texts:
I'm working on a load switch circuit that drives a capacitive load of 1000 uF and a GaN transistor in parallel. The schematic of the circuit is attached. The input voltage is 50 V and the PMOS being used is IRF5210. The simulations show promising results(also catering the inrush currrent issue), but on the hardware, when the GaN is biased to -2.9 V and the pulse is applied to the NPN transistor, the circuit turns on but draws the maximum current from the supply. Hence, the PMOS gets burned.
The inrush current is limited to 0.4 A max and the full load current can go up to 7 A.

Any suggestions will be welcomed. Thankyou]1

(original)

I am trying to work on the overvoltage and undervoltage protection circuitry and if the supply voltage is within the 45 to 55 VDC range, then the voltage may be transferred onwards. For that purpose, I designed this load switch circuitry. The NPN transistor is MJE13003 that switches ON/OFF depending upon the comparator's output signal (Here assume simply there is a 5 V ON signal coming, so the NPN biases the PMOS (IRF5210) and hence turns it ON). For inrush current limitation, I used this 20 uF cap to limit it according to the application note. The GaN at the output is QPD1881L.


texts: Serial port reading: data format unclear

texts:
I am trying to read serial data from this OEM barcode scanner module:
https://www.barcodescannermodule.com/sale-11330019-lv3085-mini-barcode-scanner-module-usb-ttl232-interface-for-pdas-tablets.html

and I am confused by the data formatting of the results: 8 bytes of data that fits my expectations, then 8 bytes of zeroes.

I am working under Linux. The device is connected via USB, and it appears as a HID Keyboard in the devices list: /dev/hidraw0.

According to the (very meager) documentation available for the device: "The default settings of the engine are 9600bps, no parity check, 8 data bits, 1 stop bit, and no flow control. The engine uses 8-bit registers.". This is also how I have tried to configure my read from the serial port.

Code used to read serially from the hidraw0 device:

#include <stdio.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <errno.h>

int main() {
  int fusb = open("/dev/hidraw0", O_RDWR | O_NOCTTY | O_NDELAY);
  if (fusb < 0) {
    printf("\n Error in opening USB device");
  } else {
    printf("\n USB device opened successfully");

    /**
     * Set the data transmission options
     */
    struct termios options;
    // Get the current options for the port
    tcgetattr(fusb, &options);
    // Set R/W at 9600 baud
    cfsetispeed(&options, B9600);
    cfsetospeed(&options, B9600);
    // Set "no parity"
    options.c_cflag &= ~PARENB;
    // Set stop bits = 1, so we clear the CSTOPB bit.
    options.c_cflag &= ~CSTOPB;
    // Set data bits = 8
    options.c_cflag &= ~CSIZE;
    options.c_cflag |=  CS8;
    // Disable software flow control
    options.c_iflag &= ~(IXON | IXOFF | IXANY);
    // Set the modified options
    tcsetattr(fusb, TCSANOW, &options);

    // Start reading and printing out what we read
    fcntl(fusb, F_SETFL, 0);
    int step = 0;
    do {
      char read_buffer[64];
      int bytes_read = read(fusb, &read_buffer, sizeof(read_buffer) - 1);
      printf("\nBytes read in step %d: %d", step, bytes_read);
      for (int i = 0; i < bytes_read; i++) {
        printf("\nByte %d: %02X", i, read_buffer[i]);
      }
      step++;
    } while (1);
}

}

And this is what is printed out:

Bytes read in step 0: 8
Byte 0: 00
Byte 1: 00
Byte 2: 27
Byte 3: 00
Byte 4: 00
Byte 5: 00
Byte 6: 00
Byte 7: 00
Bytes read in step 1: 8
Byte 0: 00
Byte 1: 00
Byte 2: 00
Byte 3: 00
Byte 4: 00
Byte 5: 00
Byte 6: 00
Byte 7: 00
Bytes read in step 2: 8
Byte 0: 00
Byte 1: 00
Byte 2: 21
Byte 3: 00
Byte 4: 00
Byte 5: 00
Byte 6: 00
Byte 7: 00
Bytes read in step 3: 8
Byte 0: 00
Byte 1: 00
Byte 2: 00
Byte 3: 00
Byte 4: 00
Byte 5: 00
Byte 6: 00
Byte 7: 00
...

The hex values printed in the even reading steps match my expectations: here, I was reading a QR code that started with "04", which matches the 27h, 21h read in steps 0 and 2, using hex -> decimal and then this mapping, according to the official USB HID usage tables for keyboards (see also here):

{ 4: 'a', 5: 'b', 6: 'c', 7: 'd', 8: 'e', 9: 'f', 10: 'g', 11: 'h', 12: 'i', 13: 'j', 14: 'k', 15: 'l', 16: 'm', 17: 'n', 18: 'o', 19: 'p', 20: 'q', 21: 'r', 22: 's', 23: 't', 24: 'u', 25: 'v', 26: 'w', 27: 'x', 28: 'y', 29: 'z', 30: '1', 31: '2', 32: '3', 33: '4', 34: '5', 35: '6', 36: '7', 37: '8', 38: '9', 39: '0', 44: ' ', 45: '-', 46: '=', 47: '[', 48: ']', 49: '\\', 51: ';' , 52: '\'', 53: '~', 54: ',', 55: '.', 56: '/'  }

I cannot account for the zeroes in the steps 1 and 3, however.

As a long-term StackOverflow user I am aware that my question is a bit nebulous, but I would like to know if this is a data formatting issue or something else I have overseen.

Bonus question: why are the expected values always in byte 2 of the read value?


texts: I am using an insulated wire as an antenna, which is picking up 0.08 V of AC. I want to convert that to DC. I know I need to use a rectifier, however my configuration doesn't seem to be working. I have a diode with a forward voltage of 26 mV and reverse voltage of 30 V. I am using a multimeter to read my voltage. I have the negative side of my multimeter grounded. Any suggestions?


texts:
Suppose that you have a design that has had an error after running 14, 18, and 20 hours.  You're not exactly sure what is causing the error, but you make a change to the design that MIGHT fix it.

How long do you have to run without seeing an error until you can be 99% sure that you've fixed the problem?

Note that the system is reset and restarted after each error, so the times given are for the first error after a reset/restart.

Also, assume that undoing the change makes the error come back at the original rate.


texts:
I wanted to ask what are the cases when it's compulosory to know the transconductance (gm) of a device, whether it is BJT, JFET, MOSFET...

As far as I know, when you want fast switching with very low timing, the higher the transconductance the faster the switch will be and in this case, is good to know it.

On the other hand, when you are designing an amplifier stage, is it important to know the transconductance of the device? Because in all the cases, you would use an emitter/source resistor for stability and liniarity, which eliminates the need of knowing the gm.


texts: Can a single power supply control multiple relays?

texts:
I want to make this circuit, to convert a toggle switch to a momentary switch:

I'll be using a 5V power source & relay, rather than 12v (with a higher μF capacitor).

Is it possible to use the same power supply (USB: 5v DC) to create multiple circuits like this?


texts: How is resistance of the induction motor calculated if we know power of motor, winding pattern, and pole of a motor?

texts: How can i calculate resistance offered by induction motor when in star and delta connection and if I know winding pattern, power of a motor and number of poles?


texts: Why does the capacitor affect the speed of the motor?

texts:
I recently watched This video about an air purifier made from an old oscillating fan and at 5:20, he explains that the motor's speed has decreased over the years because the capacitor "isn't as good as it used to be". So he replaced it.

Why does a clapped-out capacitor reduce the speed of an AC motor like that? An alternative perspective on the question: Why is the capacitor there?


texts: Why does this "square wave" have what seems to be a charging action on it's leading edge?

texts:
I'm trying to produce a basic square wave output across a resistor from an ATMega328P Xplained mini. VCC is 5 V.

Setup:

Code: (Stuff with DDC/PORTB is just to control the onboard LED)

#define F_CPU 16000000
#include <avr/io.h>
#include <util/delay.h>

int main(void)
{
// Turn off global pullup disable
MCUCR &= ~(1<<PUD);

// Direct pins
PORTC = PORTC & ~(1<<PORTC1) | (1<<PORTC3);
DDRB |= (1<<DDB5);
DDRC |= (1<<DDC1) | (1<<DDC3);

while (1)
{

    PORTB ^= (1<<PORTB5);
    DDRC ^= (1<<DDC1);
    _delay_us(500);

}
}

But when I place an oscilloscope probe on the PC1 side of the resistor, rather than a square wave I'm seeing this:

It seems strange to me that the output isn't just a square wave, I understand that resistors aren't ideal and that they have small capacitive and inductive elements to them but this seems excessive? Additionally, why is the peak voltage of the waveform only 600 mV?


texts: Trouble with phase locked loop: phase comparator is just showing the VCO output (with picture)

texts:
I am using the CD4046BC for the first time, and do not understand something that is happening. I am using the type I phase comparator, which is just a simple XOR logic gate. When I have the input as a 50% duty cycle square wave with a frequency close to the carrier frequency that I've set for the chip, I do get a lock, but it is very unstable. As in, my lock range should be from 60 kHz to 140 kHz, and yet I'll establish a lock at 100 kHz and adjusting this by hundreds of hertz will bump me out of lock. I took a look at what was going on with the phase comparator, and the result does not make sense to me. I took the following picture when the signal was tentatively locked: the top is the input, the middle is the output of the VCO, and the bottom is supposedly the phase comparator...

Adjusting the frequency of the input to view the changes in the VCO output, it was clear to me that the phase comparator output was exactly the output of the VCO, albeit a different amplitude. Why in the world would this be the case? Has this ever happened to someone before? If not, do you know what is going on? I am very confused as to why this would happen. Many thanks in advance for any assistance.

Edit: Here is a schematic of the circuit that I am testing. It is simply a block diagram of the inside of the CD4046BC with my specific component values in red. Note that INHIBIT is grounded to enable the VCO, and the reference voltage Vss is also at ground. Here is a brief explanation of the components: R1, R2, and C1 establish the frequency range and its offset to be (100 +/- 40) kHz, R3 and C2 are components of a low-pass filter with a 5 kHz cutoff, and Rs is specified to be 10 k in the datasheet if this pin is used (can ignore it for this post).

In reference to my oscilloscope image, the top wave is at pin 14 (from a function generator), the middle is at pin 4, and the bottom is at pin 2.


texts:
I have been working on a design based on solar power. While browsing through some circuits on the Internet I came across these designs below

In these designs, why was a diode added between the solar panel and the voltage regulator chip? I understand that a diode will be usually used along with a Solar panel to prevent the reverse flow of current which in  turn might damage the panel under dark conditions.

