texts: Setting the absolute potential of an isolated DC power supply

texts:
I have a circuit that, for reasons out of my control, is powered by an bipolar +/-4V supply. This circuit includes instrumentation amplifiers and so forth that have input headroom requirements of over 1V.

I use an isolated DC/DC converter to produce a floating 5V supply from +4V/0. Now, I'd like to be able to reference the mid-voltage of this floating supply (2.5V) to the circuits ground, so that the 5V output actually looks like a +/-2.5V supply from the circuit's ground. The device running off the 5V supply is only going to send analog signals back into the main circuit, and that into high-impedance inputs.

How can I do this sort of biasing? All the currents involved are low, but precision is important to me. I'd like to avoid ground loops and the like as far as possible.


texts:
Could you explain to me why U_out is -4,4V and only 3rd diode is open in the following example? Given that R is 10kOhm.

My physics resistant brain tell me that voltage at each anode is is 10,15 and 20(I know it's now just teasing you) shouldn't all diodes be open if cut-in voltage is 0.6V? Why correct answer is that U_out is -4,4 and only 3rd diode is open? I think I don't really understand how voltage works. Given voltage is similar to water pressure and current can't never flow in stop direction through diode. Then only "pressure" maker is +15V and maybe U_out. How I get to know what is U_out and which diodes allow current to flow if I need knowledge of which diode is open to calculate U_out from Kirchoff's 2nd law and I need to know what is U_out to calculate which diodes are open. I am really confused about this example. I think I am missing knowledge of some crucial law or something, but you can't learn something if you dont' know name of it. And I don't have the time to study subject thoroughly now. Please tell me what I am missing here.

EDIT: U_out was confusing me(I thought it's some SEM not just voltage between wire and "ground"). It's really easy after this realization.


texts: Verilog - Does a register retain its current value if not explicitly told to do so?

texts:
Consider this code:

reg myReg [4:0];

always @ ( posedge clk )
begin

    if ( someCondition )

        case ( someValue )

            1       : myReg <= 20;
            2       : myReg <= 31;

            //default : myReg <= myReg;

        endcase
end

If the statement default: myReg <= myReg is commented out, what happens when someValue in the case condition is not 1 or 2?


texts: Control a lot of IR sensors with Arduino / Build a game board tile

texts:
Is it possible to control a lot (let's assume 100) of TCRT5000 IR distance sensors with one Arduino? So just use one or a few pins but not 100?

I am relativly new to the Arduino/electronics area and I know about the I2C protocol which would allow that but the TCRT5000 does not support I2C as far as I know.

I have seen people using it but I am not sure how, maybe there is another chip required? Any recommodations where to start?

Datasheet TCRT5000

UPDATE

Wow, what an overwhelming response! Thank you all for all the time and effort you put into this. I will add more details here, sorry that I didn't include them in the first place.

CLARIFIED QUESTION

As it is not necessary to use the TCRT5000 and I think there might be better options I have to clarify more what I am trying to create:

I want to build the concept for a single tile in a board game which is able to:

Illuminate the tile in any colour - I already have a good solution by using a low cost addressable LED strip and control it via the Fast LED library
Detect if there is a piece on top of the tile - this is where I want(ed) to use the TCRT5000 for - and it is very cheap. But as there is already light in the tile maybe a photocell measuring the reflected light would be an option too.
Optionally detect what type of piece is on top of the tile - that is not required but it would open a few more doors in developing the software driving the game. Thought about low cost RFID or magnet detectors. I don't think it is possible to get this cost efficient enough.
It should be scalable - so preferably one tile would work independently.

The amount of tiles used in the game will be determined by the cost of a single tile, therefore it has to be as cost efficient as possible.

The cost efficiency if not for me - If I find good solutions for the concept I would like to publish it. And that is only possible if the game is affordable.

GAME TILE

One tile could look like this (not scaled properly, just a sketch) and contains a SD 5050 LED from a LED strip and a TCRT5000 to detect if there is anything on top of it.

The electronics will be covered by a frosted acrylic plate to diffuse the light and protect the components:

Now the task is to detect a game piece on top of the tile:

The piece is obviously not always perfectly centred as the player will just put it somewhere on top of it. But the tile has to be able to detect if there is anything or not.

HELP

As this starts to go way beyond the initial question and I realized how much I don't know about electronics yet I would like to ask for help with the project.

If anyone finds this idea interesting I would be happy to discuss more details about the project outside of StackOverflow.

As this is a private project I cannot really pay money but if we get to the stage where the game is published you will get a free copy of the game and at least one carton of beer ;)

Please write me at ledboardgame/gmail.com (replace the / with @) including your experience (just tinkering, evil mastermind, ...)


texts:
I've seen that many (if not all of them) MEMS, like accelerometers, they are only available in QFN packages.

Why is that?


texts: Issue with TP4054/How not to damage li-po charger ICs

texts:
My issue is: The TP4054 I am using started drawing 150 mA after something I did. I know that I have probably fried it and the obvious answer is I should ditch it and take a new one. However I am not sure what exactly caused the failure and I would like to know it for the future, and also so I don't fry the remaining ICs I have. Here goes the story:

I have designed a board in which I am using a li-po battery. Naturally I want to be able to charge it so I decided to use a TP4054, which is carried by my chosen assembly house. An English language datasheet is here. Here is the configuration I am using:
A 5.5x2.1 DC connector goes into a TP4054, which charges a battery connected to the J3 "JST_PH" connector (disregard the J2 "POWER" component, it is for connection redundancy), which then goes into a 3.3 V regulator to supply the circuit. I've used 10K resistor to set the max charging current to 100mA.
I will now explain my steps during the assembly and testing of the board.

When I initially assembled the board and wanted to test it, I first plugged in the DC jack. My power supply was a 5 volt adjustable supply with insignificant ripple. The circuit powered up, being supplied by the voltage from TP4054. I quickly disconnected the DC jack since the circuit started to turn on and off, I guess due to the fact that TP4054 regulates voltage by switching. Then I connected the battery and tested if the battery was actually being charged. And it was, since the battery voltage rose from 3.95 to 4.05 in half an hour or so, that I had the charger connected. After a while I decided to check the power draw in my circuit. With the charger disconnected I measured the current from the battery and got about 150mA. I checked the PCB for the hot spots using a wet finger technique and sure enough the TP4054 was at fault. After I removed the IC the circuit drew a more usual 5mA or so.

The question is: what could have gone wrong? I couldn't have exceeded the voltage rating for the IC, since the maximum it was connected to was 5V. Can a static shock cause such damage in those ICs? Maybe it's a common issue and I should avoid using those ICs alltogether? What's the general "safe" approach to using li-po charger ICs so that a chance for such issues is minimized?

Edit: Made clear that the high current was being drawn from the battery, not the charger.


texts: Tracking the location of NFC chips on a board

texts:
For a oroject, I am looking to track the location of several game pieces on a game board using NFC chips. This board is made up of a grid and would need to send the location back to a device. I was wondering what the best solution to creating this would be.

Using several readers seems like overkill and has the possibility of interfering with each other.


texts: Why do fuses have a maximum breaking capacity?

texts: Wikipedia told me that breaking capacity is the maximum current that can safely be interrupted by the fuse. I don’t understand why, if a small current can blow the fuse, a bigger current can’t. If the current which is bigger than breaking capacity will cause arc, why a small current with the same voltage won’t?


texts: How to power a phone with no battery properly?

texts:
I have an LG G3 phone that I want to use as a stationary device and leave it hooked up permanently.
I prefer not to do it with a battery for various understandable reasons.

My questions are:

What parts do I need to convert USB 5V to 3.8V?
(I guess a voltage regulator, but is that all I need? and which one to get?)

What other factors (like currant) should be considered and how to deal with them?

Thanks!


texts: How to "unground" a low state of a not gate

texts:
I have a seven segment display(LTS4680AE) and the anode of each segment keeps getting grounded. So I basically have a 4 bit adder which adds two 4 bit numbers and produces a 4 bit output. This output is connected to the input of a 4x16 decoder.The decoder gives out a "low" signal as active(For example: suppose the output of the adder was 1,then 15 outputs of the decoder would be left high and the one which corresponds to the input combination 0000 would be the only one that is low. So I take each output and invert it using a not gate.The output of the not gates are connected to the corresponding segments on the 7 segment display(For ex, 0000 is the output of the addition,this would make the output pin of the decoder that corresponds to the bit combination 0000 low.This output pin is then inverted(using a not gate) and connected to the segments in such a way that it will form a 0 when the 0000 pin of the decoder is active.

This method works perfectly fine for 1 digit.But when I wire it up to display 2 different digits the anode connections to the display get grounded by the other anode input of that segment from another digit.Is there a way to prevent this? I am using a 74154 decoder and a DM74LS04 not gate.The display is an LTS4680AE single digit seven segment display.If you need more information about the setup just ask.


texts:
From the datasheet the open loop phase shift is given as 90 degrees for a range of frequency.
But why doesn't a a normal open loop inverting amplifier does not show this characteristics of the phase shift of 90 degree.Instead it just inverts the output(Or say 180 degree phase shift).

What happened to the phase shift given by a Op amp?


texts:
I want to communicate with SPARTAN 6 FPGA through PCIE for data transfer using Programmed IO (PIO) method.I am confused with following questions.

1)What is the role of BAR reg in PIO design(while filling in Xilnx's endpoint block IP core)?
2)What is the role of this signal trn_rbar_hit_n ?


texts: Need a simple circuit and IC for low voltage indicator

texts:
I have a battery operated power distribution system for some audio gear I use. I need to implement a multi-level voltage indicator via LED:

Green when the voltage is above 14VDC
Orange when the voltage is between 13VDC and 14VDC
Red when the voltage is below 13VDC

I will also implement an auto-cutout when the voltage drops below 12.5VDC.

Is there an IC that will do this for me or am I going to have to grab a microcontroller?


texts:
I have been doing some soldering in my garage, and because of my solder sucker, there is a some lead dust/powder on the table and floor. What would be the best methods for cleaning up as much of this as possible.

I ruled out vacuuming for the worry of spreading, and I do not have a shop-vac, so I cannot just wet the floor and suck it all up.

The best bet that I can think of is to just get a damp towel, and dab the affected surfaces, afterwards throwing the towel in the wash for an extra long run.

Is there a better way?


texts: How do I eliminate latches in FSM Verilog implementation?

texts:
I'm trying to create an FSM that left shifts a register until the MSB is 1 while counting the number of shifts completed. However, I have an issue with latches because I don't re-assign each register on a state change; namely, the shift and ctr registers (see the "if (shift[3])" statements). To get rid of the latches, I know that I need to assign these registers, but I don't want their values to change at the end--I want them to remain constant.

