texts:
I'm trying to determine which battery to use for my application. I'll be using a class 1 or class 2 Bluetooth (not low energy) module, which requires about ~50/60mA of RX/TX current. In addition, there is a microcontroller and some low power analog IC's. I require a continuous stream of data from the device for 1-10 minutes.

Are coin cells completely out of the question? I'm talking about CR2450 Lithium-ions. I don't really mind if they don't last long, but will they work? Because in my application, size is key, and battery life is a trade off that I'm willing to make.


texts: How can I 'bridge' and unbridge connections between two inputs

texts:
How can I make a non physical switch so that when in one state the two wires will be connected and in another they are not.
IE: Current going through into I/O 22 and being connected or not connected to a wire leading from I/O 23.
I am using a ardunio mega, and the code compiler is Ardunio as-well.

It is kinda like a no moving parts button, if you will.


texts: What does the open circle in the circuit depict?

texts:
The open circle at pin 4 in 555 and pin 13 in 4017 has got me confused. I'm new to electronics and any help will be appreciated.
Also does the pin 5 in 555 need to be connected to pin 12 in 4017?
Thanks.


texts:
I need to isolate the dc input from the dc current inside the circuit (both 9v), in the same way as a 1:1 transformer isolates the AC current inside the circuit from the input AC. I already found out that there are also 1:1 DC-DC converters, but do those converters also really isolate the input from the output? And is this also the best (or only) solution for this? I need this to prevent ground-loops.

Thanks!

edit: Thanks for your comments so far, I've corrected some things in my original question, and below I'll try to explain my problem as well as possible below:

I'm building an effects pedal for my guitar. Effects are usually placed in 2 different locations in the signal chain (before the amp, and between the pre and power amp(effects loop)). If you use the same power supply for pedals in front of the amp and in the effects loop, you can create ground-loops (effect1->audiocable->pre-amp->audiocable->effect2->powercord->effect1), so usually you use 2 different power supplies for this. However, for some reason I need an effect which has parts of it in front of the pre amp, and parts of it between the pre and the power amp*. As a result, I need to find a solution to break the ground-loop inside the effects pedal.

*In theory I could use multiple pedals for this, but then I need to do some crazy tap-dancing on stage to switch multiple pedals at the same time. So this is not a possible solution.

edit2: I forgot to mention, but the only thing still physically connecting both parts of the effect inside the pedal is the power supply. Of course I could use 2 power supplies for one effects pedal, and that would solve my problem, but I think that's an ugly solution.


texts: Using a MOSFET to switch a High Voltage on a Capacitive Load

texts:
I am trying to bias the filament of an electron gun to -575 V, but I need to switch it on and off using a TTL signal. I have an idea for how to do it, but I would like to know if it will work before I start messing with HV power supplies. My question is will this circuit switch the voltage? If not, how can I improve it or what would work better? (EDITED to fix MOSFET orientation.)

simulate this circuit – Schematic created using CircuitLab

The data sheet for the MOSFET may be found here: http://ixapps.ixys.com/Datasheet/DS99988B%28IXTH-T16P60P%29.pdf


texts: Help with explanation on this transistor behaviour

texts:
Hi,
I found the above circuit on a website where it was said to produce fade in effect for the LED's. I tested the circuit out in my breadboard with R2 as 1K and C1 as 1000uF and R3 as 100 ohms.

The circuit indeed works. In that website it was explained as when the power is ON capacitor will start charging through R1 and once it reaches the base bias voltage of 0.7V. It activates the base of transistor Q1.

1) But I couldn't figure why LED's are fading in rather than lighting up in an instant. Because as far as I know when the base bias voltage is reached transistor switches ON instantly allowing the flow of current from collector to emitter, How LED's are fading in ?

2) Which state transistor is acting in this circuit? For saturation base voltage should be greater than collector and emitter but neither of this is true in the above circuit but still current flow exists between collector and emitter?


texts:
I've been reading up on small signal analysis to try and better understand audio amplifier circuit design (end goal a discrete BJT guitar amplifier). I'm attempting to apply the knowledge I've picked up (from Microelectronic circuits - Sedra/Smith) to the following amplifier schematic:

Would anyone be able to offer some guidance on whether or not I'm doing the correct analysis?
Assumptions:
$$\beta = 100$$
$$V_{A} = 100$$
$$V_{be} = 0.7$$
So:
$$(1) = 7mA$$
$$(2) \approx 4.6mA$$
Signal Input Impedance (R IN1):
$$r_{\pi} = \frac{\beta \cdot V_{T}}{I_{C}}$$
$$r_{\pi} = \frac{100 \cdot 25mV}{2.3mA} \approx 1087 \Omega$$
$$R_{IN1} = R9 || r_{\pi}$$
$$R_{IN1} = 100k \Omega || 1087 \Omega$$
$$R_{IN1} \approx 1075 \Omega$$
Diff Pair Signal Output Impedance (R OUT1):
$$r_{o} = \frac{V_{A}}{I_{C}}$$
$$r_{o} = \frac{100V}{2.6mA}$$
$$r_{o} \approx 38462 \Omega$$
$$R_{OUT1} = r_{o}$$
Gain (Avo):
$$A_{vo} = -g_{m} \cdot r_{o}$$
$$A_{vo} = - \frac{I_{C}}{V_{T}} \cdot \frac{V_{A}}{I_{C}} = \frac{V_{A}}{V_{T}}$$
$$A_{vo} = -\frac{100V}{25mA}$$
$$A_{vo} = 4,000 V/V$$
Many Thanks in advance


texts: Generating a Low frequency triangle wave

texts:
I want to replicate the circuit seen in this video: https://www.youtube.com/watch?v=MHTiSRCKNF4&t=341s without using the function generator he uses.

The video explains that by inputting a signal and a triangle/sawtooth wave into a comparator, you can turn it into a PWM signal.

My question is what is a good way to generate a low frequency (around 1 Hz) triangle wave for this purpose without a microcontroller? It would also be nice to be able to adjust the triangle wave's max and min.


texts: Programming (flashing) MachXO2 chips through JTAG

texts:
I'm trying the MachXO2 7000HE Breakout Board --- I could make a simple demo work (following this nice Youtube video).
Since I want to include one of these chips in my next design, I want to learn first how to flash them.  Looking at the TinyFPGA schematics as well as this Breakout board schematics, it would seem like I only need to connect the pins TMS, TCK, TDI, TDO, 3.3V, and GND?
I have a TinyFPGA and its TinyFPGA programmer, and I had hoped that it would work with the 7000HE Breakout board. I know, its description says "JTAG programmer for the TinyFPGA boards" — but then, these TinyFPGA boards (as well as the Breakout board) seem to have nothing other than a MachXO2 chip with the JTAG lines connected.
In the Breakout board, I removed the 0-ohm resistors R5, R6, R7, R8 — it doesn't work.  The TinyFPGA Programmer software tells me Cannot identify FPGA. Please ensure proper FPGA power and JTAG connection when I click on the Program FPGA button.  I triple-checked the connections.
Is it just that the TinyFPGA programmer only recognizes the specific MachXO2 chips used in the TinyFPGAs?
Should it work with the Lattice Semiconductors programming cables?  (e.g., the HW-USBN-2B?).
My bottom-line question is: when I place the MachXO2 chip on my board, do I just need to expose the four JTAG pins + GND + VDD, and I should be able to program the chip with the HW-USBN-2B?


texts: Using avr-gcc _delay_ms causes chip to freeze

texts:
I have a ATmega328-PU chip which is setup to use the internal oscillator without dividing clock speed by 8. The first thing I did was to use a really simple program I uploaded; a program which turned on and off all pins on PORTB. Like so:

#define F_CPU 8000000UL
#include <avr/io.h>
#include <avr/delay.h>

int main(void) {
    DDRB = 0xFF;
        PORTB = 0xFF;

    while(1) {
            PORTB = 0x00;
            _delay_ms(50);
            PORTB = 0xFF;
            _delay_ms(50);
    }

    return 0;
}

Update: I have tried what Jon L suggested. Still the same result.
Update 2: I have tried what Kevin Vermeer suggested. The chip seems to freeze when it enter the first loop. Using the timer with a value < 65000 makes the LED turn on directly, using a value > 65000 results in the LED never turn on.
Update 3: I have tried following with a new identical chip with the same results
Update 4: I plugged in simulavr and avr-gdb to see whether I found something, this was the output:

memory.c:267: WARNING: * * Attempt to write invalid io reg: ADCL at 0x0024
memory.c:267: WARNING: * * Attempt to write invalid io reg: ADCH at 0x0025
memory.c:267: WARNING: * * Attempt to write invalid io reg: ADCH at 0x0025
decoder.h:59: WARNING: Unknown opcode: 0xffff

Then unknown opcode loops forever.

However, when I have uploaded the program it reaches the second instruction in main and then freezes. Leaving all PORTB pins in HIGH. So far I have tried:

Different ms between 10 - 1000 to see whether there are some values that can't be used
Changed F_CPU to 1000000UL in case it would use CKDIV8.
Looping _delay_ms(1) in a separate function until it iterates to the given amount
Re-compiled and re-uploaded multiple times
Tried resetting multiple times
Used different PORTB pins
Defined F_CPU from the compiler arguments -DF_CPU=8000000

Why I'm asking here and not stackoverflow.com is because I think I should start to eliminate errors on the lowest level of abstraction, that is; hardware.

So what could be the problem?

Here are some information about my setup:

Operating system: OS X 10.7.3
Programmer: AVRisp MKII
Uploader: avrdude
Compiler: avr-gcc
Bin 2 hex: avr-objcopy

Fuse settings:

avrdude: safemode: lfuse reads as E2
avrdude: safemode: hfuse reads as D9
avrdude: safemode: efuse reads as 7

Input into AVR fuse calculator:

makefile:

main:
        avr-gcc -g -Os -Wall -mmcu=atmega328 -c ../src/example.c

hex:
        avr-objcopy -j .text -j .data -O ihex example.o example.hex

dump:
        avr-objdump -h -S example.o > example.lst

upload:
        avrdude -p m328 -c avrispmkII -P usb -U flash:w:example.hex

clean:
        rm -f *.o
        rm -f *.hex
        rm -f *.lst

Pins used on chip:

Pin 7 (VCC): 5 volts supply
Pin 8 (GND): ground
Pin 14 (PB0): resistor and LED


texts:
Is it possible to passively listen on low speed USB communication?

Suppose I connect a logic analyzer to D+ or D- line, will I see a valid data?


texts: Mean Well power source doesn't start on battery

texts:
I power an amplifier using ADD-55 power source with "built in UPS functionality".
As supposed, it charges a battery connected to "battery" output, and continues to run on it when mains power fails.
What I don't understand is why power source doesn't start on that battery. I.e. I have a spare charged battery "in the field", no mains power, and I want to switch on the amplifier.
Unexpectedly, the only way to start without mains power is to connect a battery to +V output of power source (not "battery" output).
What is proper way to arrange such a cold start?
Addition: power source is ADD-55A, load is custom built RF amplifier, battery is lead-acid 12V 3A*h, circuit is trivial:


texts: what are the differences between i/o expander, demultiplexer, decoder & bit register?

texts:
Newbie here, our professor had given us a big problem (i mean homework) on how to interface multiple SPIs using 1 microcontroller. But his requirements are quite exaggerated:

1 microcontroller interfaced on 90 spi devices (like what?!) and it should be simplified like use only 3-8 gpio pins to access all of those.