But I really don't understand its use in the above designs. Is there a possibility of reverse current flow from these regulator chips to the panel? I can only imagine that happening when the panel is connected directly to a battery.


texts: Is there such a thing as an RF CMOS pdk?

texts:
In this PhD thesis (page 10) about some dust particle detector that was based on an RF chip , we can read

" Since this thesis was the first attempt in this way, there were not
any primary experiences, or guide lines or even predefined parameters
and characteristics for the RF front end. Due to cost considerations
and some other limitations, global purpose CMOS process was used,
instead of RF CMOS process and this was source of many
challenges in our work. Actually we were obliged to develop all of the
required modeling and design procedure for passive elements, as well
as the proper parasitic models for active devices. "

This got me wondering about the PDKs the foundries provide. Are the PDKs used for digital/VLSI/ASIC design different from those used for RF design? What are the main differences, if any? For example, I have the tsmc 0.13u pdk (it's called tsmc13rf), will it be suitable for designing RFICs? As a side note, I can see spiral inductors and MIM caps among the components listed in the library of this pdk.
Many thanks.


texts: Why are some generic door alarm magnetic switches built using Normally Open reed switches instead of NC type?

texts:
Some generic, low-cost "door alarm" magnetic switch components are made of using "Normally Open (N/O)" type reed switches, ie, when the magnet is in proximity, the current stops flowing.

If I were building such a system, I think I would choose a Normally Closed type so that the current would flow when the magnet is pulled away, eg, when the door is open, and I could sense it and ring the alarm.

My question:

Why are generic, low-cost magnetic switch components go for Normally Open reed switches instead of the opposite?


texts: Given a gated SR latch, How do I make it a set dominant gated SR latch?

texts:
Another weirdly worded question in my digital logic book. It doesn't specifically define set-dominant or reset-dominant - nor does it show how to use these in practice with drawing circuit diagrams. I've read and reread the chapters and it doesn't specify how to do this..

I did some research online and it appears that NOR SR latches are reset dominant and NAND SR latches are set dominant?

I know that unpredictable behavior happens if S and R inputs are both equal to 1 when the clock changes to a 0. Given a circuit, I'm supposed to create a set dominant gated SR latch in which the conditions S=R=1 causes the latch to be set to 1.

I've included the circuit we're given to start with and my attempt at making it set dominant (don't judge me lol).

Given Circuit:

Characteristic Table: \begin{array}{|c|c|c||c|} clk & S & R & Q(t+1) \\
\hline
0 & X & X & Q(t) \\
1 & 0 & 0 & Q(t) \\
1 & 0 & 1 & 0    \\
1 & 1 & 0 & 1    \\
1 & 1 & 1 & X    \\
\end{array}

My first attempt:


texts: Solar MPPT charger causing regular voltage spikes

texts:
I have a van which has two 12V solar panels on the roof.  The charger is connected to the batteries and seems to constantly be outputting about 13v.  I've had it installed for a couple of days and I've noticed that my USB cigarette lighter now no longer works and the voltage throughout the vehicle is reading as 13V (I only have a low-res digital voltmeter).  And the LED on the cigarette lighter charger is pulsing suggesting it's receiving a fluctuating voltage, roughly in time with the charge LED on the MPPT charger.

The charge LED on the MPPT charger flashes around 3 times a second, but irregularly.  I think it is putting charge into the battery at 13.5V when the LED is illuminated.  This is causing the voltage throughout the van to vary between 12V and 13.5V multiple times each second.

Does this seem plausible?

Most importantly, how can I regulate this voltage to a steady 12V throughout the van?  I am drawing up to 20A from the battery to run lights, an amplifier, a fridge etc.

Am I doing the (Lead Acid) batteries any harm by having this constant charging happening?


texts: Is there a range for an isolation transformer's common mode rejection frequency?

texts:
Below shows use of an isolation transformer in a system:

(taken from this site)

At C(right after the isolation transformer) the waveform is cleaner comparing to A and B.

What frequency of interference can an isolation transformer attenuate in general? I there a lower limit for the frequencies it can suppress. I know that EMI filters can choke down to around 10 kHz not less than that in general.

But how about an typical 1:1 isolation transformer? Is there a freq. range it can suppress for common mode noise?

I'm also wondering whether transformers can be used to cancel harmonics of mains frequency like 3rd harmonic.


texts: the best way to calculate rms voltage from 10Hz to 20KHz

texts:
We need to calculate the RMS voltage of a signal that can work from 10Hz to 20 KHz with a duty of 5% to 95%. I decided to use a dsPic33CK256EP202 with the ADC sampling at 500Ksps at 12 bits of resolution. But I have a problem with little ram memory to store the points of an entire cycle (when the signal frequency is less than 250Hz). I tried to dynamically calculate the rms sum during the interruption of each sample read, with the purpose of not having to save the samples in ram. However, in this way, the sampling speed drops to 60-70 Ksps. How would you go about computing this signal?
At the moment I am trying to use flash memory to make up for the lack of ram, however I am thinking that the flash recording time will be longer than the time interval between samples.
If someone has another reading topology, it is welcome.


texts: Security/safety circuits in removable cell phone batteries?

texts:
It seems like the aftermarket phone battery is so flooded with terrible counterfeits it can't be too hard to trick a phone into thinking a battery is genuine. I'd really like to learn how to use an 18650 in my old phone instead of buying a new crappy fake off of Amazon every few months but it won't power up without the extra 2 pins connected to the extra circuit.

I hate the idea of not being able to use something just because the manufacturer stopped making quality batteries for it. Right to repair etc etc

Edit: Okay maybe I need to clarify more. I keep buying batteries for a phone I have on Amazon. Every single one won't hold a charge after around 3 months. These are terrible quality, and this is not a phone I keep in my pocket and 18650 cells are so ubiquitous it would be very practical to have the option of using an 18650 cell in any old phone in the future, but I need to learn how to get the phone to boot up with one. I don't want to be forced to use phone specific batteries so I'm trying to get some information on how to accomplish this goal.


texts:
I've searched this forum a bit in regards to the L3G4200D gyroscope, and haven't seen this problem mentioned, but I have seen others talk about it on other forums. I am seeing a strange large value in my output when the gyroscope is stationary. Unfortunately no one seems to has been able to answer why this is, so thought I'd ask around

So, I am collecting data from the gyro using i2c at 400kHz (fast mode), collecting the gyroscope data using multibyte read (six bytes at a time). Sampling at 100Hz (tried the top 800Hz too), also tried with the filtering on and off at different values. I'm not using the interrupt pin, but I am using the 'block data update' attribute in the GYRCTRLREG4, so that the data isn't outputted until both LSB and MSB are read. Full 2000dps and not done anything with the FIFO. I can post my exact register values if it helps, but figure most of you wont have the datasheet to hand.

The image below shows my problem. The data being output is good, calculated correctly (to my knowledge) and general noise is very acceptable. But then I noticed these annoying 'blips' appearing randomly when the device is stationary. If I leave it still for a couple of seconds I'll get one of these spikes, always equaling around 250-255 (thus ~18 when converted, using '(output * 70) / 1000'). The spikes, as I say, are random, can appear in any plane (in the image below you can see the first spike in the X plane, second in the Y), always around the same value, and one, two, or all three can happen at the same time. The large value is only for a single sample, then goes back to normal.

I saw in another thread somewhere that I should be using the block data wait function in GYRCTRLREG4, as I mentioned before, but no change. I've narrowed the problem down to being when the MSB is zero or higher, i.e. a positive number, then when the MSB and LSB are combined I'm getting these large numbers. For example, I grab the two bytes necessary for the X plane, I get a -6 in the LSB, and a 0 in the MSB, combining them gives me 250, then converting gives (250 * 70) / 1000 = 17.5 dps (i.e. too large for stationary/incorrect). In the same sample, the two bytes for the Y plane are -3 LSB and -1 MSN, combining them gives -3, and converting gives -0.21 (i.e. expected/correct).

Been on this problem for days now, I'm also seeing a bit of these random spikes with my magnetometer, so I'm thinking it's me reading the device (via i2c) incorrectly?

Any suggestions or things to try are really welcome!


texts: Monitoring Battery voltage using ESP8266 thinig dev board?

texts:
I have ESP8266 thing dev board. I am trying to measure battery voltage and send it to ThingSpeak. I have two questions:
1) DO I need a voltage divider connected ?
2) I googled but couldn't exactly find any example which could help me how to code in order to get battery voltage using esp8266 thing dev board?
Any help would be appreciated. Thank You!!


texts: Using Arduino + MOSFET to automate the pressing of button

texts:
I am working on using Arduino Uno to automate the pressing of buttons. The configuration to the left is the current configuration and it works fine. However, the configuration to the right doesn't. Could someone help with this matter?

P.S. I've tried using relays and it works, but I don't want to use them because they are too big.

P36N06 Datasheet


texts: Plotting pulse width or frequency of a pulse train LTspice

texts:
Maybe I'm demanding from the tool too much but I'm wondering whether the following possible in LTspice.

I have a PWL file(time and voltage values) which can be read and plotted by LTspice. This is a pulse train with 0 to 5V amplitude but with varying frequency.

To see how the frequency or the period changes for each successive pulse, is there a way to plot or extract the frequency or the period of each pulse?


texts:
I am asking this question directly on the TI forums as well, but decided to post here in case anyone has specific experience with this.

I am attempting to prototype with a CC2650 RGZ package 48 pin QFN processor from TI. I am trying to program it using the XDS100v3 debug probe on the SmartRF06 Evaluation board. The chip I am trying to program is a standalone, not the evaluation breakout board.

My only connections are a 3.3V power supply to VDDS, VDDS2, VDDS3, and the VDD_DCDC input. The DCDC output I have connected to the VDDR 1.8V inputs. My reset pin is tied through a pullup resistor to 3.3V. All pins listed above have capacitors to ground, as recommeded in the SmartRF documentation. When I tried just using that, I got 3.3V on the power rail and 5 mA being drawn from my power supply, as expected. So for that reason I believe my power connections are correct.

To program the board, I connected the cJTAG connections from the SmartRF06. This would be Pin 1 on the JTAG connector(VDD_Sense) to Power, Pin 4(Ground) to Ground, Pin 7(TMSC) to Pin 24 on the CC2650, and Pin 9(TCK) to Pin 25 on the CC2650. These follow chapter 7 recommendations from the programming guide. I ran CCS to program the board, and recieved the error "Power Failure on target CPU".

Following this, the CC2650 started drawing the current limit from my power supply at 30 mA. This persisted after I disconnected the JTAG pins. I think, therefore, that the chip was burnt somehow by the debugger. I do not, however, have any idea of why this happened.

On the SmartRF board, I disconnected the VDDtoEM jumper, but left the other default jumpers on. I also removed the evaluation breakout board. POWER switch was set to ON and BAT/USB was set to USB.

