texts: Trying to measure a pulse width and then send pulse of same width using Verilog

texts:
I am trying to write Verilog code which will measure the width of a pulse and then send a return pulse which has the same width. So far, I have created a counter which counts the number of periods that the input signal is high. I can then take the last number from this counter and multiply it by the clock time period to get the time that the input pulse was high.
The issue I am running into is how to store the count from the previous pulse, generate the return pulse and start measuring the next pulse so that its return pulse can be generated. I know I need to incorporate some type of delay but I am not sure how long the delay should be.
Here is the code and simulation result I have so far.
///////////// HDL Code //////////////
module counter    (
out     ,  // Output of the counter
in_1  ,  // input signal
clk     ,  // clock Input
reset   ,     // reset Input
);

  output [7:0] out;
  input in_1, clk, reset;

  reg [7:0] out;
  reg [7:0] counter;

always @(posedge clk)
if (reset)
  counter <= 8'b0;
else if (in_1)
  counter <= counter + 1;
else if (in_1 == 8'b0)
begin
  out = counter;
  counter = 8'b0;
end
endmodule

///////////// Test bench Code //////////////

`timescale 1ns/100ps

module counter_tb;

//parameter SYSCLK_PERIOD = 20;// 50MHZ

reg clk_1;
reg in_11;
reg reset_1;

wire [7:0] out_1;

initial
begin
    clk_1 = 1'b0;
    in_11 = 1'b0;
    reset_1 = 1'b1;

    #20;

    in_11 = 1'b1;
    reset_1 = 1'b0;

    #50;

    in_11 = 1'b0;

    #100;

    in_11 = 1'b1;

    #100;

    in_11 = 1'b0;

    #50;

    $stop;
end

//////////////////////////////////////////////////////////////////////
// Clock Driver
//////////////////////////////////////////////////////////////////////
always
    #5 clk_1 = ~clk_1;

//////////////////////////////////////////////////////////////////////
// Instantiate Unit Under Test:  counter
//////////////////////////////////////////////////////////////////////
counter counter_0 (
    // Inputs
    .in_1(in_11),
    .clk(clk_1),
    .reset(reset_1),

    // Outputs
    .out( out_1 ),

endmodule


texts: Ribbon Connector And Custom Graphics Card

texts:
I understand how to make a homemade VGA connection using resistor ladders or ICs, like is done in this tutorial. http://dqydj.net/how-to-produce-640x480-vga-color-video-from-an-arduino/

Is there any way to use a similar technique for OLED screens or other screens that use the ribbon connector found in this link? https://www.hawkusa.com/manufacturers/newhaven/displays/50-inch-tfts/nhd-50-800480tf-atxl?gclid=Cj0KCQjw6IfoBRCiARIsAF6q06uI0N-zj1bJUuBG-9u-pUYcoLcYHGXPAqGf0xwXN3Kmw2h32FN31-UaAjt9EALw_wcB


texts: Glitchy pulses in a data acquisition system

texts:
A single-ended -10V to +10V 16-bit data acquisition system is composed of 16 single-ended channels where two of the channels are analog outputs and the rest are analog input channels. The transducers are outputting DC-like low freq analog signals such as temperature sensors ect. Only one channel(channel 7) is carrying pulses from different types of rotating instruments. Output channels output constant voltages during the data acquisition.

The daq board is sampling at 8kHz currently and multiplexing the channels.

I'm having random glitches sometimes. By random I mean 2 or 3 times in 1000 pulses in a pulse train.

Here are some glitchy readings from the pulse channel:

Assuming signal conditioners are not causing this, what could be the problem?

Can it be realted to BNC lengths or multiplexing speed is high due to 8kHz sampling rate? Or output impedance is high? But then I'm observing this kint of glitches when it comes to pulse channel not other channels.

What could be the reason?

edit: I came across this article: http://www.ni.com/white-paper/4494/en/

At the end of it it says:

"When scanning multiple channels at high sampling rates, be careful to notice the settling time and the impedance of the source of each channel. If the source impedance is too high, charges that accumulate on the input capacitance of the DAQ device are not dissipated by the time the signal is sampled. The result of this behavior is that the signal often appears to follow the signal of the previous channel. In this situation, either the sampling rate or the source impedance must be decreased. If the sampling rate cannot be decreased, the source impedance of the signal can be decreased by using a unity gain buffer or voltage follower. When adding a voltage follower to the measurement system, be mindful of the allowable measurement error and accuracy when selecting components and the input configuration for the DAQ device. However, keep source impedances below 1 kW when sampling multiple channels whenever possible"

But I dont know it would be ralated to my issue.


texts: How do I wire a 380v/3 phase bench grinder to run on 220v single phase

texts:
I acquired an old factory bench grinder. It's a 380/220 3 phase 50 Hz unit. Can someone explain how to wire this to run on single phase 220 V (household power)?

I tried simply connecting the blue and brown leads to a 220 V outlet and spinning the unit by hand but that didn't work. I can hear the motor getting power, but it won't spin up.

Click images for full-size view.


texts: How to derive an RC transfer function to plot in MATLAB?

texts:
I recently came across this circuit which modifies a signal going into an ADC.  My gut feeling is that it is some sort of low pass filter but I would really like to derive the transfer function so I can plot the response in MATLAB.

----------------------R2--------------
       |       |              |
Vin    C1      R1             C2     Vout
       |       |              |
--------------------------------------

My nodal and mesh analysis is a little bit rusty so help would be appreciated.


texts: Duplicate headphones control buttons on an adapter

texts:
I want to make an adapter which connects from one side to the TRRS headset plug, on the other side to the audio jack of my smartphone.
The adapter contains the same controls (three usual buttons) of the headset, no mic needed.
If I put it on the handlebar of my scooter it allows me to avoid leaving the handlebar with one hand.
Do you think it's possible to do it without breaking my current headset?
Many thanks


texts: I need to make a PCB, and the only software I have is EAGLE. All the other parts are listed in my libraries, but where can I find a library that has MCP2551 (CAN transceiver)?


texts:
We have a liquid conductivity sensor/meter that can be configured to output its sensor value encoded onto a 4-20 mA current loop. The meter has options of outputting the 4-20mA loop as a linear scale or a logarithmic scale. We need the logarithmic scale so we can get finer resolution at the low end, but still have a wide full range.

When configuring the meter for logarithmic mode, it asked for the following inputs, and I show what we input:

Sensor Min : 0.02 uS/cm
Sensor Max : 2.00 mS/cm
Number of Decades: 4 (wasn't quite sure what to put here)

My question is: based off of these settings, what is the forumula to convert mA back into siemens/cm? I contacted the manufacturer for help, but none of their tech support seemed to have a concrete formula. One of their engineers was able to replicate our meter settings and "simulate" some readings, just to see what the current would measure. This was his table:

1) 4 mA = 0.02 µS/cm
 2) 6 mA = 0.625 µS/cm
 3) 8 mA = 2.00 µS/cm
 4) 10 mA = 6.5 µS/cm
 5) 12 mA = 20 µS/cm
 6) 14 mA = 66 µS/cm
 7) 16 mA = 200 µS/cm
 8) 18 mA = 660 µS/cm
 9) 20 mA = 2000 µS/cm

Based on these numbers, this is my best guess at a formula:

uS = 10^((mA-const)/4)
const = 20 - 4 *log10(uS_max)
uS_max = 2000

But this doesn't give me exactly the same values. The lower end of the scale is also a little bit wonky, because this equation relies on there being a sensor decade every 4 milliamps, but that breaks down at the lower end.

Can anyone help figure out what the conversion formula is?

The sensor is a Mettler Toledo InPro-7000 VP. The meter (the one in which generates the current loop) is the Mettler Toledo M300 (the older version, with buttons instead of the touchscreen).


texts: Measuring the frequency of motor vibration

texts:
I'm using a motor from Adafruit. (Product page link: https://www.adafruit.com/product/1201)

I measured the frequency of vibration with different voltages, but the frequencies are quite different from the frequency shown in the product page. According to the product page, the frequency of vibration is 11000RPM (around 183Hz) with 5V. However, I got only around 58Hz with 5V. I think I did some mistake in measuring the frequency, but I don't know what is the problem.

Here is what I did.

I made a simple circuit with small resistor (1.5 ohm) and a motor. The resistor and the motor are connected serially.

5V was applied between two terminals (A - 5V, B - GND) with a power supply. At this point,  105~110mA current flows through the resistor.
I used an oscilloscope to read the current through the resistor. The oscilloscope showed a wave form.
I calculated the number of peaks for one second. There were around 700 peaks in 1 second.
A rotation of a motor makes multiple peaks in the current wave. The number of peaks per rotation is twice of the number of commutator in the motor. As far as I know, the number of commutator in this motor is 6, so the number of peaks per rotation is 12.
I divided the number of peaks for one second by 12, and got around 58 Hz. That's it.

I think I made a mistake on this process because the number I got is quite different from the number in the product page. Please help me finding the mistake.


texts: Does minimizing full-charge time for Li-ion batteries increase their longevity?

texts:
If the stock charger for my smartphone causes the Li-ion battery to be charged in a couple of hours and I charge my phone for 8 hours a day (while I sleep) resulting in about 6 hours of full-charge time, could I increase the longevity of the battery if I use a lower current charger that results in approximately zero full-charge time (i.e. charging takes about 8 hours)? Or do smartphones take this into account and somehow reduce charging current or flicker charging on and off once a full charge has been reached?

Edit: Changed voltage to current based on the response from Juba.


texts: I get a warning that a latch is generated - why

texts:
When I compile my VHDL code I get following warning:

"ADCStateMachine.vhd":337:4:337:7|Latch generated from process for signal StartRowxSN, probably caused by a missing assignment in an if or case stmt"

Why does this happen and how can I avoid it (I am not very experienced with HDL designs)? This is the code causing the error:

architecture Behavioral of ADCStateMachine is

  [...]

  signal StartColxSN, StartColxSP : std_logic;

  [...]

