texts: Power switch - IN and OUT connected all the time

texts:
A while ago, I asked about detecting whether a power jack is connected or not, in order to select power source from USB or DC jack.

You can see the question here: Power selection circuit for USB or DC Jack - both at 5V

I finally put together this circuit:

On the input I expect a 5V supply.

I use a voltage divider (VJACK/2 = VSENSE -> going to a 3.3V uC input) to know if there is voltage at the DC jack (V-SENSE goes to a uC pin), and if there is enough voltage, I want to enable the power switch (AP2501M8-13 active LOW) in order for it to deliver the power for the rest of the circuit.
Also, I'd like to detect if there isn't power (the DC jack was disconnected, or no voltage in the power supply), and in this case, disable the power switch.

I need this, cause I have two power modes in my system, and the HIGH power mode needs the power supply to run.

The problem I am having is that after unplugging the DC jack, I still have 5V in VIN and VJACK, so I can't detect with the micro controller a disconnect.

After unplugging the DC JACK, with the microcontroller, I enable and disable the power switch (EXT_POWER_EN line), and I still have 5V at the input. I would think that after disabling it, the input of the switch would go to 0V, dischargin C10 through R7 and R8.

I don't know if it's the power switch, that is bi-directional, or that it is not meant to be used like this, or that the 5V are leaking from somewhere else to the input, but I can't find the root of the issue.

I removed the C10 capacitor, to check if the problem was that it got charged, and could not discharge, but the problem persists without C10.

EDIT: Also, after connecting and disconnecting the DC Jack, if I touch VIN with a jumper wire to GND, it stays on GND, it doesn't get back up to 5V.

Any help appreciated!


texts:
Hi Now I'm trying to understand how does the NAND Flash reading work.
AS I know, when the NAND FLASH reading work, the gate voltage go to 5v.
then electrons flow depend on holes. then we can read current.
But I can't understand this exactly. Would you please help me to understand this?
Even I want to know MLC and TLC.
Might be a little bit need to clarify.
update question.
Could you please let me know especially how does voltage controlling work to read?


texts: Electrical installation: how to label wires?

texts:
When installing it is of course useful to label the wires to avoid having to trace them when modifications become necessary. I was wondering what people are using for this.

The following solutions I found unsatisfactory:

isolation tape: the glue is too "liquid"/"soft" causing the tape to slide on the wire and leave sticky residue. Also it tends to become even softer in warm environments and falls off over the span of a few years.
brown packing tape: while a good solution short term, the glue becomes hard and pulverises over the span of a few years causing the labels to fall off


texts: Simplest way to upload sketches onto "hackduino" without having a arduino duemilanove

texts:
Update: The ATmega came bootloaded with the arduino software is that can simplify anything

I have this board:

I'm looking for a bone-simple way to upload sketches.

Ideally without buying additional components...  Double points if you've got a http://fritzing.org/ diagram!


texts: My country's voltage is 220 and I want to recharge a Japanese cellphone (100V), what should I use?

texts:
I live in the Netherlands and can't recharge my Japanese cellphone because I think it's due to the difference in voltage.
What should I use in order to recharge it anyways?

Thanks!!


texts: Possibility of an extremely directional antenna

texts:
I'm fairly new to RF technology, but a direction-finding application has come up where a highly directional antenna can offer a convenient solution, so I started searching for such antennas.

Most, like Yagi antennas, that can be purchased seem to have gain patterns that are not very focused, with half-power beamwidths of no less than 30 degrees, often much greater.

Is it possible to design PCB antennas (or alternatively, purchase pre-made antennas) with a very narrow/focused radiation pattern -- Ideally, I'm looking for a small (size < 10 cm) antenna with a half-power beamwidth under 10 degrees? Assume any transmission frequency between, e.g., 433 Mhz up to 10 GHz is acceptable (because the application has some leeway in this).

What keywords should I research for this, or are such antennas impossible due to scientific limitations?

For example, Wikipedia contains this image within a radiation-pattern article, but I haven't yet been able to find an antenna with such favorable pattern:


texts: Confusion in linking H and B in an inductor

texts:
There are two basic definitions in magnetism for circuit theory:

1-) Magnetic flux density = Magnetic flux / Area

  B =  / A

2-) Magnetic field strength = Magnetomotive force / Length of the flux path

H = mmf / l  (mmf = N * I) so:

  H = N * I / l

But there is also a relation between H and B such as:

  B = μ * H

I don't understand how the equations 1 and 2 yield B = μ * H.

1 and 2 are defined independently but still B and H has a relation which is also defined separately. I'm confused at this point. 1 and 2 are definitions but I cannot link B and H using these two definitions.


texts: How do I connect the wires on a PC Power Supply that supplies +3.3V, +5V, +12V, -12V, and +5Vsb to make 15 Volts for Peltier module?

texts:
I've selected the Corsair CS450m as the PSU. I also found a 12V DC 30A 360W Switching Power Supply on eBay for about $54 AUD (I'm not allowed to show the link), but I wouldn't know how to get it to output 15V.

The Peltier Module is rated at as 15V at 8A (Using 60 Watts/h) and the heatsink (Deepcool Ice Blade Pro V2.0) has a 12V fan that uses 3 Watts (0.25A).

I also have a Ultrasonic Mist Maker to help cool the heatsink, through evaporation. Look for a video on YouTube titled: "thermoelectric Peltier TEC cooling with ultrasonic humidifier" to see what I'm talking about.

The mist maker is an AC device, so it'll have to use a wall socket.

The purpose of this, is to create an affordable water chiller for my Hydroponic DWC Reservoir, which needs to be kept under a certain temperature. To do this, do I need to cut the power to the PSU once the water reaches a certain temperature? How does a Temperature Controller turn off the power? Is there a way it can turn off both devices?


texts: How to connect op-amps serially in high frequencies?

texts:
Assume I have a 50MHz signal with 300mV pk-pk amplitude and I want to amplify it to 8v pk-pk. For this purpose I selected AD8055. This is a 300MHz VFO that is suitable for this purpose. I selected resistor values according to its datasheet (Table3 page 16). As the maximum gain with that config is 10, I need two op-amps connected in series (schematic below) hoping the first device produces a 10 fold gain and second one a 2.2 .

The first one produces a 3 volt that is OK. but the second one's gain never goes higher than 1 ( the total never goes higher than x10).

This problem is just seen in high frequencies (in lower frequencies as 1MHz it can make a 9v pk-pk output). The supply voltage is +/-5v. The first output is 3v pk-pk that is well below the maximum input (+/-2.5v) for the second one.

I tried using different resistors ( a Pot) between 100ohms- 1k but the second Op-Amp gain never goes higher than 1. I also tried attenuating the input voltage ( reduced it to 100mv). In this case the first output becomes 1v (gain=10) and the second output can exceed unity (it reaches gain=3) but finally the total output is  3v pk-pk yet.

Is there any consideration that I am missing?


texts: Definition of "hot" resistor when calculating RMS thermal voltage?

texts:
I am calculating the RMS thermal noise voltage of a "hot" resistor of a tutorial sheet for uni. I have used the standard Johnson–Nyquist formulas, but the answer sheet does not include the entire formula.

The equation I am using is

$$v_n = \sqrt{4 k_B T R \Delta f}$$

But the answer sheet omits the 4. Would this be because it is a hot resistor or a mistake on my worked solutions?

Also my research tells me that a hot resistor is just that, a resistor above 65 degrees Celsius, am I missing something here? Is there another meaning?


texts:
I am running a RGB strip of 5 meters with 30 pixels/m with 5 V/6 A. But I will be running different lengths soon ranging from 10 m to 50 m. To avoid buying multiple power supplies for every 5 m, I have purchased a 5 V/60 A 300 W power supply.

Will this burn my LED strips if I don't use the whole 60 A? Can I still use just 10 m at 30 pixel/m without burning it out?


texts:
Looking at features of xmega avr mcu here: https://www.microchip.com/wwwproducts/en/ATxmega32A4
I am wondering why there is so big support of spi or i2c. There are 5 spi buses. What is the practical use? I2c and even spi can use the same bus for many counterparties and even when there is hardware support, so you can really communicate on more buses at once, i cannot imagine need for 5 spi buses.

So the question is: Do you have any real  world example of such use? I can imagine external memory having its own bus as advantage. Anything else?


texts: What is the structural difference between a high-drive and a low-drive cell?

texts:
I've come across IC's that are labeled high-drive and low drive. I know that a high-drive IC has a higher intrinsic propagation delay but isn't as steep as a low-drive IC in function of the load to drive.

If I were to design both a high-drive and a low-drive NOT-gate (or any other logic gate), what would the difference be between the designs?

In the picture the dotted line is the high-drive cell and the full line is the low-drive cell.


texts:
Over Christmas I started thinking of putting together some nice lighting for the house. The main element I'm thinking of is a strip of LEDs that are individually addressable. The only ways I can think of to achieve this without running to many wires tend to get expensive quickly (> 1 euro per LED). Since I also don't really know what to search for, I figured I might ask for pointers here.

In summary, what I am looking for is a communication bus protocol that can address approximately 50 nodes (the LEDs) and that can be implemented with very cheap electronics (<1 euro per node). Each node only needs one bit of data (LED on or off), but more would be handy e.g. to set the intensity. I think my best bet is some sort of master-slave configuration in which case the master is allowed to be more expensive, let's say an Arduino. Is it possible to build such a network and where should I start looking?


texts: How to calculate resistance to use along with NTC 103 thermistor to measure temperatures between 0-100 degrees celcius

texts:
I am a complete noob to temperature measurement. I initially tried to measure temperature using LM35 but i got negative values at room temperature and the values were fluctuating a lot.
I want to try to measure temp between 0-100 degrees Celsius using thermistor and found out that need to connect one end of the thermistor to a resistor and then to ground for voltage divider rule. How do i calculate this resistance. i randomly tried 10K ohms and am getting room temperature values, but it is not measuring any higher. i also tried 100k and 3.3k but i am getting extremely small or negative values even at room temperature.I hope you guys can help me out.


texts: Replacing some old SKE 1/04 diodes for newer and quieter ones

texts:
I´m working as a hobby on a early 80´s amplifier and it has SKE 1/04 diodes at the rectifier.
I pretend to make some upgrades, such as nichicon muse caps and I would also like to replace this 40 years old diodes with some newer and quieter ones.
Could anyone suggest a better option ?
Thank you all in advance.


texts: My thought on the reverse polarity protection

texts:
I am now designing a power reverse polarity protection circuit for my system. I found that most methods used for the protection would cause voltage drop in the power path. Even the MOSFET, which has maybe 0.025ohm Rdon, would cause about 5mV drop(0.2A). Some may not cause voltage drop but would be a little complex or not resettable. http://www.wa0itp.com/revpro.html

Then I have a new thought(maybe new or maybe not). My design is showed below. My circuit has three power sources(+-12V and 0V). I add two diodes between +12 and 0V and between 0V and -12V with big enough series resistors.

