions since pipeline is flushed during the CALL execution!

Which means that:

There is another hidden register storing the address of the instructions being executed and it's stored on the stack instead of IP
It doesn't work this way
I am missing something :)


texts:
My son's science teacher had 15  fifth grade students stand in a semicircle holding hands. The student at each end held an electrode connected to some kind of variable contoller. The teacher  increased the voltage until they could "feel" the electricity. He also had one student in the middle let go to demonstrate a "complete circuit"
Is this dangerous?


texts: How do I know I'm not drawing too much current for my 3.3V supply?

texts:
Continuing my learning expedition, I've decided to use the LM3S5R36-IQR80-C3 ARM Cortex-M3 MPU, to try and learn to build my own little experiment PCB, almost like the Teensy 3.0. The idea is to learn the entire process of designing the PCB from scratch.

I've come up with the following circuit so far, working on ESD protection for the USB port, as well as the 3.3V supply for the Vdd pins on the ARM chip.

I'm a hobbyist, so I have no electronics degree or background, so I'm using the datasheets for the ESD array I selected, as well as the voltage regulator, to hopefully get a steady 3.3V voltage supply from the 5V USB Vbus.

Here's my circuit so far (if it's broken, it's coz I had no help, except Google) :

I'm not sure if I can ask here whether the circuit looks right or not, I am looking for some constructive criticism, however. So feel free to comment, or refer me to a site where I can have my circuit scrutinized by the community.

More, importantly, let me state my actual question...

My next step is to start connecting the 3.3V supply from the regulator, to the ARM chip's Vdd and Vddc pins to the 3.3V supply. The thing I want to know is, how I can be sure I am not pulling too much current through the regulator or the USB 5V Vbus. The last thing I want is to sit with a bunch of scorched spares and a broken USB port on my Mac.

There are 4 Vdd and 4Vddc pins, so I understand I can get the 3.3V to each pin, by simply connecting them to the supply in parallel. This however, depending on the resistance the chip causes between the 3.3V and GND, makes it tricky, and I'm not sure how to go about making sure I don't draw too much current.

I guess it comes down to how much current the ARM chip sinks, but I'm not sure how to effectively work this out.

I hope my question makes, sense, feel free to edit to clarify it.


texts: Capacitance calculation of comb-drive actuator

texts:
I just want to make sure that I am performing this calculation correctly...

From this COMSOL study, I gathered the following info...

$$C_t = N\frac{\varepsilon_o\varepsilon_rl_ot}{d}$$

$$C_f = \varepsilon_o\frac{WL}{G}\left(1+\frac{G}{\pi W}\left(1+\ln\left(\frac{2\pi W}{G}\right)\right)\right)\left(1 + \frac{G}{\pi L}\left(1+\ln\left(\frac{2\pi L}{W}\right)\right)\right)$$

$$C = C_t + C_f$$

& performed the calculation for \$N=1\$...

import math

l_o = 90E-6 #Finger overlap
t = 5E-6 #Finger thickness
N = 1 #Number of finger overlaps
L = 90E-6 #Finger overlap
W = 5E-6 #Finger width
G = 5E-6 #Finger gap
e_o = 8.854E-12 #Vacuum permittivity
e_r = 11.7 #Relative permittivity
g = G/math.pi

C_t = N*e_o*e_r*l_o*t/G
C_f = (e_o*W*L/G)*(1 + g/W + (g/W)*math.log(2*math.pi*W/G))*(1 + g/L + (g/L)*math.log(2*math.pi*L/W))
C = C_t + C_f
print(C_t)
print(C_f)
print(C)

& got...

9.323262e-15
1.6703194931600559e-15
1.0993581493160055e-14

But from Table III of referenced paper, the values should be...

2.8819e-14
0.1403e-14
3.022e-14

I don't think I'm calculating fringe field capacitance correctly because my answer is independent of # fingers. What else am I doing wrong?


texts: Best method for determining tolerances based on production data

texts: Say I am producing a wound coil which is ultimately going to be used in a colpitt's oscillator circuit. I measure the Ls and Rs of the coil, and then install it in a ferrite and then test it in the circuit, where I determine if it works or not, based on the resulting frequency and amplitude of the oscillator output. What is the right statistics tool to help set the production tolerances for said coils? I was thinking that I can use the measures Ls and Rs and use them as the features, and the circuit performance to label the data good or bad, and use LDA to see if the good vs, bad coils are separable, and then set the tolerance based on the projected good coil's distribution mean and SD ...is this a good approach? Is there a better way?


texts: Is it possible to use a net tie on a plane layer? I know how to use a net tie to connect two different polygon pours together. But how would one go about this on a plane layer -- which is a negative layer?


texts:
I can't figure out a valid circuit for the following conditions:
I have an input signal varying from 0 V to 3 V. My ADC's voltage reference is 2.048 V. I only care about the input voltage starting from 0.768 V and ending at 2.048 V + 0.768 V.
So 0.768 V at the input (and bellow, since I have no negative voltages in the circuit) gives 0 V at the output.
2.816 V at the input (or higher) gives 2.048 V at the output.
So in practice, I just need to somehow offset the output signal by 0.768 V down (VOUT = VIN - 0.768 V assuming 0V is the minimum value).

I tried to set this up with a non-inverting level shifter circuit, but with no luck- is it the right direction?


texts: Avalon-ST interface properties of 10G MAC MegaFunction

texts:
I have an instance of the 10G MAC MegaFunction that contains an Avalon-ST interface. Reading through the Avalon-ST specification, I see that every Avalon-ST instance has "interface properties" (see table 5-2).

Now the 10G MAC MegaFunction does specify some of the interface properties (see section 7.2.1) but not all of them. I have tried searching the files Quartus II generated for the interface properties to no avail.

Where can I find the Avalon-ST interface properties of the 10G MAC MegaFunctin?


texts: How to increase sensitivity of audio-frequency pickup coil

texts:
I am building an instrument intended to pick up weak (~100 picotesla) 25 kHz oscillating magnetic fields with Faraday induction.

As shown in the photo, I have a 4-layer solenoid coil for pickup followed by a two-stage preamplifier that amplifies ~1000x for frequencies above 10 kHz.  The pickup coil is not tuned and the circuit looks like below:

Signal/noise after Fourier transform of the time-domain signal, 1500 nT field at 26 kHz. 500 ms acquisition time.

Presently the setup can detect oscillating fields down to 2 nanotesla.  There is a significant change in noise floor when I connect/disconnect the pickup solenoid coil, which suggests sensitivity can be improved.  A possible solution is tune the inductor to the frequency of interest.  My question is what is the best way to approach this, and general comments about how to improve the sensitivity are also welcome.

EDIT  Suggestion by Henry Crun: tune an LC circuit to 25 kHz and use as the pickup coil.  I'm limited to an air-core inductor for pickup.  So I attempted this with the following circuit

And this was the result: a pickup coil tuned at 24 kHz.  So, the question now is -- what is the best way to increase the Q factor of the coil, which would increase the sensitivity.  I have a detection limit of ~100 pT/Hz^1/2 and want to improve on that by another factor of 10 to 100.


texts: Why is it important, in terms of ESD protection, to ground a PCB to its case (if not insulative)?

texts:
I have a 12V DC-powered SBC to mount inside a metal case. How important is it that I connect its ground(?) to the metal case on the interior? How is this going to protect against ESD events?

From my understanding, whenever I touch the metal case, will I not be "exchanging" (thus equalizing) charges? Wouldn't connecting the case to the ground of the PCB inside allow the flow of this charge within the PCB? Also, would that not expose me to any kind of danger from the current flowing within the board, as the typical 12V AC/DC adapter doesn't have a connection to the mains ground, from what I see.

I am a bit confused because I do not know how important it is to actually do the grounding, plus I don't really know how exactly to do it. Do I just find the ground pins and connect it through some wiring to some random point on the case?

