texts:
Our generator is connected to grid by 33kv line. Due to some reason we supply a fixed amount of power to grid. This is done by a device named Auto Load Limiter Device which looks like

It measures line current. But here we used this device to limit the power. We can set upper limit and lower limit of current. For example,
Upper limit=120A,
Lower limit=117A,
Then it reduces fuel when current is greater than 120A and vice versa for lower than 117A.
For a 33kv line 120A means around 6MW power.
But the problem is, there is no polarity check for power. I mean it shows 120A(6MW) when we supply to grid. But if 120A(-6MW) comes to generator (it also called reverse power) it doesn't change it's polarity. Suppose in a faulty condition current becomes -20A(-1MW), now it is desired to be 117-120A(6MW), but MT4W increases it to -120A(-6MW) from -20A (-1MW). But our generator trips around -40A (-2MW).
How to solve this problem?
 Is there any setting in MT4W so that it can measure reverse current?
What parameters should i change in MT4W?
 You can say to use power meter  which needs ct pt to measure power. power measurement is not my problem. We use this MT4W device to limit the load we supply to grid at 6MW not to measure power. You can ask why i need to limit the load to exact 6MW. The answer is, due to poor condition of transmission line we shouldn't exceed 6MW. This is a 40MW gas turbine and we supply 6MW to national grid and remaining 34MW goes to domestic load.
Every power plant can run in pre selected load mode where you can select the load you want to supply. But it is only possible when you are solely connected to grid. But i can't use this feature because i am giving 34 MW (15-34MW, 34 is peak value) domestic load. In grid you can control your power. You can supply as much as you want, also can take from grid as much as you want. But the domestic load is beyond the control.After fulfilling the domestic load, i have to control the load to grid at 6MW (which is done by MT4W). I already read the MT4W datasheet and there is a setting to show display value from -1999 to 9999 that means also negative value. But how to activate? Or is there any other way to limit the load?


texts:
I'm trying to measure the battery voltage of 30V using the ADC of an AVR Atmega8, AVCC is connected to 5V.

I connected a suitable voltage divider: R1 is 270k, R2 is 10k. The result I get is wrong at all, at 30V I get 23V.
The equation I use is batteryvoltage = 5*1023/adcReading.

// Read the AD conversion result
unsigned int read_adc(unsigned char adc_input)
{
ADMUX=adc_input|ADC_VREF_TYPE;
// Start the AD conversion
ADCSRA|=0x40;
// Wait for the AD conversion to complete
while ((ADCSRA & 0x10)==0);
ADCSRA|=0x10;
return ADCW;
}
unsigned int adcReading = 0;

adcReading = read_adc(0);
batteryVoltage = 5*1023/adcReading;


texts: Difference between Linear control theory and non linear control theory? especially topics/contents wise?

texts: Although I know that a linear systems is the one that follows principle of superposition but I want to know what topics/contents do we study in each of both categories linear control and non linear control?Please kindly give some examples of both categories


texts: Is it important to file a new soldering iron tip before tinning?

texts:
I bought a cheap soldering iron. After reading articles and watching videos, I learnt that cheap irons get their resistor burnt easily. And many a times the iron becomes black as soon as you start heating it and then it cannot be tinned.

I am afraid that if I do not do everything right I will burn my iron too.
So I just want to be sure that,

Should I tin my iron first as written everywhere or file it?

I have also got soldering paste and one meter silver coated solder.

Should I first apply the soldering paste on the iron then heat it for tinning?

Update

Here is the iron. It does not look like pure copper but the cover says its pure copper.

So now that I have shared the final discription of my problem. Please tell me if your opinions about filing it have changed.

Thanks to all of you for helping.


texts: Can I extend my ESC to motor using some thick wire? is it possible to do in that way

texts: I'm doing a drone project for my academics. my arm of the drone is a little bit longer. How can extend my ESC? I watched extending a power-ESC cable will make problem, but increase ESC-Motor cable will not affect. If is it true, then which wire can I use to extend my ESC length? will it affect my motor performance?


texts:
I'm trying to simulate BPSK in a channel with Rayleigh fading and AWGN, then obtain the Bit Error Probability (BEP). My program is written in C.

I compared my BEP vs \$\frac{E_b}{N_0}\$ (SNR per bit) plot with one generated using the formula BEP = \$\frac{1}{2}(1-\sqrt{\frac{\bar{\gamma_b}}{1+\bar{\gamma_b}}})\$. It appears that my simulated BEP is always about twice that of the theoretical BEP.

In my simulation, the received BPSK signal model is given by
\$r(k) = \sqrt{E_s}\alpha e^{j\phi(k)}+n(k)\$
where k is the time step, alpha is the Rayleigh distributed random variable, and n(k) is the noise due to AWGN.

\$E[\alpha^2] = 2\sigma^2\$, and \$\alpha\$ is generated as \$\alpha = \sqrt{w_1^2 + w_2^2}\$ where \$w_1, w_2 \sim N(0,\sigma^2)\$. Here, \$\sigma^2 = 0.25\$.

This is how my program is implemented.

1) Set the message phase in 2D (msg_phase[0] = 0.0, msg_phase[1] = \$\pi\$)

2) For different SNR values, do the following:

2a) Calculate \$E_s = E_b = 10^\frac{SNR}{10} * N_0\$

2b) Randomly select signal to transmit, with each signal equally likely to be sent.

2c) Generate \$\alpha\$ by first generating a pair of independent, zero-mean gaussian random variables with variance equal to 0.25, then setting \$\alpha\$ based on the equation above.

2d) Generate another pair of independent standard gaussian random variables as AWGN.

2e) Set the received signal to (\$\alpha\$ * transmitted_signal + AWGN noise)

2f) Calculate the received signal magnitude and phase as follows:

\$\text{Magnitude} = \sqrt{\text{Rx}_0^2 + \text{Rx}_1^2}\$

\$\text{phase} = \text{tan}^{-1}\frac{\text{Rx}_1}{\text{Rx}_0}\$

They are used in my receiver decision.

2g) Receiver decision. For incorrect decision, count the number of error bits.

Repeat Step 2b to 2g until 500 error bits are obtained, then calculate BEP.

The same code was used to simulate differential BPSK and the results matched the formula for BDPSK. The received signal model for the differential simulations is \$r(k) = \sqrt{E_s}\alpha e^{j(\phi(k)+\theta)}+n(k)\$, so I've basically used the same code but with \$\theta = 0\$ and the generation of \$\alpha\$.

I don't know why my BEP is twice the BEP obtained from the formula.

I've seen a few Matlab simulations that do something called "equalization" to remove the fading effect at the receiver, before computing the decision metric.

For example,

for ii = 1:length(Eb_N0_dB)

n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white gaussian noise, 0dB variance
h = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % Rayleigh channel

% Channel and noise Noise addition
y = h.*s + 10^(-Eb_N0_dB(ii)/20)*n;

% equalization
yHat = y./h;

% receiver - hard decision decoding
ipHat = real(yHat)>0;

% counting the errors
nErr(ii) = size(find([ip- ipHat]),2);

I don't do that, but is that necessary? As the Matlab simulations are implemented rather differently from my program, I'm not sure how the "equalization" would work for my case.


texts:
My PMIC uses the DP/DN pair of USB type C to get the maximum current that it can draw to power up the circuit or charge the battery. The problem is that i don't have a hub and the signal from connector is singular and needs to arrive at CPU.

Could I route it near the PMIC create a little stub near the pad and continue to the CPU like in picture?

Thanks


texts:
This question is to get general idea of servo and stepper motor.

Assume same power rating motor and same voltage rating two motors. Which are servo motor and stepper motor. Same gear ratio.

what is high torque motor?
what is high stall torque motor?
what is high holding torque motor?
which motor is big size?
what is high velocity motor?

Assume same size motors which are servo and stepper motor.

what is high power motor?
what is high torque motor?


texts: Is there a PCB-layout related reasoning behind DDR memory package and footprint?

texts:
BGA DDR packages have a unique footprint. There are two columns of pads on both sides of the device, and an empty column in between.

Is there a reasoning behind the placement of these pads (in terms of PCB layout), or is this just a consequence of the design of the ddr3 silicon die?

More specifically, what I am wondering is, are there any tips/tricks/guidelines to place DDR modules on both sides of the board, directly across, or very close to each other?


texts: Connecting GPIO and SPI signals via cable

texts:
There is a requirement in one of our systems to transfer signals from  one board to another board in the same system.

The signals are GPIOs and SPI lines from I.MX6 processor and it is in 3.3V level.

The board to which these signals are supposed to be connected is approx 1 feet away from the processor board. So the cable length would be 1-1/2 to 2 feet.

I am planning to convert these signals as differential signals via RS422 transceiver(to attenuate external interference) whereas my buddy is suggesting me to convert the signals as open drain outputs and feed it to the other board.

Questions:

Which is the best practice of above two or could you suggest an alternate way of achieving this?
How does open drain signaling help in long distance transmission? (I do not want to learn from my buddy :-))
What are the other things to be considered while transferring signals via cable?


texts: How do I find the power of this circuit?

texts:
This is a circuit from one of my texts:

according to the text power in I1 = -12 watts, R1 = +40 watts and V1 = -28 watts.

My take on the circuit:

I'm assuming since current from the current source is flowing into R1 I can just do P=I2/R to get the power at R1 and for the power at V1 I do P=I*V but I don't get how to find I1 without taking power at V1 and subtracting power at R1. Is that the only way to do it?
also is my assumptions right to get the answers the text got?


texts: verlilog simualte a port pin with switchable pull up

texts:
I want to simulate two avr pins in verilog connected to one wire. Every avr can be in and output and also have the ability to switch its own pull up.

I found the typical way to connect to pins to one wire by something like:

assign io_port  = direction ? a : 1'bz;

where the pin can select the driving state.

But I have no idea how to set the wire to high state, if non of the pins drive active the wire but one or more of the pins have the pull up enabled. I think that there should be more then high/low/tristate/undefined for the wire. But as I know there is nothing like 'pullup'.

As a consequence I have to code all connected pins to a wire with own code. So the logic must be implemented manually and can not use the wire as it is?

I have the following code which do NOT work, because calling multiple times to my connection module will result in ?overwrite? the assignments instead of adding multiple inputs.

As you can see, it feels I have a basic misunderstanding how multiple wires or regs can be added to one wire.

Q1: How to deal with the multiple regs/wires to one wire assignments.
What I did is simply wrong. But how can I "connect" multiple ports to
my wire without writing the complete assignment manually. I simply need a starter tip on how to deal with subsequent adding regs to wires. Maybe my
idea for a wire is wrong?

Q2: How is the standard way to add an pull_up for a device IO-pin.