  -- calculate next Row state and outputs
  p_row : process (DividerRowxDP, CountRowxDP, RowSettlexDI, StateRowxDP, DoReadxS,  StateColxDP, ExposurexDI, CountColxDP, ReadCyclexS, ColSettlexDI)

  begin  -- process p_row
    -- default assignements: stay in present state

    StateRowxDN          <= StateRowxDP;
    DividerRowxDN        <= DividerRowxDP;
    CDVSTestSRRowClockxS <= '0';
    CDVSTestSRRowInxS    <= '0';

    CountRowxDN <= CountRowxDP;

    ReadDonexS <= '0';
    RegisterWritexEO <= '0';
    ADCwordWritexE   <= '0';

    case StateRowxDP is
      when stIdle =>
        if DoReadxS = '1' and (StateColxDP = stReadReset or StateColxDP = stReadSignal) then
          StateRowxDN <= stFeedRow;
        end if;
        DividerRowxDN <= (others => '0');
        CountRowxDN   <= (others => '0');
        ReadDonexS    <= '0';
      when stFeedRow =>
        CDVSTestSRRowClockxS <= '1';
        CDVSTestSRRowInxS    <= '1';
        StateRowxDN          <= stColSettle;
        if ReadCyclexS = "00" then
          StartRowxSN <= '1';
        else
          StartRowxSN <= '0';
        end if;
      when stColSettle =>
        if DividerRowxDP >= ColSettlexDI then
            StateRowxDN   <= stInit;
            DividerRowxDN <= (others => '0');
        else
          DividerRowxDN <= DividerRowxDP + 1;
        end if;
      when stInit =>
        if DividerRowxDP >= RowSettlexDI then
          StateRowxDN   <= stWrite;
          DividerRowxDN <= (others => '0');
        else
          DividerRowxDN <= DividerRowxDP + 1;
        end if;
      when stWrite =>
        if ReadCyclexS = "00" then
          if CountColxDP < SizeX then
            RegisterWritexEO <= '1';
          else
            RegisterWritexEO <= '0';
          end if;
        end if;
        DividerRowxDN <= (others => '0');
        StateRowxDN   <= stRowDone;
      when stRowDone =>
        CDVSTestSRRowClockxS <= '1';
        CDVSTestSRRowInxS    <= '0';
        StartRowxSN          <= '0';
        if CountRowxDP >= SizeY-1 then
          StateRowxDN <= stColumnDone;
        else
          StateRowxDN <= stInit;
          CountRowxDN <= CountRowxDP + 1;
        end if;
        DividerRowxDN <= (others => '0');
      when stColumnDone =>
        readDonexS  <= '1';
        if DoReadxS = '0' then
          StateRowxDN <= stIdle;
        end if;

      when others => null;
    end case;

  end process p_row;

  [...]

end Behavioral;


texts: How to decide on laying out copper area when working with Wifi/RF chips & how to use a guard ring?

texts:
I have seen on several designs that the designer has avoided pouring copper around the RF signal lines and all signal lines in general. Such as seen on the following example. He has also added a "guard ring" around the antenna connector.
https://www.youtube.com/watch?v=14_jh3nLSsU&t=1646s

My question has two parts.

Is there an overall guidline on how to decide to use the copper regions? For instance I usually make it so that the top layer is supply voltage and bottom layer is ground. But I am getting a feeling that what I am doing is horrible practice. But my thoughts are not clear on how to use the copper pour tool in a more educated way. My intuition tells me that esspecially around components sensetive to parasitic Inductance I should avoid it.

How does the guard ring work exactly? And When should I decide on using it?

If you could recommend a resource/ a book to do further reading on PCB design rules, it would be very appriciated.


texts: Capacitor self resonance in a buck converter

texts:
I'm building a 5 V regulator for a PCB, and I was reading through the datasheet and Wikipedia to make sure I was doing it right.

What baffles me is that the regulator switches at 150 kHz. Yet most sources I've found online say the self-resonant frequency of your average electrolytic cap is below 100 kHz.

In the circuit on page 8 of the datasheet, there's a 220 µF electrolytic capacitor. Assuming 2 nH (low estimate) is a reasonable series inductance (is it?), then the highest possible resonant frequency should be

\$ f_c = \Large{\frac{1}{2\pi\sqrt{220e^{-6}\ F\ *\ 2e^{-9}\ H}}} = \small240\ kHz \$

So at 150 kHz the capacitor should barely be working as a capacitor. How does this even work? Why is it OK?

I did some simulations of the circuit to figure out what exactly was going on. I modeled the switch/diode as a 12 V square wave with duty cycle 5/12 = 0.417, and with a load of 5 ohm (for a 1 A current). The output capacitor is 220 µF, the inductor is 33 µH. First I made a Bode plot:

The bottom circuit is using an ideal capacitor (no ESL/ESR). It's basically a low-pass filter with a resonance at 11k radians (1.8 kHz). The top circuit is with an ESR of 100 mohm, ESL 20 µH. The ESR smooths things out at the resonant frequency. The ESL (self-resonant at about 75 kHz) causes the response to flatten out at around 75 kHz, and reduces the attenuation from -40 dB/decade to -20 db/decade.

And then I simulated it with SPICE:

The top trace shows the ideal capacitor. Simulated over 3 ms, it rings at the resonant frequency of the filter (1.8 kHz).

The second trace shows the capacitor with parasitic effects included. It flattens out after a couple of milliseconds, although in the first millisecond the voltage shoots up to 9 V, and the current (not shown) peaks at 12 A, which might be a good reason to include some overvoltage protections.

The third trace shows the output voltage oscillating at around 5 V (also the voltage across the capacitor). The fourth trace is the instantaneous voltage across the series inductance. The fifth trace is the current through the capacitor.

So at these frequencies, the capacitor is indeed almost self-resonant. The impedance across it is almost entirely ESR (100 mohm). The impedance of the ideal capacitor part is 5 mohm; the impedance of the series inductance is 2 mohm (both negligible). But it still drinks up all the oscillatory current, because it is 0.1 ohm in parallel with a 5 ohm load. This is exactly what the capacitor is intended to do.

The fourth trace illustrates the effect of the series inductance. Across it is a mere 7 mV. The capacitor impedance contributes something similar. Out of 60 mV ripple, this is nothing -- but if the frequency were higher, then the overall impedance of the non-ideal capacitor would be higher due to the parasitic inductance. You're fine until the impedance of the capacitor becomes a significant portion of the load -- when that happens you get a large oscillatory current through the load, and that's bad.

This also illustrates the reason why the ESR is such an important parameter. If it's too low, then you don't damp out ringing of the LC circuit and your circuit has stability issues. But the higher it is, the more oscillations you'll get on your steady state voltage.


texts:
I need to control a DC motor with an Arduino. The motor needs approximately 9-12V and 200mA (700mA peak current). I use a 9V battery or a power supply, a transistor (BD135) and a 250 Ohm as base resistor. The following diagram illustrates the circuit - note that R2 is the DC motor and the flyback diode is missing in the diagram, but I used one:

The Problem: I need to be able to stop the motor much more faster than with setting. I read about shorting out the motor's wires or even to turn the motor in the other direction. I've found an explanation, how to control the direction of the motor using 4 diodes and two transistors, but I'm unsure how to try shorting out the motor's wires.

Can I really just connect the two motor wires to a second transistor to stop the motor? How much current/voltage will flow through this transistor?


texts: what is the ideal number of contacts to be placed in NMOS and PMOS when drawing layout in Cadence virtuoso

texts:
I am trying to draw a layout for inverter and i am not sure about how many contacts to be placed in the diffussion region of NMOS and PMOS and what is the reason behind selecting that particular number of contact?

I am using Cadence Virtuoso tool for layout editing


texts: 2n2222 transistor control motor from raspberry

texts:
I'm new and i know almost nothing about electronics (i'm a programmer).
I have to control a DC motor by using a transistor with a PWM pulse given by my raspberry.
This is the scheme i thought about, is it correct or will i burn it all?
The motor used is: www.amazon.com/Yeeco-Electric-Torque-Engine-Machinery/dp/B072HDDSHG


texts:
I'm kinda new in this and I was wondering if I could get some help.

I am trying to build a AC-DC converter, through a full wave rectifier.
Ideally a 220V AC source, freq: 50hz stepped down to 22V AC and rectified to a DC voltage but I'm struggling to get a definite formula to calculate the smoothing capacitance.
I was planning to channel the output of the rectified DC to a 7812 voltage regulator.
Thanks in advance.


texts: How can I measure the charge of a rechargeable cell?

texts:
I'm using a bluetooth keyboard which need four AAA batteries. After the cells are charged (at least according to the charger), the keyboard still doesn't work properly; there is a green LED that should stay lit for a few seconds, but it's red and blinking instead.

I'd like to know if the cells are actually charged.
The battery specification is: AAA, 1.2V, 1000mAh. Once charged, my voltmeter reads 1.43V on each cell.


texts: How to get rid of 19kHz electrical fields

texts:
The mains of my German flat has 19kHz electrical fields on hot, neutral and! ground wire.
I don't have to get rid of them entirely but I want to achieve 20dB reduction while sitting in front of my computer with grounded power supply.

How to achieve this goal?


texts: Choosing a resistance for volume (input side) potentiometer

texts:
I've seen other questions and answers here on choosing resistance values for potentiometers in audio circuits (headphones, speakers, amps, etc.) and have heard of a "4 to 10 x's the target load" rule, but continually hear people suggest values between 50 and 100K ohms, and have become confused because the impedances and location of the pot in the circuit vary so much.

I'm hoping for a fairly straight ahead answer: I have an amp that delivers 30W to each of the two (2) channels. Each channel contains a crossover composed of a 6 ohm and a 4 ohm speaker in parallel with each other. I can draw this full circuit out, or provide more amp specs if necessary.

To add a simple volume knob between the source (a phone or ipod) and the input jack of the amp, what is the logical process for determining a resistance value, and type (Lin/Log)?


texts:
I have a project that has 48 various lengths of WS2812B RGB tape strips. All 12V.

Here is a link to the tape i am using. datasheet

I seem to have a lot of flickering at the ends and the occasional flash or artifact when running animations.

I am not sure what the issue is, i cant tell if it is voltage or signal. What can i do to determine where the problem is?

Does this sound like common issues with this tape?
Thanks,


texts: I have a 11.1 V Li-ion battery pack that I use for a 9-12V device as backup power. When I charge the battery pack, it draws 1-1.25 A of current from the DC charger which has caused more than 1 charger to burn up. How can I limit the current to 0.5 A? I tried using a 47 ohms resistor in series with the battery but it dropped the current to 10 mA. What am I doing wrong?


texts:
I'm trying to create a switch between a -15V and +15V supply using a gate signal of 0V to +3V.

With the positive-going Gate voltage, I tried an NMOS FET. This works as expected with a drain of +10V but with a drain of -10V the FET just acts like a diode, dropping only 0.6V across itself or nothing.

Is there any transistor suitable for this application or must Vg always lie between Vd and Vs? Also, I'm also trying to keep the circuitry as minimal as possible.

Edit:

To further explain my problem: I need to discharge a capacitor at a specific time (when an IC turns off) clamping it to ground, otherwise other voltage lines held up by capacitors begin to leak into it causing havoc (specifically the negative voltage line). Obviously this shouldn't be allowed to happen however the leakage problem is currently out of my control hence why I'm trying to come up with a fix just in case I'm stuck with it.

Also, the level of the GPIO control signal can be active-high or active-low.

I've had some joy by using a single JFET but it's not as good as a MOSFET as the JFET conducts more than a MOSFET when it's "off". I'll take a look at level-shifting.

simulate this circuit – Schematic created using CircuitLab

The line I'm trying to deal with "VCOM" actually travels between -15V and +15V during it's normal operation and ends at 0V. However, as I explained above, it won't stay at 0V after it's operation which is why I'm trying to crowbar it to ground on demand.


texts:
I plan to permanently mount a multimeter in a circuit to measure current.

Since the multimeter is put in series in the circuit, will the circuit be open if the multimeter is turned off?