(This looks like the case, with the 4 screws at the corners, which is where I will mount the board that looks like this)


texts: Charging batteries with three LiIon modules?

texts:
I bought few LiIon modules(TP4056, from eBay). Every module has 1.2kOhm resistor, so module will charge batteries(six in parallel) with maximum 1A.
Because I have 42Wh power source, it'll take around 30 hours to charge from ~0% to 100%. So my idea is to use three TP4056 connected in parallel with batteries. Does it will work without blowing up batteries? Schematic is below(MT3608 is step-up booster). Batteries are from my old laptop's battery, they are without Protection. Also, I won't use TP4056's Protection. At best scenario, batteries will get 0.4A of current(2400mA divided by six batteries).


texts: How to avoid regulatory approval regulations, when chosing a RF module?

texts:
I've been trying to implement RF capabilities into my projecto, but I don't want to pay thousands of euros to get an ETSI certification in case it gets into production.
I know that if I get a complete module like Xbee I could avoid that problem, but those modules are a little bit too big for what I want to make.
How to avoid ETSI regulations (like some kind of frequency or dB range that doesn't need aproval, or a little smaller zigbee modules or at least some kind of list that displays modules by standard compliance)?


texts: CAN bus goes through periods of re-sending messages continually

texts:
I'm having an issue where my microprocessor CAN bus module continuously re-sends its last message, even though it seems to be received properly by my USB-CAN monitor on the other end.

I'm attempting to implement the J1939 CAN bus protocol in a Microchip DSPIC30F4013 (with an ISO1050). I found a J1939 library from Microchip for a different chip family (PIC18xx) and have ported it over for my DSPIC30. The only nodes on the bus are my device-under-test and the USB-CAN monitor I'm using for debugging. I've mostly been using a Ginkgo USB-CAN Interface Adapter from ViewTool; I've also used the CANalyst-II some as well. Both the monitor and my DUT do have 120 ohm termination resistors.

My firmware has three command messages it can receive and two status messages it sends. I've never had an issue with sending the command messages from the CAN monitor to the DUT. My DUT has always done the thing it's supposed to do upon receiving that command, and I've never noticed anything crazy on the bus at those times.

Sending a status message, however, has consistently NOT behaved properly. The status messages alternate every two seconds:
send msgA, wait 2s, send msgB, wait 2s, send msgA, ... ...
 At some point, a "condition" is being met that causes the CAN module to continuously re-send the last message. The difficult part is that it doesn't happen predictably or reliably. Sometimes it's immediately on power-up... sometimes it is seconds later... sometimes it doesn't happen for minutes.

Once I realized I had this problem, I added on some state-level logic to my 2-second trigger. Now I check the CAN status/results register(s) to see if the previous message ended properly. If not, I manually abort and then send the next message. This is kind of interesting in that now what the operation looks like is:
send msgA, wait 2 seconds, continuously send msgB for the duration of the 2 seconds, send msgA, wait 2 seconds, continuously send msgB for the duration of the 2 seconds ..., ...

The part that most confuses me is how it seems to only affect one message at a time. If it were a module configuration problem, I would have expected all messages either sent and/or received to flake out.


texts: Why is Zener avalanche noise saw tooth shaped?

texts:
I have the following schematic of a Zener based noise source:-

simulate this circuit – Schematic created using CircuitLab

When built, an oscilloscope reveals a saw tooth noise signal at the "Noise" node, like:

The time base is 1us/div.  Can anyone explain why the signal is saw tooth shaped? Initially I expected a triangular, or even sine shaped wave form.  I think that it's something to do with the impedance of the Zener in conjunction with the much higher 100 kOhm resistor.  The electrons cascade freely across the junction, but the resistor restricts current flow when the avalanche stops.  We're talking 60uA. The result being slower charge build up than when current flows during avalanche.

This wave form isn't particular to my set up.  There are other examples elsewhere on the Interweb when people have really zoomed in on the signal,
  one being https://youtu.be/CAas_kbTW3Q?t=714.  Also there's a good chart here showing the rising edge to be slightly curved.  It's probably unfamiliar as it's usually shown with a much slower time base.  Am I right about the resistance/impedance explanation?


texts: Meaning of these terms - Simulation of vector control (FOC) of induction motor?

texts:
I'm having hard time doing simulation of vector control for 3 phase asynchronous machine. I was studying MATLAB - Simulink simulations available already on MathWorks site but I couldn't understand that what certain terms mean.

1e-3 was added in denominator for following two equations.

As you can see the equations written below model by author himself gives no clue as why 1e-3 is there. And this is not the only one simulation which has this term here. Even Mathwork's site has this term as can be seen from this page.
But I couldn't find any documentation as from where does it comes. Is it because they want to ensure there won't be division by 0? But then isn't 1e-3 quite larger term? This was wild guess ...

The last block in previous figure (K*Ts/(z-1)) shows discrete time integrator right? But what is the difference between that integrator and one shown below (it is PI Torque controller) and what is its significance? Note that this is also part of the same page linked above.

Thanks in advance.


texts: What is a good microcontroller for PWM signal generation?

texts:
I want to build a Pulse Width Modulation board, something that would allow me to send different PWM signals to the devices connected to the board.
My main criteria - is being able to send at least 4 different PWM signals at the same time (e.g. with different frequency)

I need a microcontroller or chip which is not too hard to work with, preferably supports gcc and can handle PWM.

Any suggestions are much appreciated.


texts: LTSpice current dependent current source timestep too small error

texts:
I solved this circuit by hand.Which asks to calculate vo and Io in the circuit.

And I tried to verify results with LTSpice.

If I change dependent current source B2's equation to I = I(R1)* 50 it gives an error like that:

If I use I = I (R1) it works fine. What might be the problem here?


texts: Almost all the PCBs I've seen for now are right angle. But I think such acute angles are not safe for handing, even when installed on the products, it may do some bad to the wires connecting the boards. But why the chamfered corners are so rarely? For cost reason? Or there are other merits using right angles?


texts:
My circuit is the schematic above, I just recently added the push button in the bottom left (P2.3) and my code goes to crap and I'm receiving/sending junk over UART when P2.3 is no where near the UART pins. I'm assuming P2.3 is drawing all the current and causing these issues. However, as you can see I've copied the way TI does the push button P1.3 on the launchpad:

Here's how initialize Port 2

        P2DIR = 0xFF;
P2DIR &= ~(rf_intrpt + PB);                                                 // Set rx_intrpt as an input
P2OUT = rf_cs + PB;
P2REN |= PB;
P2IFG = 0x00;                                                           // Clear interrupt flags
P2IES |= rf_intrpt + PB;                                                        // Interrupt on high->low transition
P2IE |= rf_intrpt + PB;                                                     // Enable interrupt
P2IFG = 0x00;

What am I missing when correctly implementing this push button?


texts: Isolation Transformers (Capacitive Coupling)

texts:
In my application I have an issue with ground loops and to solve this I require to have devices isolated from their drivers.

The system operates with a 13.56MHz signal and a wide bandwidth is not of concern.

Capacitive coupling between transformer windings is the greatest concern.

How should I select a transformer 1:1 ratio that will provide the best isolation and allow operation at 13.56MHz?


texts: At school our soldering irons don't have grounded tips. I need one as i'm soldering MOSFETs in to my PCB. So what solutions could I use to ground my soldering iron tip?


texts: AVRDude not reading fuses in Eclipse with USB attached STK600

texts:
I can successfully burn programs using my USB connected STK600 through Eclipse/AVRDude.

From the command line, I can read fuses (using: avrdude -px128a1 -Pusb -cstk600 -v), but when I click "Read Fuses" from within AVREclipse/AVRDude I get the following error:

  Programmer "stk600" could not initialize the target hardware.

