texts: Quick junction / pn junction diode clarification

texts: I was studying diodes. I was at the part where we talk about P-N junctions diodes. There is a part I am confused about. Is the "junction" part the part in the middle which blocks the current if no voltage is applied? Or is the "junction" part the entire diode, or each of the sections that have P material or N material?


texts: Introduce delays of alternating value for synthesis on hardware

texts:
My question here is with reference to this question previously asked.
Currently, I am able to generate delays for each signal as desired.

Next, I want to generate different delays for alternate vsync rising edges.
Example:

If it is the first rising edge of vsync, then generate delay equal to 4 clock cycles on output (i.e., vsync_o).
If it is the second rising edge of vsync, then generate delay equal to 2 clk cycles on output (i.e., vsync_o).

So the delays I want on the output should alternate between 4 clock cycles and 2 clock cycles.

I am not able to figure out how to do this. I am currently initializing a counter which does not reset (so I can compute the number of vsync pulses).....but this will ultimately saturate. Is there a better method or am I missing something?

I have written the following code. Will this lead to any problems which can be avoided otherwise?

`timescale 1ns / 1ps

module Sync_Delay( clk_27,  vsync,   hsync,
                            vsync_o, hsync_o );

 input clk_27;

 input wire vsync;
 input wire hsync;

 output reg vsync_o;
 output reg hsync_o;

 reg[20:0] v_bits;
 reg[2:0] h_bits;

 reg cnt = 0;

 always @ (posedge vsync)
 begin
     cnt = !cnt;
 end

 always @ (posedge clk_27)
    begin
    if (cnt == 0)
       begin
       vsync_o <= vsync;
       hsync_o <= hsync;
       end
    else
       begin
       vsync_o <= v_bits[20];
       v_bits <= {v_bits[19:0], vsync};
       hsync_o <= h_bits[2];
       h_bits <= {h_bits[1:0], hsync};
       end
 end
endmodule

I notice a difference in pulse width between the input and output signal, which is not desirable.


texts: Why does this unity gain transistor phase shifter not drop its amplitude with frequency?

texts:
I read about this phase shifter in "the Art of Electronics" and decided to run an LTspice simulation to verify if my understanding of the circuit is in line with reality.

According to LTspice the circuit is just below unity gain over 10Hz-100kHz band.

The dashed line shows phase. The continuous line shows amplitude, but notice the scale: Looking at µV's variation from a 1V(p) input.

My feeling however tells me R5 and C2 form a simple RC low pass filter and although fed by a symmetric input voltage tapped from the transistor's collector and emitter, I would still expect the output to drop at 6dB/oct from about 200Hz.

AC analysis:

As C2 current increases with frequency, the voltage across R5 increases.
Similarly the voltage across C2 decreases.
Amplitude fed into the R5/C2 at collector and emitter is flat with frequency.

What am I overlooking here, why is the output gain for higher frequencies still about unity? I am looking for a qualitative answer.

Version 4
SHEET 1 892 680
WIRE 288 16 112 16
WIRE 832 16 288 16
WIRE 112 48 112 16
WIRE 288 48 288 16
WIRE 832 48 832 16
WIRE 288 144 288 128
WIRE 400 144 288 144
WIRE 512 144 480 144
WIRE 288 160 288 144
WIRE -16 208 -208 208
WIRE 112 208 112 128
WIRE 112 208 48 208
WIRE 224 208 112 208
WIRE 512 208 512 144
WIRE 528 208 512 208
WIRE 608 208 608 80
WIRE 608 208 592 208
WIRE 640 208 608 208
WIRE 752 208 720 208
WIRE 832 208 832 128
WIRE 832 208 752 208
WIRE -208 240 -208 208
WIRE 752 240 752 208
WIRE 288 272 288 256
WIRE 400 272 288 272
WIRE 512 272 512 208
WIRE 512 272 464 272
WIRE 112 288 112 208
WIRE 288 288 288 272
WIRE 832 288 832 208
WIRE -208 352 -208 320
WIRE 112 400 112 368
WIRE 288 400 288 368
WIRE 288 400 112 400
WIRE 832 400 832 368
WIRE 832 400 288 400
FLAG 752 240 0
FLAG -208 352 0
FLAG 608 80 out
SYMBOL res 96 32 R0
SYMATTR InstName R1
SYMATTR Value 62k
SYMBOL res 96 272 R0
SYMATTR InstName R2
SYMATTR Value 22k
SYMBOL res 272 32 R0
SYMATTR InstName R3
SYMATTR Value 2k203742
SYMBOL res 272 272 R0
SYMATTR InstName R4
SYMATTR Value 2k2
SYMBOL res 384 160 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R5
SYMATTR Value 8k
SYMBOL cap -16 224 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C1
SYMATTR Value 10m
SYMBOL npn 224 160 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL voltage 832 272 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL voltage 832 32 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL voltage -208 224 R0
WINDOW 123 24 124 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value SINE(0 1 20000)
SYMATTR Value2 AC 1 0
SYMBOL cap 528 224 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C3
SYMATTR Value 10�
SYMBOL res 624 224 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R6
SYMATTR Value 10meg
SYMBOL cap 400 288 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C2
SYMATTR Value 0.1�
TEXT -242 410 Left 2 !.tran 0 0.2 0.1
TEXT -248 448 Left 2 !;ac dec 50 10 100000


texts:
I know that this question is math related, but I still don't get why we can say the following formula holds:

I've a voltage \$V:\left[0,\infty\right]\to\mathbb{R}\$ and \$V\$ is periodic with \$T\$. Why can we say that the average voltage obays the following formula:
$$\overline{V}=\lim_{n\to\infty}\frac{1}{n}\int_0^nV(t)dt=\frac{1}{T}\int_0^TV(t)dt$$


texts: Are both electrons and holes responsible for conductivity in an extrinsic semiconductor (both n-type and p-type)?

texts: In a semiconductor, the drift velocity Vd and E(electric field intensity) are directly proportional to each other.. with the proportionality constant as mobility of charge carriers.. in the formula I studied in the textbook they substituted this mobility as the sum of the products of the concentration of the holes with their mobility and electrons with their mobility..so the doubt..


texts: What to look for when buying USB A/B/mini/micro to USB C adapters?

texts:
For personal use, I'm putting together a kind of "computer emergency" kit with cables, tools, usb keyboard, small monitor, etc. To keep the kit small, I'm trying to avoid having to get every possible combination of USB converter cable by buying only a subset of cables and getting plug adapters to fill out the rest of the possibilities. By "adapter", I mean these kinds of things:

We can assume power delivery is not a concern; my goal is to connect devices (e.g., disk drives, other peripherals) temporarily to Mac and Windows computers when investigating hardware problems. Example scenario: connect an (old) external hard drive enclosure having a USB 3.0 type B female port to a Mac laptop having a USB C female port, without having a dedicated USB 3.0 type B male to USB C cable on hand.  (One approach for that scenario is a cable that has USB 3.0 type B male on one end, USB 3.0 type A on the other end, plugged into an adapter that has a USB 3.0 type A female on one end and a USB C male on the other end. Other combinations would work too.)
Being a nonexpert in this area, it is not clear to me which combinations of adapters and cables can work, given that some USB standards have differences in things like host versus device side. If my goal is to have a way to connect any of the following to any other, what should I look for, in terms of the properties of the connectors and cables, and the combinations that are feasible?

USB type A female
USB 3.0 type A female
USB type A male
USB 3.0 type A male
USB type B male
USB 3.0 type B male
USB 3.1 type C female
USB 3.1 type C male
USB mini A
USB mini B
USB micro B
USB micro B super speed

An example of the minimum I can imagine is to have a single cable that has USB C on both ends, and then get two copies of small plug adapters each having USB C female on one end and every possible other type on the other end.  (So, the arrangement would be T1-cable-T2, where T1 is one adapter and T2 is another adapter.) However, it's not obvious to me whether there are combinations that can't work, and whether there are differences in the design or wiring of the adapters that need to be taken into account.


texts:
I'm hacking a pair of active-shutter 3D glasses. Leading to each lens is a flex PCB with 2 traces. I'd like to connect into those traces about 5 mm away from the lenses. How can I go about making a connection into them?

melt the flex PCB to leave just the bare copper?
somehow crimp metal teeth into the flex PCB from both sides?


texts: Does a RF frequency multiplier work with ultrashort pulse?

texts:
The question is, does a RF frequency multiplier work with ultrashort pulses?

In another words, does the frequency multiplier change the pulse width of input signal?

For example, suppose we have a analog signal oscillating at 100MHz and it was amplitude modulated to be a 50ns-width Gaussian-shape single pulse (note, there was only 5 periods of signal).

Will the output signal of frequency doubler/tripler be a 200MHz/300MHz gaussian pulse? What is the pulse width?
What if the signal was amplitude modulated to be 50ns-width square shape pulse?

【update】 To be more specific, my signal is a frequency modulated analog f0=100MHz pulse with pulse width of ~10μs, where the frequency modulation \$\delta f=\delta f(t)\$ is a function of time during the pulse width.

For example, \$\delta f\$ is about 1MHz at t<5μs, and \$\delta f\$ jumps right away to be ~10MHz at t=5μs, then at t=8μs, \$\delta f\$ jumps to ~15MHz.

I want to extract the frequency jumping curve \$\delta f(t)\$with high time resolution (say, at least with 100ns resolution), but as you can see, the oscillation duration is very short (a few cycles). A short time Fourier transform analysis can not resolve the frequency jump accurately.

So I wonder, can a frequency multiplication process enhance the frequency difference to \$N\delta f(t)\$, but also the frequency jumping curve shape is not changed?  Then the core question is, will a frequency multiplier work with short signals with few cycles?

