texts: Induction Motor Power Factor with Variable Speed Drive

texts:
I know something about pumps, but less about the motors which drive them and am looking for some help in this regard.

The motor in question is a three phase two pole squirrel cage induction motor. I am trying to calculate the power output from the motor based on the supplied current and voltage. To perform this calculation one of the things I need to know is the power factor. The manufacturer has supplied various performance characteristics of the motor including a graph of power factor vs. percentage name plate load (load factor) which I can use. However, I believe the power factor data is specifically for a drive frequency of 60 Hz and, with this in mind, I have two questions please:

1) Given that my motor is connected to a variable speed drive, is the plot of power factor vs. load factor for 60 Hz still valid at other frequencies? Or, to put it another way, is the power factor of a motor running at its name plate load constant with regards to frequency?

2) If the answer to question #1 is 'No' is there a recognised method to correct the power factor curve to other frequencies or is it something which needs to be determined experimentally?

Any words of wisdom would be greatly appreciated.


texts: How Much Current Is available in Series-Connected Batteries?

texts: If 3 fully charged (3.7V(nom), 2.9Ah) li-ion batteries (rated for 2A max per cell), were placed in series to form a 3S battery pack, how much current could a maximum load draw from the battery without causing damage to the cells?  2A or 6A?


texts: Delay doesn't work (avr attiny 26, delay.h)

texts:
I am trying to learn how to write programs to microcontroller, and started with very simple things like LED blinking with given frequency, or controlled by button.
However, I have problems with using _delay_ms() from delay.h. As fas as I understood, for the correct work of this function, optimization should be turned on. When I write program to the microcontroller, instead of LED blinking, LED is constantly turned on with low brightness. When I tried just turn it on without delays, brightness is much higher, so looks like for some reason microcontroller gives some intermidiate low voltage, I am wondering why and what could be the problem. Below I describe what exactly I was doing.
Code (main.c) looks like this (I am using attiny26, and asssume that it works at 1MHz).

#define F_CPU 1000000UL // 1 MHz clock speed
#include <avr/io.h>
#include <util/delay.h>
int main(void)
{
     DDRA |= (1<<PA0);  //A0 as output
     while(1) //infinite loop
     {
          PORTA |= (1<<PA0);// LED at A0 ON
          _delay_ms(1000); // 1 second delay
          PORTA &= ~(1<<PA0); //LED at A0 OFF
          _delay_ms(1000); // 1 second delay
          }
 }

I make object file with

avr-gcc -mmcu=attiny26 -O1 -c main.c

where -O1 is for level 1 of optimization. Then

avr-objcopy -O ihex main.o main.hex

and write to microcontroller:

sudo avrdude -c usbasp -p t26 -B 100 -U flash:w:main.hex:i

All the steps were completely without any errors or warnings. As I told above, resulting behaviour is weird: LED is constantly on with lith low brightness. Meanwhile, if I write to microcontroller program, where I just turn LED on (remove all the delays), LED will be turned on with full brightness. I was thinking if the optimization itself can be a problem, but in the regime without delays program works correctly in cany case - with optimization or without.

Controlling anything with button would require debouncing, and the same _delay_ms() function, which doesn't work for me.

UPD: Commenting out #define F_CPU 1000000UL or increasing argument of _delay_ms() doesn't help. But increasing delay time by making iteration for (i=0; i<100000; i++) {_delay_ms(1000);} leads to LED being constantly turned on with full brightness. Tested smaller times of iteration (10, 100, 1000, 10000) do not give full brightness of LED.


texts:
This is from my textbook talking about the advantages of a common gate amplifier. The author says that the common-gate stage is usually superior to that of the common-source stage for two reasons.

However, what makes me confused is about the second reason. The low input impedance is only an advantage when the input source is a current signal.

So with low input impedance the common gate is only better than the common source when the input source is a current signal. When the input source is a voltage signal, the common source is better.

Do you agree with this?


texts: RC circuit with two voltage sources and finding I(t)

texts:
I would like some guidance on this problem that I have:

This is the circuit:

And the question is:

Note: typo in the question, closes should be closed.

So my take on the question is:

There is two cases, one t<0 and one t=0. In order for me to find I1 I'm thinking that I need to calculate Vc. So when t<0 the switch has been closed for a long time and the capacitor should act like an open circuit, like this:

So I'm having a bit of a difficulty to go on because of the two voltage sources. In my mind I'm thinking that when the capacitor acts like an open circuit then VA should not be considered. However I won't be able to calculate Vc by only having VB, R2 and R1.

So my difficulty is what happens when the switch is closed. How am I supposed to find I1 when the switch is closed?

Any suggestions would be kind!


texts: Implement a speed controller for a cascaded position controller

texts:
I have here a motor with a magnetic encoder, which has 2^14 bit resolution. It is connected to an stm32f3, that I use for position control of the motor. Now, normally the P position controller uses as a second stage a PI velocity controller and as a third stage a PI current controller. I have some problems with this structure, since when I try to feed the position controller to the speed controller, the system seems not to be stabilizable, but when I directly feed the position control signal to the current loop, it is pretty stable.

Now how should I process with the speed controller? First of all I need an accurate measurement of my velocity, but this is not possible with this reoslution for very slow speeds, right? Especially since there is also noise on the sensor. Since this control structure is usally used for a PMSM servo motor, I ask here, how the velocity should be taken into account?


texts: Are fuse wires in air tightly sealed heat shrink tubes safe?

texts:
i've seen a few Videos now, where people use fuse wire as single cell protection layer for parallel battery packs to protect against catastrophic failure due short circuit of a defective cell.
Often these battery packs are sealed with heat shrink tube resulting in these fuse wires to be (more or less) air tightly sealed.
Is that safe? Will those trigger even without air?
My understanding is, that fuse wires will act as a circuit breaker by simply burning through, which seems difficult without air?
Thanks for your time.


texts: Random number generation with skewed distribution

texts:
I would like to implement a fully-digital circuit that can generate a random variable X with P(1)=p, P(0)=1-p (where, ideally, the probability p would be configurable with a programmable parameter).

An LFSR is useful for pseudo-random number generation and for getting a random variable in which probabilities to be at 0 or 1 are (almost) equal: this is not what I am looking for.

The ideas I was thinking about:

I could 'AND' the outputs of several LFSRs, but given that in my application p will often be <0.1, the number of required LFSRs would be unpractical.
I could also try to add a comparator and compare the contents of the LFSR to some configurable threshold to get the probability p. But given that an LFSR 'shifts' its contents, wouldn't the successive outputs of the comparator be too similar or predictable? I am unfamiliar with these concepts, so I am not sure.

I need the successive values of the generated random variable to be as independent as possible, but it is not a problem if the pattern of successive values is cyclic in the very long term (as for any LFSR output). Thank you in advance for any improvement of the above ideas or any totally different idea that could solve my problem.

EDIT - A microcontroller is out of the scope of this question for two reasons:

This implementation targets an ASIC
I am limited in resources and I might have to instantiate this circuit a couple of times, a µC is just overkilling
this has to be high-speed random number generation (a µC would would require several clock cycles)


texts: Is it possible to physically destroy a microcontroller with software?

texts:
Assumptions:

No external circuitry connected (other than the programming circuit, which we assume to be correct).
uC is not faulty.
By destroying I mean releasing the blue smoke of death, not bricking it in software.
It's a "normal" uC. Not some very weird 1-in-a-million very purpose specific device.

Has anyone ever seen something like that happen? How is it possible?

Background:

A speaker of a meetup I assisted to said it was possible (and not even that hard) to do this, and some other people agreed with him. I have never seen this happen, and when I asked them how it was possible, I didn't get a real answer. I'm really curious now, and I'd love to get some feedback.


texts: Adjustable Clock Generator between 15.5 MHz and 17.4 MHz

texts:
I'm looking for an inexpensive component to generate frequencies between 15.5 MHz and 17.5 MHz. My intention is a medium-run product (a few hundred units).

The issue is that I would like to change the frequency during operation and the change should not take more than 1 us. The control part will be performed by some kind of microprocessor.

It would be big advantage if the chip I'm looking for could simultaneously generate other frequencies which would be a division of the current main frequency and phase shifted.

I have thought about using an FPGA, but I don't have any experience with it, so I don't know what to look for.


texts: Choosing an inductor for a synchronised interleaved buck converter

texts:
I'm designing a 10 W buck converter. The input is around 18V, and the output is 12V at .6A (considering converter losses which I wouldn't include here). I used this tutorial to guide me through choosing an inductor. The inductor equation is $$L= \frac{(Vin-Vout)Vout}{VinFsw*(LIR)*Ioutmax}= \frac{(18-12)12}{18*15KHz*.3*.6A}=1.48mH$$
where LIR is the Inductor current ratio and it's .3.
$$\Delta Il = LIR*Ioutmax= .3*.6=.18A$$
$$Ipeak= Ioutmax + \Delta Il/2=.6+.18/2=.69A$$
The tutorial instructs to follow the inductance calculated to make a selection and make sure that the saturation-current rating is higher than the calculated peak current(in this case .69A).
With this in mind, I go to this supplier. I can see a 1.5 mH inductor, as I went through the datasheet questions came up. The saturation-current rating for the 1.5 mH inductor has 3 different sections, which "specify the DC current that causes the specified inductance drop from its value without current". What does that mean? Also I noticed these inductors are tested at a 100KHz frequency as opposed to my 15KHz selection. Does that make a difference? I have already ordered the 1.5 mH inductor, is it possible to utilize it by changing the frequency (maybe choose 100KHz)? I know increasing the frequency would decrease the inductor size, and don't know if this inductor selection would end up being to big (I made calculation and found the value to be .285mH at 100 KHz). Considering that I have 2 interleaved Buck converters, I'm assuming the current would be halved across both. Would that give me more head room on the saturation current limit?

Update: I've tried this out, and Used the 1.5 mH inductor, the RFS1317-155KL. I used an of the shelf 100uF 100v electrolyte Cap.  I got this waveform for the Vgs of the MOSFETs, the upper one is for the higher side.

I got this waveform for the dead time

I have used the Half Bridge Driver: IRS2003(S)PbF.

MOSFET used: IRL60B216

As I increase the input at 18V from 0V. The waveforms above sag downwards. At 2V it exceeds the current protection limit of the supply and automatically turn of the supply. what could be wrong?


texts:
I've needed to use a second power supply and been given this one by a friend, and I don't really understand how to use it fully. I also have a couple basic questions on use.

It has two screens, and I only understand the right half, which is the output current and voltage. Can anyone explain the left half?
Secondly, with the configuration i've connected it, measuring with a multimeter across + and Com shows 4.089V compared to + and - which shows 4.12V, why is this?
Thirdly when doing standard things like supplying a voltage to a circuit is it better do connect + to Com or -?

Thanks


texts:
Does the logic inside flash memory devices require a power down after each WRITE operation?

