texts: mush instead of signal stm32 nucleo-l053r8

texts:
Generating a triangular signal. The "printf" line is commented out. If the "printf" line is uncommented, instead of a signal, mush.
How to fix it? (stm32 nucleo-l053r8)
#include "mbed.h"
#if !DEVICE_ANALOGOUT
#error You cannot use this example as the AnalogOut is not supported on this device.
#else
AnalogOut my_output(PA_4);
AnalogIn analog_value(A0);
DigitalOut led(LED1);
#endif
#define RANGE (0xFFFF)
#define BUFFER_SIZE (256)
float AMPLITUDE=0;

uint16_t buffer[BUFFER_SIZE];

void calculate_sinewave(void);

float meas_r;
float meas_v;

int main() {
calculate_sinewave(); //generating a triangular signal
while(1) {
for (int i = 0; i < BUFFER_SIZE; i++) {
float arg = buffer[i];
my_output.write_u16(arg);

meas_r = analog_value.read(); // get the value from the ADC port (value from 0,0 to 1,0 = full range ADC)
meas_v = meas_r * 3300; // Converts a value in a range 0В-3,3В

//output the value to the "Terminal" program
//uncommented="mush"
//printf("measure = %f = %.0f mV %f \n\r)", meas_r, meas_v, arg);

    if (meas_v < 300) //if the meas_v value is less than N mV, the LED lights up
    {
        led = 0; // LED ON
    } else {
        led = 1; // LED OFF
    }

wait_us(100); //delay for the eye to see the blinking of the LED
}}}
void calculate_sinewave(void){
for (int i = 0; i < BUFFER_SIZE / 2; i++) {
AMPLITUDE+=(0.00244);
buffer[i] = (uint16_t)(AMPLITUDE*(RANGE));
}
for (int i = BUFFER_SIZE / 2; i < BUFFER_SIZE; i++) {
AMPLITUDE-=(0.00244);
buffer[i] = (uint16_t)(AMPLITUDE*(RANGE));
}
}```


texts:
First, let me say that I'm very new to electronics so this issue may just be down to me doing something wrong.

Here is my multimeter:

It started when I was trying to test the gain of a PNP transistor. The expected values were 0.016mA for base and 3.1mA for collector. I kept getting 0.03mA for both. My multimeter has 1 terminal for A and another terminal for everything else, including mA (I was using the mA terminal). I assumed I was just doing something wrong but eventually decided to test the multimeter on a simple circuit.

I connected an LED, a 470 ohm resistor and the multimeter in series as a test. With no multimeter, the LED is on. Using the A terminal, the LED is on and has a value of 0.014A. Using the mA terminal, the LED is not on and the reading is 0.03mA.

So my question is: am I just messing this up somehow or is my multimeter broken?

The options I have considered are:

The multimeter is working and I have just made a mistake somewhere.
The current in the test circuit with the mA terminal is actually 0.03mA. The low current could be the reason the LED isn't turning on. But why would it work fine using the A terminal?
The multimeter with the mA terminal is not forming a circuit for some reason. This would explain why the LED won't switch on. However, the multimeter reading does increase from 0 to 0.03mA once the battery is connected, which suggests some current is flowing.

All in all, I'm very confused. I only started this a few days ago so have no idea what I'm doing. I did test the current of the same test circuit yesterday (using the mA terminal) and I didn't notice it giving a really low value, but I wasn't really paying attention.


texts: So getting to the point. Ive got makita brushed cordless drill with dead batteries as those arent really cheap ive decided to try to power it through a microwave transformer. According to the switch it draws 12A at 12V. So after rectifying(kbpc2510) the 14V AC to around 12.2V DC  i though this would run perfectly. But it didn't. The drill didn't work if i didn't press the switch fully and after I applied a load to the motor the bridge rectifier fried. So im asking what i should do to power this with a cable from microwave transformer?


texts: Interfacing 16 antennas to a mux to read an RFID TAG

texts: Does a mux IC (16x1) affect the impedance of an antenna ? I was thinking of interfacing 16 antennas to a mux and read just one of them through the S6350 reader. My first solution was to use a MUX (16X1), but my professor said that wont work becuase there is high chances that the impedance missmatch thus making the antenna useless. The antenna RFID reader and the tag operates at 13.56 Mhz. My question to you is how I can make 16 inputs to one output( attached to the reader)? Is the things he is saying true ? I have seen other projects using muxes with antennas but he was saying it was a lot of active componenets inside a mux that can change the impedance thus make the antenna useless.


texts: How do USB hubs work when same device is connected

texts: I was reading on how USB hubs work and since there is only 1 master, master sends a command to an endpoint. However, how does a USB hub work when there are 2 same devices plugged into a USB hub? How does the device know which is being addressed?


texts: DC motor gets stuck when it hits the end of its track

texts:
EDIT: Solved, I'm not sure how to mark it as solved though
I don't really know what this phenomenon is called so if this question has been asked before I apologize.
Basically I have a dc motor and it has a "finger". When the motor spins it reaches a switch that stops the motor and presses it. Afterwards the motor is supposed to reverse. However, it gets stuck?? I don't even know what its getting stuck on, I have to spin it manually for it to reverse. This happens when it encounters any barrier - like a wall for example. I have no idea what even is causing it to not spin, is it something to do with its internals locking in because of it continuing to spin after the switch stops it?
The motor spins a worm gear that spins a normal gear that the finger is attached to.


texts: Powering a 5v raspberry pi, a 12v motor and a 24v motor using 2 batteries charged with a solar panel

texts:
I want to control a 250W 24v motor, as well as a 12v 1W motor using a raspberry pi. It needs to all be powered by 2 lead acid batteries which are being charged when not in use. My plan is to use two of these.

One connected to each 12v lead acid battery, wired in parallel to the solar panel. For the 24v volt motor, I will wire both of the adapter things in series. For the 12v motor, I will wire it straight onto one of the the adapter outputs. For the raspberry pi, I will use a 12v-5v converter and wire it straight onto the other adapter's outputs.

Will both batteries charge at the same speed?
Will the raspberry pi or 12v motor get fried to a crisp?

Thanks.


texts: Simulating cable length during TDR testing

texts:
I am trying to create a circuit that can be used as part of a TDR simulator.

What I need to know is if it is possible for the pulse that is sent out by the TDR equipment to be delayed by a piece of circuitry in order to simulate a length of cable. The pulse would then return back to the equipment for analysis.

If anyone has done this before or has any ideas it would be very much appreciated.


texts: A cheaper way of Lipo battery charge and power switching

texts:
I have been reading stackexchange for last 5 days but could not see any proper / answered circuit / discussion about Lipo battery charging and backup and thus asking the question here.

I am doing a circuit (GSM Modem Based) which eats around 50mA current for normal operation and a peak current of 1.6A (While GSM bursts).

I need a backup solution for the device. The circuit runs on 4V (Actually the GSM Modem can work within a voltage range of 3.6V to 4.4V. I am thinking to put a 700mAh Lipo as the power backup.

Now for the main power regulator of my circuit I have chosen LM2596 and for Lipo Charger I have made my mind to use TP4056 (for its damn low price). I know that there are specially designed power path management ICs from Texas Instruments, Microchips and other vendors, but they are costly. This circuit is a LOW COST challenge.

Can anyone guide me for a circuit for battery charging and power source switching?


texts: How to change analog sensor signal to appropriate levels for microcontrollers?

texts:
I have a FUTEK CSG110 amplifier, conditioning a signal provided from a load cell, providing a -3V to 3V signal. I can change this range to my liking, however I will be stuck with a +- voltage representing the compression and tension of the load cell.

I want to use the ADC of the Teensy 3.1 to measure this voltage, by modulate the sensor signal accordingly to provide 0 - 3.3V, the operating range of the ADC.

I was wondering how I can do this? I am sure there is a clever resistor configuration that will enable this.

Thanks,
Daniel


texts: If a 4-bit binary digit in 2's Complement form is stored in 8 bits how is it represented?

texts:
I am quite new to Digital Logic. I got this doubt while solving a problem.

If a 4 bit binary digit in 2's complement e.g. X3 X2 X1 X0 is stored in an 8 bit space what will be the representation in those 8 bits.

As far as i know, The MSB in 2's complement form is the sign bit.

So if e.g X3 X2 X1 X0 = 0 0 0 0 then X7 X6 X5 X4 X3 X2 X1 X0 = 0 0 0 0 0 0 0 0

if e.g X3 X2 X1 X0 = 1 1 0 1 then X7 X6 X5 X4 X3 X2 X1 X0 = 1 1 1 1 1 1 0 1

Could you generalize the way in which we will represent 4 bits in 2's complement to 8 bits?


texts:
Day after day, between 13:30 and 14:30, most frequently a few minutes after 14:00 we're getting power outages in our firm. One (random) or both of RCDs protecting circuits to whole wing of the building activates, switching running computers off, powering tested devices off, and so on.

We don't have any device to activate at that time, and the fact two different circuits are affected (and there doesn't seem to be any pattern which of the two, or both), suggests some external source. We sought an internal source (using a power strip with milliamp meter plugged into the ground line) and measuring leakage from different devices shows we're approaching rated leakage amperage of the RCDs, but still staying good 30% below the threshold (50mA).

Now, for more info:

Our firm is located practically under two high-voltage lines leading to a power substation barely some 200m away, supplying power to iron works - a massive industrial complex of roughly 10km^2, involving some extremely heavy industrial machinery. It seems 2PM is the end of the first shift in the iron works. I don't know how much these things can influence us, just giving them as possible avenues of research.

Can you suggest what can be done about that? What can be the source of such failures? Getting UPS for the whole firm would be rather expensive.


texts:
I'm designing a backplane that can be configured with different breakout boards (BoBs - example below of a simple pull-up type).  The backplane provides two different voltage rails (J2 and J3) and collects the BoBs' output signals (J1).

Since the footprint of the BoB is somewhat complex, I'd like to export it as a PCB footprint so I can accurately line up the connector locations on the backplane.  Is there a way to do this in KiCad 5?


texts: How can I repair lifted traces without a conductive pen?

texts: I've recently lifted a trace (first time in 2 years) on a board in a PC power supply. What is the best way to repair this issue and similar issues (consumer PCBs) without something like a conductive pen or other special tools (eyelets etc.)?


texts:
Is it possible to read a set of frequencies with a PIC in such a way that for each frequency a different function is called?

The idea was to send multiple frequencies at different times (no overlapping or super positioning) over one carrier and reading them on the other end resulting in different outputs. I was hoping to avoid having to implement many band-pass filters to channel each frequency to a different pin allowing the PIC to distinguish between the inputs.

In the end there should be ~1000 different frequencies in the audible range, well distinguishable for a micro controller.

