texts:
I'm trying to calculate voltage ripples on bulk capacitors of my guitar amp.
Here's a schematic of it:

simulate this circuit – Schematic created using CircuitLab

According to formula Vpp=I/fC, that is Vpp = 0.82/(2*50*0.0011)= 7.4V

I = 0.82, transformer is rated 30W, for rough estimation 30W/36.6V, it's going to be less at maximum load.

C = 0.0011, since two capacitors are in series

Aren't 7.4 V ripples way too high for this application. There are planty of information on the internet about ripples. I'm pretty sure I got it right, or am I not?

The main question is 'if calculations are right, are 3.7 V ripples OK considering schematic above?'

But I more inclined that something is missing in calculation, because I can hear 100 Hz hum, but it is hearable only when ear is <10cm from the speaker. Considering speaker is rated 15W, I bet it's OK.


texts: Using diodes to mix 2 audio signals into one set of speakers

texts:
I have the audio output of 2 computers connected to only one set of speakers.
Each computer uses one of these external USB sound cards:

And I use this splitter cable to wire the signals together:

The whole thing works, but with some minor problems:

There's a little bit of noise when the speakers are set at max volume
One audio signal sounds a bit louder than the other
When recording the microphone input, sometimes the audio output of the other computer becomes the mic input

So obviously the two signals are interfering each other and also each signal finds its way into the other sound card because the splitter cable is meant to be a splitter and not a mixer.

So I thought if I could solve this by adding diodes to each side of the splitter cable so that each audio signal goes to the speakers only and not to the other sound card.

Will this idea work?
What kind of diode should I use for that?


texts: Does Public Switched Telephone Network (PSTN) use two voice channels for a single voice call - one for each direction?


texts:
Hi I was wondering how to implement a pitch shifter?

So I have an audio input signal sampled at 48KHz and a 256 sample FFT. So my binsize is 48000/256=187.5 Hz per bin.

From the 256 samples I am taking the bin that has the maximum magnitude, and then in order to find the frequency I am folowing this formula:

frequency= binIndex * binSize.

Then I am taking multiply this frequency by 2 in order to make a pitch shift.


texts: Difference between hard decision and soft decision in error correction codes

texts: I am having trouble understanding the difference between hard and soft decision. My current understanding is the following. Using a sparse graph, when we are trying to decode a stream of bits, we take into account the probability that each particular bit is either a 1 or 0. Then we use the probability to gauge what the bit should be. And in hard decision, we disregard the probability information we gain by analyzing the parity bits. This is the stem of my confusion. If we are disregarding the probabilities, then how is error checking happening at all? Is hard-decision only used for concepts such as interleaving, etc? Please correct me if any of my understanding is incorrect.


texts:
I am attempting to identify brass casings vs aluminum casings.  I'm been trying to figure a reliable way to differentiate between the two.  I've thought about

Color: This may work, but I fear that dirty optics and targets may not work so well.
Weight: I'm not really sure how to implement this in my context.
Conductivity/Resistivity: Perhaps an inductive sensor?  But aluminum is very close to the same value as brass.
Ultrasonic properties: This may not work with varying levels of dirt.  But I really don't know much about it.

I prefer non-contact, and a solution that is impervious to contamination, but I'll take any suggestions given.

It seems that an inductive sensor would be the way to go.  I'm okay with rolling my own, perhaps a couple of tuned coils which the target passes through?

Okay, thanks to Charles for getting me on the right track.  It looks like I'm needing an eddy current sensor.

These are shell casings, and when run through the machine will all be of the same caliber, so the uniformity should be good.  For material identification, distance from the coil is important, and since the target is not always in the same position, I'll run the casings through the coil center, which should be immune from position errors.

It looks like some aluminum alloys overlap the brass alloys in resistivity, but I bet that the alloys used in cartridges are very consistent.  I do have another bit of information, and that is the actual identification of the head stamp.  Headstamp coupled with resistivity should get me a very accurate indication of what type of metal the cartridge is made from.


texts: Trouble understanding diode circuit problem

texts: I am having trouble understanding a diode circuit problem. I dont understand which direction the current will flow. I think for part a, Vout will be 9.3 V. But for part b, I'm unsure of how to get +6.2 V going into D1. I am just unsure of how to tackle this problem. Thank you.


texts: Why Do Pipeline ADCs have an "Overlap Bit"?

texts: In pipeline ADCs, there is an amplifier after each stage that amplifiers the remainder of the previous stage by 2^(number of previous stage bits - 1). For example, if the flash ADC in the first stage is 3-bit, the remainder is amplified by a factor of 4. This leads to an overlap bit between the stages. My question is, why do we need this overlap bit, and why don't we remove it to get the maximum number of output bits from the ADC?


texts: Is it possible that a three phase motor still spin in the same direction it was even after the phases are interchanged.


texts: Bluetooth low energy: effect of slave latency on power consumption

texts:
Slave latency is meant to allow a bluetooth le slave to skip a certain number of connection intervals before actually establishing a connection event with the master. In principal, this seems like it should mean that increasing the slave latency should have similar impact on power consumption of the slave as increasing the connection interval (i.e. if the product of slave latency and connection interval is the same, power consumption of the slave should be roughly the same regardless of each parameter's actual value).

Ok, so I've been using nrfgo studio to try and get some power consumption estimates for different parameter's, and it looks like my assumption here is wrong. For example, a slave latency of 0 and connection interval of 500ms yields an average consumption of ~26uA, while a slave latency of 10 and connection interval of 50ms yields an average consumption of ~105uA.

Am I misunderstanding how slave latency works? Or is nrfgo accounting for slave latency in some different way? Is it possible that nrfgo is miscalculating it's estimate?

Note: the number above are from estimates in the nrfgo studio, not measurements on actual hardware


texts:
I have a doubt about using opto-couplers to isolate the high voltage side from low voltage side.

This might be a dumb question :D

I'll ask based on above picture.
SO when 5V is applied to the input of optocoupler , it will turn on and pass the 5V to the base of darlington transistor.

But inside the opto-coupler is a transistor , right? so in order to turn the transistor on , B-E should be forward biased, i.e., Base +ve and Emitter- GND. But in above circuit Emitter of Opto coupler is not connected to GND, so how applying 5V will turn it On and how 5V will reach base of darlington transistor?

and also is it okay to say  "5V will reach base" or current flows from C to E of optocoupler to base of second transistor?

thanks


texts: How to calculate gain of wheatstone bridge + differential amplifier?

texts:
I have the following circuit:

I have a hard time determining the mathematics of this circuit. If we ignore the Wheatstone Bridge to the left, focusing on the differential amplifier, i know that the amplification is given by:

(V2-V1)*(R6/R5)

Given that R6=R8 and R5=R7. But what happens when I add my Wheatstone bridge, which doesn't have the same resistor values on the two sides of it? (10k ohm at the left side and 1k ohm on the right side).

In the picture i have managed to balance the R5 and R7 so that the output is ~0V when there's no difference in the bridge - but this is just by lucky guessing. I would like to understand the mathematical formulas for the circuit :-)


texts: What is a DC block and how can I put this on a PCB?

texts:
The circuit diagram that I am trying to replicate casually mentions a component called "DC block" but doesn't go into details.  I believe this has something to do with RF filtering?  Will I be able to solder a component onto a PCB to perform this function?  The component is located at the RF_in pin of a GNSS module.
page 15 of the document below
hardware integration


texts: Choosing inductor and capacitor for boost converter

texts:
I am working on a IoT project that involves an arduino and a 4G LTE module. The device will be operated with two Alkaline batteries. Both the arduino and LTE module require 3.3V input so I want to design a boost converter that reliably delivers 3.3V from a voltage range of 1.6 to 3.1. The device will be in a deep sleep for most of the day and only wake up 2-3 times a day for a short period of time, so an important converter requirement is low quiescent current. While the arduino doesn't draw much current (50mA-100mA), the LTE module requires up to 1.2A of current when awake.

Doing my research for suitable boost converters, I came across the TPS613221ADBVR. It has low quiescent current (6.5µA) and can provide up to 1.6A of current. But given my limited knowledge in electrical circuits, I'm a bit overwhelmed when it comes to choosing the right inductors and capacitors. The datasheet is excellent and gives two examples on how to choose inductor/capacitor for the given requirements of 2.2V output @ 50mA (example 1) and 5V output @ 500mA (example 2).

The requirements in my case are as follows:

Input Voltage: 1.6V ~ 3.1V
Output Voltage: 3.3V
Output Current: 1.2A
Output Voltage Ripple: ?? (how to find out?)

What inductors and capacitors do I choose? Do I need a Schottky Diode and if so, which one? What Output Voltage Ripple can be tolerated?


texts: Any pitfalls when going from two to four layer PCB?

texts:
I've had a couple of two layer boards made with success but my current design requires more layers. Can anyone suggest any pitfalls to be aware of for my first attempt, the price difference is significant so I'm hoping to not waste it.

In addition, can you jump from any layer on the board to any other or only to adjacent layers?


texts:
I'm looking to buy a ATTiny85 for a school project. We require 4 analog inputs for our LEDs which we're using as makeshift light sensors (this part of the project is sorted). I've read the the pin layout of the ATTiny85 and it says that there are 4 ADC pins however the ADC0 pin is also the RESET pin and so not sure if that means it can't be used as for analog input.

If this can be used then my second question is whether an ATTiny85 can be sufficient for the use of 4 LEDs and 2 DC motors (which I hope can be connected to the digital pins). Id prefer not to get the larger 14-pin version as we are looking to save space.

Is there any ATTinys that have 10 maybe 12pin layouts also?


texts: L6472 step motor driver and flyback diodes

texts:
I plan to use the L6472 step motor driver but I'm not sure if I should use flyback diodes connected to the driver output side.

The step motor will be bipolar with the following specs:

The L6472 has internal source-drain diodes with these specs:

Usually there are always flyback diodes but not on the evaluation boards of the L6472. So is it safe not to use these diodes? Or might the L6472 be damaged? The datasheet doesn't say more about the diodes...

Thanks!


texts:
I'm interested in using some high-performance FPGA development boards, but it seems like most of the high-end, modern options from both Xilinx (Digilent) and Altera (Terasic) seem to be PCIe-based boards. I almost exclusively do development on a laptop, where I don't have a PCIe slot.

Is there a reason that there aren't high-performance boards available as standalone, USB devices? Is this the standard way that the devices are used in practice? Do you have recommendations for how I can integrate a top-of-the-line device (preferably Xilinx) into my workflow?


texts: Is it possible to calculate a diode's V-I curve?

texts:
the other day I was confused because I din't get how an led has different voltage drop's depending on the resistance of a resistor and the voltage supplied by the battery. But then someone answered my question and told me that an led has a resistance as well. And that, that resistance changes depending on the heat generated by the LED and that creates a non linear curve.