He said submit it on a paper considering 1 microcontroller has 2 SPI buses. Well, i did take the challenge since this will be done in a demultiplexing way (right? since ss pins of SPI devices just needed some active LOW/HIGH signal even it is not directly coming from the microcontroller like let's say signal from a voltage supply/regulator output to wake it up).

Now canvasing to choose multiplexers, 3 to 8, 4 to 16 bit, 5 to 32 (cascaded) i find myself seeing this 10-bit I/O expander ICs where upon reading and looking how it will be used, it's like a bit shifter using SPI only. I plan to use these 10 I/O ports as 10 cs for the 10 SPI device's ss. I thought of this will be good. Then seeing decoder, etc.. i find using multiple 10-bit I/O expander to connect to this 90 spi devices because i think making a combinations/cascadings, etc w/ these 4 different ICs, i guess its good to stick using multiple 1 IC only maybe to reduce cost and complexity.

Do i understand it right, specially these 4 different ICs? what exactly their difference and application? Am i facing a problem if i do this kind of approach??


texts: Are standard USB connectors (Standard / Mini / Micro) Impedance controlled?

texts:
Are standard USB connectors Impedance controlled? Do they follow differential characteristic impedance of 90 Ohm for DM & DP lines?

Does standard Type A, Mini / Micro - USB Type follow same impedance match from PCB? Or Characteristic impedance changes at connector pins?

If they follow, how they manage to do so? As there is no ground / reference plane on USB connector to get this impedance.


texts: How is a capacitor in series with a resistor and capacitor in parallel calculated?

texts:
How do you calculate this circuit?

I would like to calculate both the voltage, current and charge progression of those three components seen as one part as well as their individual voltages, currents and charges.

The values given in the circuit diagram are just placeholders but for completeness let us assume the total voltage 10VDC.

I would like to understand the mathematics behind such a calculation and not only know the solution to this specific example.

Thank you in advance

Edit: I want to analyse the circuit assuming the capacitors are initially uncharged. It was pointed out to me that that is a transient analysis.


texts: Does this neon indicator light require a resistor to limit current?

texts: I've got a few of these indicator lights from LEECRAFT/VCC, they're marked "tineon 3600" and "125V 1/3W". According to this page: http://wiki.diyfaq.org.uk/index.php/Neon neon lamps require a resistor to limit current, but many indicators have them built in. I believe this is the datasheet for the indicators I have: https://vcclite.com/wp-content/uploads/wpallimport/files/files/36and36LSeries.pdf, specifically 36EN-2313, but it doesn't discuss any integrated resistor. Anyone have experience with these and can tell definitively if a resistor in still need or can be used off mains power(117V) as is?


texts:
As per my understanding, When an electric field is applied to a current carrying wire, it exerts Lorentz force on electrons and hence a transverse electric field is generated. Also when we apply magnetic field wire resistance changes called as magnetoresistive effect.
  My Question is aren't both of these effects are same? Or am i making some mistake. Also i found somewhere that magnetoresistive effect is of 2nd order while Hall effect is 1st order.How is this possible if both have same cause.
(Sorry for my poor english)


texts: Proper term for electronic-ize(ing) an algorithm

texts:
Let us consider a certain computer program that converts sine values to cosine values:

#!/usr/local/bin/python

import math

for _ in range(0, 90, 0.1):
    x = math.sin(_)
    print(  math.cos( math.asin(x) )  )

Now, I want to do it on-chip/in-hardware so I make something like:

So what is this process of implementing a math algorithm on circuit is called?

Actually, I read Apple's blog

  To achieve long battery life when playing video, mobile devices must decode the video in hardware; decoding it in software uses too much power. Sir Steve Jobs

and that got me inspired to implement some of my algrothims in-circuit. So what is this process called? here's another example

What do I search for in library- hardwiring, circuitification or what exactly?


texts: Is group delay the same as the delay of a certain frequency?

texts:
I know that group delay is the delay of the envelope, or the derivative of the phase with respect to \$\omega\$. What I want to know is what exactly happens in the time domain.
For instance take the following graph of the group delay of a bessel filter (there are several curves depending on the order of the filter)

Consider the curve at the very top which is near the 0.6s mark, does it mean that if I inject a normalized 1.1Hz frequency into the filter, will that signal be time delayed almost 0.6s at the output? meaning that the difference in time between the output and the input at that frequency is 0.6s?
A thing that also makes me believe that the group delay means time delay is the step response. Here's the step response of the same Bessel Filter

It seems like there is a delay from the 0 second point.


texts:
For the following circuit I am trying to calculate the DC drain current \$I_{DQ}\$

I know firstly that while doing a DC analysis the capacitors act as open circuits. This means that there will be zero current flowing into the gate.

Doing KVL around the gate / source loop:

\$-3 + 1200I_D + V_{SG} =0 \$

\$ \implies V_{SG} = 3 -1200I_D\$

This is also a P type MOSFET so the drain current is given by the expression:

\$I_{DQ} = k_p(V_{SG}+V_{TP})^2\$

and substituting \$V_{SG}\$ into the equation above gives

\$I_{DQ} = k_p(3 - 1200I_{DQ}+V_{TP})^2\$

Given \$K_p = 800\mu \frac{A}{V^2}\$ and \$V_{TP}=-0.4V\$, I solve for \$ I_{DQ}=4.03mA\$

However the answer is given as \$1.16mA\$.

I know that this is quite basic but I feel that the error is a fundamental error rather than a calculation one. Could someone please explain to me which of my assumptions were not correct?


texts:
A system is designed as a cascade of of 4 subsystems, each contributing the same amount of time to the average service time of the system.  If we wish to increase the speed of the system by a factor of 2 by reducing the service time of each subsystem equally, how much speedup should be applied to each subsystem?

This is how I solved the problem and I was hoping someone could let me know if I am on the right track:

Amdahl's Law is Speed Up[overall] = 1 / (Fe/Se + (1 - Fe)) where Fe is enhanced fraction and Se is enhanced speedup.  In this case Speed Up overall = 2 and enhanced speed up = 4 because there are 4 subsystems.  All I did was solve for Fe and I got .66, which is 66.66%. This means each subsystem must increase it's speed by 66.66%.

Is this correct? Am I on the right track at all?

The next question asks a similar question except the average times of the first two subsystems are to be reduced by twice as much as those of the last two subsystems, but the overall speed up should remain at 2.  I'm a little confused how to use Amdahl's Law here.

Would appreciate all / any advice or any literature that might help.


texts: What connector is this? (Inside a wifi modem)

texts:
I was about to attach an antenna to my 4g modem and thus trying to identify which connector is there on my modem board and i found this connector (4 of them, 2 for 4g and 2 for wifi).

I tried connecting u.fl female pigtail to it and it does not work. I suspect it is a female ipex, but i know you guys know better. Pls tell me.
Pls make use of the miniSIM card nearby for size reference, thank you.


texts:
I am building the following circuit, in order to control the P channel MOSFET as a high side switch for my load.

The input of this circuit will be from a microcontroller (maybe an STM32F103), and I was planning to use the output pin, in open collector mode.

Will this work? Please note that I am pulling up the pin at 12V.

I know that in other circumstances it would work, but in a microcontroller, will the output handle the 12V? When in open collector, are the ESD diodes disconnected?

And if it works, how do you handle the initialization of the pin, (after reset, before configured as an open collector pin).


texts: Instrumentation amplifier dealing with wire resistances

texts:
Can anyone please help me in understanding the output of this amplifier? According to me it is coming as
(E1-E2)(1+(Rw/R)).

I am more curious about knowing wheather Rw will come in the output equation or not, and if not how will it get eliminated.


texts: What is the main source of variation between thermocouples of the same type

texts:
Thermocouples have stated tolerances [wikipedia]. However, the characteristic behaviour is defined by the materials in contact, so there aren't size or shape considerations as for RTDs. What are the main sources of the variation/tolerances in thermocouples?

A comment to this answer blames variation in metallurgical properties, which seems plausible, but this is unsourced.


texts: Use of superposition principle for the inverting amplifier

texts:
My current understanding of the inverting amplifier goes as far as assuming the second golden rule: no current flows through the OpAmp.

From here on, up to the end result of \$ H(\omega) = -\frac{R_2}{R_1} \$, I'm having a hard time understanding what's going on.

My first confusion arises when applying the superposition rule to obtain the reference voltage \$ U_{-} \$ at the inverted terminal (the non-inverted on being grounded).

I want to understand this crucial step so I find an expression for the gain voltage \$ G\ U_{-} \$ to which the OpAmp sets its output.

I stumble upon the same problem in calculating the reference voltage at the junction point at \$ V_{out} \$.

I'm not sure of the approach of converting this circuit into a Thevenin equivalent circuit, by treating the OpAmp as a current source, either.

For the problem at hand, I don't assume the first golden rule where \$ G(U_{+} - U_{-}) = 0 \$. This is what I actually want to derive. :)


texts:
Recently I've started playing a lot with 3D printers, Adrunio, Pandaboards and Kinect's SDK. I'm starting to have more and more passion for this sort of devices and I think it's about to turn into a pretty absorbing hobby.

Now - I'm a software engineer (mostly C/C++ and low-level background) with a couple years of experience. I know a thing or two about how computer hardware work, but the last time I was exposed to lower-lever / more primitive electronic components was in college in my Circuits classes.

I know how important it is in programming/mathematics to be aware of a couple of important concepts that are not very obvious for newcomers and without a good guide (Mentor, book, etc.) its fairly difficult to even come across them (for example concepts introduced by Alexander Stepanov's - Elements of Programming) but also I do not want to go too much into details; I already have a profession that I enjoy a lot.

So here is my question: Could you please recommend a book or any online materials (tutorials, video, etc..) that would introduce me to surface-level understanding of electronics needed to build hobby projects that involve micro-controllers, possibly some sensors, some mechanic parts that I can try out different algorithms on?

Ideally I would like to get to the level of understanding where I will know where to look next if I want to build say a small device that automatically waters my front-yard basing on the weather conditions or turn the heat on.


texts: Any drawbacks to "low temp" lead-free solder paste?

texts:
I am about to try my first "reflow skillet" soldering job, and as I look at the available types of solder paste I see there are lead-free pastes with much lower melting temperatures than others.

For example, this one from ChipQuik.

