texts: I am trying to trigger an ADC conversion through TA0 CCTL1 Output in my MSP430, but nothing is happening

texts:
I am doing a simple project with MSP430FR6989, where I am converting an analog signal to a digital one, when it finishes conversion it will jump to an ISR and increment an integer.

We can configure the ADC12_B (ADC module for the microcontroller) to start sampling and converting by setting ADC12SC bit from ADC12CTL0 register, or through various device-specific triggers.

(User Guide pg 867/1021)

(Datasheet pg 91/183)

I am configuring my MSP430 to start converting using the TA0 CCR1 Output trigger (ADC12SHSx = 001)

With the information I have, I figured that if the CCIF bit of TA0CCTL1 register got set, it will trigger an ADC conversion, and when the conversion is finished and stored in the ADC buffer, an interrupt service routine will be triggered

I have written my code according to the information I have, build the project, and debug it, but during my debugging session my MSP430 never jumps to my ISR routine.

Can someone help me with that issue

This is a sample of the code I have written:
inside the main() function:

int main (void)
{
    //code

    init_Timer ();
    //configures TA0 CCR1 to 50 ms

    init_ADC ();
    //ADC12SHSx = 001 (Trigger is TA0 CCR1)
    //ADC12IER0 = ADC12IE0; enables ADC12 Interrupt

    ADC12CTL0 = ADC12CTL0 | ADC12ENC; //enable Conversion

    _BIS_SR(GIE);//enable global interrupt

    //rest of code
}

inside the ISR function

#pragma vector = ADC12_VECTOR
__interrupt void ADC12_ISR (void)
{
    static int x = 0;
    ++x;
}

EDIT_0

inside the init_ADC () function

void init_ADC (void)
{
    ADC12CTL0 = ADC12ON | ADC12SHT0_2;
    //ADC ON, 16 ADC12CLK

    ADC12CTL1 = ADC12SHS_1 | ADC12SHP | ADC12SSEL_1;
    //TA0 CCR1 Output, SAMPCON from Sample Timer, ACLK

    ADC12CTL2 = ADC12RES__12BIT;//12 bit resolution

    ADC12MCTL0 = ADC12INCH_10;//A10 P9.2

    ADC12IER0 = ADC12IE0;//enable MEM0 interrupt (if it's value changed)
    ADC12IFGR0 = ADC12IFGR0 & (~ADC12IFG0);
}

Inside init_Timer () function

void init_Timer (void)
{
    TA0CTL = MC__UP | TASSEL__ACLK;//counts to TA0CCR0, and source from ACLK

    TA0CCR0 = 1667;//50 ms count = 50/.03 (Tperiod of ACLK = .03)
    TA0CCR1 = 1667;// 50 ms
}

END of EDIT_0


texts:
I'm reading the datasheet of a PSRAM (available here). In the top-right hand corner all the pins are listed. Some of the pin names end with a hash, e.g. LB#, OE#.

What does the # notation mean for pins?


texts: How to find Emitter and Collector of an LDR

texts:
How can we find the emitter and collector of an LDR. I am using it in the following circuit but I don't know how to identify which terminal of the LDR is emitter or collector.

Here it is mentioned as Photo-transistor but it is basically 2 leg transistor which is hard to find in the market so I decided to use LDR.


texts: I'm aware that in Gray code the successive numbers will differ only by one bit. However I'm not able to proceed further.


texts: Whats the name of a BMW iDrive type of encoder?

texts:
I am looking for a component that some people call a 7 way encoder switch.

Basically, if you look at the center piece of the BMW iDrive, its that.

It's a knob looking piece that if you turn to the sides it behaves like a D-Pad. Grabbing it and twisting behaves like a rotary switch. Pushing down makes it a button.

I'm trying to find an electronic component that can do those things.


texts: Will the same C code for an AVR microcontroller work with any other type?

texts:
I'm learning about microcontrollers and have very limited knowledge on the subject.

I just know that one needs to set bits in the registers and manipulate them basically to make a uC work. The registers setup and control the electronics in the micro-controller.

Lets say I wrote a C code in Atmel Studio for a particular 8-bit uC. This uC has register names in its data-sheet like TCNT0 for instance. What if I want to use the same code with another 8-bit AVR? Should I write everything from scratch or just need to make little modifications? Are most of the register names in common?

For example, if I program an ATmega328P with C, would the same code work in any other 8-bit type for example with ATmega168? And if no, would you normally write it from scratch or just modify the previous one?

I'm confused about the code compatibility. How about same question for using 8-bit uC's code for a 32-bit uC like AVR32?


texts: How can I debounce a switch on both positive and negative-going edges?

texts:
I would like to connect a mechanical switch to an interrupt pin on an Arduino Uno processor where the interrupt is configured for CHANGE interrupts (i.e., triggers on either a positive-going or negative-going signal).
I've found numerous approaches for implementation of debounce circuitry for positive or negative going signals, but I have not found suggestions for circuitry that can debounce either positive-going or negative-going signals.
Essentially, I want to use a single interrupt pin that can detect the opening or closing of an external switch, and I'd like to debounce the input using a hardware approach.

To be a bit more specific, the switch in question will open and close up to 200 times per second and I'd like to determine the amount of time it is closed each time it goes through an on/off cycle. I.e., I'm not talking about a button pushed by the user.


texts: Arduino: Delay of 1ms necessary between Serial.read and Serial.write?

texts:
We have a Razor IMU (10736) sensor board connected to a RS-485 Breakout board, talking RS485 to the computer via a USB-RS485 Serial Interface. We use the Arduino IDE to program Razor's on-board ATmega328 (code is based on the Razor AHRS open source firmware).

Everything works fine, but for one detail: The Arduino-programmed Razor seems to need a small delay between the reading-in and the writing-out of a serial message. The way it works, is: the computer polls the razor, the razor reads the request and then responds by reporting it's data. The code looks like this (simplified) :

if(Serial.available() > 0) {

  int incoming = (int) Serial.read();    // read data
  delay(1);                              // ??? why necessary ???
  digitalWrite(RTS_PIN, HIGH);           // RE high, sets RS485-board to transmit
  Serial.write(c);                       // send data
  delay(1);
  digitalWrite(RTS_PIN, LOW);            // RE low, sets RS485-board to receive

}

There is the need for a delay of minimum 1 millisecond between executing Serial.read() and any form of output (digitalWrite and/or Serial.write()). We tried setting the value lower into the microseconds range, but always got corrupted data packages as a result. This problem does not occur when you only poll the razor once in a while, but when you repeatedly poll it at short time intervals (the computer waits for a response and then automatically triggers a new polling). This all is happening at a baud rate of 76800 right now.

Next we did tests by programming the Razor's on-board ATmega328 directly with C code. And this eliminated the need for the delay value! Reading and writing serial data could happen right after each other. But - as we'd like to stay within the Arduino language (for several reasons) - we'd like to figure how we could solve this problem in other ways.

In the Arduino firmware, the Serial library, is there any reason why there would have to be a delay of 1ms between Serial input and Serial output? And if yes, are there ways of changing that?


texts: Why is the delta connection called constant kilowatt and the star connection called constant torque in pole changing motors?

texts:
In a dual speed motor, they usually associate the series delta connection to constant kilowatt or constant power.
I understand the relationship P = Tw but what I don't understand is how delta and constant power associate. I also don't quite understand how star and constant torque associate.

I have attached a picture to clarify my question. I am referring to those diagrams.


texts: Does a modified "continuous rotation" servo typically create an H-bridge motor controller?

texts:
A common technique for driving small hobbyist robots is to make a "continuous rotation" servo by replacing the feedback potentiometer with two resistors of equal value.

Does this modification typically make an H-bridge motor controller?


texts: Capacitor in presence of an external electric field

texts:
Let's consider a capacitor made of a couple of parallel metal strips (suppose they are made of perfect electric conductor) as shown in the figure, which represents a little capacitor.
Suppose an external (time variant) electric field is applied in the space in which the capacitor is placed, as shown in figure.

Such an electric field may be for instance that of an incident orthogonal electromagnetic wave, as shown in the following picture.

What happens? I don't know which are cause and effects in this situation.
I'd say that:

The external electric field induces separation of charges in the two strips. So, plus charges on one strip and minus charges on the other.

The previous situation is like that happens on a capacitor when supplied by a voltage source. But, in such a case, I'd say that the voltage source provides charges to the capacitor metal plates, and then the resulting charge distribution generates the electric field. In this case, however, the electric field is already existing since it's the external electric field (the incident wave).

In other words, is the electric field between the plates the original external incident E field or is it the E field generated by the charges separated by the original incident E field?


texts: How can I predict the spread/span of a single IR beam?

texts:
I want to project an IR field across a 5 inch hole to detect if an object passes thru it like a mouse, a ball or other such object; say a 4 inch ball, how can I determine or predict the spread or span from the point of origin of a single IR beam across the 5 inch hole?

Ultimately I want to know when the IR field is broken and register the event.

I have NO real practical experience with electrical engineering and realize I may just have to find an engineer in the real world and discuss this but thanks.


texts: Connect two Arduinos via simple Serial connection

texts:
I have two Arduino UNO that I can't get to talk to each other.
I made the following connections

A <---> B
0(RX)   1(TX)
1(TX)   0(RX)
GND     GND

I have then, in my code (running on both boards):

void setup()
{
  Serial.begin(9600);
  // ...
}

void loop()
{
  if (Serial.available() >= 1) {
    in_sample_value = Serial.read();
    in_sample_available = true;
  }
  if (out_sample_available) {
    Serial.write(out_sample_value);
    out_sample_available = false;
  }
}

in_sample_value is consumed in a ISR (that also sets the in_sample_available flag to false), out_sample_value is produced in another ISR (that also sets the out_sample_available flag to true).
The problem is that both TX leds on both boards are continuously on but the RX leds are completely off on both boards.
I know that the ISRs are running because I tested them. Can you see what I'm doing wrong?

Addendum

To create a minimal test-case I just wired together pins 0 and 1 on one of the two boards and ran the following:

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

uint8_t count = 0;

void loop() {
  Serial.write(count++);
  Serial.read();
}

As said above, the TX led is on, the RX led is off.


texts: Brushless motor control poisition (design own PID?)

texts:
I got a few motor similar to the image below from a old scanner and I want to apply them in a robotic arm to move the arm because BLDC motors have a large torque I then control with arduino. Well, in order to do that I came across that maybe I would need to control their position moving at 60 rpm would be a reasonable speed (PID controller right?). Also the specification of a similar motor is at the link below to more informations.
https://www.nidec.com/en/product/search/category/B101/M102/S100/NCJ-42M-FeH/

Questions
Where I can find a step-by-step instructions to build my own PID like hardware needed, electrical circuit used, etcc?