So I was wondering... Is there a way to calculate this non-linear curve. And If there isn't then how does an app like "Every Circuit" calculates it?

Here are some screenshots I took too show y'all what I'm talking about.

And here is how that curve would look on a graph:


texts: Friis transmission equation (log scale calculation)

texts:
I am trying to understand the Friis transmission equation.
My scenario:  I consider transmit antennas (\$T_x\$) and receive antennas (\$R_x\$) at a distance R [km]. f [GHz], \$G_{T_x}\$ and \$G_{R_x}\$ in dBi, \$L_a\$ in dB ( loss) (<0).
\$G_{R_x}\$ =0 that is why I would like to make a calculation in logarithmical scale.
Friis equation:
\$P_r=P_tG_tG_r(\lambda/4\pi R)^2L_a\$

and then I wrote in log scale:

\$P_r(dB)=P_t(dB)+G_t(dB)+G_r(dB) + 10 log(\lambda/4\pi R)^2 + 10log(L_a)\$

In Fundamentals of Digital Communication by Upamanyu Madhow, p 134

Why is G in log scale in dBi ? I thought that dBi is in log scale dB
\$L_a\$ in dB, in log scale is it also in dB?


texts: stc12c5a60s2 similar code but typed in different PC not working in keil

texts:
Is there any reason why the code typed in my friends pc(bottom) works properly while the code I typed in my pc(top) doesn't? Both doesn't seem to have any error when compiled on my PC, but when downloaded onto the STC12 board, the top code would ask for val1 and val2 but skips asking for the operator then spits out 0 as the result. I think it might be a text format issue on my PC, but I don't know how to fix it.
my code that doesn't work
#include<reg51.h>
#include<stdio.h>
#include<math.h>

void main(void)
{
    int val1,val2,eq;
    char op;
    TMOD=0x21;
    SCON=0x52;
    TH1=253;
    TR1=1;

while(1)
{
    printf("\nValue 1");
    scanf("%d",&val1);
    printf("\nValue 2");
    scanf("%d",&val2);

    printf("\nOperation");
    scanf("%c",&op);

    if(op=='+')
    {
    eq=val1+val2;
    }

    if(op=='-')
    {
    eq=val1-val2;
    }

    if(op=='*')
    {
    eq=val1*val2;
    }

    if(op=='/')
    {
    eq=val1/val2;
    }

    printf("\nresult=%d",eq);
}

}

friend's code that works
#include<reg51.h>
#include<stdio.h>
#include<math.h>

void main(void)
{
    int val1,val2,eq;
    char op;
    TMOD=0x21;
    SCON=0x52;
    TH1=253;
    TR1=1;

   while(1)
   {
    printf("\nPlease enter value 1 ");
    scanf("%d",&val1);
    printf("\nPlease enter value 2 ");
    scanf("%d",&val2);

    printf("\noperatation");
    scanf(" %c",&op);

    if(op=='+')
    {
    eq = val1+val2;
    }

    if(op=='-')
    {
    eq = val1-val2;
    }

    if(op=='*')
    {
    eq = val1*val2;
    }

    if(op=='/')
    {
    eq = val1/val2;
    }

    printf("\nResult = %d",eq);

   }

}


texts: How to use an Arduino in order to control fluids in measured amounts?

texts:
I am new to the Arduino Platform and the Electronics world. I am currently working on a project which requires accurate fluid controls. By Fluid Control, I mean, pumping a fluid, eg. water, in certain and accurate amounts like ml, from a particular source.

Before, I mention the question, I will specify what I am doing in detail. There will be 3 different sources of the fluid. I have to deliver some amount of fluid from each source to a single container. The amount of fluid taken from each source will vary. The amounts will be in the range from 0 to 1.5 ml. I am planning to use an Arduino to control the entire process.

Now, for my question: Can a mini pump with a motor, deliver the fluid in such minuscule amounts ? If not, then what other options do I have to achieve that ?
Please consider that I have 3 different sources, so refer to a solution which can efficiently control each source independently.

I had thought of using a Solenoid valve instead of the motor. But, I need to decrease space in the project and also do not want an external power source (correct me if I am wrong about this assumption about solenoids).

Any help would be appreciated. Tell me if I am lacking details.
Thanks.


texts: The binary up counter works with function generator in simulation but doesnot work when manual switches are used?

texts:
ABOVE SIMULATION IS NOT WORKING

ABOVE SIMLATION IS WORKING

My simulation donot work if I manually turn switch on and off for clock even though I have used pull down resistors but when I use pulse generator for clock input , it works fine and correctly.


texts:
I have a question about magnetics and particularly about inductance per turn, generally indicated as follows $$A_L = \frac{L}{N²} = \frac{µ_{core}A}{l}$$
where A is the cross section of the core and l is the magnetic path length. So the inductance per turn depends on the permeability (µcore) of the core.
When I take a look on materials on Magnetics, I compare "High flux" core and "Kool µ" core (powder core).

The composition of the two cores is different so it seems logical to me that if the core is geometrically the same, the inductance per turn cannot be the same, isn't it? Otherwise I do not understand why it still exist Kool µ core as the saturation flux density Bsat is lower than for the High Flux core.
However, it is the same as the technical documentation show it:

Is it possible to have the same inductance per turn whereas the composition of the two powder core is different?
Have a nice day! :D


texts: Why not vary the opamp feedback resistor to change output levels?

texts:
I'm thinking of circuits that feature an operational amplifier like the venerable 741.  Extremely often, you see a variable resistor in the final output acting as a potential divider to adjust the level of the output signal.  The feedback resistor would be fixed in this case to provide the appropriate gain.

Why do you never instead see a variable resistor as the feedback resistor for the op amp?  It seems that it would achieve the same objective.  You would be adjusting output level by changing gain instead.  Is there some reason to always have a fixed feedback resistor and adjust output level through other means?


texts:
Why, in a lot of applications (e.g for bioengineering where very small devices are developed for the recording of biosignals), after an amplifier there is a comparator (with two inputs, one for the analog signal and the other for a triangular waveform) to modulate an analog signal to a PWM signal?

Why should we convert the analog signal to a PWM signal? What is the purpose?

So far I have understood that we want a PWM signal because it is the first step to convert an analog signal to a digital signal through an ADC. Is that true?

Paper: "Using Pulse Width Modulation for Wireless Transmission of Neural Signals in Multichannel Neural Recording Systems", Ming Yin, Student Member, IEEE, and Maysam Ghovanloo, Member, IEEE

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3579626/


texts: What capacitor do i need for a 3phase 50HP motor

texts:
Hi currently have a 3phase 50HP motor with an 80% Power factor
I need to bring it up 95% power factor.
What capacitor size would i need to achieve this.
If someone can show the formulas they used that would be great!
Thanks
This is a link to the motor
https://inventory.powerzone.com/item/55179/used-50-hp-vertical-electric-motor-reliance
575 volts, 48amps
If we assumed a power factor of 80%. how would i go about correcting it to 95% power factor?


texts: Function of UCC2813-1 in flyback converter

texts:
I am studying a design of a fly back DC-DC converter. It is based on TL431 voltage regulator with PC817 opto-coupler. I heard that it is a popular design used. Switching PWM pulses are generated using UCC2813-1 IC. I know how the circuit is supposed to behave. However I could not understand the exact way in which UCC2813-1 operates.

I have seen its data sheet and know how pins behave individually. Can you please explain the function of pins relating one to other like the relation between REF and RC, COMP and REF, CS and COMP and how they effect overall function of IC.

I also couldn't understand the comparator symbol used for 'error amplifier' to which FB pin is connecting (inverting input) - comparator with arrow symbol in block diagram in RED square. what does arrow indicate?


texts: Li-ion cell voltage balancing issue while charging

texts: I have  a two cell li-ion battery which has specifications of 7.4v, 2200mAH. I used one cell (3.7v, 2200mAH) for a required project. I discharged it and then reconfigured in to series(7.4v, 2200mAH) again and charged up(charge voltage of my circuit is 8.4v). It is not drawing sufficient charge current and finally only  1 cell is getting full charge voltage of 4.2v, other one remains low voltage(2.7v). So is there any problem of charging with two cell having different level of voltage.


texts: How to correctly find the RMS on ARM 7 LPC micro-controller?

texts:
I am trying to find the RMS of an input sine wave using the ARM 7 LPC 2119 micro-controller. I know the theory behind finding the RMS of such a waveform but I am having trouble implementing this in code, especially the sampling at equally spaced mid-ordinates. I also have just used timer interrupts to find the frequency of a sine wave using capture inputs, so I am aware of the basic functionalities in terms of programming an ARM 7 LPC 2119 micro-controller.

I am testing this functionality using a 3 V peak-to-peak sine wave with a frequency of 50 Hz. I have shifted the waveform upwards by 1.5 V so to avoid having any negative values going into the ADC pins of the micro-controller.

To sample at equally spaced intervals I am using timer interrupts, In a very similar way to this example here. Instead of switching on an LED, I am doing an ADC conversion.

Before using the following formula:

I need to make sure that I am sampling at given intervals, and to test this I have set my timer clock to provide a 20ms delay before entering the ADC function by doing so:

T0CTCR = 0x0; //Set Timer Mode
T0PR = 60000-1; //Increment T0TC at every 60000 clock cycles
//60000 clock cycles @60Mhz = 1 mS

T0MR0 = 21-1;   //Zero Indexed Count-hence subtracting 1
T0MCR = (1<<0) | (1<<1);//Set bit0 & bit1 to Interrupt & Reset TC on MR0

Once this is done, I am enabling my timer interrupt:

  VICVectAddr0 = (unsigned )timer0ISR; //Pointer Interrupt Function (ISR)
  VICVectCntl0 = (1<<5) | 4; //(bit 5 = 1)->to enable Vectored IRQ slot
  VICIntEnable = (1<<4); // Enable timer0 interrupt

The above code gives a 20 ms delay. With a sine wave at 50 Hz, this should give the same value on every reading, since the period of such a sine wave is also 20 ms. However this is not the case and I can see no visible pattern in my results.

The ADC function I am using works well on DC voltages and I can also confirm that the timer is indeed giving a 20 ms delay before entering the ADC function.