I was confused when reading the datasheet of the Micron Serial NOR Flash Memory.
There is "To avoid data corruption and inadvertent WRITE operations during power-up, a poweron reset circuit is included... ".

After WRITE operations (program or erase sector) to the Micron Serial NOR Flash Memory, it does not respond to any instruction during power-up except READ STATUS REGISTER, I have reset the circuit and the device remains in lock mode. I have to power down the chip to get correct values (previously written) back from the EPCQL.


texts: Does using multiple speakers degrade quality?

texts:
I have an amp and 4 speakers. I want to "daisy chain" the speakers together like so:

I'm trying to figure out if doing series and/or parallel connections in the diagram above will degrade the sound quality/volume/anything else when compared to a single speaker. It's a pretty simple question, but I haven't managed to find any similar questions out there (maybe I'm using the wrong terminology?)

I understand the concepts of Ohm's law and all how to balance the impedance. This question is not asking about that.


texts: cause of half voltage on microcontroller reset pin

texts:
I have an AT89C4051 micro (powered with 5VDC) in which the reset pin is pulled down via a 100K resistor (formerly 39K) and pulled up via a 4.7uF tantalum capacitor. For simplicity, let's say a normally-open button is added in parallel with the capacitor even though one isn't there.

I hooked the positive lead of a voltmeter to the reset pin and grounded the negative lead of the voltmeter.

When I hold down the button, the results that were expected appeared (around 4.9VDC), however, when I let go of it, the voltage stays at about 2.6V. I was expecting the meter to slowly count down to 0V but it doesn't unless I remove a voltmeter lead from the circuit.

The only thing I could think of is that the insides of the capacitor are somehow broken, but I can't tell from the outside since nothing blew up on the board. I did measure the resistance across the capacitor and the meter stayed at -1 which suggested to me that no short circuit (yet) exists in the capacitor.

What can I do to correct this issue?


texts: Design of an amplifier with emitter degeneration

texts:
I'm trying to solve a question that says to find \$gm\$ and \$R_c\$, considering a gain of 50 using a BC547b transistor. But I can't find a way to calculate these parameters with the information I have. Could someone help me?
The BC547 model:

*PVDB
*DATABOOK PHILIPS
.MODEL BC547B NPN (BF=530 NE=1.3 ISE=9.72F IKF=80M IS=20F VAF=50V

BR=10 NC=2 ISC=47P IKR=12M VAR=10
RB=280 RE=1 RC=40 TR=.3U
CJE=12P VJE=.48 MJE=0.5 CJC=6P VJC=.7 MJC=.33 TF=.5N)

So, because of that I'm considering Va = 50V, Is = 20e-15 and Beta = 530. Right?
The circuit of this question:


texts: What is the voltage drop across each open switch in series connection?

texts:
The excerpt below is from Multi-level conversion: High voltage choppers and voltage-source inverters by T.A. MEYNARD, H. FOCH.

Question:

From the figure, how do you know that the voltage drop across each switch is E/2?
For realistic model, every switch has parasitic capacitance between its terminal (and maybe finite open switch resistance). So the voltage drop across each switch is E/2.
Do you agree with this explanation?

Now let's assume that the switch is ideal (no parasitic capacitance, infinite open-switch resistance), what is the voltage drop across each switch? Is it still E/2?

  INTRODUCTION  In the field of High Voltage Power Conversion, the circuit designer is often confronted to a serious problem: there
  are no semiconductors capable of sustaining the desired voltage
  (traction application for example). For this reason, circuit designers
  proposed several converter topologies in which only a fraction of the
  voltage is applied to each switch.

  SERIES CONNECTION OF SEMlCONDUCTORS

  The first solution involves series connection of several switches
  controlled in synchronism, thus obtaining the equivalent of a high
  voltage switch (Fig. 1).


texts:
I'm currently trying to test some old NVSRAMs
to make sure they work before I put them to use. Id like to test them independently and I'm thinking a arduino might do the trick. In theory, should a arduino mega be able to handle this?

PORTC = DQ0-DQ7
PORTA = A0-A7

            #define E           2
        #define G           3
        #define W           4

        void fillOne();

        void setup() {

          Serial.begin(9600);
          pinMode(E, OUTPUT);
          pinMode(G, OUTPUT);
          pinMode(W, OUTPUT);

          DDRA = B11111111; // sets port a to output
          DDRC = B11111111; // set port c to output

          digitalWrite(E, HIGH);
          digitalWrite(G, HIGH);
          digitalWrite(W, HIGH);

         }

        void loop() {

        fillOne();

        }

        //Test One

        void fillOne()
        {
          int fail = 0;
          int address = 0;

          PORTC = B11111111; // Sets Dataline to one

           Serial.print("Test Start");
          for (address = 0; address < 256; address++)
          {
            PORTA = address;
            digitalWrite(W, LOW);
            digitalWrite(E, LOW);
            digitalWrite(W, HIGH);
          }

          //Read Back and check for One

           // Sets Datalines to one

         digitalWrite(W, HIGH);
          digitalWrite(E, HIGH);

          PORTC = 0x00;
          DDRC = 0x00;

        for(address = 0; address < 256; address++)
        {
          PORTA = address;

          digitalWrite(G, LOW);
          digitalWrite(E, LOW);

          if(PORTC != B11111111)
          fail ++;

          digitalWrite(G, HIGH);

        }

        if(fail > 0)
        {
        Serial.print("FAIL");
        Serial.print(fail);

        while(1);
        }

        Serial.print("PASS");
         while(1);

        }

Update: I set it up to only use A0-A7 until I get it working, then will expand to other bits. I'm also only programming it with 1's so it's easier to debug for now. It's not quite working, I think it's the addressing.. I have Address set to a INT and it's going from 0 to 256.. If I send the int to a PORT, it should send out that number in binary, correct?


texts: Where does branch circuit neutral current go in a single phase or three phase electrical panel?

texts: Specifically, I would like to know the exact path of travel for the neutral current when it comes back from a load to the electrical panel. I am an electrician of 20 years and have recently acquired information that challenges the way I was taught. Does branch circuit neutral current immediately return to the center tap of the pole transformer via the neutral bus in the panel? Or does it find its way to back to its source via the other phase that it would be 180' out of phase with? There is a lot of conflicting information about this on the internet and I am hoping someone on this site can help me.


texts: ESP8266 GPIO2 - invert logic NPN transisotr

texts:
I make big mistake in my design. I connect output to ESP8266 GPIO2 at this pin I got base of NPN transistor to control LED.

I test it on breadboard but probably by noise or "universe magic floating voltage" there was no problem with boot. I make PCBs but of course now ESP wont boot because it need to be HIGH on GPIO2 to boot from flash. So I need add pullup to D4 (it is no problem) but how I can invert logic of NPN or replace it with something different without manufacture whole new PCB ? Thanks guys.


texts:
I'm learning basics of electronics and trying to get familiar with the common emitter topology. This is my schematic diagram:

When I try to simulate it in Kicad I get this:

Everything works as I expect except the fact that "base" is 0.4V higher than "in". How this can be explained?
UPD. It looks like the voltage shift is not constant. If I change the capacitor and the resistor this way:

Thrn the voltages become equal soon:

It leaves me with question why these voltages differ by 0.4V initially? Is it something specific to ngspice?


texts:
FSK Modulation in VHDL

Hello,
 I have a VHDL block that performs FSK modulation. It looks like this

The operation of the VHDL block goes like this. Fsk_data selects Fsk_u or Fsk_l depending upon its bit value( either 0 or 1). The Logik block decides which bit of fsk_data to be used to set this multiplexer. What I need to do is to implement the counter function for this Logik block that increases with every clock cycle and when reached the maximum value will start again with zero.

The architecture of my VHDL code is as follows:

signal cnt_s    : std_logic_vector(21 downto 0);
signal temp_s   : std_logic_vector(7 downto 0);
begin

process(reset_n_i, clk_128meg_i,cnt_s)

begin

if(reset_n_i='0') then
    cnt_s <= (others=>'0');
elsif (clk_128meg_i'event and clk_128meg_i ='1') then
    if(enable_i='1') then
        cnt_s <= std_logic_vector(unsigned(cnt_s)+1);

But, after this I don't have any idea how to proceed. My point is that I need to point the next address of the fsk_data register using the cnt_s (cnt_s acts as a pointer here) in order to select either fsk_u or fsk_l. I need to know whether my point is right. Help is appreciated in proceeding this code.


texts: What is (phase lock loop)PLL?, Lock Range & Capture Range?

texts:
The explanation of a PLL is here, for a PLL, what is the meaning of the following terms?

Capture Range ?
Lock Range ?

What is it about the PLL circuit that might have these two terms span a different range.  Or are they always the same?


texts:
Im having an issue with TP4056 Lithium  Charger Module. Connected the battery 3.7v 150mah battery. When charging the red led is on but it never shuts off and no charge state is reached even after 1-2h of charging.
Also when load is connected (digispark) to output it will not power it. If I connect the module like I was to charge the battery with 5V it starts. I then disconnect the power and digispark is then powered via battery. Its like it needs a small boost to start up the protection circuit for the battery on the  module to allow it to pass current through.

Any ideas ? Thanks


texts: Differential Input to Single Ended Output with Fully Differential Amplifier?

texts:
I am using LT1994 Fully Differential Input/Output Amplifier for a single-input to differential output configuration with no problem. I need to use same amplifier for differential input to single-output configuration as tried in LTSpice simulation. This seems to work (attenuates input signal) but draws excessive current for this IC (~86mA). Seems to be a problem.

How can I achieve normal current levels?

Am I doing wrong by trying to get single-point output from a fully differential amplifier?


texts: Detecting which pins are inputs or outputs

texts:
I have an idea to make a device with a generic ZIF socket which can be used to identify any chip you place into it and once identified run a suite of tests to verify that the chip is functional. I hope to target most of the 74xx line of ICs.

My idea is basically connect each pin of the socket to an IO pin on my MCU. 74xx series chips shouldn't draw enough current that I can't power them from a decent I/O port, so odd power pin arrangements or differing pin counts shouldn't be a problem.. For simple chips it should be fairly trivial to drive the input pins and check the output pins, once I know what chip it is. Further complications arise when I get into open-collector outputs, tri-state outputs, schmitt triggers, etc..., but maybe those will need separate questions.

Here is where I am stuck now: Is there a good way to detect which pins are inputs and outputs without driving any more lines than necessary? I will most likely start with all of my IO pins as inputs. I can use the microcontroller's weak pull-ups to drive floating lines up, so I know that any pin that is zero is definitely an output from the ic. I can use that info to narrow down my possibilities, but I doubt that will be enough. Any guessing by driving pins without knowing what are inputs and outputs seems like a good way to cause a short.

I was thinking maybe if I added a slightly stronger external pulldown behind a serial analog switch or something maybe I could turn on pull downs and check which are now high to get a better picture of what are inputs and outputs, but I don't know how well that would work, since it might change the inputs to the ic under test.