How do I achieve this?

`define RST 2'b00
`define LSH1 2'b01
`define LSH2 2'b10
`define DONE 2'b11

module leftshift(clk, rst, x, shift);
    input [3:0] x;
    input clk, rst;
    output [3:0] shift;

    reg [1:0] state, nextstate;

    reg [3:0] shift; // reg holding shifted bits
    reg [2:0] ctr; // ctr keeps track of how many shifts until completion

    always @ (posedge clk)
        if (rst) state <= `RST;
        else state <= nextstate;

    always @ (state, x, shift[3])
        case (state)
            `RST: begin
                shift <= x;
                ctr <= 0;
                nextstate <= `LSH1;
            end
            `LSH1: begin
                if (shift[3]) begin
                    //shift <= //don't change;
                    //ctr <= //don't change;
                    nextstate <= `DONE;
                end
                else begin
                    shift <= {shift[2:0], 1'b0};
                    ctr <= ctr+1;
                    nextstate <= `LSH2;
                end
            end
            `LSH2: begin
                if (shift[3]) begin
                    //ctr <= //don't change
                    //shift <= //don't change
                    nextstate <= `DONE;
                end
                else begin
                    shift <= {shift[2:0], 1'b0};
                    ctr <= ctr+1;
                    nextstate <= `LSH1;
                end
            end
            `DONE: begin
                //shift <= //don't change;
                //ctr <= //don't change;
                nextstate <= `DONE;
            end
        endcase
endmodule


texts: How does an increase in operating frequency result in decrease in the size of an inverter circuit?

texts:
I was reading about inverters in a textbook where the author says that

  The size and cost of the circuit can be reduced to some extent if the operating frequency is increased but then inverter grade thyristors must be used which are costly.

How does an increase in frequency have an impact on the size of the inverter circuit(or does it affect the rest of the circuit too?).Is there some physics involved which causes this?


texts: aluminum PCB soldering techniques for prototypes

texts:
I am wondering if i ordered some aluminum pcbs that contain D2pak transistors and i want to solder a couple of them for testing is it possible using basic equipment or does it need an Reflow soldering Oven .

Equipment i have access to :

1. tempreture controlled soldering Station .

2. WHP 1000 prehating hot plate.

3. Solder leaded and lead free , with/without rosin core , flux , etc....

Questions:

Is soldering these PCB any different from ordinary (FR-4) PCBs ?
does the factory or assembly line use different procedure ( heat
profile and temperatures ) ?


texts: How to create circuit for low voltage trigger of a relay

texts:
I have the relay in the picture above and have it powered with 5 volts.
My question is how do I wire up the trigger. Correct me if I'm wrong but I'm assuming that if I send 5v 2a to the trigger pin it will fry it. so how do I drop the multage and or amperage to safely operate this relay. No information came with the relay for the voltage/amperage requirements.


texts: The differential protection relay may lose its stability through fault due to the saturation of a CT magnetic circuit during a short circuit condition. To overcome this, which type of relay should be used?


texts: PIC Micro - Can I use both sinking and sourcing maximum current ratings if some pins sink while others source?

texts:
I intend to drive 6 LEDs with the PIC12F519 microcontroller if I am able to do so.

On page 61 of the datasheet the maximum current ratings are given:

Max current sourced per pin  ....... 25 mA
Max current sunk per pin ........... 25 mA
Max current sourced on port ...... 75 mA
Max current sunk on port .......... 75 mA

Now, my question is: am I at or above the maximum ratings if half the port sources 75 mA while the other half sinks 75 mA? In other words if I source some and sink others do I have 150 mA to play with or do I have 75 mA?

Thank You


texts: Laptop fried from spark while connected via USB to a battery system

texts:
EDIT 10/11 9:40am Central:
  I learned from my partner on this project I got the order of events wrong. I have edited the post accordingly.

I am working on some custom electrical hardware for modifications to a battery powered (24V) vehicle. All of my electronics live inside a painted metal box. Recently, after a laptop was connected via USB to my custom hardware, the laptop was placed onto the metal box and immediately there was a spark, and my laptop screen died without recovery. The laptop was on battery power, and the custom hardware was powered up.

I don't know exactly where the spark occurred. It could have been on the laptop metal case, or at the large data/power docking port on the bottom of the laptop (DELL precision m4800).

About the electronics:

The custom electronics operate at 24, 12, and 5V, all powered directly from vehicle battery with DC-DC converters.
All of the custom added electronics share a common ground which is the negative terminal of the 24V main battery.
I have chosen my 'functional earth' for Ethernet shielding etc to be the box/vehicle frame.
All of the custom added hardware lives in a metal box that is electrically connected to the frame of the vehicle (my functional earth). There is a 500kOhm resistance between the vehicle frame, and the negative terminal of the battery.
The vehicle runs on rubber wheels, indoors, on a plastic like painted floor.

I don't understand what caused this spark with enough energy to break my laptop. How could such a damaging potential difference form between the metal box and the laptop case/internals?

Most importantly, how can I safely prevent this from happening again?

Thank you for any help and feedback!

EDIT: Newly updated artwork


texts: Programming and using a flash memory PIC

texts:
I'm learning how to program a PIC12F609 and I have what (I think) is a silly n00b question. As a test I'm trying to burn a program that simply turns all 5 IO pins to output and turns them all on, so that if I connect an LED in series with a resistor to any pin it will light up. My program is dead simple and builds fine and MPLAB says the PicKit3 has successfully programmed the device. But when I try to use the programmed chip it doesn't work.

My fear is that the program is expiring from the memory as soon as I disconnect the PicKit. My plan was to program the PIC, pull it out, drop it into the LED circuit and connect the power source (9V battery run through 5V regulator). In all my previous microcontroller experience, the program disappeared from RAM as soon as power stopped and only programs stored in EEPROM, which this tiny 8 pin Pic doesnt have, would boot when power was reconnected.

If this is the case, how do I get a program to "stick" on my chip? and if not, what else about my process seems wrong?

edit: I'm posting my code in hopes this will be helpful. I really appreciate the thoughtful answers that have already been given, hopefully this way someone can help me set my configuration switches.

#include <12F609.h>
#include <stdlib.h>

void main (){
    // All five IO pins are on port A.
    SET_TRIS_a(11111);
    OUTPUT_a(11111);
    while(1){
        // endless loop, my attempt to make sure it didn't stop running
        // I've also tried putting the OUTPUT and TRIS in here but no luck
    }
}

my configuration bits are

FOSC - Oscillator Selection bits - RC oscillator
WDTE - Watchdog Timer Enable bit - WDT disabled
PWRTE - Power-up Timer Enable bit - PWRT enabled
MCLRE - MCLR Pin Function Select bit - MCLR pin function is MCLR
CP - Code Protection bit - CP is disabled
IOSCFS - Internal Oscillator Frequency Select - 8 MHz
BOREN - Brown-out Reset Selection bits - BOR enabled.

I think I understand what most all of those do, but I really don't know enough to select the right ones.


texts: Flyback transformer driven using a H-bridge damages flyback?

texts:
I tried driving a flyback transformer salvaged from an old tv, a couple of days ago using a H-bridge driver which I made in past. The pwm signal used to drive is between 62KHz to around 8MHz, this generated by an arduino. At 62Khz (Potentiometer is used to vary the frequency) arcs made from flyback is weaker while I increased the frequency around 600KHz or higher (I wasn't measuring) arcs became very strong and after a while everything stopped then there is some noise coming from the inside of the flyback and no arcs made. Then I got another flyback today, I thought previous one was a faulty one and I did the same mistake as I did back then and guess what the this flyback is also gone.
What could be the reason behind this? I assume there was an insulation breakdown between windings because the stronger arc frequency is it's resonance frequency and energy was high enough? Unluckily I had no 2n3055 transistor to drive this, I used it at my first time of using the flyback transformer.
Also, those fly-backs I got are both rectified ones.


texts: Illuminated LED and push-button using only 2 wires

texts:
I want to make a circuit with an illuminated LED push-button that is far away from the input board and I only have 2 wires available. The push-button is not something specific. The input board will have many buttons, but not all buttons will have LEDs. The input board will probably be a MCP23017 16-bit expander with an MCU.

I came up with this circuit:

simulate this circuit – Schematic created using CircuitLab

The MCP23017 is powered with 5V.

When the push-button is not pressed, the voltage at the MCP input pin is about 1V, low enough to register a 0 on the digital input.

When the push-button is pressed, the voltage is 5.6V without the added 5.1V zener diode D3, and 5 volts with the zener in place - well above 0.8 * 5V VDD required by MCP23017. But because the circuit is just a voltage divider 220+220 ohm resistors over the 12V supply, it will draw ~28mA, resulting in a bit of heat from the resistors. Because the push-buttons will not be pressed for more than a few seconds, I can live with this.

D2 LED was actually an opto-coupler to separate the long wire from the digital input, but I gave up on this protection for now.

I searched a lot on the internet for other ideas about how to power an LED and have a button using only 2 wires and no complex circuitry, but could not find any relevant info.

I built this circuit and it works, but one thing I cannot test is the influence of mains wires that run alongside my long button wires. They are separated and individually protected, but parallel to each other.

Do you have any other suggestions on how to use a button and an LED on 2 wires?

Later edit:

The buttons can only be normally open. They are European type light push buttons available only NO. LED is added by me.
Led should be lit all the time when the push-button is open. When the button closes there is no problem if the led tuns off or remains on. In this particular case, the led is used for night time finding only.

One other idea I had recently was to use input-output feature of the IO expander chip. Using the output to turn on the led, and then switch to input to check for the push-button state. Doing this fast enough not to see a flicker. But I haven't drawn any circuit yet.


texts: Why it is said that second transistor cannot enter saturation mode in Darlington pair?

texts:
When I made equations it came out that for both of transistors to be in saturation
Vc-Ve2<.2V
Vc-(Vb2-.7V)<.2V
Vc-Vb2<-.5V             ............{eqn a}
As for first transistor to be in saturation region
Vc-Vb2<.2V              ............{eqn b}
If eqn a is satisfied then eqn b will automatically satisfied
.So both transistors should be able to go to saturation if eqn a is satisfied.


texts:
Let's suppose the following circuit:

I am trying to find a relation between Vs, V1 and V2 at this circuit. Please note that Vs is measured in relation to the ground. I have declared some extra points (A,B,C) on the circuit and using voltage divider laws and the properties of an ideal operational amplifier I came up with the following solution:

Is this correct?

