texts: How to perform a frequency response test in a tube amp output transformer?

texts: I have an output transformer, which is a clone from an original Fender 5e3 transformer, I would like to know how it's behavior in typical frequencies. How can I perform such test using instruments like osciloscope and frequency generator, is It even possible?


texts: Why MCP73871 lithium battery charger IC takes so long?

texts:
I'm working on a Microchip IC: MCP73871, a very small linear charger for lithium-based batteries. It has very nifty feature: a load-sharing system that gives priority to the load over the battery in order to avoid to continuously charge-discharge the battery.

The maximum charging current is 1A. How fast the battery is charged could be set on PIN13 "PROG1" by placing a specific resistor following this formula:

Ireg = 1000 / RPROG1

Ireg = mA

RPROG1 = Kohm

I tested a board featuring this IC by writing down current absorbed at the input and battery voltage over time (OCV) and it resulted the following charging profile. The battery is a li-ion 3.7V 6600mAh.

For 05 hours and 40 minutes the IC charged the battery at 1A. Then the battery voltage reached about 4,05V and current started to slow down.

Everything is correct: the charging profile is usually made of two stages:

Constant current stage
Constant voltage stage

Charging the battery at 1A when it is almost full could be dangerous and risky for battery life, this is clear. But the second stage is so slow. We are talking about 4 hours and it represents a big percentage of the full charging cycle time. And the average output power is so low.

Smartphones charge don't look to behave like this. They slow down a little bit over time but you won't never see them charging so slow. (In the graph you can see that the current slowed down constantly until a ridiculous 0,01A)

Is it possible that smartphone's batteries are declared 100% when they reach for example 4,05V, and not when they are 4,20V in order to get a shorter charging profile? What is the "state-of-the-art" technique adopted in the industry?


texts: Why is this TDS3034 scope complaining about "Low signal amplitude" for a frequency measurement?

texts:
I'm using a Tektronix TDS3034 4-channel oscilloscope to check a board. All channels are using P6139A 10x probes.  It's triggered off channel 3, which shows a fairly clean square wave, swinging between 0V and 3.3V.  Horizontal is holding steady with only a rare glitch causing some jitter.   Everything looks fine so far.

Except when I use the built-in frequency measurement, I get a plausible reading, but along with the text "low signal amplitude" on the screen.   If it's physically receiving  0.33 V at its input, shouldn't that be fine?


texts: Op-amp inverter followed by buffer. Why?

texts:
In a schematic I've been trying to understand I came across this sub-circuit:

It's an op-amp inverter directly followed by a buffer. VIN comes from a DAC in a microcontroller and this circuit produces a VOUT which is negative VIN. The op-amp is supplied by positive and negative rails (not shown here). So far so good.
But I don't fully see the rationale of using OA2 in this circuit. The only reason I can see is this: Without the buffer (OA2) a sudden load at VOUT would draw a current from VIN until the op-amp OA1 feedback adjusts (about 1µs). With the buffer (OA2) this is not the case anymore. Am I getting this right? Or am I missing something?


texts: USB Solarpanel read current with python?

texts:
I'd like to connect a small solar panel (2v 50ma) to a USB cable and measure the output on python. Now I was wondering if this would work and how to make it work.

How many volts can I send into my pc? And would pyUSB work for reading this?


texts: X-acto knife with soldering iron (Durable?)

texts: I know many people who like to use an x-acto knife on their soldering iron.  They use it to cut through plastic enclosures for their products.  But the question is, how long will the x-acto knife last with the heat?


texts: Using a shunt cap to create a delay - good idea?

texts:
simulate this circuit – Schematic created using CircuitLab

C1 is a decoupling capacitor. If the input of U1 is experiencing undesired phase shift, can a decoupling capacitor correct the issue?

credits to @Placeholder for rephrasing the question


texts: Signal extraction from Float Switch without disturbing existing circuit

texts:
I have a small coffe vending machine,and it has a floating sensor to signal when I run out of water.

I need to extract that information without affecting the existing circuit.

So, the sensor works as a switch, meaning it is closed or open.

My idea to extract the information in a circuit as follows,

Adding a small resistance in series in order to not affect the unknown circuit, that way a current in the resistant would produce a voltage that I can amplify and use to control a pump.

The problem I have is that I cannot measure any voltage drop across the resistance, and I'm reluctant to use a higher resistance because I could negatively affect the unknown circuit.

Any ideas?


texts: What is a phase difference between voltage and current?

texts:
I was reading the question here with some interest, because I am in the end stages of construction on a project that involves 16 solid-state relays. I'm using non-zero crossing type, because that's what I happened to find on a schematic by someone who completed a very similar project to mine.

The datasheet for my SSRs mentions that a snubber circuit is recommended, especially when driving inductive loads (which I am, since my loads are AC solenoids). I thought I understood that this is to give somewhere for the energy stored in the inductor somewhere to go if the SSR switches off right as the voltage peaks. When I read about ZC-type SSRs, I thought to myself, "self, that would eliminate the need for a snubber circuit, right?"

I then dug up a datasheet for the ZC version of the SSR I'm using, and I found this:

  Particular attention needs to be paid when utilizing SSRs that incorporate zero crossing circuitry. If the phase difference between the voltage and the current at the output pins is large enough, zero crossing type SSRs cannot be used.

As well, the snubber circuit continues to be recommended for the ZC-type SSR.

The phrase "phase difference between the voltage and the current" doesn't make sense to me. What does that mean?


texts:
I am building a very simple thermometer circuit on breadboard, based around the ICL7107. The 7-segment LED display I am using is made up of 3x TOD5261BE-N displays.

My intention was to make something nice and easy, just as an example circuit to show some kids at a local fair to try and get some interest in electronics. I have built circuits based on the ICL7107 and made a PCB for them and they work fine. Now I have built it on breadboard (I do not have time to design a PCB and order it/build it before the fair) and it will not illuminate the 7-segment LED displays.

The circuit is pretty much this:

The only difference is my input comes from the TMP35GT9Z which is similar to the LM35, and I am using a 0-5V supply. The V-, RefLo, InLo and Comm pins are tied to GND.

The oscillator pins are using a 100k resistor and a 10nF capacitor.

I have measured 100mV at he RefHi pin, and 212mV at InHi. Unfortunately, I do not have an oscilloscope at home so cannot measure the frequency of the oscillator pins.

Unfortunately, my laptop won't upload the pictures of my breadboard setup, or the pictures of me taking the measurements, so you'll have to take my word for the wiring being correct and the measurements accurate. I have double and triple checked the pinout and my wiring.

Is there some strange phenomena that means this IC won't work on breadboard or something? I have changed the oscillator components, tried a different IC and even tied the InHi to GND to try and force an output of all 0's but still the LED displays show nothing. If anyone can offer assistance, that would be great.

If pictures are needed, I can upload some tomorrow.

EDIT

Now able to upload pictures! First one is the breadboard set-up (I tried to keep it neat, so apologies for the mess of it! I'll tidy it up once its working!):

The next image is when I have turned it on (The last 2 digits are connected directly to GND via 470 Ohm resistors. This does 2 things. Firstly, proves the displays are working and secondly it shows it is a Thermometer as it will read °C:

With this, I find it strange that the -1 is being displayed, which are connected to pins 19 and 20.

These are pictures taken of measurements (directly on the IC pin). The first os of the reference (100mV) and the second is the actual input (212mV)

Just in case it was the clock line (as that is the only thing I cannot measure as I don't have a scope at  home) I made a little 555 timer circuit and put it straight on pin 40 which I believe would be correct if you had an external clock. This still didn't do anything though.


texts: Tantulum cap issues: Xray die construction misalignment & dirty marking

texts: I'm having some tantalum polymer capacitor die misalignment and physical dirty marking problem. I hope that I can get any advice from someone; whether this can impact the functionality of the component? Can this be acceptable? How can it happen?


texts:
I've just learned about the surge protection device (SPD). As I was reading about its connection in a three phase line, I came across this scheme:

I understand that the SPD's are there to limit the line tension in respect with the PE reference, but why isn't it connected to the line neutral? Each phase's voltage should be measured like this in my mind:

Also, isn't the protective ground meant to protect things that are outside the circuit? like other electronics, people etc. against accidental contacts?. How can you intentionally connect the circuit with a reference that is only there for safety?


texts:
I have a design which expects a TTL level square wave from a radio reciever which is fed into a microcontroller. There is some TTL level noise as no encoding is done on the transmit end. I was wondering if anyone had any pointers on how you could decrease the noise in software? (I understand there are a number of hardware solutions, but I am interested more in learning) I am not looking for anyone to solve my problem for me, just for some advice.

Names/articles/topics would be great!


texts: Designing an Over-Current Protection Circuit with Delayed Reset

texts:
As part of a larger design I am trying to monitor current through a wire and cut it off if it exceeds a threshold. After the current has been turned off it should remain off for a minimum time period and only turn back on when a reset button is pressed.

The circuit below is my current design idea. I'm looking for any reason why this wouldn't work, as well as hearing any suggestions for better designs (excluding software solutions).

The current sensor will output a voltage proportionate to the current through the wire, causing the op-amp to output a high signal when it exceeds a REF voltage.
This will trigger the monostable circuit to produce a high signal for a set period, setting the data pin low and turning on the Latch Enable (LE) to read in that low.
The high-pulse also switches the Output Enable (OE) pin on the D-latch, the Output goes to high-impedance and the NFET is turned off by R3. (Possibly unnecessary but it doesn't hurt)
Once the pulse has finished the LE pin is driven low and the data pin is high. I think I might have to introduce some small delay for the data pin here so that the D-Latch doesn't read in the high-going data pin but instead keeps its value latched at low?
The OE pin is released again and the D-latch should output its latched-to state of low. Once the button is pressed the data pin is read again and the output switched on, allowing current to flow.

simulate this circuit – Schematic created using CircuitLab

EDITS:

Added R5, C1 to provide a delay of 2ms at data pin. This is the time to charge from 0 to 2V (minimum V_IH @ 3.3V supply) with 3.3V applied. Data pin must be stable for only a few ns after LE goes low so this should be plenty of headroom

Added R6, R7 to provide 25mV of hysteresis for the op-amp which corresponds to a change of 100mA through the load


texts:
Normally a current would take a simpler route, hence why a resistor in parallel with a short gets no share in current. Again two equal resistors in parallel get equal share in current.

These questions just crossed my mind:

What happens when you have two shorts in parallel? Do they get equal share as well?
Again, what happens when I place an inductor in parallel with a short? Would the inductor become a short (eventually)? You know how inductor behave under DC.