I read somewhere on here that the traditional way to detect high impedance is to put equal resistors to ground and power and measure the center with adc, but I don't have enough analog inputs for that to seem feasable.


texts: How to generate more current than available DC

texts:
I'm not an electrical engineer.

Is it possible to generate more current than an input could supply (DC system)? And if possible, what would it take to make it dynamic?

For example, a regular USB3.1 port can give 5V at 0.9A. What electronic circuit/ICs would I need to have an output of 5V at 3A? What would I need to make the current output variable depending on certain conditions (ranging from 0.9A to 3A in this example)?


texts:
Is there a way to monitor how much charge is left in a car battery?
What I am thinking is how a laptop or phone shows you what percentage is left.

I currently have an Arduino  connected to a car battery and I can easily get the current voltage... however I cannot get my head around what to do to get the remaining power.

There are other items connected to the battery that can be turned off and on at random... so the current draw isn't fixed


texts: Art of Electronics zero-crossing circuit question

texts:
I'm trying to make sure I understand how this circuit works fairly well before I read on.  Here is the diagram:

Here are some of the things I am thinking about this circuit:

Because input goes to the inverting input, positive inputs result in output at ground, negative inputs result in output at positive saturation (+5 V).

The capacitor is there to lower the resistance at that point and therefore the gain for higher frequency signals (maybe to filter out pickup), close to or above 6772 Hz.

The positive voltage through R7 is a pull up to make sure the positive output is close to 5 V.

The Schmitt trigger part of it is that the noninverting input will be at either ground or 5 mV (roughly 5 V through the 1/1000 divider), depending on the op-amp output.  So it seems as though the thresholds at the op-amp input should be the same, and that in order to center them, we would need to add 2.5 mV to the signal reaching the op-amp input, so that an incoming signal of -2.5 mV would become ground, and one of 2.5 mV would become 5 mV.

The authors state that the thresholds are +/- 25mV at the inputs, and that R4 centers them around zero volts.  This is (I think) the hard part for me.

It looks like the resistors at the input bring all signals to first about a tenth of their original value (which are then limited by the diodes if they are too high/low) (4.7k/(39k+4.7k)), then cut in half again by the 4.7 kΩ divider.

Without R4, it looks like the thresholds would be ground for negative-going crossings, and 5 mV for positive-going.  It looks like the 5 V supply through R4 would contribute only about 1.4 mV to the op-amp input (5 V x (4.7k||4.7k)/(10M+47.k||4.7k).  Because of the resistors at the input, that seems like it would correspond to a 28 mV input difference (1.4 x 2 x 10), which isn't too far off from what the authors say.  Still, I can't see how it centers the hysteresis completely, or how the hysteresis is plus/minus 25 mV at the inputs.  Can anyone shed light on this for me?


texts: How to power a fan from capacitor after main power is down?

texts: I power a 12V 0,84 W fan from a 5V power supply through MT3608 step-up converter. I would like the fan to work for about 5 seconds more after main power is down. Is it possible to do it using a capacitor? What should be its capacitance and connection to the fan?


texts: what does 3.4Vpp DAC output voltage mean

texts: My DAC (AK4384VT) specifies 3.4Vpp output voltage. does it mean relative to 0V such that there is -1.7V to +1.7V excursion of the signal or does it mean relative to +1.7V such that the signal lies between 0 to 3.4V?


texts: Maximum series resistor value you can place on an ADC with and without a buffer

texts:
I would like to know what would be the maximum series protection resistor i can place on an ADC with a buffer AND without a buffer. I know that with a buffer you can go up to the hundred kilo-ohm range, But what characteristic should i look for in the data sheet that tells that i should go beyond that.

The ADC i plan on using this on is the ADS131m08  and the buffer is the OPA2188. Applications will be used to measure differential AC signal at all frequencies the ADS allows(primarily 60Hz, giving it a bit more flexibility). The datasheet of the adc shows an application where a 1k series resistor (one for each input pin) is used.

I need the value so i can plan out the voltage divider and tvs diodes specs.

EDIT:

The input source that is what i am most interested to use with this ADC is a current transformer like the SCT-013-100.


texts: How do low price toys implement RF communication

texts:
I have seen toy remote controlled cars and other toys available for real low prices. How do they implement RF communication?

I mean to say when I search for RF units to buy they come at a pretty high prices. So obviously there is some way of implementing RF at lower prices.

Does any body have information on how toy manufacturers get RF working at such low prices? Of course given the fact that I don't want much communication between the remote and the sensor.


texts: Can devices be added in parallel indefinitely?

texts:
I'm assuming not, but say you added devices with the same resistance in parallel. All I've learned is that they would receive the same voltage and the current into and out of the voltage source would increase. It is impossible to just keep adding devices with no adverse effect.

So what decreases when you add more devices? The battery life?


texts:
I saw a bunch of videos about Tesla coil which works on like an air cored transformer producing high voltage but could be figured it out how exactly it works I mean if we bring a tube light, lamp then it starts glowing without any physical connection. we need a closed path to complete the circuit.
my questions are
1.how the power is transferred from the air directly to the load(a blub)?
2.if power is transferred then how it formes a closed path?


texts: Establishing Safe Operation Range for Lipo Battery with Buck Boost Converter

texts:
I have a circuitry that I need to power up with lipo battery. I need to regulate battery to 3.3V with buck-boost converter, since LDO can not be able to provide required current output and causes heating problem etc. In order to safely work with lipo, I need to disconnect the load when battery drops to 3.1-3.2 V. Therefore I checked for the buck-boost converters with UVLO property but I could not be able find buck-boost converter with 3.1V minimum Input Voltage. Hence, I wonder how appropriate to plug a simple diode between input of the buck-boost converter and Positive terminal of the battery for establishing 0.7V Voltage drop in order to being used with 2.5V minimum Input Voltage Buck-Boost Converters?
Datasheet of the Buck Boost Converter I am planning to use.
(https://www.ti.com/lit/ds/symlink/tps63050.pdf?ts=1596197768219&ref_url=https%253A%252F%252Fwww.ti.com%252Fpower-management%252Fnon-isolated-dc-dc-switching-regulators%252Fbuck-boost-inverting%252Fbuck-boost-inverting-split-rail-converters-integrated-switch%252Fproducts.html)


texts: How to mux 3 (high power) power supplies into 3 power rails with some pretty complex logic

texts:
I just want to say that this may be a bit of overkill but I'm really curious how I'd go about doing this.

I'm building a little drone from the ground up and got stuck on this issue.

I have 3 possible power sources, EXT (coming from an external power supply, probably 12V but not relevant), VBUS (coming from USB and mostly used for development, not enough power for motors) and BAT (an on-board battery, probably 4S but also not relevant).

There are 3 power rails: VCC which powers all of the control electronics, max ~35W, VMOT which powers the motors, possibly more than few hundred W and 5V which is usually generated by an SMPS using VCC rail but that's not needed when VBUS is present because it is already 5V so I would also like to bypass that.

I would want to make this system as flexible as possible so I cannot simply rely on some voltages being higher than others or something like that.

I really tried my best to come up with a concise way of explaining this logic but this "pseudocode" is the best I could do, I hope it's understandable and makes sense:

if (EXT is present) {
  VCC = EXT

  if (switch is on) {
    VMOT = BAT
  } else {
    VMOT = EXT
  }
}
else if (VBUS is present) {
  VCC  = nothing
  VMOT = BAT
  5V   = VBUS
}
else { // only BAT present
  VCC  = BAT
  VMOT = BAT
}

switch is just an arbitrary switch on-board so I can choose which PSU powers the motors because the external one might not be enough etc., just a flexibility thing.


texts: Reading internal temperature sensor STM32

texts:
I'm trying to read internal temperature sensor. Each time, the value from ADC conversion is 296 which results in negative temperature. Should I add something to the code below, enable some peripheral or my calculations are wrong?

#define TEMP_SENSOR_AVG_SLOPE_MV_PER_CELSIUS                        2.5f
#define TEMP_SENSOR_VOLTAGE_MV_AT_25                                760.0f
#define ADC_REFERENCE_VOLTAGE_MV                                    1210.0f
#define ADC_MAX_OUTPUT_VALUE                                        4095.0f

int32_t sensorValue, temperature;

__HAL_ADC_ENABLE(&hadc1);

// Disable Vbat signal from input channel and wake up temp sensor from power down mode
ADC->CCR &= ~(ADC_CCR_TSVREFE);

HAL_ADC_Start(&hadc1);
if(HAL_ADC_PollForConversion(&hadc1, 100) == HAL_OK)
{
    sensorValue = (int32_t)HAL_ADC_GetValue(&hadc1);
    HAL_ADC_Stop(&hadc1);
    sensorValue = sensorValue * ADC_REFERENCE_VOLTAGE_MV / ADC_MAX_OUTPUT_VALUE;
    temperature = (int32_t)((sensorValue - TEMP_SENSOR_VOLTAGE_MV_AT_25) / TEMP_SENSOR_AVG_SLOPE_MV_PER_CELSIUS + 25);
}
else
{
    temperature = -273;
}

return temperature;

--EDIT

#define TEMP_SENSOR_AVG_SLOPE_MV_PER_CELSIUS                        2.5f
#define TEMP_SENSOR_VOLTAGE_MV_AT_25                                760.0f
#define ADC_REFERENCE_VOLTAGE_MV                                    3300.0f
#define ADC_MAX_OUTPUT_VALUE                                        4095.0f
#define TEMP110_CAL_VALUE                                           ((uint16_t*)((uint32_t)0x1FFF7A2E))
#define TEMP30_CAL_VALUE                                            ((uint16_t*)((uint32_t)0x1FFF7A2C))
#define TEMP110                                                     110.0f
#define TEMP30                                                      30.0f

int32_t temperature;
float sensorValue;
float adcCalValue30 = (float)(*TEMP30_CAL_VALUE);
float adcCalValue110 = (float)(*TEMP110_CAL_VALUE);

__HAL_ADC_ENABLE(&hadc1);

// Disable Vbat signal from input channel and wake up temp sensor from power down mode
ADC->CCR |= ADC_CCR_TSVREFE;
ADC->CCR &= ~ADC_CCR_VBATE ;

HAL_ADC_Start(&hadc1);
if(HAL_ADC_PollForConversion(&hadc1, 100) == HAL_OK)
{
    sensorValue = (float)HAL_ADC_GetValue(&hadc1);
    HAL_ADC_Stop(&hadc1);
    temperature = (int32_t)((TEMP110 - TEMP30) / ((float)(*TEMP110_CAL_VALUE) - (float)(*TEMP30_CAL_VALUE)) * (sensorValue - (float)(*TEMP30_CAL_VALUE)) + TEMP30);
}
else
{
    temperature = -273;
}

return temperature;

ADC configuration:

  ADC_ChannelConfTypeDef sConfig;

    /**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
    */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

    /**Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
    */
  sConfig.Channel = ADC_CHANNEL_TEMPSENSOR;
  sConfig.Rank = 1;
  sConfig.SamplingTime = ADC_SAMPLETIME_480CYCLES;
  sConfig.Offset = 0;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }

I'm getting the output around 35 degrees. Is it okay to have such a big offset?


texts: STM32F4 Independent Watchdog (IWDG) not triggering as expected

texts:
Im trying to understand how Independent watchdog really works and i wrote a piece of code that runs on STM32F411VE Eval board. I believe i have configured the Watchdog Timer correctly according to Reference manual.