Am I missing something obvious here or could there be some other variables I am not taking into consideration? Any ideas would be appreciated.


texts: Using 12.0v 2.0A charger on 7.2v 1.5Ah No Li-Ion Drill

texts:
Someone lost the charger, I have a 12.0v 2.0A charger on 7.2v 1.5Ah No Li-Ion Drill

What are the risks? Thanks


texts: Video wireless streaming efficiency (analog vs digital)

texts:
I was wondering about the best way to transmit a real-time video (wireless).I do not need to be high quality video, so I've bought this camera module:

Camera module
Camera datasheet

Now I need to make a wireless transmission in real time without substantial delay. I have here a couple of nrf24l01 modules:

NRF24L01
NRF24L01 Datasheet

Note that despite the fact that it uses a carrier of 2.4GHz, it has a maximum air data rate of only 2Mbps. Is this only because all the checksum, encoding and redundance methdos (specified in datasheet) to ensure a reliable communication?

If that so, I know that for a video live streaming I should use some type of transmission that excels for speed and not for reliability, correct? So this module will probably be a bad choice.

With that said, now I still wonder what should be the best method: analog or digital? I've seen some 5.8GHz analog transmitters but its input is an analog video signal. Since my camera module only outputs digital signal, I would have to use a DAC between the camera and this 5.8GHz module, correct? On the other hand, I could use some other kind of 2.4GHz transceiver which could give me some free choice of encoding. Then I could use some simple digital modulating process (FSK based) and transmit full RGB scenes with a simple CRC in the end.

Still, another thing I thought is to compress each image before sending (with some high speed MCU that I've got here). The problem is that my best MCU has only 8kB of RAM and I think it would easily exceed that.

What do you suggest me to use in this process?

Just a reminder: I need a fast transmission because my computer (receiving images) will compute some algorithms based on those images to send back a command to my MCU. So it all depends on this transmission.


texts:
Are there any special considerations I should pay attention to, when I wire multiple LEDs in Parallel?

I am doing a project with a 100 LEDs in parallel. Each LED could be a different color, and each LED is wired with a resistor (or should I not do this and group the LEDs with one resistor?)

I've calculated each resistor with regarding to the amount of current the LED will draw, and the power supply will come from a wall wart rated at 5v and 5A.

Sample diagram:


texts: Offsetting a differential amplifier to remove the need for a dual supply

texts:
I'm developing two similar circuits that will enable me to differentiate the X and Y coordinates from a segmented photo-diode (Four segments). These coordinates will be dependent upon the position of a laser spot falling onto the surface of the segmented photo-diode. I hope to obtain a value between (0-5V) for X and (0-5V) for Y.

The circuit I based my design upon used a dual supply (+5/-5V). In my application I am using a micro-controller with a 5V rail. The design would also benefit from a single supply if the output was a value between 0 and 5V as it would be compatible with micro-controller's ADC input range. I would therefore like to run the circuit from a single supply and use a rail-to-rail op-amp to to remove the need for extra circuitry.

I've tried a few different simulations where I've attempted to offset the output by 2.5V using a simple voltage divider, but the results are not what I expected.

Can somebody explain to me why the result is this way and what I can do to obtain a 2.5V output when inputs (A, B, C and D) are 0V.


texts:
I wish to measure the rotational speed and electrical current used of/by industrial components. Those components are driven by strong electric motors. The solution should be cheap and fast to implement and I want to use a raspberry pi to collect the data (with c++ or c#) and visualize it, either with an attached screen or via a web interface. There are likely 30 or so sensors to be installed at most.

The main problem here is the range. The components are transport conveyor belts that may run quite a long distance, possibly up to several hundred meters and are, as stated, in an electromagnetic noisy environment with the heavy duty motors. I have no experience with such communication at all and I was looking at I2C and SPI as possible solutions, since they natively allow several slaves, which fits my requirements. I don't want to use multiple PIs since that'd drive the costs up considerably and still leaves me with the problem of communication (at this stage probably ethernet with a max segment length of 100m) and expensive networking hardware (switches and probably media converters (copper - optical fibre) or repeaters for the range requirements), blowing the whole thing out of proportion.

I had a look at things and found stuff like this, referencing bus buffers/voltage boosters like the P82B96 and the differential bus buffer PCA9615. However non state the maximum length that they allow for and if that fits into my requirements. The PCA9615 doc states it allows for at least 3m in 1MHz mode, longer with less throughput. If this is 'long range', then I don't know if I2C is even applicable for my 500m or so range requirements. I imagine since I only want to send data from 30 or so sensors every few tens of milliseconds and that data only consists of a 16bit number, 100kHz is plenty fast enough.

I could possibly add multiple bus buffers/repeaters (P82B96) in line and keep it relatively cheap, but I don't know what that'd do with the signal run times or what effect that has on the system as a whole. Since the master queries the slaves, collisions should not be an issue since I can just wait a few milliseconds after receiving/not receiving data from each slave.

What I want is a rugged solution to get some numbers from some A/D converters to my raspberry over a long distance and I haven't got the faintest idea how to do that. There is probably some component that takes i2c and sends it over a high voltage, long range bus that I don't know of.

I really appreciate your help, I'm a programmer and not an electrical engineer and would really like some input on this problem.


texts: Calculating voltages of output and feedback voltage divider in OpAmp circuit

texts: I've been trying to calculate Vout as shown in the diagram, but I am struggling to understand the way that the circuit is wired. I need to calculate it for switch S in the lower and upper position. I realize that there is no current flowing through the virtual ground. I am confused as to why Vout, Vin, and R4 are not connected, and what "upper" and "lower" position means for the switch.


texts: Bigger GPS antenna better or more efficient?

texts:
I have the choice between:

35x35mm GPS antenna 71% efficiency glonass, tested on 70x70 GND plane
60% gps
25x25mm GPS antenna 83% GPS, 84% glonass, tested on 50x50 GND plane

I have read somewhere by a GPS manufacturer that antenna size is more important than efficiency but I feel doubtful about that. Would like to hear your thoughts.


texts: what is type of this RoHS LCD ( Any datasheet)?

texts:
I have one  18 pin LCD with this information:
1Qcu099-FLYG-GBW
So i don't know what type of the LCD is this and have not find any datasheet form google, So It's picture is here:

If have more information for It's model in Proteus and any driver library for AVR micro's or any datasheet, will be very useful for us.

Edited:

Dose it datasheet is here:
wh2004l

if yes, so any AVR library for running it's (wh2004l) with ST7066 Controller IC ?

Thanks a lot.


texts:
I just received an RFID reader from Parallax (#28440) to play with, and am having some problems getting it to send me data.  I'm interfacing it with the mbed microcontroller that I also just received.

The RFID reader interfaces via RS232 (5V level), so that matches my mbed serial port perfectly.  I have written test code on the mbed side so I know my RS232 code works.  However, whenever I send commands to the reader (e.g. "!RW\x0F"), I get result codes that aren't even in the documentation.  Specifically, most of the time I get back 0xE1 or 0xF8, when the actual result codes should be something like 0x01 - 0x07.

What's annoying is that their documentation doesn't give any timing tables, so I'm just guessing when I send all of the data at once and read immediately.  I've tried different time delays, and nothing works.

I am powering both mbed and RFID reader from the USB port.  Since USB supplies 500mA without external power, and the mbed uses 100ma and the RFID reader uses < 200mA, I figure I have plenty of headroom.  Perhaps tomorrow I should hook up the lab supply.

Has anyone here used this reader with reasonable success?


texts: Cost vs quality and performance of H-bridge

texts:
I'm working on a project where low cost and small BOM is just as important as optimal functionality. The goal is to drive a cheap DC motor (aka 'yellow motor'), in two directions, optionally with PWM.

We drive both a microcontroller and this motor from a regulated 3.3V source, which is able to provide more than enough current. The MCU (obviously) controls the motor direction. The motor consumes ±60mA when free running, which I think is pretty close to what it will be doing in the actual product (light load).

If I'd take the 'safe' route, I'd use the TI DRV8837 H-bridge IC and get a really small BOM and tiny footprint and be done with it. The unit price on a 3K reel for this on Digi-Key is €0,33. This is about 7% of the total product cost (± €5,-).

So IMO there is a case to look into a basic H-bridge made from transistors. For a BJT solution, I'd need the following:

2x NPN
2x PNP
4x back EMF Schottky diode
4x base R

When I choose the cheapest parts on Digi-Key for 3K reels, I get SOT-23 3904/6 transistors, some SOD-123, MINIMELF or SOT-23 Schottky diodes and a bag full of 0402 1K resistors, which would add up to only €0,16. That's less than half the price. Using GP 4148 type diodes would save me another 2 cents.

Using 2 P/N MOSFETs pairs, I could drop the base resistors, altough when I search for the optimal solution, I would ideally need gate resistors AND pull-downs. Also, there many questions on this board regarding the need for back-EMF Schottkies in parallel with the MOSFETs, when there are body-diodes in the MOSFET, too. My question is, would the body-diode inside the MOSFETs be good enough for this particular situation? Let's assume not and look for the cheapest parts again:

2x 2N7002    2 * €0,024
2x BSS84     2 * €0,038
4x Schottky  2 * €0,022

This adds up to €0,17 even with some resistors thrown in. So I guess using MOSFETs is just about as economically attractive as using BJTs. But again, dropping the back-EMF diodes would save a lot.

Say we would drop the (optional) requirement to PWM the drive signals, then the amount of switching would be extremely low. How much an impact would back-EMF have considering the circumstances?

-- update

Using a pair of dual Schottky common anode/cathode diodes in SOT-23-3, I can shave another 4 cents off, but adds another unique part to the BOM.


texts: Rated voltages for the Cage clamp connectors?

texts:
what does the rated voltage for a connector means? How should we select the connector for a 230V AC application?
Let us say can I use this connector for my 230V AV application?

https://www.phoenixcontact.com/online/portal/de/?uri=pxc-oc-itemdetail:pid=1904969&library=dede&pcck=P-11-01-05&tab=1&selectedCategory=ALL#Materialangaben-Geh%C3%A4use


texts: Gain error calculation for op-amp circuit in inverting configuration

texts:
For an inverting op-amp, calculate minimum gain that is required for the op-amp to achieve a gain error of 1%, if the required closed-loop DC gain is -9.
If the input resistance R1 is 1Kohm,find the feedback resistance R2 that achieves the required gain of closed loop.
Calculate the settling time, if the amplifier is applied a small step input and the response reaches 94% of it's final steady-state value. The op-amp, in open-loop condition, assumed to have only a single dominant pole at ω−3dB=6M Rad/Sec.


texts: Why are current transformers used in power stations?

texts:
I read that surge arresters in power stations suppress the high incoming voltage and the output passes on to the current transformer.
If surge arrester already reduced the voltage then why is the current transformer needed?
The reason I am asking this question because Ohm's Law states that: V∝I.

Surge arrester.