The print on the multimeter states "5 A max, unfused, max 10 sec every 15 min". Since the current is around 350 mA, it only generates about (0.35/5)^2 < 0.5% of the max allowed power, can I leave the multimeter permanently in series?


texts: How can we generate a specific (non periodic) digital signal in Multisim?

texts:
Could someone please tell me how to generate a specific digital signal in Multisim ,other than the ones provided by the function generator , like this one for example :

I've tried to use the word generator but it was unsucessful.

Any suggestions ?


texts: My lecturer said that, for any system where the amplitude response varies with frequency, such as for an op amp, there will necessarily be a frequency-dependent phase shift between the input and output to prevent causality violation. I believe this effect is named after someone, or at least has a specific name, but I cannot seem to find what it is. Would appreciate if someone could point me in the right direction so I can look into this further!


texts: Implementing an ADC Interface to connect to a FPGA

texts:
I want to implement an ADC Interface for an ADC - ADS 7230 (TI) in VHDL.
I am not very familiar with ADCs to implement it in VHDL. I already have
an ADC Interface for a 10 bit ADC (MAX 1030) and a 12-bit ADC (LTC1407).
Unfortunately these are in AHDL.

Is it possible to use any of the existing ADC interfaces and adapt it to
suit ADS 7230 in AHDL itself? If yes, what are the necessary details I
should look into from the data sheet to change the existing ADC
interface available in AHDL?

Or do you have any other suggestions to implement an ADC interface in
the quickest possible way?

Is there any link where I can get a reference of a 12-bit ADC in VHDL
similar to ADS 7230?


texts: DRAM - is data pins order important when routing on PCB?

texts:
Quick question: I have SDRAM (SDR) and trying to connect it to uC.

Can I route data bits from SDRAM to uC in any order? So they aren't connected respectively (d0->d0, d1->d2 ... d15->d15) but in any order (like d0->d5, d1->d13 etc)?

If I understand correctly it shouldn't matter - if I write in that order and read in the same it should be ok. Am I right?

(I know that it doesn't apply to address bus because of burst-read, columns/rows etc).


texts: Vbe vs Ic characteristics of NPN transistor at different Vce in active region

texts:
Below is an NPN transistor characteristics for Vbe versus Ic at different Vcb or Vce:

It seems like in the active region, Vbe vs Ic curves gets steeper with an increasing Vce.

The following equations relates Vbe to Ic in detail:

But from the above equations how can we conclude that the above curves become more steeper with increasing Vce?

The first part of the equation(Is) has many dimensional terms. Does any of them changes when the Vce increases? I want to relate the effect of Vce to the above curves through the above equations..


texts: Why is my LC circuit resonant frequency way off?

texts:
I'm very new to oscillators but very keen to learn more so I connected this very simple circuit:

where the voltage source is my signal generators and I have an oscilloscope connected across the capacitor.

Here is a picture:

The formula to calculate the resonant frequency is:

$${\displaystyle f_{0}={\frac {\omega _{0}}{2\pi }}={\frac {1}{2\pi {\sqrt {LC}}}}\,.}$$

My inductor has a value of 100uH, and the capacitors is 100uF, so the formula gives the resonant frequency of around 1.6kHz. For a parallel LC circuit, this should give the highest impedance for the circuit, so therefore the voltage reading on the oscilloscope should be the highest at this frequency.

However, this is not what I'm observing. The highest voltage seems to be at around 4.7kHz:

It has about 440mV volt peak to peak (the signal generator is set to 2V) while around the calculated resonant frequency:

The voltage is around 340mV peak to peak, much lower value. For higher voltages than 4.7kHz, the reading is smaller again.

So what am I misunderstanding/doing wrong? I understand that a basic LC circuit is not an ideal filter, but how is the measured resonant frequency so different from the calculated one?


texts:
I am helping a friend who has an AC motor that was originally wired to run on 220VAC but from the looks it is wired to use two capacitors to (somehow) convert a single phase to a 3 phase... the goal is to use a VFD to control its speed/ramp rather than just on/off.
I looked online and found a few pages (like this one) that discuss how a capacitor could have been used (and perhaps one is a start and the other a running cap?), but I am somewhat stumped about having 8 wires rather than the 6 I was expecting for the VFD. I understand that there are Y and Delta configurations where the coils are either in series or parallel, but that would mean 9 wires..? Am I missing something?

Here's an image:

Unfortunately I have no mfg# or any specs... wires are also, annoyingly, not labeled.

Any idea on how I would go about figuring out what wire is/does what? I can measure resistances and inductance, but that is about it. I didn't want to hack at this any more than I need to before I have some strategy... but I suppose I could open it up in the hope of seeing something obvious? What I'm really after, is to get feedback on a good approach to determining what each of those wires does and then how I would go about connecting them to a configuration that is suitable for a VFD.

I'd greatly appreciate any thoughts on this...
Thx,
J


texts: Refreshing flash memories. Does it work?

texts:
We all know that the flash memories have data retention time of around 10..20 years.

But what if we need to design a device that has to work for 1000 years?

The obvious solution is to make a flash reprogramming once every 5..10 years, refreshing the charges in the memory cells. If the flash memory has 100K writing cycles life, it makes 500K..1M years retention time. Almost infinity.

But the obvious way is not always the right way.

So, is it possible to prolong the data retention time of the flash memories almost infinitely, by reflashing it every 5..10 years?


texts:
"An active device or component is something which can provide an infinite energy or non-zero power for an infinite interval"

I learned this definition for an active device in a book, which is valid for capacitor, inductor and batteries (I have evaluated). I was wondering what is a "PN junction", "junctions of a transistor", "OPAMP", "JFET", "MOSFET"? I mean what are the above mentioned devices inside the quotation marks? Are they active devices or passive? If either one then please provide explanation for my understanding.


texts: How do I diagnose the programming interface to a MSP430 i2030 using launchpad?

texts:
I have to use MSP430i2030 for a project and I tried burning code on it using MSP430G2553 launchpad. I tried burning a simple code on toggling the LED, however, the CCS complained that it could not find the chip, yet I could see the LED being toggled. But no matter what changes I make to the code, it keeps on toggling (even when i commented that part of the code). Below is the way in which I connected my chip to the launchpad.

Can anyone please suggest an appropriate way to connect the chip to the launchpad? How do I setup the interface correctly?

Also, as per Texas Instruments, this chip cannot be used with the launchpad, however, I have gone through some examples where people are able to use the unsupported micro-controllers as well.


texts: How come you cannot determine the capacitance of a MOSFET gate based on the other supplied values on the datasheet?

texts:
Conjecture

If it's the case that

$$
Cg = {Qg \over Vg}
$$

It must be the case that

$$
(Ciss + Coss + Crss)Vg = Qgon
$$

But it turns out that it is not. I don't understand what I'm missing.

I know it's something to do with the fact that the actual capacitance a driver charges is not going to be including the \$ Crss \$ and maybe even not include the \$ Coss \$, but that just makes me even more wrong in the equation, so...

Reasoning

http://ixdev.ixys.com/DataSheet/99175.pdf

I wanted to calculate the capacitance of the gate with the charge and test voltage so I could check the time it took to turn on and off.

So then I did the following to see if I was doing it right;

Ciss = 8000pF = 8nF
Coss = 1300pF = 1.3nF
Crss = 220pF = 0.22nF
Qgon = 185nC
Vg = 10V

$$
(Ciss + Coss + Crss)Vg = Qgon
$$

$$
(9.52nF)10V = Qgon
$$

$$
95.2nC \neq Qgon
$$

What did I miss exactly?

I mean if you just do it to the 185nC you end up with 18.5nF, obviously, but there's no value on the datasheet that indicates that you'd actually be driving that value besides from the 185nC, which apparently you cannot calculate based off of the other values on the sheet. Shouldn't you be able to determine the capacitance you must be charging by taking a look at the input and output capacitances minus the leakage?

I'm so confused right now.


texts:
I just soldered a USB OTG cable to connect a keyboard (regular USB-A) to a Raspberry Pi Zero (micro-USB).

How to wire the VCC, GND, D- and D+ pins was obvious and the cable works. However both connectors have a pin that is connected to the connectors metal enclosure. The cable I used has a wire mesh for shielding.

How am I supposed to connect the shielding:

Both connectors metal enclosure to the wire mesh
Only one connectors metal enclosure to the wire mesh (which one?)
Connect shielding to ground?

This question has been asked before: Understand the shielding of a USB device
But it was not answered, aso I am not sure if the fact that this is an OTG cable makes a difference (I guess in case 2. I would have to connect the mesh to the micro-USB that connects to the raspberry, not the keyboard!?)


texts: How to estimate a linear power supply efficiency in LTspice?

texts:
I have a little transformer that I would like to turn into a 5V power supply. Before building it I decided to model the device in LTspice:

The inductance of the primary and secondary windings were measured using an LCR-meter. The wave on the output 20 Vpp in LTspice agrees with what I see on the oscilloscope. The linear voltage regulator is not shown. Since V(OUT) is 5.6-8.5V I would like to use L4941 LDO which has maximum 0.6V drop. But I couldn't find a model for it.

What bothers me is that calculated efficiency is about 8%:

pin: AVG(abs(v(in,ingnd)*i(v1)))=5.46445 FROM 0 TO 500
pout: AVG(5*i(i1))=0.45 FROM 0 TO 500
eff: pout/pin=0.0823504

What brings a question - is such low efficiency expected for such a simple power supply? Maybe I'm calculating it the wrong way? Or there is something wrong with the design itself? I've uploaded the model here.

UPD: After replacing diodes with 1N5408 and C1 - with 1200 uF capacitor I could increase the current through D1-D4 to 3A and the load current to 500 mA. This gives an efficiency about 35.6%. Still it doesn't look right.


texts: Interfacing LEDs at communication lines for a RS232 to RS485/RS422

texts:
I want to use LEDs at the output of R232 to RS485 & RS422 converter to indicate the Rx and TX activities. This converter will be inside an enclosure and I want the RX TX activities to be indicated by LEDs. At page 13 and page 14 of this manual specs for this particular model 7520A of the converter is given.

Here is the terminal for RS485 RS422 and power pins:

And below shows the block diagram and the configuration I want to use:

I want to add an LED for indicating D1+ D1- RS485 communication.
And I want to add two LEDs for RS422 between TX+ and TX- and between RX+ and RX-.

How can this be achieved? Would a resistor in series corrupt the data? I dont have experience with such interfacing is it even possible?

Edit: The specs of small LEDs I want to use is here.

Edit2:


texts: How to wire a 4PDT Switch to switch Rs and Caps for Hi/Lowpass filter Sallen Key Equal Component

texts:
I'm making an active Low/High Pass filter based on the equal component sallen key design I found in the Active Filter Cookbook.

In the book I read that by exchanging the position of the Frequency determining Resistors and Capacitors it is possible to switch between a high pass and a low pass response, using a 4PDT switch.

I'm very confused about how to connect the switch to the components/board, I've been drawing out the connections for a good few hours!  It's simple enough I'm sure, but I can't seem to get something which makes sense, or would work!