I have a couple days before my replacement chip comes in, but if anyone has experience with TI debuggers, specifically with designing boards using the CC2650, I would appreciate some advice on how I can program my chip.

For reference, here is the development kit I was using, which has the debugger onboard: http://www.ti.com/tool/cc2650dk

Thank you for any advice or help you can provide.


texts: Node Method vs Simple KVL and KCL Equations Difference

texts:
I am just quite confused when deriving some equations for this simple circuit. Using just KCL and KVL (loops in green) to the best of my understanding, I get the first set of equations.

Firstly, are they valid?
Secondly, when using the node voltage method, I get the second set of equations with the nodes in blue writing. I would like to know if they are equivalent or which set (if any) is correct, as I am unsure and they don't seem equivalent unless I am missing something?


texts:
In a demo software from Olimex for the PIC32-MAXI-WEB the configuration words for the osc are set as follows:

/** CONFIGURATION **************************************************/

#pragma config FNOSC    = PRIPLL        // Oscillator Selection
#pragma config FPLLMUL  = MUL_20        // PLL Multiplier
#pragma config FPLLIDIV = DIV_2         // PLL Input Divider
#pragma config FPLLODIV = DIV_1         // PLL Output Divider
#pragma config FPBDIV   = DIV_1        // Peripheral Clock divisor

There are the following macros for getting the clock speeds;

#define SYS_CLOCK             (80000000ul)
#define GetSystemClock()      (SYS_CLOCK)
#define GetPeripheralClock()  (SYS_CLOCK/2)
#define GetInstructionClock() (SYS_CLOCK)

The main clock should be 8MHz / 2 * 20 / 1 = 80

Is the PeripheralClock = SYS_CLOCK/2 a bug/typo, as the FPBDIV is set to 1. I tried to look for it in the datasheet. Is there indeed a bug, or is there some kind of internal division by 2 that is always active or activated by some other condition/register. (Like how the instruction clock was FOsc/4 on some devices)


texts: What is the use of these resistors in the schematic?

texts:
I am trying to build a line-following robot with the schematics I found below. I understood that the comparator is used as the logic for the robot and there is no need for a feedback loop for the comparator in the circuit.

Thus, what is the use of R3 and R4(marked with orange arrow) in the circuit?

Disclaimer: I am a beginner and just started learning electronics. Kindly excuse any comments/questions that doesn't make sense to you. They were written/asked based on the brief knowledge that I have acquired along the way, and asking the community here is part of acquiring more of such knowledge. Thank you for your kind advice.


texts: Accessing data past 64k boundary on atmega1280

texts:
I need to be able to store and refer to constant data arrays which must be placed after the 64k boundary in the atmega1280.  How do I create the correct data structure, and then access it for the following example:

const uint16_t PROGMEM port_to_mode_PGM[] = {
    NOT_A_PORT,
    &DDRA,
    &DDRB,
    &DDRC,
    &DDRD,
    &DDRE,
    &DDRF,
    &DDRG,
    &DDRH,
    NOT_A_PORT,
    &DDRJ,
    &DDRK,
    &DDRL,
};

uint16_t getdata(uint8_t index)
{
   return port_to_mode_PGM[index];
}

Currently AVRGCC compiles it placing the data structure after 64k (The whole program is after 64k, using a linker instruction to move the .text section) but then uses the LPM instruction to access the data structure.

The LPM instruction can only access the first 64k of program memory.

It looks like the following should work

uint16_t getdata(uint8_t index)
{
   return pgm_read_word_far( port_to_mode_PGM + index);
}

But the disassembly and simulation show that the pointer port_to_mode_PGM is only a 16 bit value, despite living beyond the 64k boundary.


texts: What are the advantages of CMOS operational amplifiers vs bipolar in the same class?

texts: Is there something else than Rail-to-Rail output and possibly lower power consumption for low frequency applications? Or Rail-to-Rail is the main one?


texts: Phototransistor responsivity does not match datasheet?

texts:
I am making a basic circuit to test the responsivity of a phototransistor.

I made a basic circuit using a phototransistor connected to 5V and a 22kOhm resistor. On the other side of the phototransistor is a Red/Green LED that has equal mcd ratings for both colors.

My problem is that, even when I calibrate for I_f, the detected voltage from the red LED is much higher than the green LED -- to the order of 2.5x or higher. This result does not agree with the phototransistor datasheet, which says the difference in responsivity is not that high.

For reference: I am using the PT908-7C-F phototransistor and the SSL-LX2577IGW R/G LED. However, these results seem to be independent of phototransistor and LED, as I have been able to reproduce this result with another phototransistor/LED setup in the past.

I am at a loss as to what could cause this result. Short of obtaining a laser/light power meter from my other lab to verify my results, what could be a possible explanation? mcd ratings are not reliable? Line width? Actual responsivity curve more steep than reported on datasheet?


texts: How to tell the polarization (horizontal or vertical) of a microstrip linear array antenna just by inspection

texts:
I know that a linear array of microstrip patches can be either horizontal or vertical depending on its orientation.

Does the feed (input port of the array) determine the direction of polarization?


texts: Is a PIR sensor as easy as just a receiver? Rather than use some pre-canned device I was planning to just hook up an IR LED to my microcontroller and then read the IR sensor/receiver for a threshold voltage level. My concern is that is a naive assumption as everyone would just do that instead of buying these pre-made sensor packages.


texts: Power electronics DC DC converter question: What is the function of the capacitor and resistor connected between two series inductors?

texts:
This is a power electronics DC DC converter question:

What is the function of the capacitor and resistor  connected between two series inductors?

This is part of the schematic from a photovoltaic inverter. I coudn't understand the function of the components in the red circle. Sure they do not participate in buck or boost feature. There is no heavy filtering required on PV side (IMO.) So what is the function of these components?

Specifically, the 10uF film capacitor and 100Ohm/5W resistor connected between the inductors.


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I am new to verilog and having a bit of trouble getting along with it.

I read about asynchronous and synchronous reset and i think i got hold of it but while implementing the same with verilog i am not able to understand a line of code which i saw on this website.

In the asynchronous reset code why are we using the always @ (posedge clk or posedge reset) instead of using always @ (posedge clk ).

I mean how are the two lines of code able to differentiate which is asynchronous and which is synchronous?


texts: What component is labeled "SI" on a PCB silkscreen?

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What component is labeled SI (SI1, SI2, etc) on a PCB? By the way, what kind of capacitor is C7? (The one on the right of the "SI" component, assuming its a capacitor).

EDIT: The PCB is a combined boiler control board (Roca Victoria 20/20T) manufactured in Spain. The attached picture shows the components surrounding the spark igniter, whose transformer is the grey plastic box on the right.

The complete marking is "6W" "R600" "95" "0029". Measured with a leg detached from the PCB, it has no continuity (Tester displays "Open Loop") in both ways. "R600" suggests a 600-ohm resistor, but it's not. I tested the PCB operation with the component removed, and the spark igniter stops working, so it appears to be OK.

Thanks


texts: Why is the magnetic field perpendicular to the magnetic force?

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In the case of the electric field, we define the field as the force at each point in space exerted on a unit charge. This is intuitive, as the field will give me a good idea of how a charge will move in space under the influence of the field. But in the case of the magnetic field, what is the significance in defining the magnetic field in a way such that we must take the cross product to find the magnetic force: $$F_B = qv \times B$$
Couldn't we define it in a way similar to the electric field, such that the magnetic force points in the same direction as the field? I understand that a charged particle follows a circular pattern under the influence of a steady magnetostatic field, so it may lead to simpler equations for B this way, but is this the only reason?


texts: Moving an electolytic cap out of the way of a chip clip

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I'm trying to read flash off an old sampler and I have all the required gear to do so.  However, there is an SMD electrolytic capacitor in the way keeping me from placing a TSOP 48 clip on the flash chip.

What I'm wondering is, after removing to allow me to put down the clip, how do I keep the cap in circuit and working?  I've attached a picture of the cap and also it in the circuit diagram (C75).  I'm also curious about the symbol used for this cap, can't say I've ever seen that before.


texts: Design LNK302 with external current boost

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I want to use the LNK302, which can work as buck converter. Of course it does not operates similar to buck converters like MC34063 but I tried in many ways to boost the current on the LNK302 with a MOSFET but had no success (tried on simulations only).

Is there a way use the LNK306 output for the input signal of a boost converter?

I tried the direct feedback and the Optocoupler feedback but had no sucess.

It can be a problem with my simulations, if anyone knows a way of making it work, please share a schematic.

LNK302 Datasheet

Below is an image of my actual schematic trying to adapt what is in the datasheet with boost cricuit (probably very wrong)


texts: How do I determine the junction-to-ambient thermal resistance?

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For a project I'm working on, I was considering using an AS7805 to supply low-noise 5V power to some sensors. (due to the uncertainty that resulted in asking this question, I've since changed to a 7805 from another manufacturer, but that doesn't really matter to the question.) However, the datasheet doesn't tell me what the junction-to-ambient thermal resistance is. These sensors don't take much current, but since I'm dropping 10V in this 7805 it still does reach 0.6 watts, and I would like to know if I can get away with not using a heatsink.

Can I assume the 60 °C/W figure given in the absolute maximum ratings to be the heatsink-less thermal resistance of the device? Or is that just saying that you need to ensure your heatsink is sufficiently good that you don't exceed 60 °C/W?

Most devices I see specify both a junction-to-case and a junction-to-ambient thermal resistance. Why does this one, apparently, not? Is it just not intended to be used without a heatsink?


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How can I stop the current flowing through the LED when the second switch is open (as it is on this circuit)? A lot of people suggests that just by using MOSFETs the problem will be solved because in steady state the current is not allowed through gate (base), but instead, if I stick with BJTs there is nothing that I can do about it? Maybe placing a buffer somewhere in this circuit that tells me when it's fully on or off?

What I really want to obtain from this circuit is to light a single LED or to power some load resistance only if both switches are closed (or the batteries are plugged in for example) from the parallel batteries.


texts: Time delayed light/beeper beacon circuit

texts: I need to build a timed beacon for locating and recovering the payload from a space balloon launch.  My Cub Scout Pack is launching a balloon to space. We have other recovery devices on board (radio, GPS, phone).  We want a backup audio-visual device that will have its own power source, start after a set time (3-4 hours) and continue to beep/light for at least an hour.  I saw a plan a while ago that used a simple programmable chip but I cannot find the specs. I'm looking for something simple to build from available parts.


texts: How do CMOS switches behave when Vdd is grounded? What are the alternatives if they behave undesirably?

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Say, I have a SPST CMOS switch, does it break the connection between two terminals when the power is out (Meaning Vdd=Vcontrol=0)? Or does it ground one terminal?

If it doesn't completely break the connection, what can I use as a switch that does?