Current transformer.
EDIT 1:
Why surge arresters are used in electric power distribution plants before current transformer?


texts: I am working on embedded systems as beginner and have come across files like start.s or cstart files that run before main() function begins. What is the purpose of these or similar files? What information we are telling the system? I've heard of initialization but don't know exactly what that is.


texts: How to choose the suitable battery for 6 stepper motors?

texts:
I am new to electronics and trying to build a robot that uses 6 stepper motors.
I bought 6 of this stepper motor and used Pololu stepper motor driver A4988 to drive them but I have an issue with the power supply. The datasheet says that the motor operates at 12V , 0.33A current. My application requires that only one motor works at a time, no overlap between any 2 of them, so I assumed that a 12v 1A battery will do the job.

I connected the circuit with Arduino for 1 motor and powered it with the battery and it worked well, but when I connected all of the 6 motors, no one worked, instead, I heard some noise for 2-3 seconds.

When I tested 1 motor, I noticed that when the motor is powered -not receiving commands from Arduino yet to move- the shaft is holding -I can't rotate it with my hand- so it seems that it is drawing current and when I connect all of the 6 altogether without moving, they require more current than the battery provide.

So I think that the motors did not work because I mischoosed the Battery, if so, I need your help to choose the suitable power supply please.
Any help will be appreciated. Thanks a lot.


texts: Oscillator for High Voltage Transformer: RLC or Blocking Oscillator

texts:
What type of oscillator is being used in the schematic? How is that particular oscillator working in this circuit?

I'm less than confident with oscillator theory, and I can't tell if this is RLC or a blocking oscillator. It reminded me of some joule theif circuits I've seen, but overall I can't make heads or tails of this. If you could include a brief summary of how the thing works, that would be greatly appreciated.


texts: Is it possible to somehow revive an AGM battery, that quickly loses voltage when used?

texts:
I have a GLP 120-12 AGM battery, this thing to be exact:

https://glpower.eu/produkt/glp-120-12/

It's a 120 amps battery, and it is about 26 months old. All of a sudden, I noticed that the battery is holding only about 10-15% of it's designed capacity. The voltage drops from 12.8 to 10.5 within half an hour when I'm draining about 100 W of power out of it, and after that, it also rises back quickly to 12.8 V, it looks more or less like this:

Draining (100 W):
Start => 12.8 V
5 minutes => 12.5 V (and it stays that way for another 20 minutes or so)
25 minutes => 12.4 ... 12.2 ... 11.9 all down to 10.5 in a minute or two

Charging (10 Amps):
Start => 11.5 V (after my inverter disconnects at 10.5 V, the battery gets back to about 11.5 V, with no load)
30 minutes => The charger stops, and it reads 12.8 V (or slightly more)

Right now, I measured the voltage (fully charged a week ago and disconnected from the inverter,)) and it reads 12.8 V as if fully charged.

I'm wondering if I could somehow revive it? Are there any chargers or other devices that could somehow restore at least part of the missing capacity? Or is it a lost cause?

EDIT:

Just to let those that may be reading this know...

I was able to recover some of the lost juice (20-30%) by using a Novitec 'Megapulse' desulfator (cost ~ 70 euro). It made the battery somewhat usable again after about three weeks.


texts:
One thing I've never quite understood about noise specifications is what happens if your circuit uses DC only -- yet all specifications for noise make reference to a bandwidth.

I have an instrumentation amplifier. Let's say the thing I'm measuring is a DAC, with a spec'd noise level of -149dBm/Hz (== 7.1nV/rtHz if I math'd correctly...), and the instrumentation amp has an input voltage noise of 3.2 nV/rtHz. The gain is set fixed at 5.

My question is, since the DAC is outputting DC voltages, what "bandwidth" do you use if you want to calculate the Vrms noise of the circuit?


texts:
My daughter wants to do a science fair experiment that involves reading the electrical signals in plants, but the cost of a multi voltmeter with data logging is very high. Can anyone suggest a setup for less than $100? Maybe she doesn't need as complicated a set up if she tests one plant at a time?  But I believe that the sampling rate has to be at least 3000 s/sec.

Here's a setup for a similar experiment:
A PXI-4071 digital multimeter (National Instruments, Austin, TX, USA) connected to .2-mm-thick non-polarizable reversible Ag/AgCl electrodes was used to record the digital data. The PXI-4071 high-resolution digital multimeter delivers fast voltage measurements from 10 nV to 1000 V, current measurements from 1 pA to 3 A and resistance measurements from 10 µΩ to 5 GΩ. A

Update: One of the researchers in this field answered my daughter's email and said that she could use a KEITHLEY DMM.  Would that still require an amplifier? The only affordable ones on ebay (models 169, 177, 179) only have a digital read-out, no PC interface. I'm guessing she needs some sort of output recording device, like an oscilloscope? What about a Radio Shack MM with PC interface and op-amp (on a breadboard?)?

UPDATE: She ended up using a RS digital multimeter w/PC interface. The software was easy to use and the data could be saved to text files on the computer. For each test, the DMM took a reading every second for 100 seconds (there are other options too). The MM was set to record mA.  I chlorided 30 gauge silver wires with bleach for the electrodes.  Those worked OK, but maybe could have been thicker and not bent as much. The DMM did measure a strong reaction from the plant when it was stressed with high heat (brass wire attached to brass woodburning pen) applied for 5 sec. The baseline voltage seemed to vary alot from day to day (over 20 days), but I'm thinking that's because the electrode was touching a different leaf or part of a leaf on each day.  Next time, it should be in the same place for each plant over all the days.  Thanks for everyone's advice!


texts: Why wont my opamp gain properly? (schematic attached)

texts:
I am trying to take a input signal which will shift between 1-5Hz and amplify only the AC portion of the signal (0.02V pk-pk, ~3 volt offset). The whole circuit has to run on 3.3v single supply DC. I am passing the input signal through a Highpass filter at f=0.5Hz to do ac coupling and then though an amplified low pass filter f=5hz. I am them amplifying the output of the unity gain using a regular inverting amplifier but I am not seeing any amplification. I am attaching the output:

Can anyone explain why I am not seeing any output wave at all? My input signal is ~7mV and I would like as large of an amplification as I can in my 3.3 voltage constraints. It looks like my filters are working fine since the AC analysis shows the expected results and I am able to read a sin wave after the filtration.

Also is this the proper way of AC-coupling the signal?

[EDIT: fixed the resistor designators and set R6 to go to VG instead of G. Still not seeing final signal]


texts:
I'm building an 8-bit computer using the Ben Eater's videos and I would like to improve the ALU, e.g. add nand bitwise operation because every logic gates can be built from this.

But I ask myself if it would be possible to have shift (left/right) operation using this nand gate?


texts: Wire Two 12v Batteries Together in Parallel With Solar Panel and Raspberry Pi

texts:
Please excuse my circuit below.  I am a high school robotics teacher, self taught in electronics, so I may have used some incorrect symbols and configurations.

I have a Raspberry Pi 3 that has a custom Pi Hat controlling a 12V solenoid.  The system seems to draw about 4W so I am trying to expand my battery from one to two 12V 18Ah cells in order to keep both of the SLA batteries charged above 80%.  Initial testing with one drew the charge down to about 60% overnight which, it is my understanding, is not advisable.  My solution is to add another battery and wire in parallel.  I want to confirm that the design of this circuit will work.  The Charge controller connects to the solar panel and the battery separately.  The RPi is powered with a USB connection.  The Pi Hat passes the 12V to the solenoid to open it using a GPIO pin attached to a transistor.  This means that the solenoid is only using power for about 20 minutes a day.

simulate this circuit – Schematic created using CircuitLab

Does this setup look correct or are there any other considerations before I put this together?  Thank you for any suggestions.


texts:
Is it possible to blink an LED using just a capacitor? (and maybe a resistor).

For example, if I want to LED to blink once every 2 seconds. Is that possible?

I know it can be done with a 555 as well as with a capacitor and transistor.


texts: Are there any advantages to using rigid RF coaxial cables?

texts:
While watching this Signal Path video, I came across this shot:

I saw few rigid coaxial cables there and so I started wondering what might their advantages be. I could only find disadvantages:

They're expensive
Limited in available angles 45° or 90°. Otherwise they're not easy to bend compared to the other cable types
Sold in sections so we may need to always join them
Prone to corrosion

The only advantage seem to be higher power capability.

So, are there any advantages to using rigid RF coaxial cables?


texts: Reduce Flyback Reflected Voltage Ringing?

texts:
I have a step-up flyback design with the following parameters:

\$V_{in}=24V\$
\$V_{o}=150-350V\$
\$P=15W\$
\$N_{ps-ratio}=1:7\$

The transformer is not ideal with 1:7 and the inductance is a bit off, but it is what i made and soldered in a way it is difficult to remove. with a \$Vo< 180V\$, regardless of load, the transistor stays cool to the touch. Above ~180V the system starts to make an audible buzz and the transistor becomes hotter, ~60C.

After doing a lot of investigation, I believe it is related to the reflected output ringing going below ground and turning on and off the internal diode? You can see the ringing in the attached image.

Some issues I have ruled out via investigation:

The transformer is made well from the stand point I do not believe there is any arc over etc.
It also has an adequate core gap and should not be saturating, this is also reinforced by the linear looking current ramp that is visable using the FET \$R_{ds}\$

The noise may also be unrelated to this, I was thinking sub harmonic oscillation, but It looks like my duty cycle is typically below 50% and this should be operating in DCM reguardless.

Is there any way to reduce the ringing without reducing the reflected voltage thus keeping the FET cooler?

Updates:
Below is the gate image, everything looks alright there.
I tried to measure current through the FET, using the 0.042m Ohm feedback my scope just sees noise. Unfortunately everything is soldered in kind of tight and with power planes there is not a great way to insert a different resistance somewhere else in the chain.

I also attached a slightly modified schematic, the switching freq is different, and some of the capacitance is not identical, but it is close enough to the as built for you guys.

Below is also an earlier image of the board:


texts: Simple Differentiator with OpAmp - response function

texts:
Ok, I have a differentiator with an OpAmp, a resistor and a capacitor. I've calculated the response function, and I've written it in the picture.

Now, the OpAmp has a single-pole response function, that is also on the paper, and I need to see how will the final Amplitude and Phase characteristics look like (Bode Plots of course). When we substitute the two expressions, we get:

\$ \displaystyle A(s)=\frac{A_0s}{s^2+s(\omega_p + \frac{1}{RC})+\frac{\omega_p(A_0+1)}{RC}} \$

Now we have a quadratic function, and in the general case, this will look strange on a bode plot if there aren't real solutions to the equation.