The advantages seem obvious, but somehow the marketing literature does not mention any drawbacks to this type of solder paste. In the quantities I would order the price seems about the same. Is there a reason this Sn42Bi58 formula hasn't become standard?


texts: MCP6001 op-amp unable to drive LED when configured as inverting buffer?

texts:
I built this circuit on breadboard and came across a problem:
I'm using the MCP6001 op-amp with a single supply, configured as an inverting buffer. That's why I connected the non-inverting input to a virtual ground made between R3 and R4. The pot R5 is used to change the input voltage. The LED should get brighter as the input voltage goes down.
It does work in principle, but the LED is less bright than when I connect it to 5V directly. When measuring the voltage at out, it is 0V when the input from R5 is high (5V). But when it's low (0V), the voltage at out will be something like 3.2V. When I disconnect the LED, removing the load from the op-amp output, all is fine and an input of 0V will result in a 5V output.
Does this mean the MCP6001 is unable to properly drive a single LED? I read the datasheet but wasn't able to make sense in such a way that I could determine the maximum output current in my configuration.

simulate this circuit – Schematic created using CircuitLab


texts:
Looking at this page it mentions that double precision digital pulse input (32-bit timer) can be divided into 2 single precision 16-bit timers.

https://github.com/ytai/ioio/wiki/Pulse-Input

It says there are 3 single and 3 double modules.

Does this mean that 9 pins can be used for single precision pulse input? (3 single + 3*2)?

Is this correct?


texts: about power supply on what length of copper wire we should use

texts:
Could you help me on the equivalent current of three phase alternating current having 400v( volt ), 530 kw power and the available cross-sectional area of a copper wire, its length 350 m for carring this curret

Added:

Presumably the question is: What conductor diameter do I need to carry power for a  400V, 530 kW 3 phase systema distance of 350 metres.


texts:
i have read quite a lot about this and i would like the experts opinion. I have an old dell desktop with a 250 watt PSU - PSU is grounded to the metal casing of the psu and the psu in turn touches the metal part of the PC case. I brought the PC from UK to Vietnam to be donated to a home. I noticed that since i am in Vietnam, the case is live / if i touch it, i get a tickle and if i apply a test pen, the test pen lights up. I also noticed that most wall outlets are not earth at all (most sockets only have the live and neutral.
1. Is it safe for me to use the PC (even though users touching it will get a tickle.
2. Do you that the capacitors are faulty (the ones leaking current to the body? (They are blue
Thank you
Michael


texts:
If there's a number, say '1101,' how am I supposed to read it?

Should I consider it an unsigned number and read it as '13' or consider it a signed number and read it '-5' or consider it a 2's complement number and read it as  '-3?'


texts: Newbie: ATmega32u2 USB-powered - how to ground?

texts:
In ATmega32u2's reference manual, there's a diagram for USB-powered application like shown below.

Should I, or should I not, connect the GROUND to VSS/UVSS line? And why? If not, then what to do, just connect GROUNDs together?


texts:
I need to learn and practice VHDL, so I wouldlike to buy a small FPGA dev board. I've found a board based on a MAX10 circuit with the exact form factor I need, but I've read this chip is a CPLD, not a FPGA.

I'm not sure to properly understand what CPLD are. Can I practice VHDL with efficiency on this kind of board, or should I invest more in a Cyclone chip, whose are "real" FPGAs ?


texts:
I'm working with a dsPIC that measures the output of a variable 20V power supply. I'm experiencing errors on the ADC measurements and they are not constant errors, they vary according to the output voltage. I measured the output voltage of the power supply and the voltage at the ADC input of the microcontroller with a  UNI-T IT61E multimeter:

Where Output Voltage is the measured voltage at the output of the power supply, the Voltage in ADC is the voltage measured in the ADC pin relative to the AVSS pin and the Division Factor is calculated as Voltage in ADC/Output Voltage. As you can see, this factor is not constant, so my multimeter is not that accurate (I think it should be precise and accurate enough) or the ADC input stage is not that linear. Here's the input stage:

Is it due to the OPAMP or the low pass filters? Or is it really my multimeter giving wrong readings?


texts:
This is follow-up question to this.

For the inferences made below(may be wrong),
let $$h[n]=impulse\hspace{1.5mm} response\hspace{1.5mm} of\hspace{1.5mm} the\hspace{1.5mm} LTI\hspace{1.5mm} system$$

$$x[n]=input\hspace{1.5mm} signal\hspace{1.5mm} to\hspace{1.5mm} the\hspace{1.5mm} LTI\hspace{1.5mm} system$$

Can we infer the following?

A system will behave as causal if:

1.The system impulse response response is causal i.e$$ h[n]=0 \hspace{1.5mm}for\hspace{1.5mm} n<0$$

OR

2.Input signal is a right sided signal$$i.e.\hspace{2mm} x[n]=0 \hspace{1.5mm}for\hspace{1.5mm} n<0$$ to the LTI system irrespective of whether the system is actually causal or not.
Here,although the system is physically the same(i.e. has an impulse response of h[n]) but it ACTS as a system with impulse response x[n] and signal h[n].

Inference 2 is due to commutative property of convolution.


texts: How can I distinguish between LTE and WiFi antennas?

texts:
I've a LTE router with WiFi, it switches automatically between LTE bands 3, 5 and 40, depending on the respective signal quality.

I want to improve the band 40 reception. So I think the easiest option is to remove the band 3 and 5 antennas. As the propitiatory firmware provides no interface to switch or lock a specific band.

The main problem is identifying the correct antennas to remove. The device has 4 patch antennas, printed on yellow mylar films. All of them looks similar to me!

So how can I identify the band 3/5 antennas ?

The WiFi chip is RTL8192EU, which is capable of 2T2R MIMO, so is it possible there's 2 antenna for WiFi? I can provide internal pictures if needed.

Device is made by Pegasus Telecom, subsidiary of Haier.

Pictures, main board.

Antenna on top

Antanna on left and right, seems like inverted F monopole.

Antenna on bottom


texts:
Quick question,

I know about CanBus protocol. I'm interesting about ISOBUS and CanOpen.
I know that those are exentsion of the CanBus protocol. So my question is:

Do ISOBUS and CanOpen need different hardware?
Do ISOBUS and CanOpen can operate on an existing CanBus network?
Do the changes for those protocol is on the software layer or is it on the chip/hardware layer?

Thanks!


texts: Can I use the external trigger to simultaneous capture waveforms on two oscilloscopes?

texts:
I want to look at synchronization in a 6 oscillator network (oscillators are about 100 kHz, 1.5 V_pp, if this matters). I have a 4 channel oscilloscope (Tektronix TDS 2024B) and a 2 channel oscilloscope (Tektronix TDS 1001B). Can I use a signal generator as an input to the External Trigger of both oscilloscopes so that I can perform a screen capture at the same time on both scopes? I was imagining that I could input a triangle wave and capture at the peak, or something like this.

I am just learning electronics (chemical engineer/applied mathematics background), so if the answer is yes, please keep in mind that my curiosity is great but my knowledge is shallow.


texts: How to highlight all instances of a net in Eagle? (multi-sheet schematic)

texts:
I'm adding some components to an existing design in Eagle.  It's currently a 4 sheet schematic.  I want be 100% sure that the net I've labelled on one sheet is connected to the desired net on another sheet.  For example, that the net named MOTOR_C_D2 on a FET on one sheet is in fact connected to a GPIO line labelled MOTOR_C_D2 on my AVR CPU (they are on separate sheets).

I did a Tools->Search for MOTOR_C_D2 and it only highlighted the pin on my CPU.  It did not highlight the pin I have on the FET also labelled the same.  I would expect that a search would highlight ALL components on all sheets of a schematic that met the search string, but perhaps Eagle doesn't work that way?

Thanks if anyone can help.


texts: Multimeter giving seemingly inconsistent voltage readings

texts:
I am trying to use a digital multimeter to measure a house solar panel installation. I'm just learning, but I can't find a good answer to my problem.
I tested the voltage on a 1.5 AA battery and as I moved the knob to higher voltages (from 200 mV to 1000 V) I get very divergent readings:

200 mV : 1 (overloaded)
2000 mV : 1580
20 V : 2.56
200 V : 12.4
1000 V : 111

I don't know if I'm wrong, but I was thinking that as I increase the max voltage I'd get smaller values, but this jumps from 1580 to 2 then 12 and then 111, the pattern doesn't seem to grow evenly in the last 3 values either.
My original goal was to measure voltage in what was to be a 12 V installation, I got these readings:

20 V : Overloaded
200 V : 105+
1000 V : 935+

I take it has more than 20 V, but the other readings don't make sense so I don't know how to interpret them.
Am I missing something, is there something I don't know?


texts: Requesting wiring feedback - Arduino/ESP32 solenoid/transducer, temp probe

texts:
2 questions:

Can you please tell me if this circuit wiring is correct for the 3 sensors I am trying to connect to my ESP32?
Is there a risk for EMI using the ethernet cable with these sensors/voltages?

Sensors to be connected:

Solenoid
Pressure transducer
-1-wire temperature probe

NOTE: Wires from left side are supplying 12v (red) and going out to GND.


texts: Transformer specifications to get 18V AC output from 230V AC in Proteus simulation

texts: Can anyone help with the transformer specifications below, so that I can get 18V AC output from 230V AC input in Proteus simulation?


texts: Want to build an ethernet-connected USB or battery powered piezo alarm gizmo -- what's a good kit?

texts:
The device is supposed to beep loudly if the network is down, a particular port on an Internet host doesn't respond or a socket connection is made on a specific local port.
Is an Arduino Ethernet shield enough? I am guessing i will also need an Arduino board and software? Are there non-Arduino solutions that are cheaper or easier to code for? This will never leave the working prototype stage.

I am a total newbie when it comes to electronics, so I am looking for a kit that covers all the hardware/software needs, excluding the speaker itself.

thanks in advance


texts: what potential difference actually do indicate how much energy each coulomb have, or make current flow, or do both?

texts: Does potential difference only indicate how much energy each coulomb have, or make current flow, or do both?


texts: Suggestions about resistor values and additional components for this circuit?

texts:
I made the circuit above by using LTSpice where I can amplify weak, badshaped pulselike signals, shift their levels, and convert them to positive pulses. At the end I obtain a pulse train with adjustable offset and amplitude. U1 U2 U3 are universal amplifiers in LTSPice. But I am planning to use LM324 opamp for these. Here is the circuit:

Click here to see it bigger: http://i.stack.imgur.com/H0I5L.png

![enter image description here][2]

My question is this circuit looks ok at Spice program but I didnt implement it.

Any idead about resistor, poti values? Do I need capacitors or diodes?
Since I'm not a professional designer, I would like to have your opinions before actually solder/implement.


texts:
I'm using ap_axiu from ap_axi_sdata.h in Vivado HLS like I saw in some example to stream data throught the AXI DMA.

I'm defining my value like this:

typedef ap_axiu<32,4,5,5> AXI_VALUE;

However, and even though I can see the following correspondence:

32-->data
4  -->user
4  -->id
5  -->dest

I can't understand what the 4,4 and 5 are for. Can someone please explain me what's the difference between ap_axiu<32,1,1,1> and ap_axiu<32,4,4,5>?