  Please Check that the target hardware is connected correctly

  Reason:

  avrdude: initialization failed, rc=-1

Is this a bug or a setup problem?


texts: Closing a circuit when a GPIO pin is low

texts:
I have a GPIO pin that reports when an accessory is connected to the device: the pin is high when there is no accessory and low when an accessory is connected. When an accessory is connected, I would like to close a circuit between a lead (0.5V@2.5μA) and ground.
The GPIO pin is 0.4V@1.6mA when low and I believe around 3.4V when high (the spec sheet doesn't say). There is also a voltage source around 3.7V.
Would a transistor be appropriate to act as a switch? From my research I believe a MOSFET could work well (compared to BJT) as it is toggled with voltage and doesn't draw a lot of current, is that right? One approach I came up with is to use a differential amplifier to subtract the GPIO pin's voltage from Vcc:

simulate this circuit – Schematic created using CircuitLab

The op amp subtracts the GPIO pin's voltage from Vcc to flip the high and low states.
When the GPIO pin is low, the op amp applies 3.3V to the MOSFET's gate, connecting Vin to ground.
When the GPIO pin is high, the op amp applies 0.3V to the gate, below the MOSFET's Vgs threshold, opening the circuit.
Rin and Rf have the same resistance values so the op amp doesn't amplify the voltage and are 1kOhm so that there's enough current to charge the transistor gate in a few hundred nanoseconds.
R1 and R2 also share resistance values and are 100kOhm so the GPIO pin doesn't draw too much current and drain the battery.
Do these resistor values make sense? Do there need to be any diodes (e.g. to prevent current from flowing into the GPIO pin) or capacitors to make the circuit better?

Am I on the right track or is there a simpler way to accomplish the original goal of connecting Vin to ground when the GPIO pin is low?


texts:
I have understood how auto-ranging is typically achieved on a digital multimeter, but I'm having trouble finding an example of how (DC) polarity is handled. How does the meter know if a voltage is negative (to show a '-') and not fail from having a negative voltage on the ADC?

I figured it could possibly be done by having ground be in the middle of the ADCs range?
(eg by having values: 0 @-2v, 1024 @0v, 2048 @+2v)

So: How is polarity measured/detected in DMMs?
(pros and cons of different methods would be useful)


texts: Could anyone help me with this question I just want to know how the schematic looks like ?


texts: PIR Sensor triggering voltage not enough

texts:
I'm using a HC-SR501 PIR sensor.
The sensor is working fine, it outputs 3.3 V on motion detection.
But when I connect the PIR sensor to pin 2 (interrupt) of an Arduino pro mini,
the voltage output is only 0.289 V on motion detection.
The sensor is detecting motion, it's just not giving enough voltage.
How is this happening?


texts: selection of transformer for flyback converter

texts:
I am designing a flyback converter. Now, necessary parameters are as stated -

Vin(voltage to primary) = 17-32V,
Vout(voltage to secondary) = 12V,
Iout = 3Amps.

Now, based on the above requirements, I calculated the following parameters for the flyback transformer -

Pout = 36W,

Assuming 80% efficiency, Pin = 45W.

Iaverage = Pin/Vin = 45/17 = 2.647Amps.

Iavg 0 Ipk*(Duty cycle)*0.5. Where D - 50% duty cycle.
Hence-forth , Ipk(peak current) = 2.647/(0.5*0.5) = 10Amps.

So, V = LdI/dT => L = 17(ton)/dI = 8.02uH. The inductance o0f the primary coil.

Nr(ratios) = Nsec/Npri = 0.70588 => Nsec = (Npri)*(0.705).
Now, with the above values, I tried selecting a flyback transformer.

I am looking at the transformer PA3856.006NL.

Now, is my approach correct ? If so, in the transformer I have show, where is the turns ratio specified ?

Also, what is the actual advantage of have a dual output in the secondary ? Does it have to do with the current on the output and its effects on the transformer saturation current.


texts: How much overvoltage can an IC take when current is limited? What in the datasheet should I look for?

texts:
I'm using an MCP3304, which reads 0-5V, to read 0-10V via a voltage divider. But I'm worried that a voltage spike could damage the IC. I'm hesistant to add a zener, because it'll affect the input.

I've read that the Atmega has overvoltage protection clamps, capable of sinking up to 1mA. Is this generally applicable to ICs as well? (e.g. is the ESD protection similar, e.g. high voltage at low current?)

Example:

I'm using a current sense opamp which has a VREF of 10V, thus should internally max out at 10V. However, I am multiplexing the VREF, and noticed that my voltmeter measured a ~12V spike (which could easily be more, but being averaged out on the display) when the multiplexer changed channels (Vcc=20V, channels 0V/5V/10V). Thus I worry that there could be a spike on the ADC signal the multiplexer changes input.

However, since the voltage divider is high impedance (10k from opamp output to ADC), and the ADC is, as I understand it, also high impedance, I wonder if this spike is even going to reach the ADC signal.

What would be the best practice? And the question: how well do ICs tolerate overvoltage at limited current? Or is the answer simply: they don't, but the high impedance causes them not to experience the overvoltage spike in the first place?

simulate this circuit – Schematic created using CircuitLab


texts: Selection of filters for an AC/AC chopper

texts:
I am involved in designing an AC/AC chopper circuit as shown in the above image. The details are as follows

1) The switching frequency is 10Khz and the input voltage is 240Vrms serving a load of 22 Ohms

2) On the left hand side, the IGBT1 and IGBT2 are switching on and off simultaneously. The IGBT1 would conduct in the positive half cycle while the IGBT2 would be conducting in the negative half cycle.

3) On the right hand side,the IGBT3 and IGBT4 are to act as a freewheeling path for the current to flow when the IGBT1 and IGBT2 are switched off.

4) Without filtering, we receive chopped voltage and current waveforms at the input and the output

I am required to select input and output filters to be installed for my circuit. How ever my supervisor instructed me that I must install

1) A capacitor at the input for input filtering

2) A two stage RLC filter at the output

3) The resistors in parallel with the inductors are for damping the oscillations from the filter.

My question is

How can I go about selecting the values for RLCs. Are there any equations for selecting these values of R and L and C


texts:
I want to implement a 12v PoE+ PD power supply, and have settled on the LTC4269 for use in this application. Unfortunately I'm having problems getting my head around everything that is going on.

A demonstration circuit is available which provides 5v output (DC1351B) and I have one of these boards. I took some measurements of the startup and ripple at Vout in it's off-the-shelf state at various resistive loads (no load, 15Ω, 7.5Ω, 5Ω, 2.5Ω and 1.25Ω) - needless to say, they all look great.

Startup and Ripple at 1.25Ω / ~4A / ~20W.

I then modified it for 12v output (more details at the end), after which it failed to startup, or would fall over under both no load and 30Ω (~400mA / ~4.8W). It also made nasty crackling / clicking sounds...

This screenshot shows a failed start followed by a successful start. Note that this does not show the switching frequency, but a much lower frequency component.

I have a feeling that this is because of flux buildup in the transformer, but I'm really not sure, and this is what I'd like to understand with your help.

Unfortunately I didn't get any measurements of the transformer coil's switched side before my modifications, so I don't have a known "good" trace of my own, but a series from afterwards are below. I have ordered another board to keep as a control so that I can compare properly.

Yellow is Vout

3v/div, aiming for 12v

Blue is the switched side of the transformer's primary coil (pin 2/3 of T2)

50v/div, the PoE supply is nominally ~54v.

As time progresses, the waveform becomes increasingly distorted. Afterwards (in the last frame, when the switching stops) there is significant oscillation on the transformer.

A full video of this trace is available here (YouTube), and a wide screenshot of everything is here - there are significant transients later in the trace...

I believe that the yellow trace below (from the DC1351B quick start guide) is equivalent to my blue above. This implies that ~80v is not unreasonable, and more when the output current step occurs - unfortunately it doesn't show the detail I'd like.