I mean, looking at the theory, and what I would suppose is that this should be a nice differentiator, with an amplitude bode plot looking normally, just with a pole on higher frequencies, sth like:

But I have no idea if this is actually right, and if yes, why. Any help? :)


texts: Why LM2596 buck converter output current is low when used as a mobile charger?

texts:
I am having LM2596 buck converter which is capable of providing 3A current and my input source is capable of providing 5A which is a transformer.

but when i used the buck converter to charge my android phone which can draw 2A current from the ac charger, only 400mA is flowing through my mobile phone. I have measured it using USB tester device.
Can anyone help me to understand or make it to provide higher current for mobile charging?


texts: Why is a caseless PC not an EMI problem?

texts:
As I understand it, the case of a PC is metal so that it can form an EMI enclosure around the electronic parts.  My view is reinforced by there being conductive fingerstrips around the mating edges.

This is a home built PC without any form of case:-

I suspect that the black backboard with the four arms is scratch built too.  It's probably plywood.  This is 100s of Watts (motherboard + 2 high end GPUs) of totally exposed electronics running at ~4GHz spread out over at least a square foot.  That's got to be an ariel somehow.  There are many other examples if you Google "wall mounted PC".  And there are of course all of the fashionable single board computers like Raspberry Pis running inside shoe boxes at 1.2GHz.  Or glass PC cases.

Since EMI regulations get stricter all of the time, I thought that EMI is a problem.  I read that it can be a major headache for equipment designers.  Is it not really the problem the authorities make out? Or will this PC's owner never receive a mobile signal, be unable to watch clear TV or be sterilised within hours?

I've read EMI/RFI emissions and computer cases, Non-metal cases and emi standards/best practices for PC cases.  The general tone of answers to these  questions speaks to enclosing the PC in a shield of some sort, be it metal or conductive paint/ tape.  Why bother?


texts: What component to use for audio signal switching?

texts:
I'm looking to build a guitar pedal switcher based on a Raspberry Pi or Arduino (have not yet decided, but I have an unused Raspberry around and I lean towards that). Anyway, digital logic.

Now, I need to switch audio signal obviously and I need to do it quietly (both physical silence and electrical silence). Please note that the signal is line level throughout most of the build, except for the input which is much lower. I will probably have 2 or 3 loops before the preamp so those may not encounter line level signal.

From what I read and know, so far, mechanical relays are not really an option due to the clicking noise they make. I also read something about FETs, but that's a bit out of my league and I would appreciate any info on these.

PS: I will probably use different power rails for the digital and analog paths.

PS2: The whole thing will be mounted in a 1U rack enclosure, so please tell me if I should take into consideration any thermal issues.


texts: How do wireless receivers reject noise created by the original signal reflecting off walls?

texts:
When a transmitter emits an RF signal it reflects and bounces around all over. If a receiver is line-of-sight with that transmitter then the original signal will hit it first but signals bouncing off walls may hit it soon there-after and thus create noise on the same frequency band with the exact same information but shifted in time. This is called Multi-Path interference from what I've been searching.

How does the receive differentiate and extract the original signal when its being mixed with thousands of reflections?


texts:
Found a switch for a project, and want to make sure I understand it correctly.

This is the switch:
(Mini-Circuits SWMA-2-50DR+).

Now, it has a TTL driver circuit with the inputs +5V, -5V, and TTL IN.
The TTL IN has low threshold 0-0.8V and high threshold 2-5V.

Will it be possible to control the switch with a microcontroller that alternates its output between 0V and 5V, and is directly connected to the TTL IN input? Or is it necessary with some kind of circuit in between?


texts:
I am building a binary for ARM using GCC and Crossworks. I have a secondary binary image that needs to be loaded to another IC during start up.

I like to integrate this binary to my tool-chain, in other words, I make this binary part of my image and every time I build this binary gets integrated into the final binary file that will be loaded to the CPU. What is the best practice for this?

Thx


texts: How does common mode range include the negative rail?

texts:
How do the devices like AD8220 handle the common mode voltage equal to the negative rail or even lower voltage (Take a look at figure 30 of AD8220 datasheet) ?

Does the operation of the amplifier degrade if the Vcm be close to the end of its range? Or it will work good as long as Vcm be within the range no matter where in the range?


texts: Interfacing to End Of Line Resistor In Security System

texts:
Off the shelf security consoles utilize an end of line resistor to monitor the integrity of the cable runs, usually a 2 KOhm resistor.

Is there a more or less standard interface circuit that most of them use to sense the line resistance? Or does everybody do their own thing? I am thinking of maybe building my own.

Voltage divider + 2 op-amps?
Current source + 2 op-amps?
Voltage divider + ADC + MCU?
Current source + ADC + MCU?


texts: Finding Voltage Thevenin via short circuit

texts:
I found this question online where \$ R_1 = R_2 = R_3 = R_4 = 15 \Omega \$ and \$V_s = 15 V\$

Finding \$R_{th}\$ first, we short circuit \$V_s\$,

We know \$R_1\$ and \$R_2\$ are in parallel which is then in series with \$R_3\$ which is then in parallel with \$R_4\$.

Substituting 15 ohms for all R values we get \$R_{th} = 9 \Omega\$

Now we want to find \$V_th\$
I attempt to do this by using the \$i_{sc}\$ short circuit method. By connecting the two terminals, I think we are short circuiting the \$R_4\$ wire
So, applying ohm's law: \$V_{s} = R_{1,2,3} * i_{sc}\$

where \$R_{1,2,3}\$ is the equivalent resistance of \$R_1\$, \$R_2\$, \$R_3\$

Finding \$R_{1,2,3}\$, \$R_{1,2,3} = 22.5 \Omega\$

Solving for \$I_{sc}\$

$$V_S = R_{1,2,3} * i_{sc}$$

$$15V = 22.5\Omega *  i_{sc}$$

$$i_{sc} = \frac {2}{3}$$

So, \$V_{th}\$ should just be \$R_{Th}\$ times \$i_{sc}\$

$$V = R_{Th} * i_{sc}$$

$$V = 9\Omega * \frac {2}{3}$$

$$V = 6V$$

However, my answer is incorrect(as given by the answer checker. Can someone please tell me where I went wrong?


texts: Simple RF-powered LED circuit works on bread board but not perf board

texts:
I am trying to make a training tool that lights up when a radio is transmitting a few inches away from the antenna. The circuit works great on my bread board, but as soon as I transfer it to a perf board, it does not work.

I have tested the circuit and I have good connections at all points. I used my Precision Variable DC Power Supply to apply 1.8 V and it lights up just fine across the circuit. Any advice how to make this work? I have a basic skill level, but lots of resources available. Thank you.

simulate this circuit – Schematic created using CircuitLab


texts: What is this chip? Labeled "ATMEL 60824C08"

texts: This chip came from a box of assorted ICs from ebay. I have looked up the code on the top and I can't work out what this actually is.


texts: ordinary power strips protections for power outlet IOT

texts:
I am trying to build some power outlet device based of this to built some thing like this:

also i like to add it some normal eclectic device protection (ordinary power strips 220v/10A for TV or refrigerator ) like this :

  Power strips often include a circuit breaker to interrupt the electric
  current in case of an overload or a short circuit. Some power strips
  provide protection against electrical power surges. Typical housing
  styles include strip, rack-mount, under-monitor and direct plug-in.

so i found this or this for overload protection circuit , and some Over-Current-Protection circuit and this as surge protection but not sure what is the proper circuit and protection for this kind usage and could combine them to do all in one circuit!.
so do those circuits fine for this usage?

So i asked here to know your viewpoints.

Thanks.


texts: I'm learning to use Kicad and got stuck trying to add a DPDT switch to my schematic. When I try to add it, I couldn't find one in the components library when I search for it. How can I add it to my schematic on Kicad?


texts: Does this capacitor discharge? SCR and capacitor doubts

texts:
I'm having some doubts about this circuit and about capacitors charge/discharge in general

SCR CIRCUIT; Igt= 100MicroAmps;Vgt = 0.7V

Ok I have like 5 questions

1) Is flowing current through R2 and R3 before C1 gets fully charged?(I know in t=0 c1 will be like a wire but as long as it gets more charged it will have more oposition to current so will current split or it will it go completely through capacitor until its charged?), if the current does split will it charge as fast as if they werent there? using the famous exponential equation for RC,(R1=R)?
2) Ignoring the scr part, Will c1 charge until Vcc or will it charge until the voltage that R2+R3 will have(around 35V)? or first till 90V and then when it gets like open it will discharge until 35V?

3)Doing the math I get 700MicroAmps trhough R3 and 800Trhough R2( since I have fixed 0.7V on R3 and adding it up with 100MicroAmps through the gate I get 800Micros through R2)so that is 3.34Volts for Vc to activate the SCR, my doubt is: since I'm asked for the graph of voltage in C1( or AK)  will C1 discharge by the switching since SCR will get activated?(to 0Volts or VFon I don't know) which will get on 0V along time.
or can the charge(maybe it will try to charge more and all current will go through it to charge it) or discharge of c1 (or any other component in this circuit) get IH lower , causing a loop of charge/discharge in the graph?

4)Imagining SCR is not 100% ideal and it doesn't have 0V, how can I know if current will flow through R2 and R3 as well?will it be lower or higher than AK current, maybe 50-50?

5)Imagining SCR is not there and instead of R3 there is another Capacitor identically to C1, how can I know the time (from the time I connect the source) of charge of this C2, do I have to assume that c1 is charged first and then c2 so I will have to add up the times by separate(tc1 + tc2)? or is there any kind of relationship between them? since C2 would have more resistance and hence more time of charge... what is the way of knowing it with certainty?

I apologize if I didn't express my questions correctly or clearly, and also if I asked to many questions in 1 threat, many thanks to everyone that can help me to watch this clear!!


texts: Why using a pointer interfacing LCD HD44780

texts:
I'm trying to interface with an LCD display (HD44780). I came across a tutorial on the internet to send characters and strings to the display. Everything went well and it works fine but I have no idea why a pointer is used. I'm not quite familiar with pointer in C. I know that thay can hold addresses of variables etc.

Can someone explain me why it is used to send data to the LCD and what it exactly does in the code below?