Note: I think this is something that should be said on the header file ap_axi_sdata because it's somewhat important.


texts: My book says we can't connect a capacitor and a  bulb because it will cause flickering of bulb.Does it mean the cycle of current we see in power curve representation should be discontinuous because we are getting no current till capacitor is charging ? Or maybe I should not believe everything I read ?


texts:
I have two numbers both with four bits (a3 to a0 and b3 to b0 reading from left to right) and I would like to find out if a is bigger than b.
I have drawn a solution of mine and a short mathematical explanation of it, it would be amazing if somebody can tell me if this is correct.
So my idea is to to use full adders (which are named VA), where I have a, b and the carry from before as inputs. The carry from the current adder and q_{i} are outputs of it.
I negate all of my bits of b,setting C0 to one to add one so I have a two's complement and than I add both numbers.
One of my sources say's, that a>b when sign=0 and z=0. Z is 1 when all q_{i} are zero. And sign means (concerning my sources), that q3 is zero.
So in the end I came up combining it like the way I did on the photo.

Am I right with this?
Why is there no use of c3?


texts:
A 200mv peak to peak sinusoidal signal is applied to an ideal 12 bit A/D converter, for which Vref(v p-p full scale) is 5v. Find signal to noise ratio.

This is a problem worked out by one of my lecturer and the answer seems to be 46dB. But I am confused on his method. Is there anyone who could explain me how the result was worked out?


texts: How can I properly test compatibility of a replacement led on a pcb?

texts:
I am looking to replace an led on this board, but I am unsure of what this current led's specs are in terms of what amperage and voltage are used by the led. I am curious what ways I can test to make sure that the new LED I am wanting to switch with, wont damage the board.

I believe I can do some tests with the LED itself using a multi-meter for amperage and voltage, but not sure what settings to use.  Are there other tools/ways to test?  Is there a way to get a spec sheet somehow?

Is it possible to test the board itself to find out what amperage levels it could handle to make sure that the  led's amperage draw wouldn't damage the board? I would assume that too much current "could" damage the board, but in this case probably not since led draws are tiny(60 mA on the new one at full white brightness). I know my power supply can handle the led, but figured I should ask, just in case the board would break.

I'm a bit new to this field, so I appreciate any guidance to learning more about this, and any resources are appreciated, thanks you.


texts:
I'm about to update an old PCB design of mine using Eagle 7.5. The previous design used a DS18B20 and I want to replace that with a 1x3 0.1 pin header.

While I can delete the component from the schematic, some lines remain in the tstop layer (#29):

How can I delete these lines? I can't move them and I don't want them in my new design.


texts:
I have an asignment where I am supposed to express a current:

$$12sin(400t+100^o)$$

as a phasor. I am not shure what that means but I guess that I should express it on the form $$A\angle\theta$$
where $$Acos(\omega t+\theta)$$

How do I do that?

I tried, but looking at the solution, it seems to be that I should divide 12 by $\sqrt{2}$ and I don't know why.

Here is my solution which is wrong:

$$12sin(400t+100^o)=12cos(90^o-400t-100^o)=12cos(-400t-10^o) \Rightarrow 12\angle 10^O$$

I am also curious to know why $\omega$ seems to not affect the answer...


texts:
So to start off I am powering 70 LEDs through a 24V 6A power supply. The WS2812 LEDs require 5V operating voltage and  about 50mA at their brightest setting (white light). I'm having this really strange power issue and I'm hoping to get some help.

Baseline

With 10 LEDs powered straight through my Raspberry Pi I am essentially just shifting colors like a sun cycle. Black, red, gold, white sustained light for about an hour and then all in reverse. I'm able to do this flawlessly and with a good transition (no flickering). The past month, I've moved the set up from 10 to 70 LEDs through a LM2596 buck converter (From 24V to 5V) and then into the power supply as stated above. Again, they've been working awesome. The specs state this voltage conversion is completely within operating values. Here is where the issue is.

The Problem

These buck converters are rated at 2A which I recognize is above the threshold of 70 LEDs so what I did was lower the number of LEDs and wire another buck converter to the same terminal but in parallel to share the current draw (still 5V). This worked for a few weeks but now I'm getting flickering. Usually you would think that this flicker happens throughout the whole LED cycle but this ONLY happens during color transitions. So if I'm holding a constant color (the day cycle of the transition) then there is no flickering. What is really weird is that this buck converter, like stated above, worked completely fine for a long period of time. I'm absolutely below my current budget so I'm not pushing these past 4A

What I've Tried

I've changed out buck converters and this has just caused me to burn through more
Lowered LED Count to 5 but flickering is still occurring through the buck converter
Played with refresh rate of code but it doesn't help
Changed brightness levels but it will still flicker no matter what
Measured Voltage across the 24V power supply terminal and it's providing an adequate and stable output voltage
Change Wall outlets
Recheck wiring

I'm very familiar with these LEDs so I can say with certainty that it isn't my code or anything software related. It's very strange and I'd like some thoughts on why this is happening on JUST the flickering sequence.

Next Steps

I'll be looking at more robust buck converters along with more research on why this is happening on such a strange part of the light cycle.


texts: Esp32 i2c read command produces no clock signal

texts:
I am trying to read temperature from a SHT21 sensor using an ESP32-WROOM board. The I2C driver is from ESP-IDF SDK. This is my reading sequence:

cmd = i2c_cmd_link_create();
i2c_master_start(cmd);                              // Send i2c start on bus
i2c_master_write_byte(cmd, (I2C_ADD<<1) | I2C_MASTER_WRITE, 1);
i2c_master_write_byte(cmd, command, 1);

i2c_master_start(cmd);
i2c_master_write_byte(cmd, (I2C_ADD<<1) | I2C_MASTER_READ, 1);
i2c_master_read_byte(cmd, data+0, 1); // data MSB
i2c_master_read_byte(cmd, data+1, 1); // data LSB
i2c_master_read_byte(cmd, &checksum, 1); // CRC
i2c_master_stop(cmd);
ret = i2c_master_cmd_begin(I2C_NUM_0, cmd, 1000 / portTICK_RATE_MS);
i2c_cmd_link_delete(cmd);

Based on the recording from my logical analyser I can tell that all write commands are executed properly. However there is no clock for reading the response from sensor. The CLK line remains low for another 41 ms.

So where is the clock for reading the response? Am I using the I2C driver incorrectly? Is the 41 ms delay produced by the sensor because of clock stretching? But shouldn't then the ESP32 continue with the reading clock afterwards? Am I missing anything else?

Thanks for all responses!


texts: Trying to simulate a PWM model of a boost converter in gnucap

texts:
There's a paper called "Simplified Analysis of PWM Converters Using Model of PWM Switch (part 1)" by Vatché Vorpérian which introduces a "PWM switch" to model the switch and diode in a switching voltage converter.

I'm following along happily while he derives its properties and then he uses the model to get DC characteristics for a boost converter. This is where I started struggling, so I thought I'd try to simulate the thing in SPICE (well, Gnucap) to see if I could spot what I was doing wrong. This didn't help much...

Here's a circuit diagram (which is correct, since it appears pretty much verbatim in his paper):

D is the duty ratio. Here is the netlist I was trying to use to simulate things:

* Boost converter with PWM model

.parameter D=0.6
.parameter vg=10

.subckt tx p1 p2 s1 s2 PARAM: N=10
FP p1 p2 VS {1/N}
ES s1 int1 p1 p2 {N}
VS s2 int1 DC 0
RLnk s2 p2 1M
.ends tx

Vg 1 0 DC {vg}
Rp 1 2 0.1
X1 2 3 4 3 tx N={D}
Vdummy 4 0 DC 0

RL 3 0 1k

.print dc v(1) v(2) v(3) i(RL) i(Rp) i(Vdummy)
.dc

The results are rather unexpected!

* Boost converter with PWM model
#           v(1)       v(2)       v(3)       i(RL)      i(Rp)      i(Vdummy)
 0.         10.        10.004    -15.006    -0.015006  -0.037514  -0.022508

Can anyone spot something I've done wrong? In particular, the current seems to be flowing the wrong way, which seems pretty bizarre. I tried out the tx transformer subcircuit and convinced myself it worked, but I may have made a mistake.


texts: On p.9 of App Note CAN Eye-Diagram Mask Testing (https://literature.cdn.keysight.com/litweb/pdf/5991-0484EN.pdf?id=2186889), the eye mask is defined 60% - 90% UI.  Does anyone know how 90% is defined?  My eye diagram touches the 90% UI mask and I don't know what can be done.  Does it mean I may get BER? If so, how bad?  Thanks.


texts:
I have 3.3V micro and +/- 12V square wave input I need to measure.

As my MCU can only read 0 to 3.3V, I would like to ask the best way to "translate" this +/-12V signal into 0 to 3.3V.

I try to read but there are many many solutions and I can't figure out which is better to do.

I'm adding my actual schematics:

Signal is a PWM @ 1000Hz coming from EV car. I can read 0-12V to 2.625 V maximum in input.


texts: Need help reversing the rotation my motor

texts:
I'm pretty new at this. I was able to salvage the motor of a washing machine. How will I know if I can reverse the rotation of it? And how will I be able to reverse it if it does?

Also how will I know if this is an induction motor? Single Phase or 3 Phase?

It doesn't say anything like that on the name plate.

Here are the details on the name plate.

Welling YXB170-4B RMOTS0007PLZZ
220~240V 50/60Hz
170W  $P
1.4A  CL E

FOSHAN WELLING WASHER MOTOR MANUFACTURING CO LTD.

It has some sort of diagram on the right.

11 uF/450V then BLUE(CCW), BLACK, RED(CW)

UPDATE:

I opened a box where the wires go to and this is how it looks like inside.

Unfortunately when I opened it, there was a spring that jumped out and messed somethings inside. I tried to put things back together as best as I could but not really sure if I did everything right. At the moment, I would not dare plug it to an electric socket as I don't want it to blow up in my face or something :D.

Is there anyway to run this off using a battery? Hopefully this would be safer.

Appreciate it if someone to guide me thru it.

UPDATE 2018/05/19:

After messing up the box with all the gears, I'm a bit afraid of plugging it to the power since I'm unsure what will happen. Anyways, I would like to ask for some assistance. Here are a couple more images which I'm hoping to help me explain what I need to do.

Figure 1.0

In the image above, I labeled the objects based on my understanding.

A - Motor
B - This was the box that had the knob for turning the washing machine on.
C - Capacitor. Label says "SH CAPACITOR. SH.M 400 VAC 50/60Hz 11uF (-5/+10%) NUINTEK/KOREA".

Figure 2.0

The image above is a close up on the box (B in Figure 1.0). I labeled somethings that I have concerns with.

A - A metal that connects to a white wire that connects to the power (not sure if positive of negative)
B - A metal that connects to a blue wire that connects to the motor.
C - A metal that connects to a red wire that connects to the capacitor and motor. A black wire then connects the capacitor to the power.

My questions:

The metals (Figure 2.0) B and C are currently not connected to metal A. I haven't tried it yet but my guess is if I plug this to power, nothing will happen since these metals (B,C) are not connected to metal (A). If I want to turn the motor on, should I have metal (B,C) connected to metal (A)? If so, can I connected them permanently?
If I wanted to reverse the rotation, should I connect the blue wire to the capacitor instead of the red one?

