texts: How to use USB 5V output for 3.3V webcam module

texts:
I want to use an old webcam module from a notebook which needs 3.3V. Therefore I want to solder it to a USB cable and use it at an USB port on my computer.
For now I use the 3.3V source from a raspberry, which works fine, but of course that's not very convenient. Most tutorials on the web on how to reuse an old webcam don't use a voltage regulator at all and it seems to work well for them for some reason. But I don't want to damage my computer, so I want to do it properly.
These are all the methods I found other people using to use the USB 5V for their 3.3V webcam:

Element
Source

2 x 1N1004 Diodes
instructables @AikonM

LM1117
instructables @misterxp

IN4001 Diode
instructables @danjunk-DIY

LE33
instructables @DiegoF42

LM1117T & 2 x 10uf tantalum capacitors
thingsconnected.io

Without the context of using a webcam I also found people using the AMS1117-3.3 see this users answer which seems to me the "safest" method so far to me.
Somewhere I also read a bout using buck converter for that.
Finally I read in this post that I probably should use a LDO switching regulator.
Now I am very confused and really don't know what to use. On the one side I definitely want to be on the safe side to not destroy my computer (and maybe the webcam itself ;) ) and on the other side I don't want to pay more for the converter than the webcam is worth.
From what I understood simply using diodes is not safe, because both the voltage and the current are not guaranteed to be constant, since the USB specification allows a voltage between 4.3-5V. With that on my mind LM1117 or AMS1117 seem to be the better choice, but also I couldn't figure out what the difference in these two is.
Can someone explain what and also why to use it for this use case?

Sources:

Connecting old webcam via USB
Reusing Webcam and Monitor from old laptop
https://www.youtube.com/watch?v=8dQfgDdJSmk
https://www.youtube.com/watch?v=g8XbDJLKKys
https://hackaday.io/project/110436-laptop-webcam-reuse-made-simple
https://www.instructables.com/Reuse-old-laptop-webcam/
https://www.instructables.com/Laptoprecycling-Webcam/
https://www.raspberrypi.org/forums/viewtopic.php?t=140849
https://buger.dread.cz/how-to-reuse-webcam-module-from-dead-notebook.html
https://www.thingsconnected.io/complete-guide-reuse-laptop-webcam/


texts: VESA CVT Standard - How to calculate video timings?

texts:
Most video resolutions like VGA (640x480), UXGA (1600x1200) or HD720 (1280x720) are defined by VESAs Coordinated Video Timing (CVT) standard. (It can be freely downloaded from VESA.org).

The download results in an Excel sheet, where one can enter the display resolution and several properties like reduced blanking. After that, the Excel sheets prints out the results like Pixel Clock, H-Front-Porch, H-Back-Porch or VSync polarity.

I would like to get the equations, so I can calculate all VESA timings in VHDL for one of our universal VGA timing modules.

I also found a Display Monitor Timing (DMT) document that lists all timings, but unfortunately no equations.

Alternative Solution:
How can I enter all known video resolutions into the Excel sheet and export the results into a file. I don't want to enter them manually.

Appendix:

Known display resolutions. Source: wikimedia.org.


texts:
This is the TO-252 package.

It's got a tab, and two leads. There is, however,  a "stub" of a lead, usually connected to the tab. What function does this serve? Is it a vestigial pin that mutated and was kept by selection bias?

I am aware of a few other questions concerning this; however, none of them seem to address why exactly this is here.


texts: Two slaves on the same I2C bus, both response to address check, one working properly but the other is not

texts:
Ok, I will try to keep it as short as possible.
I have a GY-86 breakout board, the schematic is added below. As seen, MPU6050 and BMP180 are connected on the same I2C bus.

