texts:
Good day,

I am building an H-bridge (picture below). My opto couplers were ILQ74. I am using 560 ohm current limiting resitors for the opto coupler diodes, with an input voltage of 3.3V (from MCU). My calculations proved that even 100 ohm would be enough. However, it already happened to me twice that one of the opto coupler diodes brakes (with two different opto couplers). I measured the resistance over it and I get a value of 3 ohm (definitely broken). Could it be just a "bad batch" or something else?


texts: Arduino external power source causes timing issues

texts:
I was prototyping a project (basically a servo and piezo controlled by a button with some LEDs to indicate the state) everything was going fine. So I decided to take the project off the ardiuno board and test it on a breadboard before soldering up the components.

To do this I followed several tutorials for taking the Atmega328 off the arduino and mapping the pins to the crystal and caps and adding a power regulator. But when I try to power it via a 9v battery or a 5v wall wart it acts really weird. The servo responds, then does not respond - or randomly moves about - so it seems like I have a timing issue or my button state is fluctuating.

The thing is this only happens when powered through the "power regulator" I set up - a 5v regulator and some caps. If I leave the Atmega328 on the breadboard and I plug in my arduino board via USB to my computer and just run a wire from 5v and ground to my power rails everything functions perfectly.

I have checked the voltage on the power rails using a multimeter and it is 4.96 (so it is the correct voltage) - I thought it might be an issue with not converting AC to DC - but the same thing happens with a 9v battery. Does anyone have any idea what is going on?

Please help!!!


texts: How to select a CC replacement led driver?

texts:
I have a led ramp in my bathroom. It's dead. The led driver isn't providing any volts on it's output side.
The previous driver was an EBIR AED06-700IIP44 but I can't find a new one.
It's a constant current 700mA IP44 led driver that supply up to 13V and 6W.
I'm not at ease with cc stuff and I can't find another brand with the same characteristics.
==> Except for the mandatory "700mA cc", what should I focus on ? 6W ? 13V max ? both ? or it doesn't matter ?
At amazon I found a Goobay 30602 LED driver cc 700 mA/Class II/17V max/12 W Max.
Could it be a good replacement part ?


texts: Two port mapping files in one VHDL project

texts:
I am currently working on a project for a Cyclone II FPGA board where I am coding a guess game in VHDL. The overall design looks like this:

I have made a port mapping file for the overall design that looks like this:

library ieee;
use ieee.std_logic_1164.all;
use work.all;

entity guess_game is
    port(
        inputs : in std_logic_vector(7 downto 0);
        set  : in  std_logic; -- Set predefined value
        show : in  std_logic; -- Show predefined value
        try  : in  std_logic; -- Evaluate guess
        hex1 : out std_logic_vector(6 downto 0); -- 7-seg ones
        hex10: out std_logic_vector(6 downto 0)  -- 7-seg tens
    );
end;

architecture structural of guess_game is
    signal secret_value: std_logic_vector(7 downto 0);
    signal my_logic_output: std_logic_vector(7 downto 0);
    signal my_mux_output: std_logic_vector(7 downto 0);
    signal seg1: std_logic_vector(6 downto 0);
    signal seg2: std_logic_vector(6 downto 0);

    begin
        Latch: entity my_latch port map (set => set, input => inputs, secret_value => secret_value);
        Compare_Logic: entity my_compare_logic port map (input => inputs, try => try, secret_value => secret_value, my_logic_output => my_logic_output);
        Mux: entity my_mux port map (mux1_show => show, mux1_input => inputs, mux1_secret_value => secret_value, mux1_output => my_mux_output);
        Mux2: entity my_mux_2 port map (my_logic_output => my_logic_output, seg1 => seg1, seg2 => seg2, hex1 => hex1, hex10 => hex10);
        Bin2Hex1: entity B2SSDecoderUsingCase port map (bin => my_mux_output, seg => seg1);
        Bin2Hex2: entity B2SSDecoderUsingCase port map (bin => my_mux_output, seg => seg2);
end structural;

However, before starting this project for the overall game, I created the Binary to Hex decoder as another project separately. When I started making the game, I then copied the Binary to Hex decoder into the game.
However, when I was only working on the Binary to Hex decoder, I created a port mapping file for that one alone, which looked like this:

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.numeric_std.ALL;

entity B2SSDecoderUsingCase_tester is
    port(
        SW : in std_logic_vector(3 downto 0);
        HEX0 : out std_logic_vector(6 downto 0)
    );
end B2SSDecoderUsingCase_tester;

architecture tester of B2SSDecoderUsingCase_tester is
begin

t: entity work.B2SSDecoderUsingCase(behavioral)
    port map(
    bin => SW(3 downto 0),
    seg => HEX0(6 downto 0)
    );
end architecture;

My question is, how can I have these two separate port mapping files in one project? The port mapping file for the overall design of the game should still be the Top Level Entity.
Do I have to port map the Binary to Hex Decoder in the same file as for the overall design or can I do it separately?


texts: how can i add more leds to police light circuit?

texts:
This project uses a 555 timer and a 4017 decade to produce the flash police lights.

This circuit has only 4 leds , 2 blue and 2 red.

I want to connect in  16 leds ( 8 blue and 8 red )
is that possible? and how i will do it?

My thinking is that if i repeat the same procedure from r7 and r9 and the bc547 transistors 3 more times then i will have 16 leds. but i do not know if that is correct or productive.


texts:
OK, just because I seem to like to things that are over my head, I need some advice. I am not an electrician, just a homeowner who has done a good amount of my own electrical (and yes, had it inspected each time) so type slowly to me....
I am building my home theatre and working on the lighting. At the moment, I have two 24V 24W 32ft (.75W/ft) LED strip lights that will be cut down to about 18ft each strip. I assume this means the wattage will drop but lets assume not for now. I currently have them wired in parallel and powered by a 24V 96W dimmable driver which is, itself, wired to a Lutron dimmer switch on the wall. All of this was just inspected and is fine.
What I am now thinking of doing is trying to run 8 or 9 LED low voltage spotlights down the sides to wash the walls in a soft light for effect and to highlight movie posters. The lights I want to use are 12V 3W lights which means .25A per light.
I would like to run these off of the same driver so that all lights dim with one switch. Because these are 12V, I know that if this was a stand alone circuit, I could run it off a 24V driver if I ran 2 in series. Assuming I only used 2 for a moment, I know this would mean the power draw from the driver would be 6W...24V x .25A = 6W
So, bunch of questions:

can I run two different voltage lights (the strips at 24V and the spotlights at 12V in series) off the same driver?

If so, is it as simple, initially, as connecting three positive and three negative outs from the driver (two of the positive and two of the negative outs to run the two LED strips in parallel plus one set of outs to the spotlight setup with the Positive at the start of the spotlight string and the Negative off the last light in the string and, of course, negatives to positives in between)?

Assuming I am still OK doing what I am talking about, I understand that the more of these spotlights I run in series, the bigger an issue I am going to cause. This is where I am most foggy. If I am right in assuming that running 2 12V lights in series matches the 24V out from the driver, by then having 8 of these in series, does this mean that each spotlight is only going to get 3V? (24V circuit / 8 lights)...If so, then I assume this means each light is 3V, .25A, .75W....correct math?

If 3) is all correct, I therefore believe the spotlights would be far too dim. OR does it mean that each spotlight will still be trying to draw 3W and simply 3W x 8 means they will still be needing 24W total? As I said, this is where my feeble mind breaks down.

I think you get what I am trying to do now. If this won't work no matter what, please just tell me to give up. If it will somehow, let me know how.
Thanks!


texts: If a generator is loaded with appliances that  have a power factor lower than .8 is it safe to use power factor correction capacitors to improve this number?


texts:
Recently I need use ULN2803A to drive relays. I've never used it before. I have some questions about it.

I don't find the leakage information (Icbo) of it. So if the input of it is floating, what's the output state?  On or Off? If I can left the input safely floating?
In the datasheet section 9.3:

The GPIO voltage is converted to base current via the 2.7kΩ resistor connected between the input and base of the pre-driver Darlington NPN. The 7.2kΩ & 3.0kΩ resistors connected between the base and emitter of each respective NPN act as pull-downs and suppress the amount of leakage that may occur from the input.

I don't understand the words "suppress the amount of leakage that may occur from the input". What's it mean? Where the leakage from and to?


texts: Is the cut-off frequency for each high order butterworth filter the same or different?

texts:
From reading I see that I can calculate my cut-off frequency for a given Butterworth filter using the equations below.  Let's say then that I have a 8th order filter, and I'm going to make it out of four stages.   Do I calculate the cut-off frequency once using n = 8?  Or do I calculate a different cut-off frequency for each stage i.e., n=2, n=4, n=6, n=8?

This is what I can't wrap my head around yet, are all my stages the same or does each one need slightly different gain and frequency settings to achieve my final response?


texts: Just making sure I won't fry my motherboard?

texts:
I'm building this circuit, which converts a toggle switch to a momentary one, which sends a key to a USB keyboard PCB by connecting 2 contacts together:

I just wanted to check, how do I know the keyboard PCB won't get fried when I flip the switch to 12v DC? Or worse my motherboard?


texts: capacitor in series,is that Butterworth?

texts:
Now you all know the various analog filter types,Butterworth,Bessel,Chebychev...