Thanks.


texts: What impacts the cost of switching regulator

texts:
I am selecting a 3.3V output switching regulator (to power the MCU, LEDs, and some ICs) for a project and I am noticing that even after specifying a specific list of parameters that I am looking for in the component, there is a wide range in cost. I am seeing pricing ranging from as low as $0.30 and up to like $8; and everything in between. I don't want to go with the "cheapest" option since the switching regulator is an important component...but I also don't think I need a $3 regulator.

Some things that I think impact the price are package size and the number of external components required, but even still, from what datasheets I have gone through, I cannot fully confirm my hypothesis as to what impacts price. Obviously big name brand components are not the cheapest. Maybe efficiency and ripple impact the price as well? I don't have time to go through EVERY datasheet though and come up with the answer and unfortunately some of these parameters are not listed when just doing the component searches on digikey or mouser.

If anyone with a lot of experience with different switching regulators could shed some light on this, that would be awesome!

Here are some examples...

On the cheaper side, this Diodes Inc regulator is $0.45
https://www.mouser.com/datasheet/2/115/AP65211A-1143084.pdf

This TI regulator is $1.68
http://www.ti.com/lit/ds/symlink/tps54202h.pdf

Update:

The capability of synchronizing seems to play a big factor. Switching frequency and package size seem to be the main other driving factors.


texts: Components for adjusting the current and voltage of a very high energy power supply

texts:
I have two microwave transformers in series connected to a Cockroft Walton voltage multiplier. This allows me to generate well over 1 million volts (measured by spark gap) at high current (it looks like a flame due to heat.)
I want to manually manipulate the output.
I intend to use a buck converter to control the voltage and a variable resistor to control the current (with the combination of both tuning methods obviously controlling watts.)
However, I can't find affordable components with ratings anywhere near these power and voltage levels, does anyone know a way around this? Either a source for cheaper/different components or some other or DIY solution.
BTW, there's no need to worry about my safety, I'm very careful, and one hand is always in my pocket!!


texts: FT2232D - Device not responding to set address

texts:
I've ordered a custom planned PCB which contains an FT2232D chip.
Circuit looks like this:

VCC and USB_VCC are connected on another page.
GND and USB_GND are connected on another page.

Datasheet of FT2232D: http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT2232D.pdf
Datasheet of EEPROM: http://lomex.hu/pdf/(stm)_m93c46-m93c86.pdf

Although it seems starting upon connecting, no further steps could be done:

[23980.186603] usb 5-1: new full-speed USB device number 91 using xhci_hcd
[23980.277845] usb 5-1: Device not responding to set address.
[23980.569101] usb 5-1: Device not responding to set address.
[23980.769169] usb 5-1: device not accepting address 91, error -71
[23980.880898] hub 5-0:1.0: unable to enumerate USB device on port 1

I'm using self powered configuration, so the chip gets its power from USB port directly.
A 6 MHz XTAL was applied, according to datasheet. And I also applied an EEPROM (although it's not a must I think).

On Windows I got unknown device and then Windows disables it because thinks it works wrong.
FT_Prog doesn't recognize it either.

On Linux the dmesg shows lines above.
Device is not responding.

How could I move on? Do you guys seen anything like this?


texts: Series/Parallel DC circuit analysis training issue

texts:
I'm blocked in this exercise. I don't get how I can compute R1/R2/R3 voltage.

Here's the schema :

simulate this circuit – Schematic created using CircuitLab

So I was able to calculate some values :

\$ R_{T} = \dfrac{1}{\dfrac{1}{10k\Omega}+\dfrac{1}{7k\Omega+\dfrac{1}{\dfrac{1}{6k\Omega}+\dfrac{1}{1k\Omega+2k\Omega+3k\Omega}}}} = 5k\Omega \$

\$ R_{eq_{1,2,3}} = R_{1}+R_{2}+R_{3} = 1k\Omega+2k\Omega+3k\Omega = 6k\Omega \$

\$ R_{eq_{1,2,3,4}} = \dfrac{1}{\dfrac{1}{R_{4}}+\dfrac{1}{R_{eq_{1,2,3}}}} = \dfrac{1}{\dfrac{1}{6k\Omega}+\dfrac{1}{6k\Omega}} = 3k\Omega \$

\$ I_{T} = \dfrac{V_{1}}{R_{T}} = \dfrac{10V}{5k\Omega} = 2mA \$

\$ V_{R6} = V_{AppliedVoltage} = 10V \$

\$ V_{R5} = \dfrac{V_{1} \times R_{5}}{R_{4}+R_{5}} = \dfrac{10V \times 7k\Omega}{3k\Omega+7k\Omega} = 7V \$

\$ V_{R4} = (I_{T} - I_{R_{6}}) \times R_{eq_{1,2,3,4}} = (2mA - 1mA) \times 3k\Omega = 3V\$

\$R_{1}\$ should be equal to 0.5V, \$R_{2}\$ should be equal to 1V and \$R_{3}\$ should be equal to 1.5V. But I can't find a way to compute them... I've cheated a bit and take a look at all the answers to try to "RE" based on the excepted result but can't figure out what I have to do... Any ideas ?


texts: problem facing in running the three function in arduino

texts:
I am making and Arduino program for a 3 phase inverter.  I have designed 3 functions for each individual phase.
In 3 phase, the 2nd phase has to start at 120 degree with respect to first phase and similarly for 3rd phase.
I calculated a delay for it and I got about 6.67 ms delay.  After 6.67 ms delay, function 2 should be start while function 1 should continue executing and after 13.33 ms delay function 3 should start while function 1 and function 2 are executing.
Is the above logic possible? If possible, then how?


texts: Question regarding driving an audio system with a generator (without inverter)

texts:
We're arranging a music event where we're going to drive a few speakers and a dj controller. We've been trying to find a generator that would work and so far we only have access to three. All three generators are of the classic kind, they do not have inverters. The output is connected directly to the alternator.

The most likely candidate right now is a Honda ECMT 7000. It has an RMS of 6500 in triplephase which is more than enough for us.

Our issue is interference and voltage spikes. We're afraid that the generator could spike and break our equipment that will be connected through a power central 220v that converts triplephase to singlephase.

I've tried to search the web for an answer and everybody says different things. Half of the posts I see say it's fine and they've been doing it for years while the second half says it'll definitely fry the electronics.

What do you guys think? More specs on the generators and audio can be sent on request. The power is not an issue, we already know that. We're worried about the spikes.

Would the fuses in the central and some standard EU socket voltage protectors be fine?


texts:
I am a beginner with LED lights, but would like to use a 5mm 365nm UV LED diode to make a pendant with a small fluorescent crystal.
I would like to create a very simple, very compact circuit with a coin cell (watch battery), and an on/off switch. What would be the easiest way to do this?
I had asked a similar question earlier, but have a brief additional inquiry to make. How would the circuit change if I wanted to use an LED chip instead? Or if I added other diodes for extra brightness?


texts:
I have a pretty basic question. I put this little thing together but I don't understand why the POT is causing this result.

When powered, if the POT isn't fully open. LED 1 is bright and LED 2 is dim.

When POT is fully open LED 2 becomes VERY bright and LED 1 dims slightly.

Shouldn't they have equal brightness if the POT is fully open?

My guess is that it's happening because that they are splitting the current.


texts:
I have in my hand a AG9205s PoE PD module (output 5V and up to 13W) and I want to use it with my Raspberry PI 3B+ (that exposes the center core tap wires to the J14 pin header, as you can check here in the schematic)
Now comes my question: the AG9205s module shows that the external bridge rectifiers are needed as external part of the PoE PD module, as you can see here:

But at page 4 of the Datasheet, it says that the output of bridge rectifiers are connected to the respective internal pins, as shown below:

I'm a little bit confused...I've tried to connect the AG9205s module to the Raspberry Pi and works without any issue!
What am I missing? Are those bridge rectifiers inside the AG9205s module? Are they inside the LAN connector of the Raspberry?
Do I need to add those rectifiers?


texts:
Looking for definitions of items under Type and Electric in Diptrace Component Editor. I know it's for ERC control, but official tutorial doesn't cover this properly.

What is the difference between Type and Electric? If anyone could describe any item, that would help a lot.


texts: Need some help about why this circuit (PSU) isn't working

texts:
Trying to make a current limiter for my LM317 power supply. This is the complete circuit:

I found the current limiting circuit on the web, I'am powering this circuit from a 12V 20A switching lab power supply. The problem that i have is that current regulation doesn't work, voltage regulation works fine. but when i adjust the current (above 1 amp usually) the circuit completly shuts down. the 2n3055 transistors are a bit warm but that should not matter since i only wanna test if it's capable of 2 - 3 amps for maybe 2 seconds. But the circuit just dies.

If i leave it like that (dead) but still plugged in, it comes back on again after maybe 10 seconds, then shuts down again etc.

My first thought is that the LM317 overcurrent protection is kicking in, but since the transistor is taking most of the load that shouldn't matter right?

The LM317 is very cold btw. Not hot at all. My guess is that i simply forgot to add something but i can't figure out what..

I don't have any capacitors in this circuit on the breadboard, could that be the cause of the problem?

Thanks for any help in advance!

LM317 datasheet: http://www.ti.com/lit/ds/symlink/lm317.pdf

2N3055 datasheet: http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF

Update: I just noticed that current changes when i put a finger on the current regulation pot.. if it shows like 300 mA and i put my finger on it, it goes down to maybe 150 mA and jumps around until i remove the finger.. (Tried to change the pot but same problem occured)


texts: BJT one stage amplifier with current source

texts: How I can correct my schematic to properly set the current source in the emitter of BJT common emitter stage? I can't understand how to properly bias the Q1 using R3/R4 voltage divider. How to find values of that resistors if unpredictable resistance of current source exists in emitter of Q1. It seems to use the current source must stabilize Q1 emitter current but don't spawn new problems!


texts: Mysterious current appearing on Ltspice using LT6018 opamp

texts:
Do you have an idea of where the 120 mA current (going through Cact) is coming from ? I just can't understand how the LT6018 can output that much when the datasheet says it can output max 50mA. Even if it has to saturate, it should saturate at 50mA.
Note: I tested different frequencies and it seems like it  reaaaally depends on the used frequency..Also the capacitors value have an influence. Sometimes it exceeds 50mA sometimes not(and sometimes it's chaotic).


texts: getting more from batteries via series connection

texts:
Let's assume I have a 100W load.

If I run this load on two 2000mAh 3.7V batteries in parallel then I should get a continuous run time of 8 min 53 seconds (given the 27 amp draw).

However if I were to take the load and modify its resistance so it would draw 100W on 7.4V then I will have a draw of 13.5 amps from the cells. This should give a continuous run time of 17 mins 46 seconds.

All this is considering the way voltage has a larger effect on wattage than current.

Are my calculations correct in this sense? (I'm aware a 100W load is rather a lot for this voltage, but its just a rounded number for an example).