My 4PDT is connected like this:

Could someone please help me with a sketch of the connections or any tips on how to hook up the switch?  :)   Thank you very much,


texts: I2C setting MCU as both slave and master at the same time

texts:
Hello everyone I'm working on a new project with the TI MSP432P401R microcontroller. I want to have 2 separate I2C buses. I2C bus 1 will set the MCU as the master, whereas the DAC and the pressure sensor as slaves. Then I2C bus 2 will set the same MCU as the slave, and the SmartPort as the master (more specifically a device that we connect to the SmartPort will be the master). I'm not sure how can I make the MCU both a slave and a master at the same time. What I tried to do was, I defined 2 different eUSCI_b modules

void I2C_init(void)
{
/* Initialize USCI_B3 and I2C Master to communicate with slave devices*/
I2C_initMaster(EUSCI_B3_BASE, &i2cConfig);

/* Disable I2C module to make changes */
I2C_disableModule(EUSCI_B3_BASE);

/* Enable I2C Module to start operations */
I2C_enableModule(EUSCI_B3_BASE);

/* Initialize USCI_B3 and I2C Master to communicate with slave devices*/
I2C_initMaster(EUSCI_B0_BASE, &i2cConfig);

/* Disable I2C module to make changes */
I2C_disableModule(EUSCI_B0_BASE);

/* Enable I2C Module to start operations */
I2C_enableModule(EUSCI_B0_BASE);

return;
}

where i2cConfig is

const eUSCI_I2C_MasterConfig i2cConfig =
{
    EUSCI_B_I2C_CLOCKSOURCE_SMCLK,          // SMCLK Clock Source
    48000000,                               // SMCLK = 48MHz
    EUSCI_B_I2C_SET_DATA_RATE_400KBPS,      // Desired I2C Clock of 100khz
    0,                                      // No byte counter threshold
    EUSCI_B_I2C_NO_AUTO_STOP                // No Autostop
};

and then tried to use this function for each module I defined to add slaves. But the thing is, the function only allows me to enter one slave address, but for my I2C bus1, I have 2 slaves: DAC and the pressure sensor.

extern void I2C_initSlave(uint32_t moduleInstance, uint_fast16_t slaveAddress,
    uint_fast8_t slaveAddressOffset, uint32_t slaveOwnAddressEnable);

I would be very grateful if someone can help me with this problem or show me a better way to implement the same MCU as both a slave and a master at the same time. I'm new to programming with the I2C protocol and I'd appreciate any help. Thank you and have a great day.


texts: Identify this electronic component from DVD drive

texts: I got this component from an old laptop dvd drive. It was placed within the laser assembly. Could you tell me what this component may be?


texts: Will these 100 ohm resistors protect my GPIOs from power surges?

texts:
I am designing a circuit for a microcontroller that has a few 3.3V GPIO pins. I heard from somewhere that adding small resistor of around 100 ohms in series with the GPIO, will add some additional power surge protection, but I am not quite sure how, and have had trouble finding any sources that can back this up.

Is it true that these resistors will help protect the GPIO from power surges, and does this design principle have a name that can be googled?
I assume that using this method, limits the GPIOs to signalling high-impedance inputs, like other MCU's and MOSFETs. Are there any other negatives i should worry about?


texts: Is it necessary to connect relay contact at voltage zero?

texts: While disconnecting relay contact, it is recommended that the action should be done at or near current zero. As the contact area decreases rapidly, a spark is generated due to high current density. But what about the time while connecting the relay? The current will be zero before connecting the contacts. Should I connect the contacts at voltage zero so that the current can't increase much? Or It's unnecessary?


texts: Problem related to the transfer function of RC low pass filter

texts:
I have the following question:

  For the passive RC low pass filter shown below:
  $$V_S(t)=\cos(t)+\cos(100t)$$
  $$V_0(t)=\alpha\cos(t+\theta)+\beta\cos(100t+\phi)$$

  (where \$\alpha\$, \$\beta\$, \$\theta\$ and \$\phi\$ are constants)

  The value of \$\displaystyle \left|\frac{\alpha}{\beta}\right|\$ is?

  The answer is \$10\$

I have tried using the transfer function of a RC low pass filter :

$$H(s)=\frac{1}{sRC+1}=\frac{10}{s+10}$$

$$\implies h(t)=10e^{-10t}u(t)$$

Then tried using the two given equation with \$h(t)\$ as below:

$$h(t)=\frac{V_0(t)}{V_S(t)}$$

After that I am stuck. Even after trying with Initial value theorem as \$h(0)=\lim_{s \to \infty}sH(s)\$, I end up with :

$$\alpha\cos(\theta)+\beta\cos(\phi)=20$$

Can someone please tell if I am missing something or if the question doesn't provide enough information?


texts:
I have a main board with microcontroller and two long distance panel boards with standard 5mm red LEDs with 3.3k resistors. I supply panel boards with 24V over 20m cable. Whole system power is supplied with Meanwell SMPS. I use ULN2003 open collector transistor array for switching LEDs with my microcontroller. So, I draw ULN2003 like switch in schematic. Panel boards is in a plastic box.
My original schematic:

The problem: My LEDs in panel boards, fail after a few months. Mostly, not in same time for two panels. I think some ESD occurs and breaks my LEDs. I searched and find this kind of protections.
First one, TVS:

And diode solutions:

simulate this circuit – Schematic created using CircuitLab
Red rectange is my main board. I show my power supply and reverse voltage protection. Switches are ULN2003 outputs.
Finally, which is the best choice for protecting LEDs from ESD events?
Edit: LED Datasheet


texts:
simulate this circuit – Schematic created using CircuitLab

What is VX?

I am having confusion between 2.8 V or 3 V.

Thank you for your help.


texts:
I am trying to replicate a new planar marchand balun

Is it feasible to manually draw from scratch a 2-layer PCB inside HFSS ?

Or should I use external PCB drawing tool such as Kicad or Altium, then import the PCB layout into HFSS instead ?

Which method is easier to work with ?


texts: Capacitance of two wires with a grounded wire between

texts:
I have measured the capacitance between wires number, say, 1 and 3. With the wiree #2 just floating, the result was 390 pF. But after i have grounded the wiree #2, the capacitance was 220 pF. What is the reason of these results?
The cable is FFC few meters long, so the wires just run in parallel.


texts: How do portable devices use batteries inline with chargers?

texts:
I am developing a project that has access to intermittent 0, 9-15 V DC external power, and want to augment that with an on-board battery to cope with multiple hour power outages from the supply. I am drawing less than 1 amp at 9 V from a step-up step-down regulator in the device, however input voltage can vary 7-12 V if necessary. I had imagined using one or several Li-Ion or Li-Po cells to step up to around 12 V, and include a circuit to handle charging the battery when power is available and discharging the battery when not, all while the device is active.

I thought it would be a simple case of putting a battery in line with supply, much like a lead acid battery in a car. However it seems modern batteries need a lot of nursing. I was put on to PMICs however there seem to be such a massive variety of them with different functionalities, I don't know what terminology would describe what I am after.

A belt and suspenders solution I could have the device monitor battery power and shut down gracefully below a level, but that is not absolutely necessary.

What strategies are used to integrate batteries with devices and power supplies, and thus what functionalities do I need to complete the project I have in mind?

I can see many answers to similar questions here, however some appear to accept that either the battery will discharge with no power, or be switched out when power is available, or switched to dedicated charging mode or something clunky like that. I'd like something more graceful.


texts: No protection if a powered stepper is turned manually?

texts:
It is not clear to me what happens inside the stepper motor when it is manually and rapidly rotated in clockwise/counterclockwise, overcoming the torque of the motor.
As I understand, fly-back diodes are protecting the driver when the windings are not energized and the stepper is acting like a generator.
So it seems to me that no additional protection is necessary if I manually rotate the shaft of the motor when it is fully powered. But I'm not 100% sure on this...
Details
I ordered this little bipolar NEMA 11 stepper, driven from this driver.
The shaft of the stepper is linked to the axis of a knob with a 5-to-1 ratio spur gear. No half-stepping, no micro-stepping.
I plan to use an 8-diodes-array to protect the driver board:


texts: Four layer analog board, should I pour ground on top and bottom layer?

texts:
I am now designing one four layer analog board for 24-bits ADC based bio-potential signal acquisition. I have ground and power plane on the second and third layers. Most of the analog signal traces are on the top layer. The ground plane is on the second layer.

The frequency of the board is about 1.5Hz to 3.79kHz. Board size is about 4"x5". The ADC I am using is the ADS1298 from TI, with analog front-end by op-amps and instrumentation amplifier.

My question is should I pour ground on the open area of top and bottom layers? Will that do anything good to the signals? or that will make them worse?


texts: Mount 360 degree rotator with camera using 2 pins (Power line and Gnd)

texts:
I am designing a rotator circuit which consists of a 5v stepper motorenter link description here and 5v DRV8834 driver ICenter link description here. The driver IC got 1 pins which is a step to control the motor. The problem/question is that only a two lines come from the camera top section. The camera top section runs at 12V. Is that possible to use the same 12V line to toggle as a 5V step pulse as well? The idea is as soon as the bottom section is connected to the top section, the Intelligent circuit should recognize whether the rotator is receiving 12V power or 5V step signal. If it is 12V then the system stays on and shouldn't consume current as well doesn't harm the motor. When it receives 5V step signal it goes through the 5V buck regulator (only if needed?) and supply the voltage to the motor and turns on the rotator. Is that possible to connect? I have attached the rough block diagram. Please let me know your ideas.

simulate this circuit – Schematic created using CircuitLab

My actual breadboard:


texts:
Is it in any way feasible, in a small form, to power a 12v light with a power source or transition source 3" away without any physical connection?

   .    |    ,
    \ _---_ /
 -_ .'leds `. _-
__ :  .---.  : __
   :  \   /  :
 -" `. | | .' "-                                      ,'/
    / |`-'| \                                       ,' /
   '  ]"-_[  `                                   ,'  /_____,
      ]"-_[  ----wire----- |--gap--| ---wire-- .'____ Pwr,'
       "*"                                          /  ,'
                                                   / ,'
                                                  /,'
                                                 /'


texts:
I'm using a true 8-bit DAC to play some low quality audio through some headphones. At the moment I'm just using a 300 ohm series resistor to limit the current to 10ma.

Do I need a series capacitor here to protect the headphones?

The DAC produces voltages from 0V to 3.3V. It does not produce negative voltages. Additionally, the DAC never actually seems to drop below 0.1V.

How do I know if I need a series capacitor to protect the headphones and how do I calculate it's value? Is a 10uF ceramic sufficient? High quality audio is not required, but I don't wish to pointlessly ruin it.


texts:
I am using Atmega328P in sleep mode and for wakeup I am triggering interrupt with push buttons. Circuit working completely fine. PCB is surrounded by aluminum cylindrical body.
Problem is when someone touches the outer body it generates the interrupt (Maybe due to static electric charge), causing the LED to glow which is indication for interrupt call. Even slight metal contact sometimes generate the interrupt.
What is the most optimal solution for this ? And what is the temporary solution( without any changes in circuit) ?
I guess providing ground to the outer body will work(not sure), But I am using RF communication in circuit with PCB antenna. Surrounding antenna with ground is not a good idea I guess. Any other solution in that case ?
Well my schematic is very simple, I am attaching it. I have used internal pull up to avoid floating value. Logic behind this circuitry can be found Here.

simulate this circuit – Schematic created using CircuitLab


texts: Raspberry Pi UPS with 18650 + TP4056 + MT3608

texts:
I'm trying to make an UPS for my Raspberry Pi 3.