My question is,if I put single capacitor in the signal path,it will block dc,acting like highpass filter,I believe its 6db per octave roll off.What type of filter that is? I want to imagine what kind of time domain transient response will it have,Bessel filter have less overshoot and post ringing than Butterworth,and I have no idea if my series capacitor is butterworth or bessel or maybe something else.


texts: Lattice Diamond Clock Assignment issue with ECP5 Versa

texts:
I try to get a Lattice ECP5 Versa Board running but I struggle with the port assignment for my clock as I don't understand what exactly Lattice Diamond is doing. It's the first time I'm working with Diamond but the tutorials and user guides didn't really help.
I've set up a simple project, all I wanna do is let one of the onboard LEDs blink with a 1Hz frequency.
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

USE work.config_package.ALL;

ENTITY top_entity IS
  PORT(
    SYSCLK        : IN    std_logic;
    CLKOUT        : OUT   std_logic;
    LED           : OUT   std_logic
  );

END ENTITY top_entity;

ARCHITECTURE rtl OF top_entity IS
  SIGNAL clk_i, rst_i, clken_1MHz, clken_1kHz : std_logic;

  COMPONENT ECP5PLL IS
    PORT(CLKI  : IN  std_logic;
         CLKOP : OUT std_logic;
         CLKOS : OUT std_logic
        );
  END COMPONENT ECP5PLL;

  COMPONENT powerup_rst IS
    GENERIC(
      rst_time : IN integer := 5000     --100ms
    );
    PORT(
      clk_i     : IN  std_logic;
      rst_i     : IN  std_logic;
      force_rst : IN  std_logic;
      rst_o     : OUT std_logic;
      rst_n_o   : OUT std_logic
    );
  END COMPONENT powerup_rst;

  COMPONENT clockdivider_const
    GENERIC(
      div_value        : integer;
      reset_on_disable : boolean
    );
    PORT(
      clk_i      : IN  std_logic;
      rst_i      : IN  std_logic;
      enable     : IN  std_logic;
      clk_out_en : OUT std_logic;
      clk_out    : OUT std_logic
    );
  END COMPONENT clockdivider_const;

BEGIN

 -- SOD  <= (OTHERS  => 'Z');

  SOD(0)  <= led;

  ECP5PLL_inst : COMPONENT ECP5PLL
    PORT MAP(
      CLKI  => SYSCLK,
      CLKOP => clk_i,
      CLKOS => open
    );

    -- Reset on power up
  u1_powerup_rst_inst : powerup_rst
    GENERIC MAP(
      rst_time => 50
    )
    PORT MAP(
      clk_i     => clk_i,
      rst_i     => '0',
      force_rst => '0',
      rst_o     => rst_i
    );

  -- Clockdivider for 1MHz clock
  u1_clockdivider_const_inst : clockdivider_const
    GENERIC MAP(
      reset_on_disable => true,
      div_value        => 160_000_000
    )

    PORT MAP(
      clk_i      => clk_i,
      rst_i      => rst_i,
      enable     => '1',
      clk_out    => LED,
      clk_out_en => open
    );

END ARCHITECTURE rtl;

According to the ECP5 Versa User Guide there's a 100MHz oscillator input at port P3/P4 so my intuition would be to create a pin assignment SYSCLK -> P3 but my lattice spreadsheet looks as follows (ignore the FPGA_UART_RX, SOD[0] and SOD[1] signals, they have been removed for simplicity).

So why does Diamond list the PLL ports CLKI, CLKOP and CLKOS and lists the entity port SYSCLK as "Nonexistent"?


texts: Proper cut-off voltage for SLA battery in 120°F+ environment?

texts:
This is related to this question as well, in which I inquired about the most appropriate float voltage for a battery that would be in very high ambient temperatures, as the float voltage should compensate for temperature changes to avoid over-charging.

A question I'd asked in the comments, and was recommended be a separate question here, is the following:

  What compensation is appropriate for the cut-off voltage of a sealed lead-acid battery? If ambient temperature is 130-140 degrees [inside a vehicle], and I'm lowering the float voltage by .5Volts to compensate (0.003mV per cell per degree celsius over 25°C, 30°C difference to 55°C)

As an example, if my cut-off voltage would normally be 10.8Volts for a deep-cycle battery at 25°C, would that value be lower for a battery in an ambient temperature of 55°C? If so, how much / how would I calculate the compensation?

Tagged as battery charging because I wanted to tag as battery discharging and there wasn't one for it... feel free to edit if there are more appropriate tags.


texts: DC High Current Power Supply for Electrochemical Plant

texts:
I’m looking to build my own high current full bridge rectifier to power electrowinning cells.

I need a DC supply that is adjustable 0 - 5 V, and could supply up to ~50 kA (50 kiloamps.) Obviously this isn’t an off-the-shelf supply, which is why I’d need to construct one myself.

What types of diodes can I use that can handle the extreme currents?

What class of capacitors are capable of handling the high discharge current?

I’ve heard of silicon-controlled rectifiers being used in such applications, which I assume are thyristors. Could anyone give any detail as to why thyristors would be used instead of just regular diodes?

I need some form of surge protection, would spark gaps do the job? Recommendations please.

NOTE: Sorry for the long list of questions, as I do not want to spam the forum with a million different questions on specific problems of a very specific application.


texts:
I’m making a portable Bluetooth speaker and need some help with how to charge the battery pack.
I have made a 3 cell Li-ion pack with a BMS to get a 12V battery for the speaker. My thought was to charge the pack over USB with the help of a 5-12 Volt step-up converter. I’ve set the converter to output 12.6 Volts and then connected it to the charge points on the BMS. This all works and the battery is charging just fine. But...
The step-up converter gets really hot, even though I’m only using a 1 amp USB-port as the input power. What am I doing wrong? Or is that just how it is, that it gets really hot? I’ts so hot that it hurts when I touch it and I don’t feel comfortable putting it inside a sealed enclosure (the speaker box).
Please help me. Is it drawing too much current? How can I limit that? Or is my design just not possible?
Thanks! :)


texts: How to find the UART line is free for send data

texts:
I have several boards that communicate together with Rs485. They have ATMega series microcontrollers such as atmega168p or atmega8. Each board is free to send data at any time and I have limitation that lead to I Cant use Modbus. The number of boards can range from 5 to 10.

My problem is: How can a board find if the UART line is free to send data, and if it detects that the bus is busy, wait until bus is free and then send own data?

Is there e special flag or register that could automatically or manually change it and let the other board find that Line is Busy?


texts:
I am trying to work out the current draw from Vbackup when the RTC is kept alive but the rest of the system is shutdown. I am trying to determine the size of the backup cell that I need for my application.

I am working with the GUM3703 device


texts:
I would like to make PCB board for TLE 5206-2G (check the datasheet).
It is TO263 package.

Basically, what i dont know is how to transfer heat out of the IC. I saw few PCB's that has little copper square with grid of holes in it. Is that what is used for taking out the heat?

Datasheet (page 21) says: Metal surface min. X=7.25, Y=6.9. Is that refers to heat transfer surface ? Will plated holes enhanced heat transfer ?


texts: RS-485 device to RS-232 adapter MUXing not working as expected

texts:
I have a RS-485 device that returns serial ASCII constantly. As the device might near very high voltage or electromagnetic areas, I need to ensure the RS-485 to RS-232 adapters I've been supplied with are MUXing the A and B line correctly, or cheating by using the GND to A signal only. This may sound odd, but my test results show my problem.

I checked the device by logic analyzer, and GND to A is the usual serial data, and GND to B is the inverted version : All good.

I plugged in my adapter in the following ways:

(a) GND to GND, A to T/R+ and B to T/R-    : Data is good.
(b) GND to GND, A to T/R+ and B is removed : Data is good.
(c) GND to GND, B to T/R- and A is removed : No data.
(d) GND to GND, B to T/R+ and A is removed : No data.
(e) GND to GND, A to T/R- and B is removed : No data.

If the adapter was MUXing properly, wouldn't it be watching the differential between A and B, so returning no data if: Either A or B was unplugged, Or A and inverse B didn't match?

If this is the case I would imagine (b) shouldn't return any data, but it does.

Any ideas?


texts:
I am trying to communicate with SIM7100 GSM modem but I could just rarely communicate with it across UART interface. I am observing the signal with an oscilloscope, I am giving 5V as High and 0V as Low, 8 data bit,1 start and 1 stop bit with a baud rate of 115200, at my DTE. Signals are passing thru RS232 Line Driver and a Level Shifter, then arrive to the DCE (GSM modem) with a corrected and inverted signal, which is 1.8V as High and 0V as Low (I have also tried to send for just being sure the inverse of the signal, or reverse of the bit order but GSM modem did not give any response).

When I send the AT command, it sometimes return just echo AT, sometimes OK and sometimes Booting, etc. responses. But most of the time it returns nothing. Since I use the National Instruments VISA terminal for serial communication, I am sure that the send signal is correct and reading is also proper.

If it did not give any response, I could consider it as there is a mistake with the hardware, but the seldom given responses makes me thing my hardware connection is correct (Indeed, I used only the reference designs).

I manually measured all the voltage levels, and the signals at all of the pins including GSM and RS232 for both DCE and DTE. They were all correct, except TxD line sourcing from GSM modem to the microcontroller, which is always asserted. I have also tried 4 different SIM7100 GSM modems if there were a problem with the modem.

Now, no AT or OK receives to me, but sometimes I receive

  1: Read Operation Return Count: 2 bytes \00\00

  2: Read Operation Return Count: 12 bytes Booting...\r\n

  3: Read Operation Return Count: 2 bytes \r\n

  4: Read Operation Return Count: 10 bytes SMS\sDONE\r\n

  5: Read Operation Return Count: 2 bytes \r\n

  6: Read Operation Return Count: 9 bytes PB\sDONE\r\n

What could be the problem?

This first picture set is about my circuit design.

This second picture set is about the GSM RxD signal levels (required and observed). I checked also the datasheets related sections again and I could not find any conflict.

I want to edit the question for new response data.

I am now taking this response whatever I do. What does is mean? What could I do to communicate with GSM this modem?

1: Read Operation
Return Count: 39 bytes
\D8\00!\17-#1\A3\A3\A3\E5\EB\00\00y\00\00e\00wacu\E5\EB\00\00y\
BD\B5\00wacu\E5\EB\00\00

PeterJ told me "set your scope to trigger if the voltage to the module drops below 3.4V briefly" about this edit. I will try this.

Is there any other suggestion?


texts: ESP-07S / ESP8266 I2S audio interface with audio codec IC (audio input + output mono)

texts:
I have never dealt with digital audio interface like I2S.
I want to use ESP-07S / ESP8266 audio interfaces as digital audio I/O (for mic + speaker). ESP-07 has two I2S interfaces: 3-wire audio input interface and 3-wire audio output interface.

ESP-07 manual: https://www.rfsolutions.co.uk/downloads/1494602250ESP-07S_Datasheet.pdf
I found the IC WM8974 of Cirrus Logic a bit interesting. Here is the recommended schematic/interface shown at the last pages of its datasheet:

Datasheet of WM8974: https://d3uzseaevmutz1.cloudfront.net/pubs/proDatasheet/WM8974_v4.7.pdf
The names of the signals of them are different. For example, there is no "MCLK" signal on ESP-07. I wonder if it is possible to interface that audio IC with the ESP-07... If yes, how do I need to interconnect the parts?
If not, which kind of IC should I use to interface to that ESP-07 I2S interface? This audio IC is called "audio coded mono", so for what keywords should I search.
This is shown on the ESP-07 manual about its I2S:

Regards.


texts: Raspberry Pi Pico: can read from FTDI dongle but can't write

texts:
I have a very weird issue with my USB FTDI uart dongle and Raspberry Pi Pico connection.
The problem is that I can read data from the dongle, but not write to it.
Raspberry Pi Pico operates at 3.3v and the dongle is configured to 3.3v.
RX on Pico (GP4) is connected to TX on the dongle
TX on Pico (Gp5) is connected to RX on the dongle
Everything worked fine until yesterday but sending data to the dongle suddenly stopped working.
I was using Arduino serial monitor with the baudrate set to 115200. Same as in my UART Micropython code on the Pico:
uart = UART(id = 1, baudrate = 115200, tx = Pin(4), rx = Pin(5))

I can read from uart on the Pico, but can't send anything.
When I send something from my computer I can see the TX LED flashing on the dongle, but when I'm trying to write from Pico the RX LED is not flashing and there is no data coming to my PC.
Things I've tried:

Double-check the wiring, very easy only 2 wires and they are both connected properly.
Is Pico uart fried? Verified that it's not by connecting RX to TX and verifying that it can send serial data to itself.
Is FTDI dongle fried? verified by doing the same thing - connect RX to TX and check that it echoes the same data.
5v/3.3v mismatch? Verified that the dongle is configured at 3.3v
USB cable problem? Changed USB cable with the same result.
Software issue on Pico? Tried different versions of Micropython, uploaded a simple c++ program which just writes data to the serial port - same result.