Thanks


texts:
I am doing some work with an STM32F4-Discovery board, and I am trying to get some simple usage out of the GPIO Pins.  However there is a weird problem I am having, that I don't know how to fix.

I am using IAR Embedded Workbench as my IDE, and for some reason the only GPIO Pins I seem to be able to enable are those on the B-Bus.  If I go to enable a pin on any of the other buses and go to set the pin high and low, the volt meter I have hooked up doesn't register anything.

Additionally, there are a few pins on the board that seem to be stuck at a high voltage, which seems weird to me.  Some pins were outputting ~3V before I had even enabled them, or set them high.  Are these pins broken?  Or is there a way to set them low?  Attempting to enable the GPIO Pin and setting it low has not worked for me, so I am unsure of what to do here.


texts:
I stumbled across this clock generator, and it is new to me.
I'd like to calculate its frequency (actually min and max, since there is a trimmer), but I don't know how to do, since similar oscillator looks simpler than this.

I tried to simulate this schematic, but it didn't work.


texts: Can I connect 2 standard 12V 2A wall adapters in series?

texts:
I live in the UK and I need a 24VDC power supply. They are very expensive.

Can I just use 2 cheap standard 240VAC - 12VDC wall adapters in series with no issues to achieve 24VDC?

For example, and so I'm clear, my phone charger is 240VAC - 5VDC 2 ampere, can I just wire 2 in series for 10VDC 2 ampere output?

If yes, my understanding is that it would give me the same current as the lowest current transformer and I should remove the earth wire from 1 wall plug so as to make sure the outputs are isolated.


texts: Arduino object sensing and remote control car's code not working

texts:
Following is the code that I am using in my car.  The car is supposed to first wait for signal from remote (wait until it cycles through code counting to 1000.) If no signal is received in those 1000 cycles then it will activate the autopilot.
The IR remote part and ultrasonic sensor part of code work properly seperately but in this code they don't work together.
What am I doing wrong?

#include <IRremote.h>
#define trigPin 13
#define echoPin 12
#define irPin 7
#define f 11
#define b 10
#define r 9
#define l 6
int count = 0;
IRrecv irrecv(irPin);
decode_results results;

void setup() {
pinMode(f,OUTPUT);
pinMode(b,OUTPUT);
pinMode(r,OUTPUT);
pinMode(l,OUTPUT);

Serial.begin(9600);
irrecv.enableIRIn();
}

void loop() {

if (irrecv.decode(&results) || count<1000) {
  Serial.println(results.value);
  count++;
  switch (results.value) {

     case 1904:           // button 2 FORDWARD
        forward();
        break;

     case 2800:           // button 4 LEFT
        left();
        break;

     case 1008:           // button 5 STOP
        Stop();
        break;

     case 752:            // button 6 RIGHT
        right();
        break;

     case 3952:           // button 8 BACK
        back();
        break;
        }
irrecv.resume();
}
else{
  autopilot();
    irrecv.resume();

}
}

void autopilot()

{ long duration, distance;

digitalWrite(trigPin, LOW);

delayMicroseconds(2);

digitalWrite(trigPin, HIGH);

delayMicroseconds(10);

digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);

distance = (duration/2) / 29.1;

if (distance < 100)

{ digitalWrite(f,LOW);
digitalWrite(b,LOW);
}

else {
digitalWrite(f,HIGH);
digitalWrite(b,LOW);
}
}

void forward()
{
    digitalWrite(f, HIGH);
    digitalWrite(b, LOW);
if(count>0){
    count=0;
}
}

void back()
{
     digitalWrite(f, LOW);
     digitalWrite(b, HIGH);
if(count>0){
    count=0;
    }
}

void left()
{
     digitalWrite(r, LOW);
     digitalWrite(l, HIGH);
    if(count>0){
    count=0;
    }
}

void right()
{
     digitalWrite(r, HIGH);
     digitalWrite(l, LOW);
        if(count>0){
    count=0;
    }
}

void Stop()
{
     digitalWrite(f, LOW);
     digitalWrite(b, LOW);
     digitalWrite(l, LOW);
     digitalWrite(r, LOW);
if(count>0){
count=0;
    }
}

Is there a way to make the board return to remote control part when signal is pressed again? In this code the board will never return to remote control part if it once activates autopilot.
So whole question in one line will be how to multitask with an Arduino Uno?


texts: Frequencies of current harmonics 1 phase diode bridge rectifier

texts: I was wondering what would be the frequency of the current harmonics at the input of a 1phase diode bridge rectifier. My believe is that it should be 60Hz for Is1, 180Hz for Is3, essentially every 60Hz for an odd component.


texts: Is it feasible to test microprocessor/microcontroller?

texts: What I can do if I want to test the microcontroller?


texts: No zeros, yet still affecting stability?

texts:
As far as im aware Poles affect the stability of a transfer function primarily, and is defined whether they stay within the unit circuit & are on the left side of the pole-zero plot. Zeros have no role in stability? For the following transfer function which is in a feedback loop (Using a step input):

$$G(s) = \frac{K*50}{s^4+15s^3+100s^2+250s}$$

When I change the value of 'K', if the value is too low the system over damps, if the value is too high the system becomes unstable and oscillates into oblivion. Why?

For Example, when K = 1

When K = 10

When K = 100


texts:
Where is photodiode in the CD/DVD drives?
What is his frequency response & sensetivity usuallY?

I am going to try laser data transfer, but finding decent photodiode is my weak point.


texts:
Description:
I have built a copper plating tank to plate circuit boards and am using a technique called Reverse Pulse Current plating to help aide in the copper plating process. What that involves is essentially flipping the current polarity of the anode/cathode at precise intervals, so I decided it would be beneficial to use an H-Bridge as my device of choice to reverse the polarity when necessary. In my circuit I control the IR2110 with an arduino and have it give a forward pulse (anode +, cathode -) of 240mS and a reverse pulse (anode -, cathode +) of 12mS.

This is the basic circuit I am using:
http://2.bp.blogspot.com/-dlEcbNapBZ0/UPvnk7y2MuI/AAAAAAAAAZ4/bfSogInXgj4/s1600/IR2110+-+3.png

However: Vcc is 20V and each high side mosfet Drain is connected to it's own power supply, not +300v.

Part of the process requires that there be a different current for each pulse. To set that, I opted to buy these voltage/current regulators listed below and have one power each of the Drains of the high side mosfets.

Power Supplies:
http://www.ebay.com/itm/5-Pcs-5A-Constant-Current-Voltage-LED-Driver-Charging-Module-Voltmeter-Ammeter-/221327545118

They are switch mode power supplies, not linear.

Problem:
When I connect this setup to my plating tank (which has next to zero resistance) I get a massive current draw of about 3A, despite setting a current limit through the switching power supplies to a max of 500mA. My mosfets get incredibly hot and my board I am trying to plate gets burned badly as a result of the very high current density. These switching power supplies regulate current through "fold-back voltage" which basically means the control chip regulates the voltage low enough to a point where the voltage level sustains the set current limit. I didn't think this would be a problem because my linear regulated power supplies employ the same technique, and I can connect them as separate supplies to the high side mosfet Drains and it will have no problems.

Question: What am I doing wrong by using the switching supplies vs. the linear ones? What is causing this massive current draw?


texts:
I know that those C2 and C3 are used to isolate DC from the input and output. Capacitors are always open to DC(w=0) and since the equivalent impedance of a capacitor can be expressed as 1/jwc in frequency domain, to get a low impedance(almost short circuit), I think to use a larger capacitance value like 100F. I know in reality 100F is not a so logical value for common capacitors, however, I use LTspice program and it is easy to use a 100F in a simulation. So I enter 100F for the values of C2 and C3. However, when I do that the results get creepy.

The Vout waveform for 100uF C2 and C3 is a nice sinusoidal wave with gain > 300 ( 620 mVpp nice looking sine wave ) .

But for 100F C2 and C3, the result is,

So, why is this the case? Why using a higher capacitance is not a better thing?

p.s : I hope they were called as "coupling" capacitors.


texts: Electrical saftey of metal panel-mount DC jacks

texts:
Context:
I have a robotic arm with a series of servo motors, that together draw up to 3A from my bench supply (depending on the load on the servos). To make it easier to transport the robot around, I've bought the recommended DC power supply from the manufacturer - which just looks like one of those standard laptop power supplies.

Now here's my issue:
The new power supply comes with a molex-to-coax cable. The molex plugs into the robot and the coax goes into the new power supply. The coax end is a metal panel-mount jack (!).

Should I worry about the fact that it's metal? I.e. when the servos are working hard, drawing a few amps - is an accidental brush of the jack going to throw me accross the room?

For clarity here's a link to the style of jack I've been given, any advice would be greatly appreciated.

http://minute-man.com/acatalog/Online_Catalog_Metal_Housing_207.html


texts: Difference between S-R flip flop and D flip flop

texts: What is the difference between a D flip flop and an SR flip flop?


texts: How do we decide to use a lag compensation versus a PI compensation?

texts: Although lag and PI compensation apparently have the same objective of improving the steady state response, how does one decide which one to use?


texts: calculate clock cycle of ripple Carry and lookahead adder

texts:
How would you find the number of clock cycles it takes to produce sum, the carry out, and overflow flag using ripple carry or lookahead adder.

Can someone please explain me how would we go on finding the clock cycles, thanks in advance.


texts:
I am trying to design af system using the XUF-208-256-TQ64 Xmos controller (https://www.xmos.com/download/XUF208-256-TQ64-Datasheet(1.16).pdf). The system should get an audio stream from USB, upsample and then output the stream as an I2S signal.

It is my first time designing a PCB for digital signals.

The schematic for the xmos implementation:

Y1 is a 24 MHz oscillator. Datasheet: https://www.mouser.dk/datasheet/2/94/C33xx-186.pdf

U14 is a voltage detector with time delay, for holding reset at startup. Datasheet: https://www.mouser.dk/datasheet/2/348/bd45xxg-e-746184.pdf

I am laying out a 4-layer PCB, and would like some comments if I have done something that might not work + some specific questions. The PCB looks like this:

No layers, just components:

Signal layer:

Ground plane:

3.3 V supply plane:

1 V supply plane:

My questions are:

1) On the datasheet for the Xmos it says that ecoupling capacitors should be as close to the IC as possible. How close would a minimum be? I have put the capacitors as close as I can, with tracks coming out, will this be enough?

2) On the datasheet for the Xmos it says that the USB-standard dictates a differential impedance of 90 Ohm between the lanes. I find it hard to find information on this, and I have not found any specific implementations of this. What is to be done, to have this, and is it even needed? Is it implemented in the IC?

3) On P. 72 the datasheet says that RST_N should be fast enough for USB timing. But RST_N is just a signal to hold the IC in reset, what does this have to do with USB timing?