Based on

https://nomadaselectronicos.wordpress.com/2015/05/22/fuentecargador-con-carga-compartida-load-sharing/

and

http://ficara.altervista.org/?p=2736

I ended up with this:

In theory, it should provide 5v (output of the MT3608) when powered either from USB wall charger or from 18650 battery (through the  TP4056). The Mosfet will do the switching between mains and battery.

When I power my RPi, it boots but then it enters on a boot-loop which is reported to be caused by low voltage (see: https://elinux.org/R-Pi_Troubleshooting#Raspberry_Pi_shuts_down_.28or_restarts.29_soon_after_booting_up).

I meassured the output voltage and it is stable when the RPi is off as well as when it is on (4.9v ~ 5.1v). The boot up sequence tipically consumes about 150-300mA on a Raspberry Pi B+ I use to prototype.

When the same wall charger is connected directly to the microUSB port on the RPi, everything works flawlessly.

18650 battery is a Samsung INR 18650 25R.

What could be causing the current drop? I'm considering replacing the MT3608 with an USB DC-DC Booster 0.9v-5v (https://www.ebay.com/itm/132487410767) but running out of ideas...


texts:
I am trying to use a N-channel MOSFET to toggle battery power going to a 5V voltage booster using the circuit shown in the attached image. Battery voltage is 3.7V and the gate voltage is 3.3V. High voltage at the gate is used to turn the power off and low is used to turn the power on (on by default using the 5K pull down resistor). The MOSFET switches as expected and I am able to toggle the boosted 5V on and off until I put a load in the 5V bus which seems to switch the MOSFET (BAT-SW in the schematic becomes grounded turning off power to the 5V booster circuit).

Here is a link for the MOSFET I am using
https://statics3.seeedstudio.com/images/opl/datasheet/0440200P1.pdf

Any help or suggestion would b much appreciated!


texts: Resistance or conductance of resistor networks

texts:
I am trying to figure out if the equivalent resistance (or similarly conductance) of a resistor network can be calculated using Qucs (as opposed to solving the Kirchhoff equations directly, or doing the numerical Star-Mesh transform on the network).

For instance if we know the graph/network characteristics, that is, the vertex set (i.e. how many nodes), the edge (bond) set and the resistance values corresponding to each bond (so between a chosen pair of vertices),

How can we input the resistor network as such into Qucs? (can netlists be used for this purpose?)
Assuming the above point is possible, can we then use Qucs to estimate the equivalent resistance of the network? That is, can we set up a Qucs simulation for this type of calculation? (e.g., using a fixed voltage generator in an AC simulation?)

Being a complete novice to Qucs, any hints at any level, be they basic or advanced, would be extremely valuable to me. Unfortunately, in the existing Qucs tutorials I haven't found any examples pertaining to the above type of calculations.

In case you prefer to answer with a working (dummy) example, here's a network we can work with:

Example network for testing purposes: 4 nodes only, labelled from one to four. The only bonds in the network are: {1,2} with resistance 5 ohms, bond {1,3} with resistance 10 ohms and bond {2,4} with resistance 5 ohms. And we're trying to find out the resistance between the input and output.

simulate this circuit – Schematic created using CircuitLab


texts: Why isn't this VCO responding to my sawtooth waveform?

texts:
I'm learning how VCOs work, and I'm feeding it a sawtooth waveform to see the impact on my WiFi. This VCO outputs in a 2.4ghz spectrum, and to understand how it sweeps, I'm passing in a sawtooth waveform and watching how it impacts my laptop wireless (ping drops).
But I'm only seeing my WiFi drop out when I send garbage to the VCO. What am I doing wrong? I would expect that the sawtooth would make the VCO sweep across the frequency, knocking out my WiFi.
I've tuned the sawtooth voltage to match the VCO tuning need ( 0 - 2.4v). I have a 555 creating the sawtooth, and a MAXIM 2750 VCO to create the frequency.
Scenario 1: Feeding a sawtooth waveform, WiFi millisecond pings don't change. Blue = waveform OUT to VCO. Yellow = 555 digital OUT

Scenario 2: I pull the capacitor from the 555 wavetooth circuit, passing noise, and the WiFi drops out. Blue = waveform OUT to VCO. Yellow = 555 digital OUT

Play with sawtooth circuit here


texts: Extrapolating Transistor DC Current Gain Graphs?

texts:
I'm working on a design which will use a BJT to switch 2 PMOS gates low to power 2 separate loads. I am going to drive the transistor from a NOR gate.

From my transistors datasheet, I thought I could extrapolate the current gain graphs with the assumption that they are worst case. In my situation:

Ib ~= (5 - 0.7)/1000 = 4.3 mA
(5 V from NOR gate, 0.7 Vbe drop, 1k resistor)

Ic ~= 12 / 10000 = 1.2 mA

However after probing around a couple copies of my PCB, I'm seeing very different results on each board... Things like the voltage at the base ranging from 0.6 - 4 V, etc. The voltage at the collector also sometimes work like I expect (~0 V) and sometimes is the full 12 V as if the BJT is completely off.

Edit (2016-06-28) here are the different Vbe and Vce values for the BJT:

So it definitely seems like there is either a manufacturing issue or blown transistor. I'll keep investigating.

End edit

Can we not extrapolate the graphs? Any ideas would be appreciated. Alternatively, I wonder if it was a PCB manufacturing / assembly issue.

Circuit:

simulate this circuit – Schematic created using CircuitLab

NOR Gate:
http://www.ti.com/lit/ds/symlink/sn74lvc1g27.pdf

BJT:
http://www.mccsemi.com/up_pdf/MMBT2222A(SOT-23).pdf


texts:
I have a lithium battery connected to a 0.33 amp / 12V pump via a connector (which can be changed - this connector option is part of the question). Is it possible to control power to the pump via code running on a Raspberry Pi or some alternative, and what connector would be recommended?

The reason behind my question is that I need to be able to power and unpower(?) the pump automatically, hence the need for code.

If it is possible, what avenues can I pursue to build a practical solution? If relevant, the main concerns, in order of priority, are: weight, complexity (number of independent components, complexity of code and dependencies), and power consumption (efficiency).


texts: Power consumption on LPDDR4 command bus - impedance options

texts: I'm trying to solicit and opinion on the use of the 60 ohm transmitter/transmission line/ODT for the command bus of an LPDDR4 bus would be better than 40 ohm target impedance.  The system uses an iMX8MQ and Micron 53B768M32D4DT. I only feel we need to run at 1.2GHz or even 1GHz, not 1.6GHz per the LPDDR4 specification.  I am trying to optimize for power and heat.  Any thoughts if using a 60 ohm impedance design would be suitable over 40 ohm?


texts: I know its probably been answered before, but I'm not really sure what to google to find the answer.


texts:
I am designing a flyback driver using a salvaged power transistor that was originally the driver transistor of a flyback in a ctr screen.

This power transistor is the 2SC5681

I want to drive this transistor with an IC, and the high base current required by this transitor (1-2A) cannot be directly supplied by the IC.
So i need an intermediate stage to drive the transistor base.

First, i planned to put an npn transistor before the 2SC5681 in a darlington configuration to amplify the current gain.

but when I reviewed the 2SC5681 datasheet, i saw that this transistor needs a positive Ib (which is normal)
AND a some negative current at the base for switch off (fast)

so my question is, can i use the darlington configuration to achieve the base drive despite this negative current? or what kind of simple base driver can i use for this transistor?

I had thought of using a push pull configuration like a mosfet gate drive system but is it adapted?

maxime


texts: What is the 'H' in 'RWH' for register access type in mcu register map?

texts:
In the EFM32 Ref Manual, on pg 256, there are some registers in the timer peripheral's register map that have an access type of 'RWH'.

I understand that R and W mean Read and Write, but what does H symbolize? I can't seem to find anything in the manual or on google.


texts: Express reverse diode voltage drop as a function of temperature

texts:
I've made a simple temperature meter, with means of series of Ge diodes, followed by 10k resistor.
I am applying +5V to topmost diode cathode, and measuring voltage drop between resistor and ground

simulate this circuit – Schematic created using CircuitLab

Now I am trying to find formula for V(T). It's totally non linear, Probably I could make conversion in software. But, I need to know, what does it looks like?

PS. If interested, for a calibration I know that Rdiode is ~20k for +5C and ~1k for 20C. And I only need narrow range -20C to +30C for rude street temperature measurement.


texts: Is there a way to measure the magnetic field of a digital device and mask it?

texts:
I was reading this report: https://www.fanaticalfuturist.com/2018/05/hackers-find-a-way-to-neutralise-faraday-cages-to-exploit-air-gapped-systems/

It says how researchers used magnetic field generated by CPU to exfiltrate data from an air gapped system. They proposed few solutions to protect against such attacks, two of them were impractical, one solution seems feasible, it requires masking the magnetic field generated by the CPU with a stronger magnetic field from something else.

Is there a way to measure how much magnetic field is generated by a CPU and what everyday objects generate more magnetic field than CPU, which I can use to mask the CPU's magnetic field?


texts: The accelerating voltage in a cathode ray tube is large, from 1000 to 10000 V. However, in old-fashioned television, we use the cathode ray tube. So, how can we obtain such a large voltage when the elctricity in our house is only from 220-240 V r.m.s?


texts: I am looking for a cheap but powerful dev board for an ARM9 processor. It needs to be able to run linux. I am unsure about the exact specifications for RAM and such(thats partly why I'm posting this question). I would however like it to have SD, Ethernet(or WIFI) and USB. Any suggestions?


texts:
I'm designing a simple cell balancing for charging LiPoFe4 cells in series. In order to prevent overcharging, when on of the cells reach the maximum charing voltage, the microcontroller will enable the mosfet, to bypass the current to the next cell.

Consider the following circuit, where the 3.2V sources represent two cells, only with the top cell presenting the balancing circuit.

simulate this circuit – Schematic created using CircuitLab

For the mosfet I intend to use, the max threshold gate voltage is 2.5V. Assuming the worst case scenario, the botom cell being fully charger, I'll have a Vs of 3.2V. With the bypass enabled, I'll have Vg of 5V from the microcontroller. Thus, I won't achieve the Vgs = 2.5V, and the mosfet won't transit onto its 'on' state.

The question, what would be the best way of workaroud here, not changing the mosfet? I thought, maybe, add a greater voltage reference and control this one with the microcontroller,but I still think there's something simple I'm missing.

Thanks in advance!


texts: Modulation And Other Communication Terms

texts:
Could somebody explain the concept of modulating a signal? It's such a broad term I never really understood what it meant.

Are phase shift, frequency modulation, and amplitude modulation all different techniques doing the same thing? How are these used to encode information on a signal?

What other methods exist that I am not aware of?

Thanks everyone.


texts: Is cross talking caused by cables acting as antennas?

texts:
Why does cross talking happen between different cables? Is it because any electrical cable has the capability to act as an antenna?