I really appreciate your support guys!!


texts: Sampling rate for a real signal, which is not band-limited?

texts:
I have a question about Sampling Theorem. Sampling Theorem states that a "band-limited" signal can be exactly reproduced if it is sampled at a frequency F, where F is greater than twice the maximum frequency in the signal.

But mathematically, a signal can never be truly band-limited. A law of Fourier transformations says that if a signal is finite in time, its spectrum extends to infinite frequency, and if its bandwidth is finite, its duration is infinite in time. Clearly we cannot have a time-domain signal of infinite duration, so we can never have a truly band-limited signal.

My question is that, how do we calculate the sampling rate for a real signal, that's not not band-limited?


texts:
I've got a project in which I have video output from a camera which I can have in either video out or HDMI out. This signal, then, is to be sent to a Raspberry Pi to be used in a computer vision application. The Raspberry Pi can process video through MIPI/CSI-2 or through USB as a standard webcam. I have looked at HDMI to MIPI/CSI-2 conversion boards, and they can run pretty expensive. I think this is because of low demand. At the core of these conversion boards is a TC358743XBG chip from Toshiba.

My question is

a) How feasible is it for me (I have soldering experience) to make my own conversion board (purely from a hardware perspective- I'll worry about drivers later)?

Would it be possible to adapt this project to suit my needs?

b) Might there be a better way?


texts:
Phase voltages of three-phase circuit with Y configuration are equal by absolute value and phase difference between them are \$2\pi/3\$ and \$\theta_A=\theta_B+2\pi/3\$ and \$\theta_A=\theta_C-2\pi/3\$. find complex values of all phase and line voltages if \$u_A=100\cos( 2 \pi ft) V\$ where \$f=50Hz\$.

This is not that hard, I mean, after all, all I have to do is to determine complex voltages. Since I have \$u_A\$ I could easily find \$U_A\$ complex.

\$u_A=50\sqrt{2}\sqrt{2}\cos (2\pi ft) V\$ which means that I already have effective value and phase which is enough for complex representation of this voltage

\$U_A=50\sqrt{2}e^{j0} = 50\sqrt{2}\$ and from this point I could easily find other two complex phase voltages and then I could find line voltages simply by subtracting corresponding phase voltages.
But, the problem is that I don't know what the use of the fact that I know the frequency, I mean there's reason that's the given value, but the way I solved this, it turns out that I don't need it, is there something I did wrong? Why is this frequency given to me as a known value?


texts: Why does a 10A fuse blow at 10A and 5V or 10A and 500V?

texts:
Something that's always puzzled me:

Wire and fuses can handle a given max current, pretty much regardless of voltage. A 10A fuse will blow if you exceed 10A, if the voltage is 5V or 500V.

Why is that in terms of the physics? The total energy through the fuse is amps times volts.

Intuitively, I would expect a fuse to blow at some power limit. I'd expect a fuse to blow based one the number of watts of power pushed through it. How is it that a skinny little wire in a 10A fuse can handle 5000 watts at 500V, but will blow with only 50 watts at 5 volts.


texts:
I want to handle 8 and more buttons or switches with only a few MCU pins and receive interrupt whenever some of the buttons is pressed (even if some switches are active).

I'd like to use PISO shift register to read data from buttons and switches and place voltage dividers with different output voltages on each button (shown at image below). Output of all voltage dividers will be connected to the derivative amplifier which should register any voltage change whenever any button is pressed.

Because more then one button can be pressed at the same time and supply voltage for voltage dividers will be 3.3 V, I'll need to detect voltage change less then 0.3 V, but when I make derivative amplifier with bigger gain, I have a large noise (i have negative voltage source for op amp made by inversing charge pump - image below - is possible that the noise is generated here?).

I would like to help with choosing components values for derivative amplifier for the smallest noise and the bigger gain.

update:
Thank you all for your suggestions. You have right about circuit complexity, so continuous checking of buttons state will be the best way.


texts: Will this setup trip RCD or cause any issue?

texts:
I want to mix a function gen’s output with a 50Hz mains signal which is stepped down by a 24:1 transformer as follows:

Is this setup safe? A scope will monitor the composite signal.


texts: What circuit should I study, to learn all the details of the 555 timer?

texts:
I understand OHM's Law, and have a conceptual grasp of RCL circuits, but am a little weak on the math. I am good at math, even a little calculus, just weak on RCL math.

I am trying to understand the 555 timer. I have seen various 'cookbooks', but it's like someone is trying to teach me about internal combustion engines, when I don't understand campfires.

The monostable multivibrator is generally presented first, but it does not utilize each pin individually, as some are tied together. I am trying to get a snapshot of all features offered by the 555.

I have figured out that, if I have a push button providing the trigger signal, I would want to have a capacitor in series, to limit the pulse width. Regarding the value of the capacitor, I suppose I could use trial and error.

I have a breadboard and some components on order. I'm just trying to read up a little bit in the meantime.


texts: Why this Plier is advertised with conductive handle?

texts:
See the product here.

Ok, I cannot think why I would want the handle to be conductive. What is the deal?


texts: Is it good using INA213 to amplify +/- 33mV to range 0 -> 3.3V?

texts:
I need measure AC current range 0 - 25A using current transformer and burden resistor, voltage swing from -33mV to +33mV. I searched and found INA213 (datasheet). Can I use 3.3V power supply to INA312 or need 5V? Vref is 1.65V (LM358 buffer from voltage divider) and measure by STM32's ADC. As my title, is INA213 suitable for my case?
Thanks


texts: How is this ground fault circuit working?

texts:
I am having a difficult time understanding a few things in regards to the ground fault detection circuit below. I have found this circuit while investigating ground fault detection. I intend to build my own circuit for use in my system and am using this as a starting point.

Note the circuit below is to be matched with this CT.

Now, my questions are...

I assume the intent of D1 is to provide over voltage protection. However, I don't see how that works with this particular diode. These are standard Shottky diodes which don't conduct when reversed biased. Why not just use a TVS for this sort of thing? I must be missing something here. I feel silly asking...
R17 becomes the burden of the CT and develops a voltage proportional to the current. This particular circuit uses a value of 330 ohms. If I understand the CT datasheet correctly that yields a voltage around 6.5V at the rated current which doesn't seem like a good choice. However, I am not sure I read the datasheet correctly. Is Te turns ratio? How do I chose the value R for a GFI situation? The data sheet recommends choosing R such that V < .8 Vl but they fail to specify what Vl is (or perhaps I should know this).
The threshold for tripping is set by R15 and R14. C14 would add some delay. R16 and R20 act to amplify the current reading. How would appropriate values be determined here? In other words, what's safe or customary?

Note that this is a one off design which wouldn't necessarily have to conform to any regulations but I'd still like to get a handle on this.

EDIT:

The AC leads (hot, hot, ground) will enter the enclosure and run to relay contacts. The leads then run from the relay contacts and exit the enclosure. I was planning only to run the two hot legs through the CT right where they enter the enclosure.


texts: In clamper circuit why RC>>T ? and why diode becomes reversed biased as capacitor becomes fully charged?

texts:
In clamper circuit why time constant is very very greater than time period of the signal i.e, RC>>T where R=resistance, c=capacitance, T=time period.
why diode gets reversed biased as soon as the capacitor is fully charged?


texts: What does common mode voltage stand for in an instrumentation amplifier?

texts: I was reading a text about instrumentation amplifiers. I couldn't find any easy explanation what really common mode voltage means and its importance.


texts: Why different coil power versions for a relay?

texts: This relay is available in coil powers of 150mW, 200mW, 400mW and >500mW. Why does Tyco make all these versions? Wouldn't everybody want the least power-demanding version? In other words: what's the advantage of the higher power versions?


texts: Limiting current draw on a camera battery charger

texts:
I have a camera battery charger which is driven from a 12V (measured 12.2) switched mode wall wart rated at 1A. All three items (charger circuit, wall wart and battery) are stock, but all three heat up pretty quickly, which got me worried. The items work - the battery gets charged - but all items, especially the wall wart, are very hot in the end. I measured the current through the wall wart cable to be 1.5A. Now how should I go about limiting it?

I thought about adding a 4 ohm resistor in series with the wall wart supply, as I calculated would be adequate. I also thought about adding a few diodes in series to drop the voltage, but I was worried, it might interfere with the internal circuitry of charger (there's a couple of ICs and inductors and what not in there, too complicated for a beginner like me to reverse engineer).

Or would I need an active current limiting circuit?


texts: Electromagnetic interference to my project

texts:
I am working on a project for couple of months and eventually it gets completed and worked perfectly on the test bench. But the issues arise when I installed the system.
Let me show you some pictures of my project,

The controller part

The LCD and sensors

The full system

This system is intended to do few jobs:

LCD shows the date, time, temperature and humidity
There is a mobile app (self made) which is used to set the color of the led strip and control the relays and couple of other things
IR remote is there to control the led strip and relays
Couple of other things like alarm

To make it more clear let me give a brief about the system architecture.
Microcontroller reads the clock data (like date, time) form DS3231 RTC chip and reads the temperature and humidity from dht11 sensor and shows it to lcd. Here pcf8574 I/O extender used to control lcd, this chip works on I2C protocol. Bluetooh kit does the serial communication with Microcontroller . IR receiver tsop1738 take the IR remote date and send it to microcontroller. Microcontroller is programed to do certain tasks as per the serial or IR data.

If I set alarm then the time signature will be stored on the ROM and during first power on(boot) time it will be read. ROM is used to ensure the reliability even power failure. Buzzer is the alarm output.

Shift registers (74hc595) are used to control a number of relays only for the cost of two I/O pins of the Microcontroller. Here cascading input used between the Shift registers.

LED strip controller board has 3 high current transistors(NPN) in order to power up the strip. PWM pins of the Microcontroller are used here on transistors' base.

The connection between LCD box and the controller board is done by a CAT6(Cable used for the internet connection) or LAN cable.

This cable consists of 8 wires in 4 pairs and each pairs consist two wires which are twisted with one another. Now here 6 wires are required to make the communication between LCD box and the controller board,

5v
SCL
SDA
DHT11 output
IR reciver output

SCL, SDA, IR reciver and their respective pairing wires are connected with GND. I do it to reduce the electromagnetic interference. I don't know whether I do it right or wrong. A 1000mf and a 470mf capacitor used in the LCD box.

These relays are used to control the electrical devices like bulb, Fan.

The whole system is powered by 12v 4amp transforma. The -ve or GND pin is connected with the earthing connection.

Now the issue is, when any of the switch from the switchboard (The AC switches to on/off fan, light etc) is pressed(either on or off) some unexpected things are done as for examples LCD shows some unexpected characters, relays get turn on or off (means abnormality on shift registers). Even some times, system stop responding to makes it responsive again needs a reset. I failed to understand the issues. Height difference between lcd box and microcontroller is about 7ft.
I power up the system with UPS (independent form the main line) but issues remain same.