The Independent WDOG Timer is configured with Internal LSI with a frequency of 32KHz and a pre-scaler of 64.
The counter is set to 256. So if the Reload counter is not loaded within 0.5 seconds, the MCU should be reset. Is my understanding wrong?

What i dont understand is, the watchdog reset comes way too late than expected (5-6 seconds) if the counter value is not reloaded. I fail to understand why. Here's my Code.

//Initialise Independent Watchdog
void init_independent_wdog(void){

 IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);
 if(!IS_BIT_SET(IWDG->SR,0)){
      IWDG_SetPrescaler(IWDG_Prescaler_64);
 }
 //Set counter value to 256
 if(!IS_BIT_SET(IWDG->SR,1)){
       IWDG_SetReload(0x0100);
 }
 IWDG_Enable();
}

int main(void)
{
   SystemInit();
   SysTick_Init();

   //Initialize On-board LED GPIOs
   init_led_gpios();

   //Initialize On-board USART
   init_usart6_gpio();
   init_usart6_comm_module();

  //Initialize External Interrupt Button
  init_exti_struct();
  enable_exti_irq();

  //Initialize Independent WDOG
  init_independent_wdog();
  USART_TX_string("Hello1\n\r");

  while (1);
 }

 //Interrupt triggered when User Button at PA0 is pressed
 void EXTI0_IRQHandler(void)
 {
    if (EXTI_GetITStatus(EXTI_Line0) != RESET)
    {
        GPIO_ToggleBits(GPIOD, GPIO_Pin_15);
        IWDG_ReloadCounter();
        EXTI_ClearITPendingBit(EXTI_Line0);
    }
  }


texts: How do I create a working bandpass filter in LTSpice?

texts:
I am attempting to create a bandpass filter in LTSpice. I am fairly new to the program, which is probably contributing to my difficulties.
The filter I am creating needs to have a center frequency of 1200 Hz, with the cutoff frequencies at 1080 Hz and 1320 Hz. While the initial circuit design didn't seem so difficult, I cannot seem to get any working simulations. Here is my current schematic:

Note I initially started with a single stage that also produced similar results to this one. The second stage was added to narrow the bandwidth.

Here is the frequency curve this circuit gives me:

I honestly don't know what to make of this curve... It sure doesn't look like what a bandpass filter is supposed to be. I have triple checked all of my values and the general layout for the circuit, and I am at a loss for what is wrong. I have also a wide variety of other RC values and different OP amps with no success.

Just for testing, I also went ahead and built an active low pass filter. This one is also giving me a very strange frequency curve. Here is the schematic:

and here is the frequency curve:

Any help with this would be greatly appreciated. I am currently at a loss for other things to try. Thanks!


texts: Why have a smaller fuse on input & larger on output on a power supply

texts: This appears to be a common practice in automation control panels - for example - on the power supply it has a 10A fuse on 120VAC input side & a 20A fuse 24VDC on the output. That power supply ratings are: 100-240VAC~5.6A in & 24VDC~20A out. I am just tying to understand the reasoning for this.


texts: I am looking to make a capacitor/UPS system for a few different electrical components in my car. I want to power the rear view camera, headrest monitors, and possibly the head unit for about 30 seconds after their individual power has been isolated. That way they will all stay on when the power supply is changed, for example when the car is turned over. Not sure where to start or anything really about capacitors. I can get the current draw for all the components, but dont know what Diode/Capacitors to buy and wire in.


texts: How do I tell a serial port settings, when the hardware documentation doesn't have any info about it?

texts:
Trying to get a program to work with a serial port, but there is no serial port configuration settings given.

I have an old hardware board (a Stanley MC521 Controller) from late 1990s I guess. It has a serial port and I am trying to find out the baud rate and parity settings. How to identify the correct baud rate of an unknown serial port?


texts: HSPICE - Probing Current of an Element Defined By SUBCKT

texts:
For a regular resistor model, to plot I-V curve, I write:
R1 m0 m1 1
.probe DC i(R1)
Then, I open CSCOPE. i(R1) is listed. By selecting it, I can see its I-V behavior.

Now, I have a device that is defined with .subckt:
.subckt device m0 m1 param=p
Then, I instantiate it and probe it by:
x1 m0 m1 device
.probe DC i(X1)
However, when I open CSCOPE, i(x1) is not listed, so I cannot see the diagram.
Does anyone know the reason?


texts: Because of the type of my project I need a small battery which is rechargeable and which can supply about 3.3V and 2-3mA. The current varies , but I need to be able to do this at an average for about 10-15 days. I could not find any small battery (such as CR2032 which could do these). I may have a small solar panel to recharge, but it isnt going to produce much current. What is the best way to power such a circuit? Reducing current consumption is one, but it really is not possible


texts: Why is the input resistance of this ideal op. amp. equal to 10K? I know for a fact that that's the answer, I simply am not sure why. Since the 10k closer to the op. amp. is short circuited, why wouldn't the input resistance simply be infinity?


texts: Why wasn't interlaced CRT scanning done back and forth?

texts:
I was studying the scanning of old CRT screens and the interlacing strategy for video, and I started wondering something.

The raster scan process went top to bottom on odd lines, then back to top to raster the even lines. There is therefore a vertical blanking interval to send the electron beam back to the top position.

Why wasn't the initial design of CRT vertical scan made so that the vertical scan happened top to bottom on odd lines, and bottom to top on even lines, thus negating the need for the vertical blanking? It would of course require that the signal of the even lines to be reversed.


texts: Do case statements inside a for loop work in verilog?


texts:
I am trying to replicate this charging connector on my board :

it's basically a magnetic base that charge via contact of the pins.

The only way I can think that this is done is via pogo pins:

Once the board is screwed inside the case, the pogo pins are contracted and contact is made.

Does anyone have experience with this kind of design? Am I right about the pogo pins and if yes, is it something reliable for a product used in rough conditions? (considering the pins only make contact with the board and are not soldered.)


texts:
I am using LTC3624-3.3 regulator, with components as in the datasheet app notes - 12 V Vin, burst mode, 10 uF at in, 47 uF at out, 2u2 inductor rated at 2.3 A...

At no load, voltmeter says 3.34 V. Good. But with 47 ohm resistor across output (i.e. 70 mA load), Vout drops to 3.20, and at 10 ohm - 330 mA, to 3.05 V. This indicates practically no regulation. I changed output capacitor from tantalum to ceramic X5R, inductor from 2u2 to 10u, and neither changed anything.

Has anyone had no-regulation with LTC3624? Could part arrangement cause this? I believe I satisfied all design considerations from the datasheet, except that Vin trace runs for a 5-6 mm parallel to SW trace with 2 mm gap and with ground flooding on the bottom PCB layer...


texts: How come char[3] can be displayed with more than 3 characters?

texts:
char fromBluetooth[] = "zgr\r123\r";
   int name_length = 0;
    int pass_length = 0;

    while (1)
    {
        if (fromBluetooth[name_length] == '\r')
        {
            break;
        }name_length++;
    }

    char ssid_determined[name_length];

    for (int i = 0; i < name_length; i++)
    {
        ssid_determined[i] = fromBluetooth[i];
    }

    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print(ssid_determined);

This code should give a result on LCD as "zgr", but what I am getting on LCD is "zgr!\r\r". Can someone explain me how does this happen?

NOTE: That lcd object is Arduino's LiquidCrystal type.


texts: What's the name of the Altium designer rule that warns if component "enters" another component area (PCB)?

texts: The trouble is that this PCB is a capacitive pad and needs to stay inside the other component square area. What's the Altium rule to exclude this component?


texts:
I'm taking apart a misbehaving USB hard drive, and I've spotted a broken component on the PCB for the hard drive itself. Fortunately, there appears to be an intact, identical component on another part of the board, but I can't identify it.

The code on the top isFBD (sorry for the awful phone picture), it appears to have two connections, has been deliberately surrounded by a ground trace, and is 4.9 x 2.3 mm


texts: What do i need to get this motor running off a car-battery?

texts:
I'm going to build a motorized barn-door mount for astrophotography, but have ABSOLUTELY no experience with motors, circuits or anything else related to the motor.

This is the motor I bought: https://www.sparkfun.com/products/12219

I've read about resistors, voltage, wire gauge, etc, etc... I need it at 1 rpm consistently from I turn it on until I turn it of. I plan on having a snap-switch on the thing.

Now, what do I need??? I have the motor, motor mount, switch and that's it. What gauge wire do I need? Resistor? Fuse? One of those boards that look like they belong in a computer? I've searched in here and took a look at the videos where I bought the motor, but I'm too green in this.... Hope someone in here can help.


texts: How to generate a continuous clock from one that periodically turns off?

texts:
I have a LVDS clock signal that is gated about ever 30us. This is a MIPI D-PHY clock that switches from HS mode to LP mode when the data lanes go to LP mode (and are auto-clocked). The problem is that my receiver circuit does not support this and expects the clock to always be running so I wish to build some sort of buffer circuit that "continues" the clock in those periods where it is turned off.

Here is what the input signal looks like:

In the time when the input clock is on, I wish to have low propagation delay (ideally passing the input clock right through). However, when the input clock is off, I want the output clock to continue at the "last seen frequency"--skew does not matter much. Once the input clock comes back up, I want it to match the phase again. From the D-PHY standards, I think I have 85ns + 6 clock periods to do this.

A potential solution I thought of is to use a 2:n clock buffer with a select pin along with a PLL. The output of the buffer will be the PLL (and my application) and the inputs of the buffer will be the source clock and the PLL output. Then I can set the select pin to my DCLK+ so it will automatically select the PLL when it goes high. Will this work or is there some obvious problems?


texts:
I was wondering if it is possible to add my own Bluetooth module (Widcomm or any other chip) to my existing Arduino board? The current board transmits serial data using USB. I know there is a BT version of Arduino available, but it seems to be out of my budget.

If it is possible, then;
1. How do I integrate it to the board?
2. What changes would I need to do so that my board now transmits data via bluetooth?
3. Do I need to write any additional firmware for the BT chip?
4. If the BT chip comes with a built-in firmware, can I modify it? As-In I would like it to have a custom name and so on..

Any help would be really appreciable.

Thank You!


texts: How to calculate the energy output (in Joules) from an LED

texts:
I need to emit 20J over 5ms onto a target area of 962mm^2 from an LED source. The source as well as the target will reside in a completely encapsulated environment with reflective internal walls such that all of the energy will inevitably make its way to the target.