I'm switching between AC signals (line audio) and I'm converging output of two switches (only one which is ON at a time) at a common output. I need to make sure one switch is ON when power is off, so I'm using a JFET switch for that one.

This question is for the other switch. I would rather not use enhancement MOS. Since it will either require a relay-like configuration which is undesirable (I can't afford LED current) or a diode in series with MOSFET. Because otherwise it would ground the output half of the cycle when it's off. Also note that if I end up using a series diode, it'll require biasing a corresponding signal so that the diode won't rectify it when the MOSFET's turned ON. I can't do a basic pull-up because I don't want to attenuate my signal. So I'll pretty much have to use an OPAMP.

Summary:

How do CMOS switches behave when Vdd is grounded?

I need solid state SPST switch that breaks the connection completely (NOT grounding terminals) when power rail is grounded and it should be able to work with AC signals.

Edit-Edit: Updated images with much higher quality ones.
This is a working schematic but it has problems such as DC biasing and headroom in a battery powered application.
Vgs threshold needs to be very low in a real application since I won't have access to high voltages present below.


texts: I made a board that can power a PIC32MX230F064B through a regulated power supply at my college lab. Now I want to power the circuit through USB-A (USB-A to USB-A wire, so I can power it with powerbanks or with my computer). The chip works at 3.3V. I did a little bit of research and USB outputs 5V. I have some doubts in regard to USB always outputting 5V in standard conditions. I also don't know if I need some kind of logical circuit which negotiates the current output that USB gives. I don't know either if it's better to use a regulator or a resistance to go from 5V to 3.3V.


texts: Help decoding resonator/oscillator marking

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I'm looking at a PCB for a car remote (either 314.xx or 433.xx MHz), and the resonator or oscillator (SMD, crystal? ceramic?, Japanese?) has following markings:

0300
T 7205

What frequency could it be, and how to decode these markings in general?


texts: Current flow between metal and piece of pure silicon

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This is a very theoretical question and mainly just for my understanding for current flow.
Let's say I have a DC voltage source. I use two metal wires to connect my DC voltage source across a piece of intrinsic/undoped/pure silicon semiconductor. Everything is at room temperature.

My understanding of the metal wire is that:

It has a very low bandgap energy and thus the covalent bonds in the valence band that the atoms of the metal form with each other break extremely easily and hence we have a lot of electrons in the conduction band, available to flow, just waiting for a voltage to be applied to start moving!
Because of this, it can be thought of as having a 'low' resistance - current flows easily!

My understanding of the piece of intrinsic/undoped/pure silicon semiconductor is that

Its bandgap energy is somewhere between that of a good metal conductor and that of a insulator, hence a semiconductor. At room temperature, some of its covalent bonds will too break and thus some electrons will be available for conduction, just waiting for a voltage to be applied.
The number of electrons available for conduction is significantly lower than that of the metal conductor. Hence, for this example, I think of the pure silicon as having a 'medium' resistance.

From my understanding of basic circuit theory, I draw the equivalent circuit as follows,

From this, I can see that the current flowing in the circuit is limited by the medium resistance of the piece of silicon.
My question is understanding how this current is limited from a atomical level? The metal has excess free electrons, right? Why can't these excess free electrons travel through the lattice? Why do we have to rely on the limited number of free electrons in the silicon piece?


texts: Serial control of 25 LEDs from a single pin

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I have a microcontroller with one available digital pin.

How can I control 25 LEDs?


texts: I have a module that I want to be able to plug into a custom PCB (i.e. not solder directly). The pins of the module are 1mm diameter and would be inserted perpendicular to the custom PCB. What sort of standard sockets exist for this? I have been unsuccessful searching on Digikey and Mouser. The pins are 0.5 inches apart. The module is the following: http://apowerdesign.com/pdf/h30.pdf


texts: Is it worth to assembly boards for low volume lots?

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I'm planning to sell boards I designed but I will start in low volume lots (50 to 100 boards). I 'm seeing if its feasible to assembly the boards ourselves, using SMD stencils and reflow oven. I was reading a lot and it seems quite interesting.
Now, my question is considering the boards are simple (4" x 2" PCB, 2 48-pin LQFP chips,1 SOIT16 chip, 2 USB connectors, 1 DB9 connector, and less than 30 caps and resistors), would it be worth to do the assembly from the cost perspective? I know I can get very low prices in China (or any other place) but I guess I will need to run higher volumes (I guess 1000 or more boards), and I will also need the investment to support that...(components and labor).

My point is not really try to get much lower assemblies costs in this way, but not have to invest that money in such large quantities. (I will not manufacture the PCB boards...Just assemble them)

I would like to hear someone else's experience in cases like this.

update
Many thanks for your inputs. The board is simple, but the added value comes from the Software (embedded and Desktop). Certainly I expect to sell over 1000 over the time, but I don't want to invest in such lotes of 1000... That's why I will start with 100 until I feel confident with this. Now, having said this, and assuming I would assembly the boards in the US, I would like to know if I could save money or not doing the assembly ourselves. The product itself will give me a profit to cover design, firmware, etc. Now, may I make extra money from the assembly, considering lotes of 100 through companies in the US? If I can save $20 per board in assembly costs I would be more than happy... Is this what they would typically ask for the assembly? I'm not planning to do the assembly myself but relatives that need to work, so I prefer to give them the job and save money at the same time. I hope this makes sense....


texts: Low power IR detector for microcontroller wake-up

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I am working on an ultra low power infrared wake-up circuit for a microcontroller (Atmel XMEGA). I have IRDA comms working but the receiver uses too much current to keep on all the time. I need to run for five years on a single battery, so <3uA is the goal. Cost is always a factor, as usual.

In fact my company already produces other products with such a wake-up circuit but they use somewhat expensive op-amps and take up quite a bit of board space. I'm thinking it can be done with just a single comparator, something like an MCP6546.

(can't post images, look here)

The resistors will set the comparison voltage based on what photodiode we pick, obviously. The reason for using it in photovoltaic mode like this is to reduce power consumption.

Will this work? Can it be improved upon? I found this design which is similar but uses a comparator with built in reference voltage.

I could do that too, but it would need to be something like an MCP65R41 that costs a lot less and is available.


texts: CCS PIC C: What is the difference between #INT_TIMER0 and #INT_RTCC?

texts: In CCS PIC C Compiler, there are two interrupts and both are tied to Timer0 overflowing. These are called #INT_TIMER0 and #INT_RTCC. What does RTCC mean and is #INT_TIMER0 not sufficient?


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I am using Arduino to program my ATTiny85 like this.

I am trying to make a simple blink example, here's the code:

void setup() {
  pinMode(0, OUTPUT);
}

void loop() {
  digitalWrite(0, HIGH);
  delay(1000);
  digitalWrite(0, LOW);
  delay(1000);
}

Connected to my programmer (which has a LED connected to pin 0) the LED flashes. When I plug it in to my circuit it does not work (the LED stays on.)

simulate this circuit – Schematic created using CircuitLab


texts: Differences between RC lipo batteries and Li-Polymer batteries in phones/power banks?

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From what I found from WikiPedia (https://en.wikipedia.org/wiki/Lithium_polymer_battery), RC lipo batteries and the Li-Polymer batteries in phones/power banks (like this: https://www.amazon.com/gp/product/B08NPSRS1Y/) are the same, they are both Lithium polymer battery (lipo is just a short form).
If so, what are the differences between them?
People are saying RC lipo batteries are dangerous and people buy safety bags for them (like https://www.amazon.com/s?k=lipo+bag). But people don't talk about this for Li-Polymer batteries in cellphones. The RC lipo batteries also have protection, as I found here: https://www.amazon.com/dp/B07TS2GVS3/. Is it not enough?

【SAFETY &Quality GUARANTEE】The lipo rc battery Built-in protection mechanism ensures safe charging and use.It comes with a balance lead protector, it can effectively prevent the plug from falling off.

The max output current from the Li-Polymer batteries in phone or power banks are usually limited, but the RC lipo batteries are not.


texts: How can I drive 88 solenoids with an Arduino with PWM?

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For a (crazy) upcoming school project I am converting a piano to be a computer-controlled player piano. I am currently planning on using solenoids mounted under the end of the keys (action side obviously, like Yamaha's DiskClavier system as well as the PianoDisc system).

I am planning on using an Arduino to take MIDI signals and drive all of the solenoids. I need PWM on the solenoids so that I can control the velocity at which the solenoids hit the keys, thereby determining the volume. The problem is, its no easy task to control, using PWM, 88 solenoids using an Arduino.

I was think I could use a generic PWM generator to generate the signals, and there are 16-channel servo PWM generator boards out there that are VERY cheap. However, servos require a very specific type of signal that is rather different that generic PWM which I need here. Does anyone know if these will work to generate generic PWM? (link: http://www.ebay.com/itm/PCA9685-16-Channel-12-bit-PWM-Servo-motor-Driver-I2C-Module-For-Arduino-Robot-/272557014281?hash=item3f75a9fd09:g:6SIAAOSwax5Yozsi)

Once I get a PWM signal, can I just use a MOSFET and diode (for kickback-voltage protection) to drive the solenoids directly?

Anything I'm completely missing here?

Any help and guidance is greatly appreciated.

P.S. I know I'm a little bit crazy trying to do this.


texts: Converting boolean function (dnf) to only 2-input NANDs

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I'm currently preparing for an exam and was doing some exercices regarding boolean logic.
Commonly asked question is to build a function from a truth table and simplify it with a karnaugh map.

After that we mostly have to convert the dnf to a circuit with NAND or NOR logic only, usually not the problem, but im struggling to convert this dnf to a circuit with NAND-Gates that only use 2 inputs:

(¬B ∧ D) ∨ (A ∧ ¬B ∧ C) ∨ (¬A ∧ ¬C ∧ ¬D) ∨ (¬A ∧ B ∧ ¬C)

The inputs are available in a double-rail-system, so normal and inverted.

I tried using the rules for boolean logic to extract a variable, so i'd only have 2 variables/inputs per gate left, but was getting confused due to having initial 3 inputs/variable for the AND gates.

Appreciate any help on this!


texts: Decide coherent time and fade duration through empirical studies on the channel and relate them to channel modeling

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I. Scenario:

TX floating in the lossy heterogeneous medium with undetermined positions within a limited region;
RX fixed in the air and closed to the boundary of air-lossy medium;
Frequency: 500 MHz

II. The study:
Received signal level was recorded every 30 seconds for a short duration (30 min) and sometimes no signal could be detected for a while. The measurement was repeated several times.
III. Results:
The received signal varied at each 30-second sampling but overall it could be simplified as a sequence of "square wave with different levels" (the width was around 3 minutes) with a sinusoidal trend.
Questions:

Can I assume 3 minutes to be the coherent time of the channel?
Can I assume the no-signal period to be fade duration?
How to model the channel when the TX-RX distance was not stable? Can I develop a model for the changes of received signal against time?