I have read papers that uses frequency multipliers to generate wideband linear frequency modulation (LFM,\$\delta f=\alpha t\$) pulse signal from a narrow band linear frequency modulated signal . I'm not familiar with electronics, but I guess a frequency multiplier will also work on a nonlinear frequency modulated signal? Am I right?


texts: Why MCP 3402 ADC doesn't display the correct value

texts:
I am using the MCP3204 ADC with my Arduino. The chip is powered by 5V from my LM338 PSU. Since I don't have a proper reference at hand, I use the supply voltage as Vref as well. When I give it 5V, it shows 4093 which is full deflection of 12 bit ADC. I voltage divided it down to 2.5V with two 10k's then it's 1757. I checked with my DMM and it's 2.513... huh? I suck at math but am sure that's not 1/2 of 4093.

original code in C from tutorial http://extremeelectronics.co.in/avr-tutorials/interfacing-12-bit-spi-adc-mcp3204-with-avr-micro/

uint16_t ReadADCEx(uint8_t ch) {    uint8_t byte,data_high,data_low;

   byte=0b00000110;

   if(ch>3)
      byte|=0b00000001;

   CS_LOW();

   SPIWrite(byte);

   byte=ch<<6;

   data_high=SPIWrite(byte);

   data_high&=0b00001111;

   data_low=SPIWrite(0xFF);

   CS_HIGH();

   return ((data_high<<8)|data_low); }

My arduino eqivulent

#include<SPI.h>
const int ssPIN = 10;
void setup() {
  // put your setup code here, to run once:
  pinMode(ssPIN,OUTPUT);
  SPI.begin();
  Serial.begin(9600);
}
uint16_t ReadADCValue(uint8_t ch)
{
    uint8_t value,data_high,data_low;

  //active MCP3204
  digitalWrite(ssPIN,LOW);
  value = 0b00000110;
  SPI.transfer(value);
  value= 1 << 6;
  data_high=SPI.transfer(value);
  data_low=SPI.transfer(0xFF);
  digitalWrite(ssPIN,HIGH);
   return ((data_high<<8)|data_low);
}

void loop() {
Serial.println(ReadADCValue(1));
delay(1000);
}


texts: controller area network protocol, where does the software live?

texts: The CAN protocol lives between the phy layer and the data link layer. It is a wired network protocol connecting electrical entities to allow communication. What I wonder is where each node is connected by wire, does software live in each node such that they are able to identify the correct control structure being sent? It has to recognize the start bit and the control and data field, crc. Where is does this live in each node and if anyone had an example of it that would be appreciated.


texts:
I am considering designs for a minimalist game system based on a PIC18F85J5. Part of my design is that games can be loaded from an SD card without reprogramming the chip or flashing the program memory. I chose that chip because it has an external memory interface that will allow me to run code from an external SRAM.

The basic idea is that the internal program memory will contain an interface for browsing the sd card, and once the user selects a program it will copy a hex file from the sd card to the external ram, and then jump execution into the external ram space.

The internal program memory will also have various libraries for graphics, controller input and other various utilities.

I am fairly confident I know how to make the internal firmware parts work fine. The problem is creating programs to run from the external RAM. It doesn't feel the same as targeting a regular pic, and it needs to be aware of the library functions that are available in the internal memory, but not recompile them, only link to them. It also needs to start using addresses just after the 32k of internal flash, not at zero. Is there a good way to compile a program using these types of constraints?

I am using the MPLab IDE, but I am not super familiar with it, or how to do this kind of customization.


texts: What sort of connection is used on this car remote antenna?

texts:
I'm having issues with my car remote and looking at the antenna it looks like the wires were glued into the connection. I'd like to strip and replace this but I'm not sure what sort of connector to look for online/in stores to replace it.

This is almost identical to what I'm working with

When looking for the blue connector is this image what should I search for?


texts: Source transformation of two current sources not in parallel

texts:
Is

      A  B
   |‾‾|  |‾‾|
i1 ↑  R1 R2 ↓ i2
   |__|__|__|
       D

equivalent to:

       R1 A B R2
     |‾  ‾° °‾  ‾|
i1R1 ±           ∓ i2R2
     |___________|
           D

as seen from across the two resistors (A-D and B-D)?

PS: I wish we had a quick way to insert pretty circuit diagrams here.


texts: MOSFETs leaks current between two water sensors

texts:
Goal:
I've got a set of EC and pH water sensors that need to sit in the same batch of water / capture values real-time for a Arduino project.
However my sensors cancel each other out when both are submerged cause it's creating a circuit in said water. So I've been trying to utilize these MOSFETs (JEDEC TO-220AB - RFP30N06LEs) to turn power on and off (sequentially) between both sensors and capture their values.
Issue
As a test, I've setup two MOSFETs (one for positive, one for ground lines of sensor) and have turned off one sensor, while leaving the other sensor turned on. However even though one sensor is off, I'm still getting a circuit between sensors while both are submerged. If I remove the ground and positive from said MOSFETs, indeed the circuit in the water goes away and my on sensor begins reading correctly.
As results of the above test, I think its safe to assume there is a small current leak from the MOSFETs that is only really apparent when measuring a highly conductive medium such as water.
I've created a video to outline the issue a little quicker:
MOSFET help video question!
Question
Does anyone have any advice on the best approach to completely kill a current to a sensor within in a conductive medium like water? Are MOSFETs indeed the correct way to go? Any advice would be greatly appreciated!
Thank you.


texts: How to connect the pic16f59 to a pickit 3?

texts:
I have already asked a question on this forum on how to get an LED light up using a pic16f59 with pickit 3 (The post can be found here). Some people have pointed out that it must be a problem connected a pickit on my pic. I wonder how to do this. As for now, I am using the pickit 3 and I am connecting the PIC as follow:

     pickit 3          PIC
   -----------        -----
          1            14
          2            35
          3            5
          4            13
          5            12

Also, I am connecting the VDD (pin 15 and 35) to 5V, VPP to 12V and I have also added a bypassing 1microfarad capacitor on VDD. I also connected all  VSS to ground. Please refer to the PIC16F59 pinout below.

I wonder what I am doing wrong? Should I add more capacitors? I am using the right capacitor (1 micro-farad) in the first place? Please someone help. I have been doing this for more than two days with no success.


texts: FFC Flex PCB Flat Connector for Raspberry Pi 3 B+

texts:
I have bought a barcode scanner online (promised to be specific for Raspberry Pi 3 with USB interface) but its cable does not have any connector and is just a flat cable with numbers as AWM 20624 VW-1 80c 60v.

I am not that much familiar with electrical modules and more a programmer and do not know what type of connector I need to connect it to the camera port of Raspberry Pi.

The cable itself has 12 pins as I can count where the port on Raspberry Pi seems to have 22 pins. If I get a connector like this is there an adapter/converter for it.

Or am I going totally wrong and it should not be connected to camera port?


texts:
I'm designing a metal line in integrated cicruit which will be connected to AC voltage source in one end and transistor load in the other end. How can i calculate the inductance of the metal line (6 um lengh)?
i found this equetion L = o.2 * l * (ln(2*l/w+t) + 0.223(w+t)/l + 0.5) and in another place the ther is the same equetion but insted of 0.2 * l in the begining, it is u*l/2*pi so i'm very confused.


texts: AD9850 and other DDSs: How to stabilize output gain after low pass filtering?

texts:
Recently I got familiar with DDS family of ICs. They are fine and nice to work with but there is a problem with them:
The output made by DAC has harmonics that according to the datasheet they need to be filtered by a low pass filter.
That's not a complicated procedure but I need a very very stable output amplitude for a medical device. As anyone knows by filtering, the output drops by -20dB/decade. It can be managed by setting the threshold frequency higher but has the drawback of harmonic remnants.
My question: Is there any way to stabilize the output amplitude? (by the IC itself or additional output components as an amplifier)?
The output before filtering is like this:


texts: The circuit below shows a three phase rectifier with 3 filter inductors at the input side, and a capacitor, a MOV, and fuse at the output side. I wonder what the differences are in protecting the AC side vs the DC side. I've seen designs where they use 3 fuses, 3 MOVs at the input side. This seems like an increase in cost if we compare it to using just one fuse and one MOV at the DC side. I've also seen the use of TVS diode after the bridge. What would the best approach be?


texts: What is the quickest way to read an analogue signal - Arduino / Raspberry Pi + ADC / Arduino + ADC?

texts:
I need to sample 50Hz voltage signals from four CT current sensors and compare the waveforms to a voltage signal from the mains (stepped-down and offset for ADC) to accurately measure power consumption of four devices.

I would like to get at least 360 samples for each waveform per period, meaning 1800 total samples per second. Since the signal frequency is 50Hz, this means a reading speed of 90kHz.

I have an MCP3008 10-bit ADC available which uses an SPI interface, an Arduino Uno board, and a Raspberry Pi 2.

The MCP3008 has a max sampling rate of 200ksps (datasheet).

The Arduino Uno analogue input pins can be read at 10kHz (official docs).

The Raspberry Pi can work with SPI interfaces at 20kHz using the standard Linux driver, as mentioned here, although by bypassing the standard Linux driver it can supposedly work faster (I don't know how much faster - there are a lot of different numbers being thrown around online).

The Arduino Uno can work with SPI interfaces at much higher speeds than the Raspberry Pi.

From what I can gather, there are three setups to choose from:

Reading the 5 values directly using analogueRead() of the Arduino (clearly won't work)
Using the MCP3008 ADC with the Raspberry Pi (is it possible to make it fast enough with some modifications?)
Using the MCP3008 ADC with the Arduino

Can the required speed be achieved using any of the above-mentioned setups? If not, what would likely be the maximum speed that can be achieved?


texts: Is it possible to increase voltage from a power supply without incuring great current lose

texts:
I have a 24V 4.5 amp(108 Watt) power supply.  I know most Voltage regulators take a higher voltage and regulate it to a lower voltage.

Is there a way to increase the voltage of the 24V 4.5 amp(108) power supply to 36V(3 amp) or 48V(2.25 amp) while still allowing the same amount of power output(108 watts)?

Can you boost the voltage up and then put a voltage regulator on it?


texts: Power consumption of processor: Cubic in MIPS or linear in CPU utilisation?

texts:
I have came across two types of formulas for calculating the power consumption of a server. In the following I describe my understanding (please correct if necessary):

Cubic in Million Instructions Per Second (MIPS): If DVFS is allowed, the following formula is typically given in the literature:

\$P =c\cdot V^2 \cdot f + P_S\$,

where \$f\$ is the frequency, \$V\$ the supply voltage, \$c\$ a constant and \$P_S\$ the static power dissipation. As the frequency is usually proportionate to the supply voltage and as the frequency is measured in MILP, we obtain a cubic power function in terms of MIPS:

\$P =c'\cdot V^3 + P_S.\$

Reference:

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=888701
Linear in CPU utilization: The power consumption of a server is given by

\$P = P_{min} + (P_{max} - P_{min})\cdot U,\$

where \$U\$ is the current CPU utilization and \$P_{min}\$ respectively \$P_{min}\$ are the power consumption when the system is idle respectively fully utilized.

Reference (there are many others):

http://ac.els-cdn.com/S0167739X11000689/1-s2.0-S0167739X11000689-main.pdf?_tid=8ae17a14-1ade-11e7-88b2-00000aab0f02&acdnat=1491493057_b9f8eba8eaf9a6d26839b957c51a63dc

My questions:

Is my understanding correct?
According to my understanding, the higher the MIPS the higher the CPU utilization is (is this relationship linear?). How do the cubic and the linear formulas fit together then? For me it is contradicting that I have a linear as well as a cubic function for calculating the power consumption.
My conjecture: The cubic formula applies for servers that enable DVFS whereas the linear formula applies for servers that do not enable DVFS, i.e. with a fixed frequency. Can someone confirm/disprove my conjecture with a reference?