What others have to say?


texts: need amplifier circuit for load cell output(mv) to milliamps, for giving input to the PLC

texts: We need to convert load cell output (millivolt) to (4-20)milliamps, to give input to the PLC. Is there any IC Or circuit diagram to directly convert millivolt to milliamps?


texts:
I am creating an open source dive computer (diydivecomputer.com) and have been looking for the simplest way of managing the battery which consists of three functions: 1) managing the charging of the battery, 2) Regulating the output to 3.3v and 3) providing accurate battery level to the processor (gas gauge).

I have not found any solutions that can do all this in one chip or for that matter, less than three (one for each of these functions). Does anyone know of a good, simple solution?  I want the device to worn on the wrist so board space is at a premium.  So far I am looking at Microchip's MCP73831 for charging, the TI's TPS61201 for regulating and TI's BQ27000 for "gas gauge" functionality.  If you can point me in a better direction, I would appreciate it!

FYI: the device will use a 1200mAh Li-Po and use about 40ma while operating.


texts:
I find a bit of confusion on the web about the use of the PLL. Sometimes I read that, given a certain input signal, it is used to generate a signal whose frequency is N times that od the input one, when N is chosen by us.

If we look at the following image, the previous statement means that the difference between the phases of the signals that enter the phase detector is constant in time.

Sometimes I read that a PLL allows to get that the input signals of the phase detector have the same phase, that means that their phase difference is 0 (so it is a stricter condition).

What does the PLL exactly do?


texts: High Pass Filter configuration with diodes and electrolytic caps?

texts:
I'm quite new to electronics and I'm trying to make a high pass filter to get rid of some DC component of a signal. For that, I thought of using a capacitor along with a resistor in the usual HPF configuration (values are generic):

simulate this circuit – Schematic created using CircuitLab

However, since my signal is positive and negative, as far as I understand I can't use an electrolytic capacitor since they are polarised. To make up for that, I thought of the following configuration (it is quite simple so if it works I guess it may be quite standard), but since I haven't designed many circuits I have no idea if it works or not:

simulate this circuit

Is this any good?
Thanks in advance!


texts: How to read timing diagrams: ak4554 audio serial interface

texts:
As a newbie I struggle to understand interface timing diagrams of  AK4554.
I am asking this particular example but I believe your answers will enlighten me about how to read any timing diagram.
It is a audio DAC, and here its datasheet: http://www.akm.com/akm/en/file/datasheet/AK4554VT.pdf

In this datasheet it is written that LRCK is clocked at sampling frequency. And data-in is 96 times sampling frequency. The device is 16 bits so what should I do to data-in in rest of 80 cycles? In the datasheet it is not written anywhere that the data is latched at certain time... Should I repeat the data or am I allowed to float? Can I do other tasks in my processor during that time? What is the easy way to produce sound messages while struggling with other tasks in simple microprocessor-peripheral systems?


texts: Why can the drain of a transistor be used as an output port in both OTA and TIA?

texts:
In OTA, the output is current. It should deliver a constant current to the next stage. So the output impedance of an OTA should be high. As the impedance seen at the drain is also high, it is understandable that the drain would be chosen as the output node of an OTA.
On the other hand, for TIA, it should give a constant voltage to the next stage. So the output impedance of a TIA should be low. However, as mentioned previously, the impedance at drain is high, so I don’t understanding how the drain can still be used as an output port in TIA?
Thanks


texts: For IIR low-pass filters, what design provides the least amount of phase shift in the pass band?

texts:
Given all the possible design options for IIR filters one could consider (e.g. Butterworth, Chebychev, inverse Chebychev, elliptic, Bessel, etc.) which design provides the least amount of phase shift in the pass band?

Here I'm assuming among the various designs considered, and for fair comparison that filter order and cutoff frequency are the same.


texts: 555 timer monostable operation not so stable

texts:
I'm experimenting with a bunch of Texas Instruments NE555P IC's that I bought recently from Amazon, I made a basic monostable operation circuit on a breadboard with the following schematics

simulate this circuit – Schematic created using CircuitLab

When I push the button the 555 gets triggered and the LED lights up for few seconds before going off, pushing it again would repeat the process. This is the expected behaviour indeed, however there are two issues I'm experiencing with this circuit.

The first issue is that closing the switch doesnt always trigger the timer, what happens instead is that the LED goes on for only a fracture of a second, I sometimes can overcome this by holding the button down for a second or so and it will then trigger normally after releasing the button.

The second issue is that the trigger duration is larger than \$ 1.1R_{1}C_{1} \$, I tried several different resistance values for \$R_{1}\$ and found out the duration to be about \$1.32R_{1}C_{1}\$ instead (in the circuit above the trigger lasted about 7.40 seconds where it supposted to be 6.16 seconds).

What's causing this erratic behaviour? and why the trigger duration is not consistent with \$1.1R_{1}C_{1}\$?

Heres the breadbord layout:

Last thing I would like to mention is that while testing a 555 IC got zapped (it stopped triggering all together and started heating up), what could have caused that? I used insulated tweezers to avoid ESD damage.


texts: Connector pins protection from overvoltage

texts:
I have a connector which has the following lines:

12V
3.3V
GND
SDA (I2C)
SCL (I2C)

The connector might get wet with water and I would like to protect the circuit from the resulting over-voltage in case the 12V line gets connected to the other lines.

Based on this schematic from this question Why is a resistor needed in zener protection circuit?:

I've designed this connector using a 3.6V zener diode and 330Ohm resistors. I don't understand why R1 and R2 are required and I've removed them in mine:

The connection would look like this:

Would this solution protect the connections from the 12V line? Is there a better approach?


texts:
I am trying to design a one milliamp current source (Howland current source) with a precision of +/- 1 uAmp.
The current source will be used to measure temperature with a 3 wires RTD sensor (H-T-01-12-00 from Honywell).

I did look at several voltage to current converter from Texas Instrument and Analog Devices using a pair of Op. Amp. and Instrumentation Op. Amp.
Example   :
INA128 & OPA177
INA114 & OPA131
LT6370 & LTC2057
I did some simulation with the tools provided by those manufacturers, but i was unable to get the required precisions, i was far from the expected result (I may did it in a wrong way).
I am not familiar with the behavior of those Op Amp. and Inst. Op Amp. and i do not have measurement tools to check.
Once the circuit board created, except the functionality, i won't be able to check the accuracy.
Could you please provide your remarks and suggestions on the components to be used, especially for U1, U2 and U3 (in DIP or SO package) or on the schematic itself ?

Thank you.
Additional information
I am targeting a 0.1°C precision.
According to the sensor's datasheet, i understood that the best precision i can expect is 0.3°C, but the sensor can be changed in future developments.
The circuit board is supplied with a single +5V voltage source.
Two current sources are used to supply the sensor.
An analog switch (MAX4662) is used to switch the current from one RTD termination to the other RTD termination.
The temperature is obtained by doing an average of two successive measures from two switched currents flow, 160 measures per sec.
The voltage accross the resistor RREF (1.1K) is VRREF = 2.2V (with 2mAmp current), used as Ref. for the DAC (LTC1864).
The temperature will vary from -30°C to +300°C (used in differents applications and environments).
Across the RTD, with a milliamp current, the voltage will vary from 0.088V to 0.212V  (according to the sensor's datasheet and the Callendar-Van Dusen function).
The output of the Inst. Op Amp U3 (Gain = 10) will vary from 0.88V to 2.12V


texts: Is hard real time possible with Ethernet technology?

texts:
If I use EtherCAT to control a motor -- say I use RTnet + SOEM to control a servo drive using EtherCAT connectivity -- and the servo drive both controls and reads sensor value, than: is it necessary to use an RTOS to make the whole system hard real time?

For example, right now I'm using Xenomai patched Linux as the RTOS, but is this necessary if I use RTnet to control the motors?


texts: How can I switch this audio jack, using its own mechanical switches, without creating feedback?

texts:
I've spent a few hours inside my car radio and I've found that when I short a hidden pin called AUX-ON to VCC, I can pipe music right into the it and it's treated like a regular AUX input. Great success.

Now, I have a switched jack that I'd like to use to short VCC to AUX-ON whenever I plug in a cable. The jack I'm using is Radio Shack 274-0246, the diagram is below. I can't figure out any way to do this without having the potential of grounding the audio to the vehicle ground (which could, I assume, distort quality) or without having the potential of sending 12v back through the audio cable into the phone. I know there MUST be a way to do this with a semiconductor or two, but I don't even know where to start. All I know is I need to pass current from pin 2 to 3 (or 4 to 5) and when that current stops (the jack mechanically separates the contacts when plugged in) then VCC can go to AUX.

EDIT: I forgot to mention, the unit is expecting balanced inputs, however.. I don't think I've ever seen an ipod or phone with balanced outputs. Should that be taken into consideration with this circuitry?


texts: How and when does the kelvin measurament actually works?

texts:
I know that 4 - wires method uses 2 wires for driving current throught ammeter and measure current values. So, resistivity wires will be removed from the equation. Ammeter wires resistance has no effect on current measure because wires resistance and ammeter are also serially connected with the source supply.

Voltage on Subject Resistance is measured by a parallel connected voltmeter (2 wires more). As it has a big intern resistance it has no significant current passing through this device. So, voltimeter resistance wire will has no effect to the voltage measure, but potential contact with Subject Resistance terminals. These two potential appearing in contact vA and contact vB will be cancelled when source supply polarity changes and two values of ammeter and voltage will be took and added in a expression like this:

V+ = vA + I·R -vB
V- = -vA + I-·R +vB
V- + V+  = (I- + I+)·R --> vA and vB has been cancelled because they are signed opposed

By the way that explanations I' ve found it seems to say that wire length doesn' t matter. But I' m almost sure that length and connector position does.

But the fact is that I don' t find explanations where to see whether this principle is only true when:

voltmeter and wires amperemeter have the same distance respect Resistance Subject. Does it works correctly if 4 wires have different length?
must the ammeter and voltmeter two both contacts be connected at the same place? Does it works if ammeter connector has a distance between ammeter connectors and voltmeter connectors?
Could there be some distance between the connectors and Subject Resistance terminals? or must they be connected close to Subject Resistance terminals?

Could anyone clarify when the 4 wires method will totally cancel contacts potential and wire resistance in these three prior indicated situation?