I will be thankful to you for your useful suggestions.


texts:
I am using a custom code of CDC example from 177x_8x_PDL_110602 package (I am not using LPCOpen).
I am having a trouble with CDC_Send function. That is the scenary: An python script send messages to LPC1788 serial USB, they are send time to time (200ms,300ms). The message is: "ping\x00", without quotes. When the LPC received the ping message it send back to PC this message: "resp 0\x00". After any time of messages interchange (perfectly), the LPC begins send the message wrong, like this: "r 0\x00", "sp 0\x00", "esp 0\x00", "r\x00", "\x00", ...

Bellow is the code that send the message:

void CDC_Send(const uint8_t *data, uint32_t data_size)
{
    // block until all bytes be sent
    while (ringbuff_size(g_tx_buffer) > 0);

    // puts the data into ring buffer
    ringbuff_write(g_tx_buffer, data, data_size);

    // forces the first send
    CDC_BulkIn();
}

void CDC_BulkIn(void)
{
    uint8_t buffer[USB_CDC_BUFSIZE];
    uint32_t bytes_to_write;

    if (!g_cdc_initialized) return;

    memset(buffer, 0, USB_CDC_BUFSIZE);

    bytes_to_write = ringbuff_read(g_tx_buffer, buffer, USB_CDC_BUFSIZE);

    if (bytes_to_write > 0)
    {
        USB_WriteEP(CDC_DEP_IN, buffer, bytes_to_write);
    }
}

The SetMode (command 0xF3) use the reset value (zero), so don't happen interrupts by NAK.
After a lot of time debuging I tried to put a delay after USB_WriteEP function, the delay value is 100us. In this way the messages interchange don't fail. So, I would like to fix this (remove the delay). Any idea?

Thanks


texts: Where to find a Microchip MCU's ADC AC characteristics?

texts:
I'm trying to calculate the ENOB bits of my a PIC18F26K22 ADC, the problem is that I can only find the DC error specifications, namely, Gain Error, Offset error, Integral Linear Error,etc.

But I'm looking for AC specifications,like SNR, ENOB or Total Harmonic Distortion. I tried to find in several PIC18 family devices and even in Pic32 datasheets and all show the same kind of DC characteristics. The typical table I found is like in the figure bellow. Is this type of ADC so bad for AC that they don't even bother list its characteristics ?


texts: Ideas for safe connection from panel-mounted socket to PCB

texts:
I have a panel-mounted socket with the geometry shown in the images. Inside the enclosure this sockets ends with a male gold-plated pin, diameter 1.9mm.

Any ideas on how to connect from this male pin to the PCB in a way that 1. is safe (strong mating from the pin to whichever female connector is chosen) and 2. can be unplugged for servicing of the PCB if needed? (soldering at both ends of the wire would not be convenient), 3. needs limited space (it is a small encloure).

Note that the 1.9mm male pin at the back of the socket is round. No sleeve available for easy soldering of a wire directly to the socket. It seems easier to find a female socket (RED in the image) that matches de 1.9mm and then solder the wire only at the PCB's end.

Any advice based on experience on how to solve this?


texts:
Let's look at the next circuit:

simulate this circuit – Schematic created using CircuitLab

Will electric current go through R1 in the real world?
Is ground like a conductor with some R supposedly > than R1, and can we illustrate this like that :

simulate this circuit


texts: Why is a Instrumentation Amplifier Necessary for A Wheatstone Bridge (small signal circuits)

texts:
I do not understand why an Instrumentation Amplifier is Necessary for small differential signals?

Why is it necessary that the initial inputs to the amplifier must be high impedance from the Wheatstone bridge? Since technically after the input voltages have been buffered and amplified, arent we back at the same differential amplifier stage that contains a low impedance input. Therefore wouldnt this low impedance input for the diff amp change the accuracy for the output?

My Questions

1. Are the input stage gain buffers required so that the wheatstone bridge voltages do not change? Since if it went into a differential amplifier immediately, the amplifier would draw current by itself due to its low impedance correct and so this may cause voltage inaccuracies?

2. After the buffers have outputted there voltage, does the differential amplifier not change the voltages since the low impedance can cause voltage drops etc? Or is this not the case since after the buffer, the output voltages (before R2) is like a source and so the amplifier draws the current separately. When compared to if just a differential amplifier was used the current would be the Wheatstone bridges resistance + the amplifiers resistance. Hence what I am trying to say is since the buffer separates the diff amp from the Wheatstone bridge the input voltage to the diff amp will be accurate.

Will there still not be a voltage drop across R2 and R3 which will change the input voltages to the differential amplifier from the output of the buffer gain amplifiers. Or is this ok for the differential voltage since these voltage drops will be constant and so the change in the inputs stays the same?
If number 3 is the case, then why is the low input impedance of a single differential amplifier bad if a Wheatstone bridge was directly connected to it? Since as these input impedances are constant wouldn't the voltage change still stay the same?


texts: Connector Choice for Arduino/MIDI Bridging Interface

texts:
I'm in the early stages of planning a MIDI-mapping component that I can plug into my Alesis DM-6 drum kit so I can ultimately play it through Rock Band 3. I know there are commercial options out there, but I'm intrigued about building one (at probably 5x the cost, no doubt :P).  Everything I've read about this talks about requiring an extra set of patch cables to plug into each drum which then plugs into the Arduino black-box.

Anyway, my question is this: Is there a specific reason the connector of choice for each drum (not to mention guitars, etc.) is the 1/4" phono?  I could probably get away with a much smaller box if I can use 1/4" on the drum-plug side, but the smaller 1/8" (3.5mm) phono on the box-side. Am I losing anything by using 1/8"(3.5mm) connectors going into my device? Other than being more 'durable' or maybe having a tighter-fit, are there electrical or noise/interference/impedance/other issues using the smaller connectors?

Thanks!


texts:
We have a device which can work with dry contact input and a device which gives open collector output. Will it inter-operate?

Is there any difference between dry contact mode output and open collector output?

If a device works with dry-contact input, does it work straight away with open collector input?


texts: What tools can I use for parametric circuit analysis?

texts: I have analog circuit designs that I want to analyze for accuracy, etc. according to the component variations based on tolerance, temperature, etc. To elaborate further, imagine there is a circuit designed with couple of resistors and an opamp, and based on their nominal values we have an expected output. How does this output change based on the possible changes in the circuit element parameters? (tolerance and temperature dependency of the resistors, offset voltage and bias current of the opamp, etc.)


texts: Calculate maximum current when charging a capacitor using a MOSFET

texts:
While preparing for an exam I came across the following problem, unsure how to solve it. The following values for a fully charged capacitor are given: \$ V_{in}=2V, V_{C}=1V, V_{th}=0.5V \$.

Whats the maximum current flowing into the cap when \$ V_{in} \$ is suddenly raised from \$ 2V \$ to \$ 2.5V \$?
Whats the maximum current flowing out of the cap when \$ V_{in} \$ is suddenly lowered from \$ 2V \$ to \$ 1.5V \$?

I am not sure how to even approach the problem. There is no \$ V_{dd} \$ given, so I don't know in which mode the MOSFET operates. Can someone help me out?

simulate this circuit – Schematic created using CircuitLab


texts: Eagle Change all part names (Designator)

texts: I would like to change all my part numbers(Designator Name) one by one, but Eagle does not allow to change a component name with a name that already exists. So what is the fastest way to change all parts name?  (I already know about renumber ULP function but it does not let you pick your own name)


texts: Controlling a motor with Alexa enabled WiFi switches

texts:
I am looking to replace a DPDT switch, which controls a DC motor, with switches that can be activated using Alexa/over WiFi. For my purpose, the motor needs to spin in both directions, so the polarity needs changing using the switches.

I am wondering if it would be possible to control a motor and reverse its polarity simply using these switches? I am assuming they are SPST switches. I am wondering if it would be possible to create a DPDT switch using a combination of the switches: https://www.amazon.co.uk/Sonoff-Control-Wireless-Compatible-Compatible/dp/B079CL1B5D/ref=sr_1_9?keywords=alexa+switch&qid=1577146354&sr=8-9

Otherwise, if anyone has another solution (or perhaps knows of a DPDT switch on the market that can be controlled via Alexa?), I would be very grateful as I am not an electrical engineer!


texts: How does an antenna differentiate between different signal waves?

texts:
I'm aware there are frequency filters, but at the electron and EM field level, if there are multiple waves directed at an antenna, how does it differentiate between 2 different waves and frequencies?

If wave1 is captured by an antenna, how does the filter/antenna know that there is another wave2 and that the E field is related to a different wave?

How does it know that those excited electrons are from wave1 and not a part of wave2 for example?


texts: Why is this boost converter application circuit done this way?

texts:
The schematic below comes from boost converter AP6714 datasheet - so I assume it's good, but it is very atypical.

Most (all that I used) of the impulse power converters have VOUT connected to the coil. This one has VIN connected to the coil.
Also why is this converter powered (VCC) from VOUT? How is it supposed to work? Usually you power PC from VIN.


texts: How can I add an offset voltage at the input of an instrumentation amp?

texts:
I want to measure the voltage of an H-Bridge Sensor. However, due to the manufacturing process, the bridge has an offset several times larger than the useful signal (it can easily measured by inverting the bridge sensitivity direction). I want to subtract/add this voltage at the input of the in-amp. Can this be done? If so, how?
I know I could use a summing circuit with a simple opamp like here:
https://en.wikipedia.org/wiki/Operational_amplifier_applications#/media/File:Op-Amp_Summing_Amplifier.svg
However, using an inamp would spare me using high precision resistors and loading the bridge with unequal impedances.

Could a similar thing be performed with an in-amp instead of a normal opamp?
Background: The Bridge-Sensor can be switched in direction. E.g. you have 10mV offset and 3mV actual sensor voltage. You reverse the sensitivity so you have 10mV offset and -3mV useful signal.
To get the signal you measure in reversed and non-reversed mode and subtract (after measuring with an ADC): 10+3-(10-3) = 3+3. You divide by two and get your useful signal, 3mV. I want to specifically add the offset at input level, not at output level, because I am amplifying a little bit of useful and a lot of (useless) offest.
The sensor I want to use is the HMC1002. Thanks!


texts: Running an LED blinking program on cc2530

texts:
I am trying to use the following code for blinking LED on CC2530, it would be great if someone could tell me what I am doing wrong? I know this is basic stuff but I cannot figure out what I am doing wrong! The LED is mapped to port 0 and 7th pin (06).

I am using IAR to debug the program, when I run it in steps, LED do toggle! but when I run it without stopping, LED just glows, I thought it might be because of delay being miniscule, but no matter what value of delay I use, it just glows without blinking.