Another solution with a different result is the following:

I am really confused.


texts: How to protect my 555 timer against DC motor noise?

texts:
I have this circuit:

(Sorry for such a bad schematic.)

As you can see, there is a DC motor that gets power from 12V source, using a NPN transistor controlled by a 0-5V signal.

Please note that there is no 'direct link' between the 555 timer and the circuit for the DC motor.

However when POS_1 or POS_2 are active, the DC motor starts to run and the output signal ('CLK') of the 555 stops working, i.e., the LEDs that are suposed to blink with 1Hz frequency stop blinking. Actually, they start blinking at a very high frequency, I imagine that is noise which is filtering through the 12V source (which is also supplying the regulator that supplies the 555 chip.)

I'm sorry but I don't have an oscilloscope to prove this.

I've tried this:

To put a huge electrolytic capacitor (220uF) and a ceramic (1uF for high frequencies) between 5V and GND on 555.
To replace the 12V supply of the DC motor with 5V for a lower consumption.
To add in parallel to the motor a ceramic capacitor (100nF) to smooth its curve.
To change the resistors and capacitor of the 555 that are involved in the calculations of frequency, in order to avoid noise passing through the capacitor.

And other many little tests that I'm not able to remember at this moment.

What can I do to protect my 555 from the DC motor noise?


texts:
I have been around this forum, and I am not sure I found my answer. I would like to realize a small and cheap AC switch. Relays being too big, I got interested in IGBT.

The goal is to turn on and off a standard 220Vrms AC with a maximum load of 32A. I figured out that IGBT could be a good alternative because of their high voltage/current performances. As speed is not a constraint here, it seems to be better than Mosfet.

Here is what I image I could do:

There is no isolation in the 5V generator as no one is supposed to acces it (wireless control).

I would like to know if my circuit above is correct, and what would be the characteristics required for the IGBT to handle 220Vac 32A. For example, I had a look to this one: http://www.onsemi.com/PowerSolutions/product.do?id=TIG065E8
I feel it is a little too small to handle this job... but I can't see any solid reason in the datasheet showing that it cannot.

Thank you for any help.


texts:
Is there a way to save voltage data directly (without a microcontroller) to anywhere, like EEPROM, SDCARD, etc.?

For example, I am using an MPX pressure sensor which gives 0V to 5V analog output. Instead of converting voltages to pressure in a microcontroller and saving (which takes time, money, space, etc...), first, I want to save analog data, then taking these data to my computer for the conversion of voltages to pressure.


texts: Controlling momentary switch controlled machine with programmable socket

texts:
I'm trying to control a coffee machine with a programmable socket to make it switch-on in the morning (aah, love coffee smell while still on bed)

The problem is the machine is controlled by a momentary push-button as a toggle switch so obviously I can't set it on with no power and have it automatically switch on when the socket is on.

Do any of you have any good idea on what kind of circuit I could use to operate the switch only the moment the power goes on?


texts: Searching a connector for a test port on a router

texts:
I have a bunch of Teltonika RUT500 Routers which have a test connector on board which expose a serial console.

While I has able to access the serial port by soldering a connector to the contacts, I am now searching a suitable connector for the contacts. I have measured the pins an they are 1,27mm apart.

A PCI Connector may fit if cutted into the right size, but I wonder if theres another more fitting connector available.


texts:
I want to use this BLDC motor on a project. In its datasheet, the encoder pin sequence is shown as follows.

I want to control this motor with a VESC. There is an overview of the board here. In it, the encoder connector is described as below

Can someone please tell me if I can connect the motor encoders to this connector? (Presumably the ABI) I want to measure the distance traveled at the end of the day.


texts:
We are trying to make an high voltage window comparator circuit

The following are the design constraints
I cannot resistor divide the voltage as it would load the input
Unable to find a high voltage buffer

Input
Can be from 0.5 to 400 vdc
We do not have any problem till 70v as there are buffers available

To continue the above context, if we are able to detect this window then we will be able to switch the inputs to different signal conditioning circuit

Please suggest

This is basically a voltage measurement circuit


texts: Voltage at the load in matched transmission line

texts:
We have a source (Z_s) and load (Z_load) connected with a transmission line. It is known that the connection is matched, that means Z_s=Z_0 and Z_0=Z_load. If the voltage from source is 1V, what will be the voltage on load?

It may look as a textbook exercise, but it's not. I'm having hard time understanding  what is going on if we place a matched transmission line between source and load. All the books I have focus on reflections and physical details, but not much about more simplistic real scenarios.

If the connection is matched as described can the transmission line be ignored (considering it's loseless) and voltage on load be calculated from standard voltage divider? Thus, getting 0.5V on load, or do we need to consider the line also and it's 1/3V on load?


texts:
I need to convert a bunch of data signals from an FPGA coming out at 3.3V CMOS into 2.5V for an LCD display. I've found the SN74CB3T16210 and the SN74AVCBH164245 and they both seem like they'll do the job, but I'm worried about the clock line. I have a pixel clock running at around 10MHz that also needs to be level shifted and I'm worried that it won't come out clean.

Is the clock actually going to be a problem with either of these solutions?


texts: How to calculate voltage-power to lower voltage-power?

texts:
I have a solar panel 18V 2W. How do I calculate how much power that is at 5V?

Thank you in advance


texts: How to generate a clock for my ring counter?

texts:
I want to run a 4 phase switched reluctance motor at low speed. The expected conduction sequence for the motor winding(y, r, b, g) follows the output similar to that of a 4-bit ring counter and thus I want to use a ring counter to give gate pulses to the power circuit of the motor.

The problem is with the clock. I want to be able to generate the clock from the outputs of two optical sensors in motors rotors. The following picture explains what exactly I want to achieve.

So, using the two sensor outputs, Q1 & Q2, I want to make a clock as shown in the clock waveform, which I will feed to my 4-bit ring counter to generate the 4 expected phase currents, Iy, Ir, Ib, Ig. (As can be seen, these expected phase currents follow the output of a 4-bit ring counter).
Thus, will be able to run my motor at low speeds like 60/120/180 RPM.

How to generate the "clock" for the 4 bit Ring counter from the sensor outputs(Q1 & Q2) as shown in the figure above?

The clock will be positive edge triggered to the counter. Also, as the sensor output(effect) is generated as the motor rotates(cause) , initially I plan onto give a manual start to the motor via some extra circuitry and then as the motor attains some low speed, the external circuitry can be automatically disconnected and the counter circuit (using sensor outputs) will be used to run the motor.

Also, suggestions on some other different methods to run the motor are also welcome.


texts:
I have an Agilent 4980 LCR meter and in its manual it has several graphs indicating the effective measurement ranges for each scale, like the one below:

How to read such a graph to be sure that the instrument can effectively measure my device's characteristics? For example, if I have a 500 uF capacitor with an ESR in the range of 0.2 mOhm and ESL 10 nH, how to check these values in such graph?


texts: TIA portal - failed to establish a connection

texts: I'm using TIA portal siemens v15.1 for my project when i tried to upload the code to the plc this error pops up. Appreciate anyone can help me in this issue


texts:
What is meant by Lidar optical testing? The optical section of Lidar contains
1)Laser diode
2)Tx/Rx optics
3)Photodiode
Whether it meant testing the above sections? If so,What parameters are tested in lidar optical testing?


texts: Do I need to include my custom .lbr files when exporting an EAGLE project so that it is viewable?

texts: I have an EAGLE project that uses some custom library components. If I transfer the .brd and .sch to other people, do I also need to include the .lbr files for them to be able to properly view my design?


texts: How do I fix an error message "expecting an expression or operand" when reading an input file in cadence vhdl?

texts:
How do I fix the following error message?

ncvhdl -v93 -messages -linedebug -cdslib ../cds.lib -hdlvar ../hdl.var -smartorder inverter_test.vhd
ncvhdl: 06.11-s008: (c) Copyright 1995-2007 Cadence Design Systems, Inc.
inverter_test.vhd:
    file infile  : text is in
                           |
ncvhdl_p: *E,ILLPRI (inverter_test.vhd,31|27): expecting an expression or operand [7.1] [7.3].
    file outfile : text is out
                           |
ncvhdl_p: *E,ILLPRI (inverter_test.vhd,33|27): expecting an expression or operand [7.1] [7.3].
    errors: 2, warnings: 0

The goal of the code below is to pass input to a simple inverter that negates a bunch of 1s and 0s inside an input file.  However, there seems to be a compile-time problem with that code that tries to read input from the file. Skip down to the lines that say "PROBLEM HERE" to see where that compiler error occur.

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_textio.all;
use STD.textio.all;

entity inverter_test is
end inverter_test;

architecture test of inverter_test is

  component inverter
    port (
      input: in  std_logic;
      output : out std_logic);
  end component;
  for i1 : inverter use entity work.inverter(structural);
  signal ip,op : std_logic;
  signal clock : std_logic;

begin
  i1 : inverter port map (ip,op);

  clk : process
  begin  -- process clk
    clock<='0','1' after 5 ns;
    wait for 10 ns;
  end process clk;

  io_process: process
    file infile  : text is in -- PROBLEM HERE **********
      "inverter_in.txt";
    file outfile : text is out -- PROBLEM HERE **********
      "inverter_out.txt";
    variable ip1,op1 : std_logic;
    variable buf : line;
  begin

    while not (endfile(infile)) loop
      readline(infile,buf);
      read (buf,ip1);
      ip<=ip1;

      wait until falling_edge(clock);
      op1:=op;

      write(buf,op1);
      writeline(outfile,buf);

    end loop;
    wait;
  end process io_process;
end test;


texts: How does a synchronous motor know to increase current when the mechanical load is increased?

texts:
Consider a very simple singe phase synchronous motor, such as the one shown in figure 1. This motor will not be self starting, but if an AC voltage is applied and the permanent magnet is given an initial spin, the magnet will continue to spin at the same frequency as the AC source.

Figure 1:

If the mechanical load is increased, e.g the weight in the pulley system in figure 1 is increased, the current drawn by the motor will increase to provide the extra torque necessary. Source: bottom of page 428

What I do not understand is how the motor "knows" that it needs to increase the current drawn. There is no controller involved, the motor inherently does this. Somehow the information has been passed from the mechanical load to the electrical circuit even though nothing is connecting them. How does this work?