My source which fails because of the above mentioned problems I already know but can't be solved from myself.

module connection ( input out, input in, input output_enable, input pull_up_enable, inout net, inout pullnet );
    assign pullnet = pull_up_enable ? 1'b1 : 1'bz;
    assign net = output_enable ? out : pullnet;
endmodule

module test4;

wire testwire;

// prepare net checking
initial
    $monitor( "State change for wire %b and pull %b", testwire, pullnet );

wire pullnet;

reg port1_out=0;
reg port1_in=0;
reg port1_output_enable=0;
reg port1_pull_up_enable=0;

reg port2_out=0;
reg port2_in=0;
reg port2_output_enable=0;
reg port2_pull_up_enable=0;

connection conn1( port1_out, port1_in, port1_output_enable, port1_pull_up_enable, testwire, pullnet );
connection conn2( port2_out, port2_in, port2_output_enable, port2_pull_up_enable, testwire, pullnet );

// testing the net
initial begin
    #1 port1_out=1;
    #1 $display("Set enable, expect 1");
    #1 port1_output_enable=1;
    #1 $display("Remove out, expect z");
    #1 port1_output_enable=0;
    #1 $display("set pull up, expect 1");
    #1 port1_pull_up_enable=1;
    #1 $display("unset pull up, expect z");
    #1 port1_pull_up_enable=0;
    #1 $display("-------------");

    // ok, now going with pull up from port 2 and IO from port 1
    #1 $display("set pull up, expect 1");
    #1 port2_pull_up_enable=1;

    #1 $display("set out enable, expect 0");
    #1 port1_out=0;
    #1 port1_output_enable=1;

    #1 $display("################## END ##############");


texts:
I'm designing a 6-channel amplifier which requires one LPF, one HPF, and one gain stage for each channel. I use 4*1 multiplexers for LPF and HPF, and 8*1 multiplexer for gain to control these multiplexers. So I have 7 selection pins for each channel. Now for 6 channels, I need 42 selection pins.

This is simply too much for me. My controller has at most 20 digital outputs. So I think I might need to use something like multiplexing. But the problem is that I can't do sweeping because none of these filters can be left floating.
I can't even think of any solution to google for answers. Can anyone suggest a way?


texts: Can a thyratron be used as a current booster?

texts: I haven't been able to find any decent equations that describe the thyratron cathode-plate current as a function of the anode and grid voltage differences. But in particular, if a thyratron is operated at or above the ignition voltage, how much current in relation to the cathode potential will flow into it and can it be used to draw in more current?


texts: Why does a cap in front of a choke input suply reduce rectifier current? How to calculate optimal value?

texts:
As I was designing the power supply for my tube amp, I was trying to reduce the negative transients of the choke input supply, I tried to add a capacitor in front of it (C1 in the schematic).

It reduced the transients, but also reduced the peak current of the rectifier. I tried experimenting with different values (in the Duncan's PSU designer) and it looks like 1uF is better than other common values.

Rectifier current with the cap 1nF (effectively no cap):

Rectifier current with 1uF:

Rectifier current with 2uF:

I guess the capacitor is compensating for the choke current (power factor?). Anyone knows the proper theory why does this happen? Also, does anyone know a formula that can be used to calculate the optimal capacitance?

I tried this with Multisim too and saw similar results.


texts: Why does my MCU go back? (to the previous instruction)

texts:
I don't know why but I see the same odd behaviour sometimes in the debugger environment. Look at this code (function):

static void I2C_TransferConfig(I2C_HandleTypeDef *hi2c,  uint16_t DevAddress, uint8_t Size, uint32_t Mode, uint32_t Request)
{
  uint32_t tmpreg = 0;

  /* Check the parameters */
  assert_param(IS_I2C_ALL_INSTANCE(hi2c->Instance));
  assert_param(IS_TRANSFER_MODE(Mode));
  assert_param(IS_TRANSFER_REQUEST(Request));

  /* Get the CR2 register value */
  tmpreg = hi2c->Instance->CR2;

  /* clear tmpreg specific bits */
  tmpreg &= (uint32_t)~((uint32_t)(I2C_CR2_SADD | I2C_CR2_NBYTES | I2C_CR2_RELOAD | I2C_CR2_AUTOEND | I2C_CR2_RD_WRN | I2C_CR2_START | I2C_CR2_STOP));

  /* update tmpreg */
  tmpreg |= (uint32_t)(((uint32_t)DevAddress & I2C_CR2_SADD) | (((uint32_t)Size << 16 ) & I2C_CR2_NBYTES) | \
            (uint32_t)Mode | (uint32_t)Request);

  /* update CR2 register */
  hi2c->Instance->CR2 = tmpreg;
}

And take a look at this picture of code in the debugger environment:

When I run it, at first it goes to line 4057 and then it goes to line 4054! Why?

As you can see, both lines are only several variable + several operands! That's all!


texts: Current mirror and differential amplifier problem

texts:
take a look at this circuit:

I have a problem with calculating \$I_{out}\$, or, more likely, understanding how this circuit works. I know that \$I_{out}=I_{C4}-I_{C2}=I_{C1}-I_{C2}\$, but what is the relation between \$I_{C1}\$ and \$I_{C2}\$? In other words: how does the presence of \$V_S\$ and \$R_C\$ influence \$\frac{I_{C1}}{I_{C2}}\$?

We have given: \$V_{CC}=-V_{EE}=15V, \ R_C=1k\Omega, \ V_S=5V, \ I_0=2mA\$


texts: Alternative to easy-driver (or adafruit motor shield ) on breadboard

texts:
I'm up to implementing bipolar stepper drivers  with STEP  and DIRECTION inputs just as like easydriver  and pololu stepper drivers but that on breadboard.Earlier I was using L293D to do that , but it cannot provide phase drive , I researched a bit and found these two instructables which uses L298 (1) and l2619  (2) respectively. However schematics are not very clear and unlikely to those instructable I'll not be using ATtiny2313 , I'll only be using Arduino , as the drivers will have only two inputs (step and dir ), so I believe I can drive four steppers with a single arduino that I can further use with 3D printer.

Is there any other better option for breadboarding a driver with step/dir input ?

(1)-http://www.instructables.com/id/5-stepper-driver/
(2)-http://www.instructables.com/id/45-better-stepper-driver/


texts: Which equipment for electronics should I always have on hand?

texts: This is a supplementary question to the question Which electronics components should I always have on hand?


texts: Use a lithium ion battery from a laptop, for a small project?

texts:
Now laptop batteries are very expensive, however I have a slightly beefy Dell Inspiron 1525 laptop with a half year old battery that works fine.

Other than complete depletion, of which I have heard ruins the life of a battery such as this, the charging will be done by the laptop itself plugged in to at least prevent over/improper charging.

Could I use this type of battery (after regulating to 9/12v if necessary) to draw maximum 100-300mA to allow for a fairly extended battery life of one of my circuits?

I'd hate to waste it, being over a hundred dollars if I recall. Information is scarce on the web and people often just rip out the battery array inside and use them, which I assume is very hard if not impossible to maintain/recharge without the original charger.

I could of course buy some rechargables and put them in to an array, however those are costly (4-12 to have enough voltage in series) and I do not even think (possibly in the future I will obtain) a "9V PP3 L-ion" battery exists, which could be helpful.


texts: How to design a 3-phase resistive load bank?

texts:
We are trying to design a 3-phase resitive load bank to test some step up transformers. We are receiving 3-phase 208v and stepping up to 3-phase 600V with 3-step up transformers wired in delta. Its a floating system  Each step up transformer is capable of 800VA.

Q. How do you wire up the load with resistors, to test each transformer at full load? A picture or diagram would be helpful.


texts:
I am quite new to the Arduino business and up until now managed to create a Hexapod robot from a kit based on the Arduino Mega 2560, add Computer Vision and let him crawl around to find target objects. Now I want to destroy the target (in this case... Clover). So I just bought a laser diode with 200mW optical power, 3-5V input voltage and the additional info "<300mA" current (which would mean an overall consumption of 900mW at 3V?). It has its own build in current regulator as it seems.
The robot is powered by 2x3,7V in series (=7,4V) batteries.
Assuming I measured the actual power consumption and total current of the laser, I have trouble determining:

which transistor to use for switching the laser with an Arduino pin (40mA max current)
how to regulate the Collector voltage to 5V from the 7,4V source

I understand that I first have to measure the current of the laser to determine the Ic for the transistor. After that, I select the transistor and calcuate the needed Ib (<40mA). The result would be the right Base resistor put between the Pin and the Base. If this is the right way to do it, switching is now possible.
Now the laser power suplly:
 - Should I use a voltage regulator for 5V output? I am not realy familiar how these parts work. Do I only select one which has an input voltage rating around 7,4V, outputs 5V and is sufficient for the desired Ic current? Do I need a heat sink?

If the voltage redulator is the right choice, I would

connect 7,4V to the Input of the regulator
connect GND to GND of the regulator
connect Output of the regulator to the laser Input
connect the Output of the laser to the collector of the transistor
the emitter of the transistor will connect to GND again

Is this the right way?
How do I calculate the resistor, transistor and regulator rating right for the expected voltage decrease when the batteries run low over time? As I understand it, Ib will decrease and so will Ic. I should calcuate Ib in reference to Ic, so that Ic is >= the laser current drain even on 6,5V power supply and pin voltage of what? 4,5V?

Thank you in advance for your help!
Regards
Sebastian


texts:
I've started learning about transistors in my class and am having a hard time understanding how to analyze circuits with them. I'm not sure how to calculate current changes around them or how they amplify current. I'm trying to find V_out in the following but don't know where to begin:

V_in in this circuit is equal to 20 V DC


texts:
I am driving a digital pin with a 10Mhz signal. At the pin, the signal's rise time is slewed to 35us such that the signal is no longer a pulse but a triangular waveform that does not reach the full output level of 1.8V. I have a source termination resistor on the driving source. However, this source is a couple of feet away and the trace is not a controlled 50Ohms. Would making this trace a controlled 50hms helped with the slewing of the rising time? Does line termination help or is this only to reduce reflections?
Also,if 50 ohms would help, is it better to have a discontinous 50 ohms or none at all? I have some transitions on the trace that I cannot make 50 ohms.


texts: How to connect Dc motor to Diode transistor logic

texts: So I have a nand gate using DTL (diode transistor Logic) but i don't know how to connect my DC motor to nand gate logic , I tried to put my DC motor to the output of DTL but it isn't working, may you recommend or advice something?


texts: I am very inexperienced in electronics, so far I have just done real simple stuff with an arduino. I have a Nema17 (driven through a L293D) stepper motor which has a rated voltage of 12V and current of 0.4A. Now, my understanding of current and voltage is that the current solely depends on the voltage of the power supply and resistance of the motor. Therefore the motor draws a certain amount for a specific voltage. Now, when I connect my power supply to my circuit I only get to 0.4A or anywhere near that by setting to voltage to about 20V which exceeds the 12V rated voltage of the motor. Am I simply understanding this in a wrong way or do I somehow need to convert the voltage to 12V without the current being affected?


texts: Should I assign currents to voltage sources in my circuit analysis

texts:
Mortals! I apologize if my question may seem, foolish, but I have a need of understanding a process in analyzing circuits. You see, when we are looking at resistors (non-sense, my lightning never meets such "resistance") in a circuit, and trying to solve for some unknown variable, we often times assign currents to the resistors, such that they can be used in our KCL equations. However, I am wondering if it is wise, unwise, or irrelevant, to assign such currents to voltage sources. Let me give you humans an example. http://imgur.com/xPZvmWY

You see, in the above example, my KCL equations for a node would be different if I assigned currents to the 2 voltage sources shown. I know that, since voltage sources do not supply current, they do not really have a current "of their own," and thus, any current running through them would be one of the currents drawn for the resistors or from a current source. However, am I allowed to do this and still be okay in my analysis. MORTALS, I hope you are able to provide me an answer, as Kratos draws near, and I have not perfectly understood the nature of this power coming out of my hands. If I am to destroy him, I will need to know the answers!


texts: Uneven current distribution in center-tap transformer secondary winding of LLC resonant converter at low load

texts:
I'm trying to design an 24V 50W LLC resonant converter with a resonance frequency of 250kHz.
I've run into an issue with the center-tapped transformer that i can't quite find a reason for though.