Normally, the two diodes would turn off.No current would go through R1 and R2. So no voltage drop when normal operation. If the polarity is reverse,D1 and D2 would turn on. Current would go through the diodes.

Is there any problem in this circuit? Can it work?

simulate this circuit – Schematic created using CircuitLab


texts: I have an error on stm8s like "CAN cell did not provide an empty mailbox"

texts:
I'm using STM8S208 MCU with IAR. I try to send any data on CANBUS. I have written init codes in USER_CAN.c like below:
#include "USER_CAN.h"

uint8_t CAN_FIFO[8] = {0,0,0,0,0,0,0,0};

void USER_CAN_Init(void)
{
  /* Init Parameters*/
  CAN_MasterCtrl_TypeDef        CAN_MasterCtrl     = CAN_MasterCtrl_AllDisabled;
  CAN_Mode_TypeDef              CAN_Mode           = CAN_Mode_Normal;
  CAN_SynJumpWidth_TypeDef      CAN_SynJumpWidth   = CAN_SynJumpWidth_1TimeQuantum;
  CAN_BitSeg1_TypeDef           CAN_BitSeg1        = CAN_BitSeg1_8TimeQuantum;
  CAN_BitSeg2_TypeDef           CAN_BitSeg2        = CAN_BitSeg2_7TimeQuantum;
  uint8_t                       CAN_Prescaler      = CAN_PRESCALER;
  CAN_InitStatus_TypeDef        InitStatus         = CAN_InitStatus_Failed;

  CAN_DeInit();                 // CAN register ayarlari resetlendi
  InitStatus         = CAN_Init(CAN_MasterCtrl,
                                CAN_Mode,
                                CAN_SynJumpWidth,
                                CAN_BitSeg1,
                                CAN_BitSeg2,
                                CAN_Prescaler);

  if(InitStatus != CAN_InitStatus_Failed) { /* error notification */ }
}

void USER_CAN_Filter_Init(void)
{
  /* Filter Parameters */
  CAN_FilterNumber_TypeDef      CAN_FilterNumber      = CAN_FilterNumber_0;
  FunctionalState               CAN_FilterActivation  = ENABLE;
  CAN_FilterMode_TypeDef        CAN_FilterMode        = CAN_FilterMode_IdList;
  CAN_FilterScale_TypeDef       CAN_FilterScale       = CAN_FilterScale_8Bit;
  uint8_t                       CAN_FilterID1         = (CAN_FILTER_ID_1 >> 3);
  uint8_t                       CAN_FilterID2         = CAN_FILTER_ID_2;
  uint8_t                       CAN_FilterID3         = CAN_FILTER_ID_3;
  uint8_t                       CAN_FilterID4         = CAN_FILTER_ID_4;
  uint8_t                       CAN_FilterIDMask1     = CAN_FILTER_ID_MASK_1;
  uint8_t                       CAN_FilterIDMask2     = CAN_FILTER_ID_MASK_2;
  uint8_t                       CAN_FilterIDMask3     = CAN_FILTER_ID_MASK_3;
  uint8_t                       CAN_FilterIDMask4     = CAN_FILTER_ID_MASK_4;

  CAN_FilterInit(CAN_FilterNumber,
                 CAN_FilterActivation,
                 CAN_FilterMode,
                 CAN_FilterScale,
                 CAN_FilterID1,
                 CAN_FilterID2,
                 CAN_FilterID3,
                 CAN_FilterID4,
                 CAN_FilterIDMask1,
                 CAN_FilterIDMask2,
                 CAN_FilterIDMask3,
                 CAN_FilterIDMask4);
}

void USER_CAN_Mode_Init(void)
{
  CAN_ModeStatus_TypeDef        modeStatus;
  CAN_TTComModeCmd(DISABLE);  // (CAN Time TriggerOperation) Zaman tetiklemeli CAN operasyonu kapatildi

  modeStatus = CAN_OperatingModeRequest(CAN_OperatingMode_Normal); // Istenen moda girilip girilmedigi kontrol ediliyor
  if( modeStatus != CAN_ModeStatus_Failed)
  {
      // hata bildirimi
  }
}

void USER_CAN_Config(void)
{
  USER_CAN_Init();
  USER_CAN_Filter_Init();
  USER_CAN_Mode_Init();
  CAN_ITConfig(CAN_IT_FMP , ENABLE);  // (message pending interrupt) Mesaj alma interrupt'i açildi
}

And then written transmit code in main.c like below:
transmitting_resunt = CAN_Transmit(CAN_ID,CAN_Id_Standard,CAN_RTR_Data,1,(uint8_t*)DATA);

I had examine transmitting_result on debug mode and I've realised
transmitting_result = CAN_TxStatus_NoMailBox

CAN_TxStatus_NoMailBox means "CAN cell did not provide an empty mailbox"
How can I solve this problem?


texts:
simulate this circuit – Schematic created using CircuitLab

Both diodes are assumed to be ideal. The current source has I Amp current through it .I am not sure about the voltages at the cathode of diodes and thus I am confused when the diodes will be turned ON and OFF.
So How we can decide that when the voltage at A and B is Low then both diodes are OFF because it might be case that voltage at cathode is much Lower or negative than anode.I mean how we decide that diodes are ON or OFF when we know the anode voltage only


texts:
I am trying to design a 10 bit DAC using an R-2R ladder. I hope to achieve a signal that can vary from -5V to 5V.

In the circuit provided, I am showing my design for 5 inputs. I have used Mosfets instead of directly connecting the MCU I/O pins to the DAC because their resistance varies a lot with the temp.

My question is, does this seem like a viable circuit in terms of generating the desired output signal.

This is my first time on this site so if I violated any of the posting rules, I apologize.

Thank you for your time!

*Update: I have adjusted the requirement of the DAC to produce a 0 to 1V signal which I will adjust using an opamp.

Based on the replies, I believe this circuit should do the trick!


texts: Reading data from register file in system verilog

texts:
I'm creating a simple register file in system verilog, with a total of 6 registers that can be written to/read from. When I run a simulation in ModelSim, the output never shows the correct data - it stays at 0 and ignores any read signals. This led me to believe that either a) the values I'm writing to the registers may not be getting stored, so when I try to read a value from one of the registers they don't output anything, or b) data is being written to the registers, but I'm not pulling the data from those registers correctly.

Here is my .sv file:

module register_file#(parameter bits = 16, registers = 6)(clock, write_enable, write_reg, data_in, read_reg0, read_reg1, data_out0, data_out1);

    input clock, write_enable;
    input [2:0] write_reg, read_reg0, read_reg1;
    input [bits-1:0] data_in;
    output [bits-1:0] data_out0, data_out1;

    wire [bits-1:0] data_out0_wire, data_out1_wire;
    reg [bits-1:0] data_out0_reg, data_out1_reg;
    reg [bits-1:0] r1, r2, r3, r4, r5, r6;

    assign data_out0 = data_out0_reg;
    assign data_out1 = data_out1_reg;

    always @(posedge clock)
        begin
            if(write_enable)
                case(write_reg)
                    1: r1 = data_in;
                    2: r2 = data_in;
                    3: r3 = data_in;
                    4: r4 = data_in;
                    5: r5 = data_in;
                    6: r6 = data_in;
                endcase
            data_out0_reg <= data_out0_wire;
            data_out1_reg <= data_out1_wire;
        end

    always @(read_reg0)
        case(read_reg0)
            1: data_out0_wire = r1;
            2: data_out0_wire = r2;
            3: data_out0_wire = r3;
            4: data_out0_wire = r4;
            5: data_out0_wire = r5;
            6: data_out0_wire = r6;
        endcase

    always @(read_reg1)
        case(read_reg1)
            1: data_out1_wire = r1;
            2: data_out1_wire = r2;
            3: data_out1_wire = r3;
            4: data_out1_wire = r4;
            5: data_out1_wire = r5;
            6: data_out1_wire = r6;
        endcase

endmodule

Edit And here is my testbench:

`timescale 1ns / 1ps
module test_partC();

   reg  clk,write_enable;
   reg [2:0] write_reg, read_reg0, read_reg1;
   reg [15:0] data_in;
   reg [15:0] data_out0, data_out1;
   register_file dut (clock, write_enable, write_reg, data_in, read_reg0, read_reg1, data_out0, data_out1);

   // Toggle the clock every 10 ns
   initial
     begin
        clk = 0;
        forever #10 clk = !clk;
     end

   initial
     begin
        write_reg = 1;
          write_enable = 1;
          data_in = 10;
        #20;
        write_reg = 2;
          write_enable = 1;
          data_in = 15;
        #20;
        write_reg = 3;
          write_enable = 1;
          data_in = 20;
        #20;
        read_reg0 = 1;
          write_enable = 0;
        #20;
        read_reg0 = 2;
          read_reg1 = 3;
        #20;
        read_reg0 = 1;
          write_reg = 1;
          write_enable = 1;
          data_in = 30;
     end

endmodule

I added an extra set of registers from the data_out signals in trying to find a potential solution to the problem I'm having, but I'm not sure if that changes anything.

What I was trying to do was, based on the number from the read_reg signal, read the value from the corresponding register, which sends the signal down the data_out_wire, stores it in a data_out register, and then sends the signal out via a wire (output data_out).

I'm new to system verilog and I'm struggling to figure out where I went wrong, any help is greatly appreciated.


texts: Sensing inductance change in high power (20 watts) wireless transmitter

texts:
First post here.

I have a built a wireless power transmitter that consists of 2 flat spiral coils that transmit about 20 watts across a short distant to power a heating element. The coils inductance is roughly 7uH.

At the moment I have the oscillator circuit so that it is powered off until the receiving coil is placed over the transmitting coil, in order to sense that the coil is real and not a foreign object. To do this, I have placed a Hall effect sensor on the base with the transmitter and a small magnet in the middle of the receiver. Obviously under RF power, the induced magnetic field in the transmitting coil heats the sensing magnet up pretty hot! It works, but it not elegant.

I would like to do something different but not sure how. I'm pretty sure the transmitter coil inductance will slightly change when the receiver coil is near. I would like to detect that change in inductance and trigger the oscillator. I tried to build a RLC circuit which is pinged at a known frequency then measure voltage. This works at low power I found, but now at high power as I damaged my circuit. Can anyone provide any guidance on this?

During transmission, the entire circuit draws 6.5A @ 12V with a load designed for max power transfer.

Also, if there is a better/simpler/elegant method to accomplish this, please tell!

Thanks


texts: We designed a power supply for an iOT. The uses SoCl2 battery and solar panel combination. The circuit is functioning and we are getting 3.26v consistently for over 3 days now. LTC3106 is configured for 3.3v configuration.  At VCC pin we are using 0.1uF instead of 0.01uF since datasheet says 0.1uF can be used. Does the value of capacitance make any difference ? Any other factors to consider to account for voltage drop ? Noise could be one possibility.  Any suggestions or recommendations appreciated. Thanks!


texts: Choose the right resistor for your RGB led (calibrate the colors)

texts:
Calibrate RGB leds with the correct resistor

Playing around with some microcontrollers and multiplexed leds i noticed that i always need to fix the colors of each led rgb output softwareside... thats a pain...