4) The datasheet states that the clock signal should rise/fall monotonic. However I do not find this in this datasheet for oscillators. Should I just assume that the oscillator is usable?

5) Should the tracks for the xsys header be same length? The datasheet do not say anything about this.

6) The datasheet says that I should minimize the amount of vias around the IC. Do I have too many, and how could it be done differently? By using longer tracks to the surface mounted components?

7) The PLL filter should, according to the datasheet, be as close to the IC as possible. Is my filter close enough? This is basically the same as question 1, but is the requirements the same?

I know this is a lot. I have tried to read the datasheet as good as possible, but these questions still stands. I hope some of them may be answered.


texts:
My servo is classic SG90. I connected +5V and gnd correctly to a dc power supply. Then I connected output of a signal generator which generates 0-5 V pulses at 50Hz (checked by oscilloscope).

I know that the duty cycle determines the position of a servo motor. I can vary the duty cycle between %20 and %80 from the settings of the signal generator and I can observe that pulse is changing accordingly via the oscilloscope. However, servo does not responds. What am I missing?


texts:
I am doing project in which I want to perform read and write operation by using a capacitive touchscreen. What I know is I can trigger capacitive touch screen by:

By using electromagnet as I heard that some of stylus works by using magnet at its point so I think electromagnet should work.
By using capacitor: If I connect a capacitor's one end to vcc and other to a conductor plate then I think it will mimic the property of human finger and trigger touchscreen.

I want to use these system so I not need to make any physical changes. If I want screen to trigger then I can just charge capacitor or electromagnet.
I want to know that whether my theory is correct or not and if there is any suggestion for that then let me know.


texts: A huge number of buttons on a Raspberry Pi

texts:
I am working with a friend (he's got the vision, building the structure, I'm working on the electronics) on a large scale project that involves a grid of pictures illuminated by an LED at the push of a button. He plans on having 1000 pictures, each with their own buttons. I plan on running the whole project on a Raspberry Pi. The LEDs will go through SPI. I am having trouble figuring out how to connect and monitor such a large number of buttons (I've done LEDs a lot but have little experience with monitoring multiple inputs). I have figured a couple options and wonder which is best, if this is even feasible:

A number of keypad scanner ICs (like the TCA8418 or LM8330) connected to an I2C multiplexer connected to the RaspberryPi. I don't know if this would have a reasonable response time or if certain sections of the keyboard would be unresponsive while others were active.
Multiple smaller arduinos monitoring a small number of buttons feeding info back to the Pi. We would be able to handle more simultaneous presses, but it seems to be the priciest option.

Are either of these feasible options to run on a single RaspberryPi with good response times? Registering multiple presses is less important than having something that responds quickly with each individual press in this scenario.


texts: How to wire this linear Hall effect sensor

texts:
I want to measure alternating magnetic fields 50 Hz to 100kHz.
I have the Honeywell SS 495 A linear Hall effect sensor and have used it like in the circuit diagram:

.

I could successfully measure a voltage change when bringing a permanent magnet at the proximity of the SS 495 A.
But with various resistors at R1 (0, 1K, 10K, 100K, 1M) and various devices (switch mode power supply, magnetic power supply, fan) I couldn't measure any frequencies (FFT at my oscilloscope).

Have I wired something wrong?


texts: How to stop summing counter at exact value?

texts: I want to stop summing counter at 25 decimal or 19(hex output) value while it's  begin summing from 1 to 31(1F in hex).So how can I make it ?


texts: Electric motor will only start turning at lower voltages

texts:
I have a tiny DC motor directly connected to this power supply. The motor starts just fine when the supply is set to 4.5V. I can then change the voltage to 6V and it continues to run just fine. However, if I try to start the motor at 6V it only runs in pulses (for about 100 milliseconds once every second). Also, if the motor is running at 6V and I apply significant load, it begins pulsing until I lower the voltage. I'm guessing both cases are explained by the larger current required to start the motor at a higher voltage, and to keep it running under load.

I have a few questions:

What is actually happening to cause the pulses?  Is my power supply overloading then "resetting" once every second?
Is there something very simple I can add into the circuit to allow it to start at higher voltages (a momentary current spike)?
Is there something very simple I can add into the circuit, perhaps a better power supply, to allow it to run under sustained load (a constant current increase)?


texts: Avalanche breakdown voltage, how does it start?

texts:
I would like to learn about the avalanche effect. I understand what goes on in the avalance effect, but I can't understand how it starts.

For the avalanche effect to start, an electron (the first) must have enough energy to go to the depletion zone and knock the electron from the atom.

For me it is a little hard to understand. How did that electron get enough energy to do that?


texts:
I need to convert a ppm signal to something that my computer can understand through a USB.  (This is for an RC simulator cable.)
I have looked into Arduino based solutions but will need a Leonardo for a HID interface or something similar. This is something that I don't have and can't get easily.
I happen to have a USBasp from an old project and have found this article which hacks a USBasp to a ppm2usb which is what I want. This link has more information but I still don't understand.  In terms of the hack, it all looks simple, scratch out a trace and replace it (details in the link) however I have no idea how to upload the hex file to board and then how to get a ppm input into it. This is what I need help on.

is there a better way of doing this?

if not:

is my understanding of the hack correct?
how would I go about uploading the supplied hex file (see the first website) onto the hacked USBasp?
where would I plug in the ppm signal to the USBasp?

Any help would be greatly appreciated
Thanks in advance.


texts: How to add footprint to a schematic symbol from any PCB library in Altium

texts:
I created a PCB schematic symbol and a PCB footprint, both .SchLib and .PcbLib added to my projects and in "Installed libraries".
When I go to the schematic symbol, click "Add footprint" -> Browse, in the "Libraries" drop down (see image) only one PcbLib appears although I have several. If I go to my project tree and double click another PcbLib and come back, then it will appear on the list, but will again be the only item there.
So my question is, how does Altium choose which libraries appear in this list? Why do they appear only one by one in my case, am I doing something wrong or is this a known bug?
Thanks


texts: TIP31 (TIP120) as DC Motor driver compare to MOSFET

texts:
I'm trying to drive DC motor with PWM using PIC P16F1824. Some books suggest using TIP31/TIP120 as the driver.
So I have PWM output pin connected Base pin TIP31, the Emitter pin connected to Ground.
I have a LED, the positive pin connected to positive pin from the battery, and the negative pin from the LED connected to Collector pin TIP31.

For LED, it works fine. Using PWM, I could see different strengths on the LED.

BUT, when I connected the DC motor, I could only hear noise sound.
The Motor normally run with 200 mA. If I connect the battery directly to the motor, it works fine.

My battery current is 900mA (2 x AAA, 3V). I measured the PWM output from the IC is  5mA, and the current from the Collector pin is 50mA. One of the Motor pin connected to the battery positive pin(900 ma), and the other pin connected to the Collector pin.

My questions:

Why the Motor doesn't run, although it appears it has enough current?
What are the difference between NPN Transistor (TIP31) with MOSFET and Motor Driver?


texts: Can I use a 500mA fuse instead of a 315mA fuse?

texts: I have a guitar amp with a fuse on the power socket. It is a 250v 315mA slow blow fuse. My local electronic store only has a 500mA fuse. Can I use that or should I order a 315mA online?


texts: What does 100Ohm @ 100MHz exactly mean in ferrite beads?

texts:
I am trying to understand the parameters of ferrite beads and having trouble in understanding the impedance vs frequency parameter.

What does 100Ohm at 100MHz exactly mean? Does it mean that the bead will provide impedance of 100Ohm for frequencies in the 100MHz region (depending on its graph)?

I do understand that bead is highly resistive at higher frequencies.

Any help will be appreciable.


texts: Cool White LED bulbs: Are they "full-spectrum"?

texts:
I don't have much knowledge on LED lights and find the technology quite fascinating (yes, I know, it is not that new!)

I have read that in order to create "white" light, LEDs actually need to emit light from all spectrums.

My question(s):

How do LED light bulbs (cool white or warm) generate white light?
What would be the light spectrum for cool white LED light bulbs?
What would be the light spectrum for warm white LED light bulbs?

Thanks!

P.S. This is my first question here. If it should be forwarded to another SE site, please let me know!

P.P.S. I have done my research BEFORE asking but could not find a technically accurate answer.


texts: What is the pin mapping when we use an ADC in micro STM32F401?

texts:
If we wanted to capture continuous data and map it to a digital value we must use ADCs.

But there is a problem. If we set multiple pins as analog inputs, what are the channels corresponding to each pin in analog mode?

In the control registers, we don't have any pin that determines to capture on which pin and on which channel on ADC.

I read the reference manual but it says just configure some pin on a port in analog mode. But if we have multiple analog inputs and want to use multiple ADC channels, there are some difficulties with this and the mapping among analog input pins and ADC channels.


texts:
I was reading this (https://www.maximintegrated.com/en/design/technical-documents/tutorials/1/1080.html)

I'm wondering, how did they figure out that by switching the MSB capcacitor that it causes a shift of 1/2Vref voltage on the common terminal. Is there some general capacitive divider equation for this?


texts:
I'm currently using LTspice, and I have a problem with it "never" finishing calculating a certain circuit. When I say "never", I mean that it's still calculating an hour after it started, even though the review-time is less than two periods of the input sine.

In the program status field it says: "Stepping Source: 100% step size=6.8413e-005 N-R iterations: changes frequently between numbers spanning from 0 to 200 fill-ins: 4". It seems to be stuck at this point.

The circuit I'm talking about is this frequency doubler.

Does anybody know a solution to this problem? If there is no solution, can you suggest a program that will not get stuck like this?


texts: Which motor driver to use with a DC gear-box motor?

texts:
I have this motor (a "PMDC Spur Gear Motor/KGA25RP")

I am not sure if something like L298 will work with it since it is a DC gear-box motor. What kind of driver should I choose?


texts:
So i have some 10ųf capacitator s that  i think can withstands the maximum voltage and current input of 11.1V and 3amps but they are extremly small and the legs are really thin ,just kinda need the security to know that i can use them

im using it for a 3 phase motor


texts: Circuit design - please explain to me the usage of these capacitor and inductor

texts:
I am studying this circuit, but unable to understand why they put capacitor C30, C33, EC4, inductor L3 on their current place, and their value, i keep searching on google for decoupling capacitor, sound like related, but still can not understand

Please give me some explain or keywords/documents/books that i can read


texts: Transmission line with a resistor. What happens after a long time?

texts:
Ok so I'm analyzing a problem with a very simple lossless transmission line:

In my case $$R=20 \Omega$$ and I have to find the evolution of uL(t)

So I had no problem doing the first iterations.