Am I correct in thinking that this is flux buildup? If so, what should be done to avoid it? The duty cycle already appears to be quite low.

I'm still trying to fully understand the Forward Converter topology and the constraints that are in place. I've watched videos from The University of Colorado (e.g: here).

My modifications to the DC1351B demo circuit are below:

Replace T2 with PA2649NL

originally PA2431NL
from the EP13 series - datasheet
note reduced primary inductance from ~429.3µH to ~100.5µH (I suspect this is very relevant)

Replace R29 with 180kΩ

target switching frequency of 200kHz

Replace R20 / R33 potential divider with 13.3kΩ / 1.54kΩ

D21 has a 1.24v reference
~11.94v Vout

Replace R19 with 5.6kΩ - for 12v operation
Replace R8 with 2kΩ - for 12v operation
Replace C9 with 16v rated capacitor - for 12v operation

220µF low-ESR (0.1Ω) Tantalum

The full schematic (with annotated modifications and probe points marked) is below:

The transformer windings have gone from PA2431NL: (switched input on pins 1 & 2)

to PA2649NL:

Please note, this is largely a learning exercise, and I've not yet been in contact with LT.


texts: UART RX Interrupts Stop Working After a Few Seconds

texts:
I am writing a very simple program to validate that my board (STM32L4) can receive terminal (TeraTerm) characters via interrupt. The program runs as expected for the first few seconds (anywhere between 3 and 6 seconds). If I enter keystrokes into TeraTerm, the program prints both "yo" and "hi" after each second expires, until the 3 to 6 seconds are up. After this, it only prints "yo". Here is my code:
/*variable decl
volatile bool flag1 = false;
volatile bool flag2 = false;
volatile bool flag3 = false;
volatile static uint8_t c;
volatile static uint32_t isr_reg;

int main(void)
{
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock to 80 MHz */
  SystemClock_Config();

  /* Initialize LED */
  BSP_LED_Init(LED2);
  Console_UART_Init();

  NVIC_SetPriority(USART1_IRQn, 0);
  NVIC_EnableIRQ(USART1_IRQn);

  SET_BIT(console_uart.Instance->CR1, USART_CR1_UESM);
  SET_BIT(console_uart.Instance->CR1, USART_CR1_PEIE);

  printf("\r\n");

  while (true) {
      printf("yo\r\n");

      BSP_LED_On(LED2);
      if (flag1 == true) {
          printf("hi\r\n");
          flag1 = false;
          BSP_LED_Off(LED2);
      }
      if (flag2 == true) {
          printf("hola\r\n");
          flag2 = false;
      }
      if (flag3 == true) {
          printf("error\r\n");
          flag3 = false;
      }
      HAL_Delay(1000);
  }
}

static void Console_UART_Init(void)
{
  console_uart.Instance = USART1;
  console_uart.Init.BaudRate = 115200;
  console_uart.Init.WordLength = UART_WORDLENGTH_8B;
  console_uart.Init.StopBits = UART_STOPBITS_2;
  console_uart.Init.Parity = UART_PARITY_NONE;
  console_uart.Init.Mode = UART_MODE_TX_RX;
  console_uart.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  console_uart.Init.OverSampling = UART_OVERSAMPLING_16;
#ifdef UART_ONE_BIT_SAMPLE_DISABLE
  console_uart.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  console_uart.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;

  #endif

  if (HAL_UART_Init(&console_uart) != HAL_OK)
  {
      while(1);
  }

}

void USART1_IRQHandler(void)  {

    /* USER CODE END USART3_IRQn 0 */

  isr_reg = console_uart.Instance->ISR;

  if (isr_reg & USART_ISR_RXNE_Msk ) {
        flag1 = true;
        c = console_uart.Instance->RDR;
  }
  if (isr_reg & USART_ISR_ORE_Msk) {
      flag2 = true;
    console_uart.Instance->ICR |= USART_ICR_ORECF;

  }
  if (isr_reg & USART_ISR_PE_Msk) {
    flag3=true;
  }

  return;

    /* USER CODE BEGIN USART3_IRQn 1 */
    /* USER CODE END USART3_IRQn 1 */

}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    uint8_t c;
    if (huart == &console_uart)
    {
        flag2 = true;
    }
}

I have tried adjusting the loop interval to make sure that this issue is a function of time, not # of repetitions, and this has shown to be true. IE, when the HAL_Delay in my code is set to 100ms instead of 1000ms, the "hi" is printed 10x more during the first few seconds.
I have also tried observing the UART ISR flags in the debugger, and it looks like, after the first few seconds of ideal behavior, the RXNEIE bit stays set, but the RXNE flag never gets set (ISR doesn't get called either). This would lead me to believe that the issue lies with Teraterm, not my program, but I also know that observing interrupt-driven behavior on the debugger isn't always reliable.
Once more, the problem is that my program runs successfully for the first 3-6 seconds, then RX interrupts stop working. I am truly baffled as to what could be causing this problem. Any help/pointers would be appreciated!


texts: Vivado simulation ip_user_files/ipstatic filename conflicts

texts:
When integrating IPs in Vivado apparently some files are being copied to a ip_user_files/ipstatic directory. If two IPs happen to have the same filename, only one gets placed there, and then I see errors caused by one IP being compiled with another's sub-modules.

Is there a way to force Vivado to compile each IP separately with its own files?

Note: I've also posted this question on Xilinx Vivado forums with a minimal example.


texts:
I recently came across this circuit in which the oscillator capacitors are connected to VCC and not to GND. Researching I've read many comments stating that VCC and GND are at the same AC potential.

What does that mean?
Why are the capacitors connected to VCC and not GND even though the datasheet of the microcontroller states it?
What is that diode for?, never seen one before in that configuration.
Where can I find more information about these topics?

I also read about VCC being noisier than GND due to the line impedance.

This schematic is part of a DMP expansion card model 712-8. Values are not real, just placed components there for representation. Microcontroller is a Zilog z86e0812.

**missed a 100nanoFarad cap from VCC to GND near the diode.


texts: Is it possible to build MIDI to relays controller?

texts:
I have MIDI keyboard (MIDI interface, not MIDI through USB) and want to make it to control 12 colored lights (LEDs probably as incandescent bulbs may not be fast enough to follow the music), one per musical halftone. The LED should light when the key is pressed down and go off when the key is released up.

One of the approach would be connecting the musical keyboard to PC through adapter, write some software and add USB to relays controller to control the lights. This adds the complexity of the whole personal computer (ok, maybe laptop) involved. I would strongly prefer to have the independent device instead.

Is it possible to build such a controller without building and using a PC?


texts:
I took apart a very old laptop and the cells I found inside the battery were 17670 (the full name is SF US17670GR). I was planning on using them for a DIY power bank from aliexpress, but the industry standard of lithium ion cells is 18650.

So I want to know if I can safely stick 17670 cells into a 18650 power bank regarding both size and safe charging


texts:
I wonder if somebody could help me identify where I am wrong:

I have an analogue temperature sensor in my hand and cannot find out what kind of sensor this is.

It is a two wire crimped cylinder (diameter 6mm), used for domestic heating applications. It is equipped with a silicon cable.
I first thought it would be a standard PT 1000 but a resistance measurement yielded a value of about 1.8KΩ when I warmed the sensor with my hand.
The sensor has a positive resistance curve as the resistance was slowly rising when the sensor got warmer.
The resistance was measured with ambient temperatures around 10°C.
The sensor is an unused spare part, lying around for about 5 years and a  visual inspection yields no abnormalities.

So that causes me doubts:

I cannot find some standard, positive curved, temperature sensors with that values.
I doubt that the heater manufacturer used some tailor-made temperature sensors when there are cheap, established sensors around (like a PT 1000)
An measurement error seems unlikely as the difference to an established sensor type is way too much. Even an sub-par multimeter should not have that error-range.