I really need to understand this issue and I also really need references for my research.


texts: I have a problem concerning GPS units. I have been studying on a project for a weather balloon which will go about 30 - 40km up. Now I do know that some GPS units have a limit on how high they can receive/show you the location whether it is a limitation made by the military to stop random production of cruise missiles and others which just don't work above a certain height. This is a problem as my weather balloon does go to a height which could be considered as a "GPS fail zone". At the moment I am using a 50 Channel D2523T Helical GPS Receiver - http://www.sparkfun.com/products/9566 . It’s a great product but I am worried with problems with height etc. Could anyone give me some ideas on GPS units or give me advice....Any help is greatly appreciated....P.S - The unit has to have the standerd GGA protocol.


texts:
There are many articles on the internet about life expectancy of switching power supplies, but most of them have discussed about the situations that the PSU is at near full load. I'm designing an electronic device that needs a standby state, I'm using a COTS PSU with an output of 24V-5A, something like this:

My device power consumption is nearly like this:

5% of times at near full load.

55% of time at 20% of full load.

40% of time at standby (about 1% of full load).

I know that everything is depend on the quality of PSU and it's design specs, but Chinese suppliers doesn't provide enough and reliable information about their products. Although we are buying them from a sort of responsible supplier.

Can I generally expect of 10 years life of my PSU?

Someone says that the inputs capacitors (at high ac voltage) or the optocouplers regardless of the load consumption will destroy after some years. Is it true? If yes some other electronic systems like TVs that are on ac power for many years how had solved this problem?


texts: Controlling multiple switches using voltage

texts:
I want to use my laptop with the lid closed and be able to press its function buttons (including power on/off), i.e. shorting their pins, using a wired "remote control" with the same amount of buttons. In my case there are 6 of them and I was able to open the laptop and solder some cables to the switches' pins so I have access to them externally.
I could use 6+ wires and the necessary switches, but that's precisely what I'm avoiding. I can house a small circuit next to the laptop and connect it to a "remote control" with 6 switches, but I wanted to avoid using 6+ different wires at distance and having the possibility to press multiple buttons at once without causing issues.
I wanted to know if there's any way of controlling them using voltage (less wires needed, ideally 2 or 3) and some opamps and/or transistors. I though of something like a voltage ladder on the remote and have an Arduino and its ADC doing the control, shorting the pins on the laptop, but I was looking for something more "discrete". Any ideas?


texts: Difference between a DC SSR (solid state relay) and AC SSR

texts:
I am trying to understand the difference between a DC and AC solid state relay. For electromechanical relays, I notice that they are often rated for some VAC load and a smaller DC load. Solid state relays, however, seem to be rated only for VAC or DC.
What would happen if one accidentally applied a DC load to a VAC solid state relay and vice versa?
Can one convert between each type with the addition of simple components (e.g. diodes, optocouplers, etc.)?
If I have a completely unmarked relay, how can I determine if it is for VAC or DC loads, preferably using a multimeter or similar device?.


texts: Substituting resistors with capacitors in an AC mains circuit

texts:
I have 2-gang touch wall switches that I want to make Wi-Fi-controlled. I'm intending to use Wi-Fi-enabled relays connected to the switches so that the switch outputs are connected to the relay switch inputs.
The problem is that the switches do not use the neutral line and leak current through the load in order to power themselves. This means that I cannot simply connect these two kinds of devices as described above and I somehow need to allow for constant current flow through the switches.
For now, I installed 5W 47kΩ ceramic resistors and everything seems to work as expected, but the resistors waste a lot of power and heat up to 75°C:

(The 2W connection is for 2-way communication between the switches and only one of them actually drives the lights.)
I'm thinking about replacing them with metallized polyester film capacitors, as illustrated below:

I tested a range of resistances and found out that the maximum resistance for the switches to work properly is around 47kΩ. I was thinking about using 100nF capacitors rated for 630V, such as these jb 2J 104K ones, which should provide around 31.8kΩ capacitive impedance at 230V 50Hz.
Am I reasoning correctly and is it safe to use these capacitors in my case? Note that they would be under constant operation. Also, I'm not sure if the phase shift introduced by the capacitors would be an issue here.


texts:
I'm currently trying to develop a circuit to eventually transfer to a pcb and I'm seriously stuck constructing it, this is my problem:

The circuit needs to rotate an 8 segment circle so that once a day the circuit will rotate into a new segment.
Then also once the circuit has run 8 times passing through all segments I want a button that will reset the program so that it will run the next 8 segments.
I want to also be able to develop this to be a pcb as I want to 3D print a case for the device hence I need it to be portable and battery powered.

PS I’ve had numerous people tell me that this task is simple but no one can develop a circuit with me.
edit: The picture I have described is shown below and I only want to create PCBs because I have a few animals that I use to feed them and handmade circuits just make the place look awful. So I want to create battery powered device. I’m a 3rd year electrical engineer but sadly they only teach us theory and not how to create things ourselves :(. I understand what I need to do im just more so asking what parts anyone would recommend im currently looking at using an A4988 and some micro controller with a crystal.
For more detail: the mass of the object that is being rotated is around 50g and im using this stepper motor: https://au.element14.com/nanotec/sp2575m0206-a/stepper-motor-7-5deg-1-6n-cm/dp/4743209


texts: Damaged 3 IP Cameras with replacement power supply

texts:
I have damaged 3 Edimax PTZ cameras because of a replacement power supply.  I am trying to figure out why the replacement power supply with DC output of 12V 2A would kill my cameras which operated from 12V 1A DC.

I have measured the actual output voltage from the original and replacement at 13.56 VDC and 12.04 VDC respectivly.  I,ve never encountered a situation where such a small difference in power supply specs could cause this type of damage.  Both supplys are rated at 12V. The original at 1A and the replacement at 2A.

I'd like to eventually repair my cameras and hope understanding possible causes of the damage may lead me to the damaged circuit board component(s).  I've already replace 3 Schottky Diodes on the board but no joy.  I don't see any physical evidence of burn out on the boards.

Sorry to go so long on my question but I'm totally mystified by this issue.


texts: How to determine the end of data received by USART?

texts:
I am receiving some strings from UART in AVR. Strings are chaotic, not deterministic. It also includes new line \n and carriage return \r characters that's why I couldn't find a solution including checking bytes if they are \n or \r.

So is there a way to determine the end of the data?

EDIT: For more details about the data I receive.
I am acquiring some strings from my web server and they are commands to be used such as "weather+check\r\n". Another one is, for example, "time\r\nNew York+Check\r\n\r\". I simply want to get these strings and assign to a char array. But to do this I need to know when data ends so that I can go out of the While loop that I use to fill the array.


texts: Relay or switch that can remotely power OFF and automatically power ON

texts:
Quest: I am looking for a remote Wifi-enabled switch or relay that switches 120 volt household power OFF via some type of remote Wifi connection, then back ON automatically by itself after 5 minutes or some preset delay. Any suggestions for a specific product or solution?
Explanation:
The Situation: I have a country cottage with a WiFi modem and router and several other devices connected for various home automation functions including cable modem, router, security lights, appliance switches, heat, bridges, security cameras, Logitech Harmony remote for TV and Sonos music and more. Normally, it all works very well, even remotely when I am away from the cottage using apps on my iPhone and Siri for some functions. Everything is powered and connected via one single wall outlet plug (15 amp circuit, 120 volts) and, from there, several other power bars with GFCI-type circuit breakers etc. And, FYI, I cannot get around using this one single plug at the start of the power sources, it's a small cottage but I do not think that by itself is a problem.
The Problem: The problem is that, sometimes, when I am away, a couple of these components lose their WiFi connection randomly (for some mysterious reason) and the simplest solution is to perform a whole system a "reset" to make everything work properly again. Please see "Additional Info below" for a more detailed explanation. I do not know why this happens exactly but it only happens, on average, say once a month at randomly different times but the solution is simple.
The Solution: The usual solution for any problem with my system is to simultaneously unplug the power to all the components, including the modem, wait 5 minutes for internet and other signals to power down completely, then restart everything all together so that a complete reboot of all the components automatically re-establishes all the required connections and everything starts to function normally again after a few more minutes.  I do not know the reason why a few of my components drop their signal but that is not my question here.
Query: I would like to reboot my system remotely when I am away from the cottage.  The problem with rebooting could be addressed by having a remotely enabled relay or switch (with appropriate amp and watt capability, so, not a light switch) which would be at the front end of the power supply to my system's source of 15 ampere, 120 volt power, i.e. a dedicated household wall power outlet. However, if I just disconnect the power remotely, I cannot remotely power it back ON since the modem and router would have no power.
Additional Info: The modem needs to be rebooted for this solution to work; rebooting of everything other than the modem (or the router) won't properly reset the system. However, interestingly enough, I don't think the modem or router is faulty (or their settings), it's some of the component bridges that sometimes fail and seem to be the problem, but a modem and router reset along with a reset of everything else, does fix the problem. More specifically, just for a complete understanding as I see it, the problem seems to have something to do with the interaction of the Harmony Remote bridge, the Lutron Casseta bridge and the Nest Thermostat WiFi connectivity.
That is why I am looking for a switch or relay that can power back on after a delay of 5 minutes or more. Any help or advice would be appreciated but please keep in mind that in this discussion I am really just looking for an appropriate switch or relay.


texts: What are the advantages of having USB part of the microcontroller (as the Leonardo does)?

texts:
The new(ish) Arduino Leonardo has an ATmega32u4 microcontroller which is different from the Uno. This controller has built in USB functionality and it can interface with a PC as a HID which is different than any of the other Arduino boards.

What are the other advantages to using the ATmega32u4 chip instead of the ATmega328 which requited a USB-UART chip to program and had limited USB capabilities?


texts: Calculation of ripple voltage after rectifier (equation from TAOE)

texts:
I am reading The Art of Electronics, Third Edition by Paul Horowitz and Winfield Hill but I feel like I am missing something when the book comes to talk about (begins to, instead) Power-supply filtering (Chapter 1.6.3_A, page 32) after a half/full wave rectifier with capacitor.