Some images as example of distances, wires and connector position possibilities:

If I need to extend subject R terminals by signle wire I will get this circuit with 2 new resistances -R10 and R9- at the ammeter net shared with voltmeter one too:

So they R9 and R10 will experiment a potential because of the current passing through the left net. So I think that being connector the more closer to the subject R terminals is a condition. If not, make me know.


texts: OUTPUT pin is not going LOW in 555 timer IC

texts:
I was working on a simple monostable IC project and I came acroos this problem. When the switch is closed which triggers the pin 2 and sets pin 2 on low logic OUTPUT goes HIGH. As per my settings of C and R it should stay HIGH for nearly 10s. I am using C=82uf and R=120K which gives approx 10s. But, Instead OUTPUT is not turning off and it stays HIGH till I disconnect powersupply.
Here is the schematic.
All grounds are common. And pin 8 is Given VCC +5v. I can't figure out the reason. in pin 5 mostly all of the circuits I have seen sets capacitor of 10nf But, I don't have that so I thought 100pf will work. It may cause some timing malfunction But, I can find my way around that by adjusting R Value. If 10nf is must and won't work other than 10nf then please let me know...


texts:
To protect a 3v/3w (mppt 3.2v/996mA) solar panel from back current (dark current) I would like to use a mosfet P-channel as it seems to limit voltage lost to 0.
Could you advice which one should I choose?
I have found the following one:
Drain-source voltage -16.5V
Drain current -1.25A
Power 1W
Gate-source voltage -1V
On-state resistance 1.5Ω
Thanks in advance for your help
Andrea


texts: LDO, linear regulator or DCDC buck converter

texts:
I would like to power an ESP32 in my car, so the input voltage is between 11 and 15v, and the output voltage should be 3.3v to power the Arduino board.

I thought that LDO were only for low dropout voltage. However, I saw that for example, the esp32 is powered with the usb 5v interface through a LDO ASM1117 3.3v. So the dropout voltage is around 1.7V...

Is this normal? What is the highest dropout voltage usable with LDO or linear regulator?

In my case, I think that the only way to power the esp32 is to use a buck converter, but if you have some solution with a linear regulator, I am interested for my understanding!


texts: What happens if we force a voltage on Vbe of a bjt transistor

texts:
I'm wondering what happens in a BJT transistor if we force a voltage bigger than 0.7V on Vbe.

A colleague of mine said that if we put on Vbe, let's say, 5V the transistor would be saturated.

I haven't seen the case in question but I suppose that happens if Vbe > Vce.

Still is there any harm to the transistor if we force a bigger voltage than 0.7 there?


texts: Esaki effect implementation on simple oscillator circuit

texts:
I am trying to learn basic oscillator circuits with the help of this link.

But when I connected the components, my LED is not blinking. Rather, it is giving bright light.  The components I have used are 1K resistor 18V battery 200uF capacittor 2N2222 transistor and LED with 100 ohm resistance.

Here is the circuit:

From above page:


texts:
I am trying to run AD9833 frequency generator to have a smooth continuous frequency change. I have run AD9833 module as in here using the code below as found in internet and it works fine and the waveform and frequency displayed on the oscilloscope are as desired.

    #include <SPI.h>

const int SQUARE = 0x2028;
const float refFreq = 25000000.0;           // On-board crystal reference frequency

const int FSYNC = 10;                       // Standard SPI pins for the AD9833 waveform generator.
const int CLK = 13;                         // CLK and DATA pins are shared with the TFT display.
const int DATA = 11;

void setup() {
  SPI.begin();
  Serial.begin(9600);

  }
void loop() {
   if(Serial.available())
 {
  Serial.println("Serial is available");

  float freq = Serial.parseFloat();
  Serial.print("value to specify : ");
  Serial.println(freq);
 AD9833setFrequency(freq, SQUARE);
  }
}

// Set the frequency and waveform registers in the AD9833.
void AD9833setFrequency(float frequency, int Waveform) {
  long FreqWord = (frequency * pow(2, 28)) / refFreq;

  int MSB = (int)((FreqWord & 0xFFFC000) >> 14);    //Only lower 14 bits are used for data
  int LSB = (int)(FreqWord & 0x3FFF);

  //Set control bits 15 ande 14 to 0 and 1, respectively, for frequency register 0
  LSB |= 0x4000;
  MSB |= 0x4000;

  WriteRegister(0x2100);
  WriteRegister(LSB);                  // Write lower 16 bits to AD9833 registers
  WriteRegister(MSB);                  // Write upper 16 bits to AD9833 registers.
  WriteRegister(0xC000);               // Phase register
  WriteRegister(Waveform);             // Exit & Reset to SINE, SQUARE or TRIANGLE

}

void WriteRegister(int dat) {

  // Display and AD9833 use different SPI MODES so it has to be set for the AD9833 here.
  SPI.setDataMode(SPI_MODE2);

  digitalWrite(FSYNC, LOW);           // Set FSYNC low before writing to AD9833 registers
  delayMicroseconds(10);              // Give AD9833 time to get ready to receive data.

  SPI.transfer(highByte(dat));        // Each AD9833 register is 32 bits wide and each 16
  SPI.transfer(lowByte(dat));         // bits has to be transferred as 2 x 8-bit bytes.

  digitalWrite(FSYNC, HIGH);          //Write done. Set FSYNC high
}

But everytime as I was trying to change the frequency value, the oscilloscope reading shows a 'flatlines' between every frequency changes. As I was inserting the frequecny value of 111.11Hz, it shows an acceptable value of 111.13Hz. But the problem is when I was trying to change the frequency to let say, 222.22Hz, the oscilloscope showed a 'flatline' a moment before it shows the waveform of 222.24Hz. If I input 333.33Hz, it 'flatlines' as well before showing frequency of the desired 333.33Hz. My desired is without the 'flatline', the frequency change smoothly from 111.11Hz, 222.22Hz and 333.33 Hz.

Is my desired ofr continuous smooth frequency change is can be done or the flatline is hard-coded and cannot be done?


texts: Supporting SMT electrolytic capacitors in high vibration environments

texts:
I recently experienced a situation where an engine ECU failed. The post-failure analysis showed that two capacitors had broken loose from the board due to stress from vibration. I have replaced the capacitors, but without any changes, I assume that this will happen again. How can I provide proper mechanical support for these?

Edit: the capacitors are Nichicon UUT1V220MCL1GS


texts: One-Shot circuit has problems with slow voltage ramps

texts:
I'm using this circuit:

simulate this circuit – Schematic created using CircuitLab
The circuit is powered by "24V" , "24V ENABLE" is the trigger. The circuit should act like a one-shot signal (or single impulse) that is OPEN for about 100us (between NODE1 and NODE2) when a transition from 0V to 24V occurs on ENABLE.  It should then stay closed for the rest of the time.
When thr trigger was generated by a push button on the bench all worked well. Now that I've moved to the real application that uses an opto-relay to trigger the circuit, the circuit doesn't work for values lower than 100nF, this mean impulse time longer than 500us.
This happens because the voltage on the opto-relay rises very slowly and this rising speed is comparable to C1 charging speed. What happens is that M1 never triggers. With higher values of C1 the charge slows, but also the impulse time that should not exceed 100us.
Do you have suggestions on how to avoid this applying changes to this circuit?


texts:
Could anyone advise about derivation of Marchand Balun Equations ?

Note: Screenshot below is taken from paper :

New Design Formulas for Impedance-Transforming 3-dB Marchand Baluns


texts: High voltage DC power line for batteries

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I am planning to install a photovoltaic plant of 1000Wp on the roof that puts into 10×12V batteries in series to have 120V. This way can guarantee a low section of the cable, if I had a 12V power line I would have a big one.

I want to install DC plugs 12V and 5V to power as much stuff as I can.

To step down voltage 120V -> 12V I need a DC DC converter on each plug but thinking to something cheaper I am wondering if it is reasonable a voltage divider instead of DC DC step down converter.

What do you think of this solution?


texts: The common terminal of the transistor configuration is also the GND of the circuit, right? I get it that emitter is GND but how is it possible for NPN transistor that base or collector is GND?


texts: What practices would improve this scenario for the power transfer

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As a part of a measuring project by a mobile phone on the top of a 100 meter tall mast, the mobile phone will be powered by 5V DC of a DC-DC converter output where its input voltage is 12V DC on the ground.

simulate this circuit – Schematic created using CircuitLab

There are many reasons to use DC-DC converter but some of them are power efficiency and isolation of the input and output grounds which I guess is good for long distances.

So the converter and the mobile will be in an enclosure on top of a mast. In terms protection such as type of enclosure,  ESD, lightning protection ect, what type of extra interface would be a good practice along with the diagram above? I marked the terminals. And does the 100 meters cable need to be twisted and shielded? Which specs should I consider to look for a DC-DC converter for such application? Do  most of them have isolated input output grounds? Does anybody have experience with similar scenario?


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I'm looking to build a very basic computer around the Z8180 MCU, I'm looking for a schematics to get a start.

I got a bit experience with fundamental electronics, but I never dabbled with any type of CPU/MCU before.

Any tips to get started is very appreciated.

I might add that the choice of processor is purely sentimental and there fore very definitive , Z80 it has to be, even if alternative is both better and simpler :)

Thanks in advance !


texts: Setting ground potential in nodal analysis matrix form

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I have a general question concerning the matrix formulation of nodal analysis.
I investigate a large resistor network with tens of thousands of resistors and some independent current sources.

I set up the conductance matrix as usual with the positive sum of all conductances leading to a node on the main diagonal, and the negative conductances between nodes on the corresponding off-diagonal positions.

Naturally, the conductance matrix is singular as the reference potential is not chosen, i.e. I have not defined 'ground'. This leaves me with an infinite amount of solutions to the linear equation system. For very large matrices, this seems to be a problem for my software, so I'm wondering how I can easily fix one of the potentials to 0 V and maybe solve my issue.

So, I have already constructed a large sparse conductance matrix and set up the current vector. How do I fix one of the unknown voltages?


texts:
I designed an analog board using a ±12V switching power supply as the input source.
Now I am wondering to desgin the 2nd version of it and enhance some aspects including eliminating a few tens mV noise
that I know that a part of it is due to switching power supply.
There are two solutions I think of them:

Using transformer, rectifier, caps, and then linear regulator to produce ±12V.
Using a switching power supply with ±15V output (or higher) and then linear regulators with ±12V output.

The first solution is common and straightforward. But does solution 2 make noise less than previous board?
if yes which solution will make less noise, solution 1 or 2?
If my question was not clear, please Assume that I definitely know that the noise comes from the switching regulator.


texts: Help me understand this voltage to frequency converter circuit

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I got the schematics for a  voltage to frequency converter (VFC) from https://www.multisim.com/content/6L...amp-comparator-voltage-controlled-oscillator/.
I tried it in TINA-TI and it works.
Can somebody explain how this circuit behaves?
In particular, it is not very clear why R4, R8 and R2 have to be half of R1. Only then the circuit oscillates. I understand that ratio helps in maintaining the symmetrical currents during charging and discharging period. But why does this circuit not work for asymmetrical currents?


texts:
With a 5.8 Ghz WLAN device, operating in the upper UNIII band of 5745-5825 MHz...
Is it required that, if the device is using a standard 20 MHz-wide 802.11 channel, that you can only be centered on the pre-defined frequencies of ch149 (5745 MHz), ch153 (5765 MHz), ch157 (5785 MHz), ch161 (5805 MHz) or ISM Band ch165 (5825 MHz)?
Is it not allowed to set the center of the 20 MHz-wide operation channel to, say, ch155 (5775 MHz)?
I would think that as long as you are within the 5745-5825 MHz band, it shouldn't matter what the center frequency is.
I'm being told that with a 20 MHz device, you can only use those 5 pre-defined channels as their center frequency. What about devices capable of 10 MHz and 5 MHz wide channel use?
Thanks in advance.


texts: Determining the input capacitance for a SMPS

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I'm attempting to layout a SMPS using the LTC3703 chip, however the datasheet doesn't talk about the AMOUNT of input capacitance, just that it be low esr.  However, it does talk about "bulk capacitance".