Microcontroller's pwm output has an output of 255 different values.

By mixing a color with rgb leds you do some math... i like hsl(hsv in mc's) and convert it to rgb values.

So if i want yellow  i need theoretically turn on the red and the green at 100%

rgb(255,255,0);

nope... it's not yellow...

here the lighness is not considered...the real rgb values should be less than 255 pwm.
all set to 255 should return white.
the blue and the green leds are brighter.

in my code i have something like that

red*1
green*0.2
blue*0.15

i use only 15% of the blue led when mixing the colors.20% of the green one.

The maximum value of pwm used is 38

  38 of 255 possible values. A waste!

Those are the resistors i need to properly power the leds.

Red: 5v@2.1v-20mA  = 150ohm

Green: 5v@3.2-20mA = 100ohm

Blue: 5v@3.1v-20mA = 100ohm (corrected error 2,1v vs 3.1v)

How can i calibrate the leds hardwareside?

I know i need only 15% of the emitted light comming from the blue led... what resistor should i use?

Is there some sort of calculation that allows me to set the correct resistor based maybe on the wavelength or other carachteristics contained in  the datasheet?

Would a Simple LDR help to calibrate those leds?

If i find the correct resistors for a nice hue based on a lightness of 50% what would return rgb(255,255,255) ??? white or not?

What you do to get a nice visual hue on rgb leds?

this for shure would also help to solve some issues on another question i made some time ago

LDR + RGB Led = Color sensor. How to calibrate it?


texts:
I have built the following H-bridge driver circuit (The red resistors R9 and R10 were not included). However during testing I have found that I am constantly blowing the high side P-Channel MOSFETS which has lead me to believe the driver circuitry has problems.

After a bit of thought I believe the high side the driver circuit needs to include the two red resistors (R9 and R10) which were absent from the original design.

This leads me to the following question regarding H-bridge/driver design:

Am i correct that the Resistors R9 and R10 must be included for correct operation?
What is the the expected behaviors/performance of the circuit without the added R9 and R10?
Are there any further issues with my circuit I may have missed?
Is there any reason why is the High side P-channel MOSFETS are blowing and not any of the P-side MOSFETS?
The motor is NOT being driven using PWM (hence no fast switching circuity). However I accidentally constantly drove the motor with a PWM during testing (not switching directions), could this have caused my MOSFETS to blow?


texts: I wanted to have a footprint for capacitor having mouser no: 710-860020475016 and package: AL10x10.5 . Please tell me how i can find that specific part and foot print for Altium designer. I have looked into all Altium libraries but didn't find that component.


texts:
I want to identify a rechargeable battery pack from inside an old portable hard-drive.

It is unlabelled. (I ripped open the blue covering - it isn't labelled on the internal metal cover either.)

Battery is ~55m x ~33m x ~5mm - so relatively flat. The plug is 3-4 mm wide.

Device takes +5V DC, so I imagine that is the charging voltage.
One part of the circuit takes 3.3V DC, so I imagine that's the output voltage.

How is this battery specified?


texts: Transistor in the Darlington pair getting burned?

texts: I have a relay board controlled by an STM32 to switch two AC loads (a compressor and an MD40 pump). The circuit seems to work fine but after about a day of operation, my BC847 got burned and the LM3940 LDO which supplies the STM32 with 3.3V was heating up too much. This happened again and again. I can't figure out the root cause of this issue. The load is a compressor which takes about 5A from the AC supply. A 12V supply feeds the relays and the voltage regulator (an LM2576 and LM3940) that powers the STM32.


texts: Finding the voltage and current at t = 0 using Step Response

texts:
The question that I'm trying to solve is as follows:

In the circuit shown below, the switch has been closed for a long time. a) What is v(0) or the voltage across the capacitor immediately after the switch is opened? b) What is i(0) and i1(0)?

First, I calculated for the voltage before t = 0 using voltage division. I arrived at v(0-) = 4V. Since the capacitor voltage cannot change instantaneously, I assumed that 4V is the voltage at t=0.
Here's the tricky part. I'm asked to find the current at t = 0. By looking at the diagram, I am certain that the 1-ohm resistor is short-circuited, so I simply dismissed that and used Ohm's Law to find i1(0-) using v = 20 V and R = 4 ohms. In the property of short circuit, the i is equal to 0.
Are my solutions for i1 and i legal to begin with? I'm only confident with 4V as the voltage at t = 0.


texts: Does polarity matter for a DC rechargable battery?

texts:
I have a handheld wireless rechargable mini-vac (like a Dustbuster). The charger outputs 19V DC 150mA.

My cat chewed through both wires on the adaptor. Both wires are completely black with nothing to indicate what's positive/negative. The plug and the barrel jack/coax connector both solid moulded plastic with no clues either. I've spliced them back together but does the polarity of the wires matter?

I vaguely remember from physics at school that if you reverse connections to an electric motor it spins in the other direction. In this case, would it force the vacuum's battery to discharge and then not charge? Or damage the vac altogether?

Does it matter or should I just buy a new adaptor?


texts:
I am working on a project to interface LSM9DS0 with a MSP430.
Looking for a driver in C / C++ that I can use as a reference design.


texts: creating symbol for Transmission gate switch in ltspice

texts:
I need to create a symbol of transmission gate to use but when putting its symbol I get a message "unknown subcircuit called in xx1_nc01_nc02_nc03_nc04
how may I fix it?


texts: Brushed DC motor chassis connected to each terminal

texts:
I'm attempting to build a cart which will be steered with two deferentially driven electric motors.

The motors I've chosen are and brushed DC worm drives, mainly for the high torque and low price. I believe the motors were intended for use as automotive windscreen wiper drivers, but the seller knew very little information about them. From testing and the poor information provided; powering the motor via the black and green cable drives the motor slowly, powering by the black and blue cable drives the motors at a higher speed, also if you connect blue and green cables its goes faster still. While the yellow and red cable seem to be used like some kind of an encoder (unimportant/unused).

The Brushed DC wormdrive motor.

The issue I'm having is the h-bridge motor drivers I've been using have been working for short periods of time before inexplicably dying.

Testing various properties of the motors it was found that both the green and blue wires had low resistance paths to the chassis (approximately 1.2 ohms each). This occurs even when the screw seen in the picture of the motor connecting the back wire and chassis is disconnected.

Would/could this be the cause of the fault? Does anyone have any insight of what could be happening with the motors internally?


texts: We have an electric floor sweeper at work which uses two 12 volt deep cycle batteries in series to supply 24 volt. The floor sweeper was not starting up on switch on so I connected two 12 volt lead acid batteries in series to the floor sweeper in parallel as one would if jump starting a motor vehicle with a 24 volt power system. In hindsight this was not a good choice because upon connection one of the lead acid batteries violently explode lacerating my face with a piece of the plastic case but luckily no acid entered my eyes although extensive flushing of the eyes at work and later at the doctor was performed as a preventative measure. I am wondering what may have caused this explosive situation but my guess is that there was a fault in one of the floor sweeper batteries, possibly a dead short which lead to this explosion. What are peoples thoughts on this please and how may I have better tackled the diagnosis of this no run situation in the first place please.I realise that in hindsight I should have charged the floor sweeper batteries but they did not seem to be accepting a charge from the battery charger supplied with the unit.


texts:
In this stack-up what are those presented in right-side of picture?

update:

The person who respond from manufacturer told me that is "residual copper ratio". But I think she is misunderstood because there is nothing about it on the web!
This is from PCBway, and I think it is maybe 4350B since I have other 6layer stackup like in the picture attached, that they have written 4350B next to it's (Roger layer) percent number.

Update regarding to Elmesito's answer:

Can your theory (%s are the compressing ratio of thicknesses) explain this other stack-up and "residual copper ratio"in last paragraph?


texts: M.2 PCIe x2 and SATA connections and key/notch with SATA/PCIe x4 SSDs

texts:
For my current project I am adding an M.2 slot for additional storage. Even though SATA data throughput is more than sufficient I would like to support both SATA and PCIe based SSDs, as I dont know what will be more/less available and affordable in future.
M.2 Keys
The M.2 connectors use keying notches in different positions, depending on the provided interfaces. Each key position is identified by a letter.

Key B: SATA + PCIe x2 (+ others)
Key M: SATA + PCIe x4

A quick search for M.2 SSDs on amazon showed that most NVMe/PCIe based SSDs use Key M, while SATA SSDs use a combined Key B and M. Therefore, for maximum compatibility, I need to use Key M.
Available System Interfaces
My system has one SATA and 2 PCIe lanes that may be connected to the M.2 receptacle, what is the requirement for Key B. I am missing 2 PCIe lanes for key M.
Plan
I plan to use the M key for maximum mechanical compatibility and would like to provide one SATA and 2 PCIe-Lanes on the M.2 connector.
Questions

Do all NVMe/PCIe based SSDs work with 2 instead of 4 PCIe lanes?
Is there a requirement on which PCIe lanes need to be used in this case?
How may the two PCIe lanes that are not used be terminated?


texts:
I need to find R,C and switching frequency of the following circuit such that  Switching Frequency is low as possible with given Vu and VL.

Also how can I improve the circuit so that it can reach it's output voltage quickly with good transient respond.


texts:
Why do some people use some sort of gain either external amps or the one built in to the ADC itself and not just do the calculation in software. I do not think its that expensive of a processing power to multiply the output of the ADC in software instead of using a hardware alternative. Gains done via hardware also presents offsets which you will need to account. Gain also amplify the noise that we dont want.
A counter argument would be that what if your ADC dont have enough resolution to read the signal. I can totally understand that argument, but even the high percisions 24 bit 32 bit ADCs have built in gains or their inputs has gain amplifiers connected to them. Those ADC are capable of reading at such low value that its actually very hard keeping the noise levels down that those adc wont notice. So in the case of 24bit and above ADC gain is not needed??
So why does it seem that its always better to do it in hardawre compared to doing it in software.


texts: Can the "unknown" turn-on state of registers in digital circuit be used as seed for random number sequence?

texts:
We always like to reset registers in a synchronous digital circuit just after power up so they are in a known state before device operation begins.
Pseudo random number sequences make use of a seed value. The rest of the sequence generated by the generator then relies on this seed value in a predictable way.
Is it a good idea (say in FPGA or some other device) to use the initial state of group of registers (that are never reset) as the seed value in pseudo random number sequence?


texts:
I am currently looking at generating a signal to blink a led with a 10ms duration every 2 seconds. I was thinking to use a 555 timer to do so, but I don't see how to change the duty cycle to make that off time is different than on time.

I want to avoid the use of an MCU if possible to save energy.


texts: RGBHV (VGA) to YPbPr Converter and Waveforms?

texts:
Purely for hobby, I am working on an RGBHV (VGA) to YPbPr (Component) converter circuit for old games consoles modified to output RGBHV on a VGA cable.  From the game consoles, the RGB signal is taken from before the composite encoder chip and the HV sync signals are generated by a TI LM1881 chip being fed with composite video from after the composite encoder chip.  This creates valid 15khz VGA that works with my VGA capture card for high quality video capture.