If I analyse the equivalent circuit:

The voltage across individual components is:

$$V_{R_1}(t) = i(t)*R_1$$
$$V_{L_1} = L_1*\frac{di(t)}{dt}$$
$$V_{L_2} = L_2*\frac{di(t)}{dt}$$

If connected to a sinusoidal voltage source

$$v(t)=V_{mag}\cos(wt)$$

And

$$L_1 = L_2$$

The current can then be found by:

$$i(t) = V_{mag}*\frac{R (-e^{-\frac{R t}{2 L}})+2 L w \sin(t w)+R \cos(t w)}{4 L^2 w^2+R^2}$$

(source)

Using trig identities:

$$i(t) = V_{mag}*\frac{R (-e^{-\frac{R t}{2 L}})+ (\sqrt{(2Lw)^2+R^2})\sin(wt+\tan^{-1}(\frac{R}{2Lw}))}{4 L^2 w^2+R^2}$$

In steady state operation, the exponential goes to zero and the magnitude of the current is given by:

$$I_{mag}=\frac{V_{mag}}{sqrt(4 L^2 w^2+R^2)}$$

This is independent of the mechanical load. But this cant be true as the current is supposed to increase when the mechanical load is increased. What am I doing wrong?


texts: Just how does high VSWR damage RF amplifiers?

texts:
Just how is it that a high VSWR can damage the final transistors in an RF power amplifier?

Is the transmission line significant beyond the effect it has on transforming the impedance of the load at the other end? Or would an equivalent lumped impedance directly at the amplifier's output be just as damaging?

Of all the possible impedances that result in a given VSWR, are they all equally bad?

Is the reflected power "absorbed" by the amplifier? For example, if I'm getting 100W reflected power, is that more or less the same as putting a 100W heater on the amplifier?

I've also read that excessive voltage can be the mechanism leading to damage. How is it that a voltage higher than the supply voltage can appear? Is there a limit to how high this voltage can be in the presence of an arbitrary mismatch?


texts: Could anyone explain why in this example \$ I_t = (\frac{12}{5} - \frac{24}{2})\$? It is my understanding that it should be \$\frac{12}{5}\$ because of the initial condition of natural response.


texts: How to turn on gauge lights from multiple sources

texts: I have limited experience with relays, diodes, ect. so I need a little help.  I'm currently building a rock crawler (off-road buggy) from ground up and I'm into the electrical and need some suggestions on turning on my gauge lights(4).  I would like to have the gauge lights turn on only when I have the headlights and/or my rock lights (undercarriage lights) are on.   Both sets are operated by separate fused SPST toggle and relay.  I realize that if I tie into both relays then power would back-feed to the other circuit.  I think a couple of diodes would be the fix but have no clue where to start with those, so I dunno.  I know the easiest way would be to just put it on a toggle by itself or just tie into the ignition circuit, but I like to complicate things.  Hopefully someone can give me an nice simple solution.  Thanks!


texts:
I am working with the following product: Lilypad Mini Protosnap https://www.sparkfun.com/products/14063

and have a few questions:

There are 2 parallel LED circuits on the board, each with 2 White Micro Leds which have a 150 ohm resistor per LED.

I want to know how this board works, since voltage drop for a white LED is 3.3-4 and the source voltage is only 3 V for the coincell battery [CR2032].

The led's work, and I don't understand how this is?

Secondly, how would I calculate if the I/O pin can take additional micro LEDS?...
So far i know that each pin has a maximum current of 40mA and each LED has a max current of 20mA.

This whole circuit feels problematic and would be happy to have some clarification, should anyone be able to assist?


texts:
I have a circuit that needs to electrically output a pressure value and display it using analog dial gauge. First I wanted to use regular round ammeters but they don't look like "real" pressure gaugeish. Have a look to get an idea about what I mean

Needle in a pressure gauges is usually mounted in the center and have a much more wider travel sector. The best I can think of is to get an auto tachometer, print a new dial face with pressure scale and remove all unnecessary control electronics from the tachometer leaving only galvanometer and a precision resistor inside. Then I plan to drive it with PWM. There is another type of tacho that uses a small stepper inside. This should be also fairly simple to drive.

I don't want to reinvent the wheel, so want to ask if anybody knows about a product that does exactly same job, i.e. pressure gauge simulator?


texts: Mechanisim or Circuit to detect angular position of rotating knob of Motor

texts:
I am trying to customize the normal AC motor in such a way that when it will be connected to computer by using some micro controller (e.g Arduino) its rotation will be calculated.
i can measure the rotation speed if i use Hall effect sensor which uses a refrence point to calculate rpm but my problem is i want to get the angular location of rotating shaft in terms of degrees in such a way that when motor will be turned on the one degree change must raise an event or generate a signal in microcontroller.
How i can achieve this i searched a bit on it and crawled the following info

Time Synchronization:
 in this way i will calculate the time taken for one rotation then calculate the time took for knob to move 1 degree. This way i shall start timer and calculate or pridict the knob location. this is good but obviously there will be uncertainty and it will not be perfect or reliable.

Stepper Motor:
Using a servo motor increases the accuracy because its moving steps will be counted and known and fixed in 360 degrees. but How i can convert a normal AC motor to Servo architecture i do not like this way.

A Specfific Hardware:
Well third approach may be designing a hardware that will be designed to be able to attach with any motor and it will update speed.
The Question is does some thing like this exists?

what approach is best accurate and reliable as well as easy to implement for this task.
if you have any other idea then i am waiting eagerly.


texts: Do 4-bit CPUs still outsell 32-bit CPUs in unit volume?

texts:
Way back in 2002, Jim Turley mentioned that about 14% of all CPUs sold were 4-bit CPUs, while about 8% of all CPUs sold were 32-bit CPUs.
(Most people I know were surprised that any 4-bit CPUs were still being made, much less that they were doing so well).

It's 2011 now -- Do 4-bit CPUs still outsell 32-bit CPUs and 64-bit CPUs combined in unit volume?
Where could I go to look up the latest numbers for sales by unit volume?
What are the top websites and magazines to learn more about modern 4-bit CPUs and their development tools?


texts:
In our last build we had issues with DDR stability in our prototype, simply because of lack of experience with this type of high speed memory connections.
We managed to get it working with halving the CPU speed, and loosening the timings slightly, but for our next version, we are trying to make it work 100%.
We are working with 454MHz i.mx233 and 133MHz EMI bus.

In our first prototype we had several mistakes:

Routed some of the data lines through 3 layers, and some from 2
Did not match the trace lengths
Our capacitor placement for memory power lines was not as close to the chip as possible.

This time we have fixed those mistakes, but would still like to hear some feedback from experienced designers.
We are very constrained with space (size) and layers (cost), so we did not have space for aesthetically beautiful bus design ;)

In our design tool it's impossible (to my knowledge) to color different layers differently when wires are "selected", so it looks messier (or difficult to read) than it is in reality. The AP and memory are both on top layer, processor being on the right.

So first of all, this time we have routed the clock (CLK, CLKN) lines as differentials, and they look like this:

Next, we have placed all the capacitors in the memory power lines as close to the chip as possible:

Our address lines are matched in length as much as was possible, and all go through 2 layers, so they have even number of VIAs in them:

And finally, our data lines are also matched in length as much as possible, and also these are routed on second layer for a moment (we had to route few lines through power plane instead of bottom, we just couldn't avoid this):

Our trace lengths are (in mm):

CS 18.8     CLNK 30.1   CLK 30.4    CKE 36.1
CASN 37.2   RASN 37.2

A0 37.2     A1 37.2     A2 27.2     A3 37.2
A4 36.2     A5 36.1     A6 36.2     A7 36.2
A8 36.2     A9 36.2     A10 37.2    A11 36.2
A12 36.2

D0 35.5     D1 35.6     D2 36.2     D3 36.2
D4 27.3     D5 36.2     D6 36.1     D7 36.2
D8 37.2     D9 36       D10 28      D11 36.1
D12 36.1

DQM0 36.1   DQM1 36.2   DQS0 35.6   DQS1 37.2
BA0 37.2    BA1 37.2    WEN 36.1

Indeed we are using 4-layer PCB with a separate power (some signaline here) and ground (no signal traces) planes. Previously we used seeedstudio's PCB service (Manufactoring specifications), and their default (cheapest) stack up is this:

Our trace width for EMI bus is 0,204mm, so if I calculated correctly the impedance, it would be over 60ohms in this case. Maybe trace width needs adjustment (thicker, somewhere around 0,3mm).

According to the Freescale's design guidelines, maximum trace length can be calculated from 0.3 x Rise/fall time x 15cm/ns (FR4 material). The memory we used looks to have slew rate of either 0.9 or 1ns, so in our case this formula would then produce: 0.3 x 1 x 15 = <4,5cm, so our trace lengths should be currently in spec.

After reading through the design guidelines several times and learning from our mistakes this is our current plan for next prototype run. We are grateful for any mistakes you might point out, or just any advice in general as well.. Thank you!

Edit 1 After some paint working, replaced the data and address line pictures with colored versions as suggested in the comments. Now it's much more clear what layers the traces go on - it didn't take that long once I got the hang of the masking, sorry I should have done it initially already.

Edit 2 Added PCB materials specification, and stack-up information. And some other additional information regarding the signal traces.


texts:
The issue I'm having is with Part C. I've rewritten the circuit with the Pi model as such:

I can't figure out how to get an iout/i relationship. I can only think of writing the current laws, but it doesn't seem to get me anywhere to where I can write the ratio. Since the top of r0 and bottom of r0 is grounded, I think no current can run through it, so it does nothing.


texts: Designing a circuit to record timing of power cut

texts:
I live in a place which is plagued by frequent power cuts (load-shedding). I have to design a circuit by which I can record the timings while power is gone or vice-versa. I also need an equivalent computer application which can be used to print daily/weekly/monthly reports of these power-cuts.

How should I go about doing this?


texts:
Usually MOSFETs stay in switched-off state by default and get switched on by a signal. But I want to use MOSFET the opposite way:

1) it should pull down a line to GND all the time by default, after power supply is ON

2) if needed, should be turned-off by signal from MCU, so that the line gets automatically floating

Is this possible?

In the schematics below R24 should either be connected to GND to enable charging or let float to disable it (according to datasheet MCP73833, chapters 3.4 and 4.2). As per chapter 1.0 the resistor R24 could be at least 200K to disable charging.

