texts:
Bit of an unorthodox question I'm sure, but I'm making a balance beam (two rotors on either end of a see saw) with proportional control, and I can't seem to get it to balance at 0.

The proportional gain is controlled via a potentiometer, but there is no 'sweet spot' between oscillation and insufficient motor correction around 0, meaning the beam either oscillates wildly around 0, or the gain is too small and the beam drifts and settles around 5-10 degrees either side. The odd thing is if I set it to go to another angle that isn't 0 it settles no problem.

The values being read from the IMU are fine (it knows it's settling at 5 degrees, it doesn't think it's 0). The sample rate of the IMU matches the update rate of the motors too, so it's not that the I'm feeding the motors old data.

I've tried to take measures to reduce external forces acting on it too, such as the weight of components and turbulence, but to no effect.

I know I can introduce integral control and that will correct against this slight drift, but I'd really like to have this balancing using just proportional - oscillating slightly either side of 0.

My code is in the format:

float error = sqrt(roll*roll);
Positive_esc = 0.15 + (error*Kp);
Negative_esc = 0.3 - Positive_esc;

if(roll<0){
LeftMotor = Positive_esc;
RightMotor = Negative_esc;
}
if(roll>0){
LeftMotor = Negative_esc;
RightMotor = Positive_esc;
}

Where both motors signals add to make 0.3.

I'm aware there's no definitive answer to this question, but I'm just looking for some creative thinking/some things I might not have considered, because I'm fully stumped on this one.

UPDATE to include transfer functions of response:

UPDATE to include graph of response

As can be seen, the beam will sit quite happily around 3 degrees. However, what concerns me is the positive correction when the error is already positive (can be observed most prominently around t=230).


texts: Can we determine if a filter is butterworth or chebyshev from its physical topology?

texts:
Can all analog filters be classified as Bessel, Elliptic, Butterworth or Chebyshev?

Given a physical ladder topology of several stages of {L, C or LC} in {series or parallel}, is it possible to always classify it to one of the above?

(I got this question while trying to design a steep filter by trial and error on spice, and then realized that it has too long response, as a Chebyshev filter would have, so I wanted to optimize it.)


texts:
I found an old 15 GB HDD lying around in a pile of spare computer parts. I decided to see if it would still work because it could be an emergency backup. So I plugged it into my ATX PSU only to find one of the chips on the board had several holes in it glowing red hot and it was smoking. A catastrophic failure! But why? What could cause the IC to fail so badly? The IC glowed for about 30 seconds before the supply tripped off. I have no idea on the circumstances of this failure - I did not do extensive tests, and I didn't examine the drive beforehand.

It was something like this, http://www.youtube.com/watch?v=ni_PA0as47g, but a different IC, and a different drive.


texts: What development boards have good RTOS support?

texts:
I'm looking for a relatively low-cost (<$50 would be ideal) development board with real support for an RTOS. It doesn't matter if the RTOS is manufacturer-supported or a separate project, but I'd like something that is solidly supported (i.e. actually works for multiple people). I've spent some time fixing broken RTOS ports and I'd rather not have to mess with that.

My other requirement is that the development board has to have support for a Linux development environment.

We're looking for something that is specs-wise roughly comparable to the Atmega 2560. (And, in fact, an Arduino Mega 2560 running BeRTOS is certainly one option.)

To give a little more background to the question, last year we built a quadcopter from scratch (i.e. all the hardware, all the code, etc. Nothing borrowed from Arducopter or anything like that). A small budget ($400) had us stuck with an Arduino Pro (an Atmega 328-based board). By the time we had the thing flying, we were bumping up against the memory limit (due to code size) and doing everything we could to optimize so that our PID loops would run fast enough.

The new goal is to redo the control system based on a less limiting micro and an RTOS.

So, to summarize, the question is, what development boards fit these criteria:

Approx <$50
RTOS support
Compatible with a Linux development environment

Thanks!


texts:
I'm a little puzzled about a prototyping style I've seen used recently. Here is an example picture of a circuit made in this way:

Can someone explain the process of making a board like this? Why are the copper traces covered with solder? How are the components connected together and how do they reach an electrical ground?


texts: Dual Float Switches for a Boat's Bilge Pump

texts:
Background:
I work on a sailboat and I'm trying to recreate the schematic for the vessel's bilge pumps.  The typical bilge pump system has one float switch and looks like this (the "Pump and Float Switch" diagram).  The drawback to this design in a tradition wooden sailboat is that it only removes a small amount of water and runs at frequent intervals.  (This drains the batteries and causes excessive wear and tear.)  The existing solution is use two float switches to pump out 5 gallons every hour or so, but the wiring is spread out and doesn't use any recognizable color scheme...  No one around here can quite suss it out.

Specifics:
Two float switches are mounted in the bilge with a vertical separation to create an "upper" and "lower" configuration. The bilge pump will be as low as possible.
Here are the basic rules I want:

Turn on the pump when the upper switch floats (or both switches float, like in reality).
Turn off the pump when the neither float switch is floating.

This is how I assume it works:
(I am not an electrical engineer so I appreciate your patience.)

simulate this circuit – Schematic created using CircuitLab

Will this schematic create the system I expect?  Don't hesitate with any questions, since my post may not be as clear as I think it is and thanks for your help!


texts: Is this relay datasheet incorrect? (Omron G6SK-2)

texts:
I'm using Omron G6 series relays, both the non-latching (G6S-2) and and dual coil latching (G6SK-2) for a few PCB designs.

What I didn't know was that some models of relays give their connection diagrams from the "Top" view (as expected) while some give them from the "Bottom" view (annoyingly, often both of these will be present in the same datasheet).

As such, my PCBS were produced with the polarity of the relay coils reversed. Ouch! And of course, I only discovered this after soldering everything together.

Despite this, the latching relays work perfectly. I'm using transistors to create the ground connection for each coil, using a microcontroller signal to drive the Set and Reset pins high and low to toggle the relays. No problem at all.

Of course, the non-latching relays don't work (as expected).

My suspicion is therefore that the datasheet for the latching relays incorrectly specified "Bottom" view when it should be the "Top" view, making my PCB inadvertently correct. Any value to this suspicion, or is there another reason my latching relays are working despite screwing up the PCB connections?

(Both latching and non-latching coils are driven by the exact same circuits - same transistors, same microcontroller, same resistors, etc. In addition, cutting out the microcontroller and providing a 5V signal to the transistor pins does the same - the latching relay works, the non-latching relays don't.)

Datasheet here.


texts: Batteries have spare capacity when unused for minutes after running out?

texts:
I tested it with NiZN batteries:

After they ran out of power, I measured their voltage. 0.9V.

I waited 15 minutes, measured again without charging, and it was at 1.5V.

I continued operating a CD player, and it ran for three more minutes on the exact same batteries.

How exactly did the battery manage to seemingly get power out of nowhere?


texts: Replacing Antennas for Wireless Communication

texts:
I have been working with NRF modules for some time now. I have been using the 100m rang version as shown here.

They are working great but I want to increase the range, so I have bought the PA + LNA version of the modulue.

I have the receiving NRF module on a drone and the SMA connector and the included antenna is quite heavy and weighs it down to one side.

I would like to decrease the weight of the larger module as much as possible, and have seen some antennas that seem like small strands of wire. Is it possible for me to just desolderer the SMA connector and solder on a "wire antenna" directly?

If I were to replace the antenna and connector of the module, what do I want to look for when getting a good light weight antenna?


texts: Two stepper motors at different speeds using potentiometer and Ardunio

texts:
I am trying to control two different motors using Arduino and some drivers. The problem I have is that using mills() (i need to use timer with out delay due to me wanting more than one motor at the same time) for delaying this motors is usually found in LEDs tutorials, they see numbers in milliseconds so it makes sense how many seconds you wanna blink, I am trying to grab the potentiometer reading and convert it to the right numbers so my motors pulses make sense.
This my code so far:
//1st Motor
int driverPUL = 7;    // PUL- pin
int driverDIR = 6;    // DIR- pin
int spd = A0;     // Potentiometer

// Variables

int pd = 500;       // Pulse Delay period

long previousMillis = 0;
long interval = 1000;

void setup() {

  pinMode (driverPUL, OUTPUT);
  pinMode (driverDIR, OUTPUT);

}

void loop() {

  pd = map((analogRead(spd)),0,1023,2000,50);

  unsigned long currentMillis = millis();

  /* *** The following code works for an LED but i want it for the motor with potentionmeter
  if(currentMillis - previousMillis > interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW)
      digitalWrite(driverDIR,LOW);
    else
      ledState = LOW;

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);

    /* **** OLD CODE THAT WORKED WITH DELAY
    pd = map((analogRead(spd)),0,1023,2000,50);
    pd2 = map((analogRead(spd2)),0,1023,2000,50);
    digitalWrite(driverDIR,LOW);
    digitalWrite(driverPUL,HIGH);
    delayMicroseconds(pd);
    digitalWrite(driverPUL,LOW);
    delayMicroseconds(pd);
   ***/
}


texts:
I've mistakenly ordered some 3V PIC18 L F14K22 instead of the 5V 18F14K22. 3V output is fine for the designed circuit but I need to make a 3V power rail from the available 5V rail.

Since only a couple of MCUs need the 3V power supply I've thought on using a simple resistor divider. Reading the wikipedia article on voltage dividers says any resistor matching the ratio will give the desired voltage but I'm pretty sure current matters when deciding resistor values.

Which resistor values would be adequate for powering a couple of 3V microcontrollers?


texts:
I am currently working on getting my ADUC7024 (ARM7) microprocessor to communicate with me via UART/RS232. I have tried everything and I'm getting really desperate especially since the provided example software is practically 1:1 what I have as code (and it's not working :/) :

The code compiles and runs, the diodes are properly lighting up (though not turning off O.o) but the RS232 port remains empty.

int putchar(int ch)  {                   /* Write character to Serial Port  */

    if (ch == '\n')  {
        while(!(0x020==(COMSTA0 & 0x020)))
        {}
        COMTX = CR;                         /* output CR */
        }
    while(!(0x020==(COMSTA0 & 0x020)))
    {}

    return (COMTX = ch);
}

int getchar (void)  {                      /* Read character from Serial Port */

    while(!(0x01==(COMSTA0 & 0x01)))
    {}
    return (COMRX);
}

int write (int file, char * ptr, int len) {
  int i;

  for (i = 0; i < len; i++) putchar (*ptr++);
  return len;
}

int main() {
    char output1[13] = "Hello World\n";

    // Setup tx & rx pins on P1.0 and P1.1\
    GP1CON |= 0x011;

    // Start setting up UART at 9600bps
    COMCON0 = 0x080;                // Setting DLAB
    COMDIV0 = 0x00b;                // Setting DIV0 and DIV1 to DL calculated 115200
    COMDIV1 = 0x000;
    COMCON0 = 0x007;                // Clearing DLAB

    GP4CON = GP4CONVAL;
    GP4DAT = 0xFF000000;            // P4.2 configured as an output. LED is turned on

    while(1)
    {

        greenLight(1);
        write(0,output1,13);
        delay(2000);
        redLight(1);
    }
}
volatile void redLight(bool state) {
    if (state) {
        GP4SET = 1<<21;
    } else {
        GP4CLR = 1<<21;
    }
}

volatile void greenLight(bool state) {
    if (state) {
        GP4SET = 1<<22;
    } else {
        GP4CLR = 1<<22;
    }
}

void delay (int length)
{
    while (length >=0)
        length--;
}

Oh and "UART doesn't work" means that there is just no visible communication (I tried listening via Putty and HyperTerminal)


texts: Weird error pattern on CC2541, the 8051 core

texts:
I am playing with the debug interface on the TI CC2541. It seems to be working fine, seeing correct chip ID etc.