What I'm not sure about is how I figure out how much total capacitance I need.  Is there a relationship between ripple current and capacitance?


texts: Why can't I find SOCs with integrated memory?

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I am looking for SOCs with integrated memory to avoid having to worry about design of a memory bus for, what is supposed to be, a pretty low power application. I'm looking for something like the raspberry pi where the ARM core and the memory are integrated into a single chip, but my searches have yielded nothing. In fact, when I look up the SAMSUNG K4P4G324EB processor that the RPi actually uses, all I get on Samsung's website is a big set of applications processors with off chip memory.

Does anyone have any resources or locations I can go to get a decent ARM SOC with around 512MB of integrated memory?


texts: Distance or length specification (or limit) of Arduino IO devices

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I am using an ultrasonic sensor with Arduino. I also want the Arduino to turn on an LED bar graph strip to show a level.

But the issue is sensor needs to be placed very far (Around 100m) from the arduino, and also the bar graph led is also around 70-100m away from the Arduino. Arduino is placed in a control room with some other equipments. Will this distance have any impact on the operation or the performance of the siganl? if so how can I override it without moving the position of any of the items (Arduino, Sensor, LED graph). There is another output which is actually a 25A relay with coil voltage of around 24V which is also far from Arduino.


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Having problems with the 555 timer, I have decided to configure it in the simplest way possible to test its behavior, by controlling only the inputs to the trigger and threshold pins.
I tied the threshold pin HIGH through a push-button, and LOW through a pull-down resistor. I did the opposite (pushing the button ties LOW) for the trigger.
In this configuration pressing the switches set and reset results in the same action on the SR latch.
Results:
I have found that once the output goes LOW, I can't toggle it back to HIGH. pressing reset switches off the LED as expected.

Process
Result

close set -> connect battery
LED lights up (expected)

connect battery -> close set
LED is off

simulate this circuit – Schematic created using CircuitLab
Note: Voltage and resistance shown in the schematic is exactly what I have used.
Why can't I set the SR latch once the output goes off. Is the 555 timer supposed behave like this? If so why. Or is my 555 timer broken?


texts: What potentiometer should I use for my led strip?

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I have a led strip, this led strip is consuming about 2.5A @ 12V.
Before, I was using an Arduino to modulate the intensity of the light with PWM but I realized that a simple circuit would be even better for what I want.

I am wondering what potentiometer should I use to get the same result than when I was using the PWM, because when I was using the PWM of the Arduino, I often putted it to "1 out of 255" to get a really soft light, so what is the equivalent resistance to "1 out of 255" ? Am I right to think that my potentiometer will have to go from 0 ohms to this specific resistance ?

simulate this circuit – Schematic created using CircuitLab


texts:
In my still relatively short journey into the world of electronics, I have stumbled on multiple schematics that use resistors in serial communication and suspect that they are there for some kind of protection but I have never been exactly sure.

I have found these resistors to vary from 27R to 1K or not being there at all, which is probably the most common case. Here is a picture of such an example from an Arduino schematic.


texts: Can I replace a battery with a source of the same voltage but different capacity (mAh)?

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I have a device that has a bad battery and I am trying to find a suitable replacement. There are no replacement batteries for the device so I am trying to put something together myself. The original battery has written on it 3.7 V, 1.41 W. I have found a battery (CR123A) that is 3.7 volts and 700 mAh. Can I safely use it?

Also, the original battery has 3 wires - red, white, and black. How would I connect the new regular battery?

** It's for my Nest thermostat.


texts: Sending two serial signals down a single twisted pair?

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Let's say I have two serial signals that need to be sent down a cable. This cable features a twisted pair along with a single common wire. If I were to place each serial signal onto one of the twisted pair conductors, how bad would this be?

I realize I wouldn't gain the benefit of common noise rejection had I used the twisted pair to send a differential signal, but would I ruin the quality of each signal by using a twisted pair?

Question: Would each signal in the twisted pair induce voltages into the opposite conductor thus reducing the signal quality? Or would I be better off to have these signals NOT be in a twisted pair? I'm essentially trying to determine whether or not I can be economical with my conductors, or if I should separate them.


texts: Eagle: Make copper pour connect to entire SMD pad

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So I have a design in Eagle with a few SMD components that have pads that should be grounded. I've done a copper pour (draw polygon->name GND->Ratsnest) to create a top ground plane. On some of my components the ground plane connects to the SMD pad, but only by four narrow traces (such as below):

I would like the entire SMD pad to connect to the ground plane. It's an RF design so grounding is fairly important. Has anyone experienced a similar problem?


texts:
I have built a LM317 power supply, which is working nicely through a DC wall wart and wanted to hook up to an AC transformer so it can run off mains and free up my wall wart, so I made up the below circuit

And hooked it up to my 240V to 18V transformer on bread board, and had smoke coming out of it. Note only the 18V side was connected up to my bread board not the 240V part!

Is that correct that diagram. I just want to be able to have AC mains (240V Australia) through a 500mA-1A fuse into the transformer then rectified off to my power supply.

Am I missing something?

NOTE: In the diagram AC+ is 18V tap out of the tra


texts:
I have a 150 KVA genset on a remote work site in Indonesia.  It is new and has a microcontroller that gives all kinds of information we have never had at our fingertips before.
I have been reading about KVAR, how it relates to active and reactive power, and the usual things that you would find in a google search. But it is all related to much bigger installations and I would like to know how it practically relates to our small genset.
Just now we are not processing a harvest so not using all our big load equipment, but as we are doing an oil change on our smaller unit we have the 150  kva unit online for a bit.  because of this and the new information from the display first time I have some information on our base load for the camp.  I noted the fallowing:
Load 50 KVA
kVar 21
L1 pfLg 0.91
L1 pfLg 0.90
L1 pfLg 0.80

I believe pfLg is Power factor lagging.
I generally understand lag and lead with respect to phase angle, and load types. But what is the practical effect on genset life, efficiency and most importantly fuel consumption?


texts: This circuit is used for overvoltage protection, I can see that the two opamp are comparators that will output 0 or 5V depending on the input, but can't see how it is protecting from overvoltage. Thank you for your help.


texts: Transform small Arduino protoboard project in a final solution

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I am collecting data on consumption and solar production and I centralize it in a Raspberry with Openhab.
Now I want to connect to Smart Grid Ready and/or Power Control of a Panasonic Aquarea aerothermal unit.

I will use mainly an Arduino and some already done modules like (two relays module, PWM to 10v module, ethernet module and possibly some LEDs or little LCD). As I've very little experience on electronics I will try to go for already done modules.

I will start with a protoboard, but now that I plan to buy all the components I'm considering what's the best way to transform it into a final solution, to put in the machine room when I test it.

There are premade special boxes where I can fit what I will need and have outputs for ethernet, power,...?
In case I've to use only already done modules I suppose that a simple box and wire will be enough, but If I need to use some electrical components what's the easiest way to go, a stripboard?


texts: Is correct to apply the next boolean algebra rule?

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Im trying to simplify the next boolean term
\$E(A\bar{B}+C\bar{E})+\bar{E}(\bar{A}B+\bar{C}E)\$
in this way

\$A\bar{B}E+CE\bar{E}+\bar{A}B\bar{E}+\bar{C}E\bar{E}\$

\$A\bar{B}E+\bar{A}B\bar{E}\$

But in this last line I don't know if this can be argumented as the same case of \$A+\bar{A}=1\$,so finally it can be minimized
\$A\bar{B}E+\bar{A}B\bar{E}=1\$


texts: Motor with freewheeling, variable friction and force exertion

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I search for a stepper-, servo- or other motor and a related circuit, which is suitable to handle the following aspects:

freewheeling:
Spinning the motor shaft by hand without (or as little as possible) friction
variable friction at the motor shaft under computational control:
Rotate the motor shaft by hand with a specific rotation behavior (rotation needs less force (smoothly rotation), or rotation needs more force (hardly rotation))
motor brake / lock:
Rotate the motor shaft by hand is not possible, position locked
exert a specific and directed motor force:
Rotate the motor shaft with a maximum of force so that a human can not hold the shaft

I would be very pleased if anyone can give me any advice. It would be perfect if the motor size is as small as possible.

Thanks in Advance :-)


texts: Shaded Pole motor - change RPM by relative change to windings

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I've got a small shaded pole motor (C-type) that I'm cannibalizing for use in a project,  but the current RPM is too high.  I don't want to spend the effort to build a micro-controller to run it.

Is there a way to easily change the RPM by making a relative change to the wound coil?  For instance,  it's currently running at 2750 RPM,  it's 80W, 220V and there are 1500 windings on the coil.  Without going into serious design formulas and discussions,  are there 'rules of thumb' that I can use to change the RPM?  For instance, to half the RPM, half the number of windings, double the wire gauge, or something similar.  I'm not aiming at a specific target (RPM wise) I just want it slower - somewhere between one third,  and a half of the current RPM.


texts:
In my university EE lab we were working with a 1N4148 diode to rectify half a sine wave and measure the RMS value of the current in a simple circuit. To the left is the circuit we had to make and to the right it's the modeled circuit for theoretical calculations.
However, from reading the datasheet (http://pdf.datasheetcatalog.com/datasheet/fairchild/1N4148.pdf) I find no reference not only to a model nor any mention of a resistance of 122 Ohm and the value of the DC voltage source of 0.48V. Is the model wrong, or am I just interpreting the datasheet wrong?


texts: Transmission Line Impedance Matching Basics

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From what I understand, matching a load to a transmission line means that no signal is reflected from the load, which means that at the two sides of the connection point between the load and the transmission line the impedance is the same, the load impedance. I tried to test my understanding with the following example:

If we have a \$50\Omega\$ transmission line connected at one end to a \$50\Omega\$ source and at the other end to a \$100+50j\$ load. We would like to match this load to the transmission line, using a shunt short stub. I used the Smith chart to calculate the point where we connect the stub to be \$0.199\lambda\$ away from the load. I also used the Smith chart to calculate the length of the stub to be \$0.125\lambda\$.