#define lcdE    0x04
#define lcdRW   0x02
#define lcdRS   0x01
#define lcdport PORTC       //port where LCD is connected
#define lcdDIR  DDRC

void lcd_init(void);                                //initialize
void cmd_to_lcd(unsigned char cmd);                 //send command to LCD display
void char_to_lcd(unsigned char character);          //send character to LCD display
void set_cursor_to_1st_line(void);                  //set cursor at the beginning of the first line
void set_cursor_to_2nd_line(void);                  //set cursos at the beginning of the second line
void clear_display(void);                           //clear display and return to home position
void string_to_lcd(unsigned char *ptr);             //send a string to LCD display

void cmd_to_lcd(unsigned char cmd)
{
    unsigned char temp = 0;
    temp = cmd;                         //store cmd in temp
    cmd &= 0xF0;                        // clear lower nibble
    lcdport &= ~(lcdRS|lcdRW);          //pull RS and RW low
    lcdport |= lcdE;                    //pull E high
    lcdport = cmd | lcdE;               //output cmd and hold E high
    _delay_us(10);
    lcdport &= ~(lcdE);                 //pull E low
    _delay_us(10);
    cmd = ((temp << 4) & 0xF0);         //shift command 4 left and clear lower nibble (send lower nibble of cmd)
    lcdport |= lcdE;                    //pull E high
    lcdport = cmd | lcdE;               //output cmd and hold E high
    _delay_us(10);
    lcdport &= ~(lcdE);                 //pull E low
    _delay_us(50);
}

void lcd_init(void)
{
    lcdDIR = 0xFF;                      //port C as output
    _delay_ms(30);                      //wait for lcd internal init
    cmd_to_lcd(0x28);                   //4-bits, 2 lines, 5x8 dots
    _delay_us(10);
    cmd_to_lcd(0x0C);                   //turn on display, cursor, cursor blink
    _delay_us(10);
    cmd_to_lcd(0x06);                   //increment AC on operation and move set cursor move to right
    _delay_us(10);
    cmd_to_lcd(0x01);                   //clear screen and move to home position
    _delay_ms(2);
}

void char_to_lcd(unsigned char character)
{
    unsigned char temp = 0;
    temp = character;
    character &= 0xF0;
    lcdport |= lcdRS;                   //RS = 1: data register
    lcdport &= ~(lcdRW);                //RW = 0: write operation
    lcdport |= lcdE;
    lcdport = character | (lcdRS | lcdE);
    _delay_us(10);
    lcdport &= ~(lcdE);
    character = ((temp << 4) & 0xF0);
    lcdport |= lcdE;
    lcdport = character | (lcdRS | lcdE);
    _delay_us(10);
    lcdport &= ~(lcdE);
    _delay_us(50);
}

void string_to_lcd(unsigned char *ptr)
{
    while(*ptr)
    {
        char_to_lcd(*ptr);
        ptr++;
    }
}


texts:
I've seen this following post regarding using the speakers as a microphone:
https://skeptics.stackexchange.com/questions/5664/can-a-computer-be-hacked-to-use-a-connected-speaker-as-a-microphone

There are some things I don't understand about it. He says that an amplifier doesn't pass any signal from it's output to it's input. Is this correct? if I have an amplifier such that output=100*input and I force 100*x on the output, won't I get x in the input?

To my understanding, speakers are always plugged through an amplifier to the sound card. The question is whether the amplifier resides in the sound card (where it is also controllable and we can lower it) or in the speaker. In any way, say that when I produce a voltage of x from the sound card I get some sound signal level in the air of gx right on the speakers (g in the appropriate units). Now if I produce a sound in the air that is equal to gx right on the speakers I will get the voltage level x to the sound card. So reducing the amplifier is just a matter of reducing this g. Is this the accurate explanation? and not the explanation inside the link?


texts:
I was looking through a datasheet for the LT3083 regulator and in the typical applications sections this caught my eye:

Provided input/output ratings could easily lead to over 20W being dissipated on the second regulator. I'm looking for some ballpark figures on the required heatsinking (i.e. size of the heatsink or perhaps active cooling requirements) to make this example work with the TO-220 package (3C/W junction-case thermal resistance).


texts:
I have a problem with my mppt solar voltage regulator. I have a campervan with three 320 W solar panels (Voc 40.8 V, Vmpp 33.3 V) connected in series on the roof, and two 260 Ah, 12 V AGM batteries connected in series to get a 24 V system. I've set the correct absorption (28.5 V) and float (27.4 V) charge voltages (as per battery specs), and the MPPT regulator can handle up to 145 V Voc and has an MPPT range of 30-115 V, with up to 60 A charging current, so it should be able to handle the solar panels perfectly.

The problem is, when I move the van from a shadowed area to a well lit one, I get a two second voltage surge from the MPPT charger that goes over 30-31 V. This makes my inverter overvoltage protection trigger, cutting AC power during those two seconds. It's very annoying because when power comes back some appliances automatically turn on.

Is there anything I can do to force an upper limit on the regulator output voltage, without compromising efficiency?


texts:
With the MCP73871, the load regulation is 0.08%. Does that mean it expects the battery voltage to increase strictly monotonically? That is, if the device consumes 2000mA at 5V (around 3000mA at 3.7V) from the battery, the MCP73871 will simply shut off entirely, making the load consume solely from the battery and the battery not draw current from the MCP73871 at all?

Thanks


texts:
I've been working on an audio amplifier circuit and found the following circuit.

If my power supply generates +10V, -10V and GND would there be any noticeable change in the basic functionality of the circuit by implementing the voltages I do have accordingly?


texts: How to align rotor with stator d axis for pmsm motor for pmsm foc?

texts:
I am trying to develop an algorithm for field-oriented control of pmsm motor with hall sensors as position feedback.

    I am measuring the period of hall signals and calculating speed from it.

    However, when I make the transition from ramp control to hall sensor feedback, my motor slows down and stops.

    What do I need to do to align the motor d axis with the rotor?

Any help would be appreciated.


texts: Will a 24/7 plugged-in power cable kill my laptop's battery?

texts:
I'm using a Lenovo Y50-70 and Conversation mode is always turned on (plugged-in, not charging mode).

Specifically, my question is: Will it damage the battery (or the laptop) if I leave the power cable plugged in even when the laptop is turned off?

And in a more general way: is it better to unplug an electrical device when I'm not using it?

*My laptop's battery is Lithium-ion polymer 4-cell (54Wh) battery


texts: why current flow through ground wires of submersible 3 phase motor?

texts:
I have a 150 KW 3-phase submersible motor with 2 cables. Each cable is (3p + 1 ground).

When connected the 2 ground wires at the same point, I read about 15 A on the ground cable. Why current flow through ground wires of submersible 3 phase motor?
I check this for many motors in different places and I found the same result.


texts:
I have an ARM-M0+ (SAMD21G18).

I have a project that has a bootloader and another with application.

When I try to go to debugging I suspect the following:

the ROM is erased
application flashed only
the program goes to fault mode.

I guess this is because of VTOR thing and SP in address 0x00000.

I've searched the internet, and people suggest to use application alone... but then how?

Is there another way to prevent debugger from erasing bootloader area?


texts:
I have built the following circuit intended to be an amplifier.

When I hook the input up to my phone via a guitar cable and the output to a 4 ohm speaker it produces a lower volume than plugging the phone straight into the speakers. The voltages I measure over the resistors do not match up to the tutorial I followed. I have tried switching the transistor and capacitors to no avail. My battery measures at 8.8V.


texts: What's the proper name for "annular potentiometer"?

texts:
I'm looking for a potentiometer without the shaft. It should be like a ring, in annular shape, so it can be mounted on an existing shaft.

I don't find anything, but I'm afraid I'm not using the proper English word to describe such a component.


texts: How can I matrix switch multiple lines, including power?

texts:
I have devices with several similar boards, all of which are basic computers (with CPU, RAM and ROMs etc.). They all interface to the I/O unit via a standard connector, although the connectors aren't all wired the same, unfortunately. The I/O unit comprises of a switched mode PSU (+12V +5V -5V), various switches (tied to ground) and 15kHz RGB video.

I would like to use one I/O unit as a test rig, and be able to switch the lines accordingly for each board automatically. I will probably use an Atmel device to keep note of the configurations, as I have several spare.

My main issue is that some of the pins carry voltage. Unfortunately, even these vary from board to board. The PSU is rated at 15A on the +5V line, 3A on the +12V line and 1A on the -5V line, although I'm sure most of the boards don't draw anywhere near that amount of current (I seem to recall 5A being plenty for one board on the +5V line). There are quite a few lines on the connector.

All that I can think of is using relays, but as there are quite a few lines (around 60-70, I believe), that's an awful lot of relays!

Can anyone think of a solution?


texts: Is it possible to power STM32 Nucleo Boards from a 3.7 Lithium Ion battery?

texts:
I have a Lithium Ion Battery that produces 3.7 volts and i would like to use it to power my STM32L476RG Nucleo board to collect data on the ADC and push the data to SD Card.

I understand that i can power the Nucleo from external 5 volts but is there a way to power it on 3.7 Volts without needing a boost converter?


texts: Recently, Hackaday is talking a lot about the esp8266, a wifi to serial chip. I want to use the esp-03, a breakout with half-hole connectors that has 2mm pitch. Is there a breakout board that can turn that half hole connector into through hole connector so I can prototype on the breadboard? Or do I have to resort to different methods? Any suggestions?


texts: Bipolar stepper motor sequence, wiring and dual h bridge

texts:
Im facing some issues to figure out sequence of my bipolar(specifically) and unipolar stepper motor. However , I've managed to get Dual H Bridge but couldn't find out the example/documentation for the one i got.

I want to drive my bipolar stepper motor via dual h bridge using parallel port and unipolar via IC UN2003.

You're expert guidennce for pulse sequence and wiring identification will be truly appriciable. Thanks!!

Pictures

DUAL H BRIDGE : http://i.imgur.com/cUWSxfR.jpg

Stepper Motors scavenged from printers : http://i.imgur.com/7A0gixj.jpg


texts: What to do when you don't find an electric component in Proteus?

texts:
I am looking for this component: KSC1815. It is a NPN Epitaxial Silicon Transistor

The datasheet is here: http://www.futurlec.com/Transistors/C1815.shtml

But when I try to pick that component in Proteus:

It does not show up.

What can I do when I don't find a electric component in Proteus that I need to simulate? Thanks


texts: Biggest variable that is possible to define

texts: I have a lot of data to storage at very fast speed. I can't send them using serial becouse is too slow. I've tryed to use and external flash memory but due some library problem I can't reach writing speed I need. The only way, I've tryed, that work is to storate data in an array of 8 bit. But i've tested and found that maximum size I can define is 5000 (array[5000];). Now I have 256KB free memory for code on my MCU, and I need to storate 5KB of code and 200KB of data. But I can't define in the code 50 arrays. There's a way that can define an array bigger as I want? There is a way that define my arrays when code is executing?


texts: Diode between 5V pins of multiple USB connectors on dev board?

texts:
I know all dev boards are different but on a well designed dev board (from a major company like STM) do you think it's appropriate to add a diode to prevent the 5V pin on a secondary USB connector from "seeing" the 5V provided by the primary USB connector? What pros/cons are there to this?
E.g. in this picture, we see two USB connections both of which are capable of powering the board if connected on their own. The board is a NUCLEO-F303K8 (manual here) and it has two USB cables connected (the one, that I'm calling the primary one, on the left and the secondary one, on the right, where the USB wires have been broken out, soldered onto to a small bit of header and then connected to the appropriate pins on the dev board).