Does somebody know a standard sensor with matching characteristics?


texts: Op-Amp based power supply, what powers the Op-Amps?

texts: I have seen some schematics of power supplies. They contain Op-Amps inside to implement negative feedback. I was wondering, hmmmm what powers the Op-Amps so they can actually work and implement negative feedback? Unlike diodes and transistors, the Op-Amps need power supply and that also would have to be a stable one. So how are Op-Amps inside a power supply powered up?


texts: Why isn't this decoder being inferred as a LUT?

texts:
I'm trying to model a stack which has push and pop operations.

entity stack_256x16 is
    Port (
        push : in std_ulogic;
        pop : in std_ulogic;
        dout : out std_ulogic_vector (15 downto 0);
        din : in std_ulogic_vector (15 downto 0);
        clk : in std_ulogic);
end stack_256x16;

In the architecture head:

type operation is (OpNone, OpPush, OpPop);
signal op : operation;

In the architecture body:

op <= OpPush when (push = '1' and pop = '0') else
      OpPop when (push = '0' and pop = '1') else
      OpNone;

I just want to decode the push and pop inputs into an operation.  One or the other can be set to do the expected operation.  If none or both are set, do nothing.

I would expect something this simple to be implemented as a LUT.  Instead when I open the elaborated design (RTL schematic view) I get this mess of muxes and logic.  Why is this happening?

I'm using Xilinx PlanAhead 14.7 and a Spartan 6.  The value of op is used as the selector into some muxes, which select and register various addresses & control signals.


texts: Would this lazy zero cross detector work?

texts:
Task: Design a ZCD for 230VAC to be interfaced to an atmega168, 5VDC.

The pictured optocoupler is SFH620A-3. I have on hand 1/4W E24 resistors. I am extremely lazy and want to go away with as little soldering as possible (thank God the opto has only four leads).

Let's suppose the line voltage varies from V_{min} = 200VAC to V_{max} = 250VAC rms.

$$ P_{input resistors} = \frac{V_{max}^2}{R_1 + R_2}$$
$$ R_1 + R_2 \geq \frac{V_{max}^2}{P_{input resistors, max}} = \frac{250^2}{0.25+0.25} = 125Kohm$$

We select R1 = R2 = 68Kohm.
$$ i_{in, min} = \frac{V_{min} - 1.65}{2 * R_1 *1.05} = \frac{198.35V}{142.8Kohm} =  1.39mA$$

From here on, using these or these calculations, we select 10Kohm or 15kohm for the output resistor.

Conclusion: minimum component count and price, borderline reliability, should work for a couple of years at least.

Would the schematic work? Would it be reliable for a couple of years of constant operation?

The output stage:

$$  i_C \geq i_{in, min} * CTR_{min} \approx 1.39 mA * 0.34 \approx 0.47mA $$

atmega168, page 302

$$ i_{leakage} \leq 1uA $$
$$ V_{IL} = 0.3 Vcc = 0.3 * 5V = 1.5V $$
$$ V_{IH} = 0.6 Vcc = 0.3 * 5V = 3V $$

If we strive to be below 1V for logic zero:
$$ i_C * R_{output} = 1V $$
$$ R_{output} = 1V / 0.47mA = 2.13Kohm$$

We select 2.4Kohm.

EDIT: implemented and tested. The input resistors get warm, but not hot.


texts: How can I fool an auto-calibrating capacitive touch sensor?

texts:
I have a MicroBot Push - looks like this:

Below the blue ring on the top is a capacitive touch pad and a TTP223-BA6 controller. Here's what it looks like under the hood.

It's a long story, but I need to be able to trigger that touch pad automatically (from an Arduino over USB, ideally). Interfacing over Bluetooth (the recommended way) isn't an option for a variety of reasons.

Today I tried placing a dime over that ring, then touching a small grounded wire to it. It worked! Until you don't touch it for at least four seconds, in which case this part of the datasheet appears to come into play:

  Auto calibration for life
  At low power mode the re-calibration period is about 4.0sec normally, When key detected touch and released touch, the auto re-calibration will be redoing after
  about 16sec from releasing key

After that magic ~4-16 second window, my solution no longer works. If I take the dime off and try to trigger it with my finger, it feels "hard" - I have to press extremely hard to trigger the sensor. Wait four seconds, and it's back to normal. It seems like it's "learning" the capacitance of the dime, which ruins my ability to control it.

How can I consistently fool the capacitive sensor on demand? Other questions recommend foil (which I've tried), but many are pointed toward capacitive screens, not these one-key sensors.

Is there something I'm missing here? Could I use an electromagnet, or capacitor in some configuration? There seems to be (relatively) precious little information out there - or I just don't know how to look for it!

I'd really like to design this as simply and as close to solid-state as possible. If there's a relay involved, so be it - but beyond that, I may as well push the button directly.


texts: Can I estimate Wi-Fi's power transmission in function of the amount of data transmitted?

texts:
For a specific device connected to specific AP. Can I estimate the differences in radiation power (mWh) depending on the data transmitted (2KB/s vs 200KB/s)?

If so, how?


texts:
I am trying to understand space vector transformation and I've gotten this far.
For a 3-phase system let's say that we have the following currents:
\$i_a = I\cdot cos\left(\omega t\right)\$ (Eq. 1)
\$i_b = I\cdot cos\left(\omega t+2\pi /3\right)\$ (Eq. 2)
\$i_c = I\cdot cos\left(\omega t-2\pi /3\right)\$ (Eq.3)
where I is amplitude, \$\omega\$ is frequency and t is time.
\$i_a + i_b + i_c = 0\$ (Eq. 4)
Now from what I understood space vector \$\vec{i}_s\$  is using the formula
\$\vec{i}_s = i_a + i_b \cdot e^{j\left(2\pi/3\right)} + i_c \cdot e^{j\left(-2\pi/3\right)}\$ (Eq. 5)
\$cos\left(\omega t\right) = \left[e^{j\left(\omega t\right)} + e^{j\left(-\omega t\right)}\right]/2\$ (Eq. 6)
\$cos\left(\omega t + 2\pi/3\right) = \left[e^{j\left(\omega t + 2\pi/3\right)} + e^{j\left(-\omega t - 2\pi/3\right)}\right]/2 \$ (Eq.7)
\$cos(\omega t - 2\pi/3) = \left[e^{j(\omega t - 2\pi/3)} + e^{j(-\omega t + 2\pi/3)}\right]/2 \$ (Eq.8)
Substituting (Eq. 6), (Eq. 7), (Eq. 8) into (Eq. 5)
\$\vec{i}_s  = I \cdot \left[e^{j\left(\omega t\right)} + e^{-j\left(\omega t\right)}\right]/2 \\
+ I \cdot \left[e^{j\left(\omega t + 2\pi/3\right)} + e^{j\left(-\omega t - 2\pi/3\right)}\right] / 2 \cdot e^{j\left(2\pi/3\right)}\\
+ I \cdot \left[e^{j\left(\omega t - 2\pi/3\right)} + e^{j\left(-\omega t + 2\pi/3\right)}\right] / 2 \cdot e^{j\left(-2\pi/3\right)}  \implies\$
\$\vec{i}_s  = I/2 \cdot \left[e^{j\left(ωt\right)} + e^{j\left(-ωt\right)}\right]\\
+ I/2 \cdot e^{j\left(2π/3\right)} \cdot \left[e^{j\left(ωt + 2π/3\right)} + e^{j\left(-ωt - 2π/3\right)}\right]\\
+ I/2 \cdot e^{j\left(-2π/3\right)} \cdot \left[e^{j\left(ωt - 2π/3\right)} + e^{j\left(-ωt + 2π/3\right)}\right] \implies\$
\$\vec{i}_s  = I/2 \cdot \left[e^{j\left(ωt\right)} + e^{j\left(-ωt\right)}\right]\\
+ I/2 \cdot \left[e^{j\left(ωt + 4π/3\right)} + e^{j\left(-ωt\right)}\right]\\
+ I/2 \cdot \left[e^{j\left(ωt - 4π/3\right)} + e^{j\left(-ωt\right)}\right] \implies\$
\$\vec{i}_s  = I/2 \cdot \left[e^{j\left(ωt\right)} + e^{j\left(ωt + 4π/3\right)} +e^{j\left(ωt - 4π/3\right)}\right] + 3\cdot I/2 \cdot e^{j\left(-ωt\right)} \implies\$
\$\left[e^{j\left(ωt\right)} + e^{j\left(ωt + 4π/3\right)} +e^{j\left(ωt - 4π/3\right)}\right]\$ should be 0 because of symmetry and we are left with:
\$\vec{i}_s  = 3\cdot I/2 \cdot e^{\left(-jωt\right)} \$ (Eq. 9)
Questions:

Do my calculations look correct? I am wondering why in http://people.ece.umn.edu/users/riaz/animations/sinvec.html \$\vec{i}_s\$ rotates in the positive direction. Shouldn't the minus mean that the space vector rotates in the opposite way?

Is the space vector a way to represent the 3 phase current in space because we can deduce the direction of the magnetic field from it and then tell the motor which way to point the phase voltages so that we get that specific orientation.

Relevant post:
https://www.reddit.com/r/ElectricalEngineering/comments/if5vxf/what_is_the_spacevector_for/


texts: How do I modify this schematic to be input/output?

texts:
J2 and J3 are audio jacks. The purpose of having 2 is because I want to be able to hear the original audio signal through an external speaker. I'm worried that this circuit configuration may introduce noise from the external speaker. If I add diodes, idk if it will disrupt the audio signal.

Do you guys have any suggestions?
You guys are awesome, thx in advance!


texts:
I need some help with the wiring for LED lights I'm placing in my crown molding and under cabinets.
The power supply and controller boxes will be placed on top of my kitchen cabinets at the start of the molding.  From there, I will need six 5m (16.4') strips running almost 100' total.
I am using:

LED strips: https://www.superlightingled.com/sk6812-rgbw-60ledsm-dc12v-10mmwide-digital-intelligent-addressable-led-strip-lights-5m164ft-per-roll-p-2400.html
Power Supply: https://www.superlightingled.com/mean-well-se60012-dc12v-600watt-50a-ul-certification-ac110220-volt-switching-power-supply-for-led-strip-lights-lighting-p-216.html
Controller: https://www.superlightingled.com/1224vdc-led-wifi-music-spi-dream-color-addressable-controller-works-with-amazon-alexa-google-assistant-p-1194.html
Signal Amp: https://www.superlightingled.com/dc524v-4-channel-spi-signal-output-data-signal-sp901e-amplifier-for-programmable-dream-color-6803-1903-1809-1812-2811-ic-led-light-strips-p-3125.html

Questions:

To avoid color changing due to low voltage, I know I must inject power from the supply to each LED strip.  My question is, do I need to inject power to each end of each strip or just the beginning of each strip?
Do I need to run dedicated wires from the power supply to each injection point?
What gauge wire do I need to use?

Any input is greatly appreciated. Thanks all!


texts: What is the industry standard reference designator prefix for a PCB mount EMI shield

texts:
Is there an industry standard electrical schematic reference designator prefix for a PCB mount EMI shield.  And if so, what is it?

I am creating component libraries for my CAD tool.  I created a symbol for the TE Connectivity 2118726-2.
https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=2118726&DocType=Customer+Drawing&DocLang=English

The CAD tool requires that there be some sort of reference designator prefix for the symbol.  The tool doesn't care what it is, but if possible I would like to follow what is common in other libraries.

A diode is "D".  A resistor is "R".  A shield is probably not "S" (because that's a switch), but possibly "SH"?


texts:
I have made a 3s lithium polymer battery pack that I am trying to make a charging unit for
My current charger setup is 3x AC/DC converters powering x3 TP5100 charger boards, each charger leading to one of the cells in the pack via the balacing connector.
I am using 3 chargers because these are plentiful for me and I would like to charge the pack as fast as possible while keeping the cells relatively top balanced. The idea behind the 3 converters was so all cells could be charged concurrently without shorting since each cell will have its own dedicated charger GND.
When I plug into AC, the 3 chargers power up fine but when I then connect the battery pack, only two of the chargers will change state. I have confirmed the wiring and the hardware are correct (per my plans)
Is there an inherent issue with this idea that I'm not aware of?
I would love to learn what is causing this and open to suggestions for improvement
TP5100 datasheet: https://datasheetspdf.com/pdf-file/1299994/TopPower/TP5100/1


texts:
This may sound a nonsense question for some of you but I was trying to visualize how an SMPS initializes. Below is a block-diagram taken from a particular SMPS datasheet: http://docs-europe.electrocomponents.com/webdocs/0e77/0900766b80e777c4.pdf

And before posing my question, I would like to make the assumption that all the electronic circuitry in an SMPS is DC powered by the SMPS’s DC output itself. So I assume there is no internal battery or such sort of thing.

If the above statement is true, here is my confusion as follows:

Let’s say the SMPS is switched on, and we started to observe what is happening inside the circuit at an extremely slow motion.
My logic says that first the AC input power is delivered to the rectifiers and then rectified to a DC voltage. So far so good.

But just after that moment, the electronic circuitry should start chopping the DC voltage with PWM to provide a high frequency AC for the transformer. But for that to happen the electronic circuitry should already been supplied with a DC voltage which were not created yet at the output.

How initially the electronic circuitry gets DC voltage is very peculiar and confusing for me.

Does anyone have an idea?


texts: I found this analog circuit at a surplus electronics part store. Based on circuit design, does anyone know what it might be?

texts:
The image attached is the circuit that I found. Could anyone venture a guess as to what this might do based on the components and design? My guess is that it's some type of audio signal modulator, given the 1/8th audio jack ports and potentiometers.

Details:

•The board has four 1/8th audio jack ports, two are larger than the rest and have "N" and "M" stamped on them.

•It has one common power input used by most laptop chargers.

•It has one pushbutton switch.

•It has two 85k potentiometers.

•It has one small port on the side with two leads, probably relating to power input or output.

•It has a TDA7360 Audio Amplifier chip, a BUK573 MOSFET, a HCF4066 Quad Bilateral Switch, a MC14013B Dual Type D Flip-Flop, a LF347 Op-Amp (TI datasheet here).

Numbers:
IS1, V2.1 REV 5A- Printed on the PCB

323276-004 REV B 5356 ASSEMBLED IN MEXICO- A label on the PCB

9544- Printed on bottom of PCB

That's all the information I have for now. If you think you know what it is but need more information, I'll attempt to disassemble the metal heatsink/housing to get a better look at the bottom. There are some amall logic chips visible on the obscured side.

Photos:

EDIT: It has been suggested that I add a picture of the bottom of the board. Here it is.


texts: Power Management Unit: How to consider limit to connect electronic component to power rail

texts:
I am a bit confused about the way to dimension Power Management Unit, and power rail for electronic system.

I understand quite well LDO and DC-DC in terms of voltage, but i don't understand well about current (although I know kirchoff law). Particularly I am confused about the maximum total current that a source can deliver/supply to load in the case of battery powered one. Normally, I suppose that at equal voltage we should add up current to get total current needed, but how to put this in face of battery. Does Lipo battery got maximum current it can deliver to supply many loads ?

Let's say we power a system with a Lipo battery 3.7V-4.2V, 1000mAH.