For some reason one half-period (When M1 is open) barely transfers any current from the primary side to the secondary side at light loads. At heavy loads this seems to be much less of an issue.

If anyone can explain what's going on, or link some articles explaining it, i'd be very grateful.

I have attached any relevant waveforms i could think of, but the main ones are the 2 diode currents at the bottom (I(D1) & I(D2)). Also V6 is supposed to be a start-up pulse that will turn off after a while, but right now it's just a DC source for the gate-driver.

The circuit

Waveforms at light load(100Ohms)

Waveforms at heavier load(10Ohms) - here there's an issue of D1 conducting before D2 is at 0A which also shouldn't happen as far as i know. This issue also seems to disappear at even heavier loads, which is more than this power supply is supposed to deliver though.

Ideal waveforms at resonance
(from: https://powersimtech.com/drive/uploads/2018/04/Designing-LLC-resonant-converter-TI-slup263.pdf)

Any help or comments would be greatly appreciated.


texts:
How to find the orientation of  DQ axis of rotor and stator in induction motor using iq and Id currents?

Particularly in foc of im, I have measurement of stator ia, ib, ic and rotor omega. However, rotor omega is not useful since rotor field and rotor spin asynchronously. At this stage, I can do Clark transform now. But how to get I'd and iq next?

Articles for these are not easy to obtain. It would be great if someone could link to reference articles.


texts: Confusion in feedback for switchmode dc/dc converter

texts:
I have a slight confusion in how the feedback pin works. The "\$V_{ref} \times (1 + R_1 / R_2)\$" seems like a shortcut to me, and I have trouble understanding how to feed a voltage in to it, to say make a tracking pre-regulator to always maintain +2 volts.

The circuit I am designing starts fairly simple, it looks roughly like this:

From what I understand, you have 5V running past D1 and feeding 5V in to the resistive divider (at very start), making $$\frac{10k}{84.5k+10k}\times5V=0.52V$$

That is fed in to the error amplifier, of which the reference voltage from datasheet I assume is 1.265V

And so it tries to bring 0.52->1.265V, making $$5V\times\frac{1.265}{0.52}=12V$$

The above is new to me and I had discovered the correlation while writing it. Is that how the error amplifier works?

If I want say...7V, I would cause the voltage to the FB pin to be (7/5) times lower than 1.265V so it will work itself up to 7V as my formula above? (excuse that math if minor mistake, but more or less using the difference in FB and Vref to multiply the input voltage).


texts: What is the relation between the control voltage and resulting pwm in a voltage-mode control system for DC-DC converters?

texts:
I'm currently learning about negative feedback and voltage mode control for various DC-DC converters. I'm very confused about how the control voltage changes the pwm signal, along with how the reference voltage and sensor gain are chosen.
The pwm generator works by comparing the input control voltage to a ramp voltage. If the control voltage is greater than the ramp voltage the output is high and if it is lower than the ramp voltage the output is low. This results in a series of square pulses as shown below:

Let's say we have the following buck converter with an output voltage of 15V:

Why is a 5V reference voltage selected? Can it be anything? The sensor gain for this problem is selected to be 1/3. Is it 1/3 because we want the nominal output voltage to be equal to the reference voltage?
I am quite lost from the part after the error comparator. Let's say that the voltage being fed-back is exactly 5V so Ve = 5-5 = 0V. If Ve is 0, how is the pwm generator able to generate any pulse signal to drive the transistor since the control voltage will be 0 coming out of the compensator?
Also, how is the ramp voltage value chosen? I would imagine that it would depend on the gain of the compensator since if the gain is too large, then the control voltage would always be higher than the ramp voltage.


texts:
I'm trying to sample a(low frequency) signal I'm producing using Microchip's PIC16F1783 (which has an internal DAC).
I connect its output and ground my PC's audio jack (GND+Right Channel).
I then watch the waveform using an application which is basically a scope for audio signals.
The strange thing is that the waveform doesn't change whether I plug the GND or not!
Does it mean that the I can't really trust the results I see?
Is there another (cheap) way for me to sample the output of the PIC?


texts: How to take z-transform of a function with an absolute exponent value?

texts:
Can you help me find the z-transform of the impulse response below:

$$h(n) = (\frac{1}{2})^{|n-1|} + (\frac{1}{2})^{|n|} $$

I know the z-transform of
 $$(\frac{1}{2})^{n}$$
 is equal to:
 $$(\frac{z}{z-b})$$


texts:
everyone.

I would like to ask you about the difference between Power On Reset[POR]  and other Resets because in PIC18 controller datasheet i have seen a statement like:

Note 1: The RTCCFG register is only affected by a POR.

The RealTime Clock  is affected by only POR it says.

What are the conditions in which the POR can happen to embedded systems ?

And I trust Watch dog reset and others just make the code run again from start address of program memory.


texts:
How to calculate the required storage capacity of a data logger given the measurement time sampling rate and resolution?

I want to log two voltages at 1Hz rate for 3 months continuously  and looking for a cheap data logger for this purpose. But most of them have not enough storage.


texts: Blinking an LED once when a slide pot is pulled to ~zero ohms

texts:
I am developing a little circuit to control a servo linear actuator that is used to control fine injection onto a microscopy set-up. I am using a 555 circuit (see below) to generate the PPM signal required to control the actuator position with a couple of slide pots.

simulate this circuit – Schematic created using CircuitLab

It contains three pots, a "coarse" slide pot to control the servo position, a "fine" slide pot (with audio taper) and a pot that sets the range of the "Fine" pot. The user will preset the coarse and range pots and then, at a particular time-point, gradually slide the fine pot over its full range until it reaches zero resistance. When it reaches zero resistance I would like an LED, positioned close to the microscope, to give a brief flash (~35ms). This way we can align the moment of injection with the video recording of our microscope slide. Does anyone have an idea how to add that to this circuit?

Thanks!


texts: Using diodes to channel battery charging current

texts:
I have a setup with Solar PV, battery, inverter, and AC load. Between the battery and inverter I have connected a custom circuit with DC power/energy/charge measurement, and a relay.

Problem is, circuit traces are limited to 4.5A, and the inverter charging current can go as high as 10A (and even if the amperage wasn't an issue, the circuit won't measure reverse current anyway).

To get around this, I am planning to connect two branches between the battery and inverter with diodes to control where current flows, like this:

(Not shown is the MPPT solar charger, and the back-up AC source to the inverter).

Normally, when solar is charging the battery, current will flow through my measurement/control circuit, to the inverter, and on to the load. When I switch on the backup source to the inverter to charge the battery, the higher current will bypass my measurement/control circuit.

Assuming I can find the right diodes, is there anything wrong with this setup? Anything I'm not considering?


texts: How to find the value of alpha in this curcuit?

texts:
I have tried to solve this way but i am not sure how to proceed from here:

[![tried solution][2]][2]


texts: STM32F407 - ADC in Scan mode setting overrun bit

texts:
I want to read 4 ADC channels in continuous scan mode.

I am using ADC interrupt to read from the ADC data register.

Here is my initialization:

  hadc3.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV2;
  hadc3.Init.Resolution = ADC_RESOLUTION_12B;
  hadc3.Init.ScanConvMode = ENABLE;
  hadc3.Init.ContinuousConvMode = ENABLE;
  hadc3.Init.DiscontinuousConvMode = DISABLE;
  hadc3.Init.ExternalTrigConvEdge =
  ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc3.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc3.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc3.Init.NbrOfConversion = 4;
  hadc3.Init.DMAContinuousRequests = DISABLE;
  hadc3.Init.EOCSelection = ADC_EOC_SINGLE_CONV;

I have set a breakpoint in the interrupt handler.
As soon as I start debugging, the execution goes into the interrupt handler and the OVR bit is found to be set in the status register.

To proceed with the normal execution I have to re-trigger the ADC via this line of code:

void HAL_ADC_ErrorCallback(ADC_HandleTypeDef* hadc)
{
    hadc->Instance->CR2 |= (uint32_t)ADC_CR2_SWSTART;
}

in the ErrorCallback() function.

The readings are coming fine but I cannot understand why the overrun bit is set at every cycle of conversion.


texts:
I have a cheap UHF RFID antenna (9dB) like this :

How does this kind of antenna work?
There is no dipole? Why does the "L" at the bottom left of the disc have finer passages than others? I can not find any information on the web about this type of antenna and the physical rules used.


texts: Why is an attenuator placed on the scope end and not the PCB end?

texts:
I've noticed when adding an external attenuator between PCB and the scope (1MOhm) that it is placed in this manner:

PCB -> SMA Socket -> SMA Cable Plug -> SMA Attenuator -> SMA-to-BNC -> Scope

Why is it bad practice to use:

PCB -> SMA Socket -> SMA Attenuator -> SMA Cable Plug -> SMA-to-BNC -> Scope

I assume this is due to an increase in reflection of the signal when putting the attenuator first.

When taking high voltage measurements (>400V; where limit of SMA is 400V) a 7/16 DIN connector is more ideal (limit 1400Vrms). Is it acceptable for the following to be used:

PCB -> 7/16 Socket -> 7/16 Attenuator -> 7/16-to-N -> N-to-SMA -> SMA Cable -> SMA Attenuator (0dB) -> SMA-to-BNC -> Scope


texts: Sine wave PWM: which is better analog or digital?

texts:
I'm designing a low power DC/AC sinewave inverter and I have 2 choices for the pulse width modulation :

Generating SPWM using an AVR microcontroller timers/counters.
Generating the waveform using a bubba oscillator with square wave.

I know that the 4-section bubba oscillator has good stability because it has high rate of change of phase with frequency but I don't know if it's suitable for 50 Hz operation  I think it's better at lower frequencies(or not?))


texts:
I've an ATX power supply and I'm trying to charge my Nexus 5 phone.
I connected USB female (from an old PC) to +5V and GND and shorted the DATA+ and DATA-.
My multimeter shows 0.400A when I connect my phone.
I tried to put 1k ohm resistor (that's what I found) and then it showed 0.600A but my phone shows around 0.200A on both.
The original charger output is 1.2A and on the phone it shows 0.800A.
I can't find what's the problem, my ATX PSU can give up to 36A on the +5V (Red wire) rail and my phone won't draw more than 0.200-0.300A.
What am I missing?


texts:
Using a multimeter's diode setting I see that both the base-emitter and base-collector voltages of a transistor in a powered down circuit are 0.67Vm, while reversing the probes shows OL. Voltage across C-E is 1.6, probably due to it being in the circuit and other components interfere.