If the PROG pin is open
or floating, the MCP73833/4 is disabled and the battery
reverse discharge current is less than 2 µA. In this
manner, the PROG pin acts as a charge enable and
can be used as a manual shutdown.


texts: Instantaneous Power versus Average Power

texts:
simulate this circuit – Schematic created using CircuitLab

The above question is that of a past exam paper. I have a few questions regarding some of the theory and calculations behind this. My calculations were as follows:
$$
v(t) = 311.13 \angle 0^\circ
$$
$$
Z_T = Z_C + Z_L \parallel Z_R
$$
If the angular frequency is 314.15 rad/s
$$
Z_T = -jX_C + \frac{Z_LZ_R}{Z_L + Z_R}
$$
$$
Z_T = -j31.832 + \frac {78.54\angle 90^\circ 100\angle 0^\circ}{100 + j78.54}
$$
$$
Z_T = 41.66 \angle 23.7^\circ
$$
I do not really understand the intuition behind the Instantaneous versus Average Power calculations. For the instantaneous power in R, my usual calculation is:
$$
P_\text{inst} = i(t)v(t) = \frac{v(t)^2}{X_R}  \tag 1
$$
Am I allowed to use, say X_c or X_L in place of X_R here if I wanted to find the instantaneous P through the C or L? I have thought that the last part of the above equation was only valid for resistive elements, however I wouldn't know how to find instantaneous \$P\$ through \$C\$ or \$L\$ otherwise.
For the average power, there has been some debate amongst my classmates as to whether the average power is defined by:
$$
P_\text{avg} = \frac{1}{2} IV \cos\varphi \tag 2
$$
or
$$
P_\text{avg} = \frac 1 T \int_0 ^T P_\text{inst} \tag 3
$$
I know that equation (2) is the real power dissipated by the system, but am confused  between that and the average power dissipated by the system. In addition I am aware equation (2) is a derivation of (3), however I am not sure if one can apply (2) for any instantaneous P, or if there are cases where one must use (3).
I appreciate that this is a lengthy question so in summary:
Can one use the reactance of C or L in equation (1)?
What are the essential differences between real power and average power? Can one use equation (2) instead of (3)?


texts: How to calibrate Unipolar ADC in software

texts:
My ADC manufacturer have given the value of following error, value for Avrefm = 0V & AVREFP = 2.7V :--

Zero-scale error
Full-scale error
Integral linearity error
Differential linearity error

what is Zero-scale error is given in this link :--
http://www.edn.com/design/test-and-measurement/4430080/Measure-an-ADC-s-offset-and-gain-error

As per this link, full scale error contains information about gain & offset error :--
https://www.maximintegrated.com/en/app-notes/index.mvp/id/641

Full-scale error = offset error + gain error

FSR = full scale voltage range  :---

FSR = AVrefP - AvrefN

This link states that accuracy of the ADC can be derived from ADC Specifications :--
http://www.embedded.com/design/configurable-systems/4025078/Understanding-analog-to-digital-converter-specifications

The ADC specifications that describe this type of accuracy are offset error,
 full-scale error, differential nonlinearity (DNL), and integral nonlinearity
 (INL). These four specifications build a complete description of an ADC's absolute accuracy.

Atmel link says a lot about ADC errors :--
http://www.atmel.com/images/atmel-8456-8-and-32-bit-avr-microcontrollers-avr127-understanding-adc-parameters_application-note.pdf

I read many tutorials on google but none of the above link tells, how we can calibrate ADC in firmware?
Can we use these above data from manufacturer to calibrate my ADC in firmware ?
What exacltly is use of above ADC error data from manufacturer to end user ?

Or i have to use the technique mentioned in this link to calibrate Unipolar ADC for Gain error & offset error in firmware ?
http://www.microchip.com/forums/m391768.aspx

Please suggest i am bit confused.


texts:
After watching Afrotechmod's tutorial about reverse voltage protection, I wondered if I could incorporate it in a circuit I'm working on. Unlike the circuit in the video, mine's dual supply, and there's where things get lost on me.

Do I need to tie the MOSFET's gate to GND, or to the supposedly negative power rail? Is is even possible to do this with a single MOSFET, or do I need another one? If so, P-channel or N-channel?

simulate this circuit – Schematic created using CircuitLab


texts: how does this occupancy-sensor switch not need neutral?

texts:
Note, I don't think this belongs in DIY; it's a bit more complicated than that.

I bought a Lutron Maestro occupancy sensor switch, and was perplexed to learn that it doesn't need a neutral in the switch box (they brag about this as a feature, and the instructions don't mention it).

http://pdf.lowes.com/installationguides/027557983136_install.pdf

Note that in addition to the line and load (black) wires, the switch has both a bare wire and a green wire (drawing on top of 2nd page).  I'm thinking maybe the bare wire (which is connected to the yoke) is the "real" ground and the green one carries the return current from the sensor and logic circuitry.  But the instructions say to tie both to the switch box's ground

This seems most odd to me. I thought the whole point of NEC rule 404.2C, which requires a neutral in every switch box (with a few exceptions), is that when "smart" devices such as this are installed, that no currents are introduced into the grounding system.

I wonder what's going on. Is it:

Does the switch somehow not return any current to ground ?  I'm not sure this is possible, unless there's some sort of charge pump or something working off the hot wire(s).
Does the switch's logic sensor and logic circuitry use so little current that it is deemed (by UL and/or NEC) acceptable for those currents to flow through the EGC ?   I did not know there was a threshold.
This is only meant for retrofits into older construction not compliant with 404.2(C) ?  Would this even be legal ?  And if so, why don't the instructions say to tie one of the wires (presumably the green one) to a neutral if it is present ?


texts: Will 2 always@ blocks that run at the same time in verilog use old or recent values of outputs?

texts:
I have a question about this piece of verilog code:
  reg [31:0]ain = 3;
  reg aout = 0;
  reg bout = 0;

  always @(posedge clk)// A
    begin
      if (ain == 3)
        begin
          aout = ~aout;
        end
    end

  always @(posedge clk)// B
    begin
      if (aout == 0)
        begin
          bout = ~bout;
        end
    end

Basically this has 2 always@(posedge clk) blocks(a and b) where the second uses a variable set in the first. Now assume this entire thing isn't optimized away and ain could have more values maybe.
I'm wondering what version or time of aout block B would use, since both blocks run at the same time.
Would it be undefined behavior as A and B run at the same time? Or will B always use the value of aout that was set by A previous clock cycle? Or would it completely depend on whether A can complete before B?
The reason I want to know is because I want to create a riscv cpu where the instruction fetch and decoder and such are separated(instead of all combined like I have now) so that I can have it execute more instructions per second.
Also, what would be the best approach if I wanted to make sure B used the aout of A in the previous cycle?(So the result A set aout to at the end of previous clk)
Thanks!
Edit:
It appears my question might be a bit vague so I will try and clarify.
Currently my understanding(which I think is correct) is that A and B will be executed at the same time(in parallel), meaning that aout will change during the execution of A. However, B is trying to use the aout register for it's own logic. So my question is, will aout change value before or after it is used in the if by B? Or does it depend on whether the A block finishes before the if in block B? I need to know this so I can make sure that when I have more variables that I wont try to use the output from a half executed block.


texts: Software suggestions for electronic simulations?

texts:
I am a beginner in EE engineering and want to use a software where I can analyze signals or even motor speeds, power electronics ect. But the Spice programs looks so boring and detailed for me. Maybe it is because I'm new.
Is there an interactive easier software where I can for example feel like I am really using an oscilloscope on the screen?
I would appreciate your suggestions.


texts: How do I smooth out the voltage from a pulse-charger?

texts:
I've got a dc-dc pulse charger that charges my 12v lead acid battery. The pulse charger charges for 1 second and stops for 20 milliseconds.

My battery is powering some sensitive equipment, what can I do to make sure my 12v battery is always outputting a constant voltage without pulses (while being charged)?

My equipment can take 10 - 16 volts, but I'm afraid the pulses might be bad.

Thanks


texts:
I am working on a personal side project and trying to learn what I can about electrical engineering as I progress.

I want to use the CP60231H TEG/TEC but I need to calculate it's potential output for voltage, power, and current given a temperature delta of 17-20 degrees kelvin. In the project I will be using 2 in a series and want to know what one will produce by itself and what both would, even if it is an estimate.

How do I at least estimate the potential output without going out and buying one?


texts: Which adapter/handling to choose on (Type N) rf test devices when SMA/K cables have to be connected frequently?

texts:
I'm no expert in high frequency. But probably it is no good idea to change the adapters sitting on type N female output on and on as a torque wrench is used to fix them.

But I have to make measurements where often a amplifier or bias tee is connected betwenn a rf-probe and a signal generator or vector network analyzer. The rf-probes have 2.92mm K connectors, the devices (bias tee, amplifier) often SMA.

Now the probe vendor says that SMA cables/connectors damage the K-connector on rf-Probe.

As I want to use the expensive low loss cables maybe also in future up to 40 GHz, currently only 1-10 GHz, I'm wondering what is the right handling here? I also want to prevent to much insertion losses by many connector adapters. The money is not really the problem of if an adapter costs 100-200€

What do you suggest here? Combining SMA and K cables with adapters or changing the test device adapters (N to SMA/K) on and on (probably 100-200 times a year? Are there adapters or products I missed that could help me?


texts:
I'm working on project where I would like to measure inductance of 4 different springs (to measure weights) using uC - Arduino. I found out that you can do that by measuring frequency of LC circuit and then converting signal to digital using LM339 comparator.

Since you can only do accurate time measurement using Timer1 and its interrupt on pin 8, I thought it would be best to just connect all comparator outputs on LM339 together and using different uC output pins to charge up LC circuits. It all worked fine if only one coil has been connected, but if I connected another one, I got no output from them.

I used modified version of this code: http://codinglab.blogspot.si/2013/02/measuring-inductances-using-arduino.html
to read times and calculate frequencies on pin 8.
Edit: Principle is you charge one LC and measure the output frequency and then charge another and do the measurement and so on.

I suspect that those LC circuits interfere with each other, but I have no idea how to solve that problem. The circuit that I made:


texts: CAN Transmission and termination resistors

texts: I have been trying to set up a CAN network using PIC18F25K80 microcontrollers and an MCP2551 to communicate between them. Can I use two simple wires as a CAN bus by just connecting the CANL, CANH of the transceivers? I couldn't even transmit data with the set up I have made with two wires! Should I terminate them with some resistance?


texts:
I'm using GHDL to simulate some designs that I'm doing. Now, I included the float_pkg package to work with floats in Sigasi but when I'm simulating in GHDL it states that primary unit "float_pkg" not found in library "ieee"

How can I add this new library to GHDL? Copy/paste to the GHDL>lib where we have two folders "v93" and "v87" doesn't seem to work.


texts: How to determine the corner frequency needed?

texts:
I want to design a second order sallen key low pass filter.  I want to attenuate a 100Hz signal to around 10%.  I need to use a 2nd order low pass filter.  How could I calculate the corner frequency such that I will achieve this 10% attenuation at 100Hz?
In this case a Butterworth Filter has to be used.


texts: How did Hertz prove existence of radio waves?

texts:
I am asking two questions to improve my understanding of electromagnetic energy transported into free space from current in a conductor.  At one time I thought all such energy was considered electromagnetic radiation (radio waves) but I think this is wrong.  When Hertz did his original experiments in the 1880s that proved the existence of waves predicted by Maxwell in 1865, he used a spark-gap transmitter and a remote circular receiver.