Now for the load to matched, the impedance to the left of the connection point should also be \$100 + 50j\$. But I am getting \$100 - 50j\$. I used the equation
$$Z_{in} = Zo \frac{Z_L + jZ_0\tan\beta l}{Z_0 + jZ_L\tan\beta l}$$

with \$Z_o = 50\Omega\$, \$Z_L =\$ parallel impedance of the stub and the source : $$\beta l = 2\pi \times 0.199 =0.398\pi $$

$$Z_L = \frac{j50*50}{50+j50} =25+25j $$

What am I doing wrong?


texts: How to check maximum frequency generation capability PWM of microcontroller?

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I am new to Texas Instruments Controller. By checking the datasheet how can we come to know about the maximum output frequncy generation of PWM of the controller. Is it related to the clock frequency of Microcontroller?
Thank You


texts: Protecting an ADC from negative voltage: Is it better use diodes OR to offset voltage?

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I'm working on a simple guitar amplifier and reader with Arduino.  The Arduino will use this input to find the amplitude and frequency of the input signal.

I'm getting confused about how the ADC inputs should be protected from negative voltages.
So far, there's I've found two solutions: Use a diode to stop negative voltages OR offset the voltage. Using a diode seems like it would be easier to calculate the frequency since the negative cycle is just 0V, but I'm afraid that the signal will get too distorted or weak.
But I'm just not sure which is the correct one for this situation. Which is the better solution? And why?

This is my circuit using a diode on the output. Vout is across R3:

This is my circuit using offset voltage. Vout is the BJT collector voltage:


texts: What is the importance of the input and output impedance of a BJT

texts:
What is the significance of the input and output impedance in a BJT circuit?

High output impedance means little to no current will flow at the output, why is this important?


texts: 3W 12V COB LED with 12V Campervan system

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I have an LED downlight in the camper we just bought but unfortunately the module inside is dead. I would like to replace it with another LED module/chip for cheap.

The light we have: http://www.pro-car.de/en/products/led-lights/surface-mounted-power-led/surface-mountedbuilt-in-power-led/

Dead module:

I have purchased this.

The camper circuit is run from a 12 V "leisure" battery.

It seems the light is on an independent switched circuit.

My logic has lead me to purchase the 12V COB LED commented with the hope to just directly connect it to the circuit where the previous module has been removed.

After further research I am confused with a few questions...

Does the LED require a resistor and/or LED driver to safely operate OR

a) does it already have this built into the chip.
b) it doesn't require either as it is rated to 12V.

What happens when the camper is plugged into a site and we have full mains power?

Any suggestions to cheap suitable drivers or alternative replacement LED module/chip are welcome.


texts:
I have two 64Kx8 bit memory chips which I have connected to an FPGA configured using Qsys as a single 64Kx16 block. I have used a Generic Tri-state controller as interface, with both address width and data width set to 16:

Unfortunately, this doesn't produce the result I want (which is to have a single 128KB block of RAM with 16-bit access). My controller occupies only 64KB of address space. It looks like Qsys treats my SRAM as 32Kx16 block with 16-bit address bus which allows addressing individual bytes.

Is there a way to configure my controller in a way that makes the whole 128KB of memory accessible? Here's a diagram of connections between the chips:

simulate this circuit – Schematic created using CircuitLab


texts: Define the purpose of these components in the operation of this low side driver

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I am trying to understand the operation of the following low side driver circuit I found in a schematic of an old pinball machine (redrawn for clarity):

L1 is a Solenoid and Q1 is a Darlington BJT (TIP120).

What is the purpose of C1, R2 and D1 and how does it affect the
circuits operation?
What would be the likely outcome if C1, R2 and D1 where removed from the circuit?
If the 7407 open collector buffer and R1 pullup were removed, and assuming the MCU pin could supply sufficient current to drive the Darlington directly with the appropriate current limiting resistor, would C1, R2 and D1 remain unchanged?


texts: Should there be a clearance between a lithium polymer cell and a charging circuit?

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I'm building a compact portable console that is going to use a 500ma charger board from Adafruit and possibly a 5v 1a boost as well. Past experience has taught me the chips on those little circuit boards can get quite toasty.
There is not a lot of clearance in my current design between the top of the breakout boards and the flat underside of the polymer battery.
What would you recommend for clearance between the two?
Alternatively, is there a way I could implement some sort of nonconductive barrier to prevent them from touching and exchanging heat?
Thank you in advance, I've done mods before but this is my first time playing with case design.


texts: Design sequential circuit with 3 state buffer

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I asked to design a sequential circuit with 3 state buffer so when :

Load = 1 -> put data into output

Load = 0 -> don't change output

Here is my design:

But question said also use other gates.

Is this design wrong?


texts:
Does anyone know what's this exact connector:

I got it from here, but I lost these metal connectors, and I was hoping to find them at DigiKey or similar sites, but the one that I was able to find is for slightly different connector, female obd2 connector which you can find there which looks like this, and that one does not fit into the socket that I have from AliExpress (which I need):


texts: Using an RC snubber with a triac. Is this design safe? (simulation included)

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I'm designing an ac switch for a washing machine motor. No speed control is intended, only a switch to turn the motor on for 10 seconds and off for 10 seconds. I'm using a MOC3063 zero-detecting triac driver and a BT137-600E triac. This circuit was recommended in the MOC3063 datasheet (I have changed the triac to BT137):

I have empirically found the model of the motor:

I haven't yet implemented this design and I was experimenting with the values using a circuit simulator. I used the following circuit to see what would happen without the snubber (for the sake of simplicity the triac(s) have been replaced with a switch):
(Add http: at beginning of image link)

The switch disconnects after 160ms. The result of the simulation shows a 250000V spike!:

Now I use the circuit with the snubber:

The voltage taken from the same place shows:

So it's obvious the snubber has reduced the voltage spike from 250000 to 2000 volts. And the dv/dt is about 40v/us which is lower than the triac rated dv/dt which is 50v/us.

Question 1: I calculated dv/dt by dividing the maximum voltage of the spike by the time it took for the spike to reach its maximum (~2000v/50us). Is this correct? I can get higher or lower values depending on the section of the slope I calculate this. Is the dv/dt I have obtained reliable?

Question 2: Supposing that I had obtained the dv/dt correctly in question 1, the triac can now handle the dv/dt but will it be able to handle the 2000v spike? Does it have a breakdown voltage? I don't see anything in the datasheet except the "repetitive peak off-state voltage" which is 600 volts. What is the one time peak voltage a triac can handle while in off state?

Question 3: The simulations showed that almost all of the ringing spike voltage (2000v) shows up on the snubber capacitor and the snubber resistor only sees a 20 volt (ringing) spike. What kind of capacitor should I use to handle this voltage and with what voltage rating? Can a 600v cap handle this one-time spike?

Question 4: The power dissipated in the resistor is shown below (Remember once the triac turns off it will remain off for 10 seconds) What kind of resistor (wattage that it can handle) should I use? And do I need to use a carbon composition resistor (which is usually used in snubbers) or will a normal carbon film resistor suffice here?

Question 5: What will happen If I replace the 10nf snubber capacitor with a 100nf capacitor? If I do this the voltage spike will go down to nearly 600v (see figure below) and I will be on the safe side regarding all the parameters (dv/dt, spike voltage, capacitor voltage). So why shouldn't I use 100nf? Why did the datasheet sheet of MOC3063 recommend a 10nf but the simulations are showing much better performance using a 100nf cap?

Sorry for the long post and many Questions. But I really need to understand this.


texts: Why the driving point functions have the condition that the degree of numerator and denominator only at most differ by one?

texts:
I do not understand the logic behind this restriction. What would go wrong if this condition is not fulfilled?

E.g, in frequency domain \$\dfrac{1}{(s+1)^2}\$ which has an inverse Laplace of \$t \cdot e^{-t}\$ which seems pretty bounded and stable but the above mentioned condition violates in this network function.


texts: Frequency Conversion Product Lower than 0 Hz (Negative Frequency?)

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If I have a bandwidth of frequencies from 200 to 500 Hz made from cosine waves and I mix this with a oscillator at 400 Hz which is also a cosine wave, the mathematics of conversions show that I will get a signal at 600-900 Hz and -100 to 200 Hz. Does this negative frequency from the conversion math physically exist? I dont think it does - so where has some of the energy from -100 to 0 gone?

I understand the negative frequency fourier transform concept, but the above different and is tricking me.

Thanks for you help in advance.


texts: Laptop HDD (100565308 Rev A) BIOS chip swap - chip won't come off?

texts:
I'm attempting to remove a BIOS chip from a Seagate Momentus 7200.4 HDD with a 100565308 Rev A chip number.
I've followed videos online, but for some reason the BIOS chip will absolutely not come off. I'm worried that I will damage the chip from scratching it up because of the tweezers slipping off.
To remove the chip, I'm using a micro heat pen rework station set to 300C.
Is there some general reason that this chip won't come off? Should I use some other chemical to remove it now that the solder is gone?
EDIT: Thank you all for the great information. To explain exactly what I'm doing, I'm attempting to restore an old laptop hard drive which has some burnt looking circuits on the chip. I happened to have a second working hard drive with the exact same model which originally came with the laptop, so I am using it as a donor drive to fix the broken one. I believe I just need to take the 8-pin BIOS chip off of the PCB, but it is giving me troubles as noted above.
My equipment is:

Hot Air rework station: https://www.amazon.com/gp/product/B07XPG8VPG/ref=ppx_yo_dt_b_asin_image_o09_s00?ie=UTF8&psc=1
Soldering iron: https://www.amazon.com/gp/product/B07RZV2DW8/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Solder: https://www.amazon.com/gp/product/B07VRCBJSZ/ref=ppx_yo_dt_b_asin_image_o03_s00?ie=UTF8&psc=1
Flux: https://www.amazon.com/gp/product/B00425FUW2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

I've tried the hot air gun at 370C briefly with no luck as well. I didn't try some of the other ideas that have been posted yet though
Here's an image of the donor chip - I'm sorry for the hairs all over it, I used a Q-tip to remove some flux with 99% iso alcohol and didn't see the remaining hairs at the time.


texts:
I find I'm a little confused about "image current" and "return current" in PCB/EMI/EMC design. Are they equivalent? Many docs use this model when talking return current

Exactly, I will treat the return current as a current flowing on a image plane. So, may I call it "image current"? If so, then what about this situation:

Is there image current flowing on the image plane?


texts: Can anybody tell me the name of the connector shown in these photos? (I mean the biggest one, which is centered in the photos)


texts: LTC3862 GATE Pin always high and switch on?

texts:
Switch Mode Power SupplyLTC3862-1 GATE PIN(1-2) ALWAYS HIGH and MOSFET Gate Pın ON
We are using a LTC3862 for a SMPS (switching mode power supply, 24V to 130V, 0.5A).
Firstly, we modelled the design in LTSpice and it worked better than the design installed on the perforated plate.
The MOSFET's gate pin is always on ("high") and the LTC3862 gate pin voltage value is 5V constantly. In LTSpice, the LTC3862 gate pin value is 0V to 10V and it is working. What could be causing this?