Now, the converter I am working on needs to take this VGA signal and convert it to YPbPr to display on a CRT TV.  In my inexperienced attempt at scrapping this circuit together, I have used two LT6550 chips and Linear's application note.  Here is the circuit: Exported circuit with annotations (Import & Simulate in http://www.falstad.com/circuit/).  I have also attached a picture.  The top part (RGB->YPbPr) is pretty much verbatim from the application note, the only thing I have added was the bottom part for adding the sync information to Y.

My two questions are:

What are the waveforms supposed to look like for YPbPr?  I can find heaps of information on google about composite video, VGA, and some about the Y component and understand what those waveforms are supposed to look like on-the-wire in an actual application, but PbPr information seems scarce as far as actual oscilloscope style displays go, even though I know Pb is 0.565(B-Y) and Pr is 0.713(R-Y).  In a month or two I will be able to look at the waveform with an osc. myself.

Are there any glaring problems with the circuit?  Not knowing what the waveform is like, I find it odd that Y is -300mV sync 0mV to 700mV signaling but Pr and Pb are -350mV to 350mV signaling.   Does this mean I need to AC couple Pr and Pb?  Or do I need to level shift Pr and Pb up by 350mV?  Or are these voltages valid?  I prefer DC coupling wherever possible, I have had crappy black levels with AC coupling in the past somewhat mitigated by larger capacitors.


texts: Is a neutral back to main feed from satellite circuit box necessary if neutral is bonded to ground remotely?

texts:
I have a shed about 300 feet from my house. There is a circuit breaker box with two 20 amp breakers. Each breaker feeds a single 20amp outlet. Each breaker is connected to a #6 stranded wire that go back to a 30 amp breaker in the main panel. There is not a neutral or ground going back to the main panel.

In the box in the shed, the outlet ground and neutral go back to a neutral bus that is bonded to the ground bus. A single #6 solid copper ground wire connects to two eight foot long ground rods  (the rods are about 8 inches apart if that matters). This setup was installed by a previous owner and has worked for years to power a light and some tools, and sometimes a space heater. Recently, a friend said I had to run a #6 neutral wire back to the main panel, but could not tell me why it had to be done.   I looked in the main panel, and all the neutrals and grounds go to the same buss. This new wire would be pretty expensive and I don't want to do add it if it is not necessary.


texts: SPI Altera master IP not behaving as expected

texts:
Using Platform designer on Quartus, This is a system with Nios and SPI IP.
The code on the nios is attached. This code is supposed to drive the MOSI output to 1 forever, the MOSI on the waveform is always 0. Why??


texts: How to change V and F in constant V/F control of an ACIM?

texts:
If I generate 3-Phase PWM outputs to drive a 3-phase ACIM and use constant V/F method for speed control then how will I change V and F of the generated PWM outputs?

I will generate PWM's using LUT method. What I understand is that by changing the PWM duty cycle sinusoidally I can generate the PWM but how to change its voltage? and Frequency?


texts: Why did my LiPoly Charger fail when I connected my cell

texts:
After having burned a small hole in my finger, I'm trying to figure out why exactly the Micro-Lipo charger heated up instantly.

I am using the Adafruit Micro-Lipo charger

which has the following specs:

3.7V/4.2V LiPoly/LiIon
100mA charge rate default
Short jumper for 500mA

I had connected a 3.7V 1200mAh battery to the terminals where the entire board heated up instantly. The battery is an uxcell 603450.

Was this because the mAh rating on the battery was way too high? There was no power source connected to the MicroUSB port on the charger.

If it is the size of the battery, how do I calculate what size charger I need in order to charge 3 of the 3.7V 1200mAh batteries wired in a series?


texts: Electret microphone with class a amplifier has no speaker output

texts:
I' m a relative beginner trying to build this audio amplifier, using this electret microphone, and output my sound to this 8 ohm speaker.

I'm getting no audible output.

I tested the microphone only, with no amplification, and there was indeed a small response, ~15mV and ~4uA (loud radio near the mike). So it seems like the mike is at least providing a signal.

With the amplifier, the output response is ~350mV, 70uA (again, with a loud radio near the mike). This is much larger than before, but it still seems small to me.

Should I be getting an audible response?

Is it actually necessary to amplify the signal again?


texts: Heating wire filament with low voltage / amps

texts:
Is it possible to heat either nichrome or copper wire (both 40 awg) with the following low-power delivery of 3.5 Volts, 7.4mW and 2.11mA?

This is very low power delivery and we're wondering if 3 inches of coiled wire (40 awg at .0031 inch diameter) could be heated to speed the evaporation of certian liquids?

Would a high resistant wire (nichrome) or a low resistant wire (copper) get hotter at low power?  How hot would they get?


texts: I am working on a Vehicle Tracker project. I have few digital inputs coming from vehicle system & their voltage level is 90V. These should go to Micro controller GPIOs which are @ 3.3V. What are the ways to connect these??


texts: Measurement of Isolation in a Directional Coupler

texts:
I want to measure the isolation of the following directional coupler (for more details of that specific component, go here).

Isolation can be evaluated through the scattering parameter S21, but how can I measure it? Obviously I can measure S14, S41, S13, S43, S31, S33... but what about S21? I cannot connect port 2 to a vector analyzer because it is internally terminated on a 50Ohm load.


texts: Error on Simulating 8-input NOR gate with Proteus 8

texts:
I`m new to Proteus.

I want to simulate a logic circuit with Proteus 8, I want to use an 8-Input NOR Gate (4078) and some 4-Input AND Gates (4082), but when I want to simulate, there is some Errors :

No model specified for U12. [U12]
No model specified for U15:A. [U15:A]
No model specified for U15:B. [U15:B]
No model specified for U16:A. [U16:A]
No model specified for U17:A. [U17:A]
No model specified for U17:B. [U17:B]
No model specified for U18:A. [U18:A]
No model specified for U18:B. [U18:B]
No model specified for U19:A. [U19:A]
Simulation FAILED due to partition analysis error(s).

I know the errors means there is no simulation model for this devices

I want to know what device I should use as an 8-Input OR (or NOR) and 4-Input AND gates ?

Is it possible to change the device model ? or I should redesign my circuit with new devices ?


texts: 2nd order Low-Pass Output Impedance and Phase difference

texts:
I am trying to calculate the output filter impedance and the phase difference of the inverter that I am designing.
 However not sure how to construct a formula for both the output impedance and phase difference. I know that for series RLC network both parameters can be calculated as follows:

UPDATE
Current direction alternates, but for a single cycle say it flows into AC_L and out of AC_N with a voltage source connected between them. The output is considered between the two points. Therefore, I want to know the impedance of the total network were (R || C) in series with L. I can see how my formulated question is no good since i did not specify the termination points. Apologies


texts:
I am looking at sizing a motor for lifting a mass a set distance in a set time and have found multiple design notes that have allowed me to complete this task. For example https://www.maxonmotor.com/medias/sys_master/root/8815460712478/DC-EC-Key-Information-14-EN-42-50.pdf?attachment=true or http://www.machinedesign.com/motorsdrives/how-pick-motors-linear-motion

However, my main qualm lies in understanding the ability to dictate and obtain a trapezoidal profile. Taking the the second source as an example, for acceleration/deceleration the torque required is 0.3582 Nm and 0.3309 Nm  for constant velocity.

1) I understand the concept of the torque constant, but how do you control the current supply to obtain these constant torques for acceleration and constant velocity?
Could it be implemented by measuring the current to the motor, turning off the voltage supply when it hits this limit, and turn it back on when it falls below, until it reaches the target speed and then turning off this limiter?


texts:
I have some questions about this circuit (from the book 'Art of Electronics'):

How can this P-channel mosfet support high source voltage (150 V)? In the datasheet it's mentioned that \$V_{gs}\$ = +- 20V, so if the voltage in the source is 150V then the \$V_{gs}\$ will be less than - 20V.


texts: First mains-powered project - best practices?

texts:
I'm about to commence building a project that's basically a USB-controlled dimmer.  I think the main components will be:

Velleman K8064 voltage-controlled dimmer
Phidget 1018 usb interface board
Australian mains socket (into which I'll plug a lamp)
IEC mains socket (into which I'll plug a power supply lead)
a pretty plastic enclosure

I'm not so much concerned about the project working, but as this is my first project involving mains power I'd rather not build something that electrocutes me, or burns down my house.

Could someone with some experience in the field please recommend some best practices, and / or some online resources, suitable for project builders new to mains power?


texts: How to use HDL designs in hobby circuits and how to do transistor level tuning

texts:
Please excuse the noobness.

What is the process a lone (or few) individual can send an HDL design off to a fab (tools, file formats, potential fabs)? I have played around with FPGAs but I'm curious how can I integrate them onto hobby circuits or add them to a PCB design. It seems like they would be impossible to hand solder so there must be a service for this.

I have read a bit about super low level optimization such as tuning transistor sizes and arranging transistors by hand but I don't know the process one would take to do this? Is there a standard format of interchange that one could use to specify such things to a fab completely.

I have searched the googles already. There is either nothing answering my specific question or I just don't know the proper search terms.

EDIT: Somehow my question is too broad. New version -> What manufacturers/process could one use to take a design prototyped on an FPGA and turn it into a standalone chip?


texts: Configuring the rate of Timer interrupts for the STM32F4xx Discovery Board

texts:
I'm working on a project with the STM32F407 board and Keil, and as part of a larger project I'm working on I need to configure a timer interrupt. Eventually it will run at around 46 kHz, but for now I'm just trying to control the rate at which it interrupts.

In it's current state I have the timer and interrupt working so that when TIM3 finishes counting up it's period, it throws an interrupt which I have a handler written for. I can then blink an LED or do whatever I need to in this handler. My problem is that no matter how I seem to configure it I can't adjust the rate at which it interrupts. I've put a counter that increments every time the interrupt is thrown. I've used this to time it and found that it seems to run at a rate of about 245 kHz (+/- maybe 5 kHz).