Also assume the second load of higher resistance performs the same as the first, lower resistance, load e.g. light/heat output.


texts: Identify an internal wire connector on the original NES

texts:
I am trying to identify a wire connector used on the main board of the original NES(Nintendo Entertainment System). I have been successful in identifying other connectors using online resources, but this one has me stumped. Other online forums(including NES dedicated ones) have been unable to help. One primary problem is identifying the manufacturer as there is only a single letter and an obscure logo.

The connector is identified as P6 on the main board.

Info I have:

5 pins - keyed with pin 1 at 1.5 times other pitch
pitch from pin 1 to pin 2 = 7.5mm
pitch for all other pins = 5 mm
connector is between 6 mm and 6.5 mm high
connector is between 27.3 mm and 27.7 mm wide
connector is about 4.2 mm deep
pins are about 1.1 mm - 1.2 mm square

(measurements are approximate, my digital calipers are a bit cheap, sometimes randomly adding exactly 1/5th of an inch to measurements - these are double and sanity checked)

There is no manufacturer name on either part, just a single letter('P') and a circular symbol that kinda looks like a 6 sided star, divided into 6 segments in a ring. This symbol is also found on one of my NES systems on the power and reset switches, still no company name. Other NES have Mitsumi switches, but they don't seem to be the same company.

Let me know if any other information will help.

Image of the logo:

Image of connector:

Left is pin 1.


texts: Relationship of complex load angle, voltage/current phase different and load factor

texts:
Question:

Explain the relationship of the load impedance angle to the displacement coefficient cos(1) and the power factor λ at the input of the rectifier

Not sure exactly what its asking for.
It probably needs the relationship of all 3. The load is an inductor (1H) and a 50 Ohm redistor in series, 1 is the angle between voltage and current, the power factor λ is \$\frac{P}{S}\$.
So far I though about using \$Pin=Pout\$  \$I_{s1,rms}V_{s,rms}cos(φ1) =\frac{1}{T}\int_{0}^{T}V_d(t)i_d(t)dt \$
then substitute \$i_d = \frac{\sqrt{2}V_s}{|Z_0|}sin(\omega t - \phi)\$ where \$\phi = arctan(\frac{\omega t}{R})\$
Not really sure what I'm looking for and where this is going. I'm making this post not because I am looking for someone to solve this for me but to throw some ideas about what I might be looking for and ways to approach this problem.


texts: Can I use 1000v rectifier diodes instead of 600v rectifier diodes?

texts: I plan on doing some wiring but the directions are asking for 1A 600v rectifier diodes. I could only get my hand on 1000v rectifier diodes and before I continue I want to make sure this is safe as if I wont cause a fire or a short or make something blow up.


texts: Dual Op Amp should be saturating but it is instead tracking the negative pin input

texts:
I was attempting to implement figure Figure 34 on the AD734 datasheet in multisim (the national instruments SPICE simulator)

Based off what I know of op amps, the output of U2b should be saturated to rail voltage (in my simulation it is supplied by +15 V to -15 V), meaning that the diagram in the datasheet is incorrect (ie., it doesn't output the rms of V_in).

My problem is that within NI multisim, with the circuit as depicted in the datasheet, it works perfectly. Within the simulation the output of U2b is the same as the input to the negative pin. Within the simulation if the negative pin input is replaced with a voltage source, the output saturates to the rail voltage as you would expect. If the AD708 pair is replaced with a pair of virtual ideal opamps, the output also hits the rail as I would expect.

I suspected that Figure 34 is incorrect, but multisim is backing it up, and I don't see how this isn't a bug. Would this circuit work in reality?


texts: 256 : 1 or 64 :1 or 32 :1, 5v multiplexer to handle 256 analog signals

texts:
I have an arduino mega and 256 analog sensors that I have to read. I already did it with a lot of 4067 16:1 multiplexers. At first it took all of my pins. Then I paralleled the multiexers to use only 4 digital pins to Control them and played with the E of them to turn them on or off.
Now my question is : is there a 256 : 1 multiplex that operates in the 5v range so my mega can handle it (or even smaller arduino) or if not a 128:1,64:1, 32:1. In order to make my board simpler.
Thank you very much for your time reading this. Have a nise day.


texts: I'm curious about keypads in regards to voltage.  I have searched, and not found much related to this topic.  It seems to me that keypads can take nearly any voltage so long as the voltage supplied is greater than the voltage dropped by the keypad.  This wouldn't make sense though since most keypads list themselves as 12VDC.  Can a keypad labeled for a higher or lower voltage take a higher or lower voltage?  For example, supplying a keypad labeled 12VDC with 5VDC.


texts:
I have seen cases where TFT module contains flash or SD card on module. What is the need of flash in LCD?

In simplest way, we connect RS,RD/WR,CS,RESET pins and 7/8/16/24 bits data pins of controller to LCD. So, why this memory provision is there on board.


texts: Relays in series to handle initial short circuit

texts:
I'm trying to design a circuit to turn on and off an electrical 230V 1A 1-phase motor using a relay.  I'd like to design it such that if the user inadvertedly short circuits the output, the relay is immediately opened.

My best idea so far is to use two relays. The first relay is in series with a 30 ohm resistor and with the load. The second relay is in parallell with the resistor.

If there is a short circuit when the first relay is turned on, this is sensed by a current sensor, and the relay is immediately turned off before the resistor overheats (a few ms). The current here will be <10A because of the resistor.

If there is no short circuit, the second relay, which is connected in parallell to the resistor, is switched on. This lets the full current through, and saves the resistor from overheating.

The whole thing is controlled by a microcontroller.

I think that if I only use one relay, and there is a short circuit, the inrush current may be in the 1000 of A, which I think a regular small relay cannot break.

Does this sound reasonable?

If not, how would you build a short-circuit disconnect function for a relay-based 230V motor controller?

It doesn't have to handle short circuits which occur during operation,  only before startup.


texts: Should I using ground pours to surround high speed lines?

texts:
Previously I've been using ground plane pours in Eagle to connect ground points and also to surround lines that I feel need protecting from surrounding noise. This is on two layer boards. By drawing a GND poly around the dimension layer on top and bottom you can connect all GND points without thinking too much. Less etching is a plus too, even if you end up with planes that are islands (I'd normally via those to a bottom ground plane)

Olin and others indicate it's a bad idea to do this. Thus I've been localising my ground planes:

The above image has GND highlighted and I haven't done the local ground plane pour around IC1 yet (on top or bottom). This is a '245 level shifter from 1.8V to 3.3V. As per Olin's post, I have GND local and then viaed to the bottom ground plane at one point after a decoupling cap.

Most of the bus lines coming off are SPI at 10MHz and GPIO lines. The GND line at the top is a "protection" line - like crystal guard ring - between SPI CLK and I2C lines above it. It's supposed to indicate where I'd pour a ground shield.

I don't know where to connect that ring though. Not to the local IC1 ground plane surely, even though it's part of IC1 signal outputs?

As my bottom GND pour will be one single plane, should I presume any top shield pouring can connect to the bottom pour at various points?

I'd like to know how to do it properly as doing a poly GND around the dimension line in Eagle causes the shield ground pour to connect all the other ground pours which is not what I want at all. Should I use what Olin called "shorts" between GND and SGND (shield ground) and then do an SGND poly pour?


texts:
I am using LM2596 Step Down module to regulate 12VDC to 5VDC on a pcb board.

The board specs are:
Voltage = 5 VDC
Current = 3 Amps

Normally the setting on the module will be correct and the output correctly tuned to 5V. BUT, for some reason if it isn't, it will fry the electronics on the board.

How would you suggest overvoltage-overcurrent protection be put in place in this scenario?

I can't seem to find such high ampere rated OV/OC protection IC available on the marker. If you know one, kindly name it in the answer.


texts: Difference between USB upstream and downstream ends

texts:
I'm doing a custom mobile robot project which utilizes Raspberry Pi, Arduino and I want to grasp the concept of the USB standard (http://www.usb.org/home).
When reading about USB cables I've encountered the distinction between 'upstream' and 'downstream' connectors (https://computer.howstuffworks.com/usb1.htm) which is supposed to prevent any mistakes of connecting the wrong end of the cable to PC/printer etc.

So here comes my question: Why there is a distinction between the upstream and downstream if the data can flow in both directions?

If I connect my printer & scanner to my PC, I can print a document using the printer from my PC (so data flows from PC to printer) but then I can scan a document on my printer and save it on PC (data flow from Scanner to PC) so it seems that the one side can be downstream or upstream.


texts: State Space model for three-loop circuit

texts:
How do I choose the least number of state variables for the following circuit? I started out by assuming currents $$i_{1}, i_{2}, i_{3}$$ in each of the loops and applied KVL, which fetched me three differential equations:
$$
i_{1} + 2\frac{di_{1}}{dt} - 2\frac{di_{2}}{dt} = v_{i}(t)
$$
$$
2\frac{di_{1}}{dt} - 3\frac{di_{2}}{dt} + \frac{di_{3}}{dt} = 3i_{2}
$$
$$
\frac{di_{2}}{dt} - \frac{di_{3}}{dt} - i_{3} = v_{o}(t)
$$

But when it comes to choosing the state variables, while keeping the number to minimum, I am unable to proceed. Can anyone help me?


texts: Regulating a small clockwork synchronous AC motor

texts:
Is it possible to drive a small synchronous motor with permanent magnetized rotor to other speeds it is designed for?

I tried to drive a small clockwork AC motor which is symmetrically build but mechanicaly constrained to one direction. I tried to drive it at different frequencys, while some lowers (eg. 20 Hz) seem to work to some point, the motor seem to stall at higher frequencys above 100 Hz it seems. Also I could not test at lower frequencys so far.

The voltage it needs to spin up rises with the frequency it seems. At 20 Hz, it works from 40 V, while it almost need the 220 V it's rated to spin up at 50 Hz.

Is it possible to spin it at 1/10 or 10 times of the design frequency if the voltage is adjusted, or is the frequency limited by design?


texts: DIY Ozone Generator: difference using plate-based or tube-based solution for corona effect?

texts:
I wanna build an ozone generator to use to sanitize object, cloths and so on.
Searching on internet I found two main solutions:

Plate Based (or in some cases based on very sharp nails or pins)

Tube based

As far I understand right now, both solutions work with an high voltage (HV) tension around 3KV or 4KV and are based on corona effect, but the tube method seems better in terms of O3 quantity generated.

About the solution (2), I found a video on YouTube where the makers use a neon/fluorescent tube instead of plastic tube. In the video they explain as "inner conductor" it's better to use an ionized gas, instead of another metallic mesh, to maximize the efficiency.
So to build it they wrap the neon tube with a metallic mesh, then connect one wire of the HV geneator to the neon tube pin and the other one to the metallic mesh around the tube.

Video link: https://www.youtube.com/watch?v=OFMKA1MgyGw

I'm a bit confused about that, so I would ask you: which solution is better to implement to maximize the power consumption/ozone generated ratio? And in case of the neon tube how long should it be?


texts: Multiple Servo, Move when not powered on

texts:
So I am trying to control 28 servos to make a 7 segment display clock with moving segments. Using a single signal line and 4 p channel MOSFETs and 7 n channel MOSFETs and a binary to  7 segment decoder(cd4511).