I do also have an Arduino. So, master is Arduino and the slaves are MPU6050 and BMP180.
I have used a premade I2C scan sketch with my Arduino, and the output is:
13:50:00.731 -> Scanning...
13:50:00.731 -> I2C device found at address 0x68  !
13:50:00.764 -> I2C device found at address 0x77  !
13:50:00.797 -> done

This is fine, since 0x68 is MPU6050 and 0x77 is BMP180. So, both slaves respond to address check. However, while MPU6050 is fully functional, i.e I can get data from it, BMP180 is not responding. I have used several premade "get BMP180 data Arduino code" from the internet, and none of them worked.
I also have an STM32 MCU, when I use it as master insted of Arduino, same story happens. Despite using the same I2C read/write functions, MPU6050 readings/writings are totally fine, but I cannot write to or read from BMP180. By debugging, I found that AF(acknowledge failure) flag is set when the MCU stucks while trying to write/read BMP180.
I also examined datasheets of both sensors several times, they seem to have the same I2C read/write pattern.
In short, somehow, BMP180 is found on I2C line by the I2C scanner, but data read/write cannot be done. What could be the reason for that? I could assume I somehow dameged BMP180, but it replies to its address. So, I could not understand what is going on. Any idea would be appreciated.


texts: Using 12V DC to create symmetric power source

texts:
I want to power a symmetric amp op with a raw and cheap 12V wall power source.

Can I use a schema like this to create a symmetric output ?
Or it will fail ?

simulate this circuit – Schematic created using CircuitLab

ps: I know I can use non symmetric amp ops, but I want to use symetric ones.


texts:
I would like to disconnect the current in the system with a battery (using N-MOSFET in a back to back configuration).
I would like the circuit to be on the low side and without a driver.
At this point, the circuit works only with a resistor.
When I add a power supply and the current flows in the other direction, the transistors are turned on all the time. I can't turn off the current flow.
Can such a system be implemented without a driver?


texts:
So I'm wondering if it's possible to detect a current passing through a specific cable inside a bunch, without being able to touch the cable at all... In other words :
Is it possible to detect the current in a wire surrounded by others, without touching it or moving any of the others out of the way, in any way at all?

I know the exact location of each of the wires, as well as the current that may or may not be passing through them, if that's any help


texts: Does a signal need to be in a clocked process to be registered (VHDL)?

texts:
I understand that it is best practice to register the outputs of all modules; so, I want to do that. However, I'm unsure what exactly it means to register an output signal.

I.e. Do I have to include the signal in a clocked process to ensure that it is registered? Or can I just use a concurrent statement?

It could be one of two ways:

entity mgmt_regs is
  port map
  (
    -- Internal host bus interface
    clk             : in std_logic,
    in_signal       : in std_logic,
    out_signal      : out std_logic
  );
end mgmt_regs;

architecture RTL of mgmt_regs is
signal sIn_signal    : std_logic;
signal sOut_signal   : std_logic;

begin

sIn_signal <= in_signal;

-------------------- THIS ONE?? -------------
out_signal <= sOut_signal;-------------------

process(clk)
begin
   if (rising_edge(clk)) then
       --do other stuff

       ------------------------- OR THIS ONE?? -----------
       out_signal <= sOut_signal; ------------------------
   end if;
end process;

end architecture RTL;

Also, I was wondering about cases when I have a top entity. If my subcomponents have their signals which are going to connect to the output part of my top entity and inside those lower entities their signal is registered, do I still have to register the output signal in the top sheet or can I just connect it to the output port?


texts:
I am trying to use a IRF7832 MOSFET {datasheet here} to control a short LED strip.

I have connected the LED strip between 12 V and drain and 0V to gate and source. The LED strip has 6 strings of 3 LEDs. As I understand pin 5-8 is drain, pin 1-3 is source and pin 4 is gate so I have pin 1-4 to 0V and 5-8 to the LEDs.

I expect this to turn off the LEDs but they are turned on very dim and I measure about 4.5 V between drain and source.

If I connect gate to 5V the LEDs turn on and I measure 2.5 mV across drain and source.

I have tried 2 different IRF7832's.