#define LED1_MASK  0x40
#define LED1_PIN   P0_6

int main()
{
  P0SEL &= ~(LED1_MASK);
  P0DIR |= (LED1_MASK);
  while(1)
  {
   //clock_delay(10000);  // i tried running empty for loops and NOP for loop too.
      LED1_PIN = 1;
      for(int i = 0; i< 1000; i++)
      {
        for(int j = 0; j< 1000; j++)
        {
          ASM(nop);
        }
      LED1_PIN = 0;
   }

EDIT: This is the actual program I am running, I made a mistake while pasting before (wasn't changing value of LED_PIN in the code). I am sorry for the trouble.


texts: differences between mini pcie vs half height mini pcie

texts:
I want to use a mini- PCIe half height to connect a communication module to my PCB.
For example- to use a board like the raspberry pi 4 compute module io board with a WiFi expansion board.
Given that I can arrange enough space and heat dissipation is not an issue for using both of them, are there differences between them except for their dimensions?
can I connect a mini pcie and afterwards replace it with a half height one?


texts:
Inserting a breakpoint and checking the result of data exchanged between 2 uC's tend to interfere with the timings and other factors.
Is there a way wherein i can sniff all the data exchanged between 2 uC's and store them to a log file that can be later interpreted maybe using python.

Even if it means using a #define to Enable and disable logging in code is fine.
I just dont want to use breakpoints and verify the results.


texts:
I'm looking for a temperature sensor, that can be connected to a computer over an interface that is ubiquitous, like USB. I'd like to read the temperature data over the command line.

Any suggestions what I could use?

All I plan to do, is measure the ambient temperature in the vicinity of the computer, for instance 2m above it.

I can access internal sensors with sensors, of the lm_sensors package. If possible, I'd like a similar interface.


texts: charging 10Ah li-ion batteries in parallel

texts:
i'm trying to charge a 5Ah single cell li-ion battery using bq24090 charger controller (up to 1A fast charge current) in parallel with a current boosting circuit. Overall controller should supply fast charge current at 0.5C rate(2.5A), theoretically. Which idea does make sense if i try to charge 4 of these li-ion  batteries?

option 1: using 4 distinct charger controller as described for each one of the batteries

option 2: using single more advanced charger controller such as bq24600 (up to 10A fast charge current) and supplying 4 parallel batteries from that single output of the controller.

Thank you.

datasheets

bq24090    http://www.ti.com/lit/ds/symlink/bq24090.pdf

bq24600    http://www.ti.com/lit/ds/symlink/bq24600.pdf


texts: What is the purpose of this PLC circuit?

texts:
I am reverse engineering the PLC I/O module. One output consists of a Smart Switch with 3 additional components.
Obviously, this is some kind of protection.

But how does it work?

Updated:

PCB photo:


texts: FT2232 device not accepting address x, error -71

texts:
I have designed a board with an USB IC from FTDI (FT2232D).
This board is bus-powered (i.e.: gets its power from the USB bus). Nothing else gets the power from the USB bus except this IC and its EEPROM (AT93C46A).

I followed the datasheet to design the schematics, however the XTAL is 12MHz instead of 6MHz.

When I plug the board into the USB of my Ubuntu computer, it is not get recognized, here are the error messages from dmesg:

[231.641237] usb usb3-port1: attempt power cycle
[232.265187] usb 3-1: new full-speed USB device number 5 using xhci_hcd
[232.265294] usb 3-1: Device not responding to setup address.
[232.469563] usb 3-1: Device not responding to setup address.
[232.673176] usb 3-1: device not accepting address 5, error -71
[232.785183] usb 3-1: new full-speed USB device number 6 using xhci_hcd
[232.785298] usb 3-1: Device not responding to setup address.
[232.989331] usb 3-1: Device not responding to setup address.
[233.193179] usb 3-1: device not accepting address 6, error -71
[233.193229] usb usb3-port1: unable to enumerate USB device
[249.869089] usb 3-1: new full-speed USB device number 7 using xhci_hcd
[249.981069] usb 3-1: device descriptor read/64, error -71
[250.197071] usb 3-1: device descriptor read/64, error -71
[250.413055] usb 3-1: new full-speed USB device number 8 using xhci_hcd
[250.525070] usb 3-1: device descriptor read/64, error -71
[250.741082] usb 3-1: device descriptor read/64, error -71

Here is the schematics of my design:

Here is the layout of my design:

I have measured the cable pins to the IC and all are well connected. (i.e. cable is all-good.)

This should normally work, right?
What else can I try?

Thanks!


texts:
I inherited a Weller WTCPL soldering station a while ago:

It was my grandpa's, and although I can't find a direct reference to it anywhere on the net, I'm guessing it's anywhere from 40 to 60 years old. It worked for some time, but sadly, it recently has stopped. When I was soldering the other day, I noticed the wand getting progressively colder, until it eventually wouldn't even melt solder. Now, it turns on (or at least the indicator light does), but the iron does not heat up. Is this fixable or do I need a new iron?


texts:
I seem to be going through soldering tips at a breakneck pace. Four or five hourly sessions, and it's corroded all to hell.

Does this sound about right, or is there something I should be doing differently? It's a standard 40 watt cheapo iron.


texts:
I was reading part of the hspice tutorial, I found that, there is a multiprocessing option:

"hspice -mp [process_count] -mt [thread_count] -i input.sp -o output_file"
"Note: Running both MP and MT simultaneously is limited only to LINUX."

Is there anyway to use those options on Ubuntu system?
I tried it, I got "Syntax error: Bad fd number".


texts:
I want to use the direct time of flight method to measure the distance between a person carrying an arduino and a certain part of the room. I have come across many different boards which can easily be connected to the arduino to measure distance using the reflecting time of flight method, but because of the nature of my project, these boards won't work for me.

I have sourced these sensors: Pair Aluminum Housing 40KHz Ultrasonic Transducer Transmitter Receiver. I am considering buying them, but first, I need to be sure that they will work. I have spent hours searching for instructions on how I can connect them to my arduino, but have had no luck.

Can someone please give me some simple instructions on how to connect this thing to my arduino? I basically need one of them on one arduino, which will transmit the ultrasonic wave at certain intervals, and another one on a separate arduino, which will listen for the ultrasonic waves.


texts: DC motor voltage divider with NPN, diode, capacitor, and separate battery

texts: I am trying to hook up a 9V battery to a 6V DC motor on a breadboard. The circuit on the breadboard has a 5V supply. Is the attached schematic correct in applying a 2/3 voltage drop from the battery to run the motor? I have the 1K resistor and emitter wired together and going to the breadboard ground, then my battery ground plugged into breadboard ground. Is that correct? Thanks.


texts: Different voltage readings when using different ranges on a multimeter

texts:
I'm using a digital multimeter to check the voltage on my motorcycle battery - I'm attempting to confirm the proper installation of a new alternator in the charging system.

The voltmeter has 3 ranges that I'm using: 20V, 200V, and 500V.

With the engine off the battery reads ~12.8V on all three ranges. But with the engine on (and hence the charging system going), the battery reads different voltages using each range:

20V range jumps around from 0-15 volts
200V range holds pretty steady around 17.5-18V
500V range jumps around from 40-100V

The multimeter is a brand new Equus Innova 3300: http://www.walmart.com/ip/Innova-3300-Equus-3300-Hands-free-Digital-Multimeter/14644665

I'm not expecting this community to diagnose the motorcycle issue, but does anyone have any idea what electrical behavior could cause these readings in the multimeter? Why would the readings be so different at each range?

I checked all the diodes in the rectifier (3-phase rectifier, 6 diodes), so I don't think any AC current is getting through to the battery/multimeter, which was my first thought here.


texts: ARM M4 based Microcontroller or Particle Photon drive multiple small colour lcds?

texts:
Hi I was just wondering if anyone had an example of running multiple small colour lcds from an arm based microcontroller or photon?

I'm hoping to run up to 5 lcds with photos.

Ideally if I could transfer the image data via http, store them and the display them when necessary that would be ideal.

I'm from a software side and trying to work out where to start hardware wise..


texts: Minimizing capacitive crosstalk in open collector quadrature speed sensor

texts:
I am integrating a speed sensor (Honeywell SNDH-T4L-G01) which comprises 4 lines: VDD, VSS, A, B. The last two signals provide speed and direction information in a quadrature format.

These are open collector drivers, therefore in the control unit side a pull-up resistor shall be provided.

As the cable length to the sensor is around 3-4m, I am concerned about the capacitive coupling phenomena, as the quadrature signals are expected to switch at 7khz worst case in a quadrature fashion. I expect that both signals should cross-talk each other due to the weak pull-ups.

Cable shielding is mandatory, however the classical shielding schema (aluminium braid shielded cable with GND connection in one end) would not solve the crosstalking issue in my opinion, due to the capacitance of the line, the weak pull-up of the lines and the strong pull-down driver of the sensors.

Is it a good solution that I shield separately (VDD+A) and (GND+B) with the GND connection (and thus the connection between these shields, to avoid loops) being made at the control unit end?

I know trial and fine tuning is usual in these issues, but I want to start with the best shot possible.


texts: Replaced battery on Galaxy s8 still gets recognized as 3Ah

texts:
My Galaxy S8's battery after 2 years is almost a brick.
I deceided to solder a 10Ah battery in the back (yeah the phone looks like a bomb now) because I want to create a cover which contains a battery that will be connected in parallel to the phone's battery (with resettable fuse as protection from shorts).
The problem is that now I'm using just the 10Ah battery and the phone doesn't recognize the new capacity: Accubattery measures less than 3Ah, while my imax b6 measured more than 6000mAh.
Is this due to an hard coded "3Ah max" in the circuits?
The cables can handle up to 5A, so they are not the problem (and even if they were, how is it possible that exactly 3Ah are measured?).
I really can't figure out the problem.


texts: I've read that in Profibus, both analog and digital signals can be transmitted on the same wire. I'm curious how this happens and wasn't able to find an answer on google. Could someone please explain or point me in the right direction.


texts: Confused how to draw the asymptotic magnitude Bode plot

texts:
I am trying to solve the following question:

I have derived the transfer function as follows:

$$H(\omega) = -\frac{2000}{j\omega} - 0.5$$

which I rewrote as the following

$$H(\omega) = -\frac{j\frac{\omega}{2}+1000}{j\omega}$$

What exactly do I do now?


texts: Double wave precision rectifier frequency response

texts:
To perform a didactic experience, I had to design a double wave rectifier by using op-amps (TL081). I choose to use two stages: a single wave precision rectifier (i.e. ideal diode) and an inverting adder in order to obtain a full rectified Vout starting from Vin.

simulate this circuit – Schematic created using CircuitLab

The circuit was easily mounted on a breadboard and tested, and it works very well.
The problem is its behaviour at "high" frequencies: from 8kHz on, the I/O characteristic starts to modify, thus I consider the circuit being no more reliable.
Let me show you the oscilloscope screenshot with a 10Vpp 16kHz sine wave as inpunt voltage Vin.