The interface has a DEBUG_INSTR command that lets you submit and execute an instruction to the 8051 core; it then returns the accumulator after execution.

So I decided to try with the simplest opcode 0x24 which is ADD with immediate.

But it is behaving very strangely. The behavior seems to be depending on immediate value.

If I successively execute the instruction "0x24 0x02" (i.e. increment by 2) multiple times I get the expected accumulator values (1 appears be the initial value):

3
5
7
9
.
.

On the other hand, if I use "0x24 0x01" I get strange behavior:

1
4
4
6
6
7

I.e. as if it is only every other instruction execution that works but that this then adds two instead of 1.

With 2 as the immediate things work as expected again:

3
5
7
...

But with 3 I get:

3
7
9
13

I.e. it seems to be adding only two half the time but then 4 the other time (so after an even number of iterations it becomes correct because 6 is added in total)?!

Again 4 works as expected but 5 yields:

5
11
15
21
...

Again every other iteration is one too low and the other one too high, so it balances out. But this only happens for odd immediate operands?!

I am at a loss to explain this:

Seems the least significant bit is somehow treated specially and is added to some internal register/carry flags which then gets added on the next round. But it doesn't seem from the documentation the ADD instruction would
   behave like this. It's not even the add-with-carry instruction.

Wondering if there's some more fundamental thing wrong in my setup,
   such as my use interaction with debugger interface that means that
   the instruction bytes or its result are incorrectly delivered.

But  still, the interface doesn't seem completely broken because I can
   execute commands and get expected results (checking status bits, chip
   ID etc.) and in this case, it does seem that at least something
   resembling an ADD instruction gets executed, and for even immediates,
   everything works correctly.


texts: different approaches to implementing program counter

texts:
I want to implement the following 32 bit program counter circuit:

and this is my current verilog code:

module program_counter(
     d,inc,ld,clr,
    clk,Q
);

input [31:0] d;
input inc,ld,clr,clk;
output reg [31:0] Q;

reg [31:0 ] q_inter;

always @(posedge clk) begin
    if (clr)
        q_inter = 32'b0;
    else if (ld)    begin
        case (inc)
            1'b0 : q_inter = d;
            1'b1 : q_inter = q_inter + 4;
    endcase
    end
    Q = q_inter;
end

endmodule

I switched the assignments to blocking assignments because I wanted to wait for the q_inter to receive the updated signal before assigning it to Q, as I noticed that if they were non-blocking then it would result in delayed response in simulation.

I was initially trying to do the same thing by changing the q port to an inout port and doing something like this:

module program_counter(
     d,inc,ld,clr,
    clk,Q
);

input [31:0] d;
input inc,ld,clr,clk;
inout reg [31:0] Q;

always @(posedge clk) begin
    if (clr)
        Q = 32'b0;
    else if (ld)    begin
        case (inc)
            1'b0 : Q = d;
            1'b1 : Q = Q + 4;
        endcase
    end
end

endmodule

but it gives me the following error:
"Non-net port Q cannot be of mode inout"

My questions:

1) Can anyone explain why making Q an inout give me this error?

2) Will changing the the assignments from blocking to non-blocking result in lower timing constraints? in other words, will it translate to a less-delayed circuit?


texts:
I am going to create an electronic scale that measures weight (up to 1 kilogram (2.2 pounds)).

For this I will use:

Atmega328p
SSD1306 module
HX711
load cell

I will charge this using USB

For this I will use:

TP4056  + Li-ion ( 3,7 V; 3400 mAh)
step-up DC/DC converter (input 0.9-5 V and output 5 V (if input>3V: 380-480mA))

I plan to put all this on a printed circuit board and...

Have I designed the power correctly for Atmega328p (0.2mA), HX711 (<1.5mA), SSD1306(15mA), load-cell(1.2 ±0.1mV/V)?

Is it normal to use the battery Li-ion ( 3,7 V; 3400 mAh)?

Or maybe you can suggest an alternative!?

I will be grateful for the answer!


texts: Is the impedance control of differential pair traces a transmission line problem?

texts:
I read in an article of design reference that "If the length of the interconnect PCB is greater than 1/10 th of the wavelength, we should consider using the transmission line instead of ordinary interconnect."

Now I have the following doubt:
the impedance control in a differential pair (like USB D + D-) can be considered as Transmission Line?

In the case that if it can be considered as a Transmission Line, can I forget to do impedance control if the differential traces are less than 1/10 th of the wavelenght of Full / High Speed USB and so only worry about the lenght matching?

Second part, considering the above suppose that the length of my traces exceed the general rule of 1/10 th of wavelength, then I should apply impedance control to the differential pair ... For example the 1/10 th is 1.5 cm but my traces are 2.5 cm, can I apply impedance control up to a length of 1.5 cm and then do the routing of the remaining 1 cm freely? (see the image pls)

NOTE: I would like to clarify that my last question about arriving with the differential pair routing with impedance control and then doing it without impedance control is because I found an Arduino Due design where the routing for the native usb of the AT91SAM3X8E is strange, you can not do 100 ohm impedance control in this way (see image) with that geometry in the tracks nearby of pines of MCU.


texts: Why do long cables measured with a VNA show a "drop" in their attenuation curve?

texts:
I'm measuring the attenuation of several cables with a VNA (Keysight N5234A). When I measure the attenuation of long cables (10 m, 30 m, 40 m or 50 m) I realize that a "drop" appears at 500MHz (see the figure below).

I have seen this "drop" in spectrum analyzers due to the change of internal mixing elements. However, usually after Internal Aligments, this drop gets very small.

I suppose the VNA also changes from one internal element to another. However, does anyone have more details about why this happens in VNAs? Is there any way to minimize the size of the "drop"?

PS: I asked a colleague and he also observed this behavior on another VNA that we have, so let's assume the VNA is working properly.


texts: How to determine the rotation direction, rotation angle and rotation speed of a stepper motor and a servo motor

texts:
During one of my lab session I faced this problem and couldn't find any good answer. As far as I know for a stepper,

Reversing the direction of current will change the direction of rotation.
Number of pulses applied at each pole will determine the position.
Frequency of the pulses will determine the speed.

But I dont know how to achive these with a servo. For my understanding servos control speed and direction of rotation on their own.

It would be great if some one can tell whether my understanding is correct or not.


texts: what exactly is biasing in transistors and how to do biasing

texts: I have read that collector, emitter must be reverse biased in CE configuration in npn transistor but how can n and n be reverse biased


texts: How do I pick the right resistor for an optoisolator given a desired current?

texts:
This is a follow up to this question, but isn't specific to the other one.  This is both an ohm's law question and a 'how does one interpret data sheets' question.

I want to minimize the current I use to hold open a relay via a trigger (which only requires 1.2mA) that I need to isolate.  If I use, say, an NTE3083 optoisolator to trigger this relay, how do I pick the proper resistor for the optoisolator's input?   The datasheet says the NTE3083 will trigger as low as 1mA.

But the datasheet doesn't give a definitive forward voltage.  It gives a 60mA forward current, and then has a table that also mentions 1.15V-1.5V and 20mA as part of its characteristics.

If my source voltage is 12V, and I want, say, 2mA to be conservative, how do I get there from here?

Do I just drop the voltage and current (R of the optoisolator would be constant?) by scaling down current and voltage?  So if I want 2mA, divide by 10:  20mA/10 and 1.15V (or 1.5??)/10?  And then calculate the resistor?

((12 volts) - (.1 volts)) / (2 milliamperes) = 5950 ohms

Is that the right approach?


texts:
I have STM32f107 MCU soldered on custom board. I would like to use USB peripheral in CDC mode. I connected pins PA11 (D-), PA12 (D+) and GND directly to a USB cable which leads to the computer. The device is self-powered, thus I don't use VDD pin.

In STM32Cube I created a new project, configured only USB_OTG_FS device and USB_DEVICE in middleware section. Also I configured High-Speed Clock in RCC section so that USB peripheral has 48 MHz clock.

Then I generated the program skeleton and uploaded it to the MCU. Unfortunately it does not work. I think the main problem is that there is no voltage on D+ pin so that the computer is not able to recognize a new device. When I execute the  CDC_Transmit_FS function, the processor falls into the Hard fault.

The strangest thing is that when I configure STM32F429 MCU on Discovery kit in the similar way, the USB works out of the box. I tried to diff the source code, but I haven't found any crucial difference (except the STMF4 MCU uses USB High speed OTG in full speed mode).

Please does anybody have some experience on using USB with STM32F107 and STM32CubeMX program skeleton?

EDIT: When I run the MCU in bootloader mode, the D+ line is pulled to 3V3 - therefore I think the MCU really does not need any external pull-up (also datasheet says this).

EDIT2: Does anybody know what Activate VBUS option in CubeMX exactly do? I can understand it in Host mode, but what does it do in Device-Only mode?


texts: Breadboard with high frequency digital signals

texts:
I'm trying to interface an ADC chip with my FPGA.  The ADC is on a breakout board that fits nicely into my breadboard (.1" pin spacing).  The clock input from my FPGA into the breakout board is 12.5 MHz.  I also have another clock signal going into a pin that's 3 pins away that is at ~1.5 MHz.  I have two questions:

Will the 12.5 MHz signal work in a standard breadboard?
Will the two clock signals interfere?

All wiring is done from the FPGA Dev board to the breadboard with ~3" jumper wires.

Is there anything else that could go wrong?


texts: Looking for a small rectangular non-rechargeable battery

texts:
I'm looking for an off-the-shelf non-rechargeable battery that has a similar dimension to the battery found here: https://www.sparkfun.com/products/731. Ideally, the battery would be rectangular to fit into our form factor, but I can't seem to find anything of this nature. I'm looking at coin-cell batteries, but the round form-factor breaks our design.

Can anyone offer any suggestions?


texts: A question about white noise in a single ended data acquisition system

texts:
A single ended earth grounded data-acquisition board has several inputs. Since it is single ended all input channels share the same ground when hooked up.

The thing is normally if there is no ground loop in the entire system and if I lets say plug in a new channel the other(already connected channels) channels' noise level and standard deviation is not affected.