An example diagram to explain what I meant(Apparently, it's not the real data but resembles a lot)


texts: Good FPGA / Microcontroller development board for real time image processing

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I have been working with OpenCV on Desktop environment for the past one year and now I want to shift to dedicated hardware for my real time image processing applications. I have the following questions:

Which development boards (FPGA/Microcontroller) are good for implementing image processing algorithms? The image capturing device will be webcam.
Will I be able to code in C/C++ and convert the code into assembly level and dump it in that development board?
Will I be able to use libraries like OpenCV in those image processing algorithms?

Since webcams will be used, the image interface/resolution is:

Interface USB 2.0
Resolution max 640 x 480
Frame rate 25 - 30 fps
Depth 8 x 3 for colored image 8 x 1 for gray
Application: thresholding, gesture recognition, object detection, tracking, optical flow


texts: reason to have entire Cu layer as GND connected through via (KiCad)

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This is the first time I am designing a PCB and I was looking at example PCBs drawn in KiCad (the image below is my first PCB, to remove any sources of confusion).

I noticed that oftentimes, when all components are just SMDs and all of them are placed on the front Cu layer, there are vias connecting the GND of the front Cu layer to the back Cu layer.  The entire back Cu layer is just GND.

Is there a good reason to do this? As you can see in the image below, my circuit is simple enough that I feel that the top layer ground pour is good enough for good grounding.


texts: Splicing out a single pair of wires from buck converter for 2 Arduinos and buttons

texts: I'll need to use my 15W 12-5 buck converter to power both Arduinos and for triggering 3-4 buttons. The buck has a pair of wires on the output so I'm trying to figure out what's the most tidy and solid way to splice the one + wire for multiple outputs. Would Wago splices be considered good solution, ok, hack? Any other suggestions?


texts: Tesla Coil Slayer Circuit Not Working [Electroboom's design]

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I tried to make the following tesla coil slayer circuit but it doesn't even turn on. Below are some pictures of what I have constructed. I'm using 3 18650 batteries as the power supply.
I'm not sure how to power the circuit given the schematic, I tried connecting D2 and Q1 (1N4148 and IPI70R950CEXKSA1 mosfet) to earth, and the battery + and - to R2 and the top of the primary coil(L1) respectively, which did nothing. I also tried connecting R2 and L1 to the + end and D2 and Q1 to the negative end, U1 (MIC 4452YM) started gently smoking after this. Hopefully I didn't fry it :(. I also tried flipping polarity and everything in between, to no avail.
Also, I'm using 10 turns for the primary and 2200 turns on the secondary. I don't know how this ratio would impact performance though.
Any tips would be appreciated!


texts: Why is open collector output is called high impedance and what determines the upper limit of the pull-up resistor?

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Is calling open collector output as high impedance due to the value of pull up resistor or due to the fact that the IC itself do not source any current?

And what determines the upper limit value of the pull-up resistor used for an open collector output?


texts: Switching 12V/6A with an AVR - MOSFET or relay or both?

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I want to control the 12V heating of an oxygen sensor with an ATmega328P. It draws about 6A when switched on when it is cold and about 1.5A at the operating temperature of 350°C. It is powered with a 12V/10A switching power supply.

My circuit is measuring weak signals from different sensors (thermocouple and resistance thermometer besides the oxygen sensor) and is a little sensitive to noise, so I am not sure if it is a good idea to connect GND of that big switching power supply with GND of my circuit which I think I have to do if I would use a MOSFET? The insulation between the heating and the connectors of the oxygen sensor is > 30MOhm so at the time being, there is a separation. The circuit is powered by a small 9V linear wall-wart.

To keep both GNDs separated I thought about using a 5V relay that can switch up to 10A but its 225 mW are too much for the AVR, but I guess I could use a relatively simple transistor to drive the relay.

Would that be a reasonable solution or do I worry too much about noise from the switching power supply?


texts: What is this component (probably a shock/vibration sensor)?

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The other day I received a promotional wrist band from a convention booth -- it has two LEDs that flash when you jostle it. I removed the guts to see how it works, and here is what I found:

Most of this is pretty straight-forward: LEDs, a SOT-23 transistor, some passives -- no uC that I can see (on top, at least) --  but I'm interested in the metal can in the middle, with the refdes K1. I assume this is the sensor that detects when the device has been tapped or shaken. It's a metal cylinder with two leads, and on the inside there is a smaller metal cylinder -- it might be a coil or spring, but it's hard to tell. Here's another picture where you can sort of see it:

Does anybody know what this component is called and how it works? Maybe the spring moves when shaken, changing the capacitance or inductance. Whatever it is, it must be cheap (this is a give-away promotional item). It would also be nice, I imagine, if the mechanical energy it collects is enough to wake-up the rest of the device so that it could have a no-power sleep state.

Note, too the shiny metal pad under the near end of the can, perhaps a ground needed for the operation of the device. It looks like there is some clearance between the can and the pad (and the rest of the pcb, for that matter).

UPDATE: Based on the feedback, it's probably a vibration-induced trigger switch, something like this (datasheet), that is, just a spring in a tube that makes contact with the case when it moves.


texts: Will x3 18650 batteries be enough for a nominal 12V vacuum cleaner?

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I am thinking to replace the old Ni MH Battery 12V pack of a B&D PD1200 portable vacuum cleaner with an x3 Li-ion batteries with an overcharge protection circuit. The new Li-ion pack is about 11.1V (3.7x3) instead of a nominal 12V.
So my question is, are 11.1V enough to powerup the vacuum cleaner or it will slow down its functionality? What are my options there?
Thank you.


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The beam former works using time delay to focus the beam pattern on a especific direction, a time delay represents a sample delay in the discrete dominium, that means  that is necesary to use a greater sampling frequency to get more resolution.
I would like to know, a very common ultrasound frequency for ultrasound echography is 1.5MHz and imagin that in an especific case we are using an array of 8 ultrasound sensors, what would be the sampling frequency for each sensor in order to get HD imaging???
Is time delay the only option to steer the beam pattern??


texts: Ribbon Cable Cross Talk - Is there a fix after the fact?

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I'm involved in a project where the customer defined pins in a ribbon cable, without considering possible cross-talk issues. The signals are 1 MHz data signals with no ground wire separating them. I've never had experience with cross-talk and was amazed at the size of the induced glitches (0.5 to 0.65 volts). The receiving side was using 74HCxx line drivers (CMOS switching levels) which resulted in pure garbage on the data stream. The customer is switching to 74HCT drivers in an attempt to move the input "high" switching level below the glitch level, but I have my concerns.

Is the anything that can be done, besides switching to HCT parts or just properly redesigning the board to possibly salvage what we have?


texts: Temperature threshold for electronics components

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I am designing a Li-ion battery discharger. So the discharged power, gets dissipated as heat. Although I have a heatsink and fan, I cannot make the fan work with full speed because it makes so much noise. Inside the software I have a PID which controls the temperature of device. It gets the temperature data from one of the temperature sensors located on the PCB, somewhere near to heatsink but not touching it. So the temperature I measure is less than the real heatsink temperature. I have set the threshold of the PID to 65 Celsius. That makes temperature to oscillate between 63 Celsius and 70 Celsius. So my question is, are the standard electronic components withstand that much temperature for 7-8 hours? Would it effect the component life drastically? As components I have some power resistors, MCU, ceramic capacitors, resistors, diodes etc. I know there is no specific answer for this question, I just want to get some general opinion about it. Thank you beforehand.

P.S: English is not my native language, if there are some parts that needs to be fixed, please feel free to do so.
Edit: There is 7-8 Celsius difference between the hottest component and the measured temperature value.


texts: Capstone PCB for a Single phase power energy meter

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I am an EE major in the process of working on my capstone project of developing a PCB of a Single phase power energy meter and I need help scrutinizing it. I Intend to interface this circuit with my Raspberry-pi 3 (connected at terminals X7-1 and X7-2). The current transformer is going to connected to terminal X6-1 and X6-2. The load for my analysis would be connected to terminals X4. Would really appreciate any relevant comments concerning the progress of my work. Any suggestions here? Thanks.

here is a link to the actual eagle file for viewing.
[https://drive.google.com/drive/folders/1FSukvpItx2aZZGsdDWWjXlnYBVw1Zwx6


texts: Current mirror with different emitter resistors

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(source: play-hookey.com)
I'm trying to analyse a mirror current circuit with unequal emitter resistors, without neglecting base currents. So far, I had no luck with the math.
I found this on a website :

However, if R1 ≠ R2, then the currents through the two transistors will adjust themselves so that the emitter voltages of the two transistors are essentially equal.

It boggles my mind, since I know that Vbe varies with Ic(Ebers-Moll equation). Since Ic1 and Ic2 are different, shouldn't Vbe's be different as well? How would the transistors adjust currents.
Any help is appreciated.
Image and quote taken from:play-hookey


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I have made a circuit to detect the material of a metallic cylinder.  It is able to discern aluminum brass and steel targets, and I used a hard drive voice coil for this.  This is for a machine I am developing for my small business, and I need to find a source of coils.  I don't want to wind my own by hand for quality control reasons, but I'd like to get as close to the hard drive coil as possible:

inside diameter: .5 to .65 inches
length: .1 to .2 inches
number of turns: 150 to 200

My GoogleFoo is failing me.  I can't seem to find anything in this range.


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The question ask me the power that R3 consume,here is the schematic and my calculation

simulate this circuit – Schematic created using CircuitLab

My calculation:

I modify the left part of the circuit,V1,R1 and R2, to this,and use the differential the find that if the R3 is 9 ohms,we can get the max power that R3 consume,and i can know the current  which flows through the R3 is \$2A+\frac{8}{4+3+2+9}=2A+\frac{4}{9}A=\frac{22}{9}A\$, so \$P^{max}_{R3}=I^2R=(\frac{22}{9})^29=\frac{(22)^2}{9}=53.77\$

simulate this circuit

\$V_1^{new}=V_1^{old} \times \frac{12}{12+6}=12 \times \frac{12}{18} =8V\$

\$R_1^{new}=R1 // R2=6//12=4\$ ohms

the current  which flows through the \$R3:2+\frac{V_1^{new}}{4+3+2+R}=2+\frac{V_1^{new}}{4+3+2+9}=2+\frac{8}{18}\$

But the answer of the \$P^{max}_{R3}\$ is not right,the solution said that :

\$R_{th}=9,V_{th}=22\$,and when the R=9 ohms,it can have the  \$P^{max}_{R3}\$
,and the  \$P^{max}_{R3}=\frac{V^2_{th}}{4R_{th}}=\frac{22^2}{4\times 9}\$

I want to ask  why is \$P^{max}_{R3}=\frac{V^2_{th}}{4R_{th}}\$,not \$P^{max}_{R3}=\frac{V^2_{th}}{R_{th}}\$,why should we have to multiply \$R_{th}\$ with \$4\$?


texts: How to design planar toroidal inductors using Altium designer?