The system got:
- 1 MCU such as a MSP430 (http://www.ti.com/product/MSP430FR5969)
- one auxiliary chip such as RF chip (let's say CC1310, datasheet here : http://www.ti.com/lit/ds/symlink/cc1310.pdf)
- one module such as GPS (quectel L70, http://dl.roboticngo.com/uploads/Quectel-L70-Hardware-Design-V2-0.pdf )
- one another module such as GSM (quectel M95 http://www.soselectronic.com/a_info/resource/c/quectel/M95_HD_V1.0.pdf)
- one EEPROM such as ST one
- one TF Card such as SD CARD.

How do i verify this is achievable to supply all those chip and module with our Lipo battery and how do I build our power management architecture?

How do I verify this system can work properly and how would you organize the power rail in this situation and with which PMU ?

Thanks


texts: Why do they not make center tapped loadspeakers?

texts:
An early Australian solid state portable receiver manufactured by AWA used a 30 ohm centre tapper speaker that was directly driven by a push pull PNP germanium output stage.  The orthodox arrangement of the day was to use an audio output transformer which increased cost and reduced sound quality.

In these old times PNP/NPN output stage were onobtanium.  Matching 2 transistors of the same type is still much easier today.  This direct drive push pull scheme could give very low distortion.

Why is this not done today? Is a centre tapped voice coil difficult to manufacture? Does the reduced copper utilisation affect efficiency much when considering other factors like output transformer losses?


texts:
I'm interested to sample an AC signal in the range of 5kHz - 20KHz with the STM32L432KC microcontroller. This microcontroller has a hardware oversampling feature, i.e it can take the average of several ADC samples without CPU overhead, increasing the number of bits.

The ADC runs at full speed (5.33 MSPS) when in oversampling mode. With an oversampling rate of x64 I should get 15bits of resolution at 83kS/s although the ADC is only 12bits.

My questions about designing the ADC driver are:

Should I design the ADC driver so that it can drive the ADC at 5.33MS/s although my signal is only 20kHz? I ask because the ADC is a SAR type and the internal capacitor needs to be charged quick enough.
Should I design the ADC driver for 15bits although the ADC only has 12bits?

EDIT:

I attached a snippet from the datasheet + schematic of an ADC driver. My main question is how fast does the ADC driver need to be, the signal changes much slower than the ADC is sampling.


texts:
I am trying to implement a circuit that will sense a change in capacitance and reflect it in a change of flashing frequency for an LED.

I used NE555P timer and a 74LS393 counter. The circuit connection is as shown below:

RA and RB are in the Mohm range, C2 is 100nF, Csence is in the range of 10-100pF.
The output of the timer is connected to to the counter for frequency division (to make it suitable for the LED). OUT of the 555 timer has frequency of 242.4Hz.

I noticed a malfunction in the counter and I couldn't figure out the reason.
I probed the outputs of the counter using oscilloscope:

Out: 242Hz

Q0: 118.4Hz

Q1:59.7Hz

Q2: 59.5Hz (duty cycle 17%)

Q3:29.77Hz

I don't understand what can cause a wrong output at Q2?

Sceenshots are below:

Additionally, when cascading the two 4-bit counters in the IC, the second counter output is as follow:

Q0:14.8Hz

Q1:7.4Hz

Q3: Faulty signal

Q3 is shown below:

EDIT: I found that once I feed the two chips from different channels of the DC source (Different VDD and GND channels, though VDD is 5 V for both), the issue gets resolved.

However, I don't understand the theory behind what happened?


texts: How to turn a 0 to 5V square wave pulse into a -500mV to +500mV square pulse using just passive components?

texts:
Let me start out saying I'm not trying to build anything specific or useful here, just trying to learn the behavior of circuits.

Is it possible to turn a 0 to 5V square wave pulse into a -500mV to +500mV pulse using just passive components and where the only voltage source available is 5V?

What I'm aiming for is using some resistors and capacitors (and inductors, if necessary) where there's a capacitor divider network where half the square wave ends up below ground potential (presumably due to a discharging capacitor or two).

It's easy enough for me to use two capacitors to create a divider network to get a 0 to 500mv or 0 to 1V square wave, but what I've failed at is being able to bring the square wave below ground potential in LTSpice.

I know it's possible to simply change the voltage source parameters in LTSpice to pulse from -500mV to +500mV.  That is NOT what I'm looking for.  I want to know how to do it by adding components to a 0V to 5V pulsing voltage source.


texts: Low voltage DC over long(ish) distance on a small cable

texts:
I would like to power a small internet access point about 250m (800ft) away from my home (rural).

The wifi unit and modem draws about 16W max @ 12v. I had originally planned to power this via solar, but after some calculations of cost of the panel and batteries, and the physical size of the mounting required for the panels (very windy here) I started looking at other options.

Direct bury cable garden is really expensive here (New Zealand) but a box of cat5e - even the direct bury stuff isn't too bad.

I was wondering if I could run Cat5 the 250m, use all 4 pairs for power. I understand there will be a voltage drop along the run, and some wire resistance to consider - but could i use a higher input voltage and the regulate back to 12v at the remote end?

The box of Cat5 says each conductor is 24 AWG - about 0.5mm

I was hoping someone here could help be with the maths on voltage drop, current capacity etc

Is it workable or am I back to a solar option?

thanks dave


texts: Power supply destroyed when I connected positive line before ground

texts:
I have a few switching dc-to-dc power supplies (36V to 3.5V) which gets destroyed when I connect the positive input line before the ground.

When I connect the positive line first, some very quick connections-disconnections of the ground occur spikes at the input which destroy the power supply.
But, when the ground is connected first and positive line afterwards everything is fine. Even when I try to connect-disconnect the positive line quickly the power supply works just fine as long as its ground is permanent connected.

The load current is irrelevant to the effect.

That problem has been solved by adding a TVS diode in the input of power supply but I still can't understand what causing that effect.

How is that possible? Why don't I see spikes when the ground is connected first?


texts:
I accidently changed my ATtiny45 clock source to 128khz . After that I can't program it . I tried avrdude in terminal mode but it doesn't work .

>>avrdude -P COM4 -c avrisp -b 19200 -p t45 -t -F -u

(I'm using Arduino as ISP for programming)

How can I fix it ?


texts: How do I get gyro sensor data (L3G4200D) into degrees/sec?

texts: I've been using a gyroscope sensor for an Arduino project.  It's all hooked up and working but I have no idea what the units of the data it's giving me are in.  I try to spin the board in my hand at what should be roughly 90 deg/sec but I'm getting numbers from the gyro of 2000-5000 range.  I've just tried scaling it down and calibrating the scale factor by visually rotating the board 90 deg/sec.  I know there has to be a better way to do this.  I've been over the data sheet many times and I'm still not getting it.  It says the units are mdps/digit which I've never heard of before.


texts: Choosing resistor/capacitor for wiring microphones

texts:
I've been researching how to wire up a electret mic and found this to be very common. I can't seem to find any info on what values should be used. Most people use 1k or 2.2k resistors and 4.7uF caps.

The input power source is ~2.5v. The mic is a 3 pinned 4.4k, 1.3v, 50uA electret condenser. From my research, I assume that since DC signal has a frequency of 0, any size cap will work, but an undersized one will leak DC though, but that also depends on the resistor size. So... Any help is much appreciated, thanks.


texts: Measured doppler shift error biggest on direct flight on target

texts:
Following scenario:
There is a radar on a plane which emits a CW Signal and outputs the measured doppler shifts from the reflection of a static target.

I can see from the data, that the error of the doppler shift (error to theoretical doppler shift) is biggest when the plane flies directly onto the target (or away from it).