In the A subparagraph, here is what it is said :

  It is easy to calculate the approximate ripple voltage, particularly if it is small compared with the DC. The load causes the capacitor to discharge somewhat between cycles (or half-cycles, for full-waves rectification). If you assume that the load current stays constant (it will, for small ripple), you have :
  $$
\Delta V = \frac{I}{C}\Delta t
$$
  Just use 1/f (or 1/2f for full-wave rectification) for \$\Delta t\$ (this estimate is a bit one the safe side, because the capacitor begins charging again in less than a half-cycle). You get
  $$
\Delta V = \frac{I_{Load}}{fC}
$$
  for half-wave
  $$
\Delta V = \frac{I_{Load}}{2fC}
$$
  for full-wave

Ok, I don't understand where that comes from, more specifically the \$I_{Load}\$ term instead of \$I_{in} - I_{Load}\$ term that I found (see below). I tried to retrieve it, I don't.

Let's take the following schematic (which is used in the book):

The KCL and KVL gives respectively :
$$
I_{in} = I_C + I_{Load} = C\frac{dV_{Load}}{dt} + I_{Load}
$$
$$
V_C = V_{Load} = V
$$

The latter is quite useless in fact. So, if we work with the KCL equation :
$$
\Delta V = \frac{I_{in} - I_{Load}}{Cf}
$$
for a half-wave rectifier. And :
$$
\Delta V = \frac{I_{in} - I_{Load}}{2Cf}
$$
for a full-wave rectifier.

What am I doing wrong ? Why don't I find the same equation that the book gives ?

Thanks !


texts: How is a magnetic field generated by an inductor when supplied with a pulsed current (pulse induction)?

texts:
My question relates to pulsed induction (PI) metal detection in particular.
It is my understanding that in a DC circuit an inductor acts as a conductor with little to no energy stored in a magnetic field. You will usually see them in DC circuits to help attenuate any high frequency noise components.
With a PI metal inductor, a short pulse of current for a few µs is supplied to a coil of wire. This pulse generates a magnetic field around the coil. The magnetic field around the coil excites eddy currents on the surface of surrounding metals which in turn induces a small magnetic field around these materials also.
When the current supply is removed from the coil (e.g. the end of the pulse) the magnetic field collapses and back-EMF is generated. The length of time it takes for the back-EMF to settle is determined by the amount of surrounding metal, as it will take a short amount of time after the field around the coil collapses for the induced magnetic field around the materials to collapse and these interfere with the EMF present in the coil.
How is a magnetic field generated and maintained during a pulse around an inductor? As far as the inductor is concerned, during that time when the pulse is settled, isn't it effectively just the same as DC?
Here is a little bit more on the subject of PI if needed.


texts: building my own lc meter - multi point gnd

texts: I'm building my own lc meter using the attached schematic. What I don't understand is why there is more than one path to gnd? Does it not eventually get connected to the same point?


texts: Replacing 5 V pin with battery not working

texts:
I have a small breadboard that has a L293D motor controller and 2 DC motors. The board is hooked up to a Nordic DK and everything on the PWM side is fine. The breadboard is powered by the development board's 5 V pin but I am ready to move to the next step of a PCB so I will need a battery.

I have two 2032 coin cells that were taped together and have jumpers for positive and negative but whenever I try to use it as the power source on the breadboard it fails to work. I checked it with a multimeter and it's throwing out at least 5.6 V.

Is there something I am missing? Are lithium batteries not applicable for this? Can I still make a PCB with what I have now?


texts: Usage Of Static Electricity To Remove Dust?

texts:
If I have a fine metal mesh -- say a stainless steel mesh at 50 micron, and I'm having dust build up on it, can I use static electricity to remove the dust? I have another mesh that's 500 micron, and much easier to clean next to it. My dust passes first through the coarse mesh, and then the fine mesh.

My idea is that while the filter is that when I wanted to remove static electricity from the fine metal mesh, I could give it a strong (HVDC) negative charge, and the 500 micron mesh a strong positive charge. The dust particles would subsequently become charged and leave. -- There is air traveling between two meshes.

My question is -- how can I calculate how far apart them meshes can be, and what kind of power I need?


texts: AD5231 Digital Pot programming/ Hardware issue

texts:
I am trying to use the AD5231 Digital potentiometer in a school project. However, I am having a lot of trouble with it. It's supposed to be connected to raspberry pi (model 2 B+) and I've trying to speak to it via SPI

I was wondering if anyone can help me with this. This is the following code I am using to try and speak to the device (I'm using Python)

spi = spidev.SpiDev()
spi.open(0,0)
spi.max_speed_hz = 10000
spi.writebytes([0xC0, 0x00, 0x00])

However, no matter what I do, I am constantly reading 75kohms from terminal A to terminal B, where B is grounded and A is a NC. I'm not sure whether I should be feeding any voltage to the wiper resistance. The rest of the hardware should be set up properly as I have redone it a few times to make sure.


texts:
I'm researching a good (and simple) driver for a HV transformer, and found this very simple and elegant circuit on the web:

It uses a feedback winding to turn transistors on in an alternating pattern. I assembled it and it works very well, but later I tried to replace the bipolar transistors with mosfets, to experiment.

The result was awful, the nice sinusoidal output I get with bipolar transistors turns into a very erratic and deformed waveform when using mosfets. Current draw increased a lot, and the secondary voltage was much smaller, the efficiency dropped a lot (by 10x of times).

My question is: is it possible to use mosfets in this configuration? Is the distortion the result of badly chosen mosfets? May I need to change R1, R2 or C1 to different values to make it work with mosfets?

Or are mosfets just incompatible with this self-oscillating configuration?

UPDATE: I forgot to add that the erratic oscillation with mosfets happened only after I changed R1 and R2 placement: I connected them between the gates and GND, instead of gates to Vcc, as in the schematics. Merely replacing the bipolar transitors with mosfets in the circuit above resulted in no oscillation at all, since the gates got tied directly to Vcc, making both mosfets conducting all the time.

So, the description of erratic mosfet oscillation in the original question applies to the circuit with this modification: resistors between gates and GND.

UPDATE 2: Thanks to Andy's reply, I understood what may be obvious for the more experienced: the resistor just bias the base to conduction state, so the feedback winding can make the transistor cut on negative pulses. I have applied the same logic to the mosfet version, biasing the gate to Vgs(th) (Gate Voltage Threshold), and it works.

However, this circuit is not as efficient as one using an active oscillator and a driver, which will ensure rise and fall times are short, and the transistor (BJT or FET) will not be speding time in it's linear region.


texts: LED: should I smooth the current with a capacitor

texts:
To control the brightness of a LED often pwm is directly used as input to the LED. Does this on/off turning by the pwm has any negative effect on the live expectation of the LED?

Would it be better for the MTTF (mean time to failure) to smoothen the current by adding a capacitor?


texts: Would unstable sample rate affect spectrum after FFT?

texts: The system samples analog input and then conduct FFT on the samples and then display the spectrum. Currently, the issue is the displayed spectrum line position is keeping shift between each scan. After examining the whole system, I found all the components in the system are consistency except the sample rate which varies between 9B~10B, but it always satisfies the Nyquist sampling rate(2B). My question is whether the unstable sample rate may lead to the frequency shift?


texts: STM32L1 - How do the Cat.1 vs Cat.2 (etc.) lables relate to the part numbers?

texts: I am looking at the data sheet for the STM32L1 and I keep seeing references to Cat.1, Cat.2, ... etc. devices.  How do those categories relate to the part numbers?


texts: Can I maintain the health of the data on a NAND USB drive with a power-only USB charger?

texts:
I want to maintain some data securely (avoid bit rot) on solid state media.
I know that SLC flash is the best technology to do that with, but even SLC eventually drains.
Could I plug an SLC USB flash drive into a USB charger to maintain the bits?  Or do the bits have to be rewritten every so often to prevent them from rotting?


texts: Controlling an RGB 5050 LED strip with Arduino and potentiometers

texts:
I recently found and old amplifier with the speaker taken out of it and thought it would look nice as a light feature. The switches and potentiometers are still in place but have removed the power supply.

After finding this project from MAKE Magazine (http://makezine.com/projects/android-arduino-led-strip-lights) I was wondering instead of using an android device to control the LED strip, if I could possibly re-purpose the pots already on the amp box to control the LED's. Possibly one pot for each channel such as R G B.

Is there a way to do this? And if so, what would the code be?

Any help or tips are appreciated :)


texts: What is the purpose of a pull-up resistor in a microcontroller?

texts:
I'm reading about the AVR microcontroller. In a chapter on I/O ports I've stumbled accross a concept that I have trouble understanding: the pull-up resistor.

Here is a quote from the textbook:

  PORT register role in inputting data:

  There is a pull-up resistor for each of the AVR pins. If we put s into bits of the PORTx register, the pull-up resistors are activated. In cases in which nothing is connected to the pin or the connected devices have high impedance, the resistor pulls up the pin. See figure 4-4. If we put 0s into the bits of the PORTx register, the pull-up resistor is inactive.

And the associated diagram:

Now, bear with me; it is my understanding that we control the data direction of the ports by writing 1s or 0s in the DDRx register. So if I want to read data from a port I clear the DDRx register (0s) and get my data from the PINx register. Conversely, if I want to write data I set the DDRx register (1s) and write to the PORTx register.

Okay? So the book gives assembly-code examples of how we activate the pull-up resistors of a port. We do this by writing to the PORTx register without setting the DDRx!

What is the function or desired effect of doing this? It is not clear to me, even after having read half of the book.


texts: Convert positive square wave to positive-negative

texts:
I am looking for a way to convert a square wave coming from a microcontroller with voltage range from 0V to 5V, to a voltage range from -12V to +12V. The frequency of a square wave will vary from few Hz to few MHz.

Thanks in advance!


texts: Question about AC and DC on a RC circuit

texts:
Suppose a simple RC circuit, R and C in series with a voltage source and an open switch. The capacitor is discharged.

The power supply is AC, sinusoid with amplitude 10 V and a frequency of 50Hz.

So, the power supply is

10 Sin(100πt)

The resistor is 100Ω and the capacitor is 1F.

I turn the switch on at t=0.

What is the current at t=0.05 seconds?

As far as I see the current on the circuit is ruled by this formula:

so,

i(t) = (10 Sin(100πt)/100) e^(-0.05/100)

therefore, plugging t

i(t) = 27.05 mA

Now let use Ohm's law:

The circuit's impedance, Z is equal to

Z = R -j/wC

Z = 100 - j(2π)

Z = 100 - 2πj

so i = v/z

i = (10 Sin(100πt))/(100 -2πj)

i = 2.7/(100 -2πj)

How are these two values equal?

I was expecting to get the same values for both methods of calculation.