If I were to use a xenon flasher, rather than the LED bank, determining the output energy is quite easy: the bulb's data sheet provides the max input energy (electrical) to apply at the base to achieve the max output energy (in the form of light). Most xenon bulbs are 50% efficient at converting electrical energy into light energy so if I wanted 20J output I would purchase a bulb rated at 40J input and I would power it using the relationship E=0.5*C*V_c^2.

Does there exist a similar process for determining the output energy of an LED?


texts: How to find the Q point of the NMOS transistor in Voltage-Divider Biasing Circuit?

texts:
The following is the circuit needed to be analyzed to find the Q point(\$V_{GS_Q}, V_{DS_Q}, I_{D_Q}\$).

\$V_{TN}=1\text{V}\$
\$K_n=0.5\text{mAV}^{-2}\$

simulate this circuit – Schematic created using CircuitLab

Finding \$V_G\$,
$$V_G = \frac{R_2 V_{DD}}{R_1 + R_2} = \frac{10M}{3M} = 3.33\text{V}$$

Now we know that
$$V_{GS} = V_G - I_D R_S = 3.33 - (3\text{k}\Omega)I_D$$

For finding the load line,
When \$I_D=0\text{mA}\$, $$V_{GS} = 3.33 - 3\text{k}\Omega(0) = 3.33\text{V}$$
When \$V_{GS}=0\text{V}\$,
$$0 = 3.33 - (3\text{k}\Omega)I_D$$
$$(3\text{k}\Omega)I_D = 3.33$$
$$I_D = 0.00111\text{A}$$

There are two equations:
$$i_D = K_n\left[2(V_{GS}-V_{TN})v_{DS} - v_{DS}^{2}\right]$$
and
$$i_D = K_n(V_{GS} - V_{TN})^2$$

How do I use these two equations to find \$V_{GS_Q}, V_{DS_Q}, I_{D_Q}\$?


texts: Small Chip IC identification request - top code 9N (or N6) in 3 x 3 pad package

texts: Please help me identify this chip! It is square and 3mm in length, composed of 2 layer white ceramic. It has 9 golden pads. I think it's either a Hittite Microwave Corporation product or an Analog Devices product, but I was unable to pinpoint it.


texts: I'm using OctoPart dozens of times each day to check availability, pricing, specs, datasheets etc. However, I sometimes look for "popular parts", either when specs aren't that special or as a starting point to find suitable components. I know that "popular" is pretty vague, but is there any component search engine that has some kind of useful ranking other than price or the "relevance" sorting OctoPart does? I want to use common parts when possible, to ensure low price and good sourceability.


texts:
Edit: after a lot of trial and error I discovered that JB Weld works amazingly well for this.  You want the original two-part epoxy
  that comes in two completely separate tubes (not the newer stuff that
  comes in a single double-plunger tube) since it has a ~4 hour set
  time.  If you mix the two parts and then load it into a syringe and
  hook it up to an air compressor driven solderpaste dispenser (called a
  "glue dropper") you can plug holes really really fast and the results
  are great.  Dries rock-hard.  Keep in mind that JB Weld is ferrous
  (dried epoxy will stick to magnets, but that doesn't matter for my
  application.  Also JB Weld is electrically conductive, so if you're
  plugging more than one hold you can't use this for hot-pluggable
  devices since an incorrect insertion would make electrical contact on
  the pair of plugged holes, by way of the JB Weld.  Otherwise it's
  ideal.  You'll have to throw away the syringe and tip but they only cost
  a dollar or so.

Everybody's familiar with the ubiquitous 2.54mm box header (image below).

One common way of preventing reversed or misaligned insertion is to get the male header with a shroud and the female header with a corresponding key (second image below).  However this isn't always mechanically practical.  It also requires buying the headers in exactly the size you need instead of cutting them down from larger sizes.

An alternative way to prevent flipped/offset insertion is to omit one of the male pins (they can be pulled out of the header with pliers pretty easily prior to soldering; only pressure holds them in place) and plugging the corresponding hole of the female header.  However the plugging has to be done with a glue or epoxy that dries VERY hard, otherwise you can mis-insert the connector by pushing a bit too hard and deforming the glue.  I've been looking at electronics epoxies and there seem to be a dizzying array of them!

Question:

  Can anybody recommend an epoxy that dries very hard, hard enough to
  prevent a pin being driven through it?  Preferably a one-part, air-dry
  (not bake-dry), pneumatic-needle-dispensable epoxy if possible.

A pneumatic-needle dispenser (like the kind used for solder paste) would make it really easy to key a whole bunch of headers at a time; just stick the needle in the correct female header position, press the footswitch, move on.  Unfortunately I've found a lot of these headers use plastic that can't withstand reflow ovens, so an epoxy that doesn't require oven drying would be preferred (although even the heat-dried epoxies use much lower temperatures than reflow).

Thanks


texts: Li-Ion charging ic with 5V input and battery voltage between 3.9V and 3.6V

texts:
I am currently in search for a battery charging ic that has a variable output voltage (so that I can set it to 3.6V to 3.9V) or a fixed range, similar to what I would like to have.

But why would I want that? Its because most of the charger ics are charging the batteries up to 4.2 which is considered 100% of charge.

This will use every bit, the battery has to offer, but will also damage it in the long run, so I would like to maintain my level of charge between 20 and 80% which is 3.6-3.9V According to this image: From here

I have a hard time finding a suited chip, any advice is greatly appreciated!


texts: Pulsed Power Charging Resistor and Choke

texts:
I am currently attempting to build a pulsed power supply that requires an 8 H inductor to produce 50 kV 17 A square pulses with widths of 100 uS. Please see the attached schematic for more details (unfortunately, the load is comprised of a gas ionizing device, thus, the resistance fluctuates quite unpredictably).

Due to the obscurely high inductance required, I have considered using a charging resistor instead. However, I am unsure of how to find the exact resistance that will be needed to match the pulse-limiting capabilities of the 8 H inductor. How many I calculate the needed resistance?

simulate this circuit – Schematic created using CircuitLab


texts: Calculate total apparent, average and reactive power in 3-phase

texts: I am given a balanced 3 phase circuit question shown in the linked image. I am confused on the difference between apparent, average and reactive power and how each is calculated. This is my first post so I hope it is in accordance with the rules. Thanks


texts: Base resistor configurations, are there any differences?

texts:
Sorry for the noob question. From my understanding, R1s acts as pull down resistors for the base and R2 will limit the current flow to the base.
I have seen both configurations, but couldn't work out which one is actually appropriate, if there's any. Given the same resistance for R1 and R2, wouldn't the circuit on the left draw a lot more power? But if we choose appropriate resistor values so that the current draw are similar, will there be any difference between the two circuits?

How about in the case of MOSFETs?

Thank you!


texts: Is it safe to switch Vcc of Chip while IO still connected?

texts:
I'm planning to use an Arduino to control another chip by switching its power on and off using an N-Channel MOSFET, sort of like a SPI chip enable.

simulate this circuit – Schematic created using CircuitLab

I'm just a little worried that doing this could damage the chip because there still might be (logic-level) voltages coming in on its IO pins.

Should I be worried about this or will it be safe to use this circuit to switch the power off to the chip?

Any other comments about this circuit? Should it work?


texts: How to convert a +/-12 V digital signal to 0/+5 V?

texts:
What would be a simple way to convert RS-232 +/-12 V digital levels into +5/0 V respectively?

I considered an optocouple, but I can't find one that can withstand -12 V reverse voltage. I considered adding a two-resistor voltage divider, but I suspect that will worsen the slew rate of the device, and I have no idea if that will be enough to become a problem (I'm aiming at the switching speed of 19 200 baud).
There's this simple answer, but it requires a transistor that can withstand +/-12 V as well - I'm looking for one right now but haven't found a suitable part yet. I'm also slightly worried about not having galvanic decoupling.
I considered a 5 V linear stabilizer, but I suspect it may not be fast enough to turn off/on, after all, they weren't designed for this task.

Perhaps, an optocouple with a bulky diode in series capable of withstanding -12 V?


texts:
I wonder if any one can help me, I have tried several different configurations
and I can't get it. What I want is that when darkness comes the LEDs should glow
less according to darkness (but not fully off) and when sun rise then it will rise
according to the daylight.

In the schematic is an jumper for the LEDs (display 12v isolator) here I will have an LDR that do what I meant above. Any one that can provide me with a schematic so I can make the project clear.

Thanks in advance.


texts:
battery:

LiPo 11.1v 30C 4500mAh

Raspberry Pi:

5v usb

I had a 7805CT regulator laying around and I'm pretty sure I can use that to regulate power to my RPi from the LiPo but there's one problem:

The only cable free on the LiPo is the load balancer cable which is 3 hot wires (one for each cell) and 1 ground wire. I tried to connect the three hot wires to pin 1 on the regulator but it started to smoke. How do I combine the voltage from all cells so that I can reduce the total to 5v? I want to make sure I'm pulling from all the cells so that I'm getting an even discharge on the battery. Thoughts?


texts: Is balancing the only mechanism that regulates the phase currents in a three phase system?

texts:
Here is a basic illustration of a distribution system:

In a 3-phase AC system, phases cancel each other out, leaving only a small imbalance current and this is fed to earth at the substation. That is why when we touch neutral it is safe. I can understand up to this point.

Below is a transformer at a 3-phase system:

Here is my question:

Imagine some engineers set the electricity distribution such that it is balanced perfectly. Which means all the phases passes the same amount of current and no current flows from the balanced point to the earth.

But lets say one of the phases started to draw more current than the others, would the system now automatically balance itself by letting currents flowing from the balanced point? This is what I learned if I'm not wrong.

Is there an extra system which limits the current ratios?

I'm wondering whether there is an extra system to keep the three phase currents similar besides earthing the balanced point at the substation.


texts: How can you obtain SOP and POS (Boolean Logic) given the truth table?

texts:
Recently, it appears to me that few people on here are having issues determining SOP (Sum-of-Products) and POS (Product-of-Sums).  So lets go through an example to help those people solve their future homework questions instead of giving them the answer.  The initial question concerning SOP and POS is how you can obtain it from a simple K-map or truth table of few inputs Boolean logic?

What are the steps to take to solve for SOP? Or represent the truth table as SOP?

What are the steps to take to solve for POS? Or represent the truth table as POS?

Given the following truth table:


texts:
How can I drive a scavenged TFT screen, from an MP4, without its datasheet?

I'm thinking about making a low cost bluetooth wrist watch to check my messages on my phone on the go. I'm going to open-source the code and the hardware if I succeed.

I have scavenged an LCD panel, but do not know how to drive it.

Here are two photos from the TFT screen on the MP4 circuitry.

I have googled a lot and couldn't find any datasheets about this TFT.
Can anyone help?

I labelled my opinions on some of those pins on the LCD.


texts:
I made simple board with ATMega8U2 microcontroller for my USB experimenting (I'd like to make MIDI, HID, ... devices). I took inspiration in Arduino Uno. If you look on schematic below, you can see it is almost the same as Uno.