Any ideas what might be causing this? This exact same setup was working before yesterday.
Anything else I can check?
I'm waiting on the new FTDI USB dongle (even though this one can echo to itself, but at this point I'm desperate :)), but wanted to check if there is anything else I can try to debug this.
Cheers,
Leonti
Below is the picture of the dongle I'm using:


texts: Reverse Engineering SOT23-6 device marking 41Я0

texts:
Hello Guys and thanks for having me!

I have a burned down SOT23-6 on a PCB (sennheiser AC1) with the device marking "41Я0".
Maybe one of you can tell me which component this is?
Photos:

What i found out:
*The cirquit path on which the component was soldered, had 4 short circuited pins on this component (Pin 1,2,5 and 6). This could mean that the component was a MOSFET as most MOSFETs in SOT23-6 Package have those pins short cirquited (e.g. Si3441BDV from Vishay)

thank you!


texts:
My boss recently asked me how difficult it would be to design a product that could continually record fairly low quality video and store the last few hours in some form of internal memory. I have never done any development with video before. Where would be a good place to start my design?

Do you have any suggestions for an MCU? I have been using Silicon Labs MCUs lately for other designs.

What would be the best camera type to use to keep the project as simple as possible?

What format would be best to store the video in?

Would I need a video codec or is that only need for a device that supports playback? This device would probably just need to be able to transfer the video to a PC for playback.

Any insight you can offer would be much appreciated!

ADDED:
I have been looking on digikey at CMOS Image sensors. I see that there are several on there made by a company called OmniVision. These data sheets say that "The captured data can be transferred either by a standard parallel digital video port (DVP) or by a single-land MIPI high-speed serial interface".
I have never heard of either of those. How do you go about getting that into an image file? using C?


texts: Determining Resistor for Heating Element

texts:
I am attempting to run a Molybdenum heat coil. The best I can tell it is 0.3-0.4 ohms per rack and I would like to run say two racks at 230V at 3.9KW (so it doesn't trip my 230V 20 amp breaker).

Does that mean, assuming a value for two racks is a total of 0.8 ohms, can I add a ~12.7641 ohm resistor for a total resistance of 13.5641 to run it at 3900 watts at 230 volts?

If not, how is it possible to run these? Do I need a lower voltage supply with more current?


texts: Choosing the correct Ground or Power net for internal copper planes in a 4-layered design

texts:
I am a chemistry student trying to replicate a PCB circuit as part of an extra-curricular challenge. I am in over my head, but I am learning a lot and don't want to give up. I tried to route the design with 2-layers, but I have been unsuccessful in making all the required connections due to density/space issues (board x/y dimensions cannot be increased). Therefore I have decided to try a 4-layered design, based on the assumption that these planes will remove a lot of the tracks/traces that are hindering complete connectivity.
The stack:
My electro friend recommended the following setup:

Signal/component top layer (jacks,pots,buttons)

PWR internal plane

GND internal plane

Signal/component bottom layer (the layer with all the components).

General:

A audio-signal processor (  audio delay unit).
Power consumption: +12V rail: 188mA max / -12V rail: 48mA max
Digital power : 3.3 V
Audio output : +10.5V to -10.5V maximum output
Clock signal output : 0V to 8.2V

Main Components

x1 MC - STM32F427ZGT6  - x1 Dram - AS4C16M16SA-7TCN
x2 CODEC - CS4271-CZZ
x7 Dual op-amps - https://www.mouser.dk/datasheet/2/294/NJM2068_E-364244.pdf
x6 Jfet Dual op-amp - https://www.mouser.dk/datasheet/2/389/cd00000492-1795525.pdf
x1 Non-Isolated DC/DC Converters 3.3V 500MA OUT THRU  - 78E-3.3-0.5 https://www.mouser.dk/datasheet/2/468/R_78E_0_5-1711129.pdf

My question:
If one is dealing with multiple GND nets ( i.e GND, GNDA, GNDADC) or PWR nets (i.e -12VA, +12V, +3V3, +3.3VADC) and one is not to split PWR or GND planes due to assumed capacitance/inductance/energy level differences, then how does one choose which net is allocated to the respective internal layers?
My thoughts:

Tie all the GNDS together in one plane? No - The board contains both digital and analog signals and from what I have read, I assume creating a common ground will result in unwanted noise,ground loops,etc.

Look at the net list, assume that the amount of connections needed for the respective GND/PWR connections should determine which GND/PWR is allocated to the ground/power plane. I.e Look at the netlist, assume that pad count is proportional to required returning GND/PWR connections, highest GND/PWR padcount determines the GND/PWR plane. Alternatively look at the schematic and count the amounts of different GNDs/PWRs in order to decide. This would then be 3.3 V for the power plane and GND for the ground plane.

Images

Full schematic
https://github.com/4ms/DLD/blob/master/hardware/DLD-v1-schematic.pdf
Any help would be greatly appreaciated.


texts:
I am soon building a desk and I thought an interesting feature to have would be for the entire desk to essentially be a giant QI charger for my phone.  Obviously, however, this has the problem that maximum charging range for QI is about 1.5cm. I wondered if, using large amounts of copper wire, I could make a large coil - as in the size of the desk - to charge a phone or other QI compatible device placed anywhere on it.
I am fairly new to the actual way wireless charging works, so my question is would this work, and if not is there anything I could do aside from covering the desk in coils?

Thanks in advance,

-Matthew


texts: Variable voltage 110-220v input AC to DC 12v 15a 180W output power adapter with cigarette light socket

texts: Can someone educate me how a variable voltage 110-220v AC input can be converted to identical 12v 15a 180W output without having to flip a switch at the input end?  Would the DC output be steady enough to power a tire pressure compressor without damaging it?  I have also seen products that works only with 110v or 220v (not variable) AC input to achieve same output results.  Is the variable voltage input product making a false claim?


texts: Can you recommend a book on wireless protocol design?

texts:
Can anyone recommend a book on wireless protocol design?

I'm trying to find books with a thorough treatment of MAC and network layers without just being a guide to one specific protocol.

The kinds of topics I'm looking for include: frequency hopping, time slicing, cryptography, low power design and routing.


texts: Use an ATtiny85 instead of an ATtiny13 - Where do I place the XTAL?

texts:
Having looked at a circuit diagram in Beginners Introduction to the Assembly Language of ATMEL AVR Microprocessors by Gerhard Schmidt, I came across a circuit presented by the author (in which an ATtiny13) is used, as below:

Having then looked at Wikipedia's comparison chart, the ATMEL datasheet (Pgs. 29-30) and elsewhere, the only differences between the two packages I can see are:

The '85 has more flash, RAM and EEPROM memory than the '13
The '85 requires can use a crystal oscillator (XTAL) or a ceramic resonator connected to pins 3 (Out) and 2 (In), as shown on page 29.

This lead me to modify the schematic to add the crystal, but I'm not sure if I've altered it correctly.

simulate this circuit – Schematic created using CircuitLab

The question I have is this: Is the modification I've made to Schmidt's schematic (adding the crystal and 16pF caps) correct in order for the '13 to be replaced with an '85? (Assume that, physically, the bridge rectifier and VREG portion sit closer to the LED and caps for the crystal, reducing the amount of GND trace between them.)

EDIT 1: Having read the comments and Choosing the Right Crystal and Caps for your Design, I have come to be aware of the following:

An XTAL has a load capacitance, calculated as CL = (C1*C2) / (C1 + C2) + Cstray
A better way of calculating C1 and C2 is C1, C2 = 2*CL - 2*CStray
The XTAL should be placed as close to the pins as possible (theoretically directly connected to the pins, but in the next holes, for the practical reason of not soldering to the chip's pins).
Cstray can be estimated to be between 2pF and 5pF. (That leaves a margin of error of about 6pF, which seems more than negligible to me.)

This adds a second part to the question: Is there any way to determine/measure (with some accuracy/small margin of error) what Cstray will be, in order to determine what C1 and C2 will be?

Edit 2: I have also looked at this question about appropriate caps to use for a microcontroller


texts:
I was looking at an example of a simple audio amplifier circuit and have a few questions...
In the circuit below what represents the 1 and 2? What is their role in the circuit? Also, I've seen multiple different circuits and some have the potentiometer before going through the op amp and others have it after. What is the difference in having one before as opposed to after? Thank you!


texts:
i know that the differential gain of the differential amplifier ( mosfet or bjt ) is _gmRc or _gm Rd

looking at the curve : if the current went down in one side and up in one side the gm will change so the gain will change right ? then the differential amplifier doesn't have a constant gain ? and if the current is steered to one side the gain will be as high as possible ? i don't know why i think i missed something . is every thing i said true or i made mistake ?
for example if i have a differential bjt amplifier with
Rc = 2.5k , Iee = 1mA so Ic in each transistor = 500uA
so gm = 500uA/ 25mv = 20mS
then the differential gain Avd = _ 20m* 2.5k = _50
but if the current is steered to one side (ignoring the leakage current )  then gm of that side will be = 1m / 25mv = 40mS
then what will the differential gain be ?


texts: What humidity sensors allow the user to configure their I2C address?

texts:
I'm building something that will need to use eight humidity sensors, and I want to use I2C to communicate with them. However, all humidity sensors I've found either have a fixed I2C address, or sometimes they have an address pin to choose between two addresses. The most I've found was the TI HDC1010, which has two address pins, so four possible I2C addresses, but that's still not enough.