What am I missing?


texts: CMOS inputs on microcontrollers and other ICs can be damaged by ESD discharges. Can the gate of a big discrete MOSFET (2N7000, IRF9530, etc.) be damaged by ESD discharges?


texts: Power categories in ASIC design (Design Compiler)

texts:
I am currently working on the synthesis, with Synopsys' Design Compiler, of an AES encryption module.
In the power reports there are three power categories specified :

Switching Power
Internal Power
Leakage Power

I understand what is the Leakage Power but I can not find out the differences between Internal and Switching power.

Can anybody explain me what are the differences between these two categories?


texts:
I'm making a little project purely as a hobby using a small FPGA breakout board.
I'm outputting VGA video which works fine, but would like HDMI output instead so I can connect to a television that has that input but no VGA.

I don't believe it's practical to generate HDMI directly from my FPGA board (correct me if I'm wrong...) so I was wondering if there was any encoder chip or board that doesn't cost too much that I could use in the project that takes VGA input (and possibly audio) and outputs a HDMI signal. I've not been able to find anything myself.

Any ideas? Or is this impractical and I should settle for analog video instead.

EDIT: Basically I'm asking if there is any way to generate HDMI that's possible for a small personal FPGA project, the VGA part isn't necessary if there is another way.


texts:
I am trying to drive AD9850 (DDS). First I started with a module , programmed the micro (ATMega128 ) and everything was ok ( It means there may not be a software error). Then I decided to make my own PCB (because the module has inbuilt low pass filter and I wanted to design my own filter) . I designed a schematic according to the datasheet of the IC and Module.

Now it works fine just for a few minutes. As I turn it on, it takes the commands well and makes the output signal correctly but after 4-5 minutes it dies forever! ( I mean after a restart it does not work also )  I thought about overvoltage or something therefore added overvoltage protection circuit ( 3 zener diodes ) and carefully checked all voltages.

I also electrically tested all connections down to IC pins and all are OK. When I put my oscope probe on the output pin of the Crystal oscillator, I can see a 100MHz signal ( the nominal signal of it).

Finally decided to make another PCB.  The new device went the same: worked well just for a few minutes.Has anyone experience on this specific device that can help me on this issue? What is the main cause of damage to the device ?

I also should note that I followed ESD protection guidelines ( wearing antistatic gloves and putting wire on my arm and connecting it to the ground. All clothes from pure cotton.) but I dont know what is destroying my devices.
  Here is the schematic:

and the PCB: (Please note that all DRC errors in the designed corrected later and tested electrically ).


texts: Using european telephone cables for own DC power delivery

texts:
I have european telephone cables running through my walls to each room, without any connection/socket. Well... we really do not need any hard line telephone connection and I am into DIY projects, so I want to make use of these cables. I thought I could use these lines to deliver DC power to my Raspberry Pis and Arduinos around the house (sensors and stuff). But I really do not know how much voltage and current I can allow through these cables. One other possibility is to use them for speakers around the house (music or communication). Again speakers will need audio and power and I want to avoid switching cables as much as possible.
PoE is an option I am considering, which is known/established but expansive with switches/injectors and splitters with 3+ devices.

I was wondering, if I can use existing phone cables for power (from a main AC to DC (48V?) converter, NOT from phone company of course)? Are there any standards for cable resistance/thickness and allowed potential and current?


texts:
After a bit of advice as reading a datasheet on the DM631, this is a 16 channel constant current LED driver, datasheet can be found here http://www.siti.com.tw/product/spec/LED/DM631.pdf

Now the DM631 uses a supply of 3.3V to 5V and it states on the datasheet "DM631 is a 16-channel constant current sink LED driver"

The datasheet also states "Maximum output voltage: 17V"

Basically my application requires 12V being supplied to an RGB LED strip.

As I understand it the outputs on the DM631 (which are kind of inputs as they sink current) will be happy as long as the 17V maximum voltage and maximum current rating is not exceeded?

Best regards,

Ant


texts: Power input connector for power distribution board

texts: I have been looking at several different power distribution module designs and the all seems to use a large bolt for the main power input. I am curious what these connectors are called and how they connect to the PCB internally?


texts: Do I need a heat sink for small voltage regulator?

texts: I'm using a 7808 voltage regulator in to-220 package. Vin is 12V, Vout is 8V. Expected max current should be in the range of 10mA, let's say 50mA at most. Circuit is to be encased. Do I need to add a heat sink to the 7808, or that power will dissipate correctly without?


texts:
Im basically entirely new to Electrical Engineering, however I really want to challenge myself to become a better one, so I decided to try to mod a nerf gun to be a coil gun, more or less. Now, I know physics like the back of my hand, but when it comes to wiring everything up, I am at a loss.

Right now, I need to change a trigger pull of indefinite length into a quick pulse of voltage where I could tweak the pulse length to make the gun fire consistently. I did some research and it looks like I'll essentially need to wire up a rising edge detector more or less...

Am I on the right track? And if so, how would I go about doing this physically?


texts:
Scope:
The scope of this project is to repeatably light several fireworks simultaneously (Mandalorian Whistling Birds Vambrace build). This requires that the only action required to light more firework rockets would be to load them into the device. I have looked into the ways people have done this in the past but all the options I've seen are consumable or one time use. I've built a proof of concept design and now I'd like to improve it. My initial prototype uses the nichrome ribbon I removed from a car cigarette lighter coil. I chose to start with this since it was a cheap source that uses 12V. The fuses of the fireworks rest on the coil and as I apply 12V to the coil it heats up and they ignite.

The issue I am facing is that the coil takes awhile to heat up (no calculations in first design for efficiency) so I would like to design one that heats up faster and has more surface area coverage. I would still like to use my 12V LiPo battery. I can do the equations to figure out voltage, length of wire, amps, and produced heat but what I'm having trouble with is figuring out how to suspend the coil, ensure it maintains its shape, and doesn't short to the metal chamber it's nested in. I plan to use 28-30 gage nichrome wire which is not very rigid. I'm also dealing with a small space of less than a 2" diameter tube. Any ideas?

Thank you in advance for any suggestions you may have.

Edit: Thanks everyone who answered and provided suggestions! From your responses I have learned that mica, alumina ceramic, or other ceramic compositions will work well as an insulating material. Also, the use of thin stainless steel sheet may work well as the heated element for ignition.


texts:
I'm working on a large scale LED project and I have a power supply question.

I am using multiple power supply units and I'd like to wire a large amount of strips in parallel and control them with a Teensy 3.1.  From what I understand, while the positive wires for each strip should be connected to the power supply unit, the strips must be all be connected via negative wires (in addition to the data wires). Something like this:

Ref: http://www.eerkmans.nl/wp-content/uploads/2016/02/neopixel_power_cheatsheet_v2.png

The total amperage will be large (+50 amps).  However, each strip will draw only about 4.8 amps.  With regard to wiring the negative terminals of all of the LEDs together, what gauge of wire am I looking for?  Must I use wires that are capable of handling the full 50+ amps?  Is it fine to use a wire size that can handle the load just for each strip?

Any help would be greatly appreciated!


texts: Why does an antenna sometimes has a bending on the end of the wire?

texts:
I sometimes see antennas as follows ( Paint ;) ):

It sometimes is even in manufactured wires. This gives the clue that there is a scientific explanation for this bending. I have searched on the internet, but could not really find a good answer on it. Can somebody please explain to me if this is true and has a function or has no impact or maybe is worse for the signal.


texts: Industrial IO board ST X-NUCLEO-PLC01A1 - design features

texts:
For a project I want to buy an X-NUCLEO-PLC01A1.
So I studied the schematic and datasheets (CLT01-38SQ7)(VNI8200XP), but there are still some points that confuse me.

What is the purpose of D20 - is it a reverse polarity protection? If so, why is it in the GND path?

Why is the supply voltage of CLT01 (VC) connected to 24V through a 2k2 resistor?

What's the function of the "surge test" area with the 2 x 4n7F capacitors? Are the capacitors implemented to the PCB, because it looks like they have no footprint.

Suppose I want to use this in an industrial commercial product. Would these IO be of the same ruggedness as in a commercial PLC? If not, what would be missing?


texts: How can I fix the problem of floating nodes in Pspice?

texts:
I have so many errors saying there is floating nodes in my circuit, I used a grounded big resistance in some nodes to fix them but there are so many floating nodes errors yet, my circuit is very large and I wish you could see the nodes...
enter image description here


texts: Can lightning strike into the phone line damage electronics in the house through the ADSL modem?

texts:
I was always wondering about the following:
If lightning strikes directly into the phone line outdoors, can the excess power coming from the phone line jump over the switching power supply of the ADSL modem into the mains in the house and damage any computers / TVs / washing machines?
Let's assume that the ADSL modem is WiFi only and that there are no cables connected to it except for the phone line and mains.


texts: Avoiding accidental earthing, voltage rejection, and voltage dividers for a motor control output circuit

texts:
I'm trying to connect up an integrated control DC motor with a 24V output (Motor manual - relevant page p32) with my 10V PLC (PLC Manual), and looking for a little help please.

I don't understand why the motor controller output in pic 1 is after R4 - even if my plc was 24V, surely in this position it will be getting a 0V signal? Anyway to connect my 10V PLC through a voltage divider which of my proposed circuits below that is correct, if either?
Also the manual states 'The accidental earthing of the outputs or connecting them to a capacitive load will result in them being destroyed.' Does this just mean connecting them directly to Ground without a load (e.g. a resistor) in between? i.e. both my circuits below would be OK?

Many thanks for your help!

Oli

THE CIRCUIT GIVEN IN THE MANUAL

MY PROPOSED CIRCUIT 1

MY PROPOSED CIRCUIT 2


texts: How to amplify the resistance of LDR between 500-900 Ohms for use as Arduino input (0-5V)

texts:
I have a LDR which I want to use for measuring the light level between two intensities, which are a pretty small part of its full range.

Basically the LDR ranges from about 300ohms to 2.5Mohms measured on DVM, but I am really only interested in its output between 500-800ohms. So I'd like to squash values below 500 to 0v, and set that to 5v when the R is above 800 ohms.

The basic circuit only gives about 0.1 of a volt difference over the resistances I am interested in. I can change the value of the R1 resistor to 600ohms, and get about 1V of difference, but I'd still like to use the whole range of the Arduino adc 12bits;

simulate this circuit – Schematic created using CircuitLab

I am currently using an arduino to read the voltage level between 0-5v. I presume I am looking for some sort of wheatstone bridge, or voltage divider  and op-amp set-up.

simulate this circuit


texts: Half bridge galvonic gate drive with deadtime

texts:
I'm a Tesla enthusiast and build Tesla coils now and then. One thing I have always wondered, a lot of designs (some very popular) utilize a transformer to drive a N-MOS half bridge (see image below). My concern with this, and simulations have shown it to be true, shouldn't this type of a design result in a high amount of shoot though since there is no dead time incorporated?