Thanks in advance for the answer.


texts: Negative beta forced in saturation region of BJT?

texts:
is it possible to have a negative value of beta forced in the saturation region of a BJT when \$V_{CE}<0\$?

Thank you very much.


texts: How to read an input value from atmega32 pin?

texts:
I'm trying to read a value from an avr pin but it doesn't work.

I'm trying to read a value that is coming from a push button and this button is connected to 5V DC cell.

When I press the button the 5V should go to the atmega32 and reads it, then the if statement becomes true and the led goes on.

However, when the value becomes true the led will turn on but its not.

bit 1 is the button bit 0 is the led

#define DDRA (*((volatile unsigned char *)0x3A))
#define PORTA (*((volatile unsigned char *)0x3B))
#define PINA (*((volatile unsigned char *)0x39))

int main(void) {
   DDRA |= 0b00000001;         // pin 0 output

    while (1) {
        if (PINA&0b00000010) {  // button pressed
            PORTA |= 0b00000001;   // turn led on
        }
    }
}


texts: Alternative ways to catch an inductor's flyback current

texts:
This guy had a bit of problem installing the flyback diode to his relays due to physical obstruction. Now if that is really an issue will this be a good alternative way, for perfboards and breadboards?

simulate this circuit – Schematic created using CircuitLab

When the MOSFET is turned on, C1 is essentially shorted out and completely discharged.

When the MOSFET is turned off L1's flyback current charges capacitor C1 to a voltage.

Capacitor C1 is chosen to be able to hold all the energy L1 can hold without reaching a voltage so high that it can damage the MOSFET.


texts: Replacing power transformer with SMPS to charge SLA battery

texts:
Item: 25W amplifier/speaker with SLA batteries.

I've done a little bit of modding in there. I doubt the warranty is valid any more, lol.

In case you don't want to read the link about my modding, basically, I just added a wire to the power switch of the amp, sending 12V from the battery to a LM2577 DC/DC boost converter set at 12.5V, which powers my mixer. So far, no explosions or short circuits since July 2015.

So here's my deal. Mains voltage is 240V (supposedly, but it's always lower). There's a transformer inside which is outputting almost exactly 12V, and this 12VAC is rectified and fed directly to the SLA battery. There doesn't seem to be any sort of regulating circuit that I can see, at all.

The SLA battery is two 6V 4.5Ah in series. To the best of my (admittedly poor) knowledge, lead acid batteries are supposed to be pretty robust. But that's not the point.

I want to save a tiny bit of weight in the device, and increase its efficiency a little, by taking out the 240V-12V transformer, and replacing it with a 12V SMPS, of which I have several lying around (old external HDD power supplies).

Would you advise against this? I'll have to say I'm not totally up to speed on battery management so please do educate me on the pros and cons here. I am also aware that SMPS can induce interference in the audio circuits. Is there a way around that?

Later on, I'll also look into replacing the battery with something lighter if it's possible, but that's a future concern. After all, the major amount of the weight is the speaker itself.

TL;DR: I have a transformer directly charging a 12V SLA battery for an amplifier/speaker. I want to replace the transformer with a SMPS.


texts: Estimate Current Requirements Of A Circuit

texts:
So far with all my electronics circuits I have been using a DC wallwart so didn't have to think much about the current requirements of my circuits.

Now I have a prototype that I would like to run using a battery (ideally with 2 coin cells @ 3V each in series but a 9V battery would also do).

I get the basic idea that all batteries are rated at mAh so if I know the max current used by my circuit I can estimate the time the battery would last.

But the details confuse me. With a simple micrcontoller circuit this can easily easily be done by looking up the the max current draw from the microcontroller datasheet. However in my circuit I have a microcontroller connected to various LEDs', a LCD screen (savaged from an old mobile phone), a Bluetooth serial UART and a LM317 voltage converter IC (to step down to 3.3V for LCD).

How do I figure out the current requirements with all these peripherals in my circuit ?


texts: How do I find specific transfer functions from a plant of a MIMO system?

texts:
Suppose I have a physical system, for example a mass-spring-damper system, which has been written in state space. Now, suppose that the matrices describing the system are \$A,B,C,D\$.

Moreover, let' s say it is a MIMO system, and I have \$6\$ inputs, which are \$u_{1},u_{2},d_{1},d_{2},n_{1},n_{2}\$, where the first two are the outputs of the controller, the second pair are the disturbances and the last ones are the noises.

Ans there are \$4\$ outputs, which are the displacement of a mass, defined as \$z_{1},z_{2}\$ each of which has two components.

So, I define the plant as:

G = ss(A,B,C,D)

now, I have my plant defined. Suppose now I want to find here the transfer functions of the systems, such as the sensitivity function, the complementary sensitivity function and the control sensitivity function, how could I do?

I know that I will have smething like:

\$\begin{bmatrix}
z_{11}\\
z_{12}\\
z_{21}\\
z_{2,2}
\end{bmatrix} = \begin{bmatrix}
 &  &  & \\
 &  &  & \\
 &  &  & \\
 &  &  & \\
 &  &  & \\
 &  &  &
\end{bmatrix} \cdot \begin{bmatrix}
d_1\\
d_2\\
u_1\\
u_2\\
n_1\\
n_2
\end{bmatrix}\$

and to know the transfer function I need to look at the appropriate entry in the transfer matrix, but how do I know that the order of the inputs and of the outputs is this?

So, what I mean is that I could also have

\$\begin{bmatrix}
z_{21}\\
z_{22}\\
z_{11}\\
z_{12}
\end{bmatrix} = \begin{bmatrix}
 &  &  & \\
 &  &  & \\
 &  &  & \\
 &  &  & \\
 &  &  & \\
 &  &  &
\end{bmatrix} \cdot \begin{bmatrix}
u_1\\
u_2\\
d_1\\
d_2\\
n_1\\
n_2
\end{bmatrix}\$

or other combinations, so if I do \$G(1,1)\$, in the first case I obtain a transfer function, and in the second case I obtain a different transfer function.

So, how can I do?


texts: How can you calculate the effective transfer rate of canbus?

texts: The things i found out are that the baudrate and maximum bits of the message matters. But i don't understand how they exactly calculate the transfer rate.


texts:
Background:

I designed a bipolar audio amplifier to drive a small 0.5W 8 ohm speaker. I am going to use it to listen to other circuits I make. First time doing this since college. Here's the schematic:.

It's a CE followed by 2 CC stages. I don't have power resistors or bjts, which is why I have 2 transistors and 4 resistors in the second CC stage.

I put 2 CC stages because I needed a lot of bias current for the output transistors, meaning R8-14 are small, but the CE input stage didn't like driving a low impedance so I put another stage in between.

The simulation works pretty well and drives the 8 ohms with ~250 mW.

My questions are:
1.) Does it make any sense to match the DC level between stages if the stages are AC coupled?

2.) What is the minimum limit for collector current? Is it just when the internal pn junctions stop being fully on?

Any other comments on the circuit are appreciated. I apologize if I didn't do enough searching before asking.

I checked the meta and it said design review questions are okay as long as they're kind of constrained.

Thanks!


texts: Synthesis error in module using Verilog (Xilinx Vivado 2015.4)

texts:
I am facing an issue with the post-synthesis implementation of a special Serial-In-Serial-Out kind of buffer. It receives inputs and stores them in registers and can later output the stored inputs.

When iReset is HIGH, the contents of the buffer are cleared.
When  iValid is HIGH, the values of the registers in the buffer are
shifted and buffer[0] receives iResidual.
When oEnable is HIGH, the buffer outputs the values of the last
register to oResidual (in this case buffer[2]) and the values are shifted accordingly.
When oValid is HIGH, it means that oResidual is a valid output.

Here is the full code:

module ResidualBuffer (
    input iClock,
    input iValid,
    input iReset,
    input oEnable,
    input signed [15:0] iResidual,

    output signed [15:0] oResidual,
    output oValid,
    output signed [15:0] bufferReg0,
    output signed [15:0] bufferReg1,
    output signed [15:0] bufferReg2
    );

parameter blkSize = 3;

reg signed [15:0] buffer [0 : blkSize - 1];

integer i;

reg signed [15:0] oResidualReg;
assign oResidual = oResidualReg;

reg signed [blkSize : 0] oValidReg = -2; // for blkSize = 3, oValidReg = 4'b1110
assign oValid = oValidReg[0];

assign bufferReg0 = buffer[0];
assign bufferReg1 = buffer[1];
assign bufferReg2 = buffer[2];

always @(posedge iClock or posedge iReset) begin
    if (iReset) begin
        for (i = 0; i < blkSize; i = i + 1) begin
            buffer[i] <= 0;
        end
        oResidualReg <= 0;
        oValidReg <= -2;
    end else if (iValid) begin
        for (i = 1; i < blkSize; i = i + 1) begin
            buffer[i] <= buffer[i - 1];
        end
        buffer[0] <= iResidual;
        oResidualReg <= oResidualReg;
        oValidReg <= oValidReg;
    end else if (oEnable) begin
        oValidReg <= oValidReg>>1;
        oResidualReg <= buffer[blkSize - 1];
        for (i = 1; i < blkSize; i = i + 1) begin
            buffer[i] <= buffer[i - 1];
        end
    end
end
endmodule

The behavioural simulation is working as expected:

The post-synthesis simulation is different and confusing:

The problems I am facing are:

When iValid is LOW, buffer[0] continues to receive iResidual and the
values in the registers are shifted and I don't understand why.
When oEnable is HIGH, it is reflected only in the next clock cycle.
However this is not the case for iValid as explained in (1) and I don't understand why.

~Edit:
For those who want to look at the testbench I used

`timescale 1ns / 100ps

module ResidualBufferTB;

    reg iClock;
    reg iValid;
    reg iReset;
    reg oEnable;
    reg signed [15:0] iResidual;
    wire signed [15:0] oResidual;
    wire oValid;
    wire signed [15:0] bufferReg0;
    wire signed [15:0] bufferReg1;
    wire signed [15:0] bufferReg2;

    ResidualBuffer #(.blkSize(3)) DUT (
                        .iClock(iClock),
                        .iValid(iValid),
                        .iReset(iReset),
                        .oEnable(oEnable),
                        .iResidual(iResidual),
                        .oResidual(oResidual),
                        .oValid(oValid),
                        .bufferReg0(bufferReg0),
                        .bufferReg1(bufferReg1),
                        .bufferReg2(bufferReg2)
                       );
    always begin
        #0 iClock = 0;

        #125 iClock = 1;

        #125 iClock = 0;
    end

    initial begin
        iReset = 1; iValid = 0; oEnable = 0;

        #125 iReset = 0;

        #250 iValid = 1; iResidual = 20;

        #250 iResidual = -123;

        #250 iResidual = 31;

        #250 iValid = 0; iResidual = 0;

        #250

        #250 oEnable = 1;

        #1250

        $stop;
    end

endmodule


texts: Best technology to have a specific person's proximity in a room turn on a light outside the room

texts:
I need help deciding which technology to use so that, when a specific person (1 out of 6) walks into a room, their specific ID is recognized and the corresponding colored light is illuminated outside of the room.