But recently if I plug in a force transducer amplifier as an input to the same data-acquisition board the other channels' standard deviation increases for example from 0.005 to 0.032 ect. And when I observe what happens in FFT in real time is that when I plug in any of the force transducer amplifier as an input,  other already connected input signals' white noise increases. There is no 50Hz related noise.

I can understand how 50Hz noise or harmonics appear in other inputs if there is ground loop. But in this case I couldn't find a ground loop and the noise type occurs in other channels seems like white noise.

How can this be explained?

Edit related to an answer:

Single-ended daq

Diff-ended daq


texts: Why are there only RGB and RGBW-LEDs, but none with more chips inside one housing?

texts:
In another thread the question emerged, where the LEDs with 5 or more dies of different colours are. (Kudos to Brian Drummond) The background is as follows:

RGB LEDs are very popular for creating colourful lighting effects. In fact, due to the three receptor types in the human eye virtually every possible colour we can perceive can be produced with a red, a green and a blue LED although the LEDs can produce only a very delimited section of the visible spectrum. With three colours it is even possible, provided a perfect mixture ratio, to produce a light perceived as a pure white. The human vision cannot recognise different light sources if they excite the three colour sensing cones in the eye at the same levels. This effect is called metamerism.

However the human can very well perceive the quality of light sources when light is being reflected by coloured surfaces or objects. Because the reflection of light on coloured surfaces is effectively a multiplication of the light spectrum with the remission spectrum of pigments. The remitted spectrum differs vastly for different sources of white light.

To cut a long story short: White light from RGB-LEDs is a mess. If you try to use it for general illumination purposes, colours of artwork are reduced to a greyish mélange and human skin looks like beeing afloat in a quarry pond for a week.

White LED having a blue chip and a conversion layer produce considerably better light for illumination but can't be tuned to produce light with different colour temperatures let alone pure colours.

While there are some LEDs with a white chip and three colour chips in one housing, those usually tend not to address a better colour rendering but to have a higher luminous flux at white light.

So the question with some additional words is:

Why are there no multichip LEDs (5 or more chips) for the production of light with higher colour rendering?


texts: How are physically obtained different rated voltage output -12/24/48 V- for a PMSG driven by a very small wind turbine rotor?

texts:
In some very small wind turbines (less than 1kW) specifications it is reported that the alternator is of threephase AC permanent magnet synchronous type and that the rated voltage could be 12V/24V/48V. The rated wind speed is obviously fixed to a unique constant value.
My questions:
is the rotational speed of the rotor (rpm) always fixed for the rated power and the rated voltage related to a sort of electronic regulator? or is it possible to have different rotational speeds of the rotor for the same rated power using a variable speed control?


texts: How to measure air quality (especially PM2.5) from distance (scanning like a LiDAR)?

texts:
I have a bit of experience in measuring PM2.5 (fine particles in the (ambient) air 2.5 micrometres or less in size) using PMS5003 sensor. This sensor uses laser, photodiode and the fact that the air flow through the sensor has constant speed due to applied fan.

However, this sensor can measure PM2.5 only in one location. I want a device which would be capable of measuring air quality (particulate matter or anything else) from distance. So, in order to make a map of pollutants in the city I wouldn't need to provide sensor for every x meters. I'd like to just locate the LiDAR-like sensor on some high tower and scan some area.

What should I use to build such a device?


texts: Why are diodes being used with these (apparently) AC relays?

texts:
I am trying to understand the schematics for the GA Industries Pump Director 7600 (pages 9-11).

As far as I can tell, this unit operates completely on 120VAC.  Why then are they using diodes with the relay coils? Is the supply being rectified somewhere that I'm missing?

Example:

My overarching goal is to figure out where I can tap into the circuit to get an indicator of the HOA switch position (shown on page 9 bottom right, and page 10 bottom middle).  I need some sort of output which is energized when the HOA switch is in the Auto position and not energized in the Off position, which my PLC can then read. Note that my PLC can accept 120VAC and 24VDC inputs.  I'm also open to using a relay to isolate/convert the signal if that could work.


texts: AC-DC converter to drive a dc motor (treadmill)

texts:
I would like to fix my treadmill.
I have connected a SCR voltage dimmer (WINGONEER AC 220V 4000W) in series with a full-bridge-rectifier (GBPC5006), to the dc motor.
When I move the potentiometer, the motor runs, but it smokes a little bit and smells.
What is the problem? Is the pulsed wave not good enough? What can I do? And why in the data of the motor is written 50/60Hz if it is a dc one?


texts: STM32 CAN Interrupt causes program to jump in infinite loop

texts:
Struggling with this issue for days now and can't find a solution. Maybe someone saw something like this before and can give me a hint.
I have FreeRTOS running on an STM32L4 with different tasks. One of these tasks should handle CAN communication.
In the CAN interrupt enable register (CAN_IER) I set the enable for ERRIE, BOFIE, EPVIE, FMPIE0 and TMEIE. The application ends up in an infinite loop error with the following trace

I figured out that if I remove the enable for the TMEIE (Transmit mailbox empty interrupt enable) the application starts to run normally but also crashes as soon as one of the other interrupts trips (e.g. if a message is received).
Is this something obvious, maybe an issue with my interrupt handling? Or can someone guide me in the right direction?


texts:
Where should I look for a Spice Mextram model for commercial transistors, such as the FMMT415?

or

Should I try a more advanced analog simulation software, incorporating Mextram or similar transistor modelling capabilities?

Context

Since several weeks I have been looking for a good Avalanche Transistor Model, able to simulate an Avalanche Oscillator, for a standard Spice Simulator.

LabCenter Proteus Design Suite,
Altium Designer,
Cadence OrCAD PSpice,
LTSpice,
etc.

The purpose of the simulator, rather than the electrical behavior that can be readily tested by breadboarding, is to test some impedance and charge physical models over an unknown net (to be tested on field), hence the need of having a reasonably good (not perfect) knowledge of how the transistor can operate.

I found the www.diodes.com FMMT415 Avalanche Transistor Spice model, which I never was able to reproduce for the specific the avalanche effect, perhaps because:

The model simply do not implement the avalanche | breakdown, despite of their several switches,
The effect is different to what I expected (the shown curve vs the simulated one),
I was probably unable to reproduce it in the simulator, by putting a controlled \$V_{CB}\$ voltage source and a controled \$I_E\$ current source). Because a controlled Current Source do not allow me to put a Voltage source sharing a node simultaneously (remembering the current source carry a non-controlled voltage),
I should made a sweep in another variable (which one?),
The simulation do not converge for modelling the avalanche. Which I think is false, because neither the breakdown is observed,
Another totally different reason.

The next advanced model in the scale should be the so called Mextram 503 + 504 model series, which brought to me a totally new family of simulators in answer for the Verilog-AMS models for Mextram available in Auburn.edu, at least, new for me:

Cadence Spectre Circuit Simulator,
Cadence Virtuoso Analog Design Environment,
Keysight Advanced Design System,
Silvaco SmartSpice Simulator,
Synopsis HSpice AMS Design,
etc.

At this moment I have not been able to model any of these softwares, but, I am in the right way? Should I seriously start trying these software if I care about the avalanche?

For sure, I am clear on my current need about simulating with a reasonable accuracy, just good and average but not perfect or astronomical, allowing me to have some way to predict what is going to happen in the board, and perhaps make some RF analysis or others, if I would like, in the future.


texts: using oscilloscope in Proteus AVR Simulator?

texts: I'm generating pulses on ATmega32 and I need to see the pulse wave in the oscilloscope in order to check its frequency. So I connect the pin to the oscilloscope channel and the pin blinks on and off but the oscilloscope doesn't show the wave... what am I doing wrong? Is there any other way to measure the frequency?


texts: BCD to 7 Segment Decoder Schematic: Need help fitting in page

texts:
I am working on the schematic for a BCD to 7 segment decoder right now. I understand the logic, but it is the design of the schematic that I need help with.

Here is my schematic so far:

As you can see, I only have three outputs done and I need to add four more. The problem that I am having is everything is so vertical and there is so much white space to the right. I would like to be able to fit in all in one page without having to zoom really far out, because then you can't read the inputs or outputs. I guess I just feel like there is a more simple or efficient way that I can be doing this. In the truth table we are using 1010-1110 as don't cares, and 1111 as 0 for all segments to be off.


texts: I keep blowing my SSR. What am I doing wrong here?

texts:
this is my first post. I'm having a real pain trying to get these little solid state relays to work for me.
This is a DC/DC relay.

http://www.mouser.com/Search/ProductDetail.aspx?R=84134870virtualkey59640000virtualkey874-84134870

I have now blown 2 and theyre 75 bucks a pop and I reallllllly dont intend to blow another. I cannot figure out what I'm doing wrong. My circuit seems to follow the data sheet, and in fact, the relay works for an operation or two, but after a while, the things latch shut and go completely kaput as far as I can tell. The indicator light still works normally when I open and close the control switch but regardless, the main line stays latched and I've verified that it remains latched even when completely removed from the circuit.

I'm using appropriate precautions, I even have a 30A fuse in series and the relay itself is rated at 30A! The data suggests a diode but my loads are DC only so I'm not sure it's necessary. Some insight would be greatly appreciated.

Thank you!

Additionally, does anyone have a better solution than expensive SSR's to this problem? I need to switch a 36V power supply at roughly 20A continuous power. This is for an EV so power efficiency is a concern and so is space. Obviously my plan to use SSR's hasnt been working great so far. Here's an image of my circuit side-by-side the data sheet suggested circuit.

THIS RELAY IS DCDC

Thanks so much for the help!


texts: Charging a small 100uF 450V capacitor with a small battery?

texts:
How can I easily charge a 450V capacitor with a small battery such as a 1.5V or 9V while stepping the voltage up in between so as to provide a voltage near 450V for the capacitor?

I'm looking to charge this capacitor with either pieces I buy or those I build, but I want the materials not including the capacitor and battery to cost me under $20, preferably under $10. If necessary I can take parts out of other devices, but it would be most preferable just to buy them pre-built.

I've looked up what would be necessary and it looks like I'd need a step up inverter from the small DC voltage (probably around 12V) to the large AC voltage(probably around 220V) then I'd need a 2:1 step up transformer to turn the 220V into around 440V and then I'd need another inverter to turn the 440V AC current into a 440V DC current. I might also need 2 of all of these pieces if I needed to down step the Voltage to finish the circuit, but there might be a way around that. In addition to cases for the battery or batteries. The wiring for all this will be bought separately in addition to a switch if that was a question.


texts: Finding the energy stored in a 5uF capacitor

texts:
The current flowing through a 5uF capacitor is represented in the picture. Find the energy in the capacitor at t= 1.4ms, t = 3.3ms, t = 4.3ms, t = 6.7ms, and 5 = 8.5ms.

So ultimately we will use the formula: $$w = \frac{1}{2}cv^2$$ to find the voltage at each of the points of t.