With that being said, I would love to get away from bootstrapping my driver and forcing it to be sitting on the high voltage rails (debugging and inspection with a scope gets much easier). My problem is I do not see an easy way to incorporate dead time.

The only method I see to add dead time and have galvanic gate drives would be to use a full bridge driver to sink and source current to two independent drive transformers and hackishly bypassing the bootstrap drive tying it to vcc.

So my questions are:

Do you agree with my assessment that for switching at 200khz, the design illustrated should have the bulk of its power losses due to shoot though?
Does anyone see a way with to easily employ dead time with galvanic isolation without using a full bridge driver as explained above?


texts:
I am currently studying "Principles of Power System by V. K. Mehta". I am stuck at a tutorial problem from chapter 13, which is as follows:

  A 2-wire d.c. distributor, 500 m long is fed at one of its ends. The cross-sectional area of each conductor is 3·4 cm² and the resistivity of copper is 1·7 μΩcm. The distributor supplies 200 A at a distance of 300m from the feeding point and 100 A at the terminus. Calculate the voltage at the feeding end if the
  voltage at the terminus is to be 230 V.

Here is my solution:


texts:
I constructed this circuit in the simulator Multisim11. It should switch current 15A trough resistor R1 for PWM regulation. I need to make it work for frequency 2kHz. The function generator XFG1 on the left top simulate output from TTL technology, which control switching power on R1. All active components are faster than 4 MHz, so it should work, but it is not working for that frequency 2kHz.

As you can see on oscilloscope there are two curves. The blue one is the signal from TTL and the red one is the voltage on resistor R1. As you can see it is switched on whole time. The blue curve have minimal effect for the red one.

I tried to set lower frequency (500Hz). Here you can see the problem. Rising edge looks good there is not any delay, but there is big delay with falling edge. It keeps switched on about 0.5ms after TTL signal fell.

Circuit for Multisim11

So this is problem, does somebody know how to solve it in this circuit?


texts: What actually happens when both 1 input is given in RS flip flop circuit (physical change)?

texts:
This question is somewhat similar to:

Why is S=1, R=1 state forbidden in RS flip flop?

But I am asking what actually happens if both 1 input is given forcefully  in R and S terminal of flip flop circuit. Will there be any physical change? Will the flip flop circuit burn or get damaged? What will happen?

In the original question, it is written that:

  But if you set both R and S to 1 we have that Q = 0 and \$\bar{Q} =
 0\$ at the same time. This contradicts the relation \$Q = \bar{Q}\$.
  In the real world one of the gates will reach the 1 state first and
  the result will be unpredictable.

This is true theoretically. Both the output will be 0 which is not possible as both the output are complement to each other. So, is it correct to write the truth table of flip flop circuit in the following manner(here):

instead of writing \$Q = \bar{Q} = 0\$ when R = S = 1. This can be written as output cannot be determined as this case is not possible. We cannot say which output will give 0 and which will give 1. This is mentioned here (from the same link):

  R = 1 and S = 1: This condition violates the fact that both outputs are complements of each other since each of them tries to go
  to 0, which is not stable configuration. It is impossible to predict
  which output will go to 1 and which will stay at 0. In normal
  operation this condition must be avoided by making sure that 1's are
  not applied to both inputs simultaneously, thus making it one of the
  main disadvantages of RS flip-flop.

It is written that this case must be avoided. What worse would happen if it is not avoided? Will it get damaged or burned?


texts: How to add battery backup power source to a circuit?

texts:
I am still a beginner but I already managed to design a circuit around a PSoC 4 device with some peripherals (5V powered sensors, 5V powered mini fan, 5V step-down regulator for the main power supply and 5V step-up regulator for the sensors and fan).
The circuit will be powered with 5V DC main power supply which will be either a wall plug supply or a power bank with minimum 5V voltage but it does not matter I hope.

Now I would like to add a battery backup power in case the main power supply fails or will be removed, just to be able to put the chip in sleep mode and keep the real time clock running, which is provided by the chip.

So far the application description.

Now to ensure that my backup battery lasts a long time and really provides  current for the sleep mode only, which will be some uA, I would like to cut it off the circuit in case the main power supply is available.
I woud like to use a N-MOSFET as a low side switch for this, but I am not really sure where to attach this mosfet in my existing circuit.
After some research I came up with the solution in the attached schematic image, and here are my questions:

1) Is this correct that way in general?

2) Do I need the N-mosfet switch at all? I found several statements which state, that the battery won't be used as long as it's voltage is lower than the voltage of the main power supply.

3) I heard in some tutorial about power sources, that it's in general not wise to share a common ground between grounded (my 5V wall plug power supply) and floating power sources. Is this realy a "problem" in my case?

4) Can I switch the possition of D7 and U4 or is it bad when Vout of U4 gets the battery voltage?

Noe: Vgate will be set high by the PSoC 4 device as soon a voltage drop is detected by a voltage comparator, to switch the mosfet on. The power for this critical time, between the main supply failure and switching on the battery backup, will be provided by a 220uF capacitor.

I will appreciate any hints on how to make a simple battery backup for a long battery life time.


texts:
I'm planning to build a digitally-controlled light dimmer circuit. I'm not trained in electrical engineering, and I don't want to do something that an electrician would immediately recognize as dangerous and stupid.

Please suggest a reasonable home set up for prototyping circuits involving 120V AC power.


texts: Troubleshooting a soundcard oscilloscope that doesn't appear to affect the computer

texts:
I'm attempting to build a soundcard oscilloscope, but my computer doesn't seem to be reading the voltage on the audio jack plugged into it.

I'm using an Acer laptop (product ID 00179-60315-00598-AAOEM) running Windows 8.1. It has one audio port with a picture of a pair of speaker-headphones by it.

I think that I've configured "Microphone" and "Stereo Mix" to line-in modes by (1) unchecking their "use this device for playback" box, (2) turning "Microphone Boost" to zero, and (3) deactivating all extra sound effects. Both devices are set to their "2 Channel, 16 bit, 44100 Hz (CD-Quality)" mode. Sometimes when I plug the jack from the oscilloscope probe in, before I turn the power to the signal on, "Audio Recorder" spikes up with a little green bar for a second, making me think that the things really are configured correctly. It only seems to do this when "Microphone" is in use, though -- not "Stereo Mix".

I've also tried plugging the probe into the microphone jack on a local Windows desktop computer and making the same changes to "Microphone", but without luck. "Audio Recorder" shows a constant little green bar, but it is not affected by the signal fed into the probe, or even if the probe is plugged in.

The oscilloscope-probe-to-be is very nearly the same as that described in the link above. It uses a 1/8" stereo plug, with one common- and two signal-sections on the plug. The wire connected to the section at the very tip, however, doesn't seem to be making a very good connection, so only the middle section actually gives a signal out. I'm reasonably sure that it works. I've hooked the probe up to a sinusoidal test signal and looked at the voltage on the plug's middle section with a real oscilloscope, and it matches pretty closely with what's coming out of the function generator. I've been trying signals of around 200 mV between 10 Hz and 100 kHz or so. It may be noted, however, that my function generator might be producing a really, really crappy signal.

So again, my problem is that my computer doesn't see anything when I plug the probe in. I'm looking both through "Audio Recorder" and "Soundcard Oscilloscope". I was thinking that the problem might be that the stereo jack's forward output isn't working, but "Soundcard Oscilloscope" is supposed to look at both outputs, I think, so I don't  know anymore.

I'm not very sure that Electrical Engineering is the right place it put this question, but it was focussed around an electronics project of mine and I don't know where else on Stack Exchange it would go. A migration to a more suitable site would be okay, however.

Many thanks for any advice on this; I'm pretty much out of ideas at the moment. I would gladly post more details or upload pictures and stuff on request.


texts: more than one mixing term has landed on xHz in ADS simulation

texts:
Advance System Design (ADS) Simulation....
I am getting in touch with the same warning from ADS during my simulation that "more than one mixing term has landed on 500Hz,4GHz,6GHz,8GHz, and 10GHz".
Can anybody( who knows about ADS simulations) tell me how it will be removed?


texts: What is beam coupling coefficient for linear beam klystron?

texts: What does beam coupling coefficient exactly tell? For eg. a voltage gain coefficient tells how much times the input was amplified. So what does beam coupling coefficient tell, like does it tell how much the beam is coupled with something?


texts:
I want to open and close a window using a DC motor and a lead screw. My window is 20 inches long.

I know buying recommendations are outside the scope of this forum. I have little to no knowledge about torque and RPM. Could someone tell me how to calculate the required torque and RPM to move a window 20 inches in less than 5-10 s? The window is pretty easy to open does that mean less torque is ok? Also, are brush-less motors better in this case?

Edit: I am using a lead screw(500mm long), which has 2mm spacing and a diameter of 8mm. Furthermore, my window requires about 2kg's of force to move.

This is a picture of my lead screw(https://hallroad.org/threaded-rod-lead-screw-8mm-500mm.html)

This is the type of window i have: link.(opens horizontal)


texts: Varying frequency by percentage, rather than with linear resistance?

texts: I'm using a 555 timer to generate musical tones, and employing resistors to get various pitches.  Instead of resistance by linear amounts (ie. 1KOhm) , is there a way to apply resistance by percentage?  For example, is there a type of resistor or other component which will reduce the flow to 50% ?  I ask this, because I would like to press one button to output half the frequency (an octave lower, musically) of the present frequency.  Alternatively, can this be done with capacitors? Thoughts?


texts:
I have a silly question which has got me confused. I've collected some data from a device I've designed to characterize the power usage in various modes. I used a power logger to log the power profile over a use session of about 400 seconds. I have this data as a log file with TIME and POWER columns. When plotted, the data looks something like the attached image (sorry for the analogue method).

How can I calculate the Wh power draw from the battery from this data?

I'm thinking to import data into python, then use a numerical integration to obtain the area under the power curve, and then what? Am I on the right track at all?

Thank you!


texts:
I'm an hobbist, so the reason of the silly question.
So I'm drawing with Eagle ( express ) a schematic for a DC motor driver with raspberry. I'm planning to use 2 L293D to drive four motors + another chip to drive a stepper. Anyway my drawing is at this point:

 since I got that adding all the component would create a big unreadable mess. How can make this more readable? Ideally the GPIO port on the left should be divided in smaller parts, but without loosing the information that pins are belonging to the same connector. How to do it?


texts:
I am working on an electronic water sensing mechanism.

In an underground water tank I need to sense various levels of water as the water level is consumed and refilled. Later I want to control the sump motor with logic when various conditions are met.