And most important, why do twisted pair of cables have less cross talk between them?


texts:
I replaced the induction motor in my furnace (PSC type), and it was suggested that I replace the run capacitor at the same time.  (They are both 20 years old).  The new motor is a Fasco A136, identical in model to the old one.

My original capacitor was 4 MFD 250 VAC, the new one is 4 MFD 370 VAC.  I am trying to diagnose why my induction motor is not moving enough air, and I wondered if the capacitor could be the cause.

Would the different capacitor voltage rating affect motor speed?
Could a defective (new) capacitor affect motor speed?


texts:
http://www.atmel.com/tools/avrsoftwareframework.aspx?tab=overview

In my company there is a project, depending on this library. However, it is used by copy-pasting some .c and .h files into the project and adding their names to the makefile.

I would expect the correct way of using a third-party library to be to

either get the already compiled static library plus public headers
or get a self-contained project to build the above and then user projects to depend on the built library, and not on it's sources.

However, I have been unsuccessful in isolating a solution. The download, that I have linked in the top of the question, is 1.25GB in size, and consists various sources and makefiles.

My target is SAM4S and the board is fully custom.

EDIT:

To clarify, here are my reasons for thinking that my two points above are the cleanest way to integrate a third-party static library.

Version control - get the new versions of the library cleanly.
Separation - the library is logically not a part of the core project, for example it should not depend on the external project (otherwise - spagetti code).
Read-only - do not ever fall for the temptation to modify third-party code. Doing so 1. introduces bugs, because you generally lack the understanding of the library authors and 2. prevents updating to newer versions of the library.


texts:
So I'm getting pretty familiar with Electrical Theory but one issue keeps bringing me problems. In a DC circuit, there is a negative (-) and a positive (+). I am aware that in electron flow theory, current flows from the negative (-) to positive (+). See Figure 1.
 But in a car battery, the positive terminal is considered the hot lead and the negative terminal is ground. If you take a wrench and connect the negative (-) terminal to the metal chassis of the car, it won't short, but when you short the positive (+) terminal to the metal chassis, it does. See Figure 2.
My question is.. How is it possible for the positive terminal of the battery to be hot when, there is positive charge on the terminal? ?  If electrons are supposed to flow from negative(-) to positive(+), wouldn't the negative terminal be considered hot and not at ground potential? Also, when the positive(+) terminal is shorted to ground, is that positively charged terminal just allowing negatively charged electrons to flow from the ground? Please Help!

simulate this circuit – Schematic created using CircuitLab


texts: How much can I overvolt a brushless motor?

texts:
I know that motor speed depends on applied voltage, both for DC and brushless motors: I applied 12V to a 6V motor and it started running very fast... until it burnt! :-)

Questions are actually two:

how much voltage can I apply over the rated voltage without damaging the motor?
why?

About question 2: I think it depends on maximum heat the windings can dissipate, which depends on current flowing into them... but then I got lost: power dissipated in a winding is I^2 * R, but how much is I? Is it V/R? But I tried plotting the following formula and it results in absurd values...

Power dissipated in motor:

\$ P_1 = \frac {V_1^2}R  \$  (nominal condition)
\$P_2 = \frac{(V_1 + V_2)^2}R \$   (overvolting)

This results in:

\$P_2 = P_1 + \frac{2*V_1V_2 +  V_2^2}R\$

But this gives impossibile results...


texts: How do I lay out PCB traces for a given "differential impedance"

texts:
This is an attempt to craft a good general question and answer for a topic that's been asked before, but only in specific situations.

Could you describe what I need to know, prior to laying out a PCB board for a differential signal pair with a specified "differential impedance"?

Differential pairs are used for various high speed serial buses, including USB, MIPI, RS-422, RS-485, PCI Express, DisplayPort, LVDS, HDMI and more.

What's the definition of "differential impedance"? On a PCB board, do I need to twist or alternate the wires, as is done for differential pairs in a cable?  Is the impedance of each length matched trace half the "differential impedance", or is it more complicated that that?  How close must length matching be, given the maximum signal frequency?

References that may be of help:

Differential Pair Routing
Differential Impedance…finally made simple


texts: What does a slash mean in a full-load current value?

texts:
The full load current of a motor is less than or equal to 35.6/26.7A

What does this mean?
Also , the max current of the controller (made for this motor) is 30A.
How can it be that the max current is lower than his motor.


texts: how does power load sharing work when power supplies have different/variable capabilities/capacities?

texts:
I work with large networking gear fed by multiple AC->DC power supplies.  One of the modules we use takes multiple AC inputs, when both inputs are active the module can supply 6KW of output DC power, when only a single input is active the module is rated for 4KW of output power (i.e. the single feed capacity is NOT half the dual-feed capacity).
The loads for this system are all fed from a single large busbar, so we can think of the model for the power supplies as looking something like this.  The four input feeds are labeled A1,B1 A2,B2.
        +------+
        |      |      +---+
A1 -----+      |      |   |
        | PS 1 +------+   |
B1 -----+      |      | B |
        |      |      | U |
        +------+      | S |
^                     | B |---> LOAD(S)
Feeds                 | A |
v       +------+      | R |
        |      |      |   |
A2 -----+      |      |   |
        | PS 2 +------+   |
B2 -----+      |      |   |
        |      |      +---+
        +-------

Under "normal" conditions when all of the feeds are live, the power supplies share the load evenly within a percent or so: if the load is 10KW then each power supply delivers very close to 5KW of power to the loads.
But in the case of a single feed failure (e.g. the voltage on feed A1 drops out of range or to zero) the system will begin asymmetrically sharing the load: PS2 delivers 6KW and PS1 delivers 4KW.  This happens nearly instantaneously (verified empirically and the data sheets document this as the designed behavior).
My question is how is this implemented?  My (admittedly naive) understanding is that the two power supplies are isolated from each other, and as such have no way of "communicating" to each other that one should begin providing more power than the other based on a feed failure (or reversion, when the voltage is restored to A1 the system goes back to 5KW:5KW sharing).
I found this writeup, which appears to be related, but my comprehension of what's written here isn't good enough to understand what's actually going on.  I think there must be some way that the relative voltages of the two power supplies change very slightly with the differential load, but I'm getting tripped up on the part where all of a sudden they go from sharing evenly to "the now less capable supply shedding enough load to NOT get overrun".


texts: Separate antenna for radio transmitter and receiver

texts:
I am building a HAM radio. Do I need a separate antenna for transmitter and receiver?

I will be using 20m band and voice communication (No Morse code). My primary requirement is that I should be able to listen to and talk at the same time.

Also, since I am completely new to this area, how complex can the scheme of sharing the antenna can get? In other words, which would be simpler to implement: A shared antenna or separate antenna?

(I have decided to go with the inverted V antenna)


texts:
I am trying to design a class AB linear amplifier. The required peak current is 450mA. I am just using an ideal biasing at this stage. The schematic is as follows:

Here are the resulting waveforms.

The results show that the pmos/nmos can be turned off for half of the cycle. And the problem of zero-crossing is not serious. However, the negative half cycle of the output is cutoff. And the lowest current that can be delivered is only -180mA. So how can I revise the circuit to deliver at least -450mA at the negative half output cycle? Thanks.


texts:
I would like to build a (my guess is a pretty simple) circuit to help training with the foil weapon in 'Olympic Fencing'.
The electronic foil blade has a two wire socket to connect the electric scoring system.  (circuit description ).  At rest (ex. the beginning of each point) there is a closed circuit on the foil blade and surprisingly the circuit is opened to indicate an off target hit.  There is a separate circuit that involves the opponent's metallic jacket that is used to score 'on target' hits.
I would like to use the circuit on the blade to make a buzzer sound when the circuit is opened for a hit. The circuit would let the fencer know that his tip has touched something like a training target and the button was depressed.
I've come across this diagram on a All About Circuits about how to use LEDs to signal that a garden gate (circuit) is open.
Since I'm a noob it's not clear whether the same type of circuit can be used with a buzzer, say in parallel to the green diode?  The buzzer would change the resistance of that branch of the circuit.
Any advice on how to wire the fencing training buzzer would be greatly appreciated.  Along with advice whether to use a breadboard or leverage a microbit hobby processor to help?
What are the options ?


texts: Wireless power transfer circuit to attain ~5W of power on the receiving end

texts:
I am designing a WPT system to run a ws1812 based pixel chain. The ws2812 pixel chain runs on 5v and consumes 500-800ma of power, means 2.5w-4w. The system I made is not able to transfer adequate power to the receiving end load.
Here are my circuits:

The transmitter is driven with a 12v 5a smps power supply. Initially the current consumption of the transmitter circuit was 0.3A-0.4A, then I tuned the oscillator to oscillate at the resonant frequency of the LC tank, hence forming the LC tuned circuit to transfer max amount of power. As resonance the current consumption is at minimum (~20ma). So far so good.
For the transmitter I actually made a bridge rectifier using 4 BA159, and removed the regulator part at all for initial testing however the 2.2k resistance stays on the circuit.
Observation:
1. No Load scenario - When no load is connected, means the load is 2.2k alone, the current on the transmitter is ~600ma, and the capacitor (.1u, 250v) is pretty hot, and the resistance is quite hot as well. The voltage at this state is ~30v.

A cpu fan as load: I added a 12v cpu fan as the load. Current on the transmitter is ~250ma, current on the receiver is ~80-100ma, voltage across load reduces to 14v. From this I can calculate that the power transferred is 14v*100ma=1.4w. This is the max power I could draw on the receiver.
I tried to add a ws2812 led series of 50 led, which is my goal. I used a lm2596 based dc-dc buck regulator to reduce the voltage to ~5v, as we know pixel runs on 5v. the chain I use has a controller also. As soon as I connect the chain with the output of buck regulator, the voltage drops to ~2.2v, and never goes beyond this. The input of the regulator, that is the output of the receiver circuit voltage drops to ~3.5v from 29v (when open). At this state only red leds are glowing and no animations are running due to low voltage. As this state I measured the current through the led chain and found it to be 250ma. The power hence becomes 2.2v*250ma=550mw.
Questions
My question is why the phenomenon with led is happening? If the max power transfer amount is 1400mw, then the voltage should not have reduced such low, it should be at least able to provide 5v as 5v*250ma = 1250mw.
What should I do to get 5v 1a on the output.

Circuit analysis:
At resonance the the resistance Ra and Rb are 1k and 2.8k respectively. SO total resistance across 6 and 7 is ~2.9k. According to astable multivibrator formula the frequency of oscillation is =1.44/((Ra+2*Rb)*C) that gives 211.764khz, this is also the resonance frequency of the LC tank. I am not precisely able to measure the inductance of the coil due to lack of suitable apparatus, but from calculation I get the coil inductance should be 120uh from (L=1/(4*pi^2*f^2*c)). I calculated the inductance using the calculator on https://m0ukd.com/calculators/air-cored-inductor-calculator/. (coil diameter D=65mm, L=5mm, and N=25) gives me 88uh, which is close but not matching.