I think I don't need to give much details but basically

$$u_L=u_i + u_r$$

where i and r means incident wave and reflected wave

I will constantly have:

$$u_i=U_0-u_r$$

$$u_r=\frac{R - R_{\omega}}{R + R_{\omega}}u_i$$

So I will have the following sequence

$$u_i=U_0=120V$$
$$u_r=-60V$$
$$u_L=60V$$

$$u_i=U_0=180V$$
$$u_r=-90V$$
$$u_L=90V$$

$$u_i=U_0=210V$$
$$u_r=-105V$$
$$u_L=105V$$

and so on and so forth.

I have no problem computing this iterations and I totally understand the phenomena of wave propagation in the transmission lines.

What I don't understand is when my book says that in infinite time u_L will become 120 V. Is it a general property? I mean, I think it makes sense: as time goes to infinity the output voltage will tend to be equal to the input voltage, like we would have in traditional circuit analysis. But I'm not sure if I can jump to this conclusion.

I also did the analysis with the limit cases of R=0 and R=infinity: with R=0 I would of course always have a zero voltage as it should be. While in the case of an open-circuit I constantly have the output voltage switching from 240 V and 0 V as time goes by (but the mean value is indeed 120 V).

Can someone explain me mathematically why the output voltage will tend to be equal to the input voltage when we have a finite value resistor (different than zero)? Thanks!


texts: How to make auto off functionality for an led lamp circuit with only transistor, capacitors, timer 555 chip?

texts:
The components I have are timer 555 chip, capacitors, and transitors. I want to create sleep functionality for a led lamp which consists of 6 leds in parallel and pnp, npn transistors.

I want this circuit to sleep of time interval of 10 minutes. I just want some recommendations because I have no idea where to start


texts: Transfer function of amplifier (exercise)

texts:
The transfer function of the following circuit is (I read A(s) on the solution of my professor):

$$A(s)=A_{CB} \frac{s \space \omega_{pC2}}{(s+\omega_{pC1})(s+\omega_{pC2})}$$

where Nevertheless is the pole of \$C_i\$ and \$A_{CB}\$ is the midband gain. Why there is the pole \$\omega_{pC2}\$ at numerator?

\$C_1=1\mu F\$ and \$C_2=100pF\$

\$\omega_{pC1}<\omega_{pC2}\$

Please show me where \$\omega_{pC2}\$ at numerator comes from. I applied the seen resistance method; this allows me to obtain \$\omega_{pC2}, \space \omega_{pC2}, \space A_{CB}\$. Given these 3 parameters, I want to write A(s) like A(s) above.

Thank you very much in advance.


texts: How can I go from prototype to commercial product?

texts:
I have made many designs that I would consider "professional grade", but in reality they are still just prototypes. I have used professional board fabs and professional population, but what I haven't had the ability to go through is actually turning that product into a commercial product.

What is needed in order to take the product across this large last step? I can think of obvious things like FCC/CE testing, case design, marketing, distributors, etc. but I am sure there are other things that aren't thought of until going through the process a time or two, as an engineer, what are these things that would come up?


texts: Considering: battery + terminal hardwired thru relay coil thru BJT back to - terminal

texts:
I want to make a circuit which uses a latching relay to disconnect a battery from its circuit, but it will still have a path through the relay's coil and the BJT used to switch it.  How significant to the battery is the BJT's leakage? (I would use the collector-emitter junction to control the coil current, and a resistor to the base to control the CE junction)

I couldn't (quickly) find a symbol for a latching relay, so I modified the one it had for just "relay".  The assumption implied in the schematic is that the BJT throws the relay to the upper contact and the momentary switch makes the lower contact close.
It might need a capacitor to make the armature reach the trip point before electrical contact is broken (i.e. if this is a problem I'm guessing a cap would be a way to solve it)
SECOND EDIT  Sorry about the bizarre appearance of grafting in the photos.  I wanted to show that a standard (yet heavy guage wire suitable for increased current flow) USB phone charging cable (needed to supply power to the Raspberry Pi) would not have to be modified to connect with my circuit.  The circuit is supposed to indicate 2 separate wires for + and - emerging from the inline connector's cable jacket.
When the answer to this question pointed out that the diodes which suppress the back-EMF spike (snubbers?)  were missing I noticed that the polarity of the "coils" was reversed as well.  I think (hope) this is now correct.
I have used latching relays before which had two coils per relay.  The datasheet said that this allowed for two options

Both coils could be used, so that one coil would throw the armature to one set of contacts, and the other coil would be for the other contacts (like SET and RESET?).  Each coil would have the same relative polarity so that the potential at one of the terminals marked with, say, a + symbol would be at the same potential as the other + terminal.  But it didn't matter what the absolute potential was because of their design which allowed the second option
Only one coil could could be used to both set and reset the armature which closed the contacts.  This was done by simply reversing the polarity of the current being delivered to energize the coil when changing the state of the contacts.  It didn't matter which coil was used when using the polarity reversal method.

(If I have been so awkward so as to give a "for dummies" presentation of this material, it's only because that's the only method at my disposal (which is dictated by my level of "expertise"!) ...  ;+D


texts: What is single and multi connection mode( AT+CIPMUX=0 or 1) in esp8266 AT commands

texts:
I was studying the AT commands to program atmega328p for the communication with esp8266. Now I am confused with the command AT+CIPMUX=0 or 1 , it explains that 1 for multiple connection, 0 for single connection.

I don't understand the single and multiple connection.
Actually, what is the difference between them?


texts:
I've wired a teledyne s24d40 ssr to a leviton 20 amp duplex outlet using a 12 gauge extension cord.

The load is a 1200 watt wagner heat gun and I'm using a 9v battery to test.

This is my first AC project and I'm trying to make sure I haven't done something incorrectly.

ext cord green ground wire -> outlet green earth terminal
ext cord neutral white wire -> outlet silver terminal
ext cord hot black wire -> ssr output terminal 1
ssr output terminal 2 -> outlet brass terminal
+/- wires to ssr control terminals

When the ssr is triggered and the heat gun power switch is set to high, everything works as expected.

However, when the ssr is triggered with the heat gun power switch set to low, the heat gun does not power on.

Can anyone explain what's going on? I need to use the heat gun in the low setting for this application.

I apologize if this is an ignorant question, I'm still learning :)

Thanks very much for your time.


texts:
We have the following exercise in the figure:

I understand the answer. Now my question is: what is the output going to be if we would put V=10sinwt on the input? Could you sketch it for me?


texts: What is small signal. And what is small signal equivalent circuit

texts:
I am very new in electronics. And this topic is bothering me.
I want to know what is small signal and how to draw a small signal equivalent of jfet with common source.


texts: I am trying to create a custom library part in Eagle and I am having trouble scripting vias.  I get an error saying that vias can only be created for boards. However I can manually place them with my mouse.


texts:
I was troubleshooting a circuit and found that a transistor BC547 is getting very hot and after a day or two it is completely burned out while keeping the circuit on continuously. Then i measured some voltages and currents around it and providing here. I also referred to datasheet of the transistor but couldn't solve the issue.
Vce = 10.2V,
Vcb = 9.5V,
Vbe = 0.7V,
Vc to gnd = 22.0V,
Ve to gnd = 12.1V,
Vb to gnd = 12.7V,
Ic = 20mA,
Ie = 20mA,
Ib = 6.3uA,
Here all the values are way below the max values. Then why is the transistor heating up. Do i need to check anything else. ANY HELP.


texts: Control strong DC motor with microcontroller

texts:
Could anyone explain to me what it takes to control a strong DC motor with e.g. an AVR?

For example if I have a 24V Motor with 5A or more. How can I build such a circuit? Especially if I want to change the direction that the motor is running (H bridge).


texts:
I’m making a USB powered device and that will need relatively large bypass capacitors and I’m worried about the inrush current to the caps.

Yes I know about the 10 uF inrush limit of the USB 2.0 spec, but the these larger capacitors will be charged after the initial inrush (power sequencing I think it’s called) so I guess it can handle higher current spikes by then.

But how much capacitance can I have without creating too big current spikes during charging of the capacitors?

(I already know about the TPS2141 USB power management IC but I hope I don’t need it)


texts: Is it safe to leave a capacitor between the + and - wires of a circuit, while the rest of the circuit is turned off?

texts:
Please bear with me, I am new to electronics so my question may be stupid, but I want to make sure that the system is safe and won't catch fire.
I am trying to use an A4988 driver to power a stepper motor. The system is currently working pretty well, the stepper motor is rotating when I tell it to, but I have a safety concern over the use of a capacitor in the circuit.
This is the A4988 driver https://www.amazon.co.uk/gp/product/B0793K9KF8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I've been following tutorials such as this one https://www.makerguides.com/a4988-stepper-motor-driver-arduino-tutorial/ and they all mentioned the capacitor between VMOT and GND.
Here's a diagram

The DC source in this picture is regular 12V adapter plugged into a wall socket.
The stepper motor and the A4988 driver are rarely used in the project and I am hoping to completely turn them off when I am not using them.
My questions are:

If I am not using the motor, is it safe to have the capacitor there while electricity still flows through the wires? Won't it create a short circuit?
When I am not using the motor, won't the capacitor draw power from the adapter? I'd like to minimize power consumption as much as possible. Especially since the motor will only be used 2-4 times a day tops. The answer provided here Is it acceptable to leave a capacitor across batteries even when turned off? makes me think that the capacitor will draw a little bit of power. I would like to eliminate this completely, if possible.
Should I just add a relay to this to cut the flow of electricity completely when I don't need it? If so, does it matter if I put it before the VMOT and the capacitor(point A in the diagram), or after the capacitor and the GND of the A4988 (point B in the diagram)?


texts: How resolve "logic" is an unknown type error in Vivado synthesis?

texts:
the verilog code at

output  logic           PIPE_PCLK;


texts:
I am currently using these motors and driving them off these drivers and an arduino uno, and alternatively trying to make them turn using the setup in step 6 (both with l298n and without) in this instructable. I have 4 motors and all are exhibiting the same behaviour.
Using the drivers, I just sent a constant PWM via PWM pin, and the motor would only spin at high values around 255, but even then only when I touch the motor does it start spinning. This spinning is then not even smooth, it pauses a bit every second or so and results in a sort of jittering. After a bit more, plugging the motors in it now just makes an increasingly louder whining noise, kind of like it's getting ready to take off but doesnt really spin. Code used here is just basic as below:
void setup () {

pinMode(9, OUTPUT);

}

void loop (){

analogWrite(9, 255);

}

Using the instructable setups, I've wired exactly the same way (wiring for l298N version is in step 10, wiring for discrete steps is just directly pwms to the motor), but the motors will not spin like theirs do (same poles and slots, 12n14p). Mine just jitters back and forth in tiny steps and looks like it's just twitching. Code used is exactly as at the end of 'step 6'.
Imgur album of issues


texts:
I am trying to build a high frequency (~ 5MHz) level shifter circuit. For this purpose, I designed a comparator circuit based on TI's THS3491.
The circuit schematic is shown below:

simulate this circuit – Schematic created using CircuitLab

The D, D_bar voltage levels are 3.3V.