But in order to get the voltage for the equation, we need to use the formula: $$v = \frac{1}{c}\int^{t}_{-\infty}i(t)dt $$

What I'm asking is if theres a specific way to go about taking the integrals throughout the waveform. Do I simply taking the integral from each change, such as 0 to 2, 2 to 4,and so on, creating a waveform from that, OR do I take the integral from 0 to t, which will be $$v = \frac{1}{5}\int^{t}_{0}\frac{15}{2}tdt$$ then looking at 2 to 4, we will have $$v = \frac{1}{5}(\int^{2}_{0}\frac{15}{2}tdt + \int^{t}_{2}15mA dt)$$


texts:
I am looking at a VGA to HDMI conversion circuit, and right near the HDMI connector is an array of these symbols:

By the values posted by these symbols, it looks like some sort of capacitor, but I have never seen this strange backwards-z symbol before, and hours of internet searching have given me no clarity.  Is this some odd, alternate symbol for something common?

Thanks.


texts: I2C differential network architecture using PCA9615

texts:
I'm building an architecture for a large scale robot (3x3meters) and I would like to build a specific architecture around I2C differential to control motors drivers (this should be noisy).
My problem is, in order to avoid high cost cables and connector, to build kind of star I2C network using PCA9615.
Since star network are not really recommended on RS485 for instance, I guess so it should not be ok with differential I2C.
So my idea is to split network like this:

My main board will collect all feedback from several PCA9615.
All twisted lines will be maximum 3m long.
I guess using a I2C switch will solve my solution (for example TCA9548A).
But since I don't have experience in I2C network, I rather ask ;)
So my question is: could it work? Is there a simpler solution?
Thanks a lot !! :)
Note: If I'm not clear enough, please feel free to reprimand me.


texts: How to rule out that you have a faulty power supply?

texts:
Just for context: I'm trying to code an ESP8266-ESP01 through an arduino, but I'm failing and my primary suspect, as per other forum issues I read, is that the power supply is the fault.

I've tried with 2 salvaged power supplies with way 3.2A and 2A vs the 0.2A peak that I need. This regulator lowers voltage to 3.3V.
When connecting the board, voltmeter tells me that voltage drops to 3V or even 2.8V.

In general, what tests can you do to a power supply to decide it's OK or faulty?
Is it enough to see that voltage drops when they have load to say they are faulty?
Are there any ripple or noise characteristics that could get in the way of my ESP8266 that I should measure?


texts: Why can't I get any proper arcs out of this flyback transformer?

texts:
I salvaged a flyback transformer from an old TV and used it in a single MOSFET driver like this:

I used  6 turns of insulated copper wire to make the primary coil with the centre tap and again 6 turns. I found the secondary ground on the flyback and tried drawing some arcs, but to my disappointment all what I got was a 2 mm arc.
Can someone please tell me why this is happening and if there is a way of correcting my circuit for larger arcs?


texts: Controlled impedance traces necessary between line driver and series termination resistor?

texts:
I'm designing a line driver circuit with the SN74BCT25244 chip. The chip has a rise time of ~10 ns into an open circuit based on my own scope testing, but we are only wanting to drive the signal at a frequency of around 10 kHz max.  The circuit goes to a co-ax connector and drives a 50 Ohm cable, connected to a 50 Ohm terminated device. Here's what the series connections of the circuit looks like on my board layout:
line-driver IC -> 24 Ohm resistor -> some cct protection elements (connected parallel, to GND) -> 22 Ohm resistor -> fuse -> coax connector
The total distance from line driver output pin to co-ax connector is about 1.1" (28 mm).
My question is: will I need to use controlled impedance routing on this design from the line driver to all of my other circuit elements and on to the connector?
I'm thinking even if I do, it will be screwed up by the varying widths of the resistors and fuse. Since I have about 50 ohms of series resistance from the line driver output to the co-ax connector, am I OK to use any trace width?
Thanks!


texts: Causes for a burned up flyback diode on a relay?

texts:
I'm repairing a control board for a premium washing machine (model #s at bottom for anyone that's interested).  The machine was displaying an error code for relay failure.  I took the board out of circuit, injected voltage on the DC bus, and detected two shorted 1N4148 "T4" diodes, each in parallel to a 12v SPST-NO relay (marked with arrows below). I replaced them.  Each relay switches one side of the water heating element (+ or -).  I have not tested the repair yet, but the machine does work without issue with a substitute board.

Trying to figure out what may have caused the diodes to short?

Note: After repair

Machine: MHW6000X
Relays:  Omron 12V G2RL-1A-E
Control Board:  W10406607 / W10406604 (alternates, W10342325 / W10342327, W10388205, W10427972, W10384506, W10354088, W10406635)

I found these short diodes using isopropyl alcohol (99%) and a microscope (loupe or optivisor works for less $$).  Here's a video from my microscope camera showing the alcohol

https://youtu.be/w-QVvYimghc

This is one of the larger "neighboring" diodes, MURS160T3G "U1J" in SMB package. Same relay, so perhaps a strange bit of design here.


texts: Why do EM waves with longer wavelengths propagate longer distances?

texts:
AM radio signals use carrier waves which are quite longer than in FM case. We know that in free space both high and low freq. RF signals should take the same distance in same period of time.

There must be a reason why in literature the longer EM waves(as in AM broadcasting case) can travel longer distances comparing to shorter waves(as in FM broadcasting case).

Does that mean "when we use the same power" in a real world application AM carrier signals can travel longer distances? Would FM carrier waves propagate longer distances as AM if much more power is used? Or is that only because AM waves can be reflected at the ionosphere and therefore FM broadcast can never be sent as far as AM? Or is that because short waves are effected by diffraction a lot more?


texts: Understanding test winding in core balance current transformers

texts:
In some cases it is common to see a core balance current transformer with four output wires, i.e., the secondary winding and the test winding as shown below. I'm wondering how I test it. What kind of signal should I inject? Should I inject a current signal that it is induced in the actual secondary?

Source of the picture: T. Novak, L. A. Morley and F. C. Trutt, "Sensitive ground-fault relaying," in IEEE Transactions on Industry Applications, vol. 24, no. 5, pp. 853-861, Sept.-Oct. 1988.


texts: Can the Common Emmiter Amplifier use a PNP Transistor instead?

texts:
This is a simple Class A amplifier using an NPN transistor:

Is there a way this can use a PNP transistor, instead (with only 0V and +Vcc, not 0V and -Vcc)? Why or why not?


texts: Why the triangle reference wave is used in PWM for sine modulation?

texts:
I'm implementing PWM for a three-phase inverter.

The documentation on the subject, especially the technical implementations, is very good but as far as I am able to understand none of the one I read talks about why the reference signal is a triangle or a sawtooth. In one document I found that this type of modulation is the oldest in the game (PWM concerned) so maybe is a thing of old technology that becomes standard?


texts: KCL using phasors: how should we proceed knowing effective voltage/current

texts:
I have the following problem. Consider a circuit node where 3 sinusoidal currents with the same frequency converge, i1 i2 and i3. Knowing that the effective values of i1 and i2 are I1ef=1A and I2ef=2A. What can we say about I3ef:

Options:
$$(a)1A \leq I_{3ef} \leq 3A$$
$$(b)0 \leq I_{3ef} \leq 3A$$
$$(c)2A \leq I_{3ef} \leq 3A$$

My attempt:
So using KCL we have:
$$i_1+i_2+i_3=0$$

Using phasors
$$\overline{I_1}+\overline{I_2}+\overline{I_3}=0$$

where $$\overline{I_i}=I_ie^{j\phi_i}$$

Then
$$I_1e^{j\phi_1}+I_2e^{j\phi_2}+I_3e^{j\phi_3}=0 $$

Because $$I_i=I_{efi}\sqrt{2}$$ then:

$$I_{ef1}\sqrt{2}e^{j\phi_1}+I_{ef2}\sqrt{2}e^{j\phi_2}+I_{ef3}\sqrt{2}e^{j\phi_3}=0 $$

Now I'm stuck in this. I don't know how should I proceed from this to obtain the interval of values for I3ef. I think the complex exponentials are what is bothering me. Can someone help me?

Thanks!


texts:
I don't quite understand this.
Here's a simple RC circuit, consisting of only a resistor and a charged capacitor in series.

where the formulas at work are:

The way I see this, Ir is "caused" by a potential difference across a resistor, while Ic is due to the change in voltage in the capacitor. If these two cancel each other out, will the total current in the circuit be 0, then? I'm sorry if I seem to be missing out on some very basic concepts. Thanks in advance!


texts: Lattice XP2 -- Different voltages for different IO banks?

texts:
As the subject indicates:  can I use different voltages for the different IO banks?   (1.8V for some, 3.3V for some others)
Neither the datasheet nor the hardware checklist technical note explicitly say, AFAICS.


texts: Using DC voltage instead of AC to supply SMPS

texts:
Situation:
You have a battery pack with voltage of 300V. You have some appliances designed for 250V AC. These appliances have SMPS inside.
Claim:
Instead of using DC to AC inverter, you can use DC voltage to supply SMPS inside your devices.
Reasoning:
250V AC has peak voltage around 350V. First stage of SMPS rectifies 250V AC to maybe around 300V DC. This voltage is then used to supply another stage of SMPS, but that's not important for this question. So basically from 2 stage of SMPS onwards, SMPS knows no difference between AC and DC supply voltage.
Advantage:
0 cost of inverter, 0% losses on DC to AC inverter
Disadvantage:
You can use this method strictly just for appliances with SMPS in them.
Question:
Is there something I missed? Is there reason why this would not work?


texts: Can I provide a constant charge to a battery?

texts:
I have a sketch here of what seems like a solid plan.  sketch

I need to provide a .2ohm coil around 3.7v which will take around 20 amps.  The load will be very brief; 3-5 seconds, and intermittent; 10 times per hour.  Manually operated.

I have a battery that is rated for 25a max discharge and is known to be fine with the load.  But I have to take it out and charge it...

I do not need the battery for mobility, but for the amps.  The battery reaches 4.2 volts at maximum charge.  I would like to provide it with 4.1v from a stepped down 5v 1amp power source to keep it topped off while the device is plugged in.

Will this work?  Can I trickle charge a battery and use it at the same time?


texts: How to connect VCC and GND connections of 4050 buffer IC on Eagle?

texts:
I am using a 4050, the schematic uses the triangle representation.

I have added VCC and GND connectors to a power supply of 3.3V in the schematic, hoping Eagle recognizes the connections. However the physical pins on the PCB aren't connected to any net. Also I have tried completing all the buffers on one chip, but no results on finding the connections.

Maybe it should be done manually?
Thanks for the help.


texts: What should the input mpedace of an antenna be, 50 ohm or other values?

texts:
I'm about to match an antenna and a half-wave rectifier using Schottky diode. Both of them are placed in one PCB (PCB antenna). The input impedance of the half-wave rectifier is 6 - j170 ohm at Pin = -10 dBm at the desired frequency, where Pin is the input power to the matching circuit as illustrated in the below figure. The authors in the paper I'm reading tried to match the antenna to that input impedance. My questions are:

If they do so, the antenna will NOT resonate at the frequency the antenna is matched. The goal of matching is to transmit/receive as much power as possible. In this case, it is a receiving antenna. So, will the antenna performance be lower than it would be if it resonates?