First question -- How did Prof. Hertz know that the sparks appearing in his remote receiver were not caused (1) by induction (as described by Faraday) or (2) by what today is called "near-field radiation?"

Second question -- if we repeated Hertz's experiment with the circular receiver, but we kept moving the receiver farther away from the spark transmitter, what behavior would we expect to see in the receiver?
Let's say we start with the receiver physically adjacent to the transmitter and then keep moving it away in 1-foot increments.  What response would we see in the receiver at each increment?  Regarding terminology, is it scientifically accurate to describe the energy emitted by the transmitter as EM radiation, regardless of the distance from the transmitter?  Thank you kindly for considering this request for clarification.


texts:
I want to control DC motors with L293D IC using my Raspberry Pi. I wanted to set it up similarily to this:

But then I found one article on Instructabiles, which said that it would work, but correct solution was this:

So my question is, why is the second circuit better? What do the capacitators do? I´m fairly new to electronics, so this may be a dumb question, but I really can´t figure it out.


texts:
I've been trying to interface with my car's info screen, called a TID (Triple Information Display), from Opel.
From the factory, there are multiple things attached to this screen, one of those a line called SDV - Speed Dependant Volume.
I've been able to write to the display using Arduino and the protocol described here:
http://wiki.carluccio.de/index.php/Opel_TID.
One of the information I would like to display on the screen is the current vehicle speed, using that SDV line.
The thing is, I can't get any signal from it. I know it's connected because the display has a test mode where it briefly shows the (correct) speed, but I can't intercept it with the Arduino. I've tried measuring with a DVM but there is no voltage across this line and ground...
There are multiple circuit diagrams online for the kind of thing I'm trying to do, but since I'm just a begginer in electronics, I don't quite understand them. Could someone please try to explain to me the SDV (or vehicle speed sensor) part of these circuits, and the difference between them?

(source: rolandgruber.de)

Upon further reading I understand that the transistor in the first circuit is driving the RA4 port in the PIC.
I found it strange that a port in a microcontroller would be happy with +12v from the battery of the car, but it turns out that port RA4 is an "open drain", being happy with voltages up to 14v.
It seems I won't be able to replicate this circuit with arduino (at least without extra transistors)


texts: PWM Switching of 0-200mA Laser diode driver

texts:
My main goal is to create constant current source as laser diode driver between 0-200mA, controllable by 0-3.3V analog input from MCU,
And can be modulated (ON/OFF only) by square 0/3.3V PWM signal (changeable frequency up to 10khz and DC 0-100% from MCU).
V3 In my schematic should provide the analog 0-3.3V (MCU PWM with MCP4725 PWM to analog)
and V2 should modulate the signal by PWM from MCU.
Attached are schematics of two switching concepts variations(BJT, MOSFET).
I already built the entire circuit with BJT option but since the BJT acted in saturation (the analog input 0-3.3v is smaller than the switching voltage), i received negative current in the analog input power supply and increasing the analog voltage didn't had any effect (does it make sense?)
besides that, rest of the circuit is working.
The MOSFET version use opamp since my MCU is 3.3v and unless it will be fully opened I'll ran into saturation at some point . (is it the right way to increase VGS from 3.3V?)
I'm not sure about high side switching / low side switching , BJT/MOSFET...
Hopefully you will be able to help me solve the switching issue.
and last remark the opamps VCC is 7V since I'm using MCP602 and from the datasheet I understood that's the maximum voltage range.
Thank you!


texts: Why my two coils don't repel each other?

texts: I'm experimenting with two coils. I drive them with two MOSFETs and one consumes around 1A and the second ~0.7A (12V power supply able to deliver 15A). While the coils work with permanent magnets and repel and attract them as opposed, I observe no interaction when I bring them close together. I mean not even a hint of movement. Unfortunately I don't have a way to take a picture of these, the first one is around 1 cm diameter and 50 turns and the second around 2cm diameter and 50 turns. Is the power very limited? How should I estimate electromagnet force in Tesla units, and how to measure permanent magnet (small neodymium) magnetic force?


texts: High side mosfet source voltage does not switch back to ground

texts:
I'm trying to make a buck converter with following circuitry:

I put a PWM in the mosfet driver either with an Arduino nano or an atmega32u4 (same result). The low-side mosfet is not used yet(Gate tied to ground) but is already there since the construct should become 2-quadrant converter in the end.
The exact pieces are:

Mosfets: IPP50R140CPXKSA1

Inductor: TLC/10A-102M-00

Capacitor: simple 1 mF elco

Mosfet driver: TC4432

I'm driving the High Side Mosfet with a 100kHz frequency and a 0,3 duty cycle (for this test. The duty cycle is variable).

Problem:
Here is an oscilloscope picture of two voltages. The yellow curve is the voltage between High-Side mosfet gate and ground. The pink curve is the voltage between the high mosfet source and the ground.

Now, what I do not understand is exactly why the High side Source doesn't go directly back on ground. I think it should because of the 10kOhm resistor on the output acting like a pull down. I do recognize (I think) a RC unloading curve but there seems to be an offset too.

I would like the Mosfet to stop conducting as soon as the Gate signal hits ground, but on the other hand I need this high capacitor because of the quite high inductor too (to avoid resonance problems)

I tried highly reducing the output resistor to 150 ohm (as I want to conduct rather high current, the device will have to work with resistances as small as 1 or 2 Ohm eventually), but the result is not stable at all. Here is a picture I made, but it's actually very changing:

I looked up several scripts on the buck converter topic, but never found mention of this problem, which leads me to believe it's an uncommon one.

In short, here are my two questions:

Why is the High-side source source voltage behaving this way? What don't I get?
How can I get my mosfet to completely stop leading current as soon as the gate voltage is null?

Edit:
For clarification, here is a oscilloscope picture of some things asked about in the comments:

The 9 V supply voltage is in blue.
The driver input is in pink, the driver output in green.

The datasheet of my capacitor is here. By 1mF for its value, I meant 1000uF

Edit 2
Thanks to Trevor_G's comment, I decided to try removing the diode. I began with the Low-Side diode, and the unloading became slower. Then I removed also the other diode.

And here the result with both Diode removed (right picture):

Yellow is the gate ground voltage, pink is the Source voltage of the High-side mosfet, blue is the output by the 10k Ohm resistor

So it does seem my problem comes from the mosfet acting as capacitor and then unloading other the diode. What I need is the source voltage going back to ground (at best avoiding any slow unloading process altogether), which leaves me with the question: how to avoid this capacitor behavior from the mosfet, what could be an help against it?


texts: How to connect the power planes of 2 PCBs with the least stray inductance?

texts: By the nature of my project, I am designing 2 power electronic boards that are supposed to have its high power main voltage and ground plane connected together. Can you recommend a type of connector or a connection design that will provide the least stray inductance?


texts: I have a 9V battery, but I only need to output 4.5V from it. How do I accomplish this?

texts:
This is the circuit I have so far: Falstad Voltage Divider Circuit

simulate this circuit – Schematic created using CircuitLab

As you can see, I tried using a simple voltage divider, but this interferes with the other resistors in the circuit and does not give me the desired voltage. I want to know if there is a way to turn a 9V source into a 4.5V source WITHOUT changing anything in the circuit as it is.


texts: Where to find a frequency doubler that works on signals between 5 and 500 KHz?

texts:
I've found many frequency doublers that work in the MHz range but having trouble finding any for KHz frequencies. I need to take a signal produced from some digital electronics and double the frequency of this signal. Where might I find such a device?

The signal I want to double the frequency of looks like so:

I have thus-far been using an FPGA to read in the signal, remove the DC offset and then squaring the value in order to frequency double it, but the DC offset varies significantly and results in the output signal being not a precise frequency doubling and occasionally outputting at the frequency rather than doubling it.

The power spectral density of this signal looks like so:


texts:
I have purchased an RFID reader that communicates using an RS-232 cable. I have however used an RS-232 to USB adapter to connect it to my laptop. It is an ACM812A RFID reader.

When I open the RFID reader's application and try to connect to the reader it says communication error. So I decided to pull out the Arduino and start seeing what is being transmitted. First, every time an RFID tag is placed near the RFID reader, the reader beeps to say a tag has been detected. The tag's ID is then transmitted via the RS-232 cable to the PC. So I decided to remove the RS-232 cable and connection. I then took three wires and connected it to the reader's RX, TX and GND pins and then connected the RX to TX of the Arduino and TX to RX of the Arduino and also ground.

When I open the serial monitor and when I place the tag near the reader I get the following displayed on the serial monitor for all buadrates. I was supposed to be getting the ID from the tag (like 251458712). When I measured the TX wire of the reader, it is -5.2V. Can someone help me to understand what is going wrong?


texts:
For a project I am currently working on, I need to monitor a VHF radio frequency (RF) channel, using a software-defined radio (SDR) that is connected to a Raspberry  Pi 3B.

I have successfully implemented the receiver, using terminal commands provided by the rtl_fm tool. In addition to this, I would like to perform digital signal processing (DSP) in the form of FIR and IIR filters, to improve the signal quality, however I am unsure of how to proceed, and how to implement these (what tools to use) as the Pi has limited resources.

I would like to also save these received RF signals as audio files, for listening later.

Hoping you all can offer some advice on DSP tools to use for digital filtering on low resource systems like the Pi.


texts: (1) Constant Current and (2) Zero Voltage

texts:
I received power data from groundwater pumps we are currently investigating. However, I have trouble finding out what the issue is in two data sets. I cannot figure out if there is a hardware problem in the meter or something wrong with the power supply itself. Googling various topics didn't help either. My background is only a physics class at university (environmental engineering).

Data1: What I don't understand is that phase C features a nearly constant current over time even though the ones for phase A and B vary and are of similar magnitude. I am interested in the total power and I think this leads to an underestimate.

Data2: How can the voltage of phase A be zero but the power not? And for the line voltages, if phase A features zero voltage, shouldn't phase BC be the only one with a line voltage of around 424 (instead of CA)?

Thanks in advance!


texts: EPS12V 8pin from ATX PSU with two separate 12V rails

texts:
This is your standard EPS/ATX12V connector used for feeding the main processor VRM on a computer motherboard. The two 4pin connectors can be attached together to create an 8pin connector. The top four pins are +12V and the bottom four pins are ground.