Are there any humidity sensors that either have three address pins, or that have a fully configurable I2C address?


texts: Drive voltage regulator Vout when Vin is floating

texts:
I'm designing a system that can be powered both at 12V and 5V. The circuit works at 5V, so a voltage regulator is used when the power is at 12V. A jumper (or several jumpers, given your answers) will route the power lines accordingly.
My idea is to use a single jumper that:

in position A (12V input) connects the power supply to the voltage regulator's input; voltage regulator's output goes to the circuit
in position B (5V input) connects the power supply to the voltage regulator's output, so the main power goes to the circuit; voltage regulator's input is floating

Here is a reference schematic:

Is it safe to do so? Will the voltage regulator be harmed if I drive its output when the input is floating? (in that case, I need 2 jumpers, so I can disconnect the output line)

Thanks!


texts: Program a PIC24FJ64GB002 with a pickit 2

texts: I am trying to program a PIC24FJ64GB002 with a pickit 2 but when I try to program it, the pickit 2 application says that no device was found, despite the chip being hooked up with the programmer. So far the pickit 2 has worked programming any other chip, so I don't see why this one is different.  Do different settings need to be activated in the pickit 2 application?  I am using a pickit 2 clone but I don't think it is the problem because it works with several other types of pics.


texts: Integrating Gefran Linear Potentiometer PY1 with Beaglebone Black

texts:
simulate this circuit – Schematic created using CircuitLab

I want to connect one Gefran Linear Potentiometer with Beaglebone Black for displacement measurement purpose. The signal conditioner of the Lin. Pot. gives and output of 0-10 V. I am using a simple voltage divider circuit of 8.2K 0.1% resistor and 1K 0.1% resistor.
Now I can either feed the voltage across 1K resistor to the analog input pin of beaglebone. Otherwise, as I understand, I can connect an external ADC to the output of the 1K resistor and then the ADC can be connected to Beaglebone Black. In the second case, I do not lose out in resolution provided I use a 24bit ADC. Beaglbone Black's internal ADC has a lower resolution.
Which ADC should I use for this application? Can anybody help me with the circuit diagram for connecting the ADC with beaglebone and the voltage divider circuit?

Signal conditioner for Linear Potentiometer
Gefran Linear Potentiometer PY1 series


texts:
I have some problems with bias output stages. For example in circuit below:

BC547 (VAS stage) collector voltage is about 11 volts and I cannot directly connect it to the base transistor on the next stage. I tried the changes below:

Method 1:

Method 2:

Method 3:

But none of them are working (power transistor become very hot). Has the current source (on VAS) not been correctly designed? Should we bias the transistor base ratio together? Or ground ratio?

If the crossover problem is not important for us, what is the best way to connect the two stages?


texts: Xbox one power adapter wiring - converting it to a 12 volt power supply

texts:
Thanks for having a look at my question.

I know this may seem like an odd question but here is the history of it.

I have a Solidoodle 4 3D printer, Its powered by a knock off xbox 360 brick adapter modded from the factory with a standard looking round power plug. (similar to what you will find on any wall wart) Round with the hole in the middle.

I got a roof leak in my garage and the power adapter that came with my 3d printer got soaked and currently is no good. Tried to buy a new one from Solidoodle but they are now out of business.

The original adapter was 12 volt 12.5A output, I found a used Xbox one power adapter and its rated for 12 volt 17.9A. the printer is pretty flexible on its power supply needs but more amps is better.

Question - I have the dc end of the power cord moved into the xbox one adapter in the appropriate terminals, (12V and GND2) all is good so far, however my measured voltage is only 143.4 mv when plugged in.

There are 3 other terminals on the adapter , +5VUSB - obviously the 5 volt rail, the last 2 are marked PS_ON1 which I am assuming is the power switch on the Xbox and the last is RSENSE which I have no clue what that's about.

I am assuming to have the Xbox 1 adapter turn on I need to put PS_ON1 either to ground, +5V or to RSENSE can anyone help me out with the wiring schematics for this adapter? I have no issues leaving the power adapter on all the time, when its not in use I usually turn off the power bar its plugged into anyway.

update:
The connector appears to be wired straight, cannot identity any resistors or the like in the connector:


texts: Controlling temperature of a water bath with induction plate

texts:
I am thinking of building a sous-vide cooker using some kind of prebuild heater, controled via an AVR and temperature sensor like the LM35. There are a lot of references around using rice cookers, crook cookers or immersion heaters. As induction plates are getting cheaper, this might be a notable alternative, not only regarding reaction speed (they seem to be close to water cookers) and evenness of of the heating, but also the space for putting it away.

My main question might be a little bit physical, but I assume it is still better asked here: While electric resistance heater can just be switched on and off to regulate the temperature, I am not sure how well that works for induction, as there are strong magnetic fields involved. Does anyone have experience there?
I could, instead of simply switching it on and off repeatedly, interface the control panel of the induction plate from the AVR (what would be the best way to do it? I feel the heater should be galvanically separated from the controlling circuit, so just soldering a transistor parallel to the switch doesn't sound like a good idea ...). But the lowest setting might still be too high, thus completely switching off the heat source might be necessary ...

Any experiences or suggestions?


texts: Can I Run An Appliance From a 24v Battery?

texts:
First, a little backstory. My wife is planning to operate a booth at some craft fairs and we require power for a piece of equipment (Silhouette Cameo, a computer controlled vinyl cutting machine). We've done this once before with success at a show that had power provided. However, other shows do not provide power.

The Cameo’s AC to DC pack states that it provides 24v power at 1.25 amps.

My initial thinking is that you could run two 12v batteries in series to provide the power, then at the end of the day, let them recharge overnight and have them ready for the next day. I have a few questions on the practicality and feasibility of doing this.

First off, what kind of battery can I use? I’ve read a few things on the web stating that certain batteries are not good for this application (ie: car batteries). Is this an applicable battery?

https://www.amazon.com/ExpertPower-EXP1270-Rechargeable-Lead-Battery/dp/B003S1RQ2S/ref=pd_lpo_23_bs_tr_t_2?_encoding=UTF8&psc=1&refRID=NV9MYPMB3E5Q6JT65SZS

Secondly, as batteries don’t provide a straight up 12v as they describe, and the voltage differs based on the amount of charge they are holding, can this damage the appliance? If so, is this what a regulator can help with?

Pardon if anything I’m saying comes off as incredibly stupid as I only understand electronics at a very basic level. My hope is that connecting two 12v batteries directly to the Cameo’s DC input will work without damaging it, and if not, a little regulator chip ( like this: http://www.jameco.com/z/7824T-Major-Brands-Standard-Regulator-24-Volt-2-2-Amp-3-Pin-3-Tab-TO-220_51414.html ) would be enough to supply a steady current to the machine with no risk of damage.

Thanks in advance for any help.


texts: Does lead battery + trickle charger = UPS?

texts:
I have some bits laying around and need to build a 12V constantly on power source to run some circuitry.  I have a sealed lead acid (SLA) battery (12V 7Ahr) and an intelligent trickle charger specifically designed for SLA batteries.  The trickle charger can supply about 1A maximum charge current.  The circuitry that will run constantly draws about 100mA, but very occasionally will draw 3A for 15 minutes.

Can I just run my circuitry off the SLA whilst it is permanently connected to the trickle charger which is then permanently connected to the mains?


texts:
The company I work for started a new contract building SCR controlled power supplies. They have a 480v input that's transformed down to 12.5/15/17.5 V. In testing we can push as much as 2800 A on the load side. To deal with the current we go so far as to build custom water cooled hoses with braided copper run through them. All I know about their application is that they heat ovens.
My question is why go through the trouble of building such complex power supplies with expensive water cooled conductors to heat an oven? Wouldn't high voltage with a resistive load achieve the same effect? My only guess so far is the safety on not working around high voltage.
Thoughts?


texts: VCVS ideal vs exact error percentage calculation

texts:
This may be trivial but I couldn't figure how the author came up with the shown expression for the error. I believe we want to compare \$\dfrac{1}{B}\$ and \$\dfrac{A_{VOL}}{1+A_{VOL}B}\$. Doing the math I'm getting a different expression:
\$\dfrac{\dfrac{1}{B}-\dfrac{A}{1+AB}}{\dfrac{A}{1+AB}} = \dfrac{1}{AB}\$
 Any help?


texts: carrier concentration - distance graph of PN junction

texts:
i am trying to plot the distance-carrier_concentration graph above with these formulas:
  -and-

(p-side: x < -xp , n-side: x > xn)
But i could draw only red lines on the graphs with these formulas. How can i or with what formula draw black lines on the graph that majority carrier and space charge region concentration?
I am new and i need your help :)
Thanks in advance.


texts:
I have a question about output capacitor filters.
So I know that a simple capacitor filter would have a single pole response, and this is just a first order filter.  Let's say that the value of the capacitor here is C.
If I had split this single capacitor into 5 smaller ones, i.e. each capacitor has a value of C/5, would my filter now be 5th order?  Would I also have 5 ESR zeros because of this configuration?
EDIT: here is an explaination of what I'm thinking
Given that the single pole RC filter looks like this:

(source: buchanan1.net)
Would splitting that capacitor into 5 capacitors not increase the number of poles and zeroes in my system?  assuming that the resistance in the wires is even 1 Ohm, would that not make multiple RC filters, and thus, increasing the dB/decades of my filter?


texts: Distance between SPI traces to prevent cross talk

texts:
I'm wondering, what is the rule of thumb regarding the distance between the SPI bus (MISO,MOSI,CLK,nCS). How to make sure there is no cross talk from one trace to other trace?

I guess the frequency is playing a role here?


texts: Controlling various Arduinos with Android

texts:
I have an upcoming project which requires me to use about 8 different Arduinos, probably more. They all perform a light show which turns off and on various LEDs at different timings to simulate a "light dance". All that is taken care of, however these Arduinos will be at different locations and they need to communicate wirelessly.

My plan is to have only a master Arduino and the rest of them be slaves. I would like to send a simple "start" message from a phone or other device to the master Arduino, and this master Arduino to send the message to the rest in order to start the show. They all need to start at the same time.

The problem is that I don't know how to achieve this. I have enough transceivers and I think this might be the right direction to take but I am still unsure on how to send the signal from the phone to the master Arduino.

I am a programmer and have very basic knowledge of circuits, so detailed explanation would be appreciated.


texts:
I have this expression with indexing that I would like to understand:
logic  [15:0] mem [3:0];
for(int i=0; i < 2; i++) begin
      if (wea[i])
        mem[addra][8*i+:8] <= dia[8*i+:8];
    end

What value has the expression "8*i+:8" on each iteration ? How works that i+ in the indexing?


texts: How does a battery figure out how many amps to send to an electronic circuit?

texts: How does a battery only send the amps amount the device needs, and not more?


texts: Doesn't building a circuit "Manhattan-style" introduce lot of parasitic capacitance?

texts:
I watch a lot of circuit building videos on Youtube and I can see that the "Manhattan" style of circuit building (placing small islands of copper clad board on a larger piece which acts as the ground plane, and soldering components across the "islands") is quite popular.

I can see that this method is used even in high frequency circuits such as small transmitters. But won't this introduce a lot of stray capacitance, as an "island" of copper clad board on top of the ground piece is essentially a parallel plate capacitor?

Let's say one island is \$ 0.005m\ *\ 0.005m = 2.5 * 10^{-5}m \$. I have some of such board and I measured its thickness as approximately \$1.3mm\ =0.0013m.\$ Therefore the capacitance between an island and the ground plane would be \$C=\epsilon_{0}\frac{A}{d} = 8.854*10^{-12}*\frac{2.5*10^{-5}}{0.0013m}=1.7*10^{-13}F.\$

At radio frequencies such as 100Mhz, the impedance would be \$\frac{1}{2\pi f C} =\frac{1}{2\pi*100*10^{6}*1.7*10^{-13}}=9400 \Omega\$.