I programmed 8U2 with firmware from Arduino project — UNO-dfu_and_usbserial_combined.hex. Now, if I connect board to USB, I get serial port and it works just like Arduino, so this is perfectly OK.

My problem is: how can I put 8U2 into DFU mode, so I can change firmware without external programmer? If you look on picture, I connected HWB (pin PD7) to ground, so it should be simple — just pressing reset button. Unfortunately, it isn't working.

Am I missing something? Can be a problem in wrong fuse bites?

Edit: My fuses are lfuse=0xff hfuse=0xd9 efuse=0xf4

Edit2:

I checked fuses on chip

$ avrdude -p at90usb82 -P /dev/tty.usbmodem411 \
> -F -c arduino \
> -U lfuse:r:low:h \
> -U hfuse:r:high:h
$ cat high low
0x00
0x00

For programing, I'm using Arduino Uno as ISP and this commant (on Mac):

$ avrdude -p at90usb82 -F -P /dev/tty.usbmodem411 \
> -c arduino \
> -U flash:w:UNO-dfu_and_usbserial_combined.hex \
> -U lfuse:w:0xFF:m \
> -U hfuse:w:0xD9:m \
> -U efuse:w:0xF4:m \
> -U lock:w:0x0F:m
.......
avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
  0xff != 0x00
avrdude: verification error; content mismatch

So I suppose, avrdude did not programed fuses and they are still blank. Is it possible? Because board is working corrently, except DFU mode after reset.


texts: Can I use an op-amp to supply itself a negative voltage?

texts:
For my project, I am using an LM324. According to the datasheet, its power supply can either be +/- 16V or 0-32V (max). The output will range from -3V to +3V (or there abouts), so I realise I'm going to need a positive and negative voltage supply. All I think I'll be needing is +5V and -5V to power the op-amp.

Here is the question. I'll be hooking this up to an Arduino UNO, and this can't produce said negative supply. I was thinking of using one of the 4 op-amps within the chip to invert a +5V input to give -5V. I have ran some simulations using Proteus, and according to these simulations, the idea should work, but I know from experience that theory and practice can have very different results. Would using one of the op-amps in the IC to give itself a -5V be effective, or would I have to look into an alternative method of generating -5V?

I'm using an external DC power source (not portable), and I would like to avoid batteries, if possible.

EDIT: Thanks to everyone for your answers. I had a very strong feeling that it wouldn't be possible, but something in my mind was telling me otherwise. My aim was to use as few components as possible, but I guess I was asking for too much.

I have looked at my simulations again. They are currently on a non-network PC and am unable to transfer screenshots. There was indeed a bug somewhere, and it is now telling me that what I've done is wrong, which supports all your answers.


texts:
I have an issue with a analogue signal. Your help would be greatly appreciated.
The signal is a 5Vdc, it is an output from a PCB which is a source to many A/D PCB. its output is connected using wire of length around 3 meters to a breakout terminal. This point distributes the signal to other 4 places (A/D PCB) using long wire ( 10 meters) . the first stage of the A/D converter is a low-noise high-precision amplifier (TLE2027AID), the output of the A/D goes to a digital system which can be accessed using a software interface to read the digital value.
The issue I have is that when I inject 5 Volts at the source (before cabling), I read 5.1 VDC using the software, How is that possible to have more voltage than the input? capacitance effect is not there because it is DC.
Somebody can tell what could be the issue so I can do some more investigation? Any help would be great?


texts: How do I analyze this circuit with diodes?

texts:
If diodes in this circuit are ideal diodes:

I'm making assumptions to solve this circuit for I and Vo but I have some questions:
1. What is the voltage at the cathode of the upper diode if the other two diodes are off (i.e. open circuit) ?
2. If all diodes are on (i.e. short circuit), then will the circuit look like a resistor with voltages 16 and 12 at its ends?


texts: Is clamping a valid termination strategy?

texts:
This application note seems to suggest that for high-speed signals clamping diodes can be used to deal with overshoots instead of termination:

To manage signal integrity issues and protect the input pin, follow the guidelines in this document [...]
Guideline: Use Internal PCI Clamp Diode on the Pin
The PCI clamp diode can sufficiently clamp voltage overshoot to within the DC and AC input voltage
specifications when the bank supply voltage (VCCIO) is 2.5 V or 3.0 V.

I realize this will prevent the overshoot voltage from damaging the device, but I assume that "to manage signal integrity issues" means it is supposed to prevent signal reflections and ringing as well. Does it? AFAIK clamping diodes are very widespread in modern ICs, yet external termination resistors are common practice. What benefits does proper termination have, compared to this clamping approach?


texts: How do wafers translate to computer hardware?

texts: I am trying to figure out the relation between wafers produced in a fab and computer hardware.


texts:
i have a canon EOS 550D and i want to control it from computer. i had good result with taking photos with an ir led, arduino, and multi camera ir control library but i want to control also focus, and, if it is possible, the exposition (f number and time). i've tried to have a look but i don't understand if it is possible to control via ir led, or i have to build a remote jack simulation, or even is it is possible only with official sdk.

i even can take into account a gear system like this: http://www.instructables.com/id/Arduino-Lens-Controller-Synchronized-ZoomFocus-/


texts: My new 18650 battery got a little scratch near positive pole

texts:
So recently I just bought two new batteries. When I took it from the package I accidentaly dropped one of the batteries on the ground and a little scratch appeared near positive pole. It's actually pretty small scratch and i don't know if you can see it in the picture.

What should I do? Is there a posibility to cause a short?


texts: Visualising data rate as square waves (Converting bits per second into hertz) for selecting ADC sampling frequency

texts:
I know that bits per second and hertz are two different units. This question will help me in designing an oscilloscope with proper ADC sampling frequency  for viewing communication protocols.

Just imagine a communication protocol(eg: I2C) which has a data rate of 1Mbps. As per the protocol, there are different fields where we can keep data, address etc. But I am currently assuming that each bits in this protocol is toggling one after the other. Then this looks like a square wave.

In a square wave, the fist half will high(Logic 1) and the second half will be low(Logic 0) or vice versa. So in one cycle we have two bits. As per this visualisation 1Hz i.e 1 cycle/sec is equivalent to 2bits/sec(or 2bps).

Similarly for 1Mbps data rate, there will be 1000000 bits per second. If we assume each bit is inverse of the other(i.e they toggle like a square wave) and as per our calculation, 2bits will be present in one cycle of square wave, then
1000000 bits per second = 500000Hz (1000000bps /2 bits in one cycle). So 1Mbps is equivalent to 500kHz square wave.

Is my visualisation correct(I converted bits per second to hertz)?

I want to make a USB oscilloscope in which I want to select a proper sampling frequency for the ADC. So in this case if I assume 1Mbps as 500kHz, then for a good signal display(signal reconstruction based on the ADC samples), sampling should be done at 10 times the signal frequency i.e 5Mega samples per second (500kHz *10 = 5MHz)

Is this calculation correct ?

Also does this mean that I can view this communication protocol's voltage levels clearly on a oscilloscope having bandwidth of 5MHz (500kHz *10)?


texts: Solid state relay is not completely open when control inputs are not connected

texts:
I am trying to control a 12W light using this solid state relay. Even when I haven't connected my control inputs through an Arduino the output light glows(very dim). I have an input voltage of 230V. When control inputs are not connected there is a drop of around 180V across the relay. Why is this?

When I provide 5V to the control inputs, I see a resistance to 10K ohm at the outputs of the relay.

What should I do to control the light using this relay?


texts:
I just purchased a Gordak Instruments DC Power Supply PS-3005D for getting a power to cell phones that we do not have the battery for. Could someone let me know how to set the correct voltage output and other settings correctly?

On the device there is -

Current dial = 1A --->
Voltage output choice = 0-15v, 7.2v, 6v, 4.8v, 3.6v and 1.5v

Then there is two dials for voltage, one labes fine and one labeled Course.

I have positive, negative and Ground outputs. Is grounding when using these on a cell phone nessesary?

Thank you very much in advance!


texts: My question is if there is a way to reduce a clock to two thirds of its speed using flip flops because i know a flip flop cuts its speed in half.


texts: Can a motor driver for 5V be used for a 24V motor?

texts:
I’m controlling a 5V motor with Arduino but need more torque which means a more powerful motor. Here is my scheme. (I took it form a tutorial):

Here Arduino is controlling a 5V unipolar stepper motor through a Darlington transistor.

My question is if I just change this motor with a 24V one and feed the new motor with an external 24V power supply and remain the rest configuration same would the motor still be controlled? Or do I need another configuration?


texts: Sensing a USB device plugged in without having to supply 5 volt power all the time

texts:
I am designing a device using the PIC32MX795 processor that will act as a USB host.  Since it is a battery operating device, I would prefer to not supply 5 volts all of the time on the USB port (the device will operate off a 3.7v Poly-Lithium battery and use a DC-DC boost converter to generate the 5 volts).

I would like to keep the device powered down as much as possible whenever there is nothing plugged into the USB connector.  Is there some way of waking up when someone plugs in a USB device into the connector?

Even if I have to wake up once every second or so for a few milliseconds, that might be acceptable but I would prefer not to have to power up the 5 volts each time.

EDIT: After a device is plugged in, and I get data from it, then after some delay I would like to power it off so that it is not drawing current any more.  This will force the user to unplug the device and plug it back in again to read the data again, which is okay.


texts: Is there a current sense coil inside this ELCB?

texts: Is there a current differential sense coil inside this ELCB (Earth Leakage Circuit Breaker) just like GFCI or RCD? I took it from a unit and I dont want to break it apart to peek I cant find any schematic in the part no. I read in wiki  ELCB is based on voltage sensing, but isn't this was old 1950s tech. Modern ELCB still use it?


texts: How do I wire a Shure WL 185 to to iPhone or iPad?

texts:
I have this old but very nice mic. Old days I recorded audio to the camera or recorder. Nowadays I record to iPhone so I do not have extra recording device and cameras are action cameras usually without 3.5mm jack.

What I want to do now is to resolder the plug. But I am not sure do I need to add 4.7k resistor or not? Or even will it work at all?


texts:
I am trying to communicate with some batteries that uses SMBus. In the documens of batteries it only specifies the SMBus version which is SMBus v1.1 and do not mention about addresses nor the baudrate they use. When I ask to company they tell these information is enough and I do not need address or Baudrate.
So my question is: Is there a default SMBus address or baudrate that SMBus v1.1 uses (which I do not believe)? For example in CANBUS J1939 default baudrate is 250 kbps. I wonder if it's also a case for SMBus. Thanks.


texts:
Can someone explain what dependent and independent KCL equations mean to us, and how we can determine what is number of dependent/independent equations? I am reading about KCL and they said:

I don't understand this part: This in turn shows that the four KCL equations are dependent? What that dependent means to us when we have 4 KCL equations?


texts:
For a project I'm using an Arduino to drive a motor using a special pcb. In this board there is also a way to read the current drawn by the motor. Although I have the schematic I'm not 100% how this works and what the mechanism behind this is.

see the relevant part of the schematic:

Can someone quickly explain how I can use the Imotor2 connection to read the current, and why this works (the physics behind).