I was recently taking a look inside one of my old power supplies and noticed how two of the +12V pins go to one 12V rail and the other two go to the second 12V rail. Then I see this webpage says the name of pins 7 & 8 are 12V2 (if the PSU has a second 12V rail.)

I thought it was a no-no to combine the two separate 12V rails together?
Does the EPS12V connector and main VRM keep them separate or is it no different than taking two wires from separate 12V rails and just tying them together for increased current capability?


texts: How to implement a synchronization signal with AVR (attiny45)?

texts:
In pseudocode I want to do following:

i = 0
state = 0

while (1):

  compareState = readDigitalIn()
  if state == compareState:
    i = i+1
  else:
    i = 0
    state = compareState

  writeDigitalOut(dataVector[i])

In english, I want to reset the counter i every time I change the state of digitalIn-pin.

Is the above a good way of doing this? Does attiny have event listeners or similar?

The ultimate goal is to synchronize multiple pwm controllers in different chips (writeDigitalOut is changed to AdjustPwmFrequency...)

Edit: Can I use interrupts for this? How? Can create an interrupt that fires when digitalIn-pin is changed?


texts:
Sample program to add two numbers using structures -

DATA SEGMENT
  ORG 1000H
  FOO STRUC
    A DB 0FFH
    B DB 0FFH
    SUM DW ?
  FOO ENDS
DATA ENDS

CODE SEGMENT
  ASSUME CS:CODE,DS:DATA
  START:MOV AX,DATA
        MOV DS,AX

        XOR AX,AX
        MOV AL,FOO.A
        ADD AL,FOO.B
        ADC AH,00H
        MOV DS:FOO.SUM,AX
        HLT

CODE ENDS
END START

No errors and warnings
but while debugging AL is assigned with 00H


texts: Light levels affecting IV curves for a Diode

texts:
I conducted an experiment to work out the saturation current under reverse bias for a diode in three different scenarios, ambient lighting, low light levels and high light levels. Is there an equation to relate light intensity to the current for a diode? Or is it likely that in the high light levels the heat from the lighting warmed up my diode and this is why the results have changed?

The diode was custom made in a cleanroom where I study for this experiment. The graph below shows the results I obtained for all 3, I wouldn't trust the results because they don't seem right compared with the 1n4004, oA90 and BZX zener diode we also tested with the same apparatus at the same time.


texts:
Considering that the regular treatment of a fuse is to place it on the positive side, "before" a load, is this just common practice, or is it backed by an actual reason?

Can a fuse be placed on the negative side, "after" a load? Considering that 1, there is a school of thought that current flows from the negative side to the positive side, and 2, current should be equal at all points in a series circuit (which is why a resistor can go on either side of an led and still regulate the current). Is there any specific reason that the fuse is placed on the positive side aside from just convention?

And for that matter, can a fuse be placed in the middle of a circuit?


texts: Why does GSM allocate 200kHz data bandwidth for each mobile phone?

texts:
I read that the human range is commonly given as 20Hz to 20,000 Hz. But GSM channels are carrier frequencies of 200 kHz bandwidth. Is that because of SMS part?

It seems for voice 20kHz must be enough. Why 200kHz?


texts:
I am very confused in the terms of what is the actual difference between kcl and kvl?
I don't want to have a question on a test and not know where to apply kcl and where to apply kvl?
Please help and thanks in advance


texts: How to implement a "rotary switch" like in audio equipment?

texts:
for my current project I'm planning to use an input "device" like this in the photo (don't know its real name):

It is used in a lot of musical instruments and it is like a potentiometer that can be rotated as many times as you want. I think it isn't read like an analog value.
Can someone give me some hints?

Thank you very much.


texts: Explantation for fried charger with Multimeter

texts:
I have a 9v AC to DC wall adapter that I use to power my Arduino boards. The label says it gives 9v at 1000ma but I wanted to test the validity of the label to troubleshoot.

When I connected my probes to the terminals however it said 0 amps and then the green power light on the adapter turned off. After that the adapter would not power anything. I opened it and could not identify any blown or otherwise damaged pieces.

So, before I fry something else like the USB port on my computer :(, does anyone know what I was doing wrong? The multimeter still works and gives valid readings on other things and I have measured chargers before without issues. I have this multimeter from radioshack.


texts: What happened to electrolytic capacitors in the 21st century?

texts:
We can sometimes see decades-old capacitors (such as ones made in the USSR) still working. They are bigger and heavier, but durable and not desiccating. Modern aluminium capacitors serve for about 11 years, if you are lucky, then become dry and quietly fail. I remember early 2000s devices where capacitors failed after 3–4 years of service, and not necessarily low-end devices (one example is E-TECH ICE-200 cable modem worth ∼ 240 USD in 2000). A repair due to failed electrolytic capacitors became a commonplace, something uncharacteristic for 1980s.

Was this 1990s degradation caused by cheap mass production? Or by poorly-tested technologies related to miniaturization? Or many manufacturers just didn’t care?

It appears that the trend is by now reversed, and recent capacitors are a bit better than the ones from 1994–2002. Can experts confirm it?


texts: Should I add extra protection to 74HC4067

texts:
I plan on using a 74HC4067 to add have more analog & digital inputs on my SBC.
The datasheet talks about having built-in ESD. The analog inputs would be fed 1.8V. The digital ones would be fed 3.3V.
I have a nice article on how to protect digital inputs. It mentions current limiting, filtering and external clipping diode.
My interpretation is I don't need the clipping diode because it's already provided by the multiplexer. Additionally, it seems to me that the filtering could be done "after" the multiplexer (so on it's output side), which means I need only 1 filter instead of 16. And I'm not too sure about the current limiting part.
(My use case involves long wires, sometimes beyond 20m).
Can I skip the clamping diodes?
Can I have the filter and the current limit after the multiplexer?

(16 inputs of the MUX go to one analog input of the Arduino... so here the question is what protection does the mux need, and as an extra, what does the Arduino need)


texts: What is the correct way to use voltage from multiple sources?

texts: I was planning on making a usb switch and I figured the most convenient way to power it and any connected devices would be to draw power from any and all connected hosts. From the searching I've done already I determined that I'd want to connect the grounds together, but I'm not sure if my planned way of automatically handling the 5V power is correct. I thought using a diode for each voltage source to prevent backflow would be correct, but I'm not sure if this is the case. Attached is a circuit diagram for how it would work.


texts: When running two devices in parallel is the amperage always split exactly 50/50?

texts:
I have a AC to DC adaptor that outputs 12V 3A.
This came with a USB HDD dock which has two slots.
I want to splice a 12V fan into the wire in parallel so they are both powered by the same wall plug.
Will the fan just use however many amps it needs and leave the rest for the USB HDD dock or will it only be possible for each device to get 12V 1.5A now because they are in parralell?


texts: If the dynamo is given a rotating force, it generates a current that is passed on the battery. Over time, the battery will be filled with energy. is there a backflow in the process?


texts: What is transient intermodulation distortion?

texts:
I've looked at

Op-amp slew rate over frequency
How it is possible to make bad audio amp?
Which op-amp for audio?

as well as several papers about the topic but although I may get the basis of what is is I still can't clear my mind about the topic. I've found it is related to the slew-rate of an op-amp.

What exactly is it?
What causes it?
Can it be ignored if we check some other properties instead?


texts: Why are sparks coming out of the bottom of my Tesla coil secondary?

texts:
I built a very basic tesla coil and I'm getting sparks out of the secondary bottom instead of the breakout point in the top.
The bottom of the secondary is not connected to anything. The top is connected to the coil toroid and a breakout point.
How do I get sparks to get out of the top breakout point?

The coil:

Bottom of secondary:


texts: Powering my Prototype PCB - onboard Regulator or External Supply?

texts:
I'm laying out my PCB for the first prototype of my project. The board is relatively simple as it only consists of two CPLDs (Altera 240Z Max V) and a AT Mega 128L. I am now thinking of laying out the power section but am wondering if I should just power it from an external supply. The supply meets my requirements (3.3V and 1.8V rails) and has enough juice to run the board (2A @ 3.3V and 1A @ 1.8V).

I would really prefer this approach but am wondering if this is a good idea. It keeps the simplicity as it means I don't have to test and pick voltage regulators at this stage. The power requirements may even change in the future depending on my CPLDs. So my questions are:

Are there any drawbacks I should be aware of of this approach? Should the power section be always close to the relavent chips?
Based on the advice from my previous question, I feel I have sufficient decoupling now (0.01uF and 1uF caps on every power/gnd pair with very short loops). But should I include a large capacitor (say, 470uF) and apply power straight to that?


texts: Transistors: Explain the key differences between SMALL and LARGE-signal analysis

texts:
I'm in an electronics class and I feel like this portion of the lecture was covered in a vague manner. I'm not really sure what the purpose of doing either a large or small signal analysis is, and what the difference is as applied to transistors.

Thanks in advance!


texts: How to build large multiplexers using SystemVerilog?

texts:
Note: This question about multiplexers
is similar to but not identical to this question which is about demultiplexers.
I want to build a fully parameterisable multiplexer in SystemVerilog. So far, I know how to build multiplexers of variable widths like this:
module scale_mux #(parameter WIDTH = 1) (
  input logic sel_a,
        logic [WIDTH-1:0] in_a,
                    in_b,
  output logic [WIDTH-1:0] out);

  always_comb
    unique case (sel_a)
      1'b1 : out = in_a;
      1'b0 : out = in_b;
    default: out = 1'bx;
    endcase

endmodule

I also know how to extend this for 4:1 and 8:1 multiplexers. But the number of case statements for large multiplexers will be a lot.
I'd like to build a multiplexer in which the number of inputs is variable. I'm not sure how I can extend this case statement for the n input case, do you have any ideas?


texts: Calculating MOSFET Heat Dissipation onto PCB

texts:
So for my Heated-Glove project, I was thinking of making a series-parallel battery circuit that is powered by the ATMega328p Microcontroller. What this circuit does is charges the batteries using two dedicated battery charging IC's when the micro senses the charger, and that batteries are in series when the micro does not sense the charger. The purpose of this circuit is to balance charge the batteries. the area that are boxed are the represented by the SI7997DP-T1-GE3 Dual P-Channel MOSFET.

Datasheet: http://www.vishay.com/docs/66719/si7997dp.pdf

The input voltage of this circuit goes into a Buck-Boost converter. The MOSFETs that are boxed are the MOSFETs where the Input Current will travel. The purpose of these is to break the series connection of the batteries when the micro senses the charging voltage. The P-channel that have the +5V (1) & +12V/+5V input at the gate of the MOSFET is what will open the circuit. The FET with +5V (2) at the Gate will pull B2 to GND after the Series connection of the batteries have been broken. And finally, The FET with +5V (3) will pull the gate of the connected FETs to GND, allowing current from the charging IC's to flow into the batteries and charge them.