This isn't a short circuit, but it isn't very large either. So why do we use this method of construction? What advantages do we get using it that makes it worth having these \$9400\Omega\$ extra impedances to ground? Wouldn't it be better to build on stripboards for example, that don't have that same problem?


texts: Creating a blinking circuit (sensor probe)

texts:
I'm a veteran of electronics with little knowledge if that makes any sense at all. I've dabbled in electronics for about 12 years now, and have had so much going on in life that I've strayed away from electronics building. I'm working on a design for my company, and will do my best to explain it in detail while keeping the proprietary information, just that.

I am working on a circuit/machine that will apply a determined amount of liquid, in the Furrow (path) behind an agricultural planter. The liquid will be controlled via orifices so there is no need to control the liquid pump)

The circuit I'm working on will be 12vdc, a control console (wiring module 1) will have 12vdc in from a vehicle battery supply. A bridge will be installed to power a sensor module (wiring module 2) as well as a bank of fluid valves. (also 12vdc).

On WM1 a simple "master on" switch will be installed, a "lift switch" (When the implement is "raised" in the field, it will temporarily cut power to the WM2, and will return power upon lowering the equipment) will be installed in line to the Master On.

Question: In the line running to WM2 (or multiple WM2's, connected via yet another bridge), I need to devise a circuit (without timing chips) that will "pulse" the 12 volts (on and off) to the WM2 (moisture probe). Being this is DC, powering metallic probes can/will cause corrosion and oxidation on the probe materials. Hence the Pulsing (on 12 volts, off 0 volts). I plan to use a potentiometer and capacitor to pulsate, what component do I need next in line to turn off" the circuit until the capacitor is recharged to full capacity? The potentiometer will be adjusted dependent on the speed of the towing vehicle (manually adjusted).

If possible, I would like to also have an LED blink everytime the capacitor discharges (essentially a status light).

Wiring Module 2 will be the probe. Using 2 probes, +12 will be applied to the anode, the soil will be used as the intermediary conductor, depending on resistant (high moisture = low resistance, low moisture = high resistance) the valve will open or close. I plan to use a 12 volt relay to turn turn on/off the solenoid that controls the valve.

The use of the relay will allow a constant power supply to the valves, while soil moisture content controls the intermediate "control" signal to the relay.

In summary, I am needing to design a circuit that will simply "pulsate" full on/off power to the probes, while being adjustable via potentiometer without the use of a timer.

Thank you for your help!


texts: Power supply unit from 230VAC to 12V, 5V, 3.3V DC

texts:
Is this power supply correct?
The capacistors are for decoupling. This power supply is for:

2x 2W fans
4x sensors (simple temperature, humidity)
uC PIC24

*(the component 'Regulator' is LM7805)
*(trafo is 2VA power)
* Should i separate 12V, 5V, 3.3V GND?

Should i add something or change everything, give me your opinion.
Thanks in advance,
H.


texts:
I've been making plans to install a NEMA 6-50 outlet in my garage, but I don't understand how it can not have a neutral, and instead have two hots (at 120v each) and a ground.

What completes the circuit? My understanding is that hot provides charged particles, while the neutral gives any remaining charged particles a path back to ground.

This seems like a simple question - I've done a fair bit of searching on both this site and diy.se, but can't find any answers.


texts: Encoding 10-bit data on 2 8-bit analog channels

texts:
I have some (expensive) weird real time hardware with only two 12-bit ADC inputs vacant, and it needs to read 10-bit samples taken by a MCU with 8-bit PWM output ports. The ADC can take samples at around 100Hz, the PWM operates at 32KHz, and I want samples from my sensor at at least 10Hz (more is better).

I'm planning on encoding 5 bits on each analog channel by hooking the PWM outputs to RC filters, but this seems dangerous in many ways: I can't really guarantee the PWM high/low levels, and when the 5 low bits overflow I'll have a weird discontinuity. Is there a better way?


texts:
How can I correctly dimension a component, as I'd like to create a package on Proteus ARES?
To be specific, I am not sure which measurements and numbers I have to take, when it comes to the pads.
Kindly, find an example photo attached.


texts: LM2664 noise in the OPAMPS output signal. How to remove

texts:
I have 4 opamps powered from the LM2664. Two of them (1MHZ 1.6V R-R) are preparing the offset voltage for the pair of the OPA4141 which actually provide the signal for the ADC
It works as expected but unforunatelly I see the negative supply voltage "shadow" in the output signal. Yellow - signal on the 3.3uF LM2664 capacitor - red ADC1 output when input is connected to the ground. They are different scale. It is about 30mV PP. (gain 100)

How to remove this influence.
Remarks - 15pF capacitors are not populated.
JP31 is a slider switch with the common pins 9 & 10 (one per side).

EDIT
I have moved the LM.. out of the board. Power is taken from another board.  GND is conected via a wire.
But the problem persists:

The


texts: Harmful to NPN transistor if collector circuit is broken?

texts:
Is there any harm to having a conventional switch that can open the circuit between the collector and +V with an NPN transistor? While the base is still being excited by a pin of my controller?

I am using a simple circuit to allow a micro controller to switch a light on and off. If it matters, the transistor in question is a TIP31 I found at Radio Shack.


texts: Checking my understanding of how hobby servo motors operate?

texts:
Can someone tell me if my understanding is correct please.

The control signal to a hobby servo motor that is connected to an arduino operates by :

In every 1 s there are fifty windows each of length 20ms.
Thus the frequency is 50 Hz right ?

Moving on,

If the servo shaft is at its center and I want it to go 90 degrees left, in each of the 20ms of the 1s, the PWM pin will generate a PWM signal that has 1 ms of pulse width until the pulse has traveled for 1s and then for the next second generate something like 1.25ms?

or will it start at 1 ms and during that 1 s period and change from 1ms to a different value 1.25 ms and 1.5ms as it comes closer and closer to the desired angle( decreases in angle ) ?


texts:
I reclaimed a transformer from an old scrap inverter. It is a Juta 150 W inverter similar to the one below

The transformer have absolutely no information on it, so it is difficult to know what wattage I can expect from it. I have tested the transformer, with 220VAC on the primary (which was the secondary for the inverter, it is two yellow wires). The secondary, which has two black wires, one on the left and one on the right, and one red wire which is a center tap) have the following output voltages:

Between the center tap, any of the two black wires I get 12VAC,
Between the the two black wires I get 24VAC.

Is it safe to say the maximum power I can draw from the transformer is 150W, or is there other components inside the transformer that limits the amount of power that can be drawn from it. Does any one actually know what transformer it is and what the real value is.

Lastly, if any one came across this transformers before, there are two greyish white wires that come out of the transformer between the two yellow wires which I now use as primary. I do not get any voltage from it, and the resistance is 133 kilo ohms. Any one have any idea what those wires might be


texts: How to connect a low impedance RF amplifier to an antenna?

texts:
I'm trying to maximize power transfer from my amplifier to my custom antenna, but am unsure about how to properly impedance match the system.
My amplifier has an output impedance of 4Ω, but is connected with a BNC cable, which are usually 50Ω.
My custom antenna has an input impedance of 35Ω.
My signal frequency is 1860 kHz.
To maximize power in my antenna, should I create a matching network to make my source impedance 35Ω as well (I am afraid the off-axis inductance this creates will eat away more power from the antenna)? Or is it better to keep my source impedance low? And isn't the 50Ω cable messing things up in general?
Thanks for the help!


texts:
I am trying to understand how to use the "Rate noise density" spec on a gyro IC. It is quoted at 0.25 degrees/second/root(Hertz). I plan on sampling it at about 100Hz. Is the noise going to be root(100Hz/2)*0.25 degrees/second/root(Hz) = 7.1*0.25 degrees/second = 1.8 degrees/second ?

(edit)
It is my understanding that the bandwidth is half the sampling frequency. If this is wrong please let me know.

Any help is appreciated.

If you care the chip in question is Analog Devices ADXRS649.


texts: SystemVerilog randomization for a fixed sequence of values

texts:
I need to randomize addr such that addr is 'h0 three times followed by addr as 'hf for two times. The values of addr should be in the sequence even if it is used with randomization.  I tried using a function in a constraint block, but I can't increment the counter for each randomization call.
class packet;
  rand bit [3:0] start_addr;
  rand bit [3:0] end_addr;
   //int count=0;
  constraint start_addr_c { start_addr == s_addr(); }

  static function bit [3:0] s_addr();
    int count=0;
    $display("count = %d",count);
    count++;
    s_addr = 1;
  endfunction

endclass

module func_constr;
  initial begin
    packet pkt;
    pkt = new();
    repeat(5) begin
      pkt.randomize();
      $display("\tstart_addr = %0d ",pkt.start_addr);
    end
  end
endmodule


texts: Fusing on dual voltage industrial device

texts:
Please forgive me if this question has been asked before.

I am designing a heating device that will be sold to industrial consumers. In our past designs we have had multiple versions of the same product (one for 120 VAC (L, N, G) and another for 240 VAC (L1, L2, G)). I would like to simplify the design of this new product so that it can accept both voltages.

The voltage is not the issue. The AC-DC converters I am using will accept either, and the heaters that ultimately will be connected will be selected appropriately. The problem is that the outputs that provide 120 VAC or 240 VAC for the heaters must be fused. I would like to simply put a fuse on each leg of each output, but that means that when the device is powered from 120 VAC there will be a fuse on the neutral output leg.

I understand that the concern with a fuse in N is that it might open while the hot fuse remains closed and therefore the circuit downstream would appear "dead" when it is actually "live". I believe that this concern isn't applicable in the case of the device in question. There is a minuscule chance of user contact with any of the downstream circuit whether "live" or "dead".

Is there any other reason why fusing neutral in this case is not advised?


texts:
I am working on a device with a button that is supposed to turn it on (when pressed briefly) and off (when held longer). The MCU is an STM32L432. The button is connected to PB0. I want to use EXTI as the wakeup source from stop mode 2.

I skipped the low power mode stuff for clarity.

In the main loop I am polling the button. If it is held for more than 3 seconds I call this function:

   void power_shutdown(void){

    volatile uint32_t x = 10000000;
    while (x--){ //ugly delay for button bounce, this one is ~2s
        while (PIN_BTN_LOW){} //wait for the button to be released
    }

    //configure button interrupt
    SYSCFG->EXTICR[0] = SYSCFG_EXTICR1_EXTI0_PB; //PB0 connected to EXTI0
    EXTI->IMR1 = 0x01; //enable EXTI0 interrupt
    EXTI->FTSR1 = 0x01; //EXTI0 line falling edge trigger enable

    //turn off LEDs
    PIN_LED_GREEN_HIGH();
    PIN_LED_BLUE_HIGH();

    debugf("PR1 %08X", EXTI->PR1); //this is always 0x00000000
    debugf("PR2 %08X", EXTI->PR2); //this is always 0x00000000

    NVIC_EnableIRQ(EXTI0_IRQn);

    PIN_LED_BLUE_LOW();

    //dummy loop - entry to low power mode will be here
    while (1){}
}

I have the following interrupt handler:

void EXTI0_IRQHandler(void){
    PIN_LED_BLUE_HIGH();
    PIN_LED_GREEN_LOW();
    while (1){} //dummy loop for debugging
    //TODO: system reset here
}

I expect the handler to be called when the button is pressed. If I call power_shutdown() without polling the button (automatically after some time), then the EXTI0 handler is properly called when the button is pressed, however if the button has been pressed before (like in the normal use case), then further button presses don't trigger the handler.