Transmitter:

Overlapping Transmitter & Receiver


texts: Is there any pure digital phase shifter circuit?

texts:
It is possible to make analog phase shifter circuits:

But In digital electronics (logic circuits), is it possible to shift the phase of an input digital wave?

The frequency of the input wave is 1MHz at most.


texts:
I designed this circuit on PCB (ARM:STM32f103)

My crystal freq is 25Mhz. After connecting st-link in Keil I got this error:

  Invalid ROM Table ST-Link

However, after changing the crystal value to 8Mhz on my PCB, it works fine. I need to know

1) For any value of external crystals, how can I set this value in Keil for st-link to program my MCU without any problems?

2) Keil->configure->Target-> Xtal value is important? what about Keil->configure->Debug->St-link ->Trace->Core clock value.


texts: Industry Standard for Memory Address Decoder Design

texts:
I am currently designing the address decoder of a piece of ReRAM that will be sent to TSMC and manufactured. I have studied in class and textbook that there are two common address decoder designs. One uses CMOS AND gate with a set of predecoders to speed up the circuit.
The other one uses dynamic NOR gates with N NMOS transistors in parallel, where N is the number of address lines to be decoded. I am wondering what is the design that the industry (etc. big companies like  Samsung and Intel) is currently using?
If the industry is using the former one, do they split the entire decoder into smaller ones such as 3 to 8 decoders?
Cause a single memory can have tens of thousands of word lines and building a 10 to 1024 decoder using only two-input AND gates seems improbable to me. Thanks!


texts:
I'm trying to use the SPBTLE-1S with 2 analog inputs and read the chip temperature setting, but it seems that if I try to change the mux, it results in garbled readings (eg, temperature reads -120C or the ADC1 reads 600mV, or ADC2 reads 3000mV -- not consistent).

I've tried running at a low speed (still garbled), and I tried reading (and discarding) the first 12 readings after changing the mux (still garbled).

If I read only a single channel, it works... so I'm thinking of completely disabling/enabling (DeInit / ReInit) between channels, but I was wondering if anyone knew of a better way...

Also... is there a better StackExchange place for this (and other questions -- right now the firmware runs, but it will trigger a HardFault when I try to connect to it)?

Some code:

...

  xADC_InitType.ADC_OSR = ADC_OSR_200;//ADC_OSR_32;                                                         //32KHz
  xADC_InitType.ADC_Input = ADC_CHANS[curchan];                                     //Select the channel
  xADC_InitType.ADC_ConversionMode = ADC_ConversionMode_Single;     //Single Conversion [this chip can't scan channels]
  xADC_InitType.ADC_ReferenceVoltage = ADC_ReferenceVoltage_0V6;    //Use the recommended 0.6V reference voltage
  xADC_InitType.ADC_Attenuation = ADC_Attenuation_9dB54;                    //Voltage range is 0..3v3

  ADC_Init(&xADC_InitType); //Configure

  /* Enable auto offset correction */
  ADC_Calibration(ENABLE);
  ADC_AutoOffsetUpdate(ENABLE);

    /* Start new conversion */
  ADC_Cmd(ENABLE);

...

 while(1)
  {
        //Handle data aquisition:
        //Check / Cycle the Analog Inputs
        if( ADC_GetFlagStatus(ADC_FLAG_EOC))
        {
            ADC_Results[curchan]=ADC_GetConvertedData(xADC_InitType.ADC_Input, xADC_InitType.ADC_ReferenceVoltage);
            if(++bump>10)
            { bump=0;
            //Now reset the ADC for the next one
            if(++curchan >= 0)//ADCCHANCNT)
            {
                curchan=0;
                scancomplete++;
            }
        }
            xADC_InitType.ADC_Input = ADC_CHANS[curchan];                                       //Select the channel
            ADC_Init(&xADC_InitType); //Configure

            /* Enable auto offset correction */
            ADC_Calibration(ENABLE);
            ADC_AutoOffsetUpdate(ENABLE);

            /* Start new conversion */
            ADC_Cmd(ENABLE);
        } //Else we don't have ADC data yet...

   if(scancomplete)
{
  scancomplete=0;
  //Process the data...
} //Else we're not done cycling through the channels yet.

...
}

ADC_Chans is an array of channels to be scanned; if I change the 0 to ADCCHANCNT (array size), the data comes back seemingly quite random, even if I lower the ADC speed or discard 'bump' readings before taking one and moving to the next (tested at 2,3,5,10, and 15).

On the other hand, if 0 is there (so it doesn't change the mux), I get nice, stable readings from the ADC... but I need to be able to read the ADC0, ADC1, and Temperature channels.


texts: How to use a DKO48 telephone microphone?

texts:
I have an old telephone made in the sixties (FF-OB/ZB or FF53). Now, I was planning to make an external speaker for that telephone, but I failed miserably, so I've put that aside.

Now, the handset has a headphone, which accepts line levels and I had no problems connecting it to my sound mixer. The Microphone is a different story, though. I know it works correctly, as I can use the telephone without problems. However, when I connect it to the microphone leads (XLR connector) to the sound mixer, which has microphone amplification and phantom power (48V), the microphone appears to have a very weak pickup.

I need to turn up the gain almost to maximum, to get a signal out of it, and at that levels, it acquires huge amounts of static.

The microphone is a DKO48, here's a picture:

I don't know, whether I should construct a preamp, or if I'm doing something fundamentally wrong. In case someone has experience with that sort of thing, please respond.


texts: Connecting GND on secondary side to protective ground

texts:
We have a battery powered equipment which mainly consists of a temperature sensor connected to a microcontroller via a filter. In addition to battery power we have now added the possibility to use a common 9V plug in DC power supply. When using this power supply the mesaured temperature fluctuates a lot which is a large problem. The whole device is of cause floating compared to earth and it seems to be large potentials (50 Hz) between the device and earth.
I have tried to filter all internal supply voltages without any success.
Between the sensor and the microcontroller is a common mode filter and an RC-filter. I could stabilize the temperature by increasing capacitor C1 to 1 uF but this will influence the temperature signal too much. The temperature decreases approximately exponentially with up to 200-300 degrees Celsius/second.
Another way to make the temperature reading stable is to connect system ground to protective earth which I have tried. Are there any disadvantages to do that? The best would be a power supply with secondary ground connected to earth but it seems that this is almost possible to find, at least in EU. Isn't that allowed. And the customer wants that almost any 9V plug in power supply could be used which is understandable.
Any advice?
See picture. Everything inside the red rectangle is floating regarding to earth. The power supply is connected with a 5.5/2.5 mm DC plug.


texts:
I am creating a pcb that splits a single USB input into 3 outputs (one with data/power carried, two with just power), and I was wondering what is the best way to reduce noise on the power line as this is being made for a low noise environment (for radio work).

I currently have a simple capacitor on the vcc/ground which would reduce the noise a bit, but is there a better way? I have read about LC filters and it seems this would work better than just a plain capacitor. Does anyone have some values that of common inductors that I can source out to add to my project to reduce DC noise on the USB power?

I also have switches which open/close the power outputs and I am worried about voltage spikes when you go to turn on the hardware. Is it possible to filter these by placing a capacitor in parallel to the switch output and ground?

Finally how may I add protection to the circuit to protect the hardware in case of a failure of the pcb? I was thinking about adding a diode for some form of over voltage protection but I am worried about the voltage drop.

Thank you for your time and any answers you can give me.

edit:: Been watching more and more videos mostly relating to quad copter noise filtering for their wireless camera systems. It seems that generally the larger the inductor the better, although a 400-600uH inductor seems to work well with a decoupling capacitor. Does anyone have any other input of the size of inductor that would work to filter most of the noise on a USB power connection?


texts:
Can anyone tell me what the non-cycling lifetime of a lead acid cell(s) is, under some kind of float or trickle charge?

Specifically, I need:

300W for 2 seconds
either at +24V with no conversion, or some lower voltage with a boost converter to reach +24V
10 year life time, with very few cycles (assume < 10 cycles)
trickle charge is always available, so self discharge of the cell(s) is not a problem.
all that for < $150

The largest unknown to me is showing that the lead acid cell(s) can last 10 years under trickle/float charge and still be relied upon.


texts:
I have a 9v battery pack and a small dc motor connected according to the diagram above.

When the motor is disconnected my battery terminals have a peak-to-peak voltage of 800mv:

However, during motor operation, my battery voltage can fluctuate as much as 9.4v peak-to-peak, which, by no coincidence, is equal to Vmax of the supply with no motor:

How can I reduce this this noise and bring it down to a reasonable level? I understand this question has been asked several times before, but I want to achieve a more abstract approach for any motor, given a set of characteristics.

I am aware of the following techniques, none of which have been implemented:

Add a capacitor across the supply to suppress base fluctuations
Use capacitor(s) to decouple the motor from the rest of the circuit
Add flyback diodes to short away any back-emf from the inductive load

Bonus

Say I wanted to clean up the spiky voltage on a 60v supply driving a more powerful motor. How would the values of each helper element change, if at all?


texts: Will MG Chemicals Positive Developer 418 Develop pre-sensitized circuit boards?

texts: I'm trying to find a cheaper alternative to the Datak stuff ($18 for 4oz!), and I came across this (MG Chemicals 418). I'm wondering if it will work with the pre-sensitized Datak boards I'm using (ex here), or if Datak boards require Datak developer.


texts: Transformer power rating and RMS current?

texts:
V1 is the output (secondary side) of a step down transformer. LTspice shows me this:

RMS voltage across V1 = 9.5V
RMS current through V1 = 1.96A
Average power at V1 = 12.36W

So what is the correct VA rating of the transformer, and what is the correct current rating of the transformer? How much current should I expect to be able to draw through R2 without damaging the transformer? Can a 18VA transformer, only supply 12W? It is somewhat confusing for me.

each diode
     1.4A RMS, 0.5A average, 0.5W average (datasheet limits 1A average)
2N3055
    1.36W average

So, diodes are safe, right?


texts: I managed to connect an old PS/2 keyboard to the GPIO pins of my Raspberry Pi. I do get correct data from the keyboard which means when I press 'A' on the keyboard I get 'A' in my C code. The big issue I've got now is that I can't put a sleep delay into my code because even usleep(1) is taking too much time so I don't get correct data or even any data anymore. I tried nanosleep too but for some reason this got totally ignored by my code. Is there any agreeable way to put in a short delay? Without a delay my code is consuming 99% of CPU time.


texts: Transfer function of a real operational amplifer

texts:
We all know how operational amplifiers behave in real world. I am trying to figure out the transfer function of an operational amplifier, part number UA741CN, from the data sheet. The data sheet from ST for this part does not have any performance graphs, but they do have GBWP and other parameters listed.

My goal is to derive a very accurate transfer function given this information to me. The unity gain occurs at 1MHz (the GBWP) but the phase margin is around 50 at the point. This would mean that they are introducing a zero in the part somewhere to compensate for the dominant pole. I would like find where that zero is in addition to other things that I may need to know to figure out the transfer function in Laplace domain.