Docusing on just electronic sensing mechanism there are many choices available

bias a transistor with the help of water as conductor
use Logic gate inputs to become HIGH/LOW when water touches probes.
Several choices for gates, any gate can be used in general, even a NOT gate can do.
Ultrasonic depth sensing.
LDR based
various other.

I am working with logic gates at the moment but will transfer it to micro controller later when I am satisfied with 'water sensing'.

The problem with many techniques above are, their reliability changes with many environmental effects. water vapours, hydration, corrosion, electrolysis, temperature and many similar factors change parameters which can affect changes in sensing.

Currently I am working with NAND CD4093. It has built in Schmitt trigger so it can shape inputs.

I prefer to give oscillated inputs to this logic gate, so at least electrolysis can be prevented. probes will be usually dipped in water.

To perform oscillation in sensing probe I can use transistors (AC biased), 555, opamp.

Q.1 Which one would be better option for oscillating in this scenario?

Q.2 How can I simulate the properties of tap water in reservoir e.g. water conductance and other electrical properties in NI multisim?
currently I GND the inputs with a switch to give the effect of water touching the probes in NI MultisIM. How I can model the real water properties effecting my probes

Q.3 any other idea to achieve the task?

I want 8 points of level detection, each point is one foot higher than previous one.

From full to empty, the difference is approx is approx 10 feet. This is an underground tank of concrete.

I want it reliable and long lasting, free from errors and safe from enviromental changes. a one time install solution, no corrosion at probes, no electrolysis, no
reading errors due to temp changes, hydration, vaporization, ...

Tank bottom is approx 10 feet from top.

Level readings at the moment will only light up LED's but at the next phase they will be the inputs to a micro controller based logic algorithm implementation where two pumps will be in service in parallel but one at a time, next time next up, will take turns. several conditions will be checked to turn the right pump, or to just give warning beeps. and more ... but this all will come in next phase, later.

Updated - - -

I understand all three oscillators I mentioned, AC biased transistors, 555 clock generator, OP AMP generating square waves.

I want an oscillator which will oscillate in +ve and -ve polarities, this scheme can avoid electrolysis.

I think OP AMP will do that better.

Now how to make the reading from probe non-oscillating so that it can be fed to a logic gate, otherwise logic gate output will also oscillate.

Should i use de-bouncing before giving input to logic gates

Are there any stray capacitive/inductive or other parameters in tap-water other than the conductance (or resistance) that should be taken care considering digital inputs?

I am trying to avoid any commercial sensors. I prefer building my own.


texts:
I am using a STM32F415RGT6 embedded in the 1Bitsy Board. I want to set up the I2C Peripheral in order to read some data from a sensor. I am using the stm32f4 standard peripheral library.

My example code:

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

GPIO_InitTypeDef gpioInit;

GPIO_StructInit(&gpioInit);

gpioInit.GPIO_Mode = GPIO_Mode_AF;

gpioInit.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;

gpioInit.GPIO_PuPd = GPIO_PuPd_UP;

gpioInit.GPIO_Speed = GPIO_Speed_25MHz;

GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);

GPIO_Init(GPIOB, &gpioInit);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE);

I2C_DeInit(I2C1);

I2C_InitTypeDef I2C_InitStructure;

I2C_StructInit(&I2C_InitStructure);

/* I2C configuration */

I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;

I2C_InitStructure.I2C_ClockSpeed = 100000;

I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;

I2C_InitStructure.I2C_OwnAddress1 = 0x01;

I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;

I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;

I2C_Init(I2C1, &I2C_InitStructure);

I2C_Cmd(I2C1, ENABLE);

while (I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY));

/* Generate Start, send the address and wait for ACK */

I2C_GenerateSTART(I2C1, ENABLE);

while (!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));

I2C_Send7bitAddress(I2C1, 0xE0, I2C_Direction_Transmitter);

while (!I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));

After that I want to write a 0x00, but the code always hangs in the last line, apparently the Master never reads the acknowledge. The I2C status registers always read:

I2C1 -> SR1 = 1024

I2C1 -> SR2 = 3

which means that the Acknowledge Failure bit is always set. If I analyze it using my Saleae I get the following:

The Slave sends the ACK, but the STM32F415 cannot read it.

The weird thing: If I try the same code on my F407 - Disco (only with clock set to 400khz, but it's the same behaviour on both MCUs regardless of Speed), it works flawlessly:

All other peripherals work fine. I already tried several workarounds, but the AF bit is always set, regardless of method. I hope you can help me.

P.S: I have tried with and without additional pullups and the I2C Slave Address is fine, because it works with STM32F0, STM32F4-DISCO and Atmel Mcus.

Best Regards and Thanks in advance!


texts: What is that rotating component for menu?

texts:
On some home made electronic circuits, to navigate the menu on LCD screen, a rotating component is used. My first guess was that it was a potentiometer and ADC was used for detection, but it rotates endlessly in any of directions. Does any one know what component is used for that?

Example: Ben Hack Show, https://youtu.be/xJndXebTG9I?t=13m40s


texts: Active high, rising edge circuits update state when, exactly?

texts:
I'm very new to electrical engineering. On a recent exam, we had a circuit with two JK flip-flops connected in series with one another. The circuit is beside the point, however.

Both flip-flops were active-high and had a delay τ that was one eighth the period of one clock cycle. ( In other words, the time during which the clock was high equaled 4τ. )

Which means the clock cycle was long enough for each flip-flop to update up to four times.

On the exam, the signals to both flip-flops J and K pins were toggled several times while the clock was high, so that--if the flip-flops change state in response to a high signal on the clock--the flip-flops would update state several times before the clock signal fell to zero.

My question is--when someone says a circuit is active high, does the circuit read input to determine it's state only when the clock signal is rising? Or does the circuit respond to changes on its input pins as long as the clock signal is high, regardless of whether the clock signal is rising or constant high?


texts: How to model the three phase pwm rectifier?

texts:
I have been working on a dynamic model of the three phase pwm rectifier also known as active front end (AFE). The circuit diagram is following

I have decided to solve that task this way:

choose some variables as a state variables (common approach is to choose the energy related variables as the state variables i.e. currents of the inductors and voltages of the capacitors)
make a list of all the possible switching states of the converter
write down the differential equations for the state variables chosen in step 1 in each switching state of the converter

According to the step 1. I have chosen following state variables \$i_{ag}, i_{bg}, i_{cg},v_{bus}\$. As far as the list of all the possible switching states of the converter there is \$2^3=8\$ possible switching states which are fully determined by the states of the control signals \$[S_a, S_b, S_c]\$ (\$S_i = 0\$ in case switch is open and \$S_i = 1\$ in case switch is closed) assuming that the high switch and low switch in the same phase works complementary. As far as the set of differential equations for each switching state:

State 0 i.e. \$[S_a, S_b, S_c] = [0, 0, 0]\$

$$
\frac{\mathrm{d}i_{ag}}{\mathrm{d}t} = \frac{1}{L_f}\left(v_{a0} - R_f\cdot i_{ag} - v_{ag} - v_{n0}\right) = \frac{1}{L_f}\left(- R_f\cdot i_{ag} - v_{ag} - v_{n0}\right)\\
\frac{\mathrm{d}i_{bg}}{\mathrm{d}t} = \frac{1}{L_f}\left(v_{b0} - R_f\cdot i_{bg} - v_{bg} - v_{n0}\right) = \frac{1}{L_f}\left(- R_f\cdot i_{bg} - v_{bg} - v_{n0}\right)\\
\frac{\mathrm{d}i_{cg}}{\mathrm{d}t} = \frac{1}{L_f}\left(v_{c0} - R_f\cdot i_{cg} - v_{cg} - v_{n0}\right) = \frac{1}{L_f}\left(- R_f\cdot i_{cg} - v_{cg} - v_{n0}\right)\\
\frac{\mathrm{d}v_{bus}}{\mathrm{d}t} = \frac{1}{C}\cdot i_c = \frac{1}{C}\cdot\left(i_{dc}-i_{gdc}\right) = \frac{1}{C}\cdot i_{dc}
$$
The problem which I have is how to determine the \$v_{n0}\$ voltage. Can anybody help?


texts:
I want a simple programming jig for the Esp8266, Sadly, all of the jigs I can find on ebay and other sites, have not worked for me, and use the Silicon Labs CP210x, and I have had NO luck at all with that. Normally I use the NodeMCU and it is absolutely great (other than the size). So, my plan is to remove the Esp8266 from the NodeMCU board and then solder pogopins in it's place vertically and mount it in a frame I will build. the issue is that I have been unable to remove the ESP from the NodeMCU... A heat gun seems to be heating the board too much before i can get the esp off, and after it does not work. Adding solder to the esp pins doesn't work because there are resistors too close to the esp module and they get pulled off as well. Simply trying to unsolder each pin while lifting the esp breaks the pads off of the NodeMCU board.
Does anyone have any ideas on how i can do this? If all else fails, i can use the NodeMCU to program another but I will have to pin it so i disable the esp module is disabled and that isn't exactly optimal.
any ideas would be much appreciated and sorry for such a long post.

I have also had very little luck searching google for "desoldering castlated modules"


texts: Guitar effect dry through circuit / wet dry mix?

texts:
I'm working on a digital guitar effect pedal, but wanted to implement a "dry through" circuit so that I could mix the digitally effected/wet signal with the original unaffected/dry signal at the output. This might be a simply be input buffer and summing amp at output, but I might be totally wrong.
I'm struggling with a search term for that which is giving me any useful results, so thought I'd ask here. I think there might be a lot of input/output impedance issues in replies and that's a dark art to me. I think generally guitar effects pedals try to have a high input impedance and a low output impedance, so that maximum signal voltage is transferred to the following stage.
So I thought as I'm splitting the signal, at the input, that I should use an OpAmp, (maybe you can use an BJT transistor), to 'buffer' the input signal and give the input impedance which the guitar is expecting. After that buffering Amp I can split the signal into two paths. One (dry) would go directly to a summing amp at the output, whilst the other (wet) signal would go through the digital signal path to the summing amp at the output.
I think I'd need a dual gang Pot at the output to effect the mix ratio, but that's about it. I don't want to get into phase issues but I guess that might be inevitable.
So in short buffing amp at the input and a summing amp at the output, with a dual gang pot for mix ratio. All the time naively avoiding figures for impedance and phase issues.
So I guess my question is does that sound about right for a dry through mix circuit or totally wrong.


texts: Water level measurement using Optical Mouse Sensor

texts: I wonder if anyone has hacked an Optical Mouse sensor to measure water level in an overhead water tank? Its possible to read frames data from the sensor and if those frames could be processed with a MCU then it looks like its possible to detect water level in a tank. I am going to do it for a tank of 4 to 5 feet height using STM32F407 MCU. Is it worth a try?


texts: Can anyone explain reverse bias pn junction using only electrons as charge carriers

texts:
In forward bias condition p-type semiconductor is connected to positive side and ntype semiconductor to negetive side and the electrons flow from n-type to p-type to cathode of battery.