Edited: Well, I guess I got my misunderstanding here. For Marcus response, did you mean that once the antenna parameters are fixed as desired, e.g Zin = 50 ohm and S11 = -20 dB @ 900 MHz, the matching network is there, as in the above model, to translate 50 ohm to 6 - j170 ohm which is the input impedance of the rectifier?

Usually the antenna is tuned to be 50 ohm at the resonant frequency. Is it better to do so, compared with the case in question 1?
In practice, do I need a balun when measure S11 / input impedance of the antenna or of the rectifier by a network analyzer? My PCB antenna is a PIFA one, so it is an asymmetric one.

Any suggestions would be highly appreciated.


texts:
I am trying to develop a Matlab code that calculate the RMS error of a digital phase shifter. After writing the code I have used the s2p data provided by different manufacturers and tried to produce the RMS error plot shared in datasheets but this didn't work. The method and Matlab code are shared below. Can anyone please guide or identify the issue please.
The code works with Qorvo's TGP2109 phase shifter s-parameter data.
The method of calculation that I am using is:

Read s2p file.

Find difference from reference state.

Find difference from ideal state.

Square the difference.

Sum all the squared differences

Calculate mean.

Square-root of the mean.
ideal_state = 0;
    mean = zeros(81, 1);                  % Sum of Differences divide by loop value

    sum_of_diff = 0;                  % Sum of Differences

    b = 64;                 % Loop Value

    s21_mag = zeros(81,1);

    RMS_error = zeros(81, 1);

    for a=1:b               % Loop to call "N" number of files

    delimiter = ' ';

    startRow    = 28;

    formatSpec  = '%s%s%s%s%s%s%s%s%s%[^\n\r]';

    myfilename  = sprintf('TGP2109SM_SN09_5v_25C_State%i.s2p',a-1);  %File Name

    filename    = fullfile(<file path>,myfilename);   %File Path

    fid = fopen(filename,'r'); % Open the file
    %Read File
    Data = textscan(fid, formatSpec, 'Delimiter', delimiter, 'MultipleDelimsAsOne', true, 'TextType', 'string', 'HeaderLines' ,startRow-1, 'ReturnOnError', false, 'EndOfLine', '\r\n');
    TB   = table(Data{1:end-1});  %Save Data in Table
    s2p1  = table2array(TB);      %Change Table to array
    s2p = str2double(s2p1);       %Change string to double

    freq       = s2p(:,1);        % Frequency Column
    s21_mag   = s2p(:,4);        % S21 Real Column
    s21_angle   = s2p(:,5);        % S21 Phase Column
    s12_angle   = s2p(:,7);        % S12 Phase Column
    s21_phase = s21_angle;

    if (a == 1)             %Save reference value (i.e. State 1)
        ref_val = s21_phase;      %Save reference value (i.e. State 1)
        state_wrt_ref = ref_val - s21_phase;
        diff = ideal_state - state_wrt_ref;
        sq_diff = (diff).^2;
        sum_of_diff = sq_diff + 0;                 % Difference calculation when loop value is 1
    else
        state_wrt_ref = abs(ref_val) - abs(s21_phase);
        ideal_state = ideal_state + 5.625;                      % Generate Ideal Values of States
        diff = (ideal_state - abs(state_wrt_ref));          % diff calculation of single state
        sq_diff = (diff).^2;                      % Square of difference
        sum_of_diff = sq_diff + sum_of_diff;                  % Add Difference of all states depending upon loop value
    end
figure (1)
line_1 = plot(freq,s21_real,'LineWidth',1.75);
grid on;
grid minor;
title('MAGNITUDE');
xlabel('Freq (GHz)');
ylabel('Magnitude (dB)');

hold on

Legend{a+1}=strcat('State', num2str(a));

ax = gca;
ax.FontSize = 13;

figure (2)
line_2 = plot(freq,s21_phase,'LineWidth',1.75);
grid on;
grid minor;
title('PHASE');
xlabel('Freq (GHz)');
ylabel('Phase (°)');

hold on

Legend{a+1}=strcat('State', num2str(a));
ax = gca;
ax.FontSize = 13;

fid = fclose(fid);

end

RMS_error = sqrt(sum_of_diff/64);

%Plot RMS Error
figure (3)
plot(freq,RMS_error,'LineWidth',1.75);
grid on;
grid minor;
title('RMS Error');
xlabel('Freq (GHz)');
ylabel('Phase (°)');


texts: Can I control/read an RFID reader with an Android device or do I have to put an Arduino board between the two?

texts:
I want to develop and Android app the reads RFID tags. I am wondering if I can control the RFID reader directly with an Android device or do I have to put an Arduino board between the two. The RFID reader I have is called the Cottonwood. Here's a picture of it:

I think these are the commands you can send it:

https://s3.amazonaws.com/linksprite/RFID/integrated+reader/UHF_RFID_integrated_protocol.pdf

Here's a quick start guide:

http://learn.linksprite.com/rfid/cottonwood-uhf-long-distance-rfid-reader-module-quick-start-guide/


texts: Can I have two (or more) different symbols for the same LTspice schematic? How?

texts:
I have two components in my top-level schematic and noticed that the schematics of these components are actually the same.  To avoid any duplication of changes done to these subcircuits, it would be nice to just keep one of them and have the other component just use a different symbol but actually point to the same schematic.

I tried changing the Type field of one of the components to have the same name as the other component, but by doing that, LTspice doesn't open the schematic on double-click any more and the "Navigate/Edit Schematic Block" dialog that pops up when right-clicking on a component is now the generic "Component Attribute Editor" for that component.

Note that I need to keep different symbols for that shared schematic for readability reasons at the top-level.

Edit 1:

Just tried to generate a netlist with the changed Type string, it causes an...

>>> ERROR: Couldn't find schematic for symbol: alternative_symbol_name


texts: Restricting set of logged signals in GHDL

texts:
I have a large VHDL design with hundreds of internal signals. I need to run a simulation of it for a long time in GHDL, and based on a short test run, the resulting VCD dump would be ~50GB for the full run. However, I am only interested in <10 signals.

The GHDL documentation says there is no way to restrict the set of signals recorded when a simulation is run. However, I can be fairly flexible in reorganizing my design, so for example I could wrap components with more layers, etc. Is there a way to use these tricks to restrict the set of recorded signals?


texts:
Cntl + M: Will get you a measurement tool however I wish to make faster measurements.

In kiCad, you can press space bar and it gives a 0,0 origin reference measurment to the cursor. (Displayed on the UI)

Is there such a feature in Altium, I need quicker measurement references than the cumbersome measure tool.

Solved

Shift + D changes the heads up view to add dx dy measurement and INSERT zeros the dx dy origin point to your cursor


texts: Choosing Component / External Power Supply & Arduino 3.3V

texts:
I've made a prototype for a small music player using arduino pro mini 3.3v.

My question relates to powering the device.

I want to be able to use it outdoors, and eventually power it "straight from the mains" (there's an electrician who can help me later with this part) but right now I'm not sure what type of power input component I should be using for the Arduino. So far I've just been testing with a LiPo 3.7v.

Thanks so much for your help in advance!


texts:
I'm using MPU6050 with PIC18F45 protocol I2C. On EasyPIC v6 board its just send me back anything that I put in this WRITE command I2C1_Wr(0xD3);. I replaced the sensor with New One too. Its no good. I'm using MikroC Pro for Programming. My supervisor is forcing me to drop this project can someone tell me the problem with this code please. Here is the Code:

void MPU6050_Activ()
{    I2C1_Init(100000);
     I2C1_Start();
     I2C1_Wr(0x23);   //AD0 TO HIGH NOW ADD IS 0x69 to Write 0xD2 to Read 0xD3
     I2C1_Wr(0x6B); //PWR_MGMT REG ADDRESS
     I2C1_Wr(0x00);  // PWR_MNGMT Reg set to Intenal Clock no Sleep no Reset no Cycle
     I2C1_Stop();

     Delay_ms(70);

     I2C1_Start();
     I2C1_Wr(0x22);
     I2C1_Wr( 0x1B);   //GYRO_CONFIG  Reg
     I2C1_Wr( 0x00 ); //gyro_config, +-250 °/s
     I2C1_Stop();

}

    char text_output[13];
    int data_out;
    unsigned short MPU6050_Read(unsigned short rAddr)
  {
      unsigned short reslt;
      I2C1_Start();
      I2C1_Wr( 0x22 );
      I2C1_Wr(rAddr);  //66
      I2C1_Repeated_Start();
      I2C1_Wr( 0x23 );
      reslt = I2C1_Rd(0u);      // Read the data (NO acknowledge)
      while (!I2C1_Is_Idle()) asm nop;               // Wait for the read cycle to finish
      I2C1_Stop();
      return reslt;
}

void main()
{

     unsigned short read_out;
     TRISC = 0;
     Lcd_Init();                        // Initialize LCD
     Lcd_Cmd(_LCD_CLEAR);               // Clear display
   //Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off

     Lcd_Out(2,1,"LED_ON");
     Delay_ms(1000);
     MPU6050_Activ();
     Lcd_Out( 2, 12, "LCDX" );
      while(1){
       Delay_ms(500);
       read_out=MPU6050_Read(MPU6050_RA_GYRO_XOUT_H);
       IntToStr(read_out, text_output );
       Lcd_Out( 1, 7, text_output );
       Lcd_Out( 1, 5, "K" );

      }
}


texts:
We are in the process of creating a quality assurance & control department at work.
I need to define different tests for the hardware that we make.
The devices are composed of multiple pcbs, with ICs and a micro-controller, using voltage <= 48 DC.

I already have in mind tests such as:

Functional tests
Noise tests (on communication cables)
Temperature test
Surge immunity test

I would like to make the list as exhaustive as possible.
Any help would be appreciated.


texts: Negative feedback with only passive components?

texts:
1) Negative/positive feedback with only passive components, whether this makes sense at all?

Listing the book about signal processing i found


texts: Is it OK to replace a 300mAh tablet battery with a 3000mAh one?

texts:
I want to replace the 300 mAh battery in my Chinese tablet with a new 3000 mAh one. My old battery has three wires: red, black and white. The white one connects to a pad on tablet's board labeled "T". What is the purpose of that wire?

My new battery only has black and red wires, so can I just ignore the white wire and connect the black and red wires? Is there anything I must do after replacing the battery, like resetting he tablet?


texts: Dropping voltage for red channel on RGB LED

texts:
I'm looking at a Multicomp OSW-8349 RGB LED, which has a Vf of 3V min / 4V max for the green and blue channels, and a Vf of 1.8V min to 2.8V max for the red channel, at 350mA. I'm planning on regulating 3.3V to drive the green and blue channels, but would like to avoid using another regulator just for the red one.