The building in which this will take place is still under construction and therefore the system can be hardwired in.

Originally I had wanted to use RFID but it seemed a bit pricey. I then considered Bluetooth but I am just not as tech savvy as I would have to be to use that.

What technology could I use to recognize the device on the person and activate the appropriate light? The amount of data used in the recognition step doesn't seem to be a problem, as we just need to differentiate between 6 distinct identities. But I'm just no fully aware of what is available out there.


texts: Wiring a circuit with 2 microswitches for 2 pedals where circuit is off under only one condition

texts:
Okay so this is extremely specific and I've searched around but I might be using the wrong terminology. I have two automotive foot pedals that I can attach microswitches (or anything I guess) to, either when depressed or not to know its state.

I've drawn it out many ways but can't wrap my mind around making a circuit to where it's always on unless only one condition is met: brake pedal is released and accelerator is pressed. This is the condition breaks the circuit and any other combination completes the circuit.

However I'm willing to concede that if this is not possible, then the bare minimum circuit would require it to be always off but ONLY on if the brake pedal is pressed and accelerator is not. But I don't know if this is possible either.

I wonder if there isn't some additional thing I'd need apart from a microswitch on each pedal to detect its state. I'm hoping I can get this to work.

Thank you for any answers!


texts: Circuit with 1 diode in parallel with a resistor

texts:
Sorry if this question has been answered here before, but I just can't seem to find any info on this.
A little background. I am currently doing an automotive mechatronics course and, while I know some things about circuits, my knowledge on this subject is very limited.
I tried to my best effort to solve this on my own but i just can't get matching values.
Here's what i know:
The total current (It) is 150 mA
The voltage drop through the LED is 3 V
The current through R3 is 20 mA
The LED used in the drawing is just a representation (I couldn't erase the name, sorry)
If anyone can help me understand how to get the voltage drop through R1, R2, R3 aswell as the current, I will be most grateful

Here's what I tried:
Ohm's law on first resistor to calculate voltage drop: it came as 24 V, which would be impossible since the source is only 9 V
Assuming that on the parallel part there was a voltage drop of 3 V:
This would mean that across R1 and R2 the total voltage drop would be equal to 6 V. I could calculate V1, V2 and the current aswell. V1 = 4.8V, V2= 1.2V
I= 30 mA.
From here I can get to I=Id+I3, and I3 = U3/R3. Assuming that R3 is indeed 20 ohm, I3 would come as 0.15 A, which is 5x times larger than the input current.
So, my values don't check out and from the feedback I am receiving here, it's not a problem on my end


texts:
I am currently working with ADAU 1772 Audio Codec. Since the Evaluation Board from Analog Devices is rather expensive for me, I decided to create my own programmer using FPGA. I am trying to boot DSP in assembly using this tutorial: Booting a SigmaDSP from a microcontroller with no C compiler . Have any of you ever tried it? Did it work?

I am in testing phase now and I need to create simple project in SigmaStudio. I have read SigmaStudio tutorial but the problem is that they do not take into account that you got no Evaluation Board hence my puzzlement. When I create new project I add Processor, then I am suppossed to add Communication Channels but I use none of them. Can I just skip this part of making project (do not add any communication channel), go to Schematic Tab and create my system, then generate files and program DSP?


texts: How to design a 2nd Order High Pass Butterworth filter with a cutoff frequency of 0.5 Hz?

texts:
c1=c2=10µf, R1? R2? using the unity-gain Sallen-key topology
what should I do?


texts: Comparator loses voltage when connected to mosfet

texts:
I want to make a discharger for 18650 batteries so I can store them at a specific voltage.

I built a comparator (LM393) with a voltage reference to 3.8V at the inverting input and the voltage of the battery on the noninverting input. The circuit has its own power supply (9V battery). Grounds are connected.

The comparator works fine, but when I connect it to the gate of the mosfet, its output voltage drops from around 9V to just 1V or so.

Also when I disconected the power from the Drain, the voltage appeared again.

I am using a pullup resistor on the output of the comparator (10k, tried 1k and it was the same). I also tried to put the load (5V 5W resistor) on the Drain or on the source, both worked the same. The mosfet can be opened, but the voltage on the non inverting input must be around 6V instead of the 3.8 and higher. And when I apply the higher voltage, at some point the mosfet opens and the voltage on the non inverting input drops to that 3.9V. The mosfet is IRLZ44N.

Please tell me what's going on and what I am doing wrong.


texts: Meaning of the three bars on a circuit and help regarding Kirchhoff's Laws

texts:
So i'm really lost and I have to solve some problems from circuits regarding mainly resistors.
I have this circuit and I am a bit lost because I don't really understand what to do to find the value of the resistors as well as the Voltage on N1 and N2.
I think I need to use Kirchhoff's Laws.
The thing that bothers me is do I need to pretend that the circuit is connected to itslef on the bottom portion ? (the three bars appearing 4 times at the bottom).

Thank you in advance and sorry if my question seems dumb but I really am lost here.

Here is the circuit :


texts:
I have the following trivial question:

I have acquired a noise spectrum with a resolution bandwidth of \$124\mathrm{Hz}\$.
I would like to convert it to \$\mathrm{V/\sqrt{Hz}}\$. Shall I simply multiply or divide the signal by \$\sqrt{124}\$??

Regards


texts: Altium Rename net label, auto update its connection

texts:
I have many net labels in schematics, now I want to rename some of them. But when I do, it doesn't update other net labels with same name.

Lets say I have 5 connection with 1 net label "Pin1", now I want to change it to "Pin5". Is there any way, that I change one and it updates all other 4. Yes there is Smart Edit replace, but that seems a trick and not a good way to do it.


texts: Identify 19-pin connector that looks like USB micro

texts:
We use a satellite modem that sports a 19-pin connector. There is a handy connector on the board to let us communicate with it, but the supplier doesn't know what brand/model the connector is, and the manufacturer is incommunicado. We're reduced to using a proprietary $50 cable that mates with it and terminates in fly-leads that we have to manually solder. Can you help?

At first it looks like a standard USB micro, but on closer inspection it has 19 very compact contacts (10 on top, 9 below). Here are some photos of both ends:

It would be super if you could identify manufacturer and part number or series.


texts: How does twisted pair turn rate affect interference rejection bandwidth?

texts:
I'm curious to know how the turn rate of a twisted pair affects the frequency of crosstalk interference rejection.

It's clear that an untwisted pair has no inherent rejection.  Alexander Graham Bell figured out in 1881 that twisting is good, so we now twist wire to reduce crosstalk.

As twisted pair communication has evolved, cabling has started to be specified with more and more twisting (cat5 is around 50-70 twists/meter).  Ostensibly this is to ensure we can reduce crosstalk at higher frequencies of communication.

I understand the principle of why twisting is good.  I'm looking for a mathematical or rule-of-thumb explanation for the relationship between the twist ratio and the bandwidth I get from crosstalk rejection.

The Internet is not yielding such an explanation for this.  Am I missing something?


texts: Calculating voltage loss using impedance of a system

texts:
simulate this circuit – Schematic created using CircuitLab

So I'm trying to figure out the Total impedance Z of a system with a capacitor in series with a resistor and inductor, where the resistor and inductor are in parallel.

The total impedance I got is

\$Z=0.08587...Ohm < 89.8679°\$

and the calculations for it are (a bit trimmed from the actual calculations for your convenience):
\$R = 8Ohm\$

\$L = 2mH\$

\$C = 10uF\$

\$f = 10kHz\$

\$U_{in}=1Vpp\$

\$R = 8Ohm\$

\$X_C = 2πfC = 0-j7.9577... Ohm < -90° \$

\$X_L=\frac{1}{2πfL} = 0+j25.1327... Ohm < 90°\$

\$Z=X_C+\frac{RX_L}{R+X_L}\$

\$Z=9.1999...Ohm < -37.8539°\$

With the total impedance I figured I could calculate the current based on \$U_{in}\$, but the current I get is above \$10A\$, which would put the voltage drop on \$X_C\$ alone above what the value of \$U_{in}\$ is.

Am I misunderstanding something on how I should use the value \$Z\$, or am I misunderstanding the answers of my calculations?

Again, I'm trying to calculate the voltages \$V_C, V_R, V_L\$ and I assume that \$V_R=V_L\$

Edit:

With the newly found impedance, I was able to calculate

\$I= 0.07686... A <37.8539° \$

and

\$V_C =  0.6116... V < -52.1461° \$

Assuming that it's correct in the first place, how should I proceed to calculate the phase shift of the voltage drops in V_R and V_L? Is it simply a sum with the phase shift natural to that component with the phase shift of the components prior to it (in this case, \$XC\$)?

Meaning:

\$V_L = 0.7071V-0.6116V  <(-90°-(-52.1461°))  = 0.0955V <37.8639°\$

\$V_R = 0.7071V-0.6116V<-52.1461° = 0.0955V<-52.1461°\$


texts: Current sense amplifier for overcurrent protection

texts:
I'm trying to compare the use of a current sense amplifier with a sense resistor for overcurrent protection of SiC MOSFET. Here is my schematic using  INA210 current sense amplifier, UCC21732-Q1, and SCT3160KL MOSFET.

And this is the simulation output:-

How can the /FLT pin go low before OC sends the signal? Or should I see the delay time right from when OC pin starts to go high?


texts: What is the meaning of collector current pulse in the datasheet?

texts:
Here is the datasheet of a transistor:
http://www.adafruit.com/datasheets/TIP120.pdf

In maximum ratings, there is a section called "Collector Current (Pulse)".
What does that mean in practice?

Lets say this transistor is applied 30V constant DC to its ends.
So the max. collector current should not exceed 5A.
But if the applied 30V is in the shape of a pulse with lets say %99 duty cycle will the max. current be 8A? Thats what I understand but Im not sure.


texts: Updating of a memory cell / synchronization with a clock

texts:
I'm wondering how computers actually work on a gate-level. I can see how a storage mechanism could be built from logic gates (e.g. SR NOR latch). What I'm wondering: how do values in memory cells get updated if the new value depends on the old one?

Example: I have a one-bit storage cell and I want to build logic that inverts the value in the cell. Easy - read the old value - invert it - activate the corresponding input to the memory cell to set the new value (R or S). But that's just going to trigger a feedback loop, flipping the bit as quickly as possible.

How is this situation handled in microprocessors? I imagine it has something to do with the clock signal, but I don't see how to solve it even with an external clock.