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Prior to this, I did spiral inductors which was relatively easy. But I am now stuck in designing toroidal inductors.

I know the distance between each turns but having trouble placing them in circular fashion. Any ideas on how to place them in such manner?


texts:
I too want both supplies (3.3v and 5v) in my circuit and made these schematics:

On 5v supply typical load current is ~8mA.

On 3.3v it is ~30mA.

Regulators are lm1117 in both cases,sot-23 packages and no timing issues
Which one is better?


texts:
I have a very fundamental question regarding string comparison..

I implemented a USART to PC with STM32L0 Nucleo board, and I can type something in terminal and receive it on the micro as follows:

#define RXBUFFERSIZE 1
uint8_t aRxBuffer[RXBUFFERSIZE];

/** Put UART peripheral in reception process */
  if(HAL_UART_Receive(&huart2, (uint8_t *)aRxBuffer, RXBUFFERSIZE, 0xFFFF) != HAL_OK)
    Error_Handler();

I want to compare the received data with a string, but the comparison doesn't work.

char *is_correct= "Y";
if (strcmp((char*) aRxBuffer, is_correct) == 0)
    DoSomething();
else
    DoSomethingElse();

What am I doing wrong? Thanks

How I set up the USART:

/* USART2 init function */
void MX_USART2_UART_Init(void)
{

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 9600;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONEBIT_SAMPLING_DISABLED;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  HAL_UART_Init(&huart2);

}

void HAL_UART_MspInit(UART_HandleTypeDef* huart)
{

  GPIO_InitTypeDef GPIO_InitStruct;
  if(huart->Instance==USART2)
  {
    /* Peripheral clock enable */
    __USART2_CLK_ENABLE();

    /**USART2 GPIO Configuration
    PA2     ------> USART2_TX
    PA3     ------> USART2_RX
    */
    GPIO_InitStruct.Pin = GPIO_PIN_2|GPIO_PIN_3;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF4_USART2;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  }

}


texts: Arduino controlled regulator circuit to control two Peltier devices,

texts:
I am needing to find an arduino controlled circuit that will control the temperature in a box enclosure utilizing peltier devices.

So far, I have a SR7021 temperature sensor wired to an Arduino Nano via I2c. What I have envisioned is a Peltier device for cooling the box with another Peltier device heating the box.

At the programmed temperature both Peliter devices would have a low voltage applied , in effect cancelling each other out. When the temperature rises, the voltage to the cooling Peltier would rise and the voltage to the heating device would drop and vice versa when the temp drops.

The solution can utilize two circuits each driven by separate pins on the Arduino but ideally a single circuit with two controlled drivers for the Peltiers. Can anyone point me in the right direction?

Thank-you,

Rick


texts:
I was instructed to set up a resistor on the negative side of the LED and pulling it to ground. I'm confused why we are implementing a resistor on the backside (negative end) of the LED. I always thought we put resistors before our load (LED) to limit/control current flow. Therefore, I'm confused why we are putting the resistor between the cathode (negative end of LED) and ground. To me it seems like this resistor isn't doing anything.

I don't know if it helps but on my board the positive side of the LED is connected to PIN 13 and the negative (cathode) end is going to the resistor then to the ground on the breadboard then to the ground pin on the Arduino board.

I apologize for the picture as it's the best I can get it at the moment with what I have available to me.


texts:
I have a passive crossover between my amp and subwoofer. However too much high frequency is coming through, I'd like it more subby.

If I were to add another passive crossover, so the wires going to the sub instead run into a second crossover module, would I be doubling the frequency rolloff?

Update with existing crossover

I have what is described as "600w RMS Subwoofer Crossover 4 Ohm 12dB/Oct" which are very common on eBay, around 13.00GBP.

I thought 120Hz was too high when I bought it - esp. after accounting for the rolloff - but there's nothing else on the market. Ideally it'd be variable like on many amps.

Indeed it sounds too mid-bassy, like for rock music, while I play house music with much deeper frequencies.

So I was wondering if I can simply add another! Else I'll need to buy something more expensive to augment on the signal side.

Thanks for comments.


texts: How to calculate the required number of FPGA logic elements?

texts:
I have a Lynxmotion hexapod which uses hobby servos for each of its 18 degrees of freedom (DOF).

The basic problem with this is that I cannot get data on the joint angles. I have modified the servos so that I can measure their orientation via the signal from the pot. For each DOF I want to read in the orientation of the servo via ADC and use a PID controller to generate the appropriate PWM signal. This works simply enough with an Arduino for one servo.

Unfortunately I have not found any microcontrollers with 18 10 bit (or higher) timers capable of generating PWM and 18 ADC. As such I am exploring the idea of using an FPGA. Specifically I'm considering the Papilio Pro FPGA. In reading about it I see that it has around 500,000 logic elements. While I'm new to FPGA I'm guessing this is the most crucial metric for my needs (if I'm wrong, please feel free to correct me).

The question in my mind is, how many logic elements do I need for my application? Are there any good rules of thumb for such calculations?


texts: Why isn't my ground plane in Kicad connecting all of my grounds?

texts:
I'm building a low noise power supply and when I try to pour the ground plane, some of my grounds are still unconnected. I tried redoing the board this morning, but I'm still having the same problem.

I've attached both the schematic and the PCB. Please let me know if you have any ideas. Thank you!

UPDATE:
I changed the position of C1 and added an exposed GND pin to the schematic but that's also not connecting to the ground plane. Are there settings on it that I need to change to have them connect?


texts:
I would like to know what is the best possible way to solve the following problem:

I want to have a touch screen over USB this touch screen should be able to receive Graphics from the attached PC, so there will be a driver installed on the pc itself. The touch screen should be very responsive (almost like most smartphones), can Arduino or Raspberry Pi do this ? Or should I go with ARM chip sets?

Found this on ARM website
http://www.arm.com/markets/embedded/embedded-computing.php
Looks something that i relating to me, but want to know is it abel to recieve the graphics from the attached host (PC)


texts: Meaning of small circles and sharps (#) in pinout diagram?

texts:
I'm trying to re-plumb a nice proprietary case for continued use with arbitrary motherboards.  But I've no clear idea what the meaning of the small circles (shown in red, here) at the juncture of the traces is, or of the # chars on the descriptors.

I thought the circle might simply mean negation, as it does in gate symbols, but I'm not really confident that that's true, and it still leaves me in the dark about the # that terminates some of the descriptors.

Searching the web hasn't helped.

[EDIT] Okay, someone else asked about the circles (229425), and now I know that they do mean negation.  But I still don't understand the #s.


texts: Assembling and Dis-assembling a Charged Capacitor

texts:
If I have an electrolytic capacitor, which is a cylindrical body in which the two plates are rolled-up with a dielectric paper in between them, of very high value (say 1F) and I charge it using a DC battery source, disconnect the battery so the charge is stored in the capacitor, and then I un-roll it's paper-electrodes and take them apart from each other.

Then what will happen to the electrical field (energy) which was stored in the capacitor before un-rolling its electrodes?

If I now bring back together the two electrode-papers again and roll-them-up into its original shape will I again get back the original energy which was there in it when the capacitor was charged originally?


texts: How to make a digitally controlled power switch?

texts:
I am new to electronics. I want to make a power switch controller by a digital pin as shown on the following figure.

How to do this safely?

Update: I forgot to let  you know the bulb is just an example for the sake of drawing. The real scenario, it is a female socket into which any equipment male socket is inserted.


texts: Testing changing sheet resistance with impurities

texts: I have a chemical film, and I'm trying to detect the presence of impurities on the film. They should change the resistance. Assuming it does, how do I measure it? I believe the four point probe method might be right, but as far as I can tell that method is for uniform sheets without impurities. Will I be able to detect a particle on one side of the film even if my probes touch on another side? How does an impurity somewhere far away on the sheet affect the resistance close to the probes?


texts: Calculating capacitance for three conductor transmission line

texts:
The black part is the insulation, brown part is copper.
How can I calculate the capacitance between the two small copper cables?
There are 3 conductors, 2 of them inside the big conductor


texts: Admittance, Conductance, Susceptance definition

texts:
Admittance is the reciprocal of impedance. But:

1) Susceptance is the reciprocal of reactance, or the imaginary part of admittance ?

2) Conductance is the reciprocal of resistance, or the real part of admittance?


texts:
Problem: Assuming that diodes are ideal, find I and V.

This is a worked example in the textbook and it says that if you assume both diodes to be conducting then V=0 and VB=0 (nodal voltage at B).

I don't understand how the voltage at B is 0.

What I'm getting confused about is how can there be a current through D1 if it's connected to ground and also does ID2 go to ground or does it flow into the node? I get that if you assume the diodes are conducting you short them, but I can't see how that allows one to assume that the potential difference between B and ground is 0? I get that the sum of the currents flowing into B must be zero, and that the diodes conducting means you short them, but does this mean that the voltage drop (increase) across the 5k resistor is 10V and the voltage drop across the 10k resistor is 10V?

Any explanation would be much appreciated.


texts: How to Make Sure SIM900 modem will always give me +PSSUTTZ string?

texts:
I am using SIM 900 modem to enable GSM connection wirh my product.
Micro-controller Communicates with SIM900 modem through a SET AT commands over UART.
My product is time critical and i need to have updated time even after power failure.
To achieve this I am using inbuilt RTC of SIM900 modem.
After each power ON I send following sequence to modem:

AT+CFUN=0
AT+CFUN=1

After this I am supposed to get +PSUTTZ string from modem which has timestamp in it and it indicated that modem has synchronized its time with network.After this after this I send AT+CCLK? command periodically to modem to read its RTC.

The problem is sometimes I does receive +PSUTTZ string from modem with some Service providers. With BSNL(in India) service provider I never able to get this string.

Anyone has Idea that how to make sure that +PSUTTZ will always receive without fail?
(May be some different AT commands or something?)


texts: What happens if i rotated a DC motor's rotor?

texts:
a 3V DC motor. If i rotated its rotor at a constant RPM without any DC input, what will the output current be at the terminals?

will it be a constant Sine wave or DC?


texts: Do I need external pull up resistors for TX and RX lines in CP2102N?

texts:
I want to use it to program a microcontroller and this is the recommended set up from the data sheet. I was wonder If I need these resistors or not.