The circuit is working well until the ground of the square waveform generator and the power supply circuit is kept different. As soon as I connect both the grounds, high frequency signals gets pulled up to a digital 1 (24V), at lower frequencies, i.e. below 500KHz, I am still able to receive a waveform (though not perfect).

I am not able to figure out the reason for the same. Any help would be appreciated.


texts: What is MOSFET gate drive capability and why do I care about it?

texts:
Someone told me that this circuit has "poor gate drive capability":

simulate this circuit – Schematic created using CircuitLab

What exactly does that mean? I tested it with an LED as a load for M1, and the microcontroller is able to turn it on and off just fine. Under what circumstances is poor drive capability a problem? How do I improve it?


texts:
A few years ago I had to design a board that uses the NXP LPC1769 MCU and had Ethernet connectivity. I was in need of a PHY chip and the LAN8720 was choosen.

During design however, I noticed that NXP in their development boards use an inverting buffer on the REFCLOCK signal (see here, U9). I searched the datasheet, but I couldn't really understand the reason for this inverter. Finally I decided to follow their advice and also use the inverter. The board worked perfectly, as many more following designs did.

Now we are migrating to the STM32F427 MCU, and again I need Ethernet connectivity. I plan to use again the LAN8720 PHY, but I am confused about whether I should invert the REFCLOCK signal again.

Since I didn't understand why it was needed in the first case, I am not sure what to look for now to ensure whether it is needed or not.

Why this inverter was used? Where one can find information on the datasheet about this? And most importantly how can I know whether I need it on the new design?

Note: Space is at a premium for my new design, so eliminating even such a small part will be beneficial. I wouldn't really like to add it to the design just for a trial-and-error approach, only to find out it needs bypassing...


texts: Moving a small pin up and down using <12v

texts:
Hobbyist here. I'd like to move a pin up and down using <12v. How can I do that.

I don't wanna do it the mechanical way as I have three of them. my first option is using a servo in vertical way and making it moving up and down.

UPDATE

The size of the pin is 2-1CM, I want to use arduino to connect it and manage it.


texts:
i'm currently working on a PCB for an 8x8x8 LED cube. The PCB layout in the current status you can find below:

The ATmega328P (16Mhz) will use SPI to send the needed data to four TLC5940 chips (12bit grey scale, 16 channel LED driver) and one TPIC6B595 (8 bit shift register). In order to get high enough FPS and still have enough CPU time for effects the SPI interface needs to run at 8 MHz.

I'm a little bit unsure about the correct layout to avoid problems like corrupted data.

Relevant layout parts for this questions:

A) SPI Data: From the ATmega SPI pin to the first TLC and then daisy chained via the next three TLCs to the TPIC (every trace ~2-3cm long)

B) SPI Clock: From the ATmega SPI Clock pin in two directions. Firstly to the corresponding ISP header and secondly under all the TLCs to the TPIC. Every TLC data clock pin is connected by a very short branch of the clock line. The line ends in the clock pin of the TPIC chip. (total line length ~23-25cm long without branches)

C) GS Clock: Needed to keep the grey scale PWM of the TLCs going. Via the set CKOUT fuse a constant 8Mhz signal is send via this line to all TLC greyscale clock pins (~20cm long without branches).

D) Blank: From ATmega to all TLCs, ending in the last one. Usually GND level, toggled regularly to reset PWM counter in TLCs. During data update for the TLCs it is high for the first few transmitted bytes and then set low again while the rest of the bytes is shifted out (to reduce LED downtime)

E) Latch: From ATmega connected to all TLCs and the TPIC chip. Always low except for a quick toggle (when SPI is not active)

F) PCB Layers: Red lines top, blue lines bottom. The bottom has additionally a complete ground fill, as seen in the magnification of one TLC:

My questions regarding the data transmission layout:

1) Is it ok to route those lines over ~14cm in parallel? Blank und latch ("calm lines") are in the middle and the "noisy" lines GS Clock and SPI clock on the outside (0.05 inch distance between each line), but therefore close to IC pins.

2) Are the short 90° branches ok to connect every IC to the data lines or will this create problems?

3) What about signal reflection/termination (for SPI and GS clock)? I've read several articles about that topic but did not really understand all of it. Some people claim that at 8Mhz there is no problem. Others differentiate between trance length and so on. Some solutions like end line termination apparently are only working for a single load, therefore this will not work for me obviously. So far I haven't found anything concrete/clear regarding this topic. I feel like this could be a dealbreaker for my board at the moment.

4) What about the signal return path? I tried to make it possible for the return current to follow the relevant top trace on the bottom layer, but a few obstacles remain (like the connections of the GS clock, latch and blank traces to the PLC pins). Is the layout in this respect still ok?

Best regards,

ratuso


texts: Finding a thin conductive, non-magnetic material

texts:
I want to find the thinnest possible material, so it lets through most of the 30 kHz magnetic field, but is also good for use as a terminal for an "air" capacitor. The material should have the highest as possible permitivity so that the capacitance is as big as possible and as low as possible magnetic permeability so that the eddy losses are small as possible because of reduced skin effect.

I need a material sheet or spray to then make as small as possible layer (order of one micron). What material to use and where to actually get it. It would be best to be easily obtainable. This is going to be used in the end in mass production so the focus should be on price as well. But for now it's just for predevelopment.


texts: Solar Cell to DC-DC converter to Li-Ion charing module, is the DC-DC converter necessary?

texts:
I have the following components:

1W Solar Cell (5V at 200mA): http://www.ebay.ca/itm/291435192356
DC-DC Converter (2.5V Vin_min, set to 5V Vout): http://www.ebay.ca/itm/200983543561
5V Lithium Ion Charger (with protection): http://www.ebay.ca/itm/400665520672

I'm thinking of connecting them like this: Solar Cell -> Converter -> Charger -> Li-Ion Battery. The reason being is that the converter will keep a constant 5V into the charger, which will charge the battery. My questions:

Why can't I remove the converter if I'm willing to accept inconsistent charging? It will also avoid any power usage that existed across the converter.
If I take another solar cell and connect in parallel to the first, will I get 5V, 400mA?

[EDIT] My constraints:

Using it indoors, will get some sunlight, varies between 3-5V (maybe more on a really sunny day), but a lot of the time will be crappy fluorescent light.
Will trade consistency with efficiency i.e. It doesn't have to be on all the time, but when it's on, I'd like it to power the charging module properly, and charge the li-ion battery.
The converter seems to boost to 5V for inputs less than 5V, but if input is over 5V, then output of converter will NOT clamp to 5V and actually rise with input.


texts:
I'd like to do some experiments with a traveling magnetic field. To start with, I'd like to create a traveling magnetic field with a set of coils and try to propel an aluminum sheet. A basic model of a Linear Induction Motor.
Like this experiment: https://www.youtube.com/watch?v=PAAfFgyWvB4 (t=10:10).
I am wondering to what kind of power supply these coils are connected? 3-phase AC?


texts: Why does armature current increase when load on the DC motor increase?

texts: Does this load somehow decrease the resistance of the armature causing it to draw more current? Is it due to the torque the load will give to the motor?


texts: I was stuck while studying schottky contacts. If we are using metal and a doped semiconductor, we get depletion region inside semiconductor since it has either donors or acceptors ions. As we goes on decreasing the doping concentration, we get more efficient rectifying contact. But what will be the scenario with undoped semiconductors. Undoped (intrinsic) semiconductor do not have any impurity ions, so we cannot show depletion region inside them. And if we can't, then how will the metal-intrinsic picture will look like?


texts: When to use Star ground vs ground plane for audio circuits?

texts:
I have designed a 4 layer board for a DIY DJ mixer I'm building. The 4 layers are:

Connectors. Some traces going to/from components to Molex connectors.
Power plane.
Ground Plane.
Signal plane.

The circuit is designed using dual power supply essentially creating +12V, virtual ground, -12V. The virtual ground is all connected through the ground plane.

I have noticed that the part of the circuit that uses op-amps, specifically the TL072, seems to be ok.

The headphone part of the circuit which uses 2 LM386, is susceptible to oscillations and distortion. I.e: When I touch my case or event pots or components on the PCB, the op-amp circuit seems fine, no distortion, the sound plays clean. The headphone section though goes crazy.

I have attached my KiCad PCB project. Just wondering if I should continue to use ground plane, switch to star ground or use both, ground plane for the op-amps and star ground for the headphones amplifiers?

Or do I have serious design issue?

https://www.dropbox.com/s/shabj2at0fffa25/main-v5.zip?dl=0

The images are in the order that they where described above.


texts: Can BME280 sensor's output be converted to 1-wire Protocol

texts:
Teltonika FMB125 is an advanced GPS Tracking device with 1-Wire interface to monitor temperature data. I tested a waterproofed version of the DS18B20 Temperature sensor with Teltonika FMB125 and I got the temperature reading successfully. As I am using the sensor to read the temperature of a freezer vehicle which keeps the temperature at -35 ~ -25 Degree Celcius, the performance of DS18B20 Temperature sensor is not satisfactory. I want to connect a BME280 Temperature Sensor to Teltonika FMB125, but BME280 doesn't come with 1-wire support. Is there any way to convert BME280 sensor's output to 1-wire Protocol so that it can be used with Teltonika FMB125?
Thanks in advance.


texts: Do I need a crystal to for the Atmel SAM D20 MCU to Run at 48 MHz?

texts:
I am working on a very small device and would like to use the Atmel SAM D20 as MCU (this variant ATSAMD20E16).

Reading the data sheet, there is only one point I do not find clearly spelled out:

Do I need a crystal to run this MCU at 48 MHz?

I found, there are various internal clock sources. Also the feature list states "Internal and external clock options with 48 MHz Digital Frequency
Locked Loop". But interestingly every existing design I checked had an crystal added to the board.

For my device, the clock can be imprecise.


texts:
There seem to be about 4 major flavors of transistors, and then there are NPN/PNP versions. There are also relays, SCRs, and TRIACs.

When I need an microcontroller-controlled switch, what rules of thumb should guide me in choosing? Are there a few common ones that people like to keep around for use when there are no particular high-performance specs?

I'd like to learn the general rules so I don't end up googling 37 variants of the same question.

For a concrete example, the application I am choosing for right now involves driving a 5 V, 160 mA (80 mA average at 50% duty cycle), 3.1 kHz buzzer with an output from a 3.3V MCU that can sink 8 mA or source 4 mA.


texts: calculating input resistance of darlington pair (TIP120) from datasheet values

texts:
I've tried to find a way to calculate the input resistance of a darlington pair (TIP120), using the values given in the datasheets.

https://www.onsemi.com/pub/Collateral/TIP120-D.PDF

After Searching for a while, i was only able to find solutions for discrete darlingtons,(these required knowing parameters for each transistor (like the hfe,hie that are missing in tip120 datasheet).