Thanks

R.


texts: How to use a smartphone / tablet battery?

texts:
I have a c11-me172v battery from Asus tablet. I tried but didn't manage to find a datasheet. There are 6 wires - two red, two black, yellow and white:

How it should be connected to power my circuit? How to charge it in DIY devices? Does it have a build-in interface that allows to figure out current charge or it's done somehow else, using external components?


texts: Suggestions on conductive materials for textile capacitive pressure sensors

texts:
I am doing preliminary research for my thesis.  The thesis involves textile capacitive pressure sensors.  I am trying to find out more about how the type of conductive material used affects the capacitance of the sensors so I can better design my thesis.  The layer my research will focus on is actually the dielectric layer, but I need to decide on a consistent and reliable sensor design and am a bit overwhelmed by all my options for conductive materials (both in terms of metal and construction method of the material.  ie. thread, knitted fabric, woven fabric, etc).  Ideally I would just use conductive metal plates for the electrodes, but most likely I will have to make the electrodes out of conductive fabric and an integrative fabric.  Any good resources and/or personal experience with picking conductive materials for textile based capacitive pressure sensors would be great.  What metals are preferable?

I am new to the site, so if I need to be more specific with my question, please let me know.  Thanks in advance.

**Edit:  I forgot to add that I am specifically measuring the impact of variations in the spacer material on the outcome of data collected by the sensor, in case that affects anyone's answers.


texts: Analog buffer/voltage follower with function table?

texts:
I'm looking for a buffer as I am going to fan out a VCM signal from an ADC to multiple ADC drivers.

    ADC VCM out: 0.95V 10mA
    ADC dr in  : 10Kohm x 3

Looking at the SN74LVC3G34, the datasheet mentions high and low a lot and a "Function/truth Table". This makes it sound like a schmitt trigger to me. Should I not be looking for a buffer?

If buffers are not what I think they are, is the solution to just pick a 3xop-amp IC and set them up as voltage followers?


texts:
Hi guys and thanks for reading and your help. I can't understand a thing that my book says: "When the temperature grows, the diode will let flow more current" and then it gives 2 formulas:

\$V_t = \frac{nKT}{Q}\$
\$I = I_o( e^{\frac{V}{V_t}}-1\$)

Where T is the temperature in Kelvins, K is the Boltzman constant and q is the charge of an electron. The problem is that when \$V_t\$ grows (So when the temperature grows) \$e^{V/V_t}\$ will become smaller, since a number divided by a bigger number will become smaller, and so \$I_o\$ will become smaller. If \$I_o\$ become smaller, also \$I\$ does. So when the temperature grows, \$I\$ will become smaller, but my reasoning is wrong. Why?


texts:
I am trying to use gschem/gnetlist/ngspice to do some circuit simulations. I have a subcircuit schematic and have created a symbol. I am able to add the symbol into the higher level schematic in gschem but when run gnetlist I get the following error:

WARNING: Found a placeholder/missing component, are you missing a symbol file? [<symbol file name>]

The device does not appear on the output netlist. The symbol file is in a subdirectory called "symbols" and in my ~/.gEDA/gafrc I have the line

(component-library "./symbols" "Local Symbols")

as per advice on the gnetlist mailing list but for some reason it still cannot find it, though gschem finds and uses the symbol without a problem. I've tried many things but I cannot get gnetlist to find the symbol. I've scoured the Internet for an answer to no avail and I posted here because there is apparently no simple way to post the question on the gEDA mailing lists. Anyone have an idea what is going on here?


texts:
My old/new laptop adapter specs as given below. I understand the output current for new is 4.5A which is OK  when compared to old which provides 3.25A load since it can provide more load.

However, just cant seem to find any idea about input Ampere i.e 1.2A max vs 1.5A(1.5A) I am left with below questions.

Does max in 1.2Amax mean anything.
does the bracket (1,5A) mean anything.
is the new adpater usable inplace of the old

NEW -
90W 20V
AC INPUT 100-240VAC 1.2A max
DC OUPUT 20V / 4.5A

OLD -
65W 20V
AC INPUT 100-240VAC 1.5A(1,5A)
DC OUPUT 20V / 3.25A(3,25A)

I think one of the questions regarding brackets probably might just be dot vs comma notation

3.25A(3,25A)


texts: How can an inverter transfer energy to the power network?

texts: It is possible to use an inverter to transfer energy from home made produced energy to the main power network. It is not clear to me how this can be achieved. What type of load appear to be the power supply network? What are the strategy to have the power flowing from the inverter to the the load and not vice-versa?


texts: Conducted Emission Fail at High Frequency

texts:
Good Morning All

We run Conduction emission Test on Lab with the Line filter and without the line filter. Product was 230V 16A welding Power supply. Below are the graph with line filter and without Line filter.

Question is even with Filter Coonecting I am getting failure on High Frequency Side.(around 22 Mhz to 30Mhz), I tried with Different-Different Core(All most of core manufactures with Ferrite and Nanocrytalline Materials), No of turns, Changing Cx and Cy Value , Single filter and double stage filter, Stack up the Cores Alos. Even with all tried I have the same problem of noise at same frequency.

Please suggest some method to suppress this high frequency noise, I am going next again for lab Testing.

Thanks


texts: How does a flip-flop circuit keep it state?

texts: When reading about the difference between SDRAM and SRAM (electronically), I understand that SDRAM requires the dynamically charging of the capacitors to maintain their states. I do not get how SRAM maintain its state. SRAM are essentially flip-flops and probably relies on the processor to remember what current flow goes into the flip-flops to get a state. So I do not get what is "Static" in flip-flop/SRAM (e.g. a spinning disk drive would use magnetism to maintain a state - that's more static). Or, am I misunderstanding something here?


texts: Creating Serial Pressence Detect data from discrete DDR RAM datasheet

texts:
I have a board that has soldered discrete DDR RAM chips. The datasheet for the DDR RAM chips is available to me. The DDR memory controller is programmed manually using pre-calculated values.

I have modified the bootloader (u-boot) to perform automagic DDR memory controller initialization. u-boot will act as if the discrete memory is a DIMM. For this to work, the SPD chip read process was modifed. When u-boot performs a read of the SPD data an array containing the SDP data will accessed. All I need now is an array of valid SPD data that matches the configuration.

I have the DDR RAM chip datasheet, and I've got one day (or more) to spare. How do I create the SPD data? What are the maths involved? What free tools are available?


texts:
I have noticed, that my +12V Buck Converter LMR16006X (Datasheet) has some voltage peaks with a constant frequency for any input voltage from +15V to +48V. This peaks are also independent of the load and I'm not sure, where it really comes from. I think, that I have choosen a wrong inductor, but at the moment I cannot prove it.

There are no peaks on the input voltage
The peaks occur with around 100ms in between directly at the +12V output
There is always a double peak with around 1.5ms in between

So can this happen, if the inductor goes into saturation? I have the following components:

From the calculations in the datasheet I get 100uH as the minimum inductor value. So this should be good, but I'm unsure about the saturation current, my inductor seems to have only 420mA, I have not seen that when I have chosen it. Could be this the cause of the problem or may the tolerance of 20% be the reason, such that my inductor may have only 80uH and so less than needed?
The Layout looks like this and should be fine:


texts: Eagle airwires for pins of the same name

texts: I am finishing up a four layer board and as shown in the picture below, Eagle is showing me around 40 airwires in the DRC. I have tried everything i can think of to get rid of them, rerouting each net multiple times. The Eagle run length script also shows that there is no remaining unrouted net length, which I find strange. I know that I could probably send the board to be manufactured and it would be fine because all the nets are connected as they should be, but it is very uncomfortable to have errors in the DRC and it would be great if anyone had an answer or has experience something similar.


texts: In a RAKE receiver, why is a Path Searcher needed? Can't the delays be found from the Channel Estimator?

texts: I am a little confused, since the Rake Receiver has one finger for each multipath path, and the channel estimator models the impulse response of the channel and can be used to find the multipaths, why do I still need a Path Searcher?


texts: Implementing a deadband on a PID controller for a dc motor

texts:
I've been building a system to control motor position using a microcontroller.
But I faced some problems during the implementation of the PID controller and I found out, thanks to this article: http://www.wescottdesign.com/articles/Friction/friction.pdf
that the problem is friction. The following image shows the response of my system using a PI controller:

Where the orange line is the PID output variable and the blue line is the angle of the motor axis(what I want to control). If you compare this image to figure 12 on page 12 of the article posted above we can conclude that friction is the problem.
Also in the same article one of the given solutions is to apply a deadband to the controller but I'm having some difficulties understanding how to implementing it. If my PID controller code is:

angulo = (encoder*360)/(4*102.0);
erro = setpoint - angulo;

d_term = kd*((erro - erro_ant)/0.00125);
i_term = i_term + ki*(0.00125*erro);

output = kp*erro + d_term + i_term;

erro_ant = erro;

if ( output >= 0 )
{
    direcao(1);
    setPWM(fabsf(output));
}
if ( output < 0 )
{
    direcao(0);
    setPWM(fabsf(output));
}

The direcao() function will change the h-bridge pins to make the motor rotate in the correct direction.
And what I fought to do was:

...
erro_ant = erro;

if (error is within deadband)
{
    setPWM(0);
}
else
{
    if ( output >= 0 )
    {
       direcao(1);
       setPWM(fabsf(output));
    }
    if ( output < 0 )
    {
       direcao(0);
       setPWM(fabsf(output));
    }
}

or

...
erro_ant = erro;

if (error is within deadband)
{
    output = 0;
}
if ( output >= 0 )
{
    direcao(1);
    setPWM(fabsf(output));
}
if ( output < 0 )
{
    direcao(0);
    setPWM(fabsf(output));
}

I also fought about setting the integral term to zero, when it is within the deadband, but that will act as a anti-windup technique when the system overshoots.

Thanks in advance to anyone who answers.


texts: Are there 4 position switches that control power to a circuit and provide state?

texts:
I'm trying to find a 4 position switch to use with an arduino project.

The first position would be off, as in no power to the arduino.  Positions 2,3,4 would all provide power to the arduino and I need to be able to tell which position the switch is in.  Think of

OFF-LOW-MED-HIGH

What sort of switch would accomplish this, and how would I wire the power and the pins to the digital pins on the arduino?


texts: Sdcard stated bandwidth at max working hours

texts:
Sandisk and many sdcard companies state the amount of hours they can work without hitting wear issues.
Usually they state this while recording Full HD video but they don't state how much mbps that is.
Any idea what is commonly used when talking about full HD? How many mega bits per second is that?
Example:
https://shop.westerndigital.com/products/memory-cards/sandisk-high-endurance-uhs-i-microsd#SDSQQNR-032G-AN6IA


texts: Controlling the brightness of multiple LEDs at once

texts:
I'm building a device for DJ-ing. When practicing at home I prefer the LEDs on the device to be quite bright, but when I'm in a club setting I'd like to dim them to my liking so that I'm not blinded by them. The brightness should be controlled via a potentiometer connected to an analogue input on my Arduino but I'm intending to switch the LEDs individually (no mutliplexing) with digital outputs.