Put another way: given an RS-Flip flop, and a clock signal line, is there a gate arrangement that flips the Flip flop once per clock tick? If this isn't actually solvable on the gate level, how is it solved on real microchips?


texts:
I have a problem with below code. The variable loopTimes get reset to 0 after one loop.
The program also has a ISR routine for TWI interface which updates the value as shown in the below code.

int main(void){
 //my var
 int loopTimes = 0;

 for(;;){

   if(loopTimes >= 0){
      loopTimes--;
      //Do some operations
   }
  // check if twi has data
   if(TWI_has_data()){

   //Read it into buffer
     twi_read_data(rxBuffer,2);
     if(loopTimes == 0){ // set the variable if it has reached zero
       loopTimes = rxBuffer[0];
     }
   }
 }
}

The setup is a ATMEGA 8L on a custom board running at 8 MHZ external crystal, program compiled using Atmel Studio 6 with compiler optimization at level 1.
I am not able to find out why the variable gets to zero every time the loop goes through.
The problem wont occur if i declare loopTimes outside main loop.

This solves the problem

int loopTimes = 0;
int main(void){
 //my var
 ... Rest of code is same
}

Can someone explain this a little more ?


texts: Bypassing a multi function Christmas light string controller

texts:
I'm getting annoyed with my light string, it turns on to a random effect out of 8 and all I want is an always on.
I managed to find this great website showcasing different controllers and how to bypass the logic to have the lights always on https://auschristmaslighting.com/wiki/Bypassing-Multi-Function-LED-Controllers
I have a very similar board to this one that I found on the website, it shows which solder pads to connect to make the lights always on without any effects.

Here is my controller

By the looks of it, the only difference is the 4 transistors(?) on the board from the website, whereas I have only 2. If the same logic applies, soldering the last 2 pins before they breakout into the separate leads will work? Maybe? I don't have enough experience in electronics to figure out which pads to connect together, maybe someone has an idea.
Thanks :)


texts: Sound Sensor that can give feedback on the amplitude of different frequencies?

texts:
I'm trying to find a sound sensor that can give feedback on all the frequencies of sound and their levels.

The sensors I'm finding in my search however only support level of sound it seems.

Is it possible to get the level of individual frequency ranges from one sensor, or does it require multiple senors?

I'm new to this so don't know the exact terminology, but essentially I want to create something that can respond to a set of different frequencies of sound independently, not just how loud the sound is.

Ideally the sensor would be made to work with Arduino, but I'm not afraid of something that it is more complicated.


texts:
i test the below circuit using with LM358. and i use instead of n-MOSFET i use CL100 transistor and for p-MOSFET i use CK100.

in my 4-20mA converter circuit for 1.1 v input i get 31mA
and for 4.4v i get 45mA as a output.
this kind of situation what to do? to get a 4-20mA for my input...
is that any components need to change


texts: If a power supply supplies 3 amps, does this mean that 3 amps are always in the circuit, regardless of load?

texts:
If I have a power supply that says +5.0V/3.0A, does that mean that it can go up to 3 amps or does that mean it always has 3 amps in the circuit all the time?

If I need something that takes 500mA, and I connect it to a breadboard, proto board, or PCB, will it only pull the 500mA?


texts: PCB Layout - Transistor to convert analog signal to digital pulses - how to connect emitter GND

texts:
If have designed the following circuit to convert a certain analog signal of an amplifier to digital pulses. The circuit works well - except for one point.

My prototype PCB has 4 of these amplifiers and transistor circuits on it and when one transistor produces a pulse the others do as well.
I did many tests in the last week, an I isolated the problem to the shown transistor stage.
So my guess is right now, that the fast rising collector current of the transistor, causes some short high frequency burst in ground, which is then picked up by the other amplifiers.
however I am not able to fully measure this.
I added C2 (and tried different values, to smoothen the pulse flank) as an afterthought and this already improved it, but not for all situations.
So my next idea is, to separate the GND plane of the amplifiers from the transistor stage - this looks to be the best, as when I remove the transistor stage from the PCB, everything works fine.
But here is also where I struggle.
I plan to put the 2 planes together at a star point.
Here is the layout without GND:

As the emitter of the transistor is kind of on both GND planes and the star point is quite far from the transistor, I struggle on to which GND plane I should connect the emitter.
I tend (just by feeling) to choose the 3V3 GND as this current is what causes the problem in the first place and as this current is much higher.
However, I am worried, that the "small" current flowing through C1 in a pulse situation, has to go all up to the star ground point and back to the transistor, if I connect it like this.
So the 3 options are:

connect to 3V3 GND
connect to 15V GND
connect to both (but then I guess, I'm back to square 1 as this is already the original layout).

I hope, I described the problem clear enough, otherwise, please let me know in the comments, if need some more information.

Edit1:
The Original layout looks something like this:

The bottom layer is 1 solid GND fill.
Now I am thinking about something like this:

Closeup of the transistor circuit:


texts:
I joined just because I'm having sort of a dilemma. I need to design a flash circuit for a tiny SMD based project, and I have a way of doing it, but I want to see if I can make it better and I haven't had any luck for days.

Basically I'm using a 555, in a monostable configuration, which would actually be okay but I want to do better if I can.

I want two simultaneous flashes from the LED, but I'm having no luck. I've tried running parallel 555's, but no luck either.

I also tried an RC circuit, but I dislike how the LED discharges slowly, plus I can't get multiple flashes out of it, which is why I'm using the 555 approach. I like how the 555 just flips the LED ON\OFF and doesn't fade with the cap's discharge. Furthermore, the SMD chip and total solution is pretty tiny.

So basically how do I make this circuit flash the LED twice? Is it even possible with the 555?

PS: I'm sure my values and placement are probably baffling everyone right now. I'm not an EE, but I am learning fast, so if there's other corrections, let me know by all means :)


texts: Why does power driven to the load has this expression?

texts:
I'm designing an oscillator, I'm using as textbook Krauss one.
I would like to design the oscillator In function of the power it must give to the load and the fundamental frequency.
I have seen this expression in bjt amplifier design too.
According to this books, the power driven to the load (RL) is:
P = Icq2 × RL/8
So Krauss find the transistor's Q-point with this expression knowing the load and the power he wants.
I have try to deduce this equation and I have got this expression.
Let's assume the current (I) is the current across the load resistor (for example, using a simulator and measuring this signal).
P(rms) = IRMS2 × RL.
P(rms) = Ipeak2 × RL / 2.
P(rms) = Ip-p2 × RL / 8.
It's a similar expression, however it depends on the alternal current across the indictor, not Q-point.
How can I relation this expression with Q-point?

Also I have another question, let's say I have a voltage amplifier (CE). It has a gain of 2.
If the input signal is 1, I would have 2 volts in the output. So my RL with have this 2 volts signal across it, and this would generate a power.
Now I have 2 volts in the input, this will generate 4 volts in RL. So the power will increase.
According to this, the power depends on the input, the amplifier gain and the RL, not Q-point, so how does this expression makes valid ?
P(rms) = Icq2 × RL/8

simulate this circuit – Schematic created using CircuitLab
Thank you.


texts: Problem with PWM generator SG1525(SG3525)

texts:
I am designing a Full Bridge DC to DC convertor using SG1525(SG3525).
I'm doing the simulations in OrCAD Capture(PSpice).
Actually, I've successfully simulated the Power section of the converter using four IRF540 in two bridges and igniting their V_GS 's with two Pulse Generators that are isolated(virtually) via VCVS's.
For the control section, OrCAD's PSpice says:

  * SG1525 *
  * The following model for the 1525 was obtained by consulting the data sheets
  * and corresponding with Silicon General.  A number of simplifications were
  * made to speed up the model, among these we have:
  * (a) replaced th oscillator with ideal voltage sources,
  * (b) simplified the output stage (only two bipolars per output driver),
  * (c) the sync pin is ignored (can drive clock directly if needs be),
  * (d) made the shutdown pin respond to digital stimulus, and
  * (e) used digital simulation for the internal logic.
  * The impact of that these simplifications must be considered in the context
  * of the parameters of the circuit, and the circuit being examined.  The
  * above list might change as we get feedback. .subckt SG1525  ; note: the node numbers   are equivalent to chip pinout
  +  1    ; - input of error amp
  +  2    ; + input of error amp
  +  4    ; oscillator output
  +  5    ; ramp output
  +  8    ; soft start pin
  +  9    ; compensation pin
  + 10    ; shutdown pin
  + 11    ; output A
  + 12    ; ground
  + 13    ; collector of the output drivers
  + 14    ; output B
  + 15    ; vin
  + 16    ; vref
  + params:
  + period   = 25us ; internal clock period
  + deadtime = 0.5us ; internal clock deadtime
  * Pin  3 (sync) NOT USED due to (a) above.
  * Pin  6 (oscillator time resistor) NOT INCLUDED due to (a) above.
  * Pin  7 (discharge resistor pin) NOT INCLUDED due to (a) above.

I have the following questions:

1. R_T is ignored in simulation, so the period must be set by the user. In model editor it is claimed that period is 25us, but in Schematic Editor there is also a period. Which one is used in simulation?

2. What should be connected to the pin OSC? Actually I don't even know what it is used for?

3. As I know, each of the output pins should ignite two MOSFETS... So where should we get feedback from? Since the output is between the two bridges...

4. Where is the feedback pin? Is it C(pin 13) or COMP(9)(I think it is the controller)

ANY help is greatly appreciated :(


texts: How does programming code provide power to electronic circuits?

texts:
I've been thinking about a question and haven't been able to find an answer. The question is that:

For instance, an Arduino has a 5V output pin to feed any electronic component.  When you code something as "giving nonzero voltage to the output pin", the Arduino provides power to the 5V output pin.

Here, my question is how does this work? It's not a mechanical process, but how can the code control voltage or current?

Someone told me that the transistors do that, but how? How does the code become energy?

Thanks for your time


texts: Difference between battery and capacitor?

texts: Can capacitor acts like power supply, in which situations? How related are charge/discharge time of battery and capacitor? Why battery has longer discharge time compared to capacitor? Why we cannot for example use big capacitors in our mobile phones instead of batteries?


texts:
I have designed a closed loop current control (PI controller) of a DC-DC converter in continuous time domain and it is working fine. The next task is discreetization of the controller and implement it in FPGA Spartan 6. FSW is 40 kHz and I am sensing inductor current with an LEM sensor and then a  low pass filter of 400 Hz and then into my ADC in designed hardware.

Now the question is while discreetization of controller, what sample time do I use? In VHDL code I have written, I calculate PI output at every rising edge of clk (50 Mhz). This would mean a TS of 20 ns. Could there be any issue with sampling so fast? My understanding is that I should sample at least a decade faster than the controller bandwidth, which I have designed to be at least a decade lower than my switching frequency.

Any advice is much appreciated.