I've used the excel spreadsheet that generates the system_stm32f4xx file to configure for a clock of 168 MHz. I configure the TIM3 clock using the following function:

void InitializeTimer() {
    TIM_TimeBaseInitTypeDef SetupTimer;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

    SetupTimer.TIM_Prescaler = 167-1;
    SetupTimer.TIM_Period = 1000-1;
    SetupTimer.TIM_CounterMode = TIM_CounterMode_Up;
    SetupTimer.TIM_ClockDivision = TIM_CKD_DIV1;

    TIM_TimeBaseInit(TIM3, &SetupTimer);
    TIM_Cmd(TIM3, ENABLE);
    TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);
}

I configure the interrupt with the following function:

void EnableTimerInterrupt()
{
    NVIC_InitTypeDef nvicStructure;
    nvicStructure.NVIC_IRQChannel = TIM3_IRQn;
    nvicStructure.NVIC_IRQChannelPreemptionPriority = 0;
    nvicStructure.NVIC_IRQChannelSubPriority = 1;
    nvicStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&nvicStructure);
}

Both are called from main in this order. Based on this post I found the above prescalar and period values to get an interrupt of 1 kHz. However this is not the case. In no particular order a list of things I've tried includes:

Numerous different combinations of prescalar/period values
Changing the the HSE_VALUE in stm32f4xx.h from 25 MHz to 8 MHz (everything I've seen says the external oscillator runs at 8 MHz, not 25; but the that's what the excel file configured it to
adding the following to my Timer initialization function:

uint16_t prescalar_val = (uint16_t) ((SystemCoreClock / 2) / 6000000) - 1; //6 MHz
...
TIM_PrescalerConfig(TIM3, prescalar_val, TIM_PSCReloadMode_Immediate);

Which is a code snippet I found that said it configures the timer to run at 6 MHz

I'm pretty much stumped at this point. I've read this document's section on general purpose timers (ch 18), and based on that and other examples I've found online I'm doing everything right. Maybe there's something I'm missing, which wouldn't be very surprising - I'm pretty new at this. In a worst case scenario I just use the interrupt as is, and use a counter to divide the frequency, but that seems like a pretty silly solution.

Any help anyone could give me would be greatly appreciated. If someone wants to look at any other file or function in particular I can post it.


texts: What is the correct method for Triac supply?

texts:
I need to know what is the correct power supply for fallowing light dimmer circuit that operate by 230V/50Hz AC supply.

It should be neutral(N) to MT1 or live(L) to MT1?
If can use both, what is the most suitable and what are the reasons for that?


texts: What parts could be labeled XT and be near a Clock of a microcontroller

texts:
An ice cube maker stopped working with the symptom that the temperature cycles are getting shorter and shorter.

I suspect that the microcontrollers clock is not working properly.

I desoldered a part near the clock and I want to replace it.

It is labeled '4.00 J'. I can not identify the part and google did not put out useful information for me.

The microcontroller is this one, page 19 shows its pins. The XT component center pin (pin 2) is connected to vss. XT pin 1 os connected to XIN/P1.0. XT pin 3 is connected to XOUT/P1.1.

Most confusing for me is that the XT component has a 'J' printed on it. What does that label mean and what could be my unknown XT component?


texts:
Is there any practical difference between a matched pair of transistors and dual transistors in one package? Realistically, the latter are also two transistors from the same die, so they should be quite identical.

For example, the Diodes Inc. DMMT3906W is advertised as a matched PNP pair, while the Nexperia PMBT3906YS is "only" a dual PNP. Regarding the other parameters they are very similar components.

So is there a real difference or is it that Diodes just does more meticulous tests and is therefore more confident in their specs?

For context, in my application i am looking for a close tracking of base-emitter voltage over temperature.


texts:
How many watts does a 12v 300 led - 5 meter strip light use roughly, is there a wattage per smd/led there 5050, I have a 5amp 12v = 60watts I think and was told that's more than enough, and I have a 1.5amp 12v = 18 watts I think. There was no watts per meter specified.
Rule of thumb sort of answer


texts: Would it be safe to exceed a battery's C rating for short bursts?

texts:
I'm currently building an autonomous drone as an experimental project, because my high school classes are getting quite boring.
I've already ordered all the parts, but upon further inspection of the 18650 cells I chose, it seems as though the C rating may be considerably lower than what my motors can pull.
The cells are Panasonic NCR18650B cells which are rated for 2C continuous discharge. I'm going to be running a 4S3P configuration of cells, so that would leave my total safe continuous discharge rate at around 20.4 A.
The problem with this is, the motors can pull up to 25 amperes EACH at 100% throttle. I went a bit overboard on the motors, but after looking at the specifications, it is completely possible for the drone to fly at around 60% throttle (5A per motor.)
Now my question is, would it be safe to exceed the battery's C rating, lets say to 3 or 4 C for short bursts (10 seconds?) What about 10C for a fraction of a second?
I'm not super experienced with electronics, seeing as this is my first "real" electronics project, any help would be appreciated.
TLDR: Can I exceed 2C rating of a battery for short bursts safely?
datasheet


texts: Why do we not use true sine waves in power inverters instead of PWM?

texts:
These days it seems all power inverters use variable PWM and an H-bridge to generate the signal which drives the output transformer. Why do we not use a pure sine wave oscillator  and amplifier instead?
It seems to me the technical complexities of PWM are much greater than a simple sine-wave. But I cannot find a single example of an inverter which uses a sine wave oscillator. Therefore, I'm assuming there are very good reasons for not using such a design. Can anyone explain what those reasons might be?


texts:
Is it possible to replicate a random pattern of trigger and charge times to an UJT firing circuit for an SCR configuration?

What I mean is that, UJTs usually have a periodic sequence to them. Charging and discharging of the capacitor connected between  its E and B1 terminals occurs in a periodic fashion. Now, say the power supply is about 5V and I assigned this the binary value 1 and the binary value 0 to 0V. Since charging and discharging happens in a regular periodic fashion say, 1001001001... Is there a way that a UJT firing circuit can be configured in order for the charging and discharging to occur in say an irregular un-smooth fashion like 0010110011110?

Here's a website that describes how a UJT firing scheme works: http://www.electronics-tutorials.ws/power/unijunction-transistor.html

As you can see, the $$V_{R2}$$ waveform is regular and periodic. What I'm asking is if it's possible to redesign this circuit:

so that it can produce an irregular waveform. Assuming that the high values of$$V_{R2}$$ and $$V_{ON}$$ are 1 and the low values $$V_{R2}=0$$ and $$V_{OFF}$$ are 0. Then can a circuit be designed to produce a firing scheme such as 0010110011110 that repeats itself instead of 1001001001 that repeats after every 100?? So that if you zoom the waveform out, then you can see that repeating pattern though it's not as smooth and nice as the regular 100100100 sequence.


texts:
I'm reading about integrating PV into legacy grids, and I saw the following scheme:

Left side is middle voltage grid, and right side is low voltage grid (400V AC). It is talking about communication between PVs about stabling the inductive power, but if both feed in with the same frequency and in-phase, what communication do they need to have? What could be the problems in such a configuration?

This image is taken from "Aufnahmefähigkeit von Niederspannungsverteilnetzen
für die Einspeisung aus Photovoltaikkleinanlagen" by Georg Kerber


texts: Can i implement a wireless connection between an embedded system and a mobile phone?

texts:
I'm trying out an automation system, and i was wondering if it is possible to communicate over, say WIFI between a mobile application and an embedded systems based arduino ethernet shield or microchip TCP/IP library for example.

I'm thinking if the embedded system can create a wireless network, to which the phone can connect to and use to communicate.

I'm not sure if this is possible.


texts: Is the following system time-invariant or time-varying?

texts:
I was wondering if the following system is time-invariant or time-varying
$$ y(t)=e^{-t}\int_{0}^{t}e^{\sigma}x(\sigma+1)d\sigma$$
I know that it's not causal, and I think it's time-varying because of that \$e^{-t}\$ before the integral that makes the input delay and the delay of the output not equal, I am not sure if I am right.

Thank you.


texts: Can I use 3v CR2032 to power multiple vibration motors?

texts:
I am planning to use a 3v Arduino pro mini with 2 coin cells (3v CR2032 each).

I also need to connect 6 flat vibration motors in series rated as follows:-
Rated Voltage: 3v,
Rated Current: 70mA

Can I use 2 coin cells (CR2032)?
Each Rated:-
Nominal Voltage: 3 Volts,
Nominal Capacity: 220 mAh,
Nominal Discharge Current: 0.2 mA

If not, please suggest how to proceed ahead, what power source should I use and how. I only have a limited housing/space so a small battery is prefarable.

Please help me its my first project.


texts: Finding maximum power of resistor in 2 voltage source circuit

texts: I am trying to find the maximum power on R_L in the following circuit. I believe I need to use Thevenin's theorem but am not comfortable with it. I believe I need to find the equivalence of the circuit of everything on the left, but am not sure how to deal with the 2 batteries.


texts: 4-bit shift register wont work (unknown state)

texts:
I must design a 4-bit shift register circuit. I am pretty sure that I need 4 D flip-flops sharing the same clock. right??

So I did that and here is the result:

As you the LED lights are neither completely off (0) nor completely on (1) rather they seem to be in this, uh, indifferent state? Anyway, the point is, it is not working no matter where i put the switch.

If I go to each ff and remove the preset/clear lines the circuit works! but I do not understand why that is an issue? Why doesn't it just work the way I drew it?


texts: What determines voltage levels in RS-232

texts: What determines the peak voltage levels for RS-232 lines? Is it determined by the software? The hardware? Something else?


texts: reading only 12-bits from SPI on MSP430F2122, is it possible?

texts:
I'm trying to read data from a RGB sensor (S9706) and I thought about using the SPI for the readings.

The problem is that the sensor wants a little pause of 3-4us after each 12-bits (the colors resolution is 12-bit) I read,
and the hardware SPI can read 7 or 8 bits at once.
So if I choose to read 7-bits each time, I will not be able to make the pause after 12-bits, and I might loose some data while reading 2 more bits than I should.

Is there a way to read exactly 12-bits (12 clock pulses only) with the SPI, or should I write a bit-bangging function to do what I want?

Thanks!

EDIT

Eventually, I choose to do it with bit banging, although I think it might be possible to use SPI with low a frequency of 200Khz.
With 200Khz every clock will be 10us, 50% dc = 5us, and it's more than the pause I need after every 12 bits.

what I don't sure is what will happen between bit 37 to 40, because the SPI will read 5 bytes (40 bits) and the sensor has data for 36 bits. It might start sending new data from the next 36 bits..


texts: Interpreting triangles in RC high pass filter circuit diagram

texts:
I came across the following image of a RC high-pass filter

There is also an initial analysis that says that there is an initial condition for the output voltage that says $$v_O(0^-) = 0$$  which apparently implies that the capacitor voltage satisfies $$v_C(0^-) = 1V$$
I am not sure how this implication is derived, because I do not understand the circuit diagram, more specifically what the triangles mean. I would like to use KVL but then would need a closed loop. From wikipedia and other sources I have looked at the example image of a RC high pass filter is

Are these two images equivalent and what does the triangles in the upper image mean?


texts: Do I need to protect buck converter when switching to alternate power source?

texts:
Noob question here; please pardon my ignorance.  I am trying to power some 12v devices, (e.g. Peltier cooling device and fan ~4A), optionally from one of two power sources:

12v DC In
DROK Waterproof DC Buck Converter Voltage Regulator 8-22V to 1-15V 5V 12V 3A Adjustable Output Power Supply Transformer

There are times when I want full power, and others where I believe 7v-9v would be more appropriate.  Since the buck converter would consume power even if not used, I'd prefer it was off unless selected.  I also want to try to control selection with one switch.  My desired solution is to use a DPDT On/Off/On switch as follows:

inputs are +/- 12v source
switch center: off (obviously)
switch up: +/- power goes directly to +/- load terminals (12v option)
switch down: +/- power goes to buck converter input (9v option), buck converter output goes directly to the same +/- load terminals

My concern reflects my lack of knowledge, that being whether 12v power (switch up) would cause damage since buck converter outputs would be connected to the same load terminals.  Thus, when switch is up:

Would current flow into the output of the buck converter and cause damage to buck converter or downstream due to some power build up (e.g. a capacitor)?
If I need to protect the buck converter, would a diode (e.g. Schottky) on the buck converter output (+) wire fix the problem?  If so, what spec should I be concerned with?


texts:
I have ATmega328P circuit that drains from 0.1 to max 150 mA. Most of the time it's asleep (0.1 mA - with other little components attached) and once a minute it wakes up and drains 80 mA && occasional user input can increase drain up to 150 mA. So drain isn't constant, but most of the time it is less than 1 mA.