As you can see, the I/O characteristic is modified and it is no more V-shaped.

I can't understand if is this due to a different behaviour between the rising Vin and falling Vin, or to something else.
I can't understand why we experience that sort of "delay" between the Vin (yellow line) and Vout (light blue line), since the switching time of the used diodes is "4ns max" and the slew-rate of the op-amp is 13V/us (and, measuring its output, the max slope reached was 2.4V/us - moreover, the circuit was designed with low resistances to let the op-amp work well).

Simulations performed with LTSpice using the models of the real components gave the same results.
Thanks for your replies!


texts: Where can I find specific examples of parameters for a loudspeaker circuit model?

texts:
When I look around for loudspeaker literature, I often encounter an equivalent electrical circuit model such as http://en.wikibooks.org/wiki/Acoustics/Acoustic_Loudspeaker#Modeling_the_loudspeaker_as_a_lumped_system (image shown from the linked site):

Where can I find examples of component parameters (\$R_\mathrm{e}\$, \$L_\mathrm{e}\$, \$R_\mathrm{evc}\$ etc.) for such a model for actual loudspeakers? It does not matter which speaker it is. I just need a realistic model.

It does not have to be this exact circuit. I have also seen other variations of it and something reasonably similar will be OK.


texts:
I know about SparkFun.com, but their product line is limited to general appeal for the average hobbyist.  I appreciate them for that.  But when I want a specialized component, I'm not sure if vendors don't sell or if I'm looking in the wrong spots.

I find sites for chip manufacturers that make components I'd like to buy, but they never seem to publish their prices (why??), and some seem to have minimum quanities or minimum purchase totals.  I'm intimidated to ask for a quote on a single item.

Where does the hobbyist source high-end parts?  Should we expect a full product catalog with prices?  Any tricks to the ordering process?


texts:
We know that we have now 50/60Hz in our walls due to mainly historical reasons - back 100 years ago there were no ways to up/down scale DC voltage.

These days we just have problems due to that - every single device sold have to have ~1uF cap per 1W of power before it's PSU to have enough power when we go through 0. (this problem does not exist in 3-phase power, but it available mainly in industrial applications only AFAIK) + caps have to have higher rated voltage to survive sine peaks + all this PFC mess.

Is that correct to say that if we were to design modern power grid, we would skip AC, and just have DC everywhere? As far as I see, it would significantly increase reliability & reduce cost of many devices out there.


texts:
I am trying to compare power spectral density values (obtained from dsp.SpectrumAnalyzer) with PSD values obtained from hardware which has a VSA.
MATLAB's documentation says that " The power spectral density is the magnitude squared of the spectrum normalized to a bandwidth of 1 hertz." and expressed in dBm/Hz

whereas the hardware expresses PSD in units  dBm/RBW per 100 kHz    So,I'm assuming that it is normalized w.r.t 100Khz bandwidth
This is an example snippet of hardware's vsa( not my actual output)

Do I need to do any kind of conversion or something in terms of PSD ?
For ex:  dBm-->mW--> multiply by 100e3  something like that to properly compare? Kind of confused with these units.
MATLAB's output is off by approx 20 dBm

Here is the output comparison

EDIT>>>

0)  RBW is set to 100KHz on hardware and in MATLAB too
 1) I'm guessing there is a factor 100 which I need to multiply to PSD in mW to make it similar, but not sure why I need to do that

2)The reference load for matlab is set to 1 ohm by default, whereas  hardware (litepoint ) reference impedance is 50 ohms

3) Updating basic specAnalyzer code in matlab if that helps in understanding

nSpectralAverages = 3;
specAnalyzer = dsp.SpectrumAnalyzer('SpectrumType','Power density',...
                              'SampleRate',fs);
specAnalyzer.FrequencySpan = 'Span and center frequency';
specAnalyzer.Span = psdSpanLpVSA;
specAnalyzer.SpectralAverages = nSpectralAverages;
% Resolution Bandwidth
specAnalyzer.RBWSource = 'Property';
specAnalyzer.RBW = resolutionBandwidthHz;

specAnalyzer.AveragingMethod = 'Exponential';
specAnalyzer.ForgettingFactor = 1;
% Run the spec An and get collective result
specAnalyzer(WiFi_iqData_bw20MHz);
specData = specAnalyzer.getFramework.Visual;

I'm using exponential averaging method as its pretty clean and similar to litepoint's output

4) My other question is: Can I even compare outputs directly like this? Or should I just add the difference in spectrum peaks and then compare (after adding 50 Ohms to the MATLAB's output)

EDIT 5)
 I have converted dB/Hz (which matlab provides) to dBm/100Khz for comparison and also calculated power values for 50 ohm

Pwr in dBm/Hz --> convert to mW --> multiply by 10000/50 (100e3 for 100KHz and 50 for 50 ohms conversion)  --> then reconvert to dBm

Here is the output

Any comments /suggestions

Thanks


texts: Need suggestion on the selection of rechargeable battery

texts:
I am planning on to design a system to power my router. Unfortunately, there are shortcomings of electricity in our area and I want my router to operate 24/7.
I have read the specs of the router and it requires 12v/1A | 12watts.

What I want to do now is to select a Small size rechargeable battery so that I can power my router through it when my main electric power is cut-off. I thought about 3v7 LI-ION battery with a Boost converter but LI-ION can't provide me, ideally about 3.4A (12w/3v7) continuously. So should I connect two LI-ION in series (3.7x2) to drive Boost  converter i.e (12/7v4 = 1.62A) or there is another better approach which can be both cost-efficient and suitable for the above purpose?


texts: Can I use a 3.3V linear regulator to level shift a 5V square wave down to a 3.3V square wave?

texts: I have an output of a comparator that is a 5V square wave. Can I feed that square wave into a 3.3V regulator to get a 3.3V square wave? The 3.3V regulator I have is the LP2950.


texts: How can I make a Fuse Blown Indication LED circuit with variable voltage input?

texts:
I'm creating a power supply with an input fuse and and output fuse, and I'd like to have blown fuse indicators. However, the circuits I have found typically have set voltages and thus set resistors, which would give me varying levels of brightness, or not work at all. I'm using chassis mount fuse holders.

Input Fuse: 12V to 24V variable, but I'd like the same brightness regardless of voltage. If there's such a thing as a constant-current LED driver that's not very complex, this could work - there will always be 12V-24V on this when I'd expect the LED to be lit if the fuse was blown.

Output Fuse: 0V to 20V variable, and I'd like the LED to indicate blown even if the output voltage is 0V, but wouldn't want this voltage or current affecting the load (or requiring that there be any).

I do have a microcontroller on the board, and I could thus drive the LEDs with the digital output pins, but would prefer a solution that does not use it. Is such a circuit possible?

Essentially, I'd like to power the LEDs with a set voltage (I have 5V and 12V rails), irrespective of the voltage on the fuses themselves.


texts: Is connecting a 12V circuit to +12V and GND the same as connecting it to GND and -12V?

texts: After reading What is negative voltage? and the answer given by kellenjb I wondered if I understood the topic sufficiently, and started theorizing. If the + or - sign is just a convention and the voltage is the potential difference to ground, and my PSU has a +12V, -12V and GND connector, would it make no difference wether I connected a circuit to +12V and GND or to GND and -12V? In other words, say I had a 12V LED, could I connect the anode to GND and the cathode to -12V and still have it work same as when I connect the anode to +12V and the cathode to GND?


texts:
We are currently intending to purchase a TDR device (or maybe 2) to measure the impedances of various traces on PCBs but we are just at the beginning. Can you recommend some good devices or devices which are commonly used in the industry at the moment? What are the parameters I have to look at (I know that the rise time is the most critical one; but what else characterizes such a system)?

I know that shopping questions for parts are forbidden here but I hope that the some does not apply for gear as well. At least it doesn't for soldering irons from what I've seen in the past.


texts: Circuit for high voltage pulses using raspberry pi PWM to drive a piezoelectric actuator

texts:
I am trying to engineer a device to separate red blood cells from blood plasma in 100mmx1mm capillary tubes using the raspberry pi GPIO pin PWM feature and a piezoelectric actuator. The pulses generated by PWM will drive a piezoelectric actuator disk from Thor Labs using DC pulses (link: https://www.thorlabs.com/drawings/e156ef3a59a932ba-124DF929-CB86-F6E9-8CA97377261D0DE2/PA25LEW-SpecSheet.pdf). The problem I face is that the raspberrypi GPIO pins only generate pulses around 3V, but I may need a pulse that is 20V to 150V  @ up to 1 amp in order to drive the piezoelectric actuator. From my research, I believe I will need to link the GPIO output to a transistor that is capable of handling the load from a power source.  I need suggestions on designs for such a high voltage circuit that wont blow up my raspberry pi or light my house on fire.  The most useful circuit would be one that is hooked up to a variable resistor so I could modulate the voltage (would be dope if I could control that with the raspberry pi). Power supply recommendations would also be useful. Ideally I would be able to use the wall outlet as a power source.

The scope of this project is to replicate the results of these papers:
“Development of Micro Particles Separation Device with Piezo-Ceramic Vibrator” Katsutoshi Ooe, Toshio Fukuda

Transport and Concentration of Blood in Capillary Tube using Flexural Acoustic Wavw” Eun-Sun Kim, In-Kag Hwang

“Long –range Particle Manipulation in a Micro-Capillary tube using a flexural acoustic wave” Eun-Sun Kim, In-Kag Hwang

I intend to generate a single antinode in the center of the capillary tube to concentrate the RBC’s and give me a clear view of the blood plasma that I can take a picture of using a raspberry pi camera with low focal length lens.

Any help is much appreciated!


texts: Can features like ADC and PWM on a pin be considered as functions/configurations of a GPIO?

texts:
this is more or less a question about wording. I am designing an API and need to figure out whether or not the namespace name used is correct or needs to be refactored.

The namespace is called GPIO and inside this namespace are modules to configure a pin. That means, there're routines for configuring a PWM and an ADC on pins in this namespace. Also things like using the pin for I2C or SPI are grouped.

As I am only a hobbyist when it comes to electrical engineering, I am worried that the name of the namespace is confusing, misleading, or plainly wrong - because I gathered those routines/modules under the name of GPIO.

I have always thought that GPIO just means that a pin has possibly many features that can be configured. But when you lookup wikipedia or almost all other sources on the web, then a GPIO seems to be limited to only digital io capabilities and maybe configure a pull up or pull down resistor.

So, what exactly does the term GPIO mean? Is it really limited to digital IO?

Is it correct to say: I configure this GPIO as a PWM. I configure that GPIO as a timer.

Or is it wrong?


texts: Is Modular Entropy Multiplication really a new form of entropy?

texts:
I have come across Modular Entropy Multiplication (MEM) on GitHub. It's used as an entropy source for a hardware true random number generator called REDOUBLER. I've never seen such a circuit. Ye olde avalanche diodes are common enough, but this seems new...