I need this parameter to perform the calculations concerning the AC Analysis of this circuit (T1 is the darlington):

How do I find Hfe and Hfi for this circuit?


texts: So when you derive the Bode Plot from the transfer function you plug jw into the transfer function H(s).  You then get the magnitude of H(jw) and plot it to get the Bode Plot.  My question is why does this work?  My book simply tells me to plug in jw into the equation without giving me any intuition on why I need to do so.


texts:
I'm trying to power a Raspi from a Power Supply but I would like to switch it on and off depending on if the USB out from the TV is on or off (the USB from TV is not needed for anything except signaling if TV is on or off).

Prinicpally the TV could power the Raspi but that's just beyond the normal USB power specs, so I'd like a safer solution but keep the on/off logic tied to the TV as the Raspi is useful only with TV on.

Is there something like that out there? How could it be done? TIA!


texts: I2C Slave ACK not driving down sufficiently

texts:
My I2C slave is not pulling down the bus all the way for the ACK.

I have tried replacing 1.5k pullup with 10k pullup, but the ACK voltage remains the same (1.6V).

System Voltage: 2.5V

Master: STM32L151

Slave: NXP NT3H211

I have confirmed that the NT3H2211 is recognizing its address, because when I send another address (0x56 instead of 0x55), I see no response. (See screenshot).

I have confirmed that the NT3H2211 has a good ground and power supply, stable during the I2C access.

I have also ruled out an I2C peripheral issue on the master by writing a bit-bang rutine with the same result.

In this situation, how to proceed?


texts: How do I change the output voltage of the LM7805?

texts:
I read in the LM7805 datasheet that I can change the output voltage to not only 5 V, but to another value by changing the circuit resistance. How do I do that?

From what I understand, to change the output voltage I saw this picture:

However, I can't find the values of R1 and R2 in the datasheet. How do I calculate them?


texts:
Its my very first question here and I am very new to circuits.

I have an LED with USB connect port that turns On when connected to my PC. I want to make a circuit and turn it On/Off using some programming language like C#.

I am a C# developer and want to use my skills with electronic hardware.

I'll really appreciate your response and guidance on this. I am a beginner so need to understand from basic level that how I can achieve my goal.


texts: switching shape memory valves with microcontroller using NPN transistors

texts:
I am using a standard NPN transistor-as-a-switch set-up to use a Teensy 4.0 to switch a bunch of shape memory valves (valves controlled by a wire that changes shape when heated by a current). I have previously got some advice here on the use of a buck converter set-up to run this, but this did not work out well so I decided to go this simpler route and accept the ~0.35W power waste in the 8.2 Ohm resistor (2W type).

simulate this circuit – Schematic created using CircuitLab
When I connected the "Teensy DIO" point directly to the 3.3V DC power source, the transistor switches fine, giving the desired .25A current required to the SMV. When I instead set the Teensy DIO to High as in the circuit, I only get a 0.05A current, and the voltage at the Teensy channel is only .8V, with a current flow from the Teensy at 0.5mA. when disconnected from the circuit the channel goes to 3.3V when set to high, so the Teensy seems fine. Does anyone know why this set-up does not work?
Thanks in advance!


texts:
Using two 74F189 parts, implement 16x8 bit RAM circuit.

Using two 74F189 parts and decoder, implement 32x4 bit RAM circuit.

Using four 74F189 parts and decoder, implement 32x8 bit RAM circuit.

Not sure where to start with the decoder. The circuit is simple enough to avoid using one and instead using an inverter, however this is not an acceptable solution.


texts: I need to make a bunch of thermocouples but I don't want to spend a ton buying them pre-made. I only need short thermocouples (like 6-8" long) so if i were to buy them it would be wasting a lot of wire too. I know thermocouple wire is pretty cheap but I don't have a good way of connecting the ends. I need to measure temps about 200C so regular solder won't do. I don't have a welder either. Is there any other good way of connecting the ends? Would JB weld work or would that mess up the reading. What about a high temperature epoxy? Can the wire ends be twisted together or can they only touch in one place at the tip?


texts: Can a 12V 7AH@ C20 battery support a motor having load variations form 1-10 Amps?

texts:
I want to know what is the significance of C5, C10, C20 rated  7AH Battery to drive a varying load 12V DC Motor. Is it possible for a C20 Battery to power the motor for atleast 20Mins or so if the motor takes a load of 5-10Amps. Or is it like 7/20A is the max load capacity for C20 7AH battery.
Thanks for any useful information


texts: SLA battery constantly being charged and used

texts:
I have a 12V 7Ah SLA battery with a smart battery charger for SLA batteries with the maximal output of 0.8A.

I would like to use the battery to charge an Arduino board with few other things (at most 0.5A current consumption). Several times a day, the battery must be used for few seconds to power a motor (which takes few amps).

The battery must be contantly used for powering the board. Is it safe to charge and use the battery constantly? Is it a standard use case, can't it reduce its lifetime?


texts: Is capacitor noise due to observed step charging?

texts:
According to Tom Bearden and Per Wallander the capacitor step charges and step discharges. Se for example Per Wallander, My way of understanding
electromagnetism, section 2.3 page 13:

  What we see on the oscilloscope is a staircase produced by the signal which is reflected
  at the far end, total reflection, but also being rereflected at the generator end
  according to the reflection coefficient.

This stepwise measured behaviour differes from the smooth exponential curve that we have been taught that capacitor charge changes follow. I wonder how this difference is percieved?

The design practice to parallel connect capacitors of different sizes to minimize noise also support the idea that capacitor noise is due to stepwise voltage change.

Is this effect included in what is called capacitor noise?

Since people misunderstand this question I repeat that it is the observed step wise voltage change in the capacitor I am referring to.


texts: PWM motor control - weird voltage ringing issue

texts:
I'm having some issues with a specific 24V brushed DC motor I'm PWM controlling.
I'm seeing some rather nasty voltage spikes and ringing on every PWM on and off cycle.

All scope measurements are made with a differential probe across the motor at DO19+ and DO19-

At first I thought it was the internal diodes of the MOSFETs that couldn't handle the inductive spike, so I added another flyback diode directly across the motor - no difference.

Then I tried replacing the 0 Ohm gate resistors with 50 Ohm resistors to slow down the on/off time of the MOSFETs - no difference. (Maybe 50 Ohms was a bit on the low side?)

So I tried a different 24V brushed DC motor (no detailed data on this motor unfortunately) very similar to the first one, except this one had a lower gear ratio - so less resistance:

Everything looks great, so I'm slightly confused and left wondering what to do about the first motor?

Any hardware changes that I can make so the first motor will look as good as the 2nd motor?

UPDATE!

After removing the ferrite beads FB3 + FB4 it looks a lot better. I think Marko is on to something regarding the LC resonance.


texts: What is the rate at which a mobile/cell phone listens for an incoming call or a text in standby mode?

texts: As I understand, a mobile/cell phone, in the standby mode, listens to some kind of circular buffer in its memory for acquired packets from the antenna to check if there's something that regards installed SIM card. What is the rate at which the CPU fetches and checks the packets if there's anything (an incoming call, a text message) that's been sent for the installed SIM card?


texts:
Can I say that in UART shift registers -

UART Tx uses  Parallel in Serial Out Shift registers - My reasoning is that we are writing complete byte but it will transmit bit by bit.  True or False?

UART Rx uses Serial in Parallel out shift registers - My reasoning is that we are receiving data in Serial but we will read data in parallel i.e. after 1 byte.  True or False?


texts:
I have a question with respect to altium and polygons. I have used altium just for a week and i am not sure of how to analyze this issue.

I have created 2 polygons using a signal layer in altium and connected it VDD and VSS. Using this polygon plane which in the properties i connect to respective VDD and VSS nets, i tap the VDD and VSS connections to the IC's on the board.

please check the layout snapshot of the VDD and VSS planes below

Also the properties of the VDD polygon:

Now, what i dont understand is, why are the VDD and VSS taps into the polygon "etched" and not a SOLID connection to the polygon.

Similar issue occurs to the GND plane one layer below.

When i run the DRC i receive errors "Net Antennae Violations" on these nets. and also show up in the "Un-routed" net constraints. (These erros i assume are showing because of the non solid connection to the polygons).

Any inputs would be appreciated.

Thanks!


texts: I simply wish to check the voltage of my RC plane Li-po battery under a simulated load. The battery voltage is 8 V. The usual current draw from the four servos is around 1 A. Could you please tell me the size of the resistor I would need to hook up to this battery so I can check its charge level under load?


texts: I'm trying to rewire an arcade game, and I need one button (a simple microswitch hooked up to the coin acceptor) to have a longer press than a coin passing by provides.  I'm not sure exactly how long a press the software is looking for, but what would I need to wire in to lengthen the pulse?  A capacitor, or maybe a retriggerable multivibrator?  I'm a total novice, as you can see.


texts:
So to the background of my question, there has been a rumor around that Apple might use Intel's fab to manufacture their A4 or A5 chips as they no longer source them from Samsung. The article then goes on to state that Apple might then benefit from Intel's knowledge of a 22nm process and that would mean some power savings for them, giving them a quite a large amount of power savings over their current 45 nm process.

So my questions is in two parts; How much power saving does a die shrink offer all things being equal and Is there a mathematical formula for this for calculating the power consumption as a function of process size?

The last thing I would like to add, that is more conjecture then anything else, because we just don't know; that is, until Intel releases a product using their 3D transistor platform; how much benefit do 3D transistors add to the overall power efficacy of the chip?


texts: LED driver putting out more voltage than rated?

texts:
The Background

I bought a 200W magnetic LED driver with hopes of replacing the 40W Philips-supplied driver that came with my set of Hue Lily outdoor lights. Each fixture requires 8W at 24v. This new driver should allow me to add about 25 fixtures, instead of 5...

The (unexpected) Problem

I wired up the driver and tested the output with my multimeter: 24.1v. Perfect, so I brought it outside and hooked it up to the 5 already-installed fixtures. Nothing happened

Back inside, I retested the output and sure enough, it was 24v. This time, I intercepted the voltage in-line while I plugged in ONE fixture... A flash, and then nothing. The multimeter was now reading 38v!!