The issue I am having is I am trying to figure out how to calculate the size of copper pad needed to dissipate the minimum amount of heat onto a PCB. The Max input current is (Edit: 5.25A) and the Input Power is 26.25W. Finally, I would rather not use a Heat Sink since I want this PCB to be as compact as possible. How would I be able to calculate the amount of copper needed to dissipate heat from the MOSFET?


texts:
My objective is to send a bit pattern of 1000 bits from one microcontroller (PIC or Atmel) to another one using the SPI method.

How can I visualize the bit pattern so I can find the errors of received bit pattern?

In Arduino serial monitor can be used for this. But I want to know a way for PIC or Atmel microcontrollers.


texts: using the Arduino internal reference 1.1v

texts:
So i want to measure a resistor of around 20 ohm in a voltage divider with an Arduino UNO R3.
Is there any way on an arduino to use 1.1v instead of 5v?
I want to do this to decrease the current, because the resistor to be measured is a small speaker.


texts: What is the safest way to trigger an output?

texts:
I need to trip a 12V output with a signal. In other words, I will send a signal through the output of my microcontroller and this signal will activate its output.

I've figured out several ways to do this, the most common ones being activation with relay or activation with Mosfet. As in the examples below.

My concern is reliability, I need to make sure that the output is triggered. How many drives per day will be needed to ensure that the system supports a large number of activations?

How can I know which of the forms of activation is the most reliable? Which one will guarantee the activation of the output without fail and which supports the largest number of activations?

EDIT-
The load connected to "output12v" is an electronic lock that consumes around 1A.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Why the simulation time of a synthesized netlist depends on the clock period at which it is constrained?

texts:
I have a design which after synthesis at clock 500 picoseconds in dc_shell takes about 2 minutes to run the synthesized netlist against the testbench. The synthesized netlist worked as expected.

After that, I reduced the clock period to 400 ps and synthesized again. Timing is met again with a slack 0.43. This new netlist just took 10 seconds to complete the simulation and all the results are x.

Why is that dc_shell says timing is MET but the simulation is too fast and the results are x. Can someone please enlighten me on this?


texts:
I'm new here and don't know much more about electronics.I need a switch/relay that help me off DC line when AC (grid) line is available and automatically turn on when AC (grid) line is not available.

Some Details here:

We use 12 v car battery for home dc lights and dc fans, because there is energy crises in my country. I want some sort of switch/relay that help me switch off my dc line whenner my AC grid (220v AC) available.

AC= 220 v
DC= 12 v (200AH battery)

6 Lights = 12 v , 5W
3 fans= 12v , don't know watt.

If
AC=0 then DC= 1,  AC= 1 then Dc = 0

Thanks


texts: Calculating the torque value needed to turn an alternator from an electric motor?

texts: I know very general question I am relatively new in this field of study, and am looking to know the formulas or how to calculate what H.P., rpm, and, volt rating needed to spin an automotive or commercial grade alternator and or a flywheel setup for mechanical energy storage?


texts:
I use the following Colpitts oscillator schematic and I always need to put the scope probe on the inverting input of the opamp to make it start. Otherwise I get a DC voltage and no oscillations.

Do you have any idea about what I can do to to have a reliable startup at powerup ?

Thanks.


texts:
Why does the adc_bridge not work when we have an input dc value?
The plot for v(1) appears but v(cmp) is blank.

.model adc_buff adc_bridge(in_low=0.5 in_high=0.5)
v7 1 0 5
Aad1 [1][cmp] adc_buff
.control
tran 0.02u 7u
plot v(1)
plot v(cmp)
.endc
.end


texts: How do I create a secure clamping circuit?

texts:
Clamping is good for transients, e.g voltage peaks. But two issues with clamping is that if you have a linear voltage regulator attached to 3.3v and 3.3v is the voltage regulator output, then that voltage might going to increase.
The other issue with clamping is that if the voltage is negative, then we are going to have negative voltage after the lower schottky diode.
Have a look att this picture.
Question 1:
How can I prevent so 3.3v will not increase(in practice) if I'm using a linear voltage regulator and 3.3v is the linear voltage regulator outut for e.g a microcontroller?
Question 2:
How can I prevent so negative voltage will not appear at the round blue circle? Assume that this is an digital input for a microcontroller. When I apply 24V, then i'm going to have a 1 as digital input. But if I'm applying -24V, then the digital input going to recieve vaccum and become destroyed. Why?
Picture shows 10K resistor and 2 schottky diodes as a transient and high voltage(30V) protection.


texts: quick charge but slow discharge of a capacitor

texts:
I'm trying to find a circuit that will quickly charge a capacitor with a load(led) in the circuit but slowly discharge it (keep the led on longer than it took to turn on).  Is this possible?  Does anyone have a circuit that will do this?

Thanks!


texts: Why does kicad complain about a voltage source not being driven?

texts:
What does it mean to kicad that a pin is driven?

I have a 12V rail connected to a battery positive terminal in kicad. Kicad says the 12V rail is not driven. Why does it say that? In fact, it tends to shift around depending on whenever I redraw the wire and run a design rules check on it. I'm trying to make sure the board has a battery input, when it is drawn up on PCBnew.


texts: Options for 12v battery pack with charger

texts:
I have an amp that requires 12-20v dc power. I'm looking into a solution for a portable battery pack that I can charge while running the amp as well with discharge and overcharge protection.

This is what im thinking:

18v Power Supply --> Diode --> Resistor --> 12v Battery --> Device

Will this charge the battery and power my device while it is plugged in, and then when it is unplugged use the battery as its power source?


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Having never worked with flexible PCB's before I was wondering how much and how often it can be bend? I'm thinking of using a flex PCB inside a pet collar where it would have to fold in order to adjust collar length.

Would a flex PCB be able to cope with this much mechanical stress?

Thanks for sharing your thoughts!


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I have a DC/DC convertor that tales 5V and makes + 15V and -15V rails

My question is how to place common mode chokes to reduce common mode noise. Should I place 3 of them (1 on the negative to Gnd , 2 on positive to GND and 3 on the +15V and -15V) or 2 of them will suffice (1 on positive to Gnd and 2 on negative to GND)


texts: I need to create a delay in my circuit (about a second) and I'm wondering what are the advantages/disadvantages of using a 555 Timer to create a delay vs using a specialized delay IC like the LTC6994? This is the datasheet for the LTC6994: (http://cds.linear.com/docs/en/datasheet/699412fb.pdf)


texts: Help solving thermal runaway in voltage follower circuit

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I'm trying to build a circuit to drive a heating element. In testing a portion of the circuit, I've noticed what looks like some kind of thermal runaway in the Darlington transistor I'm using, but I'm struggling to understand how this is possible.

At first, the voltage at the emitter follows the base quite accurately. As the transistor heats up, the voltage at the emitter runs away to ~22V, and high current. I'm struggling to understand how this is possible - how is the BJT still conducting when there is no forward bias? - and how to fix the problem.
(The 2N6037 seems to be rated to 40W - see attached)
The op-amp portion is for voltage amplification - I apply a signal of 0-3.3V at 3, and am hoping for approx 0-22V at the darlington emitter.
I've tried isolating just the voltage follower circuit and have had the same problem.

(edited to fix missing wire in schematic)


texts: Create a dynamic schematic table of contents in Altium Designer

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Is it possible to create a dynamic schematic table of contents in Altium Designer?
E.g. if I change the name of a schematic sheet, the entry in the TOC changes too (similar to Word).
Or is it possible to create a text string like "=sheetname(sheetnumber)"?


texts: Generating 14V, 12V, and 5V for winbond 8051 chips such as w77e58

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I'm trying to make a way without error to use the fewest digital inputs possible to provide an output of 14V, 12V and 5V on the VPP pin of the winbond microcontroller. The model I will be using is w77e58.

I have seen circuits that only produce 5 and 12V but none for 14V.

The circuit below is my attempt. and the regulator on the bottom right is one the rest of the circuitry. Capacitors will be 22uF/50v electrolytic.

I have calculated the resistors the best I can based on what's available at the local store to achieve the required voltages.

The only issue I have with this particular circuit is that if all inputs to every transistor is logic low then the output will get 15V which might blow up the microcontroller (for being 1V over at the VPP pin)

How do I improve this circuit so my issue no longer exists regardless of the digital input? and it would be ideal if I convered the separate inputs for 12V to 14V to one exclusive input since I won't need both those voltages at the same time.

I also have PNP transistors if that helps.


texts: Detect ring signal using a low pass filter

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I created 2 boards communicating each other like an intercom system. One of them has a button to send a ring signal to the other. The ring signal consists of PWM signals created by an MCU. I want to detect the ringtone by the MCU of the receiver side.

My ringtone contains 4 outer pulses with a period of 300 ms:

200ms of this signal contains the inner pulses with a period of 1.25ms:

So, I want to add a filter circuit to the receiver side of the ringtone and convert the outer signal to a straight PWM signal. Below is an example output

:

So far, I have tried adding an RC low pass filter with a cut of frequency of the outer signal (1/300ms = 3.33Hz). But I couldn't even get close to the example output. Is there anything I misunderstand about the concept since I'm not very experienced in circuit designs?

Regarding my circuit: I just added a series resistor and a parallel capacitor to the node:

Edit: I didn't want to talk about the circuit that handles converting the audio line signal back to the PWM since this is not the subject on this question. But I suspect that my RC filter does not work properly because of that part. I tried the solutions on the answer but they didn't work as expected.

Below is the schematic of my optocoupler side, line input contains the audio signal of the PWM. The audio signal converted back to the PWM by the optocoupler then I get the PWM signal which I gave the screenshots above. But when I add the RC parts to the OPTO_OUTPUT node, PWM signal changes in terms of volts too. Do you think I have a mistake on adding the RC parts?


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I have recently bought a FT2232H mini module breakout board. When I tried to connect it to a computer via usb nothing happened, either on windows or linux. For the latter I checked that the devices listed in lsusb are unchanged. I also checked with two different computers and two different usb wires.

Then I noticed that there is some white dust around all the soldered pins of the chip:

What is this dust ? Is it related to aging of the breakout board (it's written 2010 on the board, not sure if this is related to design or manufacturing) ? And could this make shortcuts among the pins and be the reason of the chip failure ?


texts: With all the LED and fluorescent light bulbs being used now and much more later, do you expect  power companies to raise rates because of lower power factor? Or will they just absorb the cost as they are doing now? Or will they add a device to the meter to measure VAs? It's not much per household but millions of households added together......