What am I doing wrong?


texts: Cheap options for high precision distance measurement?

texts:
I built a rather cheap(~€100) 3 axis CNC router for my workshop for cutting wood and aluminium in all sorts of fancy ways. It works great for most stuff but for things that require high precision, its always a little off.

For example, if I make it do 2 identical cuts, one right after another, the difference in any axis can be up to 1mm. Not too bad for wood, considering the total work area is 800x800x400mm and the size of things I make but kind of a problem for aluminium pieces that have to fit together.

It can be worse if significant amount of time/work is between the 2 cuts. I've had identical cuts made a few days apart for replacement parts differ by up to ~2.5mm on large pieces.

Now I figured I could get better rails, better bearings, engines, whatever to try and make it more consistent but I think the biggest gains could be had by having the ability to calibrate and check it in software.

TLDR: So what do people use for measuring distances of up to 1000mm with lets say 0.1mm precision?

I looked around chinese estores but all I found was laser sensors for large distances, like 100m with precision +- 0.2m and ultrasonic proximity sensors for shorter distances but pretty terrible precision.

They were pretty cheap though (<€10) which gives me hope. I also have the advantage of having complete physical control over both the points that I want to measure the distance between instead of just one.


texts: What is the recommended way for starting an ac induction motor with a VFD?

texts:
I am designing a control strategy for an AC(induction) 3-phase motor fan in an HVAC air handling unit for pressure control inside the ductwork.

The plan is to use a PID algorithm for the pressure control, by varying the fan speed, however I am quite confused if it'll work on start-up.

If the (Setpoint-Measured pressure) is high enough on start-up, which should always be, the output fan speed will be at 100% at start. This means that the system will start the motor with a 100% motor speed(high frequency). I was wondering if starting the motor with a high frequency AC would provide enough torque in order for the motor to start moving.

So my question is if the PID algorithm is sufficient or do I need to provide a slow acceleration at start-up(starting from 50Hz) and then switching to PID when the fan is accelerated enough.


texts: Shortest time required UART- UART transfer of 32 Byte block

texts:
I need to transfer 32 Byte block UART to UART
8 clock cycles per bit
1 start bit
Struct 8-E-2 8bits 1 UART char, Even Parity, 2 stop bits/ char

1 + 8 + Even parity + 2 stop bits = 11

efficiency = 8/11 (not sure)

Can any one help me the calculate the shortest time required to transfer?

Assume Micro Controller with 16MHz clock needs to transfer 32 Bytes of data


texts: Power and Energy Computations in the Frequency Domain

texts:
How do you calculate the power and energy of a signal given only the frequency domain form of the signal function? For the purposes of this question, please do not assume that it is possible to find a closed form representation of the inverse fourier transform time domain function. Or, in other words, assuming you cannot look at the time domain at all, how can you derive power and energy from the frequency domain representation of a function?
To add some clarification:
Rayleigh's Property:
$$\int_{-\infty}^{\infty}|x(t)|^2dt = \int_{-\infty}^{\infty}|X(f)|^2df$$
Definitions of Power and Energy:
$$E_x = \lim_{T\to\infty}\int_{-T}^{T}|x(t)|^2dt$$
$$P_x = \lim_{T\to\infty}\frac{1}{2T}\int_{-T}^{T}|x(t)|^2dt$$
Since the limit approximates Rayleigh's property, it seems it should be possible to find Energy and maybe power even if you cannot access the time domain function.


texts: How to solve Keil compiler 'Error: L6218E: Undefined symbol' on STM32

texts:
I am trying to run a simple tutorial (external interrupt example) on my NUCLEO-F746ZG board. I use STM32CubeMx software version 5.2.0 and Keil software version 5.28.0.0 as compiler. I get the following error:

EXTI_callback\EXTI_callback.axf: Error: L6218E: Undefined symbol ex0 (referred from stm32f7xx_it.o).
Not enough information to list image symbols.
Not enough information to list load addresses in the image map.
Finished: 2 information, 0 warning and 1 error messages.
Target not created.