Is there a cheap way to cut the voltage for the red LED? I'm considering using the forward voltage drop of a diode to bring it down to 2.6V, but I'm not sure how well this would work, especially with the temperature varying between ~16°C and ~38°C.


texts:
I am new to Processing and attempting to write code to communicate with my Arduino - on a linux platform.

When I run the following code:

println(Serial.list());

I'm supposed to get a list of available ports through which communication with Arduinos/computer is/are possible but instead I get the following message:

WARNING: RXTX Version mismatch
Jar version = RXTX-2.2pre1
native lib Version = RXTX-2.2pre2

I don't know anything about Processing nor why this message is coming up ... I really need help.


texts: LCD SPI interface logic levels and SPI pinout

texts:
I am designing a circuit that includes this LCD and STM32L071 microcontroller.

I have connected the LCD to 3V power net and the microcontroller to 3.3V power net.

To communicate with the LCD, I need to use SPI interface.
So my questions are:

1) As I can see, according to LCD's datasheet, it has only 3 pins of the SPI interface (SCL - clock, SI - serial data, CS). The A0 pin is connected to MCU GPIO. And I see that according to the datasheet the LCD has a command to read the display pixels, so the LCD should send data back to MCU - but on which pin? I assume that the LCD is SPI "slave" device and SI pin is input only. Also, the MCU's SPI2_MOSI pin is route the SI pin. Should I change it because of the LCD's RX?

2) I have found the table below in the MCUs datasheet. I assume that the voltage levels are relevant to the SPI interface too. I'm a little bit confused. An output pin can be TTL and CMOS or can it be configured like a direction of GPIO? How I know if the output pin is CMOS or TTL?

I'm asking this because I want to put logic level translator IC between the LCD and the MCU. And I assume according to the logic levels of the LCD that the LCD is CMOS.

Thank you very much!


texts: Powering hundreds of Adafruit's NeoPixels for a cosplay

texts:
My problem: I am trying to power a project with a 8x32px flexible matrix, 8x8px flexible matrix, 24px ring, 16px ring and 7px jewel (two of each), totalling up to a whopping 734 pixels. For my project I only am using a maximum of 408 though.
Each lit LED at 100% luminosity is either drawing 60mA (white), around 40mA (mixed) or 20mA (primary color). My color is in the mixed area (hot pink) so I used 40mA for my calculations, which already has a little overhead (since no primary color will be at 100% usage).
The amps needed here would be: 408px * 40mA / 1000 = 16.32A
Each unlit LED draws ~1mA, so: 1mA * (734px - 408px) = 326mA
Totalling up to 16.646A.
Now, I could decouple the two 8x32px matrices from this, which would total to 12.88A for them alone and making the other circuit a breeze to power, but those two 8x32 matrices (edit: not the two circuits, sorry for the confusion) need to be in sync, so they need to run off of one microcontroller and preferably one power supply (I don't want three power supplies spread out in my costume, no thanks).
Any suggestions on how I could accomplish this? I have looked through dozens of sites and even thought of using an RC car LiPo battery, but I don't know if that's overkill or even fits in my costume. Any help in this is greatly appreciated and if there are questions requesting more info, I am trying my best to supply it.


texts: How many clock impulses can a passive RFID get in 1 radio signal?Does it even have a CPU?

texts: From what I've found so far, when scanning multiple passive RFID tags at once, collisions will occur so some collision avoidance algorithms like pure aloha and slotted aloha are probably used.What I don't understand is how do passive RFID tags even support these algorithms?Does this mean that they have a CPU?Another thing I don't understand is how does a passive RFID tag know which information bit (serial number for example) to send when it receives a signal from a reader?


texts: How can a remote oximeter meet the standards of EMC?

texts:
An oximeter is a sensor commonly used in medical applications where one needs to retrieve the oxygen saturation of a patient. The reference MAX86141 from Maxim Integrated is one of them :
https://www.maximintegrated.com/en/products/interface/sensor-interface/MAX86141.html
The principle is as follows : the sensor drives an LED at a given frequency, and reads the optical output of a photodiode placed close to the LED. When the patient puts his finger on the LED/photodiode, it is possible to compute the oxygen saturation based on the variations of the reflected signal on the skin.
On the datasheet, Maxim gives strict recommandations regarding grounding these two signals in order to minimize noise.
Now let's take a look at this oximeter :
https://www.healthcare4all.co.uk/contec-handheld-pulse-oximeter-cms-60d
As you can see, the LED/photodiode system is placed close to the finger. The oxygen saturation is computed and displayed on the device.
I was wondering what signals could possibly transmit through the cable, given that EMC must be met in medical appliactions  :

It cannot be the analog signals, otherwise it would be too noisy and the device would not meet the standards of EMC.
They cannot use buses like I2C or SPI which are typically proposed by sensors, because they cannot be integrated outside of the PCB.
There is maybe a microcontroller which transmits the data using a differential protocol like CAN, RS232, RS422, RS485 for instance. However I have opened a remote oximeter myself (which is equivalent to the one on the URL above), and there are only 3 wires in the cable ! It is not sufficient to transmit supply AND a differential protocol.

So... Do you have an idea ? Am I missing a point here ?
Thanks.


texts: Death of Zen (Audio Amplifier) Questions

texts:
I am wanting to build the Death of Zen class A audio amp from Elliott Sound Products. Here is the circuit. I have a few questions:

For all of the capacitors, what should the voltage rating be? I don't want to break them down from a high voltage source.
What should the value of C3 be? Somebody HERE used a 4700µf 35V in parallel with a 10µF polypropylene. Is the polypropylene required?
As a voltage source, I hooked a big transformer through a bridge rectifier through a 30,000 µF, 50 V capacitor and got 36 volts and 34.2 under a 1.33 A load, and 28 VAC from just the output of the transformer.  Is this an OK source or do I need a choke for more filtering?

For the 2 12v Zeners I will be using, how much current should they be rated for? Is 500 mA enough?


texts: Why is RMS used for P=VI (where there are no squares)?

texts:
I understand why RMS values are used for

$$P = {\bar{v^2} \over R}$$

because \$\bar{v^2}\$ would be the "MS" so to speak, and then by square rooting we get the "RMS" (\$\sqrt{\bar{v^2}}\$), which can then be squared to give \$\bar{v^2}\$, meaning the above equation is equivalent to:
$$ P_{av} = {V^2_{rms} \over R}$$

However, why are RMS values used for calculating the average power using \$P = VI\$, i.e

$$P_{av} = \bar{V}\bar{I}$$

In a textbook I see this equation for power for AC written as:

$$P_{av} = V_{rms}I_{rms}$$

Why is the mean of the square values used here when there are no squares in the equation? Surely it should just be the (non squared) average of the absolute voltage and current?


texts:
I've spent the weekend absorbing video lectures from Eric Bogatin and reading his book "Signal and Power Integrity - Simplified"

He states that the the return path for the PCB may be any DC plane which could be a VCC rail underneath the signal path.

Consider the following simple circuit

simulate this circuit – Schematic created using CircuitLab

If U1 and U2 are placed on the top layer and TX and RX are routed only the top layer, then the return path for the signal (TX to RX) would be Vcc. I'm ok with that.

My question is, when the return current reaches just under the TX pin, where does the current go ? At this point does it find its way to Gnd or does it go back into the TX and through the die, back to ground ?

** Added Text from book **


texts:
The output voltage of an astable multivibrator is not a perfect square wave; the voltage when viewed from an oscilloscope tends to resemble a curve. I'm told that this is because the voltage across the capacitors cannot change immediately and therefore the R1 capacitor current somehow disrupts the voltage waveform at the transistor collector. Apparently this can be fixed by isolating the capacitor from the collector using a diode:

Now C1 charges through its own resistor, R2. But I don't understand how the R1 current in the first picture disrupts the collector voltage. When Q1 turns off it's off and therefore above ground. How does the capacitor alter this? And when the diodes are included, how is the situation different? To me it seems that the collector is simply around 0.7 volts lower than the capacitors R2 plate.


texts:
I am trying to drive a 12V motor that has max amps of 15amps.  I am using MOSFET RFP30N06LE.  Can someone explain to me why these are used for motor control when they control the current?  When I use my circuit below, turning the gates on using TTL 5v from an Arduino my voltage on the 12v circuit drops dramatically and the motor barely turns.  What am I doing wrong?  These are TTL MOSFETS from my understanding.

simulate this circuit – Schematic created using CircuitLab


texts: How to create a Retentive/Accumulative Timer from On-Delay/Off-Delay Timers

texts:
According to this post , all timers can be created from just the On-Delay Timer (TON).

At the end of the post, after showing how to create an Off-Delay Timer, an On+Off-Delay Timer, and a Flasher Timing Function, the author states that Pulse Timers, Pulse After Off timers, and Accumulating Timers can also be created from only On-Delay Timers but this isn't shown.

How can this be done?

You can use any basic components, and it doesn't have to be in a single rung but that would be cool.

If you can do it without any timers at all that is also obviously acceptable, and would be interesting.


texts: DRV8889: Unexpected voltage drop at output

texts:
I'm getting some unexpected behaviors when it comes to the voltage and current I see at the AOUTx and BOUTx pins. I must be missing something from my calculations from the datasheet.

Right now, I'm calculating the expected full-scale current as

$$I_\text{FS} = (V_\text{ref}/K_v) \cdot TRQ_\text{DAC},$$

where \$K_v = 2.2\$ and I have \$V_\text{ref} = 1.9\,\text{V}\$ with TRQ_DAC register configured as 50%. Meanwhile, VM = 13.5V with the motor resistance as 17.5 ohms. Since VM = 13.5V, I've set TRQ_DAC to 50% in order to not hit the rails. Given these parameters, I should be expecting a voltage of 7.6V according to Ohm's Law and a current of 432mA given the equation above but I'm getting values (rather inconsistently too) that are over 10% off especially with current. Am I missing part of my KCL/KVL circuit analysis; that is, is there another element in the loop I'm not accounting for? The datasheet makes it seem not the case.


texts: A logic board with two inputs where the state of the output changes upon changes in any of the inputs

texts:
Sorry if my question if very novice. I want to have a simple logic circuitry with two inputs and one output. The state of the output should change if the state of any of the input changes.

The inputs constitute four different states [0, 0], [1, 0], [0, 1] and [1, 1]. The output should change form 0 to 1 (or vice-versa) if the current state of the inputs changes. Thanks for your help in advance.


texts:
I'm trying to pick an op-amp and I'm having trouble figuring out if the op-amp needs a positive and a negative power supply or if I can connect it to ground and the positive supply.

What do I need to look for in the datasheet?