Why would a driver rated for constant voltage suddenly jump and destroy my fixtures?


texts:
Question : An infinitely long, very thin cylindrical conducting tube of radius b carries a uniform surface current Js = azJs(A/m). Find B everywhere.
When r<b, it says that "In  condition flux density of cylindrical conducting tube is 0 because the cylindrical tube has no internal surface. So when the  condition the flux density  is 0."
: Why there is no internal surface?


texts:
I have a problem where my 485 transceiver just get damaged at field, when it's at laboratory everything runs fine, now reading about it I saw that 485 requires a 120Ohm impedance on both ends and bias resistor, what I used was 120Ohm on each drop and 4k7 pull-up on A, 4k7 pull-down on B on every drop. We use 2 transceiver MAX485 and Texas' SN75176, both are getting damaged, when I change transceiver, the communication doesn't happen.
I need some advices about resistors, good quality transceivers, etc.
Edit:
We use a 4 pin connection, 5V, GND, A,B, while 5V isn't connected. There's a common gnd between them. Also, for protection we use two 5,6V Zener at A and B, but normally on web searchs I see they using TVS.
Schematic
The BUS is a PCB that only carries A,B,GND and 5V, there's a connector at the end and it's not connected, only connected when I want to probe what is being transmitted.
My power supply is a 5V/3A flyback SMPS. The field condition is a aluminium "crate" which my PCBs are in, sometimes we use a PC too. It's stay at sun and rain 24/7.


texts: Can the bytes that make a word be handled individually?

texts: In word-addressable machines, fixed point numbers are naturally handled word-wise by the CPU. This means that any integer is stored in word-sized memory cells and that you have to access a whole word to read or write a single integer. But how about smaller data units as characters, commonly encoded as 8-bits data pieces? Since a word is made of multiple bytes, is the CPU capable of storing multiple characters in a single word while handling them as individual data pieces? For instance, if I store 4 characters (encoded with an 8-bits scheme) in a 32-bits long word, can the CPU understand them as a set with 4 elements? Or it is necessary to store a single character into a whole word? Is there a standard or different architectures deal with this matter differently?


texts: Circuit explanation, role of the trimpot and capacitor, as shown in a part of the circuit

texts:
Here is a part of the IOIO circuit

.

Wondering if someone could explain the role played by the trimpot (R2) there (why not a fixed resistor?) and the role of the capacitor (C5).


texts: Is there a simple way to transform an analog signal into its first derivative?

texts: I have an analog signal in the range 0.5 ~ 4.5 V. I'm less interested in the signal's absolute value than I am in its rate of change. Is there a relatively simple passive circuit that I can put between the signal and an ADC that will do this? Is it as simple as throwing in a capacitor? The input range of the ADC is 0 ~ 3 V.


texts: What are real world examples of using op-amp as voltage adder, subtracter and an averaging amplifier

texts:
While trying to understand about op-amps, most tutorials show how op-amps can be used as adder, subtracter and an averaging amplifier. However none of the tutorials gives any real world examples for those type of circuits.

Could you please give some real world examples for using op-amp as adder, subtracter and an averaging amplifier?

Specifically, why do we need to add up voltages? or subtract? or need to find average?


texts:
So I finally Dived into understanding the P-N Junction and Field Effect Transistors. (this may almost be teetering on the "Physics portion" of electronics, but it's still mainly for understanding the Field Effect....

This video (Which I hope was correct) really made it feel so simple or easier to understand.
http://www.youtube.com/watch?v=CLLcRRBph90  (Just for reference, don't really have to watch it)

Anyways from What I understood, 2 Semiconducting Material (P being Positively charged and containing "holes" and N being Negatively charged (Extra Electrons) from whatever they were "doped" with. When a Positive current is applied it makes the Electrons "Jump" into the Holes, this causes current to flow (The free electrons in the N junction, jump into the P Junction).

Anyways I have a few questions.

What exactly "causes" the electrons to jump into the Holes? and What exactly is happening when the electrons attach to the holes? are they immediatly unseated...or do new ones take their place or what? I understand the "holes" concept but im not sure I understand what happens when current is flowing. Do these electrons from the N Region go into the hole of a P region and then continue to flow, do they stay there? do they discharge someone else?

The Depletion Region

So if you reverse bias a PN junction it causes electrons to go from the P region to the N region, causing a Depletion Region. First of all, does the P region have ANY electrons in it at all.... or is it doped to have absolutely zero (and therefore any free electrons are coming from your ground/- source (Battery/etc...) and therefore just filled with Holes?

And what exactly is "In" the depletion region? Just nothing...floating electrons? I understand the concept of a Depletion region, but im not sure I understand "Why" one forms when reverse Biasing a PN junction. The more voltage you apply the bigger the depletion region becomes, but is this because more electrons are getting shoved into the N region where they have no "holes" so they just "float around"? and cause a Neutral zone of sorts (or an insulator)? How comes they don't just bypass the N region....since it's technically still a conductive material? (Or do "some" actually still do..like a Reverse Biased diode will leak a little bit won't it?)

Also sidequestion: The PN Junction is obviously pretty important..but besides the fact were able to control the flow of electrons using the Depletion Region, and reverse biasing and such...is there any other "special" qualities that aren't talked about? Since Even Transistors almost seem like a Diode, and that seems to be the basis of the PN junction.

Sorry if this is borderlining Physics im just trying to nail down the PN junction into terms I can understand. (Although if anyone knows of any Physics books that go into detail on the PN Junction and Semiconductors/Electronics Physics I would appreciate it)


texts: Can anybody tell me why the amplitude goes down by half?

texts:
Can anybody tell me what I need to do to this circuit to keep the gain at 0dB until 23kHz to 25kHz?

The gain goes to -6dB. I want the gain to remain at 0dB until it's 23kHz to 25kHz, that's when I want the cut-off to start.


texts: Controlling a DC Motor 48v with a 63v power supply

texts:
I have a 1000w 48v DC motor and some Lipo batteries 15s (one 6s and three 3s). My batteries full-charged has 63v (4.2v * 13s).

If I control the speed of my motor through a PWM (using my arduino), I guess I can set the max duty cycle to never reach a tension higher than 48v.

Is that the best way to do it? Thanks!


texts: Review this solar-powered weather station schematic?

texts:
It's my first time designing a schematic in EDA (or at all really) and I'd love a review of this schematic to point out any silly general circuit mistakes I might be making. Not looking to dive into functionality, but any general EE considerations (pushbutton circuits, placements of resistors/caps, proper wiring of grounds) that I might have missed since I don't have a formal EE background.
For context: the project is a solar-powered RasPi system with a pushbutton/e-ink interface which controls motor-actuated valves.
[Edited per comments to clean up wiring:]

Also hope this schematic might be useful to anyone building solar-powered RPi stuff.
(Edit) Datasheets:

MCP23017 i2c I/O expander
Ag103 solar charge circuit
TB6612FNG quad half-bridge
SPI e-ink display


texts: CPU Memory Hierarchy: Calculating Average Memory Access Time

texts:
(From Schuam's Outlines Computer Architecture, 2002, page 193, problem 8.7(b))

Suppose I have the following memory hierarchy of:

CPU <-> SRAM <=> DRAM <=> DISK

SRAM  has 5 ns access time

DRAM  has 60 ns access time

DISK  has 7 ms access time.

If the hit rate at each level of memory hierarchy is 80% (Except the last level of DISK which is 100% hit rate), what is the average memory access time from the CPU?

So I start the problem... here are my calculations:

For the DRAM Level the access time is:

$$
T_{DRAM} = (0.8)(60 ns) + (0.2)(7 ms)
$$

$$
T_{DRAM} = 1.448 \mu seconds
$$

For the SRAM/CPU Level the access time is:

$$
T_{SRAM} = (0.8)(5 ns) + (0.2)(1.448 \mu s)
$$

$$
T_{SRAM} = 293.6 ns
$$

Now for the problem,  the solution manual for the book says the answer is:

$$
T_{SRAM} = (0.80)(5 ns) + (0.20)(0.80)(60 ns) + (0.20)(7 ms)
$$

which I calculate to be: 1.4136E-6 seconds and they calculate to be:

$$
T_{SRAM} = 280,0136.6 ns
$$

My answer is "293.6 ns", and the book's solution to the problem is "280,0136.6 ns"

Who is right and why?


texts:
I have two active low async resets (rst_na and rst_nb) and associated two clocks (clk_a and clk_b). Assume Block B required effect of rst_nb and rst_na.

There are two options as far as I know to have synchronized rstsync_nb:

1) ANDed two reset and then sync'd

2) Both resets are sync'd , ANDed and again sync'd

General guideline is to use reset which is not output from combinatorial logic because it is glitch prone.

To have glitch free sync'zer scheme which option is better for combining multiple resets?

Any other mechanism?

Edit : Reset Synchronizer


texts: Why is component spread a figure of merit for analog filters design?

texts:
Sometimes I read that in analog filter design, component spread is a figure of merit. The lower the better.

What is the advantage (or disadvantage) of having a low (high) component spread?

The only limit I see for components value, is that an actual component with that value must exist. But I don't see how component spread could affect this. What's there to consider?

Note: I consider component spread as \$ C_{max}/C_{min} \$ where \$C_{max}\$ is the maximum value of the capacitors in the filter, while \$C_{min}\$ is the minimum value. The same goes for resistors and inductors. I'm not sure if any mixed component spread may be meaningful.

EDIT1

From the comments/answers I would like to precise that:

I've got passive filters in mind, like an LC ladder structure or any other standard implementation;
You can neglect any loading effects on the load or any effects of the source connected to the filter.
We can just consider any transfer function (i.e. something independent from the source and the load) and then, among the many implementations of the same transfer function, the filter with the lower component spread (defined as above) is the best one. (of course, there are many other figures of merits in a filter, but we want to limit the analysis to this one).

This is how I interpreted the fact that component spread is a figure of merit in filters, but I don't understand the disadvantages of having it high.


texts: What is the actual ratings of this limit switch?

texts:
I'm going to use this microswitches as the limit cut off for motorized locking system for sliding door of my store room under the stair case.

Upon checking it properly, the Indonesian made Omron switch marked with three different voltage ratings and current ratings. Im my application the switches will be handling about 2Amps peak at 24V. All the markings are above these thus I will not having trouble using these switches but still I'm very much confused what exactly the specs are for this units.


texts:
I read a white paper earlier on that implied that Passive Beacons were on the horizon (which I will accept could mean 10 years away).

My head's spinning thinking about the applications of mixing active and passive beacons, and I have a lot of thoughts on what they might have actually meant, or what research could be going on, but I'm honestly not even remotely experienced enough in electronics or RF to be able to decide whether or not I should be excited.

In your experience/with your educated opinion, would you say this is actually a possibility?