I am not asking if STM32 chips require pull ups. I know they are required I am asking whether they are built in Silicon Labs CP2102N or not.


texts: The advantages and disadvantages of the monolithic filters

texts: Recently I noticed there are some monolithic filters on the market, such as http://www.linear.com/product/LTC1065. I want to know what's their advantages and disadvantages comparing to the normal active filters made by discrete R,C and Opamps. What about using them in high precision measurement?


texts:
I was watching this YouTube video.  The content maker simply declared that 200/300 volts DC is safe to touch.

I think the capacitor used in that circuit is limiting the current. That's why nothing is happening to him.

I have seen my friend to get injured by touching the supply line of 400 volts DC generator in lab.

My question is - Is it really to safe to touch any DC supply (200- 300 volts) without considering line impedance or the maximum current that can be provided by the source?


texts: Using if/else syntax for assign statements

texts:
I have a wire to which I assign a complex right-hand-side expression with lots of bitwise operations. This right-hand-side expression is quickly becoming long and hard to maintain.

Is there a way I could replace the bitwise operations by if/else or case statements to help readability and maintability?


texts: digital input levels based on another circuit (using a transistor switch?)

texts:
I would like to control some microcontroller¹ code based on the status of a push-button switch in an external 3.3V circuit via a digital input.

The external circuit has a little under 3.3VDC going through a SPST push-button switch, normally open.  I don't have access to the rest of the circuit (it's pretty thoroughly hermetically sealed, and I'd like to avoid destroying the device), but I can splice into the switch line, either parallel across the switch or in series with the switch.

UPDATE: voltage measurements of the switch:

across open switch: 3.15V (±0.01V)
common ground to open switch, + side: 3.25V (±0.01V)
common ground to open switch, - side: -0.01V (seems to vary between -7mV to -11mV depending on what the microcontroller is doing)
common ground to either side of closed switch: 3.25V (±0.01V)

The switch can't be hooked in series directly to a digital input, as there seems to be too much resistance in the microcontroller for the switch to complete the external circuit.  A 330Ω resistor in series with the switch seems not to interfere with the operation of the external circuit, though.  I should also note that the external circuit and my circuity will in most configurations share a common ground.

I have managed to get the code to respond as I want with the switch wired in parallel to an analog input (with a resistor in series).  However, I would like to leverage interrupts (instead of looping to read the analog input), so would like to use a digital input instead.

My initial approach to changing the level of the digital input based on the external circuit's switch has been via a transistor switch.  I have attempted both an NPN- and a PNP-based switch, but haven't managed to get the resistor values right to even completely switch an LED on and off with the external circuit (most recent attempts have been in series with the switch, but I've tried in parallel too).

If a transistor switch is indeed a good approach, I would like guidance in how to get this right.  Is an NPN or PNP switch better (my guess is that NPN is going to be more problematic, given that they share a common ground already?)?  How should I go about calculating the resistor values to get the output right for proper 0/1 levels in a microcontroller digital input, and also allow the external circuit to respond properly when the switch is closed?  Should I use the negative or positive side of the external circuit's switch in controlling the transistor switch?

¹ I'm currently working with an ATmega328P board, but I plan to switch to an ATmega32U4 board as I continue development in order to use a few of the extra features available with that board.


texts: Power needed to generate for heating strip - Nichrome strip element

texts:
I have a nichrome strip, about 8 mm in width - 0.25 mm in thickness - 1 m in length.
I tried working around various formulas but can't seem to get a definite answer regarding how much power should i generate for 270°F heat roughly.

Much thanks

*Edit

The strip is to be used in an impulse sealer. Therefore the main usage will be sealing plastic bags at most. It will be working at room temperature so i would say there are not alot of external factors. Seeking advices..thanks!


texts: I am watching this video about lumped matter discipline, and I'm not sure for what is it used? Why and how we can make dq/dt be zero? What LMD says about circuit element? Does dq/dt represents excess of charges because of non ideal element?


texts: PWM generation with master/slave timer configuration

texts:
I am going to generate a PWM with master/slave timer configuration. I prefer that my master timer generates PWM with an interrupt. I need to connect this interrupt to another timer as its input clock to count the number of the pulses.
Based on this diagram, what should I do?

I enable my timer to generate PWM.
Enable timer interrupt for each pulse.
How to connect this interrupt to another timer?
How to configure it as master and the second timer as a salve?
Is it necessary to define these timers as master and slave timer, or is connecting the interrupt as the second timer enough?


texts: Why am I seeing drift when using Madgwick algorithm to correct for orientation with 9 DOF IMU?

texts:
I am trying to correctly track orientation of a sensor with accelerometer, gyroscope, and magnometer, using the open source Madgwick algorithm. The algorithm returns quaternions which represent the rotation between the internal and external frames. However, when using this code the quaternions returned seem to be suffering from drift and even after digging through multiple times I can not find what may be the cause. On the top is what is returned, and the bottom is the approximately correct values (from an experiment with a different sampling frequency): .
Could this be caused by too low of a sampling frequency? The internal Madgwick report shows a lower bound of 10hz, and this sample was taken at 5hz. However it is not clear to me how that issue would produce these results, but that is currently my best guess. I think the issue could also be the linear acceleration from gravity, but my understanding is that gravity's influence can be removed once the quaternions have been calculated - so if that is indeed the issue how can I remove linear acceleration to calculate them in the first place?

Edit: The accelerometer and gyro values are not suffering from drift, and this effect only emerges with the calculated quaternions.


texts: I have a battery pack consisting of 4x1.2V AA Sanyo NiMH Rechargeable batteries used to charge a Beagleboard device. I want their discharge output to not exceed 5V. But when they're fully charged, the voltage output is over 5V (it triggers the overvoltage detector of the Beagleboard). What is a simple (and relatively small) intermediate component I can place between the battery pack and the Beagleboard to limit the voltage to under 5V?


texts:
In many documents and books, the collector base junction of a BJT transistor is usually represented as an inversely polarized diode, however there is no collector base voltage that we must overcome since as soon as we apply 0.7 volts to the base the transistor already conducts between emitter and collector without offering resistance
Is the collector base junction really misrepresented as a reverse biased diode?
Thanks


texts: What sensors would be suitable for measuring masses of the range 0.5 g to 1g?

texts:
I am working on a project that involves measuring objects whose masses range from .5g to 1g.
Preferably looking for something small and thin but at this point, anything that accomplishes the task is also welcomed.
I did some research on force-sensing resistors and even though their physical dimension was suitable for my project, I am yet to find one that is capable of measuring masses ranging from 0.5g-1g.
(Project details -> The object would be mounted stationarily on a platform with the sensor underneath the platform. The sensor then produces an electrical value that can be used to deduce the objects' mass/weight).
Thanks
 Update 8/22/2020.
Since the previous accuracy requirement was extremely difficult to achieve I have refined the accuracy requirements.
Accuracy +- 0.05g


texts:
I need to use an AD 8302 Gain and Phase detector along with a SynthHD frequency generator to design a Vector Network Analyzer. Before I get to that I wanted to try and obtain readings on my PC. There are many projects online that seem to show readings taken from the AD 8302 sent to LabView and Matlab where the results are shown graphically, however nothing specifies how to make the connections and what coding is required.

Here is the link to the datasheet for the AD 8302. How do I obtain readings using an AD8302?


texts:
I have already asked this question but again I am asking it with a clear view. As u can see in the diagram attached I need to divert power coming from inverter. I want to maintain the power flow either through the short circuit line or through inductor using switch, Relay or jumpers.

I have thought about doing it with switch but then I thought It is difficult to find out the switch with this rated current.
(Good thing is I do not switch when the system is working)
When I looked about the jumpers I could not find it with higher rating. I found some power connecters but I am not sure how to use it.
But jumpers seem cost effective and also consume less space.
I found many relays which is rated for my application but the size are very big. I think I have to use min of 800V rating Relay just to be on safer side because of the voltage spike.
Please suggest out of 3, which way is best suitable for this application. U can suggest any other ways like any connectors which would do the job with less losses. Thank you


texts: Why does this not work for all transfer functions?

texts:
When we analyse electric circuits we often use transfer functions. To calculate the poles and zeros of such a function can be done in different ways. When we look to a transfer function in the Laplace domain, it looks like:

$$\text{H}_{\text{T}}\left(\text{s}\right)=\frac{\text{Y}\left(\text{s}\right)}{\text{X}\left(\text{s}\right)}$$

Now, if we want to set it in the complex frequency domain we substitute:

$$\text{s}=j\omega$$

Where $$j^2=-1$$.

Now we substitute that into the Laplace domain transfer function:

$$\text{H}_{\text{T}}\left(j\omega\right)=\frac{\text{Y}\left(j\omega\right)}{\text{X}\left(j\omega\right)}$$

To calculate the (absolute value of the) poles and zeros of the original transfer function (in the Laplace domain) we can solve:

 1. When we have one capacitor or inductor (called cutoff frequency):
$$\Re\left[\text{H}_{\text{T}}\left(j\omega\right)\right]=\Im\left[\text{H}_{\text{T}}\left(j\omega\right]\right]$$
 2. When we have more capacitors or inductors or a combination of these two (called resonance frequency):
$$\Im\left[\text{H}_{\text{T}}\left(j\omega\right)\right]=0$$

  Question: For which transfer functions does this hold, that you can calculate the poles and zeros of the Laplace domain transfer function, using the complex frequency domain as stated above? Because it does not work for all transfer function? And how can we prove that it only hold for some transfer functions?

Circuits where it work, for example a simple RC series circuit. Because:

$$\text{H}_{\text{T}}\left(\text{s}\right)=\frac{\frac{1}{\text{RC}}}{\text{s}+\frac{1}{\text{RC}}}$$

And:

$$\text{H}_{\text{T}}\left(j\omega\right)=\frac{\frac{1}{\text{RC}}}{j\omega+\frac{1}{\text{RC}}}$$

They give the same result (poles and zeros):

$$\left|\text{s}\right|=\frac{1}{\text{RC}}$$

And:

$$\Re\left[\text{H}_{\text{T}}\left(j\omega\right)\right]=\Im\left[\text{H}_{\text{T}}\left(j\omega\right)\right]\space\Longleftrightarrow\space\omega=\frac{1}{\text{RC}}$$

EDIT:

When I have a series RRL circuit, my transfer function looks like:

$$\text{H}_{\text{T}}\left(\text{s}\right)=\frac{\text{R}_2+\text{s}\text{L}}{\text{R}_1+\text{R}_2+\text{s}\text{L}}$$

Finding the poles and zeros of that function gives my different values for \$ \omega \$ then when I solve:

$$\Re\left[\text{H}_{\text{T}}\left(j\omega\right)\right]=\Im\left[\text{H}_{\text{T}}\left(j\omega\right)\right]$$

Using:

$$\text{H}_{\text{T}}\left(j\omega\right)=\frac{\text{R}_2+j\omega\text{L}}{\text{R}_1+\text{R}_2+j\omega\text{L}}$$


texts:
It has been suggested that one of the reasons typical RISC CPUs stop at 32 architectural integer registers, despite a 32-bit instruction having enough spare bits to specify 64, is that a larger register bank takes more time to access, which would impact clock speed.