Also, where do I find the "drop-out" of the output compared to the rail voltage?


texts: Inverter Surge Capacity -Technique Behind it

texts:
An inverter's surge capacity indicates how it handles short-term overload before "tripping". Surge capacity is essential to start up some large loads, especially motors that need 2-3 times their running power to get going. The start period may be very short – a fraction of a second

I clearly know the inverter cannot withstand the 3 times of its load for a steady state current ,it can only a transient .

How do the technique attain ? How the circuit desgin ?

Can i use NTC Thermisitor for this purpose ?

Or can i put a time constant (capacitor for saving the over current for transient) accross the current sensing point at the micro controller section


texts: Can I assume that groundings in electrical circuits can be split?

texts:
Assume there's a circuit like this:

What I'm asking is if I can split the grounding points like this:

The reason I want to do it is just for simplicity sake. I don't have an excellent physics background, but the grounding points like these always confuse me when doing calculations. I know that the voltages on all three of these points is equal, although this kind of circuit may create some problems in real life scenarios, I believe it's just easier to read. Will this produce wrong answers for calculating currents and voltages?


texts: How To Eliminate Amplifier Squeal When PreAmp Power is Turned Off

texts:
I have a bass guitar that has a built-in pre amp, which is switched ON whenever the cable is plugged into the bass.  I typically use the bass all day, and leave the amp on and the bass plugged in - for convenience.

The problem is that as long as it is plugged in (whether or not the instrument is in use) there is a drain on the 9-volt battery.

It is not practical to constantly unplug the instrument, so I decided to add a single pole switch that simply cuts the power from the battery to the pre amp circuit.

This preserves the battery life, BUT, when the switch is thrown it produces a pop and short squeal from the bass amplifier (which stays ON while the instrument is not in use).

Would adding a capacitor into the mix solve this little annoyance?  If so, can someone recommend the capacitor value needed?  If not, can anyone offer a solution?  ...or is this simply a bad idea that needs to be abandoned?


texts:
I'm a newbie here. I'm currently planning to make my own prototype board using an ARM chip. So I'll have to get the chip (which I have chosen to be SAM3S4A), and get some other components to support the chip e.g. regulator, caps, resistors, etc. But I am not sure what the components are, for me to get the chip working.
Maybe you can imagine this as a development board like arduino, it has its own core, but it needs supporting components to work. I'd like to make a board like this.

Any one here have ever done something like this? Developing a board out of the core and other components?

I would be really helped if anyone could share.


texts:
I'm got a RC car, which can go forward and backward and it's supplied by ~5V battery. At this moment the circuit looks like this:

and the board can swap + and GRN so the motor can rotate in both ways.

My goal:

How will look the circuit if I wanna accomplish something like this:

And replace the 5V battery with 9V battery ( and add a resistor before the electronics? )


texts: Delayed Switching Between USB Peripherals

texts:
I have two USB sensor pads that cannot be connected simultaneously to the computer. Currently I am using a USB hub with individual on/off switches for each port. To change pads the user MUST turn off one pad and wait for the computer to recognize the device has been removed, before turning on the second pad. Users can confuse the software (not my code, commercial software), if they switch one on before turning the other off or if they do not wait between switching.
To prevent this issue, I would like to present the users with a single momentary button. The connection would be Pad1 and Pad2 connected via USB to switch box. Switch box connected to single USB port on computer. The switch will a standard arcade style reed switch.

Pad1 on. LED indicator on switch box confirms this.
User pushes momentary button.
Pad1 USB power is turned off and Pad1 LED on switch box turns off.
Circuit waits 3 seconds.
Pad2 USB power is turned on and Pad2 LED on switch box lights.

The same process to switch back, 1 button press = pad2 off and pad1 on.
I don't believe I need to switch the USB data, only power?
I have a bucket of caps/resisters and some 555's on hand. Can I create a simple circuit that will operate off the USB source that can achieve what I am after?


texts: Send AT commands from Arduino to Xbee (RX/TX)

texts:
I'm trying to setup some of the IOs on my XBEE SX 868 from my Arduino but yet I didn't achieved for some reasons.
When typing my commands in the Console Log of XCTU, my XBEE is responding and processing it.
When typing my commands in the serial monitor of Arduino, starting with "+++" for exemple, I can see that it has been received on the XBEE console log, but it never returns "OK" to allowing me to continue with AT commands...
If I try to send my commands from my Arduino's initialisation code, using for exemple :
const char *atcmds[] = {"+++", "ATD05\r", "ATWR\r", "ATCN\r"};

// Write the commands to the xbee
for(int i = 0;  i < sizeof(atcmds)/sizeof(atcmds[0]); i++){
 Serial.print(atcmds[i]);
 delay(1020);
}

In the console log, XBEE translates it by a quantity of incomprehensible various symbols..
My goal is to be able to se high or low some IOs of my XBEE in the init sequence of the Arduino, what am I doing wrong ?
Working with an XBEE SX 868 and a Trinket Pro v3
Thanks for the help..


texts:
In AVR programming, register bits are invariably set by left-shifting a 1 to the appropriate bit position - and they're cleared by a ones' complement of the same.

Example: for an ATtiny85, I might set PORTB, b4 like this:

PORTB |= (1<<PB4);

or clear it like this:

PORTB &= ~(1<<PB4);

My question is: Why is it done this way? The simplest code ends up being a mess of bit-shifts. Why are bits defined as bit positions instead of masks.

For instance, the IO header for the ATtiny85 includes this:

#define PORTB   _SFR_IO8(0x18)
#define PB5     5
#define PB4     4
#define PB3     3
#define PB2     2
#define PB1     1
#define PB0     0

To me, it would be much more logical to define the bits as masks instead (like this):

#define PORTB   _SFR_IO8(0x18)
#define PB5     0x20
#define PB4     0x10
#define PB3     0x08
#define PB2     0x04
#define PB1     0x02
#define PB0     0x01

So we could do something like this:

// as bitmasks
PORTB |=  PB5 |  PB3 |  PB0;
PORTB &= ~PB5 & ~PB3 & ~PB0;

to turn bits b5, b3, and b0 on and off, respectively. As opposed to:

// as bit-fields
PORTB |=  (1<<PB5) |  (1<<PB3) |  (1<<PB0);
PORTB &= ~(1<<PB5) & ~(1<<PB3) & ~(1<<PB0);

The bitmask code reads much more clearly: set bits PB5, PB3, and PB0. Furthermore, it would seem to save operations since the bits no longer need to be shifted.

I thought maybe it was done this way to preserve generality in order to allow porting code from an n-bit AVR to an m-bit (example 8-bit to 32-bit). But this doesn't appear to be the case, since #include <avr/io.h> resolves to definition files specific to the target microcontroller. Even changing targets from an 8-bit ATtiny to an 8-bit Atmega (where bit definitions change syntactically from PBx to PORTBx, for example), requires code changes.


texts: How do I know when an amp has virtual ground?

texts:
Well, I´m making "Cmoy amp" (Actually RA1 copy), but I've been stuck in the power management since I saw these:

Here the blogger says that the amp uses a real ground circuit. (And there's also a schematic diagram).

But below that diagram shows that the ground is Virtual ground, and really the only difference between the two schematic diagrams is that one has polarized caps.

I thought that in order to create a virtual ground you needed a couple of resistors. That made me realize that I really dont have idea of when a circuit uses virtual ground or not.

Please help!


texts: Looking for a chip to connect to internet and display text

texts:
I am looking for a small chip that will be able to connect to the internet and display black & white text. I'd like to program the chip to connect to a remote service and display text accordingly. What chips do you recommend? Do you know the prices?

I am not very experienced in hardware of any kind, I hope this is the correct place to post this question.

Thanks


texts:
I recently purchased a filament LED bulb. However, when installed (AC 220V), it wasn't working well: it had a very low light. But sometimes (~ every 5min) it lights up for a few seconds at its normal power.

If the LED was really broken it wouldn't emit at full power, even for a short time. So what can be other problem to check?

NB: Doesn't seem to be a bad contact, it was very deeply plugged in the socket, and other bulbs work well in the socket.


texts: What is reason of having 3 phase in the transmission in cities?

texts: What is the reason of having 3 transmission lines as three phases ?


texts:
My sons birthday present literally went up in smoke when batteries were inserted. I will eventually get a replacement but it will take time and I'd love to be able to fix this as soon as possible. It's a radio controller for a car. It's fairly evident which component has burnt out (not so much if there's other damage), but the burn has made most of the identifying numbers/letters impossible to read. There are no components with the same package on the circuit board to serve as inspiration for what this one might have been.
From the size of the component I am pretty positive it's a SOT89 package but that's where my detective skills end, none of the markings help me figure out what this chip is/was, any help would be much appreciated.

Edit: Addition of picture of full circuit board, component is dead center in the picture, although upside down.


texts:
I understand what they are but i have a few questions...

What are the multi layers on a pcb (i understand 1 and 2 is front back but what about 3, 4 ,5 etc.)
In http://www.youtube.com/watch?v=jzs2Zo_mc4c around 2:21 you can see the some of the board is connected around through copper. Doesn't this power all of the paths at once when the border is connected to power?
Is circuit design the same on a pcb, except for the copper paths acting as the wire?

I'm new to electronics so i also don't have the best understanding about circuits. This is probably why question 2 confuses me.


texts:
Sorry for such foolish question, but what is the behaviour of circuit below:

LED_ON is 3.3V logic control signal, LED_STATUS is output signal to MCU pin (GPIO).
When LED_ON is logic high and Q1 is open LED1 is ON and LED_STATUS = '0', but what will happen when LED_ON = '0'? Q2 will be closed, LED1 will be OFF, but what will be the state of LED_STATUS signal? Will it be +5V (logic high) or floating and why?


texts: Rotating Room by 90 degrees (vertical layout)

texts:
I am working on some simple project in Altium Designer and I have created Power Supply Room:

How do I rotate this room by 90 degrees for following result (following screenshot is result of rotating screenshot, not room itself):


texts:
I have a 5V DC supply that outputs at most 1.5A, and I want to charge a 25F capacitor (BCAP0025-T01) at 2.5V and close to 1.5A.

How can I build a circuit to achieve this? Current mirror maybe?

Apologies if this is lacking in information. Feel free to make assumptions and throw out ideas; I'll be happy to do further research given some leads.


texts: Voltage reference for DAC: is a reference really necessary?

texts:
In section 10 of the datasheet for TI's DAC101S101 chip, it's suggested to use a dedicated voltage regulator only for this chip to reduce noise that digital circuitry could inject into the DAC's voltage reference.

My brain tells me that they're just trying to use an LDO as a low-pass filter.  Why not just use a ferrite bead or inductor to block the HF noise coming from the rest of my circuit?  Will this be less effective than using an LDO?

simulate this circuit – Schematic created using CircuitLab

I imagine that an LDO would be worse because you're limited by how quickly it can respond to errors.  If your MCU is injecting noise at 50MHz + harmonics, you're probably out of luck in terms of LDO response.


texts:
I'm a total newbie on electronics. All I'm able to do is just connecting broken cable here and there :p So this might be dumb question, but I hope it' still the right place to ask this question

Now I'm trying to repair my automatic air refreshener dispenser.
It won't spray out the perfume. I opened the case, confirmed that the power is still flowing well because the indicator lamp is still beeping and even the motor is rotating.