How much confidence can I have that the transistor is not bad? I understand that desoldering it and then measuring would be a better indicator of its state.

For context, I have an amplifier PCB with 6 transistors on it, it produces a low output volume, and was told that one of the transistors on it may be malfunctioning and I should try desoldering them to see if anything improves.

UPDATE:
TR1, TR2, TR3 and TR4 are identical NPN, and have 0.67V across both B-E and B-C and LO when inverted.

TR5 (BC558 PNP) has 0.73V and 0.7V on B-E and B-C and OL when reversed.

TR6 (BC548 NPN) has 0.69 V on both on forward, 0L on B-C but 1.08V on B-E when reversed.

TR7 is a digital transistor, which from what I understand is an IC and cannot be measured as a BJT.


texts: Combining 2 NOT / BUFFER gate outputs for same input to increase current output

texts:
To drive a RLC circuit by pulsing at a frequency close to 1MHz, I would like to use  a schmitt trigger inverter gate (SN74AC14) / buffer (SN74LVC2G17) in between the uC pin and RLC circuit for higher current output (50mA). Since, they have a voltage drop at pins at their maximum current output. I was wondering, if I could reduce the drop by combining two output gates powered by single input.

Of course, I could foresee that there will be a short circuit involved during mismatch of the gates during the transition phases of the inverter / buffer circuit. But since they are from the same chip, I was having the feeling that the would have very similar switching / propagation characteristics and even if they mismatch, that would be for a very short time (<10ns?)

My questions are:
(1) Is this mismatch negligible meaning would the thermal model allow this short circuit for small time at a frequency 1MHz?
(2) Would this configuration still reduce the voltage drop on my output without compromising the max. limits of the component?
(3) Is there other consequences that I have missed?

Thanks!


texts:
I have 5 states : idle, state1, state2, state3, state4. I sometimes need to go to idle according to my design, and when I return from idle, I don't want to start from beginning, I want to start from the last state I was in. I thought about doing this in idle as

if (statereg = 2) then
my_state <= state2;
end if;

Is this a good approach or won't work? Are there better ways? How do VHDL gurus handle this kind of situation, what do we call this method in VHDL, does it have a name?


texts: Matlab code to derive the overall difference equation relating two systems

texts:
Using Matlab, I am trying to:

Get the overall difference equation relating to z[n] to x[n] and check if
z[n] = x[n] is a valid solution to the overall difference equation

I have two signals given by the differential equations:

z[n] + az[n−N] = y[n]
y[n] = x[n] + ax[n−N]

Where x[n] is an uncorrupted speech signal,  which has been delayed by N samples and added back in with its amplitude decreased by a <1. Also, N = 1000, and the echo amplitude,a = 0.5.

What I have at this point:

% z[n] + az[n - N] = y[n]
% y[n] = x[n] + ax[n - N]

% Replacing:
% z[n] + az[n - N] = x[n] + a[n - N]
% z[n] = x[n] + a[n - N] - az[n - N]

syms z(n) % z[n] = dz/dn
syms x(n)

ode = diff(z,n) == ??

But I am stuck in how should I add the x[n] part.

How do I show these equations are equivalent?

As requested, I am adding more information about this overall question:

I am using a speech that was recorded with a sampling rate of 8192 Hz (I can hear the speech by typing sound(y,8192). The signal y[n], represented by the vector y, is of the form:

y[n] = x[n] + ax[n−N] (1)

where x[n] is the uncorrupted speech signal, which has been delayed by N samples and added back in with its amplitude decreased by a <1. This is a reasonable model for an echo resulting from the signal reflecting off of an absorbing surface like a wall.

For the problems in this exercise, I am using the value of the echo time, N= 1000, and the echo amplitude , a= 0.5.

My first task and also my question here was to remove the echo by linear filtering. Since the echo can be represented by a linear system of the form Eq. (1) I determined and plotted the impulse response of the echo system Eq. (1). I stored this impulse response in the vector he for 0≤n≤1000.

Now I need to consider an echo removal system described by the difference equation

z[n] +az[n−N] = y[n] (2)

where y[n] is the input and z[n] is the output which has the echo removed. I need to derive the overall difference equation relating z[n] to x[n] and check if z[n] =x[n] is a valid solution to the overall difference equation.

My whole code at this point is:

% Testing the input:
sound(y,8192)

    %% Part A:
    % create the impulse response
    M = 1; % MATLAB indexing offset
    N = 1000;
    h = zeros(1001,1);
    h(M+0) = 1;
    h(M+1000) = 1;
    stem(h);
    he = h;

    %% Part B:
    % z[n] + az[n - N] = y[n]
    % y[n] = x[n] + ax[n - N]

    % Replacing:
    % z[n] + az[n - N] = x[n] + a[n - N]
    % z[n] = x[n] + a[n - N] - az[n - N]

    syms z(n) % z[n] = dz/dn
    syms x(n)

    ode = diff(z,n) ==


texts: I will switch an ac load with a triac. I am providing a dc voltage of 5V on the gate of first Triac and 0V on the gate of second Triac. In the first picture the triac is working and the switch is closed but in the second picture the triac is still closed despite providing 5V to its gate. I don't understand why?


texts: How can I attach an analog to digital converter to a guitar

texts:
I want to modify an electric guitar to add an ADC and microcontroller to drive some LEDs for fancy effects that follow music.

Since typical output levels of pickups are about 100mV, I was thinking of adding an op-amp circuit in parallel to the output of the guitar, independent of the any other amps the user may connect.

Since the power generated by the pickups is so low, I am not sure of they can drive both the op-amp and the other amplifiers? Do I have to provide pre-amplification to the guitar output so it can still be used as an instrument?

EDIT: I am not trying to power up form string vibrations. I foresee battery, I am only concerned about the loading of the pickups, "losing" the signal they create in the process. I want it to be playable as usual.


texts:
Consider two Arduinos (ATmega328P), with pins 2 connected for half-duplex communication (e.g. using SoftwareSerialWithHalfDuplex):

Both Arduinos may be transmitting at the same time, either for logic reasons, or if something is wrong. In this case, one Arduino may set pin 2 to high, the other Arduino may set it to low. The result is a short circuit. To limit the current to 5mA, I could add a 1kΩ resistor:

Is that the preferred solution? Am I missing something?


texts: My CRC8 is dysfunctional and I'm not sure why!

texts:
So I'm interfacing an arduino with a Melexis temperature sensor, and it's going okay--aside from the fact that I can't seem to get the CRC check to work.

I've gotten read operations to complete successfully (although my software ignores the packet error code) but I have tried a lot of implementations of CRC8 to check the PEC byte to no avail.  The code block I am using now came from OneWire:

uint8_t OneWire::crc8(const uint8_t *addr, uint8_t len)
{
    uint8_t crc = 0;

    while (len--) {
        uint8_t inbyte = *addr++;
        for (uint8_t i = 8; i; i--) {
            uint8_t mix = (crc ^ inbyte) & 0x01;
            crc >>= 1;
            if (mix) crc ^= 0x8C;
            inbyte >>= 1;
        }
    }
    return crc;
}

I rewrote it to consider just the one byte:

int smbCRC(int message) {

    uint8_t crc = 0;

  uint8_t inbyte = message & 0xFF;
  for (uint8_t i = 8; i; i--) {
    uint8_t mix = (crc ^ inbyte) & 0x01;
    crc >>= 1;
    if (mix) crc ^= 0x8C;
    inbyte >>= 1;
  }

    return crc;
}

But its CRC does not match that of the MLX datasheet (Figure 8 from here for example).  When I print an int with its CRC8 like so:

int message = 0x3aD2;
lcd.print(String(message,HEX) + " " + String(smbCRC(message),HEX));

I get back "3ad2 eb", though the datasheet says the correct PEC is 0x30.  Where am I going wrong?  It seems like this could be caused by a bad implementation of CRC or bad assumptions on my part about the CRC input, and I'm not sure where to start troubleshooting.


texts: Can BLE transactions be encrypted without pairing?

texts: The way I understand BLE specs is that the only way the communication between 2 BLE device to be encrypted is that they need to be paired. Is that right?


texts:
I was just looking at the schematic shown below for a DAC.  Anyone know why the iron core inductor (L1 circled in red) is included?  My guess is that it's used to ramp the power up/down when powering up/down the unit to help prevent the common "popping" sound that occurs in speakers, but I'm far from certain of that.
Additionally, I'm confused by the units of the inductor.  "2500" what?  Anyone know?


texts: Can you help me identify the antenna? Looking to add External Antenna

texts: I'm looking to add an external antenna and I want to find out I add the antenna using a Mini PCI U.FL to RP-SMA Antenna WiFi Cable Signal Connector Network Adapter I got off of ebay to a Trendnet Range Extender.  I'm a total newb and need help identifying what #1 is, what #2 is, and really what else I might need to know to get this working.  Thanks!!!!]2


texts: I have a potentiometer for the volume control in my electric guitar. My multimeter reads 485K ohms on a 500K pot putting my test leads on each outside lug, which is fine I believe. When I put a test lead on the wiper and one on an outside lug my multimeter just says 1 as I turn the knob and also switch to different ohm ranges on my meter. What does this mean?


texts:
I'm looking to build my own power button for my computer.

Most motherboards have a pair of PWR_SW pins that your case power button typically attaches to via two female pin connector wires (I don't know the correct term). This is the part I plan on replacing. Attached to some button like this for example: https://www.adafruit.com/product/558

I'm also aware you can short the two pins by touching them both at once with a screwdriver and most motherboards will just turn on– is this basically what a switch / button does? If I attach two wires to the button above and press the button– I'm guessing that essentially does what the screwdriver does and completes the circuit– turning the computer on?


texts: Finding the impulse response from the integral

texts:
I'm trying to solve the part (a) of the following:

I know that:
$$
y(t) = \int_0^1 \! \delta (t-\lambda ) \mathrm{d}\lambda
$$

But I'm not sure how to proceed from that.


texts: Why for an inductor part is the RMS current rating is specified at 20°C rise and 40°C rise?

texts:
The inductor part from coilcraft (https://www.mouser.in/datasheet/2/597/xal4000-270751.pdf), RMS current rating  is specified for 20°C rise and 40°C rise. Is there any specific reason? In note 6 it is mentioned as the current rising from 25°C (ambient temp).

Also is only 25°C meant ambient temperature or any temperature between 20°C and 40°C meant to be ambient temp range?

so while designing which one they consider whether current rating of 20°C rise or 40°C rise temp?


texts:
I am new to the world of audio amplifiers however i am quickly trying to learn.  I have built a simple circuit using a circuit based on what I read in the database.  The circuit works however there is a lot of noise and the sound quality quickly decreases at higher volumes however that may just be the speaker I am using. I am sure I need additional filtering capacitors however after looking at several example circuits I am confused about what where these capacitors should be and what values they should have.  Please help me find a way to improve the audio quality to a decent level.  Additionally I need to remove radio signals that are interfering with the playing sound.  I am running the lm386 on 6 volts.

What value speaker would be ideal for this use?
What capacitors do I want between my power rails?
What capacitors do I want between my inputs?