Also if I force trigger a software interrupt with EXTI->SWIER1 = 0x1; before the dummy loop the handler is only called if the button has not been pressed before. If the button has been pressed before, then the handler is not called even when the pending bit in EXTI->PR1 is set.

I do have default handler and hard fault handlers installed (they are not entered). This situation happens independently no matter if the debugger is connected or not. I know I am calling the function only once, because of the dummy loop at the end.

How to make EXTI trigger an interrupt if the button has been pressed before?


texts:
So basically i have decompiled unoptimized simple program and saw that it runs through gcrt1.S, and i dived in to assembly language and tried to understand what exactly it does. here is my code and my assumption of what it does

00000034  CLR R1        Clear Register
00000035  OUT 0x3F,R1       Out to I/O location
00000036  SER R28       Set Register
00000037  LDI R29,0x08      Load immediate
00000038  OUT 0x3E,R29      Out to I/O location
00000039  OUT 0x3D,R28      Out to I/O location
0000003A  CALL 0x00000040       Call subroutine
0000003C  JMP 0x00000050        Jump
0000003E  JMP 0x00000000        Jump

Clear R1
Clear stratus register
Set R28 1111 1111

Here is where my questions start:
Load R29 from 0x08 (PORTC ?)
OUT to SPH <-R29
OUT to SPL <-R28
Call Main

The confuision that i have is why it loads byte from PORTC register, since the default would be 0x00 anyway

Microcontroller is atmega328p  link to a datasheet


texts: Adding polyfuse to batterypack. Information about adding fuses (self resettable ) is nowhere to be found, so I'm asking here

texts:
The plan:
21S8P x2 (connected in parallel for discharge, charged individually) got brand new Molicell INR21700 P42A 4200Mah 45A rated (they are genuine, safety+reliability is paramount so I got them from a reputable US based reseller.) The controller can sustain 70A constant (96A peak) & up to 90V (this is where I get 21S.)
In my research I have seen a video where they add what IMO are multiple polyfuses (I asked them about that, got no reply) it looked like they put one in for each battery strings.
How do i find the specifications for them? Am I correct in my assumption that each string could use one?
NB: This is my first time asking info here, I hope I did this the right way and that I will learn more.  I did read often about stuff and want to add a big TYVM to all who participate on this site.


texts: Using the switch function of a DC-jack to disconnect a load

texts:
I want to use the switch function of a DC-jack to disconnect a load when a battery charger is connected to a battery which powers a constant current source that powers an LED.

Is the wiring shown below the way to do it? Namely, when the charger's plug is plugged in, 3 disconnects and the battery charges, with the load not simultaneously drawing from the battery?


texts: High power consumption using two transistor boosters

texts:
I have a project which runs on a 12v battery and it needs to draw as little power as possible when being "inactive". I have an ATtiny85 running on a lithium coin battery consuming on average about 5 µA. It is connected to a J-K flip flop IC (cd4027bc). The voltage from the ATtiny i/o pin is 3v which is not enough to "toggle" the flip flop which runs on a separate voltage source(see schematic below). So using two transistor voltage boosters I can toggle the flip flop from the arduino. The problem is that this circuit consumes a lot of power.

The current solution using a transistor voltage booster with two 2SC1740 transistors seems flawed, and I am not sure how to fix it since I am a rookie when it comes to electronics.

Below is the schematics for my circuit:

simulate this circuit – Schematic created using CircuitLab

(pins 9-13 are also connected to ground on FF1)

The flip flop runs on a 12v source separate from the microcontroller.

The goal is to control a raspberry pi, using as little current as possible when the raspberry pi is turned off. So, in other words. I want a switch controlling the 12V battery which will be connected to a 5V regulator that will in turn be connected to a raspberry pi. This switch will be controlled by the ATtiny85 running on a 3v lithium coin battery which is separate from the 12V battery.


texts:
I am attempting to make some of my own connectors to attach to a PCB I have made. This was the tool I used to perform the crimps:
Source

My primary issue is that the connector will not fit into the housing. The smaller fitting on the crimper will crush the insulation barrel and the larger fitting gives a weaker connection. Nevertheless, the crimps will not fit into the housing.

I am using 22 AWG wire. I have noticed that most people use 28 AWG wire and it will slide right into the housing, but shouldn't 22AWG work as well?

I have tried this with female connectors from Pololu as well as a supplier on eBay. I would say it is safe to say the connectors are not the issue.

The DuPont housings are from here

These seem to be fine as well. I have used them on precrimped wires as they slide right in. This leaves the crimper/wire as the culprit.

What is causing the problem? Is it just the tool crushing it?

If the tool is the issue, can you recommend a pair of crimping pliers, preferably ratcheting? I would like to keep the price under $100.

On a side note, I returned my crimping pliers and bought some from SparkFun, hoping that would fix the problem. Instead, it created more. The die on the crimper is not long enough for the Pololu connectors. Furthermore, the crimper tends to mess up the insulation barrel instead of curling it around. Has anyone had any luck with the SparkFun crimper? Maybe I am doing something wrong.

Edit: Some additional information. I loosened the screw on the SparkFun crimpers are they are doing okay. The die is still not long enough for the connectors and I have to crimp the insulation barrel twice to get it to fit into the housings. From this information, I suspect that the tools are the issue. Even though the SparkFun crimper is working now, I would be interested in buying one that will work correctly the first crimp. If anyone has any suggestions, I would greatly appreciate it.


texts:
I'm gonna design a board which data logging it's mandatory! I don't think that i have sufficient space in pcb for large parts but i want an embedded flash (dedicated IC). For handling unexpected power downs the system must storing data every time which is determined by some interval value (seconds). Data have string format with undefined lenth. And i need to store that data in an embedded flash memory. Data comes from, sensors and other peripherals such as power supply monitoring.

Who memory type is best for that purpose? (NAND or NOR)?

I will glad with a >4MB memory capacity.
In a little research i find that NAND flash have small amount of pages with large capacitance and this will consumes more W/E cycles.

-Thanks!


texts: Does it matter what size of via you use in high frequency circuits?

texts:
Here is an image of an LNB and there is some different "Via"s in the PCB that I don't know Why do they use different size of Vias in such circuits. Why? Any reason?

I showed two Vias using two arrows that are close each other(Right side of the image).


texts: When to add an op amp buffer to a voltage reference IC?

texts: The circuit below is from a TI reference design, but my question is generic. I'm generating a voltage reference to add a DC bias to an AC signal for ADC purpose. Could I use the output of the voltage reference IC, in this case LM4041, directly instead of making it passing through an op amp buffer? How do I decide that?


texts: Why is earth at 0 V with respect to phase?

texts:
In 3 phase transmission lines we have different voltages depending on how we measure it. Phase to phase voltage is going to be 1.73 times more than phase to neutral. So far I understand everything that I've just said. Now, phase to neutral has the same voltage as phase to earth. This means that phase has a higher potential than earth and that earth has a lower potential than phase which would in theory be 0 V. Why is earth at 0 V with respect to phase and not floating?

The only reason I think that earth is at 0 V (with respect to phase) is because at the power station there is a metal pole stuck to the earth which is connected to neutral thus allowing current to flow through the earth and up the neutral pole. If there weren't a pole, current wouldn't flow through earth and earth would not be at 0 V it simply would be floating. Right?

Any help is greatly appreciated.


texts: Why does this 75C battery only have a 12 gauge wire on it?

texts:
Example battery:
https://www.amazon.com/Lectron-Pro-7-4V-7600mAh-Battery/dp/B01AAVM1MS

I see many different RC batteries that are have very High "C" ratings but all of them use connectors rated for very low current. According to the formula the continuous current out of that battery would be 75C * 7600mAh = 570A. 570 A is way more than any deans connector is rated for.

Also the wire off of that battery looks like 12 gauge wire. From charts I find the gauge would have to be below 1 gauge to work effectively.

Is the "C" rating for RC batteries just much greater than it needs to be and they are in a sense selling a spec that really doesn't make any difference?


texts:
The boolean expression:

y= (a'+b) * (b(c'+d')) = (a'+b) * (bc' + bd')

is given.

Find out the disjunctive normal form to this boolean expression.

My suggestion:

y= a'bc'd' + a'bc'd + a'bcd' + abc'd' + abc'd+abcd'

only when these terms are true the function is 1 and otherwise not. (=0)

Is the DNF right?

Thanks for the help.

Edit: Here ist the truth table for the boolean expression:


texts:
The electric power grid consists of many buses, with generators and loads connected to each bus.

The so-called operating point of the system consists of the voltage magnitudes, Vn, and voltage phase angles, An, at every bus n. So, the operating point of a system with N buses is the collection of operating points over all buses, (V,A) = ((V1,A1),(V2,A2),...,(VN,AN)).

I am wondering if anyone knows of any public data sets that shows the operating point of the system over time, for example, in hourly increments, over multiple days. If this is not available, I can reconstruct it given the generation/demand at each bus (although not ideal).


texts: GPS USB device with external coax antenna?

texts:
I've been looking around for a bit searching for a USB connected GPS reciever which i can hook up to my laptop. However, the building i'm sitting at is not ideal for recieving GPS signals but i do however have a antenna tower ontop of the building which i could mount a GPS antenna to, but that would require a long coax connector since the USB cable is not suited for ~300m of wiring through a building.

Anyone know of a good USB-GPS-reciever that has external antenna support? I simply can not find any (pref if it's supported by gpsd in Linux).

This is what i've found so far:
http://www.usglobalsat.com/p-688-bu-353-s4.aspx

Thank you in advance.


texts: Do I really need an H-Bridge controller in this application?

texts:
I'm looking to integrate a latching solenoid in my next project. I found a 5V latching type here: LHLA0531111H

The manufacturer recommends I use an H-bridge to control switching of the solenoid. The have a few schematics here.

Instead of using an H-bridge, can I just a use a pair of MOSFESTs to control when it switches? Is that even possible?


texts: Questions about Dry EEG electrode interfacing circuit

texts:
I have finished reading a paper about developing an interfacing circuit for Dry EEG electrodes and there is a few points that I couldn't understand.