It's just that the motor is too weak to push the perfume sprayer. If I replace the battery to the new ones, it might works for a while (the motor works strong enough to push the perfume sprayer), but after one or a few days, it would get weak again.

So what could be the cause of the problem? Is there any components that I could just replace to easily fix it? the capacitor maybe? or perhaps the motor? or anything else?


texts: Computer case causing interference with TV

texts:
I've recently changed my computer case to a new, bigger case. However, after I changed this case over, I can no longer watch TV due to interference with the signal.

I have removed every output to my computer (e.g. internet, visual, sound etc) which has not changed the affect at all. I have bought a new PSU which did not change the problem.

The aerial is in the loft above my PC but, this was not an issue before I changed my case.

I noticed a change in the interference when I removed my water cooler and replaced it with a stock CPU cooler. The interference then "moved" from the originally affected channels to some lesser used channels.

Could anyone suggest what is causing this interference?

Thanks


texts: Constant current and constant voltage control of inverter

texts: Most of inverters in the grid are based on constant current control where inner current control loop tries to limit the current. Hence acting as a constant current source. I was wondering how control philosophy will be difference if we were to model the same inverter as a constant voltage source?


texts: Why am I measuring the power different than the given rated power?

texts:
There is a solenoid-valve where I measure its resistance as 55 Ohm across its terminals. The photo of its label is shown below:

Above it says 24V DC 8W. But I measure the solenoid's DC resistance as 55 Ohm and from P = V^2/R this corresponds to (24^2)/55 = 10.5 W.
But the label says it is 8W. What can be the reason?


texts:
I'm exploring an Onsemi MC33153 IGBT/MOSFET driver and stuck with this:

simulate this circuit – Schematic created using CircuitLab

When turning SW1 on (closed), Fault pin turns low, Drive stays low (0.4V). Turning SW1 off (open), Fault pin turns high, Drive raises a tiny bit (to 0.42V), which is not as expected. Drain voltage keeps around 15V, which means to me that M1 is slightly open.

This is a simplified version of the "basic" implementation from the datasheet:

I've added R1 to simulate the load and apply some Drain-Source voltage. Measuring the Drive pin in open state (without a MOSFET connected) yields the same results sometimes shows high level (after falling transition on Input), but the behavior is unstable.

Raising input voltage to Vcc (16V) does not change anything, the signal voltage of 3.3V is sufficient for transition (datasheet mentions 2.7V as a threshold).

I've also tried multiple switchings of SW1 back and forth, the behavior did not change.

What am I doing wrong?

Update: Nailed it! Thanks to Tony Stewart and analogsystemsrf I confirm that adding a 1000uF capacitor between Pin6 and FET Source (I suppose this is what's been meant by "decoupling") leads to reliable operation. Removing it raises the Fault signal and disables the Drive right away, so this is pretty much verified.

I've put together the whole circuit (STM32F1 controller, 3 MC33153's and 3 FETs connected) and it works.

For those having the same problem: the placement of a "minus" pin of the cap might be crucial! If this solution doesn't work for you, try moving the pin closer to the FET's Source, it should be between the Source and all other connections to the Ground.


texts: Transformer output voltage calculations using load current

texts:
I can't find formula for this. I have rated load current, acutal load current, rated output voltage and variability of output voltage (given in percentage).

How to find no-load output voltage and output voltage for given load current?


texts: Measuring the charge of a battery while charging

texts:
Determining whether a 12V car battery needs charge is as easy as touching its leads to those of a multimeter. While charging from a vehicle's alternator, the multimeter method fails to determine the battery's state of charge and instead reports the alternator's 14V until the engine is turned off. Only then can we read the battery's voltage again. However, even gauges on older car battery chargers reflect rising voltage over time.

How can I measure the voltage of a charging battery, and how do battery chargers do it?


texts: How many affordable lithium polymer batteries would it take to safely jump-start a car?

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I have a couple of these incredibly powerful 12V battery packs and I got thinking about how feasible it would be to MacGyver an engine starter out of them.

These things are rated on the package to deliver 30C and even higher: For a single set of 3 cells in series a 2Ah 30C cell will deliver 60A.

Consider this specimen: Monster Battery

5Ah @ 65C is 325A, and 5Ah @ 130C is 650A. The 130C max rating seems to indicate that the battery can be discharged in under half a minute.

I'm pretty sure many compact automobile engines can be started with this much current.

My thinking is I could buy a cigarette-lighter adapter, solder it to a beefy 4S battery like the one linked above, and I've got a self-contained car starter with a LOT more power than the pathetic "jump starter" products one might find in a store. With something like this, it basically could not be easier to use, and a 4S lipo won't even get overcharged. Once your car is started, leave it in there and the battery automatically gets topped off. (well 14.4V nominal voltage isn't the most ideal situation but it could be worse)


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We need to connect a small speaker- a headphone one, to an Microchip Pic.
I don't know whats the resistance of such speaker(it's very small) but I guess it's 8-ohm. (We are only using one headphone speaker, not both.)

I know the Pic can output 20mA in a port, so with 5V output and 20mA I have about 0.1W to use, which is good enough (Does not have to be audible to humans, this will be audio-coupled to a microphone).

Not knowing the speaker's impedance or current requirements, I was wondering if connecting them with a 300Ω resistor, directly to the mcu (with a dc blocking component), would produce something, or am I missing something?

Please don't advice an op-amp. I know about them, but am trying to avoid that, because I need a small signal and very small power draw.


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I want to put an exponential voltage source in Orcad / Pspice that \$V(t) = e^t\$.

I used Vexp and I don't know how to set \$V1, V2, Td1, Td2, Tc1, Tc2\$.
I found an equation $$V(t)= V1+(V2-V1)((1-e^\frac{(-time-Td1)}{Tc1} )-(1-e^\frac{(-time-Td2)}{Tc2} ))$$
for $$V(t)=e^t $$
I set \$V1=0v , V2=-1v ,Tc1 =-1 ,Td1=Td2=Tc2=0\$ to so by equation I get
$$V(t)= (-1)((1-e^\frac{(-time)}{-1} )-(1-e^\frac{(-time)}{0} ))=e^{time}$$
but when i put Voltage probe to find graph it doesn't show the correct result.
Does anybody know how should I set the settings to get \$e^t\$ ?


texts: So if my Vin signal is of 50kHz and I want a gain of 50, would this mean that the GBW of the op-amp has to be at least 2.5Mhz? What happens if its below 2.5Mhz


texts: Simple, cheap "Nano-UPS" for 5V/<2A/<10W load (e.g. IP camera), based on 4xAAA batteries (or similar)

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There are many inexpensive IP cameras available these days, most of which run on 5VDC supplied via a USB2 cable. Problem: a power interruption of even a tenth of a second is plenty enough to force the device to restart when power returns, and risks loss of data both through a discontinuity of recording and possible corruption of a local microSD card being used as a recording medium.
Suppose we want to enable such a cam (or a similar small, low-power device) to shrug off a transient power interruption of from 0.1 to 10 seconds at least, and optionally up to 100 or 1,000 seconds, through the use of a minimalist battery backup, or "nano-UPS", which uses a quartet of ordinary AAA cells wired in series as its power reserve. Assume that the device will continue operating as long as it receives a voltage of between 4 and 6 volts. Suppose a power-loss failover starts with a fresh set of AAA batteries producing 1.5 V each, and continues operating until the four cells have each drained down to close to 1.0 V. At a steady combined load of between 2 and 10 watts (0.5 to 2.5 watts per cell), that should take several hours — much more than the few seconds (or less) that will be needed in most instances.
Suppose we wish to construct a bare-bones connection that simply keeps the 4xAAA batteries ready to supply the necessary current instantly (for practical purposes) if and when the primary voltage supply drops below a minimum level (say, 4.2 V). For simplicity, there's no need to accommodate trickle-charging the batteries from the primary supply; let's just assume that the batteries will be replaced manually when they're run down. Let's also assume that there's no need for a DC transformer to regulate the voltage supplied by the batteries; we'll just count on them being in the appropriate range.
The objective here is to be simple, reliable, and compact, so as to be easy to install behind an IP cam, and easy to protect from environmental threats (mostly moisture) when placed outdoors.
What are the minimal components needed to implement such a failover circuit as this, and how should they be assembled with a minimum of fuss (preferably without soldering)?
[For brownie points, please leave a comment if you're aware of an off-the-shelf product already available that provides this functionality, either as described here, or by a different method of similarly low cost and complexity (e.g. small LiPo). Thanks.]


texts: How to calculate voltages on guitar fuzz circuit with pnp and npn transistors?

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I have built this circuit on a veroboard, and it seems to me that it has been wired correctly. I do however get a very low output from the circuit, approx 1/2 to 1/3 of the input signal. I reckon that either I've fried one of the transistors, or I've soldered in a wrong resistor somewhere.

I want to calculate the different voltages that I should be able to measure around the circuit, but I can't get my head around this particular circuit. If anybody could point me in the right direction to find the BE and CE current on Q2 I think I'd be able to figure the rest out myself. Thanks.


texts: How to clamp opamp output to +-12v when supply is +-15v

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I have the following circuit. It's purpose is to take a 0-3.3v signal from an MCU and provide a square, -12v to 12v wave across R3, R4 and either R5 or R6. The idea is to read +-9v when only R4 is connected, +-6v when R4 and R5 are connected, and +-3v when R4 and R6 are connected. The peak-to-peak voltage of the square wave are reduced depending on the configuration of R4/5/6. I have no control over the values of R4, R5 and R6. My problem is that, considering the +/-15v supply, the output of the opamp is somewhere around +/-13.7v. This offsets the values at the "Output" point by a few volts and is out of spec.

I thought of using a rail-to-rail amplifier with a +/-12v supply, but even the rail-to-rail amps can't truly swing to the rails. Also, I'd have to re-work a whole bunch of other subcircuits to work with +/-12v or add a whole other AC/DC converter and I'm not willing to do either.

I then thought of using two back-to-back zeners right after R3, but that would only clip the max voltage, all of the other points would still be too high/low.

Then, I thought of using simple voltage divider for the power inputs of the amp, but that would add 4 resistors to the board and I'd rather avoid that if possible.

In the schematic, assume SW2 has another unconnected pole so that having only R4 in series with R3 is an option.

simulate this circuit – Schematic created using CircuitLab

Can anyone think of how I can limit the output of the opamp to +/-12v and maintain the 9-6-3v ratios with the regards to the output?


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I have designed an Op Amp inverting buffer (gain is 504/600  actually less than 1) stage. This is the schematic:

I seem to have a bump in gain at high frequencies, This is the ac response plot for out2:

Could you help me arrest this issue? having this would mean that my circuit is would amplify high frequency noise.
Thanks!