But imagine the same situation when the situation is reverse biased so now p-type is connected to negetive terminal of battery and n-type to positive terminal of battery.

Now there is excess of electrons in n-region and it is connected to positive terminal of the battery.So electron can flow from n-type region to positive terminal of the battery due to potential difference created by battery whereas in p-type electrons can flow from one covalent bond to another as they do in forward biasing.

Only difference is,here electron move in opposite direction (from one covalent bond to another) i.e. from n-region to depeletion region whereas in forward bias they move from depeletion to n-region.Which shouldn't be a problem

Now in this manner current must flow regardless of biasing so what's the correction?


texts:
I've bought a beginners' electronics kit, which has some electric components and things, and a book with several projects.
There is a list with all the components in the kit. There are 3 different capacitors in the kit:

3 100uF capacitors,
5 100nF capacitors,
5 100pF capacitors.
I know the 100uF ones, I've seen similar ones like them a lot in videos and inside some devices, and I know they come in different capacitance, so what are the other ones? And why do they looks very different from the usual capacitors? And why aren't they used as the usual shape capacitors?


texts: LDO Regulator Power Good Output Pin Question

texts:
MCP1755 has Power Good Output (PWRGD) output pin which is open drain. In page 15 of data-sheet it says

  The PWRGD pin may be pulled up to VIN or VOUT. Pulling up to VOUT conserves power when the device is in Shutdown (SHDN = 0V) mode.

1) How should I connect this pin. Should I leave it as not connected or pull it up to Vout pin with 10K. (I will not monitor the operation of converter I want only proper 3.3v regulation).

2) What is the exact purpose of this pin. Should we connect it to an ADC to see the operating condition if we want.


texts: Why is the electrolytic capacitor not polarity sensitive?

texts:
The issue

I was making a project in which I had to use a 2.2uF electrolytic capacitor in series with a microphone and weirdly, the circuit works even if I toggle the polarity of the capacitor, that is the capacitor can be inserted in either polarity to make the circuit work.
Why does this happen? What are the criteria for doing so intentionally? Additionally, if I am to substitute a ceramic capacitor with an electrolytic capacitor, in what polarity should the capacitor be inserted?

Schematic:

  This schematic is based on the manufacturer's schematic, in which also, a ceramic capacitor of 2.2uF is used.

This question is referring to the MIC portion of the schematic only.


texts: TSOP382838 IR receiver keeps outputting signal even if no infrared light is present

texts:
This is a beginner question.
This is my first time using an ir receiver. The one I have is a TSOP38238. I have setup a simple circuit that consists of a visible led and receiver. When I have no infrared light pointing to it, the led keeps blinking. Shown in the 3 second gif below.

(source: ezgif.com)
I am powering the receiver with a 5v dc source. When I point infrared light at it, the led blinks like it should be.
Why is this happenning? Does it mean there is infrared light at 38khz around me? Is this suppossed to happen naturally? Is there a way to fix it?


texts: Is my 7 seven segment Common Anode or Common Cathode

texts: I am making a stopwatch, i bought a common cathode 7 segment and i installed resistors gave ground(-ve wire of battery) to pin 3 and positive to each segments including DP but i didnt glow, after that i gave ground to segments and red wire(+ve) to third pin and it started to glow so i am now confuse weather my 7-Segment is common cathode or common anode? Also if it is common anode then can i use IC 4033 (Decade Counter) with it? (As i saw some where that i need to use different decade counter with it)


texts: Why have extra resistor in switch debounce circuit

texts: I am using a Laird BL654 module in my project, and using the dev board schematic to help me.  On the reset switch they have an external pull-up of 10k (R112) (in addition to the internal one on the module of 13k), which I understand is to give robustness against ESD.  The capacitor C63 I understand is for debounce.  What is the 150 ohm resistor for (R34)?


texts: Multicell overvoltage protection with op amps, how to get rid of oscillating behavior?

texts:
Still a beginner in analog electronics, so excuse me for  being inaccurate. Also I am playing with circuitjs@falstad.com which might not be the most accurate sim...

I wanted to provide a very sharp overvoltage threshold, while being able to stack more cells in series. So I went with a bypass MOSFET controlled by a couple of op amps: the first sensing the voltage and the second comparing it to a reference.

The circuit appears to work fine, clamping the 1 mF capacitor at 2.7 V. However as soon as I swapped the ideal op amps with LM741, I started to get wide voltage swings at the MOSFET gate and, in turn, large currents in and out the capacitor.

Where are these coming from? Can they be mitigated? I put a low pass filter at the gate which improved the situation, but can the source be addressed directly? ...or is it just a bad design?

Here is the circuit in the picture above
Here is my initial attempt, with two cells in series and ideal op amps.


texts:
For a project, I like to feed a sine wave to laser, this sine wave must have a DC value of 2V and it should oscillate between 2.5 and 1.5V at 100KHz. The current required is <50mA.

What is the best way to achieve this configuration?

UPDATE
What Olin described below is simple and elegant, probably works well. I have three bonus questions.

If I wanted to add a feedback fromt the photodiode inside the laser module to optimize the light output, how can I do that? (I am guessing some sort of feedback from PD to the + terminal of the Opamp for modifying the DC bias).
If I wanted less harmonic content, could I use an active BP filter that is narrow on the target frequency (100KHz etc) before the driver?
If I want a higher frequency the limiting factor would be the GBP of the opamp?


texts: What transistors can I use instead of BS170/2N7000, and what parameters to look at?

texts:
I'm following the below schematic for a tremolo guitar effects pedal. I'm trying to figure out how I can use any of the transistors that I have available (image further below) instead of the three listed, but have had a hard time understanding which values to compare in the data sheets.

What should I be looking at?

Schematic:

.

Available transistors:


texts: Can i replace 3 (parallel) capacitors 16v 1800uf with 16v 2200uf?

texts:
The motherboard model is G31T-M REV:1.0 .
The circuit is for the 4-pin 12v power rail coming from the power supply.

I'm replacing these because they are very bloated,
It's quite a miracle that the capacitors are still working xD


texts: How do I select an optoisolator to both provide zero crossing to a uC and controll a triac?

texts:
This application note states that zero crossing detection can be achieved in an AVR with just a couple of resistors. However, it forgoes galvanic isolation and this is not acceptable for me.

I would like to supply CMOS control signal to a triac, in the same time monitoring mains voltage for zero crossing. Is there an opto device, capable of both these tasks at the same time. Preferably a small,  DIP, not exceeding $1 device?

This is an AC input optocoupler:

And this is an optotriac, used for controlling power triacs:

Having them both in a sigle package, pointing in opposite direction, would, IMO, simplify and make cheaper implementation of simple AC load control.


texts:
I'd like to control a 20 amp, 240 volt AC resistive load with a heavy duty contactor.

The contactor I have is a Siemens 3TX7130-0DB03 rated for 30 amps, and DPDT.  I was originally going to switch both lines on this relay.  But I got to thinking...

Would it be easier on the contactor to use both poles in parallel to switch the same line, and leave the other line always powered?
What theory or research would support that conclusion?

In short...

simulate this circuit – Schematic created using CircuitLab

Which of the above relays will last longer, why, and what other pros and cons are there?


texts:
I have this schematics here

Does anyone know how the capacitor in the black circle (disregard the blue circles) can discharge once it is charged up and the power has been disconnected.
It is suggested that it is discharged through the resistor but this cant be because once it is charged its left plate will be +5Vcc and the right plate 0V so to discharge through the resistor the charge would have to go through the insulation through the resistor and to ground?? Witch is impossible unless the capacitor is bad.


texts: So if I want my op-amp to produce a 12.5V peak value, and my op-amp data sheet says that with a 15V supply, minimum voltage output swing is 10V, would this mean that a 17.5V is sufficient to produce a 12.5V output?


texts: Do electricity meters contain inverters?

texts: In Germany the low-voltage grid is 0.4kV whereas the plugs in flats have 230V. Who is responsible for this conversion? Smart meter?


texts: Minimum number of NAND gates to implement f(x,y,z,w)=x(y+zw)+yz'

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As the title states, given a function f(x,y,z,w)=x(y+zw)+yz', what are the minimum number of NAND gates you need to implement f?

My first attempt at a solution was to draw a kmap to see if there was a further simplified boolean expression (technically I first drew the truth table to find the minterms). From the kmap, I found f=xy+yz'+xzw.

I know that you can implement AND using two NAND gates, OR using 3 NAND gates, and NOT using a single NAND gate. Thus, I figured, "well we have 1 NOT,2 ORs, 3 ANDs, so we'd need 1+(2*3)+(3*2)=13 NAND gates... But the correct answer is supposed to be 7!?

What's wrong/insufficient with my reasoning?
How on earth do you implement the function using just 7 NANDs?


texts: Why do speakers sound different when they're not fully plugged in?

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I've noticed that if there's not a good connection between my jack and the port, like if it's dirty or half plugged in, then the sound is different, but there is still sound, and sometimes twisting it around makes it sound better.

Why is that?

I was looking at some schematics of a 3.5mm headphone jack, but it doesn't look like there's a "this part of the jack gets the treble" thing going on. You'd think that if there's a signal at all, it doesn't matter which way the jack is twisted since it's a ring inside a ring anyway.


texts: How can I design a divide by 5 counter which counts from 6 and up to 10 then resets to 6. A normal divide by 5 counter is 3 bit counter which counts from 0 to 5 then resets to 0. I think my one should be 4 bit and require some changes so that it will not count from 0 to 5 but starts from 6 instead?


texts: control multiple inputs with one potentiometer

texts: I'm trying to build an analog synth. I'm reasonably adept in electronics but I have a problem. Its going to be a polyphonic so I want to have one pot controlling 4 oscillators because quad ones are expensive and I'm sure there must be a better way to do it. Is there a chip that could be used or is there something else I'm missing???


texts:
Hey I have a BLDC square wave controller. How to check the efficiency of the controller alone (not including the BLDC motor). Any suggestions ?

I have checked with DC load test machine, but what I get was the efficiency of both motor and controller. But I want to efficiency of the controller only.

Are two wattmeters suitable for this, which are designed for 3 phase power measurement?

I think  a power analyzer could be used but it is very costly and even we don't have one.
Advance thanks guys...