I need my circuit run from 320 mAh LiPo batterry and also to be able to charge it while the device is being used. One problem is that there is no datasheet for my LiPo batterry (CELLEVIA BATTERIES L303040), so I don't know if it's possible to charge it in 1C rate...

If the charge current was 160 mA (0.5C), with AVR circuit's 150 mA drain the charging current equals 10 mA. But this is only temporary (miliseconds), not a constant drain. So I guess that battery charging process won't be affected.
Or I can set charge current up to 320 mA (1C), so with drain 150 mA there should be 170 mA left for the battery.

What do you think about charging no-datasheet battery in 1C?

I have MCP73831T-2ATI/OT charge IC and BU33TD3WG 3.3 V 200 mA regulator available.
Will this circuit work?

There is 220 mV dropout voltage on the regulator so it won't work with
VIN < 3.52 V?

I know there is a solution suing P-channel MOSFET to switch power sources, but I don't have any access to this type.
I hope the circuit above should work.

Thank you very much!


texts:
$$V_o = \frac{V_s \cdot R_2}{R_1 \cdot (1+R_2/R_L)+R_2}$$

I need to derive this equation given this circuit:

This is what I have so far.

$$I=\dfrac{V_s}{R_1+\dfrac{R_2 \cdot R_L}{R_2+R_L}}$$

$$V_{R_L} = I \cdot R_L$$

Where am I going wrong?


texts: How to calculate MOSFET temperature increase in PCB

texts:
I want to calculate MOSFET(DATASHEET) temperature increase for PCB.

MOSFET - FDD86250_F085-D

Totally 13 MOSFET's will be mounted in PCB. At the same time, maximum 8 MOSFET's will be used in PCB

1, Actual power dissipation for total MOSFET's?

2, Temperature increase in complete MOSFET(max. 8) in PCB?

3, Position of MOSFET's in PCB?

4, Will it require Heatsink?

PCB size is 90(L)*62(W) mm

From MOSFET Datasheet,

Maximum Power Dissipation 160W

Operating Junction Temperature Tj - 55 to 175 °C

Thermal Resistance, Junction to Case Rthj c 0.94°C/W

Thermal Resistance, Junction to Ambient Rthj a 40°C/W


texts: Synthesis error when using "-opt_mode area" in Xilinx XST

texts:
I am experiencing fatal errors when synthesising my design with Xilinx XST 14.7 and the -opt_mode option set to area. With -opt_mode set to speed it works fine and synthesis finishes successfully.

The error message I get is the following:

  FATAL_ERROR:Xst:xstmacronode.c:118:1.15 - Invalid In Port Name : D
  from my_port_name, index==-1  Process will terminate. For
  technical support on this issue, please open a WebCase with this
  project attached at http://www.xilinx.com/support.

(I replaced the real signal name with my_port_name for reasons of confidentiality.)

The design never caused problems before (-opt_mode had been set to speed until now). The error first appeared when switching to -opt_mode area.
I tried to change the port name given in the error message to something different, but the error still occurs, now complaining about the new port name.
On the Xilinx support forum/answer records are 2 posts with similar topic, but no solution is given (and the version of XST/ISE is a different one).
What (besides a bug in XST) could cause this error?


texts: On PIC MCU, a pin assigned an IO function the neighboring pin is also affected

texts:
I have been chasing  the 'read modify write' problem for two days. This is a problem that when you write to one pin a neighboring in is affected. It suddenly started happening - different chips - different computers - different breadboard. The only thing I can think of that is in common is the programmer and the weather. I never had this kind of problem with any other embedded systems, Arduino, raspberry pi, Motorola, etc...

Before I give up completely on (PICs), is this an issue anyone has heard of before? is there a solution?


texts: Digital potmeter in transimpedance amplifier feedback

texts:
I am considering using a digital potmeter with, e.g., I2C interface as the resistor in the feedback loop of my transimpedance amplifier. I am concerned about this. Will this add any additional noise compared to a normal resistor or somehow limit the transimpedance amplifier performance in any way?

EDIT:
Conversion range needed: 10nA - 10mA


texts: Charge LiPo battery with protection directly through dev board

texts:
I am just buying some LiPos (3.6V) and charging circuits for a project. The batteries come with overheating, over-voltage, over- and undercharging protection circuitry. In the reviews, someone mentions that you can use any source to charge it due to the protection. I googled it but it seems people make a difference between protection and charging circuitry, and I cannot find an example of someone using it without charger. I see why, but wonder if a protective circuit would work as a make-shift charging circuit, at least it won't explode, right?
In short, can I just hook the battery on the Vin on my D1 mini, supply the board from battery and charge the battery when hooking the board onto USB?


texts: Is my charge controller working like it's supposed to?

texts:
I have a Coleman 40w solar panel & charge controller to charge a 12v battery.  The battery is a group 24 deep cycle with 85Ah lead-acid and works fine.

My charge controller always shows "Charging" even after days of not using it.  The green "Charged" light never comes on.  In the darkness and after turning on several lights and using my water pump to get rid of surface charge, my battery reads anywhere from 12.7 to 13 volts.  But every afternoon when I come home, I check the voltage and it's between 14.6 to 14.8 coming from the charge controller (measured at the battery terminals) and still reads "Charging".

Is my charge controller malfunctioning?  I have no way to check amps because I blew the fuse in my multimeter.  Is this going to boil my battery?  The only thing that's always on is my carbon monoxide detector which uses hardly any power.


texts:
I need to generate an adjustable clock in hdl (verilog) on altera cyclone II fpga using signal probes (blocks that can change their output value through jtag - there is no need to recompile the code). I came up with a solution which uses a counter and a comparator, the output of the comparator being the new clock but this idea creates a very ugly clock (spike) and I was wondering if there is a better solution to this.

On some fpgas (stratix) it is possible to use a reconfigurable pll but this doesn't apply to cyclone II unfortunately.

Thanks for your help

edit: Input clock 24 Mhz. Output clock 1khz - 10Mhz, clock is used for transceiver and receiver blocks, which are simply sending bytes between each other.


texts:
sorry for my bad english
i have problems with rs  modbus , my project is about max 485 i have  master and 3 slaves when  i put master with one slave it's ok and there isn't any problems but when i put the master with 2 slave or more the rs modbus is disappear ""when i invert A&B in the second slave the led of rx flashed but there is no response from processor""
what is the problem in this??
 (first picture for master)
(second one for slave)

the processor is atmega 8


texts: Line Level to Mic Pad Working Randomly With Phones

texts:
I'm trying to build my own headphones to mic pad. I want to connect the input of the pad to a phone's headphones conector and the output of the pad to a second phone's mic connector. Both phones feature a TRRS 3.5mm audio jack (4 contacts, CTIA standard). Here's the circuit:

                     C1
    +Line level in --||----R1----+-- +Mic level output
                       +         |
                                 |
                      +----R2----+
                      |
    Ground (input)----+--------------- Ground (output)

I found the schematics in this page

I've measured the headphones output signal in a couple of phones. Each brand seems to have different amplitudes, almost nobody follows line level standard. I measured amplitudes ranging from 500mV to 1.8V peak to peak.

I've chosen R1=20K, R2 = 1K, so the output amplitude of my pad should be 1/21 the input (23mV to 85mV).

This pad works fine when plugged to any device that only has a mic input. But with phones it's a bit more complicated. Phones already have a built-in mic, and there is some mechanism in place to detect whether or not an external mic has been plugged to the audio jack (e.g. a handsfree). So with phones and tablets, this very same pad works only sometimes: when it works, the pad is detected as an external mic, and it displays the "headset+mic" icon in the status bar; when not working, the phone switches to the built-in mic, and the "headset with no mic" icon is displayed in the status bar (as if only a TRS connector were plugged in). It looks like a random issue, and I don't know why, because I used exactly the same phones and tablets for my tests. My pad is well soldered btw.

And now here comes the odd thing. If I add a 1V DC offset to the pad output then it works always. No random malfunction any more.

Could it be that the unbiased pad output signal (which is centered around 0V) is detected as "ground" by the phone and it switches to external mic? Or is it a bad choice of resistor values?

UPDATE: it could be the case that my voltage bias circuit is providing aditional impedance and that makes it work. I'll play with a potentiometer in R2 and see what happens.


texts:
I have everything in place to log my consumption of elektricity and water, but have no success to log my gas consumption.
My gas meter is an old mechanical meter with rotating numeric wheels.
There is no reflecting part on one of the wheels. Also there is no magnetic signal that is detectable. I tried already with an IR array sensor.
Now I've placed an IR sensor (diode) + IR led on one of the wheels, and amplified the output with a differential amplifier (with opamp). In the picture, you see the result. There is indeed a pattern. The challenge is now to 'translate' this in 1's and 0's (where 1 is for example the start of a pattern). I like to use the '1' as a signal for a hardware interrupt. Maybe getting the spikes significant higher?
All idea's to solve this, or get another solution are very welcome!
I informed for another gasmeter, but that is expensive...

Wannes

Rough schematic:


texts: Attaching temperature sensors to solar cells

texts:
For my project, I have to find the temperature coefficients of the solar module that I am using. Meaning that I need to calculate the change in voltage, current and power with respect to temperature of a solar module.

In order to do so, I need to attach a thermistor to the back side of a solar module and continuously record the temperature (using arduino). I am going to be using an epoxy  thermistor and thermal curing glue to attach it to the module.

Is there another way to do it? Any recommendations as to which thermistor to use (bare or epoxy based) and which glue or grease or paste or tape or another way in general?


texts:
Maybe it's a silly question, but I want to use a microcontroller with a CPLD.
My idea is for the microcontroller to reprogram the CPLD as many times as the user wants.
The problem is that I don't want to use a software provided by the manufacturer, I want to create my own software tool.
Is it a crazy idea?
It is something similar to this project:
HOW-TO: PROGRAMMABLE LOGIC DEVICES (CPLD)


texts: Why does output voltage increase when pwm input frequency to output enable increase?

texts:
I'm trying to pulse-width modulate an output from a 74HC585 shift register.