Link to video

Below is  a sample schematic and after that the real schematic, I know both MOSFETs show up as N-channel but the end  product has the proper P channels with correct pinout, you can also view the actual board, the module in the middle is for an RTC, next to barrel jack is Vreg for the micro controller and Vreg for the servos

Look at the images provided for reference in the real schematic because in my schematics I use labels and not real lines so I am not sure if that will help you understand the circuit, so that's why I drew a sample one with lines. I also have a video link of one of the digits working as expected but the issue arises once I connect the rest of the digits.

First, there s a CD4511 Binary to 7 Segment decoder, this will take 4 inputs ABCD, A being least significant bit, I drive those pins high and low to make a binary number between 0 and 9. The IC then drives the corresponding output lines (ABCDEFG)high to make that number appear on a segment display.
However I am not using it to drive an LED Display, instead, I am driving MOSFETs which are acting as LOW side switches for the Servos, All 28 Servos! However not all 28 are actually on because for every 7 servos (hence one digit) I have a P-channel MOSFET as a High side switch, that I control with the microcontroller, So when the time changes I only change one digit (7 servos) at a time and never all 28 servos.

So for example , If I want the first digit (the ones digit for the Minute) to display a 3 , i would set A and B high on the CD4511 chip, this would then through the N-channel MOSFETs provide the low side for the servos, then I would also activate the P_channel MOSFET via the microcontroller to only provide the high side of the first 7 servos which correspond to the ones digit of the minutes. So now those 7 servos are "on" and I give them the PWM signal to move their arms to the desired position that will reveal the segment like in the video. In theory the rest of the servos are not ON because the CD4511 decoder is not turning their MOSFETs on and I also have not turned the high side MOSFET ON for them either... the problem is that they DO move and the ones that I want to move don't move properly!!! and not to the position set by the PWM  signal but just erratically, Now If I unplug all the servos and only leave 7 servos plugged in, doesn't matter what 7 servos it is but so long as I only work with one digit everything works fine like in the video, the problems are when everything is plugged in....I just can't figure out why? PWM signal looks clean in the scope.


texts:
I need to design a circuit able to enabling and disabling a voltage source and its respective reference (GND). The power supply has a adjustable voltage output and can supply 12V, 5V, 3.3V and up to 5A at 12V. It will be a source for powering external circuits that can be any, as long as they are within the capabilities of the source.
To accomplish this task, I thought about using the following circuit:

Does anyone have any experience or observation about this type of circuit?
Corrections:
The mosfets were mirrored


texts: How can we power Christmas LED lights without mains supply

texts:
I have read the other thread 'Best way to power Christmas lights without nearby outlet' and my question does differ.

We have a Christmas Tree which sits in the middle of our Village Green every year. The lights need to be on from about 4pm until midnight every day for almost a month. Until now, we have used multiple threads of battery powered Christmas lights (AA/AAA) but the results are not very good, with the lights being very dim.

We would now like to power normal (mains) bright LED Christmas Lights by some means. We have explored all options of connecting to a mains supply and they are prohibitively expensive. The current thinking is that we should use some sort of car battery. (Using a generator has been ruled out as being too noisy).

My question is what specification of car battery would we need to get to power about 600 lights for a month, hopefully without having to charge the battery too often. Is this even possible?

We have not yet purchased the lights, so we could buy ones that suit the battery. I appreciate from the other thread, we may need an inverter. The question in the previous thread related to powering lights for only a couple of hours, so this is a very different scenario. Also they already had the lights they wanted to use, whereas we can choose lights to suit the battery.

Thank you in advance for any help.

Suzanne


texts:
I've got a USB device that requires 12 watts to charge.

My laptop appears to output less that that.

My question is: Is it possible to step-up the output of a laptop USB port to 12 watts?


texts: How to cycle through bits of information for a hex display?

texts:
I am doing some work with a Hex Seven Segment Digital Display with a built in decoder that takes in 4 bits of information. Controlling it I have 4 cascading T-FlipFlops whose outputs are inverted so I iterate through its states backwards rather than forwards.
It has the following states 1,2,3,4,5,6,7,8,9,A,b,C,d,E,F.

For example to view a 3, the first two bits are set to High, and the last two are set to off. To view an E for example the first bit is off, and the last three bits are set to High.

My problem is that I don't know how, or what is the best way, to skip the alphabetical characters, and cycle through just the numerals 1,2,3,4,5,6,7,8,9 then back to 0. What is the best way to do this.

I'm not coding, there are no micro-controllers this is all digital logic.


texts: Can I calculate the parasitic capacitance in Altium?

texts:
As you know for calculate the capacitor of crystal(for MCU) you should use of this equation:

  CX = 2*(CL - Cstray)

We can find the Cl in crystal's datasheet but, for Cstray, we should calculate:

  The capacitance of the microcontroller pins (data sheet) + The parasitic capacitance of the traces on your board (can be approximated knowing length, width and layer of the traces).

I use AVR and I couldn't find the capacitance of the microcontroller pins(if you know, please tell me) but, my problem is that I don't know how can I calculate the parasitic capacitance of the traces. can I calculate it by altium? if so, how? if no, please provide a program untill i use it for solve my problem.


texts: Damaged Bosch battery charger IC identification help

texts:
I accidentally damaged my Bosch cordless drill battery charger by hooking the charger's PCB's 12 volt lines directly to the 220V|50Hz AC mains.
The charger's model is AL 1110 CV https://www.amazon.co.uk/Bosch-POWER4ALL-Li-ion-Battery-Charger/dp/B0777RXTKJ
I suspect, that this IC is at fault:

I cannot find much info about it online.
Any help finding this IC (and what it does) or an equivalent alternative will be much appreciated!
Thank you


texts: Use port for comparator and analog input?

texts:
I'm trying to use Port F on the PIC18F65J11 as both analog inputs and a comparator. For example, there are 7 pins on Port F, and I'd use 3 pins for comparator (2 comparator inputs, 1 comparator output) and the rest for analog inputs.

I know that you can configure it so that comparators are enabled, or you can turn of comparators. I'm reading the data sheet, and I'm confused how to configure it so that I can use comparator and analog inputs on Port F at the same time, if that's possible.

For reference, here's the data sheet: http://ww1.microchip.com/downloads/en/DeviceDoc/39774d.pdf. Page 143 talks about Port F. Page 260 talks about analog inputs. Page 270 talks about comparator module.


texts:
We are planning to use this power-line-filter to reduce the possible power line noise in our data acquisition system. And the data-sheet as pdf can be downloaded from here.

The data sheet shows the wiring diagram of the filter as follows:

But I was planning to use this filter for PC and many transducers ect. by also maintaining the safety.

So for my question I have drawn the following:

As you see above if I use this filter between the power outlet and the power strip as in 2nd figure, the earth connection(yellow-green wire) no more exists after the filter. I have equipment which is chassis grounded to earth for safety.

Wouldn't it be risky to use this filter since earth wire cannot be used anymore for safety? Does anybody have experience with such application and filters?


texts: Is it possible to use a raspberry pi to control these LED strips?

texts:
I want to control some LED strips (inside PVC tubes) with a raspberry pi. Is this possible? Where would I start?

The problems are, I don't have a lot of info about the strips:

LED Chip Model:SMD5050
Brand:Epistar
LED Chip:Epistar 48PCS SMD
Input voltage:DC12V DMX512 led digital tube
Power:Around 12W/Tube DMX512 tube

I got about 80 of these tubes. The idea is to build a 40 by 2 tube array and to use it as a display.

Thanks a lot for any help!


texts: Control System: Model a simple flow valve

texts:
I was reading a paper about a Controller Design for Temperature Control of Heat Exchanger and I couldn't understand how to model the valve used in the system.

No need to read the paper as I will wrap up the whole issue:

Given:

capacity of control valve is 1.6kg/sec
time constant is 3 sec
valve input is pressure varying from 3 to 15 psi

The resulting transfer function is:

It is obvious that they considered the valve as a first order transfer function.The gain Kp was calculated by: (1.6kg/sec)/(15-3)psi=1.6/12=0.133. Time constant=3 seconds and that's it.

But the problem is: shouldn't a step input of 15psi output a signal (1-exponential) with a final value of 1.6kg/sec. But that transfer function won't actually output that. It still needs some kind of a shift. So Am I missing something? Is the model wrong?

I also simulated the transfer function response with MATLAB SIMULINK along with a suggested alternative that probably solve the offset thing:

The resulting waveform:

zoomed in near time=0seconds:

The yellow waveform is the input step function
The blue waveform is the output of the transfer function of the valve
according to the paper.
The red waveform is the waveform of the transfer function with an
offset.

problem with the blue waveform: wrong final value.
problem with the yellow waveform: starts from a negative value (-0.4
kg/sec)

So what is the correct model?


texts: I am wiring up an AND gate with 2 2n2222 transistors, a LED and 3 10 Ohm resistors. When I make the AND gate, the LED lights up but there is a weird smell coming from the resistor wired to ground. When I touch the resistor, I find that it is hot! The circuit is wired up correctly and I am giving the right voltage. The only thing is that I am using 10 Ohm resistors instead of a 1 Ohm resistor.


texts: I have read that power of a periodic signal is calculated for a single period (correct me if am wrong). So why can't we calculate energy of a periodic signal for a period and say it has finite energy. Why this is not the case ?


texts:
I have this circuit

My task is to match these four statements.

"\$v_1=0\$ for a very long time. The time constant for the charging time for the  capacitor immediately after \$v_1\$ jumps to \$v_1=10V\$ is ...
"\$v_1=10V\$ for a very long time. The time constant for the discharge time for the capacitor immediately after \$v_1\$ jumps to \$v_1=0\$ is ...
\$R_2\cdot C\$
\$(R_1+R_2)\cdot C\$

I can't really find any arguments as to why these statements belong together.

Has it something to do with the diodes not being forward biased? I hope someone can clarify this for me.

Edit

The main problem I have with this, is that I don't exactly understand how the capacitor is charging and discharging through the resistors, and when and why the diodes are conducting and non-conducting.

I just saw the answers to this problem. For number 1 they have this drawing.

For number 2 they have this drawing.


texts: Op-amp - can't choose the right model for the PCB model

texts:
I'm thinking of using an op-amp in my circuit.
Here is my circuit:

Now I'm making the PCB model in KiCAD:

I don't know how to find the right model of my op-amp -> U1, U2, and U3.
Can someone point me in the right direction towards choosing the right op-amp?


texts: What options are available to sniff LVDS communications?

texts:
I'd like to capture packets on LVDS communications links. These links are a single pair in each direction - TX and RX, point-to-point, with 8b/10b encoding. I'm looking for options to sniff communications on these links to analyze packets for debug purposes. For most other communications links such as Ethernet, RS-232, I2C, USB etc - there are options to sniff communications on the wire or in a repeater or receiver. What about LVDS?