I have a bunch of 2N3904 transistors so I thought maybe I could use them in some configuration, but I'm having a hard time finding a simple way to do this.

EDIT:
I'm happy to provide any additional information.

Regarding the LED's: I'm using 15 regular 5mm LED's.

Controller: Meduino Mega2560 R3 Pro Mini.

Power: The device will be powered by a 9V wallwart but I'm not too sure if it's OK to use the 5v regulator output on the MCU-board.


texts:
I am designing a Raspberry Pi shield and it needs to have two separate supplies: one for the RPi itself, and one for the rest of the circuitry (consisting of energy metering ADE7758 chip). I plan on using Mean Well switching mode power supplies. The ADE7758 part of the circuit needs 5V/100mA. The RPi supply needs to provide 2A at 5V.

The concern I have is about the power supply ripple and I am looking for advice on how to calculate the value for the smoothing capacitor or any other method for smoothing the output of the supply. I don't want to plug in a LDO regulator after the SMPS as I don't have enough space on the board. The datasheets of the power supplies specify 150mV and 200mV ripple but do not specify the frequency, so I assume it is 50Hz.

Using the equation for capacitor discharging  is giving me unreasonable values if I use Vc = 5.000, starting voltage 5.075V and t = 0.01s: 13.43mF. That is if I want to reduce the 150mV ripple in half.

Edit 1 (as suggested by the comments): Acceptable ripple for the RPi supply is 120mVp-p, and for the ADE7758 power supply is 50mVp-p.

Edit 2: Adding a schematic.


texts: Assistance with 18650 3S battery pack for RC

texts:
Need some assistance. I am not sure if this is the correct forum.

I have an OverDrive JLX RC vehicle. The original battery is 12V 800mAh and I am unable to find these batteries anywhere. I decided to make a 3S battery pack from 18650 cells with a 10A battery management system (BMS) board. The pack charges fine and when connected to the RC vehicle it runs fine, however the 18650 3S pack gets really warm and the wires get really hot.

I can't seem to find the specification for this toy so I am unable to tell what is the current draw of the motors. I assume it's getting hot because it is being discharged too quickly? Would adding a resistor suffice as current limiting, and if so, how would one calculate the value without knowing the current draw of the motors?


texts: Motor shield R3 does not supply full power

texts:
I'm currently trying to build a small independent rover from my old Lego Technics set. Currently I power two 9v DC motors (2838) using an Arduino motor shield R3 in combination with an Arduino Uno. I connect the motors independently to the two outputs of the motor shield and use an external 9V power supply to power the Arduino via the barrel jack. All this worked fine in the beginning with both motors doing their job at full speed. (The software should be OK - I did set all needed pins on their desired values (brakes off, directions on, PWM to 255)).

Now here's the problem: After having tinkered around a bit with my design it seems to me as if I have broken the motor shield. As I said, the software worked in the beginning. I also double checked the motors by directly connecting a 9V battery to them, they both work just fine. Also, the Arduino board itself is unharmed; I checked it with other designs just to make sure. But the motor shield does not supply enough power to the outputs anymore and so the motors don't run properly. I used my multimeter on the motor shield's output terminal screws and voltage was down to about 7.4v. Is this a normal behaviour or is the shield really broken? If so, what could be a possible cause for the lack of power on the output?

I would be very thankful for any comments or hints, since googling the problem did not show any useful results.


texts:
I'm trying to get to know my PIC with simple 'start-up' projects.
I made a LED flash with a button.
I made a BCD count up from 0 to 9 with a delay.

Now I want to combine those two and also refractor the code a bit. So I want the BCD to increment on each button push. Ideally that would use an interupt, but not necessary for this aplication. Next step would be use the interupt and have two inputs (for up or down) and then swap the buttons for a rortary encoder.

The questions I have are:

where should I 'store' the current value on off the BCD? a global var in main?
why do I get this type redeclared error and function declared implicit int warning?

The BCD is on PORTA, the input (active low) is on PORTB.RB0
These are the two progams that actually work:

void main(void)
{
    /* Configure the oscillator for the device */
    ConfigureOscillator();

    /* Initialize I/O and Peripherals for application */
    InitApp();

    while(1)
    {
        if (PORTBbits.RB0 == 0){
            PORTAbits.RA2 = 1;
        } else {
            PORTAbits.RA2 = 0;
        }
    }
}

Note that RA2 would be connected to a normal LED.
And for the counter:

void main(void)
{
/* Configure the oscillator for the device */
ConfigureOscillator();

/* Initialize I/O and Peripherals for application */
InitApp();

// lookup table for BCD
const uint8_t pat7seg[10] = {
    // RA0:6 = ABCDEFG
    // RA7:0 = FG-EDCBA
    0b01000000, // 0
    0b11111001, // 1
    0b10000100, // 2
    0b10010000, // 3
    0b00011001, // 4
    0b00010010, // 5
    0b00000010, // 6
    0b11111000, // 7
    0b00000000, // 8
    0b00010000, // 9
};

// current digit
uint8_t digit;
digit = 0;

while(1)
{
    for(digit = 0; digit < 10; digit++){
        PORTA = pat7seg[digit];
        __delay_ms(2000);
    }
}

}

So I tried to 'combine' these like:

void main(void)
{
/* Configure the oscillator for the device */
ConfigureOscillator();

/* Initialize I/O and Peripherals for application */
InitApp();

// current digit
uint8_t digit;
digit = 0;

while(1)
{
    /* TODO <INSERT USER APPLICATION CODE HERE> */
    /*for(digit = 0; digit < 10; digit++){
        PORTA = pat7seg[digit];
        __delay_ms(2000);
    }*/
    if (PORTBbits.RB0 == 0){
        digit = updateBCD(digit);
    }
}

}

uint8_t updateBCD(uint8_t myCount) {

    /* define constant for lookup BCD */
    // common anode so, inverted
    const uint8_t pat7seg[10] = {
        // RA0:6 = ABCDEFG
        // RA7:0 = FG-EDCBA
        0b01000000, // 0
        0b11111001, // 1
        0b10000100, // 2
        0b10010000, // 3
        0b00011001, // 4
        0b00010010, // 5
        0b00000010, // 6
        0b11111000, // 7
        0b00000000, // 8
        0b00010000, // 9
    };

    if (myCount < 9){
        myCount++;
    } else {
        myCount = 0;
    }
    PORTA = pat7seg[myCount];

    return myCount;
}

errors:
(908) exit status = 1
main.c:46: warning: (361) function declared implicit int
make[2]: * [build/XC8_16F628/production/main.p1] Error 1
make[1]: * [.build-conf] Error 2
main.c:52: error: (984) type redeclared
make: * [.build-impl] Error 2
main.c:52: error: (1098) conflicting declarations for variable "updateBCD" (main.c:52)

I use a PIC16F628 and MPLAB X IDE 2.00 with XC8 compiler.

Hope you can help.


texts:
MCP4725 has internal reference voltage which is equals to VCC:

  VDD is the power supply pin for the device. The voltage at the VDD pin
  is used as the supply input as well as the DAC reference input. The
  power supply at the VDD pin should be clean as possible for a good DAC performance.

Also it needs 50mA of current:

I want to use one LM4040AIZ 4096V reference voltage as power supply for three DACs but the forward current of LM4040 is only 10mA.

So I need LM4040 to provide at least 150mA, How can I achieve that much of current with only one LM4040?

* MCP4725 and LM4040 are the only parts that I have access to.


texts: lt SPICE: How to show the center frequency in the error log (of a band-filter) in ac sweep using .meas?

texts:
I'm trying to measure the center frequency of band pass fillter.
And use
.meas maxGain MAX V(Xo)/V(xi)
I can get the max gain easily.
But I cannot find a way to get the frequency at the max gain point.
I tried
.meas AC res FIND frequency AT V(Xo)/V(Xi)=0dB
.meas AC res FIND frequency AT V(Xo)=108.8m
The log shows:
res: frequency=(-1.#INFdB,0? at 0
How to solve it?


texts: How to find a fitting cooler/heatsink for a Mosfet?

texts: How do I find a fitting passive cooler/heatsink for a TO-220 Mosfet? What parameters do I have to search for?


texts: What happens if the Ground plane is expanded/poured in the VCC/Power layer in the multilayered PCB design? Is that recommended?

texts:
I just wanted to know what are the advantage and disadvantage expanding the ground plane in the VCC/power plane in the multi layered PCB.
Below is the 10 layered PCB stackup:-
TOP,
Gnd,
Sig 1,
Sig 2,
VCC1,
VCC2,
Sig 3,
Sig 4,
Gnd,
Bottom,
I want to expand the GND plane in VCC1 and VCC2 layer. The reason behind is to provide solid ground reference for the signal present in the sig 2 and sig 3 layer.


texts: Can I divide 3kV pulses with a voltage divider?

texts:
The pulses are generated with a high voltage push/pull switch that outputs high voltage pulses at the voltages it being fed by a DC high voltage power supply and the signal is controlled by its TTL input. The generated high voltage pulses have picosecond level rise time.
Such pulser has one output and is rather expensive. Now I need 2 synced pulses at 3000V and 2400V. It would be problematic and expensive if I use 2 such pulsers. Is it possible that I use a voltage dividing device to create 2 pulses from 1 3000V pulse with sub microsecond rise time? In addition, the voltage divider needs to have high impedance so that it doesn't consume a huge amount of power.
The divided pulses will have no load, since they are meant to create electric potential difference inside a vacuum system. Sometimes the ion beam would hit the electrode and create a small current (sub-μA level), and in this case the load can be regard as a minuscule capacitor.
I have tried to divide the voltage of TTL pulse using metal oxide resistors, the output wasn't great. The rise time to 200 mV was longer than 10μs. At first I thought it was the large parasitic inductance of the potentiometer, but after I changed it to a fixed resistor the problem remains.


texts:
I have a transformer with several secondaries, and this is how I'm planing to control the inrush current:

simulate this circuit – Schematic created using CircuitLab

I'm using a resistor to limit the inrush current and MCU will energize the relays after a few seconds to bypass the resistors.

Can I use a single resistor and relay on the primary to limit the inrush current instead of using a relay for each secondary?
How can I activate the relays without an MCU, using only analog circuitry?


texts: Want to understand the led series/parallel and parallel/Series combination circuit

texts:
I'm Working on LED load design circuit which is up-to 64V@1.2A. I thought of giving LED's in series and parallel combination with switches to control the voltage but while searching I found one circuit.

From theoretical point of view both are same but what's the main difference in both the circuits and which one performs better.IS there anything related to thermal protection?