Here we can see a diode between the 5V of the secondary connector and the 5V pin of the board.
This seems sensible - I can imagine that's it's not good for the secondary connector to see the 5V of the primary connector if the primary connector is plugged in and powering the board.
Is this the case? But I also wonder about the voltage drop introduced by the diode. The diode is something like this 1N4001 which has "about 0.7V drop for typical usage". This would drop the 5V of the USB to 4.3V - well below the 4.75V lower threshold listed in the manual for powering the board via the 5V pin - and so make the secondary USB connector unsuitable for ever powering the board on its own.
And I see that there is no similar diode protecting the primary USB connector (either on the breadboard or the PCB).

And in-fact the manual has fairly explicit warnings about the order in which one should connect power to the 5V pin and then connect the primary USB (with dire warnings if you fail to follow their stated ordering - "the PC may be damaged or current supplied is limited by the PC").
So two issues really - I can't see that the secondary USB can provide the necessary minimum of 4.75V if the diode is in place and it looks like a risky business to have 5V coming from two different USB connectors at the same time.
I'm inclined to think the best thing to do is to get rid of the diode and only ever connect the 5V red jumper wire from the secondary USB connector iff the primary USB connector is not plugged in.
Sorry for letting this question get a bit meandering. I've just been looking at this tutorial (the source of the photo up above) and been wondering if the setup shown is really appropriate. The tutorial is by Shawn Hymel - his work is always super informative and educational and I'm sure any misunderstanding in set up or application is on my part.


texts: What is the effect of MOSFET switching frequency on PMSM FOC drive?

texts:
• I have developed FOC drive software for PMSM motor used in an electric scooter.
• Drive works fine but there is noise on the initial start-up. In order to remove it, I tried
many different approaches like estimating angle from hall sensors more precisely, increased
current loop sampling frequency but nothing gave the drive performance what I expected.
• Then I modified the PWM switching frequency from 15KHz to 20KHz and observed less noise in the
drive, But I am unable to conclude my observation, Kindly Help!!!!


texts: Reading RAM externally in a running system by intercepting the memory bus or replacing the RAM chips?

texts:
I wonder if it is possible to modify a consumer electronic system (TV, phone, embedded device, etc.) so that it is possible to read and possibly write the contents of its RAM chips while system is running, without adding any software to the target device.

I'm not very familiar with hardware, but I guess a solution could possibly involve soldering something on the pins of the RAM chip, so that signals are intercepted, and then "replaying" the writes to an internal RAM, effectively creating a synchronized copy of the device RAM.

The internal RAM could then have a second port that would allow the user to read it, for example via a controller exposing an USB mass storage interface.

Alternatively, without the second port, the controller could perhaps give the original device access to the internal RAM when it is writing, and instead replace reads with the reads issued by the user to examine the RAM when it is reading.

Or for DRAM chips refreshed by the controller, it could filter out all access except writes used for DRAM refresh (by detecting a refresh and then using a timer), and then pass examination reads at times when DRAM refresh is not happening.

An alternative design could be to replace the RAM chip with a dual ported RAM, and then wire the original port to the target device, and the other port to the controller allowing to read or write it.

This latter design would also allow to write the RAM in addition to reading.

Alternatively, one could maybe attempt to process the stream of RAM signals in software instead of sending it to a RAM chip, but it seems this would be far more complex and expensive due to the high data rate (which might require splitting the stream and processing it with a cluster of machines).

Precisely, the questions are:

Is it possible at all?
Is it feasible to do this on commercially produced motherboards with soldered RAM chips found on consumer electronic devices?
Are there any off-the-shelf devices that can do this?
If not, what would be the cheapest/simplest way of building a single copy of such a device with only read support? What about write support? (assuming everything beyond the target device and a normal PC has to be bought)

This is a general question regarding SRAM, DDR, LPDDR, GDDR, Rambus, etc. chips.


texts: Colpitts oscilator - purpose of voltage divider

texts:
I'm confused by the Colpitts oscillator shown below:

I've marked my understanding of the various components, but I'm having trouble understanding the tank circuit.

My understanding is that C1 and C2 form a voltage divider. However, I'm assuming Vin is coming from the emitter, between the two caps which seems unusual given the standard representation:

(source: learningaboutelectronics.com)

But intuitively I can see that the voltage is split between C1 and C2. But what is the purpose of this? From my understanding of tank circuits, L1 and C1 alone in parallel should resonate? Why is a voltage divider required?


texts: How to Implement Float Switch On/Off LEDs

texts:
I've previously built this circuit to control a submersible pump with a PIR sensor:

I'm now going to add a float switch to the circuit to prevent the pump running if the water level gets too low. I would like to also include a green LED when the switch is on (sufficient water level) and a red LED when its off (low water level).

The circuit would therefore look like this with the inclusion of a red LED, however I can't think how to implement the red LED to be on when the switch is off and then to turn off when the switch is on (the inverse of the green LED's behaviour). Any pointers would be appreciated.

Note: R1 is meant to be 47k and a 1N4004 diode is across the motor


texts: If energy is drained from a capacitor linearly, does capacitor voltage decrease linearly as well?

texts:
If a charged capacitor is connected to a current source and resistor as shown above, the resistor is constantly consuming 0.001J/s. If you were to make an energy-time graph of the capacitor, you would see a straight linear decrease.

These equations hold for a capacitor:

\$ I = C \frac{dV}{dt} \$ (1)

\$ V = I\frac{t}{C} + D \$ (2) <= this is a linear decrease of voltage
Thus, because I is also constant, you would see a straight linear decrease in a voltage-time graph as the capacitor is discharging.

However, the energy of a capacitor is

\$E = \frac{1}{2}CV^2\$ (3)

and the voltage is

\$ V = \sqrt{2 \frac{E}{C}} \$ (4)

If the energy inside the cap is decreasing linearly, how can the voltage be also decreasing linearly according to that equation?


texts: What is the plastic tubing that DIP's come in

texts:
I'm looking to protect some old vintage MOS chips that I own and I don't want this to sound like a stupid question, but I cannot find the name of the plastic tubing that DIP chips can be purchased in.

I've looked up things like "dip chip tube" or "chip plastic cover" but to no avail.

I have actually purchased some old 8-bit CPU's (all DIP's) that came in this kind of tubing that I'm looking for the others and it conforms to its shape.

Does anybody know what these are called and if they are available to buy empty?


texts: Extracting phase-shift and gain from a time series information

texts:
I have many files consisting input and output voltage signals for a linear filter circuit. For each file the input and output signal is at different constant frequency. All sampled for 2 sec duration with a sampling rate Fs. So basically by using a function generation each time I applied sinusoidal input signal Vin at a constant freq. to the input and I obtain a sinusoidal output. I want to plot the phase-shift versus frequency. Below is an example for 5Hz input in time-series.

By using the time domain data above how can I algorithmically extract the phase shift? What comes to my mind is to find the first maximum point for each sinusoid and the difference will reveal the phase shift. But I dont know how to implement this. And for the freq. vs amplitude I need to find the pk-pk values(because sinusoids have some offsets) and extract the ratio.

Is there a way to implement this?


texts: Pour-and-drain conformal coating as an alternative to potting

texts:
Is there a standard process to pour conformal coating, similar to potting, but then drain the excess? The benefit of draining the excess is to reduce weight and get better cooling.

From my limited experience, potting usually involves pouring a solid block of 2-part epoxy or urethane in an electronic enclosure. Even with thermal fillers, the thermal resistance is typically high which results in reduced cooling. 2-part potting compounds are required because the solid block won't air-cure and the 2-part compounds add to process costs.

Conformal coating on the other hand is typically sprayed (resulting in spray shadows) or dipped (which doesn't work for enclosures).

I've never seen it done but it makes sense to pour a 1-part low viscosity conformal coat using a process similar to potting but then remove the excess by either pumping out or draining the cavity. Like a dipping process, the excess would be recycled for subsequent parts. Since the resulting coat is thin, a 1-part air-cure compound can be used.

Does anybody have experience or comments?


texts: how to sense high frequency current and power sensing

texts:
Input

AC Voltage: 250V

Current:2A Max

Max Power out : 300W

AC frequency : 4MHz

Problem Statement is to measure power and sense current and alarm if exceeds certain limit

my approach :

step down AC voltage > feed to bridge rectifier > calculate its voltage

how to measure /  sense current ? as i have voltage, if i have current measured i can find power output

i am not seeing current sensing IC with bandwidth of 4MHz, even i doubt how transformers react to a 4Mhz input ?, even if i get a high BW current sense transformer how to measure current with of the shelf ICs(to construct an instumentation amp for I-V conversion)

first i want to simulate this approach on simulators like TINA or LT

kindly throw some light on approach to follow to measure high BW AC current sensing


texts: Are there any cases where single-cycle is better than pipelining?

texts:
I've been asked by my professor

  When pipelining is better than single-cyle MIPS CPU's?

I actually answered "always", but I'm not sure that's the correct answer. Excluding an increase in design complexity, and the added complexity in handling hazards, from the point of performances doesn't pipelining always give better (or equal) results?

EDIT: I omitted I was talking about the MIPS architecture.


texts: A good reference for modeling pmos transistors in LTspice?

texts:
I've been trying to learn how to use LTspice, and I'm attempting to create a model for a pFET I've been using/will use on a real board.  However, since my specific transistor isn't already in LTspice's collection (probably because it's a TI part...), I'm attempting to create the model myself.  I've found the standard.mos file, and while some of the arguments are easy enough to figure out (Ron, mfg, etc.), there are a few I can't figure out (Rs?  Vto?).

So, my question: is there a decent reference anywhere that says what all of these arguments are?  I can probably get real values from a datasheet if I know what to look for, and if not, I can make an educated guess.  Currently using LTspice IV for OS X if that makes any difference.


texts: Electric shock from cover of preamplifier

texts:
I'm using a Focusrite Scarlett as a preamplifier between my computer and amplifier. The preamp gets power only through a USB connection. Sometimes when I touch the cover of the preamp, I can hear a small "poof" from my speakers. I didn't realize those were mild electric shocks, until today, when I touched the cover and heard a loud "poof" at the same time as I felt that poof on my finger. So, the cover of my preamp is giving out small electric shocks.

The warranty on the preamp has expired and I'm happy with it otherwise, so I would prefer to keep it. On the other hand, I don't want to feel another shock like the one I felt (or burn down the house). I was thinking, is there an easy way to make the preamp safe? Like, can I go out and buy a grounding wire and connect that from the cover of the preamp to the radiator? Or something like that?


texts: Connection problem, BUS or Wire? - Altium Designer

texts:
I'm trying to make a panel with 1000 LEDs divided in two groups of 500 units and I want to put my schematic in A4 page. To do this I'm trying to use blocks, in this case 250 repeated blocks, separated in 2x125 blocks for each type of LED. But I have a problem with the connections. I already tried using wire, bus, bus+wire, but in all off tries I have problems when I compiled the project. Anyone can help me?