Here is my current circuit


texts: what is the diffrence between hid and cdc usb device?

texts: I was not able to get the difference after much googling.I am a newbie in microcontrollers and doing a project on Temperature controlled fan using LabVIEW and PIC18F4550. I need to know how communication takes place between the two. I also need to know that if USB 2.0 is a half-duplex system then how will I achieve real-time control of speed of the fan which depends on the temperature.How will the PIC be used a CDC or HID?


texts:
What software does porous silicon simulations?
I didn't find it in my searches. The closest was TCAD Atlas, but it gives more prominence to cmos. I would like to know if there is (names) software that makes porous silicon simulations: porous size, cavities, filling of chemical elements, reactions etc.


texts:
There has been a fairly wide ranging discussion as to why it is difficult to combine memory / CPU logic on the same die (yield issue compounding, different processes, different clock-frequency, increasing testing requirements etc).

It seems that the latest NVDA GPU chips have >10GB of on-chip memory. These chips are also produced at leading edge nodes (i.e. 10nm below, TSMC process). So my question is: why does the memory / logic same die combination seem to work better for GPUs versus CPUs?


texts:
What are the final steps to arrive at the transfer function for this RCL circuit?
I am attempting to arrive at this transfer function $$\dfrac{V_o(s)}{V_i(s)}=\dfrac{sL}{CL(R_1+R_2)s^2+(R_1R_2C+L)s+R_1}$$ for the following RCL circuit.

My initial problem was not knowing the correct steps to take to get from the circuit to the final TF, using the complex impedance method.
So, I have now used the KVL method, which has got me to a final transfer function. But, not the one that I desire.
$$\dfrac{I_2(s)}{V_1(s)}=\dfrac{s^2CL}{CL(R_1+R_2)s^2+(R_1R_2C+L)s+R_1}$$
Therefore, I would just like to know whether or not the last remaining step is to take \$V_o = I_2(s)Z_c\$, where \$Z_c = \frac{1}{sC}\$ and therefore multiply \$I_2(s)\$ by \$\frac{1}{sC}\$ and thus reduce the numerator from \$s^2CL\$ to \$sL\$
So, these are the steps taken using KVL:
Loop 1:
$$V_1(s) - I_1(s)R_1 - L(sI_1(s)-sI_2(s)) = 0$$
$$I_1(s)(R_1 + sL)- sLI_2(s) = V_1(s)\tag{1}$$
Loop 2:
$$I_2(s)R_2 + \frac{I_2(s)}{sC} + L(sI_2(s)-sI_1(s)) = 0$$
$$-sLI_1(s)+I_2(s)(sL+R_2+\frac{1}{sC}) = 0\tag{2}$$
From (2) I get that \$I_1\$
$$I_1=I_2(s)(sL+R_2+\frac{1}{sC})\frac{1}{sL}$$
$$I_1=I_2(s)(1+\frac{R_2}{sL}+\frac{1}{s^2CL})\tag{3}$$
which, when substituted into (1), gives
$$I_2(s)(1+\frac{R_2}{sL}+\frac{1}{s^2CL})(sL+R_1) - sLI_2(s) = V_1(s)\tag{4}$$
Multiplying through by \$(sL+R_1)\$
$$I_2(s)(sL+\frac{sLR_2}{sL}+\frac{sL}{s^2CL}+R_1+\frac{R_1R_2}{sL}+\frac{R_1}{s^2CL})-sLI_2(s)= V_1(s)\tag{5}$$
Multiplying through by \$I_2(s)\$
$$sLI_2(s)+\frac{sLR_2}{sL}I_2(s)+\frac{sL}{s^2CL}I_2(s)+R_1I_2(s)+\frac{R_1R_2}{sL}I_2(s)+\frac{R_1}{s^2CL}I_2(s)-sLI_2(s)= V_1(s)\tag{6}$$
cancelling out like terms, I get
$$\frac{sLR_2}{sL}I_2(s)+\frac{sL}{s^2CL}I_2(s)+R_1I_2(s)+\frac{R_1R_2}{sL}I_2(s)+\frac{R_1}{s^2CL}I_2(s)= V_1(s)$$
factoring out \$I_2(s)\$, I get
$$I_2(s)(\frac{R_1}{s^2CL}+\frac{R_1R_2}{sL}+\frac{1}{sC}+R_1+R_2)= V_1(s)\tag{7}$$
obtaining a common denominator, I get the following
$$I_2(s)(\frac{R_1}{s^2CL}+\frac{sR_1R_2C+sL}{s^2CL}+R_1+R_2)= V_1(s)\tag{8}$$
$$I_2(s)(\frac{R_1}{s^2CL}+\frac{sR_1R_2C+sL+s^2CL(R_1+R_2)}{s^2CL})= V_1(s)\tag{9}$$
factoring out the \$1/s^2CL\$, I get
$$\frac{I_2(s)}{s^2CL}(R_1+sR_1R_2C+sL+s^2CL(R_1+R_2)= V_1(s)\tag{10}$$
Rearranging in terms of \$I_2(s)\$ and \$V_1(s)\$, I get
$$\dfrac{I_2(s)}{V_1(s)}=\dfrac{s^2CL}{CL(R_1+R_2)s^2+(R_1R_2C+L)s+R_1}\tag{11}$$
So, is the last step to take \$V_o = I_2(s)Z_c\$, where \$Z_c = \frac{1}{sC}\$ and therefore multiply \$I_2(s)\$ by \$\frac{1}{sC}\$ whereby reducing the numerator from \$s^2CL\$ to \$sL\$?


texts: How to position adjacent transformers so they don't interfere?

texts:
Using a couple of 240V mains step down transformers, undecided whether to use E/I laminated or toroidal, one 22VA the other 7VA. How to mount them in the case, so that they're not affected by each others magnetic fields?

This is unless I can find one ready made with separate secondaries of 22-0-22 and 7-0-7.


texts: RMS current of a circuit driven by a white noise voltage source

texts:
Note: I am an applied mathematician, not an electrical engineer, so apologies if this comes across as silly. I am analyzing the following circuit as part of some modeling related to energy storage systems:

simulate this circuit – Schematic created using CircuitLab

Where the voltage source is gaussian white noise (hence my use of "mixed Hz" in the schematic software this site uses). This means that the fourier transform of the voltage waveform is flat across all frequencies.

I was wondering if, given the rms Voltage, I could calculate an "equivalent capacitative reactance" \$X_{c,eq}\$ such that:

$$I_{rms} = \frac{V_{rms}}{X_{c,eq}}$$

I've heard of Johnson-Nyquist noise and kTC noise for capacitors, but I don't see how temperature applies here (since they are modelling a physical phenomena).


texts: Programmable routing of VCC and GND (up to 500mA)

texts:
So... I'm designing a kind of retro CPU testbed (Z80, 6502...), akin to a generic programmer such as the xgecu. I have an Atmega2560 as my microcontroller, and a 40 pin ZIF socket. All ZIF pins are redirected to known I/O MCU pins. I'll then have a configurable REPL working via Serial/USB.
My problem is on VCC/GND configuration. Not all CPUs have the same VCC/GND layout, and I'm not confortable with the Atmega2560 source/sinking the necessary current through its IO pins (although current CMOS versions of these CPUs do have very little consumption).
Besides a rail of 160 jumpers (to select VCC/GND for each possible pin), or an array of 80 transistors, what would be the most elegant way of arbitrary routing source/sinking paths in a programmable fashion?


texts: Rms value of rectified output from a half wave rectifier

texts:
The rms value of an alternating quantity which is the input to a half wave rectifier is Imax divided by square root of two.

Then the rms value of output should be IMAX by 2*sqrt two. But it Isht given every where that it is IMAX by two. Can somebody help me?


texts: How frequency is modulated in FM transmitter circuit

texts:
I am new to looking at FM transmitter and have a few questions regarding the FM Transmitter circuit below.  Please break down your answers as simple as possible as I am not as well versed in circuits at this point. Thank you all in advance for your help and guidance.

1.I understand that the base current effects the collector current but I don't understand how the frequency from the Tank circuit changes based on the signal going to the base of the transistor.  Please break down in simple terms how the frequency from the tank circuit at the collector is changed to a higher or lower frequency based on the signal going to the base of the transistor. Are the 2 signals combined somehow, sorry I really don't understand how this happens.

2.My understanding is that the capacitor across the transistor C2 is for signal feedback. Is this correct? Why is signal feedback needed?  Does this feedback signal need to be in phase with the tank circuit? If so, how do you know that simply placing a capacitor across the transistor will achieve an in phase feedback signal?

3.Does C1 and C3 effect the frequency of the signal going to the antenna? If so, please breakdown how they effect the frequency going to the antenna. Also, does C1 and C3 serve another purpose in this circuit? Please explain what will happen in the circuit if they were not there.

4.Please explain what is the purpose of R2 and R1. Please explain what will happen in the circuit if they were not there.


texts:
Trying to figure out how to design this with decent precision but having trouble getting this started.  I've worked with 555's before but not for precise counting that can be modified in steps.

I'm trying to come up with a 5 volt system that accurately pulses an output of +5v that is measured and displayed in pulses per minute, or beats per minute, between 60 and 240.  The BPM should be adjustable by 2 momentary buttons which will step the timer +1 and -1.  It would also be great if there could also be a second set of buttons for +10 and -10 steps.

Is using a 555 timer the wrong way about this?  Is there something more precise I can use to reference the gating? Is there already an IC out there that can do this on its own and do a compare to calculate the maths?

Apologies for not posting what I have so far.  I'm on version 80-something on my breadboard and nothing has been working accurately so far.  I also want to stay away from having to program roms and stick with discrete IC's.  Again, I DO NOT want to be programming chips.

I think what I'm after might be a function generator with a frequency counter, but I don't know if that's the best way to go.


texts:
I've build a LED strip controller using NodeMCU and a transistor STP16NF06FP according to the schematic below:

LEDs were powered with 24 V power supply and I want to regulate it by changing the voltage using PWM on mcu. So for the simplicity's sake I output 255 on PWM pin D5 and the voltage output is ~16 V instead of ~24V also LEDs are flickering.

When I power NodeMCU from USB instead of voltage stabiliser then it is not flickering, but the voltages remain the same.

How to get rid of flickering and get a higher voltages?  Max power output from power supply is 0.5 A and it is enought to power LEDs.

When I mount IFRZ44N instead of STP I get ~16 V but the LEDs barely light.
With TIP120 there is no flickering but the output is ~16.7 V (so still a voltage drop, I wanted to replace to MOSTFET as these should have less voltage drop than NPN).

Here is the code for NodeMCU https://bitbucket.org/mdczaplicki/smarthome/src/master/node_mcu/node_mcu.ino


texts: Working of transistor in an Opamp log amplifier..?

texts:
In the figure it could also be possible to connect the transistor Q1 as a diode by shorting its collector with its base ..but instead it is done by keeping both base and collector at ground...
The text have to say that if it would be connected the other way(i.e by shorting collector and base )then the base current would have caused an error ( Base current error ) .
Which type of error is the author talking about..?
Why and how does the error manifest itself...?