To achieve this, I plugged a PWM output from a teensy 3.1 microcontroler into the output enable input of the 74HC595. The A output of the 74HC595 is then connected to the ground via a 640 Ohm resistor. Voltage between VCC and ground is 3.3V.

Then I use the microcontroler to shift 0b00000001 to the 74HC595 and I start to PWM the output enable input at 50% duty cycle.

I expect to measure about 1.6V voltage between output A of the 74HC595 and ground. And indeed, if the PWM carrier frequency is slow (100 Hz), that's what I observe.

Problem is, when I try to increase the PWM carrier frequency, the voltage between A and ground increase. For example, I measure 2.7V for a 10 KHz frequency.
I measured the voltage between the teensy pwm output and ground, and it is as expected : 1.6 V.

So, I know ICs can't be fed arbitrary high frequencies, but I was under the impression that 10 KHz doesn't qualify as high frequency.

I seem to be unable to understand the problem, so here I am : can anyone explain me the reasons of this behavior ?


texts:
I was wondering if someone knows if it is unusually hard to do soldering on a flat headphones cable. I am sorry, I don't know how one is called, which is why I could not even find a replacement or any videos or how-tos. It's for Sony MDR-ZX600 headphones with a 3.5mm TRRS jack. The jack is slightly bent, and I have to use a M-F adapter and flex the cable to get them to work. I've never had to deal with a flat cable like that and don't want to completely break it by trying to solder a new jack to it.

Has anyone dealt with this type of cable and is it as easy to deal with as most low-end round audio cables? I was only able to fix no so fancy XLR mic connectors and inexpensive speaker systems with ripped out cables, etc. Thanks in advance.


texts: RS422 and RS485; full-duplex or half-duplex?

texts:
I have extensively used RS232 transceivers in many projects and have fairly good understanding of UART communication using RS232 transceivers. MAX232 and MAX3232.

Now I have to build my understanding about RS422 and RS485 transceivers. So far I could not build crisp understand of the two as to when is one better than other. One thing that is clear to me is that RS422 use uni-directional transceivers for RX and TX differential lines while RS485 uses tri-state-able bi-directional transceivers.

For RS232 I know its always full-duplex but for RS422 and RS485 both of them are at some places explained a full-duplex while at other places as half-duplex buses.

What can we say with certainty about it for these busus?


texts:
I guess I know the answers already, but the "X" in this table really confuses me:

Source: VN5E010AH datasheet.
Questions 1: Is it usual for "X" to be used for "yes" - to me, it might as well mean "no".
If we take all three pins individually:

Regarding OUT: I don't intend to let the output floating, so I'll ignore that one.
Regardin IN: this pin will be driven from a microcontroller, which means that the pin would be floating until the micro has completed booting.

Question 2: can I interpret "X" as meaning that I don't need a pulldown resistor to keep the pin down until the micro has booted?

Regarding CS_DIS, ST has confirmed the meaning of "X" in the chip user manual, available from  the VN5E010AH resource webpage. From page 8:

If current sense disable function is not required, CS_DIS pin should be left open or connected to ground through a resistor (~10 kΩ). Direct connection to ground is not safe (ISO pulses clamped through CS_DIS pin can damage the device).

Am I just just overthinking it?
Thanks.


texts: Are there combo gates XOR followed by AND? (4-bit identity comparator)

texts:
Is there no 4 bit identity comparator in TTL or CMOS? It could fit into a DIP-12 package as all it would have is 4 XOR gates for selectable invesion and 1 4-way AND gate.

OUT := (A1 xor B1) and (A2 xor B2) and (A3 xor B3) and (A4 xor B4)

Just 11 pins with Vcc and GND. Could even have both OUT and (not OUT) for easy (not CS) or (nor LOAD) application.

The comparators I know, 74LS85 being the smallest, comes in a DIP-16 package and has A < B and A > B outputs which I don't need.

I am building a TTL or CMOS mini-computer from scratch. I have a bus and various modules can be addressed on that bus using 3 or 4 module address lines. Now each module listens to these 3 or 4 lines with a comparator to find out if their address is called. I have seen this principle on ISA bus cards where they use 74LS688, but that's for 8 bit.

I'm just trying to save space. I went down the entire 7400 list and 4000 list, so I know it's not there.


texts: If we have open loop gain of 2dB or 3dB what happens if we use this in closed loop (except the gain reduction)..i mean how does gain affect on the output of feedback amplifier.


texts:
I was looking for some reference and I found this resistor symbol:

All the resistors in the schematic (several sheets) have the same symbol, so I concluded that it means nothing, but I'm not sure. What does the dot mean?


texts: Maximum power transferred by the source to the load

texts:
I am in the middle of doing this question however have reached an issue.
To find maximum power transfer I understand the equation is P=I^2RL
However the answer I get is 2.4w the answer should be 50W  The Answer i get for R2 is 15 ohms. Any help would be appreciated


texts: Meaning of (*(__IO uint16_t*)PAGE0_BASE_ADDRESS) variable declaration

texts:
There is a variable declaration:

uint16_t status = (*(__IO uint16_t*)PAGE0_BASE_ADDRESS);

__IO is the precompiler directive that becomes the keyword volatile. PAGE0_BASE_ADDRESS is the hex address, say 0x08000000;

I can't get my head around what this statement actually does. Anyone help please?


texts: Nixie tube equivalent circuit model and transients

texts:
I am about to design a Nixie clock and at the moment, I am doing some research. However my doubt is how to treat Nixie tube. For example, a simple circuit for switching Nixie on and off with: anode resistor, nixie and common emmiter in cathode.
If transistor is off, what is the voltage in collector? I suppose there should be:
Supply voltage - Ra*InverseCollectorCurrent - Vnixie(InverseCollectorCurrent)

In this case what could be the maximum collector voltage in such a circuit and how to dimension my transistor?


texts:
Simply put I have the following:

  Arduino Uno

With a

  SainSmart L293D Motor Drive Shield

Plugged into it

Now the last part needed is to hook up my

  bluetooth module

so I can control the Motor Drive shield.

Here's the problem though, the Motor shield uses

EVERY SINGLE DIGITAL PIN ON THE ARDUINO!

I have

  5 analog pins

open though.

Am I able to turn analog pins into TX and RX for the bluetooth??


texts: Memory-mapped IO vs Port-mapped IO in microcontrollers

texts:
I've been reading about external peripheral mapping to microcontrollers.

I understand that memory-mapped IO means that the same address space in the microcontroller can be used for internal memory and also to map external peripherals. Therefore the same instructions we normally use can be used to communicate with external devices.

Port-mapped IO means that there is a certain address space especially used for mapping external peripherals. Sometimes specific instructions need to be used to accesss the peripherals via this address space.

Obviously we can see the advantages of memory-mapped IO here. However, I read from the link below that

  "The disadvantage of memory-mapped IO method is that the entire address bus must be fully decoded for every device. For example, a machine with a 32-bit address bus would require logic gates to resolve the state of all 32 address lines to properly decode the specific address of any device. This increases the cost of adding hardware to the machine."

Can someone please explain this as I can't understand this. Why does the microcontroller need to decode the 32-bit address bus like this?

https://www.bogotobogo.com/Embedded/memory_mapped_io_vs_port_mapped_isolated_io.php


texts: Extremely simple OpAmp comparator circuit not working

texts:
I decided to make my own ADC and I tried to use the following circuit to do it.

According to my knowledge, when a 5V signal is applied to the mosfet gate and then pulled to ground, the capacitor should discharge and when it discharged to 5V, It should pull the output of OpAmp to V2'S VCC.

Then I can use the capacitor discharge formula to calculate the voltage. But when I tried it, it is not working. The OpAmp is outputting 0V.

simulate this circuit – Schematic created using CircuitLab

I did some troubleshooting and found out the OpAmp wasn't working probably. I separated it from the circuit and tried this circuit:

simulate this circuit

According to my knowledge, the opamp should output 3.7V or near it because it is not a rail-rail opamp, but instead, it is outputting 0V. I have tried using an lm393 instead of lm358, but it is still not working.

So is there anything wrong with my circuit?

Edit:
I have the opamp successfully output a voltage but the voltage is extremely low (0.08 v) and it is unusable, I have fixed my circuit to something like this:

simulate this circuit

This circuit works but the opamp outputs very low voltages, so is my circuit right? Or did I destroy it again?


texts:
There are little to none information about Peltier in the internet, especially in team of powering it, so here I try to ask few question about it.

Here is the particular one that I am referring to:

12706
Internal Resistance 2.1-2.4 ohm
Imax 4-4.6
v 12v  Vmax 15.2v
QCmax 50-60W

Q1, Clearly, I should power it using 12v-15.2v power supply, but what about powering it with a higher voltage? Being dumb and all, I did powered it with a 19v DC and it works fine, so what is that Vmax all about?

Q2, What is the closest electronic component can a Peltier device model to? If I know that, then I know how to properly power it, but to me, it's like an unknown dark box.

Q3, PWM or NOT PWM? and why? Some people have claimed that it's not efficient to power it using PWM, but I think they are confused PWM with AC. Powering it using AC is like changing the Heat side to cold side many times in a second, which will only produce heat in the process.

Q4, A LED is a current device. what about this? Is it current driven or voltage driven? How to calculate the current? My test: powering it with 19v, got 5.1A and 12.8v got 3.5A;

Q5, It's not a resistor, nor a diode, maybe both? When measuring it with a meter, I got 12ohm with reverse; and 0 ohm with red to red and black to black.


texts: Can I reduce voltage from 3.3V to 1.8V using a 1.5V battery?

texts:
I am interfacing to an EEPROM that works via SPI at 1.8V; unfortunately I do not have a 1.8V power source around and being this a weekend project, I wanted to complete it without going to the shop.

I asked a skilled friend an advice and he suggested I could put a 1.5V AA battery in the circuit to get 1.8V.

Is this a sound configuration? I am a newbie but by gut feelings I feel there is something wrong, in particular regarding current intensity.

Edit 1: I know this is a bad idea, but I am asking here to know why. I could not find a similar question so I believe it will be useful to have here as a reminder of why not to pursue bad ideas like these. I will accept the answer with the explanation of why not to do this. I know it should be done with a voltage regulator, I am asking if it is possible without it, so answer can be yes/no with an explanation. I am also curious to read about anybody that thinks it is possible.

Edit 2: for those interested in the power draw, the EEPROM is a Winbond W25Q64FW and I will use it through a TXB0108 level shifter (side B). For the records, I did not ever try this circuit (in particular after the answers/comments I received) but I am nonetheless very interested in reading what is possible or not.


texts: Effects of ground plane size on antenna gain

texts:
I have looked online a bit and it seems to me that the general belief is that the larger the ground plane (up to a certain extent), the better.

I am trying to design a patch antenna, so I ran several full-wave simulations and increased the ground plane size each iteration, extracting the gain. I observed that as I increase the ground plane size, the gain increases at first and then decreases. Additionally, I've read a paper which claimed that the gain of the antenna changes periodically with the ground plane size.