Regards,
Eduardo.


texts: I have a coil whose inductance will be changing continuously. I would like build a circuit to monitor the change in inductance continuously. Can I just use a RCL circuit and give it a sine wave of f Hz, and measure the voltage across the coil?


texts: How to demonstrate mathematically the conditions of reflection in transmission line?

texts:
We are all taught about transmission lines and its associates -- characteristic impedance, reflection, standing wave, etc. It is well known what happens when a transmission line is terminated with different types of impedances:

1) Open - reflection occurs

2) Shorted - reflection occurs but inverted

3) Equal to Zo - no reflection

4) Between Zo and open/short - partial reflection

So far, so good. Every textbook and other reference will tell you this. But I cannot find a straightforward explanation why it is like that. Some demonstrations show the charging of capacitors through inductors and how the end capacitor doubles voltage due to collapsed magnetic field in the inductor, etc., but I find it very confusing. So maybe a mathematical demonstration would be convincing.

How can we show mathematically, for instance, that when the load impedance Zl is equal to Zo then reflection is zero, and so on?


texts:
A friend gave me a Marine VHF Radio Receiver which is working badly, and asked me if I can look into it and try to repair it (I'm not going to charge him).

The first time the radio is turned on, the reception works OK, but after a few minutes the reception dies, and turning it off and on again immediately won't fix the issue. I have to wait a few more minutes with the radio turned off to again start receiving OK. The squeltch is always at minimun, receiving noise.

When the radio dies there is a high pitch noise coming out of the speaker. The external speaker connection is wired directly to the same internal speaker circuitry.

Since the problem goes away after a few minutes I guess the issue is a broken component, like a capacitor or resistor.

I have no electronics background, just a few soldering skills. I want to learn how to repair stuff the DIY way. A few weeks ago I repaired an audio amplifier. The problem was simple, a burned track on the PCB.

What are the steps required to pinpoint the problem? My toolset is limited, I have no oscilloscope, and no capacitance and inductance meter, just a couple of cheap multimeters.


texts:
We are using to the BC856ALT1G on our products
Below is datasheet of ON Semiconductor.

I'd like to know that How much the hFE value decrease at -40C (low temperature)
or How to calculate the hFE value at low temperature.
If possible, Could you send me the related reference materials.

Thanks,


texts: Which is more efficient: every loop or afterwards?

texts:
Planning to collect some sensor data with an Arduino (or ESP32) and looking through other people's code I noticed two variants, generally, to process sensor data.

Collect, average and subtract some initial calibration value within the loop.
Collect all data, then process after the loop.

Some data qualities (in my example):

data sampled at 100Hz
2-3 channels (imagine gyroscope sensor, natural signal frequency.... maybe 1-10Hz for anything useful?)
some baseline calibration window before is subtracted, e.g. 100 datapoints / 1s

Pseudocode:
//variant 1) process within loop
loop() {
  read_data=readsensor();
  read_data=smooth(read_data);
  read_data=subtract(read_data,baseline);
  data_store[cnt]=read_data;
  cnt++;
}

//variant 2) after
loop() {
  read_data=readsensor();
  data_store[cnt]=read_data;
  cnt++;
}
process() { //called after loop 'finishes'
  data_store=smooth(data_store)
  data_store=subtract(data_store, baseline)
}

I understand that 1 will impact processing time during acquisition and 2 afterwards. I'm interested in coming up with the fastest way (i.e. time after recording) to the best version of the data (i.e. smoothed, subtracted, etc). Concrete questions:
Questions:

Is there some sort of optimization implemented in Arduino, that would make 2 faster than 1 - or can this fundamentally be implemented faster than 1? (this is my hunch)
is there some fundamental engineering principles that would suggest 1 rather than 2 (based on sampling theorem etc)?
Are there some general rules of thumb on the Arduino (-compatible) platform?

Any other advice is very welcome!


texts: Supercapacitor Emergency Power Supply UPS

texts:
I'm considering hiring an electrical engineer to design an emergency power supply for use in embedded devices. This power supply only needs to hold ~15 seconds of charge (enough time to safely shut down the devices). I would like to support 12V and up to 2A. Juice4Hault produces a Supercapacitor UPS, but thier prices are very high. Batteries aren't reliable since they degrade and corrode over time.

I found some cheap parts that I hope will keep production costs low:

2.7V 100F Supercapacitors ($1.50 each)

LM2623 ($0.50 each)

Basically I would like to use low voltage supercaps and a voltage booster to convert extra amps into higher voltage output. Where I'm lost is interpreting the LM2623 datasheet. Could it reliably boost these Supercaps into 12V 2A 15-second output?

UPDATE:
I'm considering using two capacitors in series. Then I'd have 5.4V 50F at my disposal. The Samwha Green-Caps that I am considering can pull 5A continuous current. So 5A ∙ 3V(Min) ∙ 80% efficiency = 12V ∙ 1A, sustainable for 10 seconds, which I could live with. I would have to use a more expensive booster:

TPS55332-Q1 ($2.50 each)

Is there an IC that can safely support this?


texts: High capacitance oscillator circuit to produce longitudinal waves

texts:
I’m trying to figure out a suitable oscillator circuit to produce longitudinal electric field waves (like in a Tesla Coil) to experiment and produce any mechanical or EM effects on various materials.  A conductive sphere will be driven with AC. So the sphere will be pulsing  with –q , +q , -q , ... with an isometric pure electrodynamic field with all magnetic  field cancelled out.

A 50 Mhz fixed frequency oscillator circuit with weak or no harmonic distortion to oscillate relatively high amount of charges  back and forth to a high capacitance sphere antenna (sphere, because i know the self-capacitance equation of a sphere only). I think a crystal/Pierce oscillator would fit best for a fixed high frequency without harmonic distortions.
The problem is, I would need to oscillate  high amount of charges (about 10^-5 – 10^-4 Coulombs) to produce a decent, mechanical or EM effect.

To drive such high amplitude of oscillations with peak voltages low enough to be safely measured even with a 10x oscilloscope probe, I would need a high capacitance oscillator circuit and I think that even if I connected many crystals in parallel, I would need thousands of them.

Could I use a thick crystal with low fundamental frequency and produce only a higher harmonic (50MHz) by a band-pass circuit? But then again, why would I need a crystal when I used a resonant LC circuit with high capacitance?

Also I would need to be able adjust the amplitude of the oscillations (amount of oscillating charges) which makes things even more complicated. Should I vary the collector voltage of the transistor or the resistance?

Any suggestions are welcome.


texts:
I am doing a research about the electricity grid and a marketplace where neighbours can trade energy with each other.

I found out if your PV cell has excess energy you can with an inverter put it into the grid in 1 phase, or 3 phase if it's too much (>5kw). The question I am asked when I do presentations is: Does this work? And who does the frequency or voltage regulation?

Is it a real world problem or inverters are so good that they don't break the grid?

I also know if the grid goes out of specification the inverters are able to shut themselves down, so I got that going for me.

My professor questions if it is possible that neighbour A puts energy into the grid and then neighbour B takes it. Of course it won't be the same "energy" but the net difference on the grid will be 0 thus a "virtual" transaction. If grid operator agrees with this they might only have to pay a small transaction fee.


texts: Current sense trace vias underneath shunt resistor

texts:
I need to connect current sense traces from a shunt resistor to my PMIC on the other side of the board. Due to space constraints, I'd like the traces to pass through vias directly underneath the shunt resistor (option 1 below), rather than first exiting the side of the shunt resistor before going through the vias (option 2 below).

Are there any issues with doing so? I would normally length match the traces on both sides of the board (per option 2 below), but can't do so with option 1. Will trace matching on only one side of the board be sufficient?

Option 1: Trace vias directly underneath shunt resistor

Option 2: Trace vias exiting shunt resistor before going through vias


texts: Modified Gummel-Poon BJT Modelling Issue

texts:
First of all, sorry for my bad english.

Output for Vb:

From the schematic above, I redrew the 2N3904 BJT into the modified Gummel-Poon model.

Output for Vb:

The equation for B1, B2 and B3 were determined using the info below.

Then, the values of the intrinsic capacitance were determined using the DC operating point analysis in LTSpice.

Cbc = C2

Cbe = C3

But the result seems wrong for me. What do I miss? Can I just take and use the values of Cbc and Cbe from the DC operating analysis log file of LTspice?


texts: Inverze z transform - contour integration

texts:
Here is my task:
Find inverse z transform of

$$X(z)=\frac{1}{2-3z}$$
if \$  |z|>\frac{2}{3} \$ using definition formula.

I found that $$x(n)  = \frac{1}{3}(\frac{2}{3})^{n-1}u(n-1)$$ (using other method).

But how can I find it using definition formula, \$x(n)=\frac{1}{2\pi j}\oint_{C}^{ } X(z)z^{n-1}dz\$ ?


texts:
I have an LCD (the DOG-M 102x64, with a uc1701 controller) that I am driving (over SPI, but that's somewhat irrelevant) from an AVR (ATMega16 @ 8 MHz) - all in all, a fairly low spec'd screen with a low-spec'd system. The screen at hand is only capable of 1-bit display, but I would like to emulate some shades of grey with it (per-pixel).

Reading through the controller datasheet offers some ideas: there exists commands that will turn on all pixels, and another that will invert the display (not affecting the display ram).

I've searched around, and the information I came up with was in a question posted here, commenting mainly on biasing of the liquid crystal over time.
I'm also aware of Binary Code Modulation, perhaps that could be applied to this problem?

Is this technique a viable method for emulating greyscale? Has anyone done it before?

Edit: Found this resource which illustrates that the concept might be somewhat viable.

Edit: Found this resource that makes me think rapidly switching between two framebuffers (2 bit planes) might not only be a viable approach in general, but might also have some long-term negative effects on the LCD if done incorrectly.


texts: What does 'not controllable' mean in power electronics?

texts: A book says that the power diode is 'not controllable' whereas a 'Thyristor' is semi-controlled and a 'MOSFET' is fully controlled. What do these degrees of controllability mean? Is it somehow related to feedback loops?


texts: Any problems with double step-down conversion?

texts: I would like to use this PMIC but the problem is the default values for the DC/DC and LDO converters are different than what I want to use. Unfortunately the custom OTP setting to get the values we want is too expansive. I was thinking to covert the values with a step down converter like this. Are there any problems with doing dual conversion, one happening in the PMIC and then again externally.