  To mask the diode’s parasitic capacitance and conductance,Cb(2.2μF)bootstraps the input for input frequencies higher
  than1/2πRbCb Hz, thus preserving the amplifier’s high input
  impedance while achieving lower noise levels than what is
  possible with a purely resistive bias.

how the diodes and DC bias current circuit could decrease the input impedance? and How Cb will "deny" this and reduce the noise levels?

  For true common-mode components in the input, the current
  through Rf is zero, so that common-mode signals are absent
  in the amplified differential signal at the ADC input.

Why is the current through Rf is zero?

  The second operational amplifier (OA2) serves as a buffer to drive the
  active shield and bootstraps the biasing network

What is the bold sentence mean?

Since all op amps are negative feedback and the  inverting pin of OA1 is connected with the non inverting pin of OA2, Could we consider that all voltage pins of op amps are equal?

Link of The op amp data sheet.
Vcm is the average voltages of all EEG electrodes


texts:
I am designing a PCB for an image sensor. The manufacturer provided a design guide in which they recommend using multiple split ground planes.

One ground plane is for the analog supplies, but there are two split digital ground planes: one for the high speed serial data interface (bandwidths to 4GHz) and one for the rest of the (slower) digital interface signals (bandwidths up to the 10s of MHz).

I think I can understand the necessity of the split analog ground, however why would you split digital grounds? Shouldn't return currents be confined underneath the traces at such high frequencies? Is this to try to keep away the return currents of high speed interface (SLVS differential signals) from the interface signals, or the other way around: keeping the return currents of the slower single ended signals away from the differential interface?

Can I connect the two digital grounds a bit further away (before decoupling capacitors)?


texts:
I need a micro-Voltage reference to calibrate my micro-Volt amplifier. The ICs only go down to 200mV, fixed.

So how should I go about this? Use the lowest I could find, then use a Voltage Divider to go down the micro range? Doesn't seem to be much of a problem since said amplifier have a high Input Impedance.

Or, use an adjustable Voltage Reference that are usually settable using resistors as well (assuming it can be set to micro-Volt).

Or, combination?

We can assume that the resistors are very high precision and low noise.


texts: How are multiple frequencies played through a speaker/buzzer without distorting eachother?

texts:
I have an idea for an Arudino project which is essentially a piezo buzzer music machine that I will be able to program sheet music into. It would consist of individual 555 oscillator circuits at different frequencies and the arduino would control whether they (the specific note) is active or not. I've looked around to find similar projects but everyone I find only uses one or two piezo buzzers with the arduino tone(); library.

It got me thinking about multiple frequencies on one speaker/buzzer and how that works. If I had two square waves wouldn't it cause distortion by either the signals stacking when both are high or cancellation when one is high and the other is low?

I've searched a lot trying to find an answer to this question but nothing has been straight forward. It also has me questioning whether my project is a good idea or not because I wish to play a plethora of sounds.


texts:
So, I'm trying to modify a sample and hold circuit from "The Forrest Mims Engineer's Notebook", that uses a 353 op-amp, so that it runs off of a single supply:

I needed to add a 4.5V (1/2 supply voltage) offset to the inverting input, so that it would operate on a just a single polarity supply. My dilemma is that I need to remove the 4.5V DC offset from the output. Obviously, the output would be a DC voltage, so a capacitor would not work. I was simply wondering if there was a way that I could subtract the 4.5V offset from the output, using all discrete components if possible.


texts: Modeling the thermal part of the Time-current curve

texts:
G’ day,
I am working on designing protection devices for my research work and I am struggling to model the thermal part for the low voltage circuit breakers based on IEC standards.
Based on the standards, the time current curve for types B, C and D are as mentioned on the attached figure. I could not find the proper formula which represents the thermal characteristic for these types (the curve inside the red circle). Please, assist on this matter.
Thank you for your cooperation in advance.


texts: Where to look for logic level of a circuit in the datasheet?

texts:
Whenever I pick a chip for my project, I run through the same chore: finding out if its logic levels match what I work with. Is it 5V? 3.3V? 1.3V? Or one of these that sources whatever level I apply to VCC and reads anything from 0.6V to 36V and more just fine?

I'm fairly sure that information is supposed to be in the datasheet but only rarely I manage to find it somewhere in clear view. Common search for "Logic" turns up only irrelevant entries; search for Voltage brings hundreds of various ratings, levels, tolerances etc. I usually end up looking up a circuit involving given chip.

What are the usual entries/clues/symbols to look for in a datasheet to find the logic levels of given circuit?


texts: How to integrate,monitor and control home alarm system using RS485 - TCP/IP?

texts:
My house have an older alarm system which hardwired into the walls and i would like to connect it to the home network for furher integration or expansion. our CCTV cameras are connected to the DVR and the network router which allows more control and flexibility in its maintenance.

This is the spec sheet of the alarm system and the product spec for the PC Interface module and notice the "485 COMMUNICATION BUS" listed at the bottom of the list in 2nd page which is also labeled "CONVERTER: SERIAL PORT/NETWORK CONNECTION" in the diagram on the following page.

The "PC INTERFACE MODULE" comes in 2 flavors which use 4 wires over "Serial Port Cable" to connect to a PC and a 2 wires over "Network Cable" to connect to a router.

Below is the wiring diagram of the control panel for my home alarm system.

My immediate concern for now is to connect this control panel into the home network so i can monitor, tweak or control it over ssh, for example. At the same time, i can't help to wonder if i can substitute any of the devices above to either connect to the router directly or to a raspberry pi using the 2 wire connection, or wirelessly using arduino with relevant modules.

Alternatively, can can i use other serial interface such as cp2102 based USB-TTL to connect directly to a Raspberry Pi? Is it possible to use arduino with arduino with serial port shield (ie: RS485) and wireless serial module to communicate with the router? What are some of the programs that can recognize this type of protocol and allow the intergration of this alarm system with the existing CCTV-DVR system?


texts:
I have designed a frequency counter circuit diagram.  See below.

Now I am stuck on the part to wire up the decimal point in my circuit. The one that's the LED beside the 7 segment display. Do let me know if you find it hard to see the image below.

So basically I am supposed to:

Display the frequency on three 7-segment displays with a decimal point wired up so that:

The display is in the format XX.X.
If the current frequency is out of the current range, all the
segments are OFF except for the decimal point.
Arrange the displays so they read left-to-right.


texts: I am looking for a microcontroller to process 1 HDMI input, manipulate the frame, and output to 1 HDMI output. What can I use?


texts:
I have seen in many books and sites that we can build DC to AC converter circuits. My question is whether there is any limit for the range of DC voltage and AC voltage. Is it possible to get high AC voltage from very low DC voltage?

Let me give a small example to understand my question clearly. I have recently seen some posts:

12V DC to 220V AC Converter Circuit

Is it possible to convert just 12V DC voltage to that much 220V AC voltage? And also if I require 240V AC with 10V DC, what are the modifications to be done in this circuit?


texts: Selecting the correct ILI9341 Drive Mode for STM32F407 using FSMC

texts:
I have selected the STM32F405 for my next project. With this controller, I am planning to drive a 240x320-TFT with an ILI9341 display controller by using the STM32's internal FSMC interface.
I have not decided exactly which display I am going to take but I have chosen two almost identical TFTs with ILI9341 for the selection that only differ in terms of FPC pinout.

The FSMC interface of the microcontroller can either drive displays in 8-bit or 16-bit mode. In terms of display speed, I would like to adhere to 16bit mode.

So, I have been looking at the different drive modes of the ILI9341 and have found out that there are 15 modes, which can be selected through IM0-IM3 (page 27).

Datasheet: https://cdn-shop.adafruit.com/datasheets/ILI9341.pdf

However, I am currently in the process of designing the schematics and I am not sure which 8080-mode I have to select.
What is the difference between 8080-I 16bit and 8080-II 16bit (p.70-75)? I have looked at the diagrams and have found that different channels of the datachannels D[17:0] are used. But I can not imagine that this is the only difference. Can anyone tell me or recommend the appropritae mode that complies with the STM32's FSMC interface? As I am not using the STM32F427/37 direct TFT-driving is not relevant in this case.


texts: How to send a text message from an ATMEGA328PB microcontroller

texts: I am looking to make a project with an ATMega328PB microcontroller. I want to tell when my mailbox has been opened and to send some sort of notification. I was thinking of use a GSM module to send this text. Is this possible and is there any other way to send some sort of notification without having to use a SIM card?


texts:
While this may be suited for an automotive section I believe my question is better suited to this forum.

I'm having OBD II comms issues and have a run a similar troubleshooting process to what's listed here.

https://mechanics.stackexchange.com/questions/44157/obd-ii-scanner-refuses-to-communicate-with-the-vehicle

In addition I have checked the actual voltages and grounding of the data link connector (DLC).

Per the following I have J1850 PWM pin out.

http://www.onboarddiagnostics.com/page03.htm

I am relatively new new to electronical comms processes having only tinkered with an arduino. My voltages are 12v at the battery and pin 16 to pins 4+5. Pin 2 to ground varies between 1.5v-2.1v, pin 10 to ground varies between 4.3v and 3.5v.

Not sure if I am accurately reading pins for a coms protocol should I be measuring voltage between the +bus and -bus or between the bus and ground?

If my measurmemts are accurate does it indicate a wiring problem or a comms ouput issue?

"-Edit your question with more details. What OBD cable you have? Have you been able to make it work somewhere? What software are you using? What car or CAN device are you trying to connect to? What other resources you have available or you might be able to get?"

I was using a Veepeak OBDII BTLE connector. I have also used A cheap advance version and the more expensive advance version, in addition a mechanic tried to use their professional computer for inspections and it failed there.

I have used all of these OBD connectors to connect to other vehicles. I have used both torque pro and car scanner apps for the bluetooth. The other scan tools come with whatever default software they are running.

I am attempting to connect to a 2003 Mazda Tribute ES  V6 3.0L engine.

Since writing the original post I have swapped the ECU, which brought the voltage outputs in spec range, and bypassed the DLC using some spare jumpers I had soldered to alligator clips and then form fit O ring style connectors to the pins on the OBD reader.

I'm more than willing to get another arduio shield and learn a bit more but as far as I can tell the car doesn't speak CAN. J1850 PWM is it's own pin out and comms protocol that was common on early Fords, Mazdas and related production.


texts:
I'm still busy with my DMX splitter (soldered everything), however, I made a mistake with my TVS protection diode. I put it in series with 220 V AC, and nothing happens (no current flows).

I expect I have to put this diode between the two AC wires, but before I mess up with 220 V AC I rather hear some feedback.

What I have now is:

simulate this circuit – Schematic created using CircuitLab

(I could not find all symbols, so I misused a few):

V1: 220 V AC (Dutch power socket)
F1: Now fast blow, later slow blow 0.25 A
F2: Resetable temperature fuse, 73 degrees
D1: Bidirectional 440 V TVS resetable diode
Load: 5 x 600 mA 5V AC/DC converters

I expect I need to use the following circuit:

simulate this circuit

Can this be confirmed?