Does anyone with experience relating ground plane size to antenna gain know of any useful resources?


texts:
This is what I have:

Atmega 8 wired for programming, confirmed working, programmer is my power supply.
2 leds connected via 470Ohm pull up reisistors to ports PORTB0, PORTB1 and to GROUND, working.
Pushbutton wired directly from VCC to PORT7D. My problem is that pressing button doesn't do anything. I have measured voltage levels at PORT7D and it is 4.96V when I press the button, otherwise it is zero.
Please find the program below and help me:

#define F_CPU 1000000UL

#include <avr/io.h>
#include <util/delay.h>

int
main (void)
{
    DDRB = 0xFF;
    DDRD = 0x00;

    while(1)
    {

        if( (PORTD & (1<<PORTD7)) == 1){
        PORTB =   (1 <<PORTB1);
        _delay_ms(200);
        PORTB = (1 << PORTB0) ;
        _delay_ms(200);
        }else{ PORTB=0xff;}
    }
}


texts: How does flicker noise cause phase and amplitude noise in an oscillator?

texts:
It seems to me like the flicker noise is phase modulated with the output sinusoid in an oscillator, but why is this the case?
I'm guessing that the amplitude noise is a result of the flicker noise also being summed with the output.


texts:
What I'm essentially trying to do is to add an amplifier to a simple passive radio receiver:

simulate this circuit – Schematic created using CircuitLab

XFMR2 consists of two inductors 0.4 uH and 730 uH. C3 varies between 35 and 235 pF (or something like this). Numbers and the whole left part is taken from here.

The idea is to demodulate negative part of a signal via D1, R1, C5 and pass it to an inverting amplifier based on OA1.

If this circuit is going to work: I'm interested in receiving medium frequencies. It is said they're quite tough to receive in a city due to industrial and home EM noise, especially during days. Am I going to need something more sophisticated instead of this circuit? (not going into antenna discussion here)

Also, why germanium diode OA47? Can I replace it with a Schottky diode?


texts: Why are IMU sensors calibrated in the ways that they are?

texts:
I'm using a BNO055 IMU for a project, and I'm learning to calibrate each sensor separately.

The gyroscope is calibrated by standing the device still in any position
The magnetometer is calibrated with sufficient normal movement of the device
The accelerometer is calibrated by placing the device in 6 standing positions

My question is why is each sensor calibrated in this way? I'm looking for an explanation of the science behind the sensors which determines these methods of calibration.
I've looked around the internet for an explanation but I can just find loads of tutorials on HOW to do it (as explained above), and not WHY its done in this way.
Link to the calibration procedure: https://learn.adafruit.com/adafruit-bno055-absolute-orientation-sensor/device-calibration#generating-calibration-data-2974405-5


texts: Effects of unearthed PSU and shielding on audio 50Hz hum

texts:
I am trying to get a good understanding on sources of 50 Hz “ground hum” interference in audio equipment and good practices for shielding and grounding  by making hum on purpose and taking steps to remove it.

I have been doing some experiments using a EMU 0404 external soundcard with 1 Mohm ¼” jack unbalanced line inputs. I am using it as a pre-amp/ headphone amplifier (not attached to a computer).

Here are my observations:

The EMU has an unearthed 5V dc ”wall wart” power supply. I noticed that there is a stable 100V ac (50Hz) and 0.2V dc potential difference between the 0V connection and earth. However, if I touch 0V and earth at the same time, I do not receive an electric shock. Why is there this large (presumably high impedance) common mode voltage? Why is it stable, if it is a “floating” power supply?
If I connect an unterminated 2 meter unbalanced ¼” jack cable to one of the inputs, I can hear lots of 50 Hz hum on the output. This is not surprising as the cable is acting as an antenna and the 0404 has high input impedance. However, when I connect the sleeve part of the jack to earth, most of the hum disappears. I can still increase the hum significantly by touching the tip of the jack with my finger.
If I remove the earth connection and insert the jack into a shielded but unearthed box, I can no longer detect the hum with my ears.

Can someone explain these observations, in particular the effect of the large common mode potential difference to earth on 50Hz hum?

My thoughts:

So I was surprised about the behaviour of the power supply and also that it would be used for audio equipment. Presumably the common mode voltage is stable because neutral is attached to earth in the uk. Could someone point me to a schematic of a switched mode power supply which behaves like this?

What I conclude from 2. Is that most of the hum is caused by the large common mode ac voltage of the sleeve/shield (which is connected to signal ground), which I find surprising. Surely the tip connection also has this common mode voltage at the input stage of the soundcard, so overall it should not make any difference?

When I touch the tip, I am turning the cable into a better dipole antenna, so this increased hum does not surprise me.

Observation 3. tells me that when everything is fully shielded, the common mode voltage no longer seems to matter.


texts: Deriving that Vin is way larger than nVt from Shockley equation

texts:
I am trying to show that from the Shockley equation Vin >> nVt.
Given a simple diode circuit like this

So far, I have equated the current through the resistor \$I = \frac {V_{in} - V_{D1}} {R_1}\$ to the Shockley equation \$I_{D1} = I_s(e^\frac {V_{D1}}{nV_t} -1)\$.
Thus
\$\frac {V_{in} - V_{D1}} {R_1} = I_s(e^\frac {V_{D1}}{nV_t} -1)\$
\$V_{in} - V_{D1}  = I_s R_1 (e^\frac {V_{D1}}{nV_t} -1)\$
Expanding right-hand-side:
\$V_{in} - V_{D1}  = I_s R_1 e^\frac {V_{D1}}{nV_t} - I_s R_1 \$
Assuming that \$I_s\$ is small \$I_s R_1\$ can be ignored, giving
\$V_{in} - V_{D1} \approx I_s R_1 e^\frac {V_{D1}}{nV_t} \$
Taking logs on both sides
\$ln(V_{in} - V_{D1}) \approx ln(I_s R_1 e^\frac {V_{D1}}{nV_t}) \$
\$ln(V_{in} - V_{D1}) \approx ln(I_s R_1) + \frac {V_{D1}}{nV_t} \$
From this I would like to interpret the equation such that I can show that when \$V_{in}\$ is positive, \$V_{in} >> nV_t\$, for the diode to be conducting current.
I know that \$n = [1,2]\$ and that \$V_t = \frac{kT}{q}\$ which is around 25mV for room temperature.  I know that the diode will start conducting at around \$0.6V = 600mV.\$
\$600mV >> 2 \times 25mv = 50mv\$
So these values all show that what I am trying to show is correct.
However, can this be extracted from the equation derived alone, without knowing any of the values?


texts:
Why do we use "shunt resistors" and is there a difference between a standard resistor and a shunt? Or is this context based, e.g., as in pull-up or pull-down resistor?

Addition: What is meant by shunt? I'm sort of missing the fundamental concept as well.


texts: Reading an Old Philips Radio Manual with SCR rows

texts:
I've been looking at the manual for the Philips L4X26T radio and I have noticed that for each of the diagrams, there is a rather peculiar table with three rows of numbers labelled "S", "C" & "R" (please see the pictures below). Would someone know how you're supposed to read these? I would hazard a guess that they're there to show component values since the three letters correspond to inductance, capacitance and resistance respectively. (For some reason, whoever wrote this manual has decided to use "S" for inductance as opposed to the usual "L". If anyone knows the reason behind this, please let me know.)
On the 2nd page (the 1st picture here), there seems to also be another table with the labels "SK1", "SK2", "SK3", ... all the way up to "SK7". If anyone know what this table represents, please let me know.
Thanks.


texts: Will 8 bit addition in 8085 gives 16 bit result?

texts: If two 8 bit numbers are added in 8085 microprocessor, will it give 16 bit result, if so where it will be stored, because Accumulator can store only 8 bit.


texts: Why current flows along a transmission line?

texts:
Say I don't have a ideal transmission line i.e resistance/length!=0.
Also E-Field exists between the two conductor lines. How then current flows through the line? There is no E-Field along the line right?


texts: Help wiring relay to LED driver - L/N on driver to L/O on relay?

texts:
I have a Shelly Dimmer 2 wifi-controlled relay, and I'm a bit confused as to wiring it to my LED module. The front of the relay looks like this:

This is the LED lamp I am trying to connect. At one end is a normal 2-prong 240V mains plug (i.e. AU plug, no earth), it goes to a LED driver, then to the LED module itself:

Closeup of the LED driver

There is a "L" and a "N' on the left input side.
I'm just trying to understand the correct way to wire it up to the relay.
Should I connect "L" on the driver to "L" on the relay? And then "N" on the driver to "O" on the relay?
Or is there another way to do this?
I don't need a physical switch in my case, I just need to use wifi to control the relay to control the LED.
(Shelly also talks about using a https://shop.shelly.cloud/bypass-wifi-smart-home-automation if you don't have a neutral, and your load is < 10W. I assume the LED draws very little at idle, so that my be needed here).


texts: Trying to differentiate between two simple clock divider circuits - VHDL

texts:
I'm very new to VHDL and I'm trying to design a simple clock divider process, but I'm running into a strange disparity between two forms of a process that I can't tell apart logically. I'd really appreciate help with this! Sorry if I don't include enough context, I don't know yet what would be helpful for this sort of thing.

Form 1:

div_main : process(clk_in) is
variable count : integer := 0;
begin
    if (rising_edge(clk_in) and sw_in(3) = '1') then
        count := count + 1;
        if (count > div) then
            count := 0;
            tmpclk <= not tmpclk;
        end if;
    end if;
end process div_main;

Form 2:

div_main : process(clk_in) is
variable count : integer := 0;
begin
    if (rising_edge(clk_in) and sw_in(3) = '1') then
        count := count + 1;
    end if;
    if (count > div) then
        count := 0;
        tmpclk <= not tmpclk;
    end if;
end process div_main;

(The sw input is a form of clk enable)
(The clk_in is a 125MHZ pin output on the FPGA)

The first form works perfectly, but I'm having a ton of issues with the second. It's tmpclk output is nearly random. The only difference I can see is whether the conditional reset of count is evaluated on only rising edges or on both rising and falling edges, which I wouldn't think matters. I would really appreciate if someone could explain why they behave so differently!


texts: Alternating ON and OFF with logic gates in a simulator

texts:
My intent is to make sure that when the top mosfet is on the bottom mosfet is off and vice versa. I'm really not sure that this accomplishes the goal. Is there some better way than this? I'm using two current sources that are configured to one second intervals. My sim doesn't look quite right when I turn it on both 1V batteries are pumping current through the mosfets.

I tried the PWM it was a little too complex for me right now but I did come up with something I though maybe works too:

So this must be what the PWM diagram is kind of saying:

Thank you


texts:
Possible Duplicate:
  Why wiggle nearby tracks on a PCB?

I was looking at a Raspberry Pi that a friend got today and noticed some weird traces on the board.  I'm wondering why they were designed this way.  Here is the best picture I could find of them.

See a larger image.

There are a few sawtooth like traces that can be seen just above the HDMI and coming out from the IC.