I've reduced this circuit to a simpler layout than seen in other parts of the Interweb:-

As previously, it works by alternately clocking the analogue switch inputs SW1EN and SW2EN, and digitised entropy appears at the comparator outputs, COMP1 and COMP2. For information, it's two units that (I think) can operate independently if you just close the feedback loop around one set of sample and hold components.

The designer advertises about 7.9 bits/byte of entropy from the circuit, without any further whitening. That's a purity of 98.8%, which seems like very good stuff.

A. Is this really a new form of entropy within circuits, as it's a very uncommon technique?

B. Is there any reason to suspect that COMP1 output would be highly correlated to COMP2 output?


texts:
I recently got a Milwaukee compact floodlight, which is a powerful LED hand light.

The light from the device appears constant, but if a scene illuminated by the light is viewed with a scanning imager, it can be seen that the light is actually flickering too fast for the eye to see. Why would this be?


texts: Nationally Recognized Testing Laboratories or UL Certification necessary for USB device

texts:
I'd like to import a USB device similar to a mouse to the USA and Canada, does it need to be certified by Nationally Recognized Testing Laboratories (NRTL) or UL? Does it make a difference if the device is manufactured in Japan or in China? As well, who should be responsible for this certification if it is necessary - the distributor (me) or the manufacturer?

Thanks.


texts: Connect two pins on AD009-01T without a relay

texts:
I have an IR chip where I want to shortcut two pins (PA2 and PA0) when told so by a 3.3V Arduino.

I could do this with a sort of relay, but I want a better way.
I thought, that one of the pins needed a high input (provided by the other pin) and would pass this one when shortcutted. But this seems not to work (both pins measure 2.8V - from pin to GND).
What other way is there?
The chip needs 3V to power.
Datasheet: http://www.datasheet-pdf.com/PDF/AD009-01T-Datasheet-AnGuangElectronics-1088702


texts:
I have a microcontroller Atmega328p and some sensors like Dht22,Lm35,Soil Moisture,switching voltage regulator and a 9V battery.When my microcontroller is on sleep the total circuit consumption is about 6mA.That i want to do is not only the microcontroller to be on sleep mode but also the rest circuit such as my sensors(except Zigbee).So i used a mosfet as said at the comments below.I created a schema and as you see i connected Gate to pin14(so i will enable through microcontroller the mosfet),Drain to the 5v Switch Mode Regulator output and Source to the Gnd and to the Vcc of each sensor.Now when my device is on sleep my total consumption is about 2mA.Because i don't have someone to verify my schema and i am a newbie i want to check if my schema its ok and so my measurements.Thanks in advance!

ps. Gate Threshold Voltage is about 2-4V.So i have to put a resistor from Atmega pin14 to Gate?


texts: Step response to feedback loop with disturbance

texts:
When using step response to a feedback loop with disturbance. Why do we analyze the step response of the disturbance D and the step response of the input R separately. Instead of considering them together like with $$Y = \frac{GR}{1+HG} + \frac{GD}{1+HG}$$ given that \$Y\$ is the output.

I'm assuming we can't take the step response with both together in the function as we want the transfer function to be in terms of \$\cfrac{Y}{R}\$ or \$\cfrac{Y}{D}\$, but I just wanted to confirm that this was the case.


texts: Is there a something else I could use in this circuit instead of inductor?

texts:
I'm making the analog interface for MCP3909 chip ,

I'm having a problem in finding any inductor where I live ..

I've two question :-

Is there a substitute of this inductors ?

What's the reason of them ..!

here's the link for the reference design manual if the image isn't clear.


texts: Driving low-voltage H-bridge directly from MCU

texts:
I need to drive a small (3.6V, <1A) brushed motor bidirectionally with a PIC MCU. My available space is extremely limited, so I'd like to use a single 3.6V power supply for both the motor and PIC, and a minimum of drive circuitry.

I haven't found a dedicated motor driver IC that operates at this low voltage, so a discrete H-bridge seems the most suitable drive arrangement. I've identified the NXP PMV30UN and PMV32UP as suitable (N-type and P-type) drive MOSFETS (line card here).

Since both PIC and motor use the same power supply, is it possible to dispense with all the usual driving circuitry for an H-bridge, and connect the transistors near-directly to the MCU pins as follows? Are there any pitfalls with doing this that I should be aware of?

(The inductor symbol is the motor and RB0 and RB1 are the PIC pins (CMOS outputs driven by the same 3.6v supply)).


texts: What is the bandwidth of an antenna ? and what happens when a narrow bandwidth is used?

texts:
I'm trying to understand the bandwidth of an antenna in order to choose the right one for my next project which involves a Nordic 2.4GHz radio transceiver (NRF24 series) that operates from 2400MHz to 2525MHz.

According to this

  The bandwidth of an antenna is the range of frequencies over which it
  operates

I assumed this meant the higher frequency - lower frequency = the bandwidth, however, the datasheet of the 2.4GHz chip antenna used frequently with this chip, says it has a bandwidth of 180MHz, but the operating frequency range is 2400Mhz to 2488Mhz! if my assumption is correct, shouldn't it be 2580MHz (2400+180) ?

Also, if the higher frequency is 2488Mhz does this mean the antenna wouldn't radiate optimally if the radio is set to a channel over 2488Mhz or does it mean that it wouldn't radiate at all?


texts: Filter gyroscope's error from linear acceleration?

texts: I need to use 3-axis angular velocity data for my application, but the gyroscope outputs angular velocity when under linear acceleration (not rotating). Is there a way to filter this error?


texts:
In my FPGA designs I often deal with components which perform some kind of task/calculations which takes multiple clock cycles (non-pipelined). These components have an input port iStart which tells the component to start processing and similarly an output oDone which signals that the component is finished. This oDone output is then often connected to one or multiple iStart inputs of following components.

I'm often struggling with how I should design the trigger behavior of this signal, i.e., should it be edge triggered (rising edge triggers processing, signal usually high for multiple cycles) or level triggered (high level triggers processing, signal must be high for single clock cycle only). Sometimes these styles are mixed throughout the design (components written by different people) which leads to incompatibilities/bugs.

I used to write my components edge triggered because it allows combining multiple outputs using logical AND (if the outputs go low again at the correct time). Now I think the level triggered approach is probably better because the time point when the signal goes low again is clearly defined. For best compatibility it’s probably best if the inputs continue to use an edge detection, but the output is only high for a single clock cycle. What are your thoughts and recommendations on these styles?


texts: What is this SOT-89 component marked 43B H42?

texts:
Can anyone help me identify the SOT-89 component in the picture below? It is marked \$\text{43B H42}\$. I have searched to find anything resembling a match, and I found that it could be both a programmable shunt regulator and a NPN power transistor.

Here following a sketch of the circuit surrounding the component of interest.


texts: High voltage (500V) measurement by scaling down voltage

texts: We are looking to develop a precharge circuit in which we require to measure voltage  for which we are scaling 0-500V to 0-5/10V. In this paricular component we get an output which can be given to an ADC. There was a particular component which I found V500-ISO which scaled voltage from 0-500V to 0-5V but the issue with the component was it wasn"t available and was very expensive. So I looked for similar components one of them being ISO224 by texas instruments. In a particular application the output of ISO224 was fed into a precision amplifier. So the couple of questions which rose were is the voltage the same as input voltage ie 0-12V which is the voltage across the R2 resistor in the above diagram or does it correspond to the voltage on the output side which can be -0.3 to 6.8V and the other question is as all the parameters are given for AC voltage can this component be used for DC application. The details regarding all the specifications are listed in the pitcures and datasheets attached below.


texts: Transfer Function Magnitude, how to deal with 'j'?

texts:
I have the simple transfer function of an RC filter:

\$ H(s) = \frac{sRC}{1 + sRC} \$

In order to find the magnitude, square the previous equation and take the square root:

\$ (H(s))^2 = \frac{(sRC)^2}{(sRC + 1)^2} ; s = j\omega \$

\$ (H(s))^2 = \frac{(j\omega R C)^2}{(j\omega R C + 1)^2}  \qquad(1) \$

This is where I get stuck. I know that the correct magnitude should be of the form:

\$ |H(s)| = \sqrt{\frac{(\omega R C)^2}{(\omega R C)^2 + 1}} \qquad (2) \$

However, when I actually try to calculate this out on paper I don't know how to deal with the \$j\$. I don't understand how to get from equation I get from equation (1) to equation (2). The \$-1\$ from \$j^2\$ causes the form to look like the following:

\$ (H(s))^2 = \frac{-top}{1 - bottom} \$

If I were to take the square root of this I do not get equation (2).

What am I doing wrong?


texts: BJT Differential amplifier design and issues with gain and DC operating point

texts:
I am working my way through the Art of Electronics and I have today studied the differential amplifier. I aam having issues with Exercise 2.18: Design a differential amplifier to run from ±5V supply rails, with Gdiff = 25 and Rout = 10k. As usual, put the collector’s quiescent point at half of VCC.
I have already seen this this and this questions, which were quite useful but I still have some issues.
This is my design process:

\$R_{OUT}\$ = 10kΩ was given. Given that the collector quiescent point needs to be halfway between supplies (i.e. 0V), that means that the quiescent currenc across \$R_C\$ is 500μA
Given that $$G_{DIFF} = \frac{R_C}{2(R_E+R_C)} = 25$$ I calculated \$R_E\$ to be 250Ω
at 500μA quiescent current \$R_1\$ will see ≈ 1mA of current. To keep the quiescent \$R_C\$ voltage at 0V, I can only use a resistance \$R_1\$ of about 4.2kΩ. (\$R_E = 250Ω,  R_e = 50Ω and V_{BE} = 0.65V)\$

I simulated the circuit and it works fine. However, these are my questions:

The circuit only takes a very small input signal: at 0.02V amplitude the circuit already starts clipping. Why is that? What's the benefit of having the quiescent \$V_c\$ set midway between +/-5V, if I can't seem to be able to get an output amplitude greater than about 300mV, which leaves me with about 4.7V before reaching the supply rails?
As the common mode rejection would greatly increase with a larger resistance \$R_1\$, I could increase \$R_1\$ at the expenses of the amount of quiescent current and \$V_C\$ being centered. Would there be any drawbacks if I did that?

EDIT: The second image shows clipping with an input signal of 0.05V amplitude


texts: STMicroelectronics ST-LINK/V2-1 USB driver for macos?

texts:
I am trying to connect to my MacBook Pro the eval board: STEVAL STLCX01V1 from STMicroelectronics so I can try programming the SensorTile.

I am using OpenSTM (System Workbench).


texts: What charge controller would be required to charge a 12v battery with 40w solar panel?

texts:
I am looking to setup a 40w (or similar) solar panel on my SUV to charge a 12v deep cycle (AGM) battery for use when we're camping and that sort of situation. I am unsure as to what sort of charge controller and what amperage charge controller I am going to need for such a setup.