Please help!


texts: What is the net charge held in a battery?

texts: I assume that the net charge held in a battery is always 0. I.e. the total charge held in the positive terminal of the battery is always equal to the total charge held in the negative terminal. Is this correct? And either way please can you explain why?


texts: How to configure Atmel SAM D20 for internal 48MHz clock source?

texts:
I try to run a Atmel SAM D20 MCU at 48MHz using the internal oscillator (OCM8M) and the digital frequency locked loop (DFLL48M). All I achieve is a deadlock of the processor, even I use a simple "Atmel Start" project.

I searched hard, but I found no examples or even descriptions how to achieve this. Everything references to some other source, but no source explains the process in detail.

What I try to do is this:

Which is the correct way to put the CPU into internal 48MHz mode?

Are there any detailed examples or explanations somewhere? Did I miss an important source?

Any help is welcome. Any code examples are welcome in any language.


texts: PIR Sensor + LEDs with no additional Microcontroller

texts:
I'm thinking of building a project that would only include PIR sensors and LEDs.

Could I use a PIR sensor like this one, https://www.adafruit.com/products/189, to power 8 LEDs or would those 8 LEDs draw too much power for the onboard circuit of the PIR sensor? How would I wire it?

If this is possible how much voltage would I need to provide the PIR Sensor?

If it's not possible as is, is there any way I could still make this work without having to introduce a microcontroller like an arduino?


texts:
In my spare time I've decided to create something on my own. I've never designed difficult things, but I'm very curious, moreover experience would never be useless ;) I decided to create a robot, but I want to do this from 0: schematic, programming to do this the way I want. And the important one: I want it to be autonomous as more as possible (self charging, path finding - some kind of intellectual robot).

I have experience with MCUs and simple logic devices, so I can imagine, which way should robot move, which way I could control it etc. But to achieve desired autonomy at first I should create a way to interact with it (autonomy dictates - radio transmitter-receiver) and some kind of navigation system. Well, this is my way of thinking and I think so.
So for now my question is: which ways is it possible to track movements of a robot, current position and what accuracy is achievable?

Broadly used radio-location is useless here because I have no intentions to measure distances about km (really centimetres and meters - in my room). GPS is useless too as signal is lost in-door.

I was thinking about to use servomotors and count ticks(!), but it is not so reliable as wants to be (robot could rotate wheels, but not move).

I was thinking about GPS in miniature: putting several antennae and measure distances (this is just an idea, which may be either nonsense or unrealisable).

Recently I found inertial navigation system (INS) article on wikipedia, but I'm confused with integral error rate. Wiki states error level expected is to be approximately 650m, which is no good at all.

Did anyone deal with similar problems? If someone could tell me practically obtained accuracy values for different navigation systems or some concepts, ideas or even papers concerning that?

I repeat once again - no industrial realisations, I  want to do this on my own with available elements, costing reasonable money.


texts: Battery - reconditioning a 12V UPS lead acid battery

texts:
I have a 12V lead acid battery UPS battery which I want to revive.
I tried adding baking soda to clean it internally but it did not work. I also tried distilled water in the battery but it was also not helpful.
It reads only 1.30V on my multimeter.
Will a desulfating battery charger using a 555 or other desulfating circuit work (in my case) or any other method?
I am beginner in this and I need some advice.


texts:
Earlier, I asked a question about an induction loop being used to transmit Wi-Fi, or internet to anybody who was in the loop. I then realized that the loop could not pick up the data for uploads, because it is the big loop transmitting, and the small loop in the wi-fi device would not be able to send data back to the big loop.

I then commented

  I also forgot about upload, I only thought of download!

But then someone commented back

  skyler that's actually not so much of a problem, if you could solve all the others. If an antenna can transmit, it can usually receive as just as well.

How could the induction loop pick up the data from the small coil if it takes a huge loop around the house to send the data?


texts: What is used to reduce to 220v AC voltage to lower voltage for DC conversion

texts:
I want to build my own power supply section for my project. The condition is that I want to connect the 220V AC power source to the board and the power section is about to reduce this 220V to 5V, 9V, and 12V using the bridge rectifier.

I am now planning to use 3 linear regulator which are LM7805, LM7809, and LM7812 but I have been wondering for a while about what kind of transformer I have to use to reduce the voltage before supplying it to the bridge rectifier section.

I found that there are DC-DC step down converter but those are for DC not AC.


texts:
I've been trying to do trace length matching in Altium from one node to multiple and cannot seem to figure it out.  The solution I have now (picture below) is to have 3 net ties that break up the one node into 3 and then make sure both sides match.  The problem with this solution is I still need to manually match the 3 traces coming from the PATTERN_B node.  Additionally, I have another trace elsewhere which need to have the same length as all 3 of these, so finding the trace length is additionally difficult because of the net ties now.

Ideally, I'm looking for a reasonably automated tool (like the already existing trace length tuning) that will allow me to go from the 1 pattern node to all 3 input pins.  A better way of manually doing this would be less good, but still helpful.

I'm on Altium 17.1 right now but might move to 18 soon, so I'm open to solutions on either version.


texts: Are sealed lead acid batteries water-resistant?

texts:
I am going on a climbing trip in the Canadian Rockies for 20 days starting this weekend.  I am bringing a 12volt 7Ah SLA battery that I am going to use to charge my GPS, iPod, Camera, and Sat Phone.

I ordered this Yuasa battery.  Will using this in a wet environment, and possibly getting rained on be bad for the cell?  Will the water be able to get inside?  I figured if the Lead Acid and HCl can't get out, then water can't get in.  Is that true?

Also, I know that cold weather makes the life of Alkaline's and even Li batteries shorter, does the cold have a negative effect on Lead Acid batteries?


texts:
I have a design with an 8bit SDRAM which I want to replace with a 16bit one,the problem is I don't have much pins left to connect all 16bit data bus, is it possible to access the whole memory using an 8bit data bus ?

The ram (IS42S16800E) is organized as 4096 rows x512 columns x16 bits per bank, using 9 bits column, I'm only able to access half the ram, this is acceptable if I have to, however, I tried using 10 bits for column address, and it worked, ran a memory test and I can read/write to every location, but I'm not sure how/why this works, if I understand correctly, it should only use 9 bits for the column address ? so does this depend on the organization of this specific ram ? or is this how all SDRAM work internally ?

Update:

I fixed my ram test (Thanks Dave Tweed) and this time it fails, writing to address base+0 overlaps with base+512 which means the 10th bit is ignored and it wraps around to 0. If I use 9 bits for the column address I can still access half the ram.

Here's my ram test:

uint8_t pattern = 0xAA;
uint8_t antipattern = 0x55;
uint32_t mem_size = (16*1024*1024);
uint8_t * const mem_base = (uint8_t*)0xC0000000;

/* Test data bus */
for (uint8_t i=1; i; i<<=1) {
    *mem_base = i;
    if (*mem_base != i) {
        BREAK();
    }
}

/* Test address bus */
for (uint32_t i=1; i<mem_size; i<<=1) {
    mem_base[i] = pattern;
    if (mem_base[i] != pattern) {
        BREAK();
    }
}

/* Check for aliasing (overlaping addresses) */
mem_base[0] = antipattern;
for (uint32_t i=1; i<mem_size; i<<=1) {
    if (mem_base[i] != pattern) {
        printf("address bus overlap %p\n", &mem_base[i]);
        BREAK();
    }
}

/* Test all ram locations */
for (uint32_t i=0; i<mem_size; i++) {
    mem_base[i] = pattern;
    if (mem_base[i] != pattern) {
        BREAK();
    }
}


texts: Thevenin Equivalent Voltage and Resistance with Multiple Parallel Sources

texts:
I am looking for help with finding the Thevenin equivalent voltage in the circuit pictured, basically 2c on the list of problems.

I have so far done the loop equations and have come out with the following:

Loop 1 (left hand side)
E1-R1I1-R2(I1-I2)-E2 = 0

Loop 2 (right hand side)
E2-R2(I2-I1)-R3I2+E3 = 0

I am pretty sure the next step I have to do is combine these equations to solve for either I1 or I2.

Any hints would be appreciated. Thanks in advance.


texts: How to troubleshoot a DRV8833 motor driver module problem?

texts:
I am trying to control a DC Motor with a DRV8833. To be precise, I have this module from MJKDZ (which, I believe, is not the original one from TI).
I measure the voltage on the input pins, they are as expected, but the output pins have 0 V. My input pins have those values:
GND :  0 V (connected to ground)
VCC : +5 V (from a battery power)
IN1 : HIGH (+3.7 V from an ESP32).
IN2 : LOW  (0 V)
IN3 : not connected
IN4 : not connected

Every output pin has 0V (including "ULT", which may indicate a fault condition). All grounds (ESP32, battery, etc) are connected.
I am wondering how I can "debug" what's going wrong.
Do you think I may have overheated it while soldering the pin sockets (I learned soldering when I was a kid from my father probably like many of you, but I didn't do it for a while and now I am terrible at it)?
Or could it be an over-current issue?
So, just to be sure that the issue is really on this particular module, could I try connecting an even simpler circuit like this (basically excluding things related to ESP32):
GND :  0 V (connected to ground)
VCC : +5 V from regular power
IN1 : +5 V from regular power (HIGH)
IN2 :  0 V (connected to ground) (LOW)
IN3 : not connected
IN4 : not connected

and expect the potential difference between OUT1 and OUT2 to be 5 V ?


texts: Low Voltage AC as power source for Audio Equipment?

texts:
When might an AC (not DC) voltage be used as a power source for an audio device - most every guitar pedal I've ever owned converted line voltage - 120VAC to some lower DC voltage - often 9v or 12v DC. However, my Line 6 guitar processor (POD XT) uses 9VAC to operate - I believe that it is not being converted to DC before powering the circuit - what advantage does designing a circuit to be powered by AC provide? I found one answer here:

http://forum.arduino.cc/index.php?topic=186059.0
"Audio mixers often use AC because they need to resolve positive and negative voltage with respect to the audio reference / ground."

Still not clear -
Thanks


texts: Dirty electricity filters how do they work?

texts:
There are videos on youtube about finding sources of high EMR. In this videos they reduce EMR level by plugging some 'dirty electricity filters' in wall outlets. I don't understand how it is possible but this filters somehow reduced EMR-meter readings near them on one of videos.

My question is how do these filters work? Is there scheme for these overpriced devices?

P.S. I'm not sure if it is a good idea to provede a link to specific video or product because they are easy findable and I don't want to indirectly promote stuff which I'm a little bit skeptical about.


texts:
I am designing a system which will use two 12V AC/DC 60W modules (Meanwell IRM-60-12)

I would like to protect the system using a fuse. In the case of a parallel design like the one below, should I use one fuse for each supply or a global fuse at double the amp rating for both?

e.g (sorry for the bad drawing):

Left or right design?

Thanks!


texts: Effects of power fluctuations on batteries?

texts: When we use an AC motor for the battery, if the motor load fluctuates and the power fluctuation occurs, what will this affect on the battery? As a simple example, if the power changes by 10 + 2 sin (t) versus constant at 10, the average drawing power will be the same. But in both cases, how will the battery consumption or lifespan be affected?


texts:
I am looking at implementing a MOSFET Bridge Rectifier circuit. I am trying understand why there is a difference in the basic application circuit and layout from the app note. The layout image below has resistors while the basic application circuit does not.