EDIT/UPDATE:
My question is - Are Passive BLE Beacons a possibility for commercial users within the next 5-10 years?


texts:
I have this circuit:

simulate this circuit – Schematic created using CircuitLab

The idea is that a high at Vcharge will charge the capacitor and then a high at Vdischarge will discharge it. However, a high at Vcharge creates about 3.22V across the capacitor, which then discharges as soon as Vcharge goes low again. Why is this happening?


texts: What limits physical size of capacitors and inductors becoming really small?

texts: For same capacitance C or same inductance L, one wishes to shirink the physical size of capacitors and inductors (by whatever methods - shrinking down the size of wire, etc.). What limits size becoming small? Planck length limitation is obvious, so I am asking other sources of limitations.


texts: How to talk with RTC hardware by Python?

texts:
I am using DT6 custom board from Variscite . This board is connect with DART MX6 board. DT6 in below link

http://www.variscite.com/products/single-board-computers/dt6customboard

I need to handle the RTC hardware on DT6 board by Python. This RTC named ISL12057. I google some info and I understand as follows.

ISL12057 is same as DS1307. There is a library of Python for DS1307 as link

http://www.switchdoc.com/2014/07/python-driver-ds1307-real-time-clock

I try this Python library, but I do not understand this library well. So I have some questions as below. Could you answer them? I appreciate your support.

As I list in /dev/, it has i2c-0, i2c-1, i2c-2. I do not know which I2C that connect to my RTC. I tried 3 of them by smbus.SMBus(0), smbus.SMBus(1), smbus.SMBus(2), there are 2 kinds of error.

1.1 IOError: [Errno 16] Device or resource busy

1.2 IOError: [Errno 5] Input/output error

So, firstly, how can I solve 1.1 or 1.2 to talk with my RTC?

I have no experience with Python that can talk with RTC hardware. So, if my usage of DS1307 library for my ISL12057 is not correct, could you tell me another way?
ISL12057 has an interrupt function at each second or each minute. In Python, can we detect that interrupt when it is asserted?


texts: Line-of-Sight method of simple code transmitting for outdoors

texts: I'm trying to determine the best way to do this. Basically I'm trying to design a system that would transmit a signal containing a simple code to allow the receiver to identify the source device. It needs to work only with line of sight. Like laser-tag. My first thought was IR, but I'm worried that this would not perform well in sunlight. Whatever the system uses must be able to work in direct sunlight, and must be able to run on common batteries. Any advice would be great.


texts:
I'm trying to understand how binary addition works.
If I understand it correctly, with two variables e.g. x and y you add a third one called c_i. On the other side, you add the sum and c_o.

The rules as far as I understood them: If you have two 1's, you carry 1 out and the result is 0.

Here is what confuses me:

1) In normal addition, you would carry in the 1 you carry out to the next line. Why don't we do this here, and therefore, what happens to the carry outs?

2) why is the carry in an "input" of its own, shouldn't it be just x and y since the carry ins/outs usually belong to one operation distinct from the values we use?

Thanks in advance!!


texts:
I have one of these charging this battery but it's taking forever. Is the below diagram a good idea or is it dangerous/a better way.

(also please feel free to criticize my diagram. I am trying to learn this on my own and could use the help)

The Charger Specs

https://www.sparkfun.com/products/10401

enter image description here

The Battery Specs

http://www.ebay.com/itm/New-Internal-Battery-replacement-dajn-fit-for-iPad-1st-gen-/231044587897


texts: How do I prevent backfeed through contactors when joining 3 x 230v ac circuits all single / same phase

texts:
I am working on a project to safely combine separate power circuits into one. Its to do with using available power instead of renting mobile generators.
The problem is that the 'magic box' has various safety devises that are being hampered by backfeed- as when one supply is cut the eg. contactors remain fed through bacfeed from the other circuits. If it was DC we would , i think be talking diodes, but its ac 230v.
I have looked at SSR relays but it seems although no back-feed current will flow there is still a potential voltage present and this is enough to keep the relays/contactors open. I have also looked at using RCD devices to detect some kind of in-balance but the back-feed seems to be balanced through it's own neutral.
I have used DP double pole MCB's to provide overcurrent protection but also to offer a higher degree of isolation. I did try running two lives through the DP MCB's and using one feed for the coil. This worked, in that the O.C. devices in the magic box would activate the contactors. But I still have the problem that one of the supplies can be cut outside the magic box with no activation of a contactor.

My Objective is that if one supply is cut off - all supplies will separate.

:Please edit your question to explain your requirements. (1) Are multiple supplies on and connected at the same time? (2) Do you want just one supply on at any time? (3) What is your intended sequence of operation? (4) Is it to be fully automatic?

YES multiple supplies are on and connected at the same time.
NO I do not want just one supply on at any time.
Sequence of operation: 1. Plug in 3 x trailing leads from magic box to 3 x 13amp supply 1ph. Flip trip switches in the magic box to energise 1x 32amp 1ph supply trailing lead from magic box.
Yes once energised the safety should be fully automatic.

Thanks
Niall


texts: A way to make temporary connections to battery holders?

texts:
I often need to make connections to these types of battery holders. For example, to power it from an external power supply, and/or to measure current draw in various modes of operation.

I can use my hands to hold probes to the battery-holder terminals, but then I can't push buttons on the device or adjust the multimeter. Alligator clips can't grab onto the flat surface of the positive terminal.

Is there a way to make temporary hands-free connections to these types of battery holders without soldering?


texts: How to reduce audio noise from Bluetooth module

texts:
I assembled a "Portable Bluetooth Speaker" with of the shelf Bluetooth/MP3 module and tiny stereo amplifier (supposedly 10W per channel) plus battery pack. Both devices need 12 volt.
When they are connected to independent power supplies (either different batteries or power adapters) the sound is perfectly clear. But when connected to the same supply, the module seems to inject noise trough the power leads, which is picked by the amp.
I connected a headphone in series with a 10uF capacitor to the power input of the module and sure enough, the noise was heard. By noise I mean clicks and ticks, like an old modem or the sounds some speakers make when a cell phone receives a call nearby. When connecting the headphone directly to the module's output, the music is heard faintly but the noise is not noticeable, that's why I guess this noise is produced in the power input side of the circuit.
What alternatives do I have to reduce or minimize noise while feeding both components from a single battery?
I tried connecting some capacitors in parallel with the module with the hopes that the noise would pass through them and thus "short circuit" while leaving the DC alone but that did nothing. (tried several values 10uF, 4.7uF, 2.2uF, None of them seemed to even reduce the noise level)
For this particular BT/MP3 module, when using USB the noise is very low and almost inaudible at mid to high volume (The amp has it's own volume control), but when using BlueTooth the noise is so loud that it renders the whole thing unbearable.
The construction is as simple as can be:

Side-dish question: Why does this happen and why some combinations do not suffer from this? why these modules seem to inject noise from digital operation into the power rail?
For example, using another module type, I have 3 of them and installed one in my car, one in a boombox and one in a small 4-AA Battery powered active speaker. The three modules are the same "model". (The cheap 10 Dollar ones from China).
In the Boombox I had the same "digital noise" (repeating ticks and clicks that vary when I change modes on the module or skip tracks, etc). It disappeared if the module has powered from a separate source. I was feeding the audio through the volume control potentiometer, as the boombox has no "line in", but the sound was clear if I connected a cell phone or the same module but powered separately.
In the car I connect it through the head unit's "aux in" and the digital noise is audible but so faint that at normal listening volume plus road noise is not noticeable, however, I have to use one specific 12v to 5v adapter (a phone charger) because any other, either branded or generic, introduces "alternator whine" (I call it that because the pitch rises when engine RPM increases).
In the 4AA battery operated speaker, using essentially the same schematic as above, the sound is perfectly clear in any of the modes of the module, it does not show the problem at all!
The goal of my question is to achieve more enjoyable sound in my hobbyist audio projects and learn electronics concepts in the process.


texts: Quiescent current vs GND pin current for Linear Regulator IC power dissipation

texts:
I want to confirm that, for a linear regulator IC, quiescent current multiplied by the input voltage accounts for the IC power dissipation(including drop-out voltage loss).

I ask because the datasheets for some of the linear regulators say that this loss is calculated by the GND pin current multiplied by the input voltage. This is found in the thermal considerations section.

While I initial thought of them as the same thing, the datasheets have different values and curves for each.

I'm doing a stress analysis on the linear regulator and want the total power loss of the IC, so which current is definitively used for the IC device dissipation; quiescent current or GND pin current?

Note: I've already calculated the power dissipation from the drop out voltage. I just want the device dissipation.

Some datasheets I was referring to:

https://www.analog.com/media/en/technical-documentation/data-sheets/3012fd.pdf

https://www.analog.com/media/en/technical-documentation/data-sheets/1761sff.pdf


texts: How to build a Schmitt trigger using transistors?

texts:
I understand that Schmitt trigger is a comparator circuit with hystersis and that it is used to convert signals from analog to digital and to remove noise from a signal using positive feed back. However how it actually works is confusing and to further understand it I decided to build one myself.

I decided to make a circuit with a power source of \$V_{cc} = 8.5V\$ that switchs on an LED when the input voltage \$V_{in}\$ exceeds the high threshold of \$V_{HT} = 7.5V\$ and switchs it back off when it goes below the low threshold of \$V_{LT} = 3V\$, I used a potentiometer as a voltage divider to control the input voltage. I used the following schematics:

simulate this circuit – Schematic created using CircuitLab

To determin the resistor values I set the quiesent current to \$I_E = 1 mA\$ when Q1 is off and Q2 is on, therefore:
$$R_E = \frac{V_{HT}}{I_E} = \frac{7.5}{1 \times 10^{-3}} = 7.5 k\Omega$$
$$R_{C2} = \frac{V_{CC} - V_{HT}}{I_E} = \frac{8.5 - 7.5}{10^{-3}} = 1 k\Omega$$
When Q1 switches on and Q2 switches off, the emitter current changes and therefore:
$$I_E = \dfrac{V_{LT}}{R_E} = \dfrac{3}{7.5 \times 10^3} = 0.4 mA$$
$$R_{C1} = \frac{V_{CC} - V_{LT}}{I_E} = \frac{ 8.5 - 3}{0.4 \times 10^{-3}} = 13.75 k\Omega$$
Now I wans't sure how to calculate R1, R2 so I assumed that \$V_{B2}\$ is equal to the high threshold and using the voltage divider between \$R_{C1} + R1\$ and \$R2\$:
$$ V_{HT} = \dfrac{R2}{R_{C1} + R1 + R2} \quad V_{CC}$$
I chose R1 to be equal to \$1 k\Omega\$ so:
$$R1 = 1k\Omega \Rightarrow R2 = 15k\Omega$$

However when I tested the circuit it didn't work at all and the LED was constantly on regardless of the input voltage. Why is it not working as it should be?


texts:
I have 20 pieces  3v 0.5w 150mA 5730 smd led chips and a 3.7v 2600mAh li-ion battery.
I want connect 20 pieces led s in parallel and use the battery as a power source. Thus I decide to make an emergency bulb. Using 5ohm resistor in every connection.
How efficient it will be? ? Or is there any problem? ?