Could anyone please suggest what sort of charge controller would be recommended for this situation and why?


texts: Component identification, Trascend SSD340

texts: i have a broken SSD, one component burned up because of the power source of the computer and I can't identify it in order to get a new one and fix the SSD, the component is U23 in the picture. The three left pins are connected to 5V, the middle one of the right is COM, the top one is, maybe, not connected. I think it's a voltage regulator, but im not sure.


texts: Purpose of capacitors connected to both inputs of Op-Amp

texts:
What is the purpose of the capacitors in the following circuit? Using Ohm's law :

V+ = I * RTD
V- = I * R3

and also :

Vout = G * (V+ - V-) =>
Vout = G*I(RTD - R3)

The circuit is used to measure temperature,because of RTD which is a resistor that changes with temperature ( for this example it is RTD=1kΩ(1+aθ), α=5*10^-3 /C ). But i can't understand what is the purpose of the capacitors.
Are they used to block some unwanted frequencies?
And also what should be their value (approximately) if i have : I=0,1mΑ and G = 20? Are the capacitors related to the current I so their value should be mF ?


texts: Can a Variable Frequency Drive convert standard wall outlet (120V/15A/single phase) to ~220V 3 phase?

texts:
In my workshop I have a device that requires 220V 3 phase power, with a requirement of up to 1.5kVA. In North America, my wall outlet provides ~120V/15A single phases.

(EDIT - my device can take +/- 10% voltage, so anywhere from 220V to 240V 3 phase is fine.)

Doing some research, I found devices like these, called 'Variable Frequency Drives' that seem to take this type of single phase input and give the 3 phase output desired:

https://www.mcmaster.com/variable-frequency-drives

I am a noob at electronics, and I just want to confirm if I could buy one of these VFDs to solve my problem as described. I guess I would get the 2 HP version to match approximately 1.5kVA.

Thank you for any help, and open to other suggestions if this won't work.


texts: Should the primary winding of a transformer have more or less resistance to increase efficiency?

texts: I'm a bit unclear about how to think of the energy transfer in a transformer and how it would be optimized.  On the one hand, if the primary winding of a transformer is more resistive than the rest of the equivalent circuit (the power source's internal resistance and any connecting wires), most of the voltage drop would be across the transformer, but on the other hand, if the resistance of the primary winding was lower than the connection to the transformer, the I^2*R losses of the primary winding would be lower.  Basically my question is, assuming the entire primary side of a transformer has some given and constant resistance, would the transformer be more efficient if the primary winding had the highest possible portion of the resistance or the lowest portion of the resistance?


texts: Why requiring input resistors in series before digital-to-analog convertor (DAC)?

texts:
Im using AD9742 (Analog Device) for building a high speed digital-to-analog convertor (DAC). I will use FPGA digital I/O ports as inputs to the DAC. As I can found in the data sheet, the example layout could be found and shown in the figure below.

I can understand the R1-R9 are the pull-down resistors to make the inputs at GND level in case there are no inputs (floating).
I can't figure out what are the purposes for using RP3 and RP4 (22-ohm) in series between DB0X-DB13X to DB0-DB13 before DAC inputs.

I have searched other kinds of DAC data sheet (ex. TI DAC902, DEM-DAC90xU/E) and they all have similar design. Does anyone know why we need the RP3 and RP4?

Thanks in advance.

Best.


texts:
I design a board and I need around 5-8 chips connected on I2C bus. What's the main routing considerations on routing topology for multiple devices?
I was thinking that daisy chain topology would be better instead of star routing or any other topology.


texts:
I’m trying to build a simple robot using 4 DC motors with 2 LM298's controlled by node mcu and powered by LiPo 3s battery.

Since powering the node mcu directly to the 3s LiPo(11. Iv) would be overwhelming for it, I was thinking of powering it from the 5 V rail of one of the LM298 (it has a built in 7805). Will it be okay to do so or should I use an external 7805 circuit or to go with a dc-dc buck converter. I’m not from electronics background so not very sure which way to go with.


texts:
I've been trying to make an extremely simple AM receiver (without even a tuner), however, it doesn't seem to be working.

As shown in my schematic, what I did was connect the antenna wire to the base of a BC547 transistor. The collector of that is connected to a 9V battery and the emitter is connected to the base of another BC547.

This BC547's collector is connected to the same 9V battery and the emitter is connected to a germanium diode (so that only positive voltage radio signals are received), and this diode is connected to a piezo buzzer, which is then connected to ground.

So basically, I'm using the transistors to amplify the antenna's signal so that the piezo buzzer can make noises as it receives AM radio signals.

When I connect the power, I hear a chirp initially, but nothing else. Even if it's extremely low power, I should still hear some small chirps/noises right? What am I doing wrong? Thanks.


texts: When finding the s-domain transfer function of an op-amp, is the following possible?

texts:
I'm trying to find the transfer function of a Sallen key filter in the s-domain and thought that cutting out the op-amp from the circuit by using the ideal op-amp laws was a smart move (see image below). However, when I attempt this I end up with the transfer function seen below.

\$ \dfrac{V_o}{V_i}=\dfrac{s(R_2+C_2)+1}{s^2(R_1R_2C_1C_2 + R_1R_2C_2^2) +s(R_1C_1 +2R_1C_2+R_2C_1 +R_2C_2) + (R_1/R_2 + 1)} \$

This transfer function does not agree with what any sources on the Internet say, and I'm sure that it's because of how I've remade the circuit.

If possible, could someone please explain to me why this would not work (if that's the case) and how would be better to approach this task?


texts: fpga multiplexor - select line controlled by a soft processor

texts:
I have 5 pins coming into an FPGA (inputs). I have two different sets of 5 output pins. I want to select which set of output pins that I connect the input pins to. What kind of multiplexer is this called?

I have a soft processor running on th fpga which will call the select line to the multiplexer.

In verilog, what would this look like

module switch (inputs, outputs1, outputs2);

    input [4:0] inputs;
    output [4:0] outputs1;
    output [4:0] outputs2;

endmodule


texts: What is the advantage of differential Manchester

texts: I can see the advantage of Manchester code over NRZ: you get clock and data in one signal combined. But what does differential Manchester add to that?


texts:
I am new to electronics. I am trying to figure out voltage divider to bias a transistor in saturation mode to drive a relay coil. Here's the circuit:

The coil resistance is 270 Ω. So the collector current has to be 44 mA. With hfe = 110, Ib = 0.4 mA. So R2 = 12V / 0.4 mA = 30 kΩ. Vb has to be lower than Ve by 0.7V. Let's say 11V. So R1 = 3.3 kΩ. Am I correct so far?
Also in some tutorial it says "The amount of biasing current flowing through resistor R2 is generally set to 10 times the value of the required base current IB so that it is sufficiently high enough to have no effect on the voltage divider current or changes in Beta." What does that mean exactly?


texts:
I started another project where I need to charge a few devices (preferably simultaneously) wirelessly. They all have BQ51050B and the corresponding coil/battery.
I need to know what I should look at when deciding on what IC to choose to be compatible with the mentioned device.
On the receiver, I am running 3.7V 60mAH batteries and using this coil.
On the charger, I intend to control the chips using the I2C protocol.


texts: Buffer / Line driver ; 3 state IC Working

texts:
I am just curious to understanding the working of this - Buffer IC (Part Number - 74AHC1G126)

My questions :

I figured out that this IC does not act as a level translator which changes the voltages levels of the output based on the input. Why would I be needing this IC which only replicates the voltage at the output from the input? Is the answer something like high impedance and reduce the loading of the source?
Where do we need to use these type of ICs?
Why are there like 7 inverters in the fig. 3 logic diagram?

I have read this previous question at this site but still not able to get clarity

Please also help to understand the working of the circuit below (which is similar to my question) :


texts: What are the fixed values in transformer?

texts:
I am trying to understand how impedence matching works, but I realized I had some issues with basic transformers as well:

If the voltage and current is merely dependent to the input voltage, current and number of turn ratios, I say that the resistance of the secondary part of the transformer is not important? Then why don’t add infinite resistance(even open circuit) to get infinite power?
In a different way: what happens when there is a resistor at the secondary part of transformer? Voltage and current is only dependent on turn ratios and voltage and current values of the primary part, which are fixed. Then it can disobey ohm’s law?


texts:
In a single phase meter measurement, the power is being measured by using the instantaneous power which is p(t) = v(t) * i(t). But as we need to sample the voltage and current to get the power, hence it need to be calculated by using this formula:

So is this formula can really measured the real active power without considering the phase angle between V and I? As we all know that active power, P = VIcosθ.

So what is the difference between apparent power measurement, S=VI and active power measurement if the P = VIcosθ is not being implemented?


texts: Arduino on breadboard, voltage regulator

texts:
I'm working on an atmel on a breadboard, where I use a voltage regulator from 12VDC to 5VDC. The fact is that, I also program the chip while it's on the breadboard, do I need to put a diode in the main 5VDC line, when I program it using an external power ? Do the voltage regular may be damaged getting 5VDC on its output pin ?

Thanks !


texts: How to determine the total number of charges a portable charger can supply for a phone?

texts:
According to can a 3000mAh portable charger charge a 1500mAh battery?, it was mentioned that a 3000mAh Portable charger can only charge a 1500mAh phone's battery 1.33334 times.
So, how do we determine the total number of charges that a Portable charger can supply to a battery given the following parameters:

X mAh Portable charger with output of Y volt and Z Amp.

P mAh phone battery with input of 5 volt (almost all phone is using 5 volts due to USB Charging) and Q Amp.

The reason for asking is that according to the article, it mention that there is a 20% inefficiency (which I do not know if it is true for most portable charger), so a 3000 mAh Portable Battery charger can only charge a 2400 mAh battery.
If that is the case, the 3000 mAH Portable Battery charger can charge the 1500 mAh battery 1.6 times instead of 1.33334 times. I was thinking why it was stated 1.33334 times and not 1.6 times and I believe that there must be a way to calculate the number of times a Portable charger can charge a phone battery until it have no more electrical charges.
Added Information
Also, according to a user, it mention the following:

As posted above, with voltage conversion there is just 80% capacity of portable charger's battery pack available for your phone.
While charging, your phone needs power for stand-by, so in my experience, you'll have just 65% capacity.
And by industrial standards for batteries is +/- 20% tolerance admitted with capacity.
So, your portable charger might have just 45% of its 3000mAh available for to charge your phone.