The app note shows a basic application circuit here:

But then shows a layout with resistors 8 total as seen here:

Does anyone know what the purpose of those resistors could be?


texts:
What is the DC-resistance tolerance for a smd ferrite bead (e.g. BLM18RK102SN1D)?
Does anyone know? The datasheets I have seen only give a maximum value for the DC-resistance.


texts:
I need to measure a current with the osciloscope on a ZYNQ ZC 702 board and I do not know what shunt resistor should I pick. I am not so good at electronics so if some one can help me I would be very glad.
The schematics is attached and I want to measure the current drawn from VCCINT. You can find VCC int at page 40 in the right part of the page upwards. Also down in the left there are R256, R222 and C315 related to this power supply.  Moreover on page 39 in the power controller the power supply enters in pin 64 and 65 and there is also a CS signal PWRCTL1_VCC1A_CS .
Basically I need to measure the current drawn from this power supply by my code, with the osciloscope. Right now I believe R222 is the one but if there is another one as good as that it is better(because right now R222 is missing from the board). Also if you think there is another signal that I need to measure in order to get the current drawn by a circuit powered by this power supply please suggest me.

ZYNQ ZC702 schematic


texts:
According to my analysis, none of the options are correct. But the answer mentioned in my workbook is option B.

In positive half cycle, I'm getting vo = vi.

And in negative half, vo = vi/2. This doesn't match any options.


texts: Questions about transition holes on the pcb board

texts:
Questions:

1) Is it possible to connect tracks of different sizes using a via? Example: on the upper layer 0.8128 on the lower layer 0.6096. The size of the drill is 0.6mm.
2) The larger the size of the via, the better?

In the second photo ring more.


texts:
I am curious about wind turbine generator types used around the world today if anybody has any experience they wish to share.

My question is mainly are most wind turbines of the synchronous or asynchronous type?

I'm guessing this has a lot do to with the rated power of the machine.

If asynchronous generators are used would they be DFIG's for the larger gensets and maybe permanent magnet rotors for much smaller scale turbines?
Are many synchronous generators are used? And are they likely to be excited by brushes or a static brushless exciter?
Are wind turbines ever used to power a load given there is enough wind power, and the mains actually used as a backup for when the wind turbine can't supply the load?
I'm guessing both types are just as tricky to sync with the grid requiring complex power electronics?

Thanks everyone


texts: Unable to use compiler built-in functions to write to dsPIC EEPROM

texts:
As I mentioned here, I've been having issues with EEPROM on dsPIC30F6012A. Since my old EEPROM library was difficult to analyze and support, I went back to square one and rewrote it using the new (newer than my library!) C30 compiler built-in EEPROM routines. I took the Microchip demo code and tried to run it. Compiled, programmed, no problems, but it didn't seem to operate correctly. I made a modified version of their demo, also without success.

I run this program, read the chip's contents back into MPLAB X, and look at the contents of EEPROM. Erase operations work correctly, any addresses I erase comes back as 0xFFFF. But the write operations do nothing. I've tried several combinations, repeated writes, different addresses, nothing appears to be written.

#include <p30fxxxx.h>
#include <libpic30.h>

 _FOSC(CSW_FSCM_OFF & FRC_PLL16);
_FWDT(WDT_OFF);                 /* Turn off the Watch-Dog Timer.  */
_FBORPOR(MCLR_EN & PWRT_OFF);   /* Enable MCLR reset pin and turn off the power-up timers. */
_FGS(CODE_PROT_OFF);            /* Disable Code Protection */

 typedef struct _eestruct {
    unsigned char testdata[10];
} eestruct;
 eestruct eedata __attribute__((space(eedata)));
 eestruct backup_eedata __attribute__((space(eedata)));

 int main(){

    _prog_addressT EE_addr;
    //_init_prog_address(EE_addr, eedata);
    EE_addr = 0x7FF000;

    int temp_word = 0x0102;
    _erase_eedata(EE_addr, _EE_WORD);
    _wait_eedata();
    _write_eedata_word(EE_addr, temp_word);
    _wait_eedata();

    while(1){
    ClrWdt();
    };
    return 0;
}

I've got four theories:

Writes are taking place, and I'm not reading the data back correctly.
Writes are not taking place, because something is wrong with my
code.
Writes are not taking place, because something is wrong with
my project/build options.
Writes are not taking place, because something is wrong with my hardware.

I've posted to the Microchip forums without result. I've opened a ticket with Microchip, and all they did was tell me to use/write an assembly call. They seem uninterested in whether/why these built-in function calls don't work.

Does anyone have any suggestions?


texts: Detect an unknown communication protocol and read data on it

texts:
We have old type textile machinery in our factory. (open end machine) on the machine's screen is showing the operating efficiency of the machine. Under the hood, When I follow the cables, the sensors are followed by multiple sections. Sections only connected each others by 3 wire cables. Finally, 3 cables come to the machine processor (main board).

Main processor is collecting all section values and displaying the total operating efficiency of the machine. I want to read the data over these 3 wires as a parallel bridge and read the logical values and publish this values on a channels like Thingspeak. In this way, I will be able to monitor the efficiency of the machines at home.

The problem here is to determine which communication protocol the 3-wire data from this textile machine uses. How do I identify the protocol via a communication protocol that I don't know and how can I get it from there?

I've used Master Writer/Slave Receiver technique from docs but it returned -1 and didn't make sense.

I tried to draw the wiring diagram to you


texts: What's the purpose of the components shown in this circuits?

texts:
I have a question when studying a power switch circuits.
As shown in the picture below.
It's an switch to enable 12V and 5V to the system by EN signal.
My questions are:

What's the purpose of C2, C4, C5?
What's the purpose of D1, D2, R3, R4?

Thanks a lot for any reply! :)

BR,
David Wu

Hi Olin:

Thanks for the detailed feedback! :)
I still got few questions about your answer and hope that you can give me some hints....
Add more pictures for discussion.

For C2/C4/C5, you said that they are there for slop control.
I add another picture to show the possibe charging current.
Take Q3 and Q4 for example, did you mean that due to the existance of C4 and C5, the voltage built on drain node of Q3 and Q4 will be lower than not having C4/C5?
Same idea for Q2?
How about the turn-off slop?  Still controlled by discharging this C ?
(See pic 1 and 2 below)

There comes a another question, when Q3 and Q4's gate go high, will it boost the drain at the same range, due to C4/C5 existance? Will drain voltage exceed 12V then? (same situation when Q3 from off to on, will drain be coupled to negative voltage first?)
For Diodes, I think you mean that they are used to make charging/discharging time symmetrical.
Charging : 12V => 4.7K => D => Q3 gate
Discharging : Q3 gate => 100K => Q2 on resistor
Not sure if the resistor value make sense to balance the timing.
(See pic 3 below)
Is C3 there only for compensate the charging time of Q2's gate?

Thanks a lot for all the helps!!

David


texts: Are there different Ethernet shields available?

texts:
Beside the w5100 chip powered Ethernet shield, are there shields available with other chips?

The w5100 seems to make a lot up problems. There are many Ethernet related problems documented on several forums. Therefore I wondered if there are alternatives?


texts:
Question:

  Determine the output waveform for the network(assume that all diodes are ideal)

The book says for the positive half-cycle it will be like this:

Similarly I think that for the negative half cycle it will be exactly like this except that the polarity of input voltages are flipped .
But book says that the output waveform for the negative half-cycle will be  same as positive half-cycle (in the positive region) .

But my intuition tells me that if the polarirites are flipped the output voltage must be in the negative region as current is entering from negative side of V0 .Am I missing something here ?

[I'm not allowed to post more than 2 image links]


texts: Xbee Factory -Hardware reset without serial communication

texts:
I'm using "XBee 802.15.4 Module"
After successful connection with X-cut & made a "+++" it responded "Ok"
Then is stopped working ....
I tried to reconnect to it again & failed .. it no longer accept a serial communication.
I searched many topics for this problem , trying to find a solution for reset, specially a Hardware reset ... didn't find any !

So my questions are:

1- "There a method to make a reset for it & restore to factory default with hardware & without serial communication " ?

2- "How I can be positive  that the module is "burned down" & no longer working .." ?


texts: Small connector alternative for 10/100base Ethernet

texts:
I have been looking for a small connector that I can use for Ethernet 10/100 base communication. There were some similar discussions here about the same topic, but I couldn't find a solid answer.

In my application, I don't want to use an RJ45 connector because of the form factor. I looked at some industrial connectors like "Industrial Mini IO" from TE, but the problem with those is now I have to deal with a big back shell for the cable itself although the connector helps with making the product smaller.

https://www.te.com/usa-en/product-2294417-4.html

I was wondering has anyone used an RJ12 for a 10/100 base Ethernet application? That's currently one of the options I'm looking at and I'm not sure if it is the correct way.

If RJ12 is not a good option, does anyone know any small connector that I can use which also doesn't need a big back shell for the mating cable?


texts: Thevenin tension on the following circuit

texts:
I've been trying to solve a circuit by aplying thevening (the following one)

I've obtained 11,4V but I've seen to be wrong.

Can anybody help me?


texts: Using SPI Nor Flash as storage memory in Vehical tracker device

texts:
I am designing a Vehicle Tracking device. I need a storage memory of 2Mb to 8Mb to store data from MCU. Based on what my MCU supports, I am planning to use SPI NOR Flash as a storage Device. As I know , NOR Flash is not recommended as a data storage device but it is commonly used as a Code storage device.

Considering the requirement of only 2Mb to 8Mb, is it okay to use NOR Flash as a data storage device?


texts: I have two transformers with a 220V primary and 12V secondary winding. What will happen if I apply 220V to the primary of the first transformer and connect the two secondary windings together? Will the second transformer's primary winding give 220 volts again?


texts: How to correctly connect low current analog ground plane with high current analog ground plane on PCB?

texts:
I am currently designing a PCB for a PWM controller based on the LMC555 timer chip along with a low side gate driver FAN3100TSX and N channel power MOSFET. Below is the PCB in question. In my design, I have separate ground planes, one on the left side is for low power analog section and on the right side is high current analog section. I have created a common connection for ground planes at the top middle (at pin 1 of J1 ). Essentially this would be my star ground connection. Additionally, the gate driver FAN3100TSX (IC2 on board) requires pin 2 to be common ground for chip for both control signals and power signals. Because I'm using the driver in non-inverting mode, its IN- pin (pin 4) needs to be grounded. This IN- counts as control signal pin. Thus I have made a connection between pin 2 and pin 4 to create common signal ground for the IC. I have also connected pin 2 to the high current ground plane on right because of return currents when it drives the Power MOSFET.  So my question is, does this connection between these two pins create a ground loop and cause problems? Is there a different way to do this and create a star ground? Any suggestions. Thank you
This is whole PCB:

Zoomed in at J1:

Zoomed in at IC2:


texts: Need advice choosing wiring configuration for combination pressure and temperature sensor

texts:
I am currently trying to purchase a combination temperature and pressure transmitter for a project, and it has an option to choose between a 3 wire or a 4 wire configuration. I have attached the link to the datasheet of the transducer which has all its specifications.
https://www.pmc1.com/Customer-Content/www/Products/Files/ATM.1st.T.705a.pdf

Here is the wiring diagram:

I'll be connecting the pressure sensor to a 9 pin D- sub female connector for an analog input pin on DAQ device. Can anyone help me figure out how I will be able to connect the sensor to the input pin? Here is the link to the DAQ manual: https://d36j349d8rqm96.cloudfront.net/3/6/DEWE-43_user%20manual.pdf
Pages 21- 24 have all the information regarding the sensor connections and the input pin layouts.