The question refers to the open loop configuration of this operational amplifier.


texts: Why the resultant period of two signals is the LCM of the individual period of that signal?

texts:
Suppose a signal is constructed using two independent signals(say S1 and S2)both S1 and S2 have two different individual frequencies.The resultant signal that has been constructed has a new frequency,which is the LCM of the two frequencies of the signals S1 and S2 .Logically how can we justify and explain the above method.
 Also there is a video tutorial on YouTube where I have seen this.Refer to it for any reference.
Here is the Video-- 1. Understanding Fourier Series, Theory + Derivation.

He added a low frequency with a high frequency--


texts: Arduino and Interrupts: Fast way to get pin values

texts:
I use an Arduino Uno and already set it up to work with interrupts on digital pins 2, 3, 4 and 5 according to an explanation1 I found.

void setup() contains the following code to setup the interrupts.

  //Endable Interrupts for PCIE2 Arduino Pins (D0-7)
  PCICR |= (1<<PCIE2);

  //Setup pins 2,3,4,5
  PCMSK2 |= (1<<PCINT18);
  PCMSK2 |= (1<<PCINT19);
  PCMSK2 |= (1<<PCINT20);
  PCMSK2 |= (1<<PCINT21);

  //Trigger Interrupt on rising edge
  MCUCR = (1<<ISC01) | (1<<ISC01);

And now, the ISR( PCINT2_vect ) function is triggered on every interrupt. That works like a charm. My question is, what is the best/fastest way to find out, which pin was triggered?

I found something in Re: Is better to use ISR(PCINT2_vect) or attachInterrupt on pins 2, 3?, but I do not understand the code and it does not work out of the box. But it looks impressive...

What is the solution?

[2] http://arduino.cc/forum/index.php/topic,72496.15.html#lastPost

Edit:

At the moment, I am reading the pin state from the from the input pin register:

  if (PIND & 0b00000100)
    Serial.println( "PIN 2" );
  if (PIND & 0b00001000)
    Serial.println( "PIN 3" );
  if (PIND & 0b00010000)
    Serial.println( "PIN 4" );
  if (PIND & 0b00100000)
    Serial.println( "PIN 5" );

In the end, I want to count the interrupts on the pins.
But how can I assure, that there are no counted twice?


texts:
So I'm trying to use one of Analog's evaluation board PLL circuits (ADF4350, here). I need to generate frequencies around 1 GHz, ideally in a +/- 250 MHz range, but in steps of < 1 KHz.

Using the ADF4350 evaluation board, I'm able to specify (say) 0.5KHz between channels. But, I notice that (for example) it is able to produce a really nice, clean 1000 MHz signal, but stepping it to (ie) 1000.001 MHz produces symmetric sidebands that are about -30 dBc and spaced about 1 KHz from the center frequency. It doesn't make a difference whether I'm in low noise or low spur mode.

Has anyone experienced a similar problem? I'm wondering if it's worth trying to custom design something with a different loop filter, or if I should start looking around for other options. This is going to be used in locking electronics for a very narrow line-width laser, and sidebands like that will almost certainly broaden the line :/


texts: Change circuit while sketch is running on arduino

texts:
I've tried to find an answer to my worries but without "definitive" answers.

I'm a noob in electronic so excuse me if it sounds obvious.

My question is: is it safe to update a circuit while a sketch is running? If I'm creating a new circuit and a previous sketch is still on the chip?

I found that normally by disconnecting the ground it should be ok, can you confirm this?


texts:
For p-i-n junction with intrinsic region d, I need to answer what happens when d is very large.
So from simple logic, I believe that at some point there will be no diffusion of charge carriers from p-type to n-type and reverse and I guess that these relate to diffusion length, but the diffusion length is more than 100 μm so that cannot be the reason.

Any idea?


texts: PSU Voltage combines with different amperage capacities

texts: In a common atx PSU has several voltage outputs with different amperage capacities such as 3.3V 25A, 5V 28A, +12 15A, - 12 1A. My question is simply that, if I make a connection positive side from +12V with 15A capacity and negative side from - 12V 1A capacity, then I will have 24V but what about the amperage? It will be 7-8A as total power of positive side or limited to 1A because of -12V capacity?


texts:
I've been trying to print and make my own circuit using Altium (print it on film paper, iron it on copper-coated plastic and then dip it in Ferric Chloride etc.), using Gerber files. Only problem is, Gerber files don't show the holes (and obviously I can't print the drill file) and I can't print the PCB directly since that I can't separate the layers while printing the PCB. Any idea on how to print holes normally?

I've been looking for an answer for a long time but couldn't find anything that worked for me (looked mostly at this).


texts: What happen if I switch those labels when generating Artwork

texts:
What will happen if I edit the label "TOP" and write is as "BOTTOM" and vice versa with the other one? Will the manufactured board be ok, or will everything be mirrored? (When BOTTOM layer is mirrored in the design, as it should be)

We designed this board and we put routes in TOP layer (not mirrored), but we were supposed to have routes in BOTTOM layer. Parts in BOTTOM layer, which were supposed to be in TOP layer, are mirrored. So I wonder if renaming this in createing artwork would fix this thing, or mess up everything.


texts: PIC: What clock is used to program the PIC?

texts:
I have a PIC16 that is not connected to an external clock. If I program the PIC with the FLAG setting the clock to an external clock, then will I ever be able to reprogram the PIC?

Is the programming clock the one specified by the flags, or is it an external one provided by the programmer (PICKIT 3)?


texts: What determines the frequency of alternating current?

texts:
I am certain this question has been asked before but I search and cannot see anything just yet. I read most AC current is 60 cycles per second in the United States and some say 50 but that does not matter to the question.
I am thinking a typical electric generator belonging to a  hydroelectric plant generating power. The generator has some value for the revolutions per second as the water produces mechanical motion to spin its rotor. As the rotor spins the polarity switches from positive negative and visa versa. Is it the case that this value is the same as the 60 cycles per second that feeds into my home?
The transformer I believe does not affect frequency so must the frequency produced at the generator match the value at the electric plug. It is such a precise value I have difficulty thinking it is the speed of the generator but I do not know so I ask.


texts: What is the function of Vref/2 pin in IC ADC0804?

texts:
I've been reading the datasheet of ADC0804 and still don't understand the function of the pin Vref/2. I also have applied the 2.5 volts to that pin (on simulation) but the output stay the same. Like nothing happen.

Can anyone explain to me what is the function of Vref/2 Pin on ADC0804/ADC0803 ?


texts: Which diode is conducting and what are the operation points of the conducting diode?

texts:
In the following circuit assuming that diode's cutoff voltage is \$0.7 V \$ , I want to find operating points (voltage, current) of diodes \$D_1,D_2\$.

simulate this circuit – Schematic created using CircuitLab

My first guess is that DI=0FF and D2=ON.
Then I will have:

simulate this circuit

By applying KVL I have $$10V +I5kΩ -0.7V + I10KΩ +10 = 0$$ By solving with respect to \$I\$ we see that \$I=1.29mA\$

From this point how can I continue to find the operational points of the diodes???

------------------------------------EDITED_1---------------------------------------

My question was answered as you can see below it appears my first assumption was wrong.

My second guess is that \$D_1\$ is on and \$D_2\$ is off;

Then I have the following circuit:

simulate this circuit

By applying KVL I have $$-10V +I5kΩ +0.7V = 0$$ By solving with respect to \$I\$ we see that \$I=1.86mA\$

Then I will have:

\$V_{anode,d1}=0\$

\$V_{cathode,d1}=-10+IR1=-0.7 V\$

Where \$V_{cathode,d1}\$ is the voltage of node between the two diodes.

So now the main question, do these values hold true for our assumptions.

For D2 to be off, VD2<0.7 and \$V_{D2}=10V-I10KΩ-V_{cathode,d1}=10-18-(-0.7)=-7.3V\$

For D1, to be on VD1>=0.7 and \$V_{D1}=0−(−0.7)=0.7V\$

The math confirm our assumption So D1 is on and D2 is off!

------------------------------------EDITED_2---------------------------------------

As I was told my second guess was also wrong since there was a mistake in the math of D2.
D2 is assumed to be off so there is no current flowing through it and hence there is no current flowing through R2 and hence there is no voltage drop in the anode of D2. In the second guess \$V_{D2}=10V-V_{cathode,d1}=10-(-0.7)=10.7 > 0.7V when it was supposed to be <0.7\$ So I am going to make a third guess.

My third guess will be that D1=ON and D2=ON

Then my circuit will be:

simulate this circuit

Then I apply Mesh current method to find I1 and I2:

$$I_1: 10V +I_15kΩ -0.7V = 0 => I_1=1.86mA$$

$$I_2: 0.7V -0.7V +I_210kΩ +10V = 0 => I_2=1mA$$

For D2 to be on, VD2>=0.7 and \$V_{D2}=10V-I_210KΩ-V_{cathode,d1}=10-10-(-0.7)=0.7\$

For D1, to be on VD1>=0.7 and \$V_{D1}=-10+5KΩI_1=0.7V\$

The math confirm our assumption So D1 is on and D2 is on! So probably the third guess was right!!


texts: Computer can no longer see Arduino; possibly burned out?

texts:
I have an Arduino UNO R3. I was working on this excercise and I could not get the servo working. I thought the USB port may not provide enough power, so I plugged a 9V/1A adapter into the barrel jack as well. I also pressed the reset button. I noticed the edge of the PCB between the USB port and the barrel jack getting hot, and I unplugged the Arduino.

When I plug the USB cable in now, the "L" and "ON" LEDs light up, but there is no activity on the RX/TX LEDs and my computer does not recognize the Arduino (no /dev/ttyACM0 shows up). Looking at the edge of the PCB, I see a bit of a white powdery residue where it was heating up, although I am not sure if that was there before.

I'm worried that I may have burned something out in the PCB. I may have had the 3 pin header for the servo misaligned. Can anyone offer me some insight into what may have happened?

EDIT: Here is the edge of the board:

Sorry, I've already scraped off a bit of the powdery stuff, so it is harder to see now.


texts: What limits the speed at which information is sent/received over a fibre optic line?

texts: I was trying to find an answer everywhere, but all I can find is absorbtion and scattering, which doesn't limit the speed itself, just the quality of the signal.


texts: SMD capacitors for a guitar distortion pedal

texts:
I'm trying to build a guitar distortion pedal.

Alright, a bit about the motivation behind this project : It's my friend's birthday in a couple of days and I wanted to get him a distortion pedal cause he's been saying he'd like one for some time. I soon realized that would cost me an arm. So I figured i`d build one.

I've been getting into electronics for a while now so i've gathered quite some components but not that many big through hole capacitors, in fact I almost only have smd capacitors and I was wondering...Could I use SMD capacitors to do my biding in this project? I've never quite understood the reasons why you'de choose one type or physical size of capacitor over another when they are both rated the same capacitance and voltage ratings...I hope you can enlighten me!

Here`s the schematic and a link to the instructables' project page.

N.B. I have all I need to etch my board and given the time constraint that's another good reason i'd want to use smd as I can just reflow my board...

-----------------------------------------EDIT----------------------------------------------

Just to make sure, because I do realize there are different types of SMD caps. I mean ceramic ones. These kinds :