So, can one use the magical value 45% as a gauge for portable battery charger? (Meaning that a 5000 mAh battery charger can only charge a 2250 mAh phone battery one time.)


texts: State transition graph for a table with a whole column with don't cares

texts:
I have this state transition table and I want to draw the state transition graphs

Didn't have problems until I reached the last column with the state 11 where the whole column consists of don't cares

How do I handle such don't care situations?


texts: Very precise way of measuring small distances?

texts: I am looking for a somewhat cheap way of measurin small distances ( >0.1 inch) between an object and a sensor, are there any good ways to do this? I am considering the component from a flatbed scanner, but I am not sure how I would make use of this. It would be preferred to use some kind of mechanism that uses absolute positioning, so it doesn't get thrown off, but a very accurate absolute positioning method would work too. Suggestions would be appreciated.


texts:
Sorry for the provocative subject line. I was looking at using one of those integrated ESP32 + SX1276 + SSD1306 boards (there are a few that have popped up) in a battery powered application. I would like to be able to use the Wi-Fi / Bluetooth features and the LoraWAN features,  but probably not at the same time or in the same application even.

I looked up all those part datasheets, and by my reading they should all operate down to 1.8V. Someone asked me, "could you just run it off of two AA batteries?" Let's not worry about questions of battery life for now, and treat that question as "is that a plausible thing to do without fundamentally compromising basic performance?"

Electrically, it seems plausible to wire battery power to the 3.3V header pin, bypassing the module regulators. But my gut said that radio performance might suffer from unregulated power,  and that using a 1.8V regulator between the battery and board would be a better idea, but I wasn't satisfied with my confidence in giving that answer, which is what brought me here.

So what are the pros and cons of bringing a regulator to the party here?


texts: PCB via stitching for current management

texts:
I'm designing a board that should handle a reasonably high current (30A) I would like to keep this on 2 layers (70um). For routing reason I need to apply the ground on the bottom layer (while positive is applied on top layer along with the 'load') in the bottom layer I have also shunt resistors. Is it possibile and 'safe' to handle such large current trough via stitching? There's some rule of thumb to 'size' vias in such cases (number and diameter)?.

PS I'm working in DC (up to 50V).


texts:
I want to build a small POV display, but how is the power (and if possible a communication line) transmitted to the spinning part?

I've looked at some POV project, but they usually don't explain that part much...


texts: What's the benefit of 24V over 12V in solar and charging?

texts:
What are all the benefits of 24V solar systems over 12V solar systems in regards to solar panels and battery charging?

All I've been able to find is that you can use smaller gauge wire with 24V, there's got to be more benefits than that.

Does 24V charge the batteries faster, etc?


texts:
I have been tasked with retrofitting some small fans to an old car, to help move heated air into the footwells. Being a computer-type, I immediately bought some standard computer cooling fans.

The fans are DC, and the only rating information is 8-12V.

It was my hope that a basic potential divider with knobbed potentiometer would provide a voltage-based fan control:

simulate this circuit – Schematic created using CircuitLab

I only ask because any search for "Fan Control" leads to pulse-width-modulation. Is it possible to control fan speed using this basic circuit above?


texts: Value for feedback resistor in pierce crystal oscillator configuration

texts:
This question is partially an "understanding english" question and partially and "understanding the pierce oscillator configuration" question.

Backstory

I'm currently looking at using a Freescale Kinetis series ARM microcontroller for a project of mine (specifically one of the KL2x series, reportedly compatible with the K20 series used on the Teensy3.1 board).

I was reading the datasheet about the oscillator and clock generator modules. There are many configurations that the oscillator can be put into, but the one I'm interested in is the "high frequency, high gain" mode which can be used for driving the internal PLL. I saw the following diagram:

simulate this circuit – Schematic created using CircuitLab

The datasheet says that for the mode I want (high frequency, high gain), the above connection diagram can be used (there are two possibilities: Connection 2 and Connection 3; Connection 3 uses external capacitors). I have chosen "Connection 2" because the internal capacitors that the processor offers are sufficient for the loading of my crystal (they are a capacitor ladder with 2, 4, 8, and 16pF capacitors configurable by register). However, there a note attached to the line that says I can use Connection2/Connection3 written in the following great english:

  With the low-power mode, the oscillator has the internal feedback resistor Rf. Therefore, the feedback resistor must not be
  externally with the Connection 3.

I was slightly confused by this because it doesn't say anything about Connection 2, so I read the sections on high power and low power modes:

  25.8.2.3 High-Frequency, High-Gain Mode

  In high-frequency, high-gain mode, the oscillator uses a simple inverter-style amplifier.
  The gain is set to achieve rail-to-rail oscillation amplitudes. This mode provides low pass
  frequency filtering as well as hysteresis for voltage filtering and converts the output to
  logic levels. In this mode, the internal capacitors could be used.

  25.8.2.4 High-Frequency, Low-Power Mode

  In high-frequency, low-power mode, the oscillator uses a gain control loop to minimize
  power consumption. As the oscillation amplitude increases, the amplifier current is
  reduced. This continues until a desired amplitude is achieved at steady-state. In this
  mode, the internal capacitors could be used, the internal feedback resistor is connected,
  and no external resistor should be used.
  The oscillator input buffer in this mode is differential. It provides low pass frequency
  filtering as well as hysteresis for voltage filtering and converts the output to logic levels.

Question

I interpreted the above to say that, in my mode of interest (high gain), the internal resistor is not being used (since it didn't explicitly say so). Therefore, I am under the impression that I need to provide a feedback resistor.

I've never really looked much at the pierce oscillator until now, but apparently a feedback resistor is part of that. My question is this: Assuming I need to actually provide this feedback resistor, what value should it be (or where can I find this out? The MCU datasheets are entirely silent other than saying that "you need one")? I know it's used for biasing the inverter (which in my case is inside the MCU), but that's about it.


texts: Op Amp adds spectral components to amplified output signal

texts:
I'm using this simple circuit to amplify a small signal:

simulate this circuit – Schematic created using CircuitLab

Input voltage is defined by: Vin = 1.5V + 5mV*sin(wt) with w = 5 kHz / (2*Pi).

The op-amp I use is the MCP6142 (application requires very low current consumption). I use the second op-amp only to probe the output signal from first op-amp (as scope impedance  - 1 MOhm - is much higher than the resistances I use).

The problem I have is that some extra spectral components are added to the output signal:

Here is a capture of the input and output signals over time:

We can see that the input signal -  blue - is "pure" as it is generated by the waveform generator of the scope. However the output signal - yellow -, though it is correctly amplified, has some extra spectral components, whose frequencies are multiples of the input frequency. Do you have any idea why this happens?


texts: Vintage Pocket Radio Transistor Replacement is Oscillating

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I have an old pocket radio which uses silicon NPN transistors for the mixer and IF stages. I replaced 2 of the IF transistors and the unit functions, but the new transistors are faster than the old vintage parts. I’d like to hear any recommendations for reducing these spurious signals in the IF stages, which sound like squealing when tuning the radio. Should I build shields for the stages?
EDIT: Radio is similar to a Philips 90 RL 020, twin band LW/MW. 1st IF amp, 2nd IF amp, and audio preamplifier (Q2, Q3, and Q4) were all replaced with low noise ZTX690B transistors ordered through Farnell. Small signal hFE was measured to be around 600 for the new parts. Staggering the IF yields good performance on MW sacrificing adjacent station rejection. Unit functions exceptionally well on LW with the IFs peaked so it’s close to working. Experimenting with shielding seemed to reduce oscillation but not enough. All electrolytic capacitors have been replaced. The purpose of this project is to learn how to improve RF circuit stability.
https://elektrotanya.com/philips_90rl020_sch.pdf/download.html
https://www.diodes.com/part/view/ZTX690B
See also: http://www.dicks-website.eu/low_noise_amp_part3/part3.html


texts:
It has been always said that having gold plating on a PCB has lots of advantages. Not only does it give a good clean low resistance contact, but the perfect flat surface. However based on the galvanic series table, gold and tin\lead (or even copper) placed farther apart from each other that leads to corrosion and noise voltage.

if it is true what would be better to take into account first, resistivity or corrosion (also noise voltage)?


texts: What is meant by 'On-chip 2-cycle Multiplier' for AVR microcontroller?

texts:
While checking the datasheet of ATMEGA 32 I have found a feature called 'On-chip 2-cycle Multiplier'.

Can anyone explain to me what's that and what's the advantage of it?


texts: I'm wondering if I've blown my lcd by accident. It's supposed to be a 20 * 4 rows lcd however only row 2 and row 4 seem to light up. Should they not all light up


texts: How to design a CMC (Common Mode Choke) footprint to allow no-pop solution

texts:
How would you design in CMC's with a 0504 (1210 metric) 4-lead package to allow for  a no populate (do not pop, DNP,DNI) solution? I am thinking 0402 0ohm (zero ohm) resistor but cannot picture the PCB layout?

Specifically, this is for USB data lines and the CMC's may be used to reduce radiated EMI.

Edit 7/9/19
Would this footprint setup work okay? 4-pad CMC with two 0402 resistors in series.


texts:
I have a DC- adapter which gives me the output of 12V and 3.3A, I want to connect it to a device which requires 12V and a few hundred milli amps, would this damage the device? or any device would automatically draw the current it needs and not anymore ?

If it matters the device is a display driver. Datasheet.

Please, Help me understand the basics of current draw.


texts:
I'm doing a prototype on a perfboard and I need to use a square wave of 1 MHz at least. The square wave is for a clock pulse and I generate it with a AC generator.

I want to know if at that frequency  I will have some electromagnetics problems and if there is a way to minimize them.

I add the part of the circuit where I need to emit the 1 MHz pulse. The part where it goes to the FF, it is a counter.


texts: Appropriate models to model magnetic components in LTspice and what are the pros and cons?

texts:
I'm looking for appropriate models to model magnetic components, mostly transformers and perhaps for chokes as well, for use in LTspice.

I've heard briefly of some models, like Jiles-Atherton-model (JA) and John-Chan-model. At LTwiki non of these models feels very appealing. Maybe the JA-model can be used in a late simulation of a design, but before that the sim-time do not feel any appealing at all, so i'm trying to find something more appropriate.

In "Switch-mode power supplies" by Basso, there is a model presented that I think is pretty suitable, that can model saturation, hysterical losses and "frequency losses" and also plot Flux and the magnetizing force, however it doesn't work to just take the subckt to LTspice, the syntax isn't the same.

I've also found some other literature that reminds of the one in "switch-mode power supplies", perhaps some of them are exactly the same just described a bit differently. 1,2 and some in 3 and 4 look very much the same. However non seem to be direct "copy paste" compatible with LTspice.

1http://www.intusoft.com/articles/satcore.pdf

2http://www.ti.com/lit/ml/slup109/slup109.pdf

3Transfromer modeling,beigbag

4SPICE Modeling of
Magnetic Components  by Sanders

5Non-Linear Saturable Kool Mu Core Model, aeng

6Spice3 Compatible core model, at aeng

Before deciding which model or models to implements in LTspice, I need to know what the pros and cons of the models are? and are there any more relevant ones that I've missed?

Best regards