I am new to industrial pressure sensors and haven't worked with them much before, therefore any advice will be a great help! Thank you.


texts: Is a 1N4001 diode supposed to allow reverse leakage?

texts:
I recently bought one of those cheap digital clocks from my favorite Chinese superstore. Most of these clocks have one achilles heel: the power supply. They get their power either from a USB source OR from 3-4 AAA batteries. Unfortunately it's wired so that when you power it from USB, it passes some of that voltage on to the battery contacts. This is not regulated any way because it's not supposed to be a "charger". So your choice is to either run the clock from battery (and have to fiddle with the display every time you want to see it) OR run from USB (and have to reset the settings every time the power blinks).  If you run it from USB with the batteries installed you run the risk of exploding the batteries.
I thought I could get around this by putting a diode in series with the battery contacts.  To verify this, I did some testing.  I used some jumpers to clip the 1N4001 diode in series with the positive battery terminal and then to a multimeter.  To my dismay, the voltage was fluctuating around 100mV.  I reversed the diode just to make sure I didn't make a basic mistake- when I did that I got 3.5 volts.  So I put it back and hooked it up to a scope.  I found that there was an odd-looking waveform and it was actually AC coming out the wrong end of the diode- between +100mV and -100mV to be exact.  It was about 55Hz or so.
Why am I getting an AC voltage out of the wrong side of the diode?  Furthermore, will 3 AAA batteries (@4.5v) be damaged if they are exposed to this small current for many months (years?) at a time?


texts: Running a 24V motor on a 12V boat system

texts:
I'm trying to design a jigging machine for a fishing boat, using a RaspPi as the controller. (A jigging machine jerks a 1kg lure up and down near the sea bed, and pulls in a fish when it's hooked.)

The motor I'm hoping to use is here: 3336_0 - 86STH156 NEMA-34 Bipolar Gearless Large Stepper and the supplier recommends I recommends I use a 24V supply.

However, the boat I want to fit the machine to has only 12V. I'm trying to assess the pros and cons of different approaches.

The simplest solution is to just use a 12V supply to the motor. I understand I'll need thicker wires to supply this. I'm thinking that using 12V will generate more heat and produce less torque. There will be times that the machine will need to pull up several fish at a time from 50m deep - say a 20-30 kg load. And sometimes the hook will snag the bottom. I'll include a current monitor, so I could limit or cut the supply when there is too much load. I don't know how often this might happen till I try it though, and how inconvenient it would be.

I've ruled out having 2 batteries, in parallel when the engine is running and in series when the engine is stopped, using solenoids to switch - the engine is often left running while the boat is fishing, as it needs to continually drift with the tide/wind, then motor back up to the spot where the fish are.

So I think the only other option is to buy a second battery and wire in series, swap the 12V alternator for a 24V alternator, and have something that supplies 12V from the 24V for the GPS, radio etc.

Naturally, I'd favour the first option, but I wonder how important a 24V supply would be for the jigging motor, and how much we'd lose out going with the 12V option.

Thanks for any further input on my inputs quandary.

John


texts: Drive logic signals when power might be off

texts:
I'm designing a board that interfaces two systems with an SPI signal. Each system has a 5V power supply, and I have access to both supplies, but either supply may be turned off at any time. How should I drive and receive the SPI signals so that I don't drive current into powered-off logic?

Low power design is not necessary, and the SPI speed is only 31kHz, so answer one is to just put in series resistors. That's ugly :-)


texts: ADG608 multiplexer acting really strange in Multisim

texts: I am trying to use the circuit below to switch between multiple resistors using a multiplexer. Initially I had different values of resistors attached to every channel, but since I was getting very strange and HUGE!! results, I grounded all the channels except the first channel and just connected a 120 ohm resistor. I am measuring resistor readings of magnitudes of Mega ohms and I have no idea how such huge values of resistance are showing up at all. I am not sure what I am doing wrong and I really really appreciate any help.


texts:
I am thinking of using DesignSpark for PCB design and pass the files on for manufacture.

If I want to miss out the soldering part and get the full boards made by a pick and place machine, can I use DesignSpark or are there any other design tools for this?


texts: Cascading two instrumentation amplifiers to achieve higher gain

texts: Is it possible to cascade two instrumentation amplifiers (for instance INA128)? let's say each has a gain (G) of 100 up to 100 kHz. Would this result in a G=10k up to the same frequency?


texts: Light indicator for TTL-level UART serial interface with a SINGLE LED?

texts: I want to add some LEDs after the MAX232 to indicate the serial traffic on one of my design. I found some decent circuit like this but seems like all of them are using two LEDs for TX and RX. Because the premade chassis only has limited LED holes, I wish to use a single LED to denote all serial activities (flashes when TX or RX is busy). Would two diodes from TX and RX in parallel connected to the base of the PNP transistor of the circuit above work? How should I do this properly?


texts: Two details about phase noise have been confusing me for a long time. Hope to be resolved

texts:
Just like FLOYD M. GARDNER said in the PhaseLock Techniques, 3rd Edition: "In light of that success in spectrum analyzers, a practitioner’s answer to the question above is: The spectrum of phase noise consists of the data delivered by a phase-noise spectrum analyzer.", the value of zero frequency of phase noise PSD should be infinite in theory. But in reality, what should the value of zero frequency of phase noise PSD showed on phase-noise spectrum analyzer be? In other words, what is the value of zero frequency of phase noise PSD stored in phase-noise spectrum analyzer? If I simulate phase noise PSD in Matlab using discrete data, what the zero frequency value should be or should be set? Hope these two problems can be solved.
What is the VCO DC power? What is the relationship between VCO DC power and VCO output phase noise PSD which has a 1/f^2 shape? Hope to be resolved.


texts: Would SPI work in a system that may have EMI, distance =~ 60 cm

texts: for a project I will be using 2 microcontrollers communicating with SPI 100 kbps. Distance between them will be approximately 60-70 cm but these microcontrollers will be in a case with a 24 V battery and other components so I am afraid of EMI and noise. Would there be a corruption in SPI communication or any problem? Any suggestions that you can give such as: use twisted pair cable etc. As a last option I might go with a CAN but that would be a waste of space for CAN Bus transceivers.


texts:
I'm building a device with two PICs, a PIC18F46K22 and a PIC16F88. I have a buffer on the 18F46K22 which contains a program that I want to write to the program memory of the 16F88. I can't do this manually, because it has to happen on the fly (the buffer might change), so the programming has to be initiated by the 18F46K22. The CONFIG bits can be set manually though, I don't need to change them on the fly. There is also no need to write to the 16F88's RAM or EEPROM by the 18F46K22.

The two chips are powered with 5V and there is no 12V supply available. I guess I'll have to go with Low Voltage Programming (LVP)?

Is there anyone who has done such a thing already? Is there some code or a circuit available somewhere to program a PIC with a PIC?

In the end, this is to make a basic PIC-based coding device: the user edits the buffer on the 18F46K22, programs the 16F88 with it. There will be an I2C interface between the two so that there can be some sharing of results. The programming to the 16F88 will be for mathematical purposes only: the chip gets some input over I2C and a START trigger on some pin. After that, the result is sent back over I2C.


texts:
When a vendor specifies an Rds(on) value for a part I have seen typical and max values specified but never minimum values. I understand that Rds(on) is a function of temperature and gate to source voltage (Vgs) but for a given temperature and Vgs is the variance of Rds(on) basically an intrinsic of the MOSFET design? How much does the Rds(on) vary from FET to FET of the same kind at a given operating point?

What motivates this question is current limit sensing of the drain to source voltage (Vds). I can measure Vds and approximate a current if Rds(on) is known. However if Rds(on) varies too much the current limit sensing may erroneously report no fault with a huge current.


texts: How does the logic board know the buttons have been depressed on the Philips ACC2330 foot pedal?

texts:
Unlike other input devices like an Xbox controller, that has the buttons
physically mounted to the logic board, this foot pedal's logic board has
absolutely no apparent connection to the buttons. How is the communication
done? I can't easily take the thing further apart.

Bottom

Bottom Plate Removed

Logic Board, Top Left

Logic Board, Top Middle

Logic Board, Top Right

Logic Board, Bottom Left

Logic Board, Bottom Middle

Logic Board, Bottom Right


texts: Effective Capacitive Loading of Active RC Integrator

texts:
For a simple active RC integrator shown above, what is the effective capacitive load when output is open-circuit.

I think it would be the integrating capacitor, \$C_I\$, because of the virtual ground at \$V_x\$.

But it doesn't really make sense since \$C_I\$ is charged by input current, not the opamp, so the opamp doesn't "see" the integrating capacitor.


texts: Switching between two Ethernet magnetics and one simple Phy

texts:
I'm deep into a project and I would like to ask how can I switch 2 ethernet interfaces to single PHY. I know that there're some suitable analog switches for this purpose like MAX4890, but I don't fully understand how does this IC work.

It's supposed that Ethernet signals are differential, depending on which interface you use, these levels could be +/-1V and +/-2,5V.
My question is, how does this IC work with single and positive supply if needs to switch differential signals? In the same way, the PHY has also single supply.


texts: What's up with these plated through-holes / vias?

texts:
We purchased a number of stainless steel kiosk keyboards from a Chinese manufacturer a while back and have been seeing extraordinary failure rates (around 30%).  Groups of keys just stop working.  I've pulled several of them apart and traced the problem to plated through-holes / vias that have failed.  I've been repairing them by passing a small wire through the hole and soldering it directly to the trace or pad on either side.  Photos show what they look like when I pull them apart:

Given this information I have two questions:

What's up with these?  Any theories on why they're failing?  Anything we can do to prevent it?
Is the repair method I mentioned earlier appropriate?  Is there a better way or anything specific I should be taking into consideration?

As a follow-up to this, we eventually figured out that the kiosk screen cover wasn't sealed properly and cleaning solution sprayed onto the plastic was seeping into the enclosure, running down the inside of the keyboard mounting bracket, and then into the housing for the keyboard itself.  The cleaning agent would corrode the copper in the vias if they weren't sealed well enough.  After sealing the enclosures properly we saw much better performance out of them and far fewer failures.


texts: Two 12v batteries in parallel 7ah and 20ah

texts: I have two 12v batteries, 7ah and 20ah. Can they be connected in parallel without damaging the 7ah battery? They will be charged separately.


texts:
Why is the noise figure of an amplifier minimized when the  source impedance is equal to: $$Rs=\frac{E_n}{I_n},$$ En,In are respectively the noise
voltage and noise current of the amplifier
$$$$Noise figure is given by : $$F=1+\frac{E_n^2}{4kTBR_s}+\frac{I_n^2R_s}{4kTB}$$
k is Boltzmann’s constant
,T is the temperature in degrees Kelvin,
B is the bandwidth of the system in Hz.