Is this normal?


texts: How to obtain the steady state response of the sampled periodic signal data?

texts:
Below the green plot Vin is 5Hz sine voltage signal from a function generator output sampled at 12kHz sampling rate:

The blue plot Vout is the processed/filtered data by using the following code in Python:

#Transfer function
fc = 1 # roll off freq
wc = 2*numpy.pi*fc
sys = signal.lti([1], [1/wc, 1])  # transfer function

#Output in time (Response of the filter to the input)
tout, v_out, x = signal.lsim(sys, v_in, time)  # output

And here is Vout in a more detailed view:

Basically I define a low pass filter transfer function  using:
 sys = signal.lti([ 1 ], [1/wc, 1]).

Then the Vout is obtained from tout, v_out, x = signal.lsim(sys, v_in, time)

So Vout is the filtered response of Vin.

If you compare the Vin and Vout in above plots, Vout looks like it is processed like in Laplace domain, that is to say Vout looks like it is both the transient and steady state response of Vin.

(This problem seen more obvious for a DC input; the output Vout becomes like a transient response of an RC filter)

Having the sampled data like in green plot Vin, how can we obtain a steady state response of such filter? Or at least close to steady state.


texts:
I recently obtained an electric typewriter and am trying to intercept the keyboard circuitry for an arduino project. The keyboard has a 17 pin ribbon cable that goes into a plastic connector on the main board. The holes are too small to fit any wires through and my soldering skills are not good enough to attach any wires to the solder points. The holes are a pretty standard spacing, and seem to line up spacing wise with the headers on my arduino.

My thought is I can solder a strip of header onto the board and just set the ribbon connector into the header. That doesn't solve my problem though, because I still can't connect extra wires to it. What I need is some kind of header strip that has an extra row of connectors to tap into the main set, or something like that.

Has anyone done anything similar to this, or have any tips, or know a part that may help me.


texts: Can an AM signal be picked up and decoded via software?

texts:
I'm trying to build an AM transmitter to remotely listen to sounds within a fairly small distance from the microphone (<30m). One thing I wanted to try was to use the microphone jack on my laptop to pick up the signal. The idea is that I could pick up all signals (my laptop can record up to 192,000 samples per second) and have the transmitter transmit at a frequency such as 48khz. I could then demodulate the signal in software. I figure this could reduce costs and it should be fairly easy to pick up RF frequencies through the microphone jack. The main issue is that the transmission frequency would be very low.

My questions are:

Is it practical to transmit audio at such a low frequency?
What can I expect in terms of signal quality?
What can I expect in terms of signal range at this frequency (the transmission power would probably be around 100mw)?


texts: How does this MOSFET-configured chaos circuit work?

texts:
I originally asked a question about this picture:
Circuit LTspice implementation not working

I am trying to understand this MOSFET circuit in terms of how it becomes a non-linear Chua's diode through LTspice. However, ultimately I realised I don't understand this at all.
How does this actually all work? The theory, etc. would be great, or just a step-by-step explanation.
The source of this:
https://books.google.co.uk/books?id=Tve6CgAAQBAJ&pg=PA17&lpg=PA17&dq=mosfet+in+chua+circuit&source=bl&ots=aOxjnewukF&sig=ACfU3U01aTtquge_KsePIF1yGUP0IbRDBw&hl=en&sa=X&ved=2ahUKEwjD2_CrvvvsAhWFs3EKHdxWCBg4HhDoATADegQIAxAC#v=onepage&q=mosfet%20in%20chua%20circuit&f=false
Original source: http://engineering.nyu.edu/mechatronics/Control_Lab/bck/VKapila/Chaotic%20Ref/Porfiri's/Biblio/Donoghue.pdf
It is an implementation of a chaos circuit inspired by Leon O. Chua.


texts:
I've just gotten one of these Teensy boards: http://www.pjrc.com/store/teensy_pins.html

I am trying to set it up using the basic keyboards tutorial. It is working correctly on Windows PC devices when I plug it in and press one of my buttons the proper key presses come through. But if I plug it into an Android device (Toshiba Thrive) I can tell that it recognizes it as a keyboard because it stops showing me the soft keyboard just as it does if I plug in a usb keyboard. But when I press my buttons no keypresses come through.

Does anyone have experience setting up a teensy board to be recognized as a USB keyboard on Android?

Edit so it turns out that it works if I select USB type "Disk(internal) + Keyboard"
But not with "Keyboard + Mouse + Joystick" I now suspect that the inclusion of joystick in this profile is what is causing it not to work. I've read that some android devices do not support input devices with joysticks.

So a followup question would be: Does anyone know how to remove the joystick functionality from the Teensy 2.0 board?


texts: High resistance (100Mohm) control using constant voltage or current source

texts: I want to control resistance (100Mohm) programmatically. I found on this site that photoFET can solve this issue by sourcing constant current.  From my understanding  FET can give resistance control over orders of 1 to 2Mohm. Apart  from this I want to drop 5000V dc(5kv) across this resistance. So what should I use? i.e Range of variation for this resistor needs to be from few 100 Megaohm to few kiloohms. A small amount of current 50 micro amperes flows in the circuit.


texts: how to resolve 64 bit address of remote xbee using Arduino xbee library

texts:
Does anyone know how to resolve the 64 bit address of a remote xbee (series 2) using the Xbee Arduino library (http://code.google.com/p/xbee-arduino) ?

The getRemoteAddress() public function of class ZBTxRequest returns only the the 16 bit address.


texts: switching a buck converter with transistor

texts:
I've got a bunch of shape memory valves (SMV) that require 1.2V @ 0.25A and I'd like to use a single buck converter and DIO signals from an Arduino to switch these  shape memory valves on and off. I've tried using an NPN transistor to do the switching, but this does not seem to work, perhaps because of the 600KHz switching frequency of the buck I used (OKR-T/1.5-W12-C). Is there a way I can make this work, perhaps by filtering the output of the buck, or should I go another route? I've previously tried a solution proposed here using a TLV62568P for each SMV, but never got that to work, so I hoped this would be simpler.

simulate this circuit – Schematic created using CircuitLab


texts:
When designing microwave amplifiers, stability is an important factor to consider. Stability is usually measured with the K factor. In a unilateral network, S_12 = 0, and this makes the K factor infinite.

However, we also know that being unilateral means Gamma_in = S_11, and Gamma_out = S_22. What if the network is unilateral, but either S_11 or S_22 are larger than 1? Will the amplifier be unstable despite being unilateral? Is this situation possible at all?


texts: If I have 2.4 amps on 5 Volts, how many amps am I using on 220v?

texts:
I know this sounds like a stupid question but I'm trying my best.

Anyways, I have a 2 meter RGB LED strip with 120 LEDs in total (60 leds/meter). I calculated the power consumption, which will be 2.4 Amps at 5 Volts but I can't figure out how many amps it draws at 220V.


texts: When is it required or permitted to sample below Nyquist rate

texts:
I have searched past questions and answers on this platform but none answers this question. A prof said it is possible to sample below Nyquist rate under certain conditions.
I will like to know, first, if it is possible to do this, if so, when?


texts: Sublime Text editor to develop ARM-based software

texts:
Until this moment I used Atmel Studio to develop software for AVR-based devices. Now I'd like to go to ARM Cortext M. Additionally I'd like to try codesign and version control (I still not experienced in those useful things yet).

I know that Atmel studio have the plugin to work with GitHub repositories. But I just acquired with Sublime Text 2 editor which is very nice to work with. It is also able to work with GitHub (as I have read in the Internet, I just not tried it myself) but I'm not sure that Sublime Text will be handy to compile GCC and ASM sources to HEX's.

Does anyone tried to use Sublime Text 2 as a source editing tool for such implementations? Or traditional IDE's will be much easier to work?


texts: What is the maximum current a human body can bear?

texts: Which causes death of human when a certain amount of current passes through him? And what is the maximum current a human can bear?


texts: I am using the PIC18F2550 and I wanted to know how much time takes between an event happens (e.g. ADIF)and the interrupt routine starts. In other words, how much time the "interrupt system" takes to change the MCU's state, saving all the registers and changing the Program Counter.