Also, does the order of F1, F2 and D1 matter?


texts: Make a NP (motor start) capacitor from two electrolytics

texts:
I trust this hasn't been answered already. I have read some of the posts and I understand that the basic answer to the question is 'yes', but, before I damage something valuable, I'd like to clarify....

I have a concrete mixer which operates on 110V ( site voltage ). In fact, we salvaged this from a skip. It isn't very old and cost 400 UKP when new. It has been brutally mistreated, is dented and covered with concrete, BUT most of the damage is cosmetic IMO.

The motor is a 750W induction type and it all looks in very good nick. They binned it because the motor wouldn't turn, but that's just a dodgy capacitor. However, this particular start capacitor ( 100uF @110V ) costs 15-20 UKP.

I have plenty of very big electrolytics from big SMPSs: two of these rated at 250uF in series ( the voltage is plenty big enough ) should work, but this is lots of volts and lots of uF and I wonder if anyone has ever done this or can confirm the scale-up from low voltage work will fly? I don't want a shower of sparks.


texts:
In one of my projects I need to generate different kind of 220V amplitude waveform signals in order to send commands to a heater using the pilot wire protocol. Here are the needed waveforms:

Is there a way to use a DAC and then amplify the output of the DAC to a 220V amplitude. If yes which circuit and components can I use.

Otherwise I am open to other price and size optimal circuits to get such waveforms.

Many thanks


texts: What is the type (or package) of this IC?

texts:
Recently I found such IC on a PCB. I have never seen such package and wonder what it could be? Please, help me identify the type of this package. (It seems like an IC adapter, but has the same pins pitch inside and outside, so probably it is not an IC adapter).

The yellow things is just dirty PCB, it doesn`t matter.


texts: Can an inverter through a battery charger charge its own batteries?

texts: I understand some of these laws of thermodynamics. An alternative to this question, being inventive, is can an inverter power a dynamo (which is powered by an electric motor) to charge the same inverter batteries? It may seem redundant but I am pushing the limits with a beginner knowledge.


texts: Understanding 5V to 1.8V UART level-shifting circuit

texts:
Hopefully it's OK to ask very basic electronics questions here.

I had a TTL 5V UART cable, however the board I had only accepts 1.8V max. So I found some online schematics that uses resistors and a transistor, and I built it on a breadboard. It actually worked.

I just want to understand how it worked deeply. Why did it work?

Also, how do you properly calculate the EXACT values of resistors to drop the 5V input to 1.8V? What's the formula for that?

Sorry for electronics 101 question, but please ELI5 the answer. Thanks.


texts: Two-Stage Common Emitter Amplifier Is Clipping Unexpectedly

texts: I've been reading about multistage common emitter/source amplifiers and have decided to test some high-gain designs with PSPICE. One design has me very confused and I was wondering if someone could explain its behavior. I have a green voltage probe on the first stage and a red voltage probe on the second stage. Both stages are identical and are AC coupled. Why does the PSPICE simulation result in the following output waveforms? The final output clips at 5V and 15V as expected, but I'm unable to explain the behavior of the first stage. Thanks!


texts: 74ls245 won't drive the data bus from 74hct377 8-bit Flip Flop

texts:
I'm building a breadboard 8-bit computer (Ben Eater design: https://eater.net/). However, I decided to substitute two 74ls173 (D flip-flops) with one 74hct377. The register works as expected, but the 74ls245 doesn't output the data to the bus. What did I check:

The connections seem ok. The Buffer is working in A->B direction
(pin 1 high). The output is enabled (pin 19 is low). Both ground and
VC are connected.
The buffer receives data on pins A. The
voltage is approx. 2,5V.
The supply voltage is a bit too low: 3,5-4V. My power supply is supposed to give 5V, but I got Voltage drops (I have difficulties handling them). Anyway, other IC seem to work well enough on 3,5-4V, even the 74ls245 at the other location in the circuit.

Here goes the photo of my ciruit. Any ideas how to solve this? Maybe some other IC for buffer that handle lower power supply?


texts:
i want to communicate between uno, mega and netduino, which protocol should i use

i want the uno and mega to send information to the netduino which mean that i don't need duplex connection which mean i could go for I2C with both as master writer and netduino would be slave reader, would that work ?

distance is 2 to 3 ft and i duno about other limitations it's kind of why i'm asking in the first place

any tips or information is appreciated, thanks in advance

also i'm using easy VR shield and wifi shield, would that be a problem ? thanks


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What's the purpose of the ground plane?

I guess it's a pretty basic question and I tried to understand it by reading http://en.wikipedia.org/wiki/Ground_plane#Printed_circuit_boards but I still don't really get it.

The "allowing the designer to ground anything without having to run multiple tracks" part is clear but the others are not so much.

I observed that various PCBs have, but others don't have a ground plane. Also, how usual it is to have a ground plane on one side and a power plane on the other side? What are the benefits? Is it supposed to lessen electrical noise? In what applications is it preferred?

I guess it's a lot of questions but I'm really interested about the answers.


texts: Does pin A15 on a Z80 tell if the CPU is addressing ROM or RAM?

texts:
I am designing a simple, hobbyist single board computer similar to an Arduino using a Z80 CPU. The trouble I am running into is how the CPU addresses memory. I know that the Z80 uses pins A0-A15 to form an address bus, but reading "The Z80 Microcomputer Handbook", https://archive.org/details/The_Z80_microcomputer_handbook_William_Barden/page/n109, page 118 (In the book, not in the slider at the bottom of the webpage), second paragraph under "Interfacing ROM and RAM", it says that pin A15 is used to differentiate between the CPU addressing ROM or RAM. It says that when A15 is low, then ROM is being addressed, and when A15 is high, then RAM is being addressed. Is this true?

If it is, would I be correct in saying that that would take my 16 bit address bus to a 15 bit one, since one of those address pins is used to tell if the CPU is using ROM or RAM? Wouldn't it make more sense to AND MREQ and M1 together and connect that with the chip enable on the ROM, so as to make the ROM active whenever the Z80 is in opcode fetch mode?

The reason I ask this is because I would like the CPU to have 64K of ROM and RAM, if this is possible.

I'm new here, so any help is much appreciated, but if I did anything wrong, please tell me and I'll fix it.


texts:
I'm trying to cut the power for 5 seconds to my circuit every 30 minutes using a 555 timer. I've been trying to design my circuit using 555timer and NPN but im not having any luck with it has anyone got any suggestions?

Input Voltage: 5v


texts: How to Wire DC Motor to Solar Panel and Battery to Only turn on at Night?

texts:
I have tried looking this up on google but can only come across ones that have the motor running all the time from the solar panel and battery, where I need it to run only at night. So anyways, my dad is trying to build a small scale lighthouse (6 ft tall) and basically needs the motor to only run at night to turn the shaft that has a light on it to simulate a real lighthouse. My dad and I arn't too familar with electrical things when it comes to DC stuff as I know a little bit and my dad knows pretty much nothing other than + goes to + and - goes to -.

So far my dad thinks we should connect the motor to the battery and electrical panel to the battery, but I told him that I think that will run the motor all the time, which is not what we want. So we both know we do need a sensor to detect if it is night or day of some sort. Anyways, one video mentions using a DC to DC buck converter. This is because the voltage coming off of the solar panal is 20 volts as I measured it with my multimeter. The current plan looks like this: https://imgur.com/a/X7VsoDn However, there are a few issues with this current plan that I am hoping you guys can help us out with. The first thing is that there is no sensor and I am not for sure which one to get and how to wire that into the circuit. The second thing is that the solar panal actually came with a "charge controller." I think we may need this as the amps put out by soloar panel according to the specs on amazon is too much for the buck converter and the motor. In the design above, there is no charge controller in there as I don't know how to wire that in either. The reason why I think we need the charge controller is because it says the amps is reduce to 3 amps which is below the max amps that the buck converter says it can handle, which is good. Another thing I am worried about is we might need a second charge controller or something to reduce amp as the amps coming from a standard car battery is probably too much for the second buck converter. The reason why there is a second buck converter is because my dad wants the motor to spin slowly as this motor, while it has lower rpms, it is still way to fast. I know that if I reduce the voltage down from maybe 12v to 9v, that it will decrease how fast the motor spins. This number may have to be reduce further by playing around with the buck converter to get the right speed out of the motor. One good thing is I don't have to worry about direction of the motor and even if I do, I can just change the polarity of the motor by switching the 2 wires around. I am also thinking there is probably something else I am not thinking about that can be a concern that you guys might know about. So anyways, here are the current parts we have from amazon and the specs are listed there too:

Solar panel: https://www.amazon.com/gp/product/B01MZ43GWR/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

DC to DC buck converter: https://www.amazon.com/gp/product/B07NTXSJHB/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

Motor: https://www.amazon.com/gp/product/B07FKKWSFJ/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

Thanks in advance.


texts: How to interpret thermometer sensor reading values?

texts:
how to interpret values for this sensor:

The value is 12 bits, so values can be as much as much as 4096. The temperature range is -40 to +125 Celcius. What is the meaning of -9.05 LSB/degreeC?

user manual p33


texts: Schematic editor capable of diagonal components

texts:
I've found several great editors capable of vertical and horizontal components, but none that can do diagonal ones. Are there any available?

Edit - This is purely cosmetic. I've just started an introduction to circuits course and a  good deal of the exercises involve diagonal components. AFAIK, in all cases these can be redrawn to vertical-horizontal schematics, but I'd like to show the original circuit as well.


texts: What components are inside a port expander, how does it work? (Are they tiny MOSFETs?)

texts:
Do port expanders use MOSFETS internally to switch the pins high/low?
My project is using a Raspberry Pi and a MCP 23017 port expander to sink some current (to GND through the port expander) from a variable resistor (200-400 ohm) at (3,3 volts from the Pi).
I have noticed that the port expander is not a perfect short circuit to GND and have measured a voltage drop between the pin of the port expander and GND.  This voltage drop increases when a higher current is sunk through it to GND. Stupidly, I was expecting the only voltage drop to be across the variable resistor (or most of it.)
Sourcing and sinking current through the GPIO of the Pi works as I thought, with a 3,3V drop across the resistor.
In the MCP 23017 datasheet, (under param No. D080) it says when MCP is operating at "Output-Low-Voltage" the voltage drop across the MCP23017 pin to GND will be 0,6V when the Iol (sunk current) is 8mA and the Vdd (supply voltage of MCP) is 4,5V. This would explain my problem.
I'm looking for literature / links explaining the basics of (I/O) port expanders which I can reference in my bachelor thesis which explains this.
So far the only thing Ihave come across is this link.
From my understanding a MOSFET has a set (Rds on) resistance when on, but the port expander resistance changes based on the current sunk or sourced.  Why? Do they internally use MOSFETs?