1 option is to modify an FPGA on 1 side of the link to buffer TX and RX traffic. This offers the advantage of gaining access to decoded data but this approach also has the disadvantage of modifying one of the components being debugged. It would be nice to be able to tap into a comm link and capture traffic.

Why would I do this? To debug communications problems caused by noise, hardware problems or bugs in code - the same reason that sniffers are used on other types of communications links.


texts:
Will my circuit work for the following goal?

When INPUT_N is HIGH (i.e. micro is not driving it and it is pulled up to 3.3V), VCC pin on device will have 24V.
When the microcontroller drives INPUT_N to be LOW, VCC pin is at 0V (so device is off).

Should circuit below work as intended?


texts: Is it possible to power a microcontroller via inductance from an AC power line?

texts:
I have an AC mains wire powering a pump running at 220V at 5-10A. Is it possible to wind a secondary wire around the outside of the insulation of one of the two "hot" wires (single-phase) to get low-voltage AC that could be rectified to DC and used to power a microcontroller?

The goal is to monitor current while the pump is in use, using a separate split-core transformer as an analog input, and report usage via Wifi or Zigbee without requiring a separate DC power supply.


texts:
What I do not want is one of those RFID readers which attaches to serial or USB port and writes its input to stdin.

I am looking for cheap & nasty RFID reader which I can query over serial or USB; a bonus is if it is also an RFID writer but doesn't add too much cost.

Coding something like:

fopen(com1);
fwrite, com1, "hey, you, send me some input");
read(com1, ipit_value);
fclose(com1);


texts: Two Different Charge Pump Circuit Variants. What Are Their Advantages?

texts:
While looking at the L6470 stepper driver datasheet I came across the following charge pump circuit suggestion (I will just name it Variant A).
The charge pump is used to provide the "Bootstrap voltage needed for driving the high-side
power DMOS of both bridges" 1.

As a beginner, so far I only knew about the circuit below (say, Variant B).

My questions are:

What are the advantages of two different charge pump circuit
variants?
Are both interchangeable?
Do applications exist where one of them is the preferred choice?

To get a better understanding, I tried both variants in the simulator on falstad.com (see link for live circuit).

I used a resistor (10k) as load in both cases.
Is this maybe inadequate as variant A is used to charge the power mosfet gates?

So far my conclusion is that Variant A requires a smaller voltage rating for the second capacitor, but seems to draw more current from the main source.

Thank you!

L6470 stepper driver datasheet

live circuit


texts:
When designing a transmission link, are there any standardized/typical objectives for maximum bit error rate? Apart from some papers speaking about values like \$10^{-10}\$ or \$10^{-12}\$ for optical fiber I not only failed to find something comprehensive, but I found hardly anything at all. Just some measurements/simulations.

I'm mostly interested in values for wireless links, but anything about wired connections is appreciated as well.


texts:
I'm building an indoor greenhouse, I have gather a few tutorials on how to achieve what I need but on the heater I bought I can't seem to find anything that could help, and my knowledge on electricity is a bit shaky.

I'm using an ESP32 to control the sensors and valves I need and I thought that I could control this heater (https://www.ebay.com/itm/322871906747) with the ESP32 and a mosfet. The mosfet(IRFZ44N) is rated for 55V and 49A which is safely above what I need.

Upon receiving the heater I tried to test it with some dupont cables and PC power supply but those thin cables couldn't handle the 12A that the heater was trying to pull so they melted. After this little accident this got a bit real (I come from a software background where a bad day is when you crash something important but starting a fire is a whole new level).

I read that the problem was the thickness of the cables I didn't seem to find a clear way to check how thick I needed to be to be able to handle all the amperage but I'm sure this I can figure out.

My question is handling this kind of power on a breadboard will burn down my house wont it? (because this greenhouse it's supposed to take care of itself and being unattended for most of the time)

How can I safely build it without soldering? (I have shaky hands and zero soldering skills)

I'm planning to use a PC power supply for everything but I have no idea what resistors and or diodes I would need to keep the usage o this heater safe. (I have ordered 1N4001 diodes and 0.25W 1K OHM resistors for other sensors and valves but for this I don't think It will do. ( some reading materials for understanding this are welcomed)

Lastly connecting thick cables to the mosfet seems wrong (for lack of a better word). I bought some dupont connectors I was thinking on using these with the thicker cables on the breadboard but now I have no idea how to connect them.

Thanks


texts: KiCad: "No footprint for automated placement"

texts:
I just finished my first PCB with KiCad. Now, I need to produce it and I need the Pick and Place file. When I try to generate footprint position files the software produce the message "No footprint for automated placement". I'm using the version 5.1.4-e60b266 for ubuntu 18.04.1.
How can I generate this file? How can I solve?

This is my PCB:


texts: Adding solder to PCB traces to increase current flow

texts:
If I have a PCB with standard 1.4 mil copper thickness. I have used a trace width calculator based on IPC-2221 to determine that a 2.72mm trace is enough to handle 5 amps for an "external layer in air".

I have seen many times on power supply and relay board that people add solder to unmasked traces to increase the safe current flow.

I am using Sn63Pb37 solder. My finish is ENIG. I know that solder is much less conductive than copper.

My question is how much does this help? If I lay a fat convex blob of solder over the entire length of the track what ballpark level of increase in safe current flow can I expect?

I am sure an exact answer relies on various circumstances but a conservative value would be helpful.

I have seen in various claims on the internet that it can increase the amount of safe current by 40%-100%, but the sources seem to contradict each other. I would like to get an educated answer.

Is there any reason why doing this is a bad idea?

[EDIT]

I am going to attempt to answer this myself based on the information at PCB Tinning to increase current about how to figure out conductivity based on cross section and KalleMP's information about solder conductivity. Please correct me if I get any of this wrong.

Assuming a 1.4 mil thick copper trace with a width of 1 mm(to make the math simple) and a convex layer of solder going .5 mm tall at the highest point.

The cross section of the trace is a rectangle 1 mm wide by 1.4 mils(0.03556 mm) tall which gives an area of 0.03556 mm2.

Assuming a circular shape a 1mm wide and .5mm tall blob's cross section is a half circle so I use pi * .5^2/2 to get an area of about 0.3927 mm2.

If I go my what KalleMP said about solder being about 9-14% the conductivity of copper I can conclude that the effectiveness of the solder should be the equivalent of 0.035343-0.054978 mm2 of copper which is a 99-154% improvement, less depending on how thick the solder blob is.

This answer seems consistent with some of what I have heard from others, but I have also read of people doing actual tests and finding it closer to 40%. Does anyone see any fault in my reasoning? Are there other factors that would reduce the improvement such as the connection between the solder and copper?

[Note] at first I posted a different solution with an error, I think I have it right now.


texts: How to connect a 12V battery to a 24V system?

texts:
I have a 24V battery (two 12V lead/acid in series) connected to solar panels and I'm looking for a way to have a 12V battery and circuit. (But the solar array will charge the 24V system so i need the 12V battery to be charged with power from the 24V)

I bought :
- A 12V battery
- A Step-down 24V to 12V converter 30 Amps

Can I simply connect the 24V to 12V converter to the 24V battery and connect just after it the 12V battery? Or do I need something else, like a battery charge controller?


texts:
I'm building a battery powered device based on ESP8266. There are few buttons (lets say 4 at the moment). After pushing any of them ESP should perform some action and go to deep sleep mode. Next press of any of these buttons should wake ESP up so it can perform another action and go to deep sleep mode again.
So what I need is to put RST line to low for a while (about 100us) on any button press but keep proper GPIO low as long as button is pressed.

I came with the following idea:

simulate this circuit – Schematic created using CircuitLab

Unfortunately it doesn't work very well. There are two issues: one is that it's not reliable - for unknown reason voltage on RST drops low enough only when I press SW1, it used to work for other switches too but it stopped after some time (oscilloscope shows that it drops to about 2.0V). The other issue is that there is a voltage spike on RST line when I release the button - it goes to about 6.6V because capacitor is discharging. Maybe these spikes damaged other (electrolytic) capacitors because I tested my software mostly using SW1?

Do you have a better idea how to reset ESP with multiple buttons and still be able to detect which one it was? I'd like to avoid anything which draws power when not used or would take much PCB space (it's very limited).


texts:
I understand that dividing a wire into multiple insulated pieces reduce the Eddy Currents, and that reduces the magnetic field inside the wire, which leads to increased skin depth.

But why do they twist these insulated sub-wires? What is the importance of twisting? And how do we decide how much to twist?

(Image Source)


texts:
I would like to use a Arduino as "simulator" in a training class. It would connect to an industrial controller that has 24 VDC inputs and outputs. The Arduino program would simulate the IO from a production line (sensor inputs and motor controls for example)

Is there a shield which can interface  with 24 VDC IO? I know I could use separate relays, but I want to see if there is a better solution.

I could use 12 VDC instead of 24, but nothing lower.

I am considering the Arduino as cost is factor. So I want to keep the component count and price as low as I can.


texts:
Using external PLL clock Multiplier ICS501A

The crystal is http://www.txccrystal.com/images/pdf/ab-automotive.pdf

I need load capacitors on crystal ?


texts: How does a gas grill starter spark work?

texts:
On some gas grills, there is a button you push which creates a spark to ignite the gas (propane, natural gas etc.)

My questions are probably pretty simple:

How does the button create the spark?

What voltage is this spark?


texts:
An interesting thing about a few unique DT signals is that although they may be periodic in the DT domain, they are aperiodic in the CT domain.

One example of such a signal is:
$$x[n]=\cos\left(\frac\pi{10}n^2\right)$$
(whose fundamental period is sought out for in this video, at 10:18: https://www.youtube.com/watch?v=AhoeYb6Qq2c).

What are some other examples of periodic DT signals that are aperiodic in CT?


texts:
Is it reasonable to use a ferrite transformer from a big SMPS (LCD TV power supply) as a mains transformer, assuming I split the transformer in half and rewound the coils to provide the proper impedance? Ferrite transformers are generally operated at high frequency, but I don't know enough about transformers to know what happens if they are operated at low frequency.

I just want to know if it would have a reasonable efficiency, I'm not planning to do anything with it myself.


texts: Why the MOSFET VDSS is measured at 250 µA?

texts:
General defintition of the MOSFET VDSS is " BVDSS is usually defined as the drain to source voltage when leakage current is 250uA"

How this number 250 µA came? or What is the significance of this particular number?


texts: I was checking out a circuit for power management. That's when I came across this unknown component which looks so much like half a transformer and a switch. What exactly is this?


texts: How to start separately excited motor with 4 point starter

texts: How do we connect a 4 point starter to a separately excited dc motor?  Do we keep the F terminal open?


texts: I've got an Arduino Duemilanove and am programming it in C with AVR Studio.  Is there any way to get a source level debugger to work with this setup?


texts: I am taking a course from edX called computation structures: 1.Digital Circuits. When the course explained about CMOS timing, there was propagation delay(tpd) and contamination delay(tcd). I understood that tpd has to be upper bound but I couldn't understand why tcd should be lower bound. Shouldn't tcd be upper bound too?