However, modern CPUs typically have even more than 64 physical integer registers, using register renaming to map architectural to physical.

Does this mean process technology eventually made circuits fast enough that a large register bank can be accessed quickly after all? Or is there a reason physical registers don't impact access time as much as architectural registers?


texts: TVS/Bidirectional Zener for N-MOSFET Gate Protection

texts:
I am using a MOSFET to read a square wave, which usually ranges between -1 and 16 V. However, on occasion, the signal can reach values of -30 to 45 V. My current setup uses a Zener-protected STN3N45K3 MOSFET (max Vgs +/- 30 V). The circuit is shown below. Note that the RPM_DI signal is connected to a microcontroller input, which is pulled-up to 3V3 via a 1K resistor. The input driver signal goes in through pin 3 in P20. Note also that D15 is the TVS diode I am planning on installing.

My questions are:

Would it be a good idea to add a TVS diode (in the position of D15), with a Vcl < 30 V, such that I am protecting the MOSFET (additional to the included Zener)?
If so, could the TVS diode become damaged due to the higher voltages? Note that when the signal reaches -30 to 45 V, these are not transient voltages, rather the square wave will stay at these voltages permanently. I don't, however, expect large currents.
Should the TVS diode be placed before of after the gate resistor (R22)? If placed after, I understand the resistor would limit the current through the diode. If placed before (as in the current schematic above), I'm not sure what the current through the diode would be (?)

I guess my question is somewhat similar to what was asked here: Mosfet Gate-Source Zener. In terms of this other question, I would ask: Could the Zener become damaged after continuous application of the 30 V signal? Does this depend on the power dissipated by the Zener? If so, how would I calculate the power?
If anyone can help, I'd appreciate it!


texts: Why did I get "Internal polygon error 71" in eagle?

texts:
I attempted to create a ground plane for my circuit with the polygon command but this time, I get a weird problem. Normally when I create a rectangle and rename the polygon to GND (ground), I'm asked what the new name of the track should be and then the blank spots of the circuit board are filled in mostly with GND which is normal.

However, this time, I did the same thing to a bit more complex of a circuit, and just after drawing the polygon and associating it with GND, I get the following error:

Error:

ABORT: Internal Polygon Error 71

It gives me an OK and cancel button to click on. Once I click on either button, the entire program immediately exits.

What could cause this? and I'm using Eagle 4.16r2.


texts: How to power ADXL362 with consumption as low as possible

texts:
I'm designing a product which requires total consumption as low as possible. I came across adxl362 with ultra-low power consumption. However, I didn't figure out how to power it efficiently.

There product will have a single-cell LiPo rechargeable battery as a system power. Its voltage will be between 2.7v ~ 4.7v . A main MCU with internal LDO and DCDC, which could work between 1.8v ~ 3.6v, but is recommended to work above 3.0v due to current leakage in lower voltage , an ADXL362 could act as a motion switch .

I intent to use a buck-boost regulator to power the main system under 3.0v, i.e. main MCU. But how to drive adxl362 efficiently (preferred at 3.0v due to Vddi/o limits)?  adxl362 need to work when main MCU works or not. The buck-boost regulator's quiescent current is even higher (100 ~ 200 uA) than adxl362.


texts: Issue getting relay to trigger, coil voltage might be insufficient

texts:
I have a simplisafe home alarm system. All components of the alarm(keypad, base station, sensors, alarm) are wireless, so there are no wires running to any sensors. I wanted to add an additional siren with some bark, not another wireless mediocre "siren" from the manufacture.

I needed a way to trigger a relay to turn on the additional wired siren I purchased, so I turned to taking apart the wireless stock siren. I probed around on the circuit board and found a pair of circuit pads, which were labeled(T6 & T9) But had no wires connected to them. The pads provided battery voltage (6V) when the wireless siren was going off.

So I thought I was all peachy, but when I connected the relay coil to the terminals I found out that the wireless alarm would not operate at all. Is there some kind of diodes or something that needs to be installed inline with the relay to allow the wireless siren to function, and also inturn be able to energize that relay coil ? With the relay not connected, the alarm continues to work properly. I can get a picture of the wireless alarm circuitry, I am not very familiar with the components to name them.


texts: What is this type of write-protection called?

texts:
Upon powering up, flash memory is read/write. At some point during the startup phase, the firmware, the bootloader, or maybe even the kernel triggers some mechanism built into the flash chip that write-protects parts or all of flash memory at the hardware level. This write-protection cannot be reversed by software running on the device and can only be reset by removing power to the flash chip. Variations of this mechanism are used in certain Archos devices running the SDE firmware and in some older Android phones. What is this kind of write-protection called? I'm trying to search for chips and devices/SBCs/boards that have it, but my search terms don't turn up many results.

I am not talking specifically about the S-ON/S-OFF thing. That is a variation of the mechanism, but it is more involved with special designs involving the Qualcomm modem.


texts: Why does a Thévenin equivalent exist but not a Norton Equivalent, and vice versa?

texts:
In the following diagram, the Thévenin equivalent of the circuit on the left is shown on the right:

simulate this circuit – Schematic created using CircuitLab

However, it appears that there is no Norton equivalent for this circuit.

Similarly, the following diagram shows a circuit whose Norton equivalent exists, but there appears to be no Thévenin equivalent for it:

simulate this circuit


texts:
I'm currently attempting to mod my snes jr for rgb output. This requires me to solder some ribbon wire into 4 through holes. I did this once but I (stupidly) made the wire too short and had to remove it using solder wick. I must have done this incorrectly because now the through holes have a few tiny bits of wire in them and I am unable to insert a new wire  (I apologize if the picture is low quality it was taken with a cell phone). What soldering/desoldering techniques would one use to clear out these through holes? I have most common soldering tools outside of a desoldering station (I just have a self-heating pump).

Worst case scenario, is there anywhere I could send this to be finished off by someone who's better at soldering? Thanks.


texts: Using transformer that have same frequency with resonant frequency of primary coil for tesla coil

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Sorry im still beginner at electronic.
So im thinking if we use spark gap just for trigger primary coil oscillating at resonant frequency, can we just use transformer that oscillating at primary’s resonant frequency?


texts: Proteus VSM: digital vs analog resistor and LED

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I'm a newbie to electricity and electronics in general.  I've been reading about the principles and have a basic understanding of them.  I'm also diving into creating my first basic circuits with Proteus VSM to be able to simulate them and hopefully understand and learn in the process.

The reason I'm mentioning this is that if there's any logical mistake in my question, I'd be awesome if you could point me towards what I need to read about.

My setup:
I have a basic circuit using two digital-output MCU pins (using an arduino, two pins in OUTPUT mode), a resistor and a LED that lights up as soon as I run my simulation.

I'm simulating this with Proteus VSM although I believe this question is generic.

My doubt:
Proteus VSM allows you to configure the resistor and LED as either analog or digital.

Is there a difference between those setting for resistors and LEDs?  Do these components exist in digital and analog versions?


texts: Controlling esp2886 via bluetooth... help!

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I am trying to control my esp2866 via bluetooth so I bought a DSD TECH SH-M08 Bluetooth 4.0 BLE Module. In a tutorial I saw they paired it to the computer and then under 'More Bluetooth Options', in the COM Ports tab it shows up and you simply take the COM port it's connected to and put it into your code.
For some reason though, the module doesn't show up in the COM Ports tab. It does however show up in device manager.
Another way of connecting it is via the AT Command line however I don't fully understand how to do this.
I also have an HC-05 but it runs on 2.0 BLE can I connect this to my computer? My computer doesn't seem to be able to detect it.
Any help is appreciated.


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I am attempting to make an alarm on AC main failure based on Arduino Mini Pro.

The idea is that when AC main failure happens the Arduino Mini Pro shall wake up and periodically "beep" between "sleeps."

I want to use 3.3V/8MHz version of Arduino primarily sourced by AC adapter and to use its hardware interrupt to detect the AC failure.

When AC fails it should be powered by coin cell battery until AC main returns. Primary goal here is to work on battery as long as possible.

While reading various posts, threads, articles, I understood that this should be done with op-amp and MOSFET but struggling to figure out how.

Because of coin cell battery's low voltage to power 3.3V Arduino, I understood that solution based on Schottky diodes are not the right option, especially due to reverse current it may blow up my battery over a time.

Appreciate experts' help!


texts: Do I need to get a device certified by the FCC if it uses the ESP32/8266?

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I plan on making a device that the user can control with their phone via a WiFi connection to an ESP8266 or ESP32. If I end up selling this device, will I need to get it certified?

The ESP32/8266 has an FCC ID written on it. Does this count, or do I need an FCC ID for my device? I don't plan on selling more than 100 of them, so it would be too expensive for me to get it tested.

Does the answer to this question depend on whether I:
Use an external antenna?
Use a readily available ESP breakout board?
Design the ESP directly into my board?


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Is there a way to dump the memory in verilog using vcd dump?
Since now i have written this:

module sampler(clk, pixel);

    input clk;
    input[7:0] pixel;

    wire[7:0] pixel;
    reg [7:0] macro_block [0:63];
    reg [5:0] address;

    always @ (posedge clk or negedge clk) begin
        macro_block[address]=pixel;
        address<=address+1;
    end
endmodule

module tb();

    reg clk;
    reg[7:0] pixel;

    sampler s(clk,pixel);

    initial begin
        $dumpfile("test.vcd");
        $dumpvars(0,tb);
        clk=0;
        pixel=1;
        $monitor("%g %b",$time, clk);
        #5 $finish;
    end

    always begin
        #1 clk <= ~clk;
    end

endmodule

but the array macro_block is not shown in gtkwave, is it possible to shown?


texts: How can I measure the current draw of a device without powering it?

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I'm building a DIY security system for my home, but I'm using the existing sensors and siren that are already installed from my old security company.

So, I don't know the current draw of the siren or have a part number for it to look up the datasheet, but I'm attempting to make sure I have a sufficient transistor/relay to switch it on. All I know is that the siren is 12V (from measuring the alarm output of the previous system with a multimeter).

Is there a way I can measure the current draw of the siren without actually sending current into it? It blares at around 105dB, so I'd love to try to figure out a way to determine this without the deafening tone or attracting the attention of my neighbors.

I considered measuring the resistance of the siren, since it's probably just a piezo, and using Ohm's law, but I'm not sure that would give an accurate estimate without knowing what kind of other driving circuit, etc. is inside the siren.

Any suggestions?