where ex0 is a variable that is defined in main.c as

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */

char ext0;

/* USER CODE END PV */

and it is used as the external variable inside the stm32f7xx_it.c as follows :

/* External variables --------------------------------------------------------*/

/* USER CODE BEGIN EV */

extern char ex0;

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {
    if ( GPIO_Pin == GPIO_PIN_13 ) {
        ex0 = 1;
    }
}

/* USER CODE END EV */

by using the HAL_GPIO_EXTI_Callback function I want to assign the value of 1 to the ex0 variable, whenever the blue push button (GPIO_PIN_13) is pressed on the NUCLEO-F746ZG board.

It seems the code can not find the reference to ex0 variable, while it is defined in the main.c file. I don't understand what is cause of this problem. Should I add some .h / .c files to the my project? In addition, many users have also complained about the "Error: L6218E: Undefined symbol VAR_NAME" when they have tried to compile their code with Keil Software. I have read some of them, but I didn't find the main reason behind this error. I appreciate those of you who can share their experience on how to solve this error.


texts: Common mode choke vs individual inductors for offline flyback smps

texts:
I am working on Viper22a based offline switcher and I was going through similar app notes by ON semi and ST. I found two different implementations of noise filtering on incoming mains.

This one uses individual inductors (each of value 1 mH):

And this one uses a common mode choke (2.2 mH):

Is there any benefits of using a common mode choke over inductors?


texts: Is it possible to use a PIR detector to switch something on and keep it on without a microprocessor?

texts:
When a PIR detector switches something on e.g. a 12V light, I know I could use a microprocessor to keep it on or do anything that I choose to programme.
If I didn't want to use a microprocessor, how can I switch a 12V something on and then have it remain on even after the PIR detector has reset?
Basically, I am looking for the most simple circuit I can get away with, for no other reason than trying to not over-complicate things.


texts: LDO regulator (LD39300) output capacitor ESR not so small

texts:
I want to use the LDO regulator LD39300 of ST. To buffer VOUT, I thought about buffering the output in addition with an aluminum capacitor of 6800 µF in parallel to the recommended 4.7 µF.

But in the datasheet at page 10 (figure 14 and figure 15) it is described, that the ESR of the output capaitor must be bigger than ~0.3 ohm. Here is my problem, because an aluminum capacitor of 6800 µF often has only an ESR of a few milli ohm. In parallel to a ceramic capacitor the resulting ESR will be smaller than 0.3 ohm.

Is it right, that this LDO regulator will not work if I put such a buffering capacitor in parallel with the output capacitor?


texts: I need to bias some op amp inputs with a voltage. I’m in the 10-60 hz range. I need the bias voltage to be as low noise as possible, like -155 dbv . Would a voltage reference, voltage regulator, or even zener diode work the best here?  I’m confused as to which part would work the best. And do I need to drive the bias through a voltage buffer or can I put it right onto the inputs?


texts: Internal physical layer in microcontrollers

texts:
I am working on a project and while doing the component selection I realised that many microcontrollers have MAC & PHY layer on the different chip. Except for TM4C1294 microcontroller (there might be many out there).

So my question is is there any specific reason why MAC & PHY layer job is exported to dedicated chip out of controller ?


texts: Area of iron core to lift a certain amount of weigh(magnet/solenoid)?

texts:
I've been wondering and testing selfmade magnets by wrapping iron with wires and applying a voltage to it which makes it a bit magnetic. I've been looking around the internet and can't seem to find formula's or calculation examples on this subject. If I have wires of example 0.22mm² and a voltage of 3.3V, 2Amps, 25 turns, how big must the  iron core be to lift a weight of example 5 grams?

OR

How much voltage and current do I have to apply when I have a constant value of the thickness of the copper wire, windings and iron core to lift 5gr.

Also, if I halve the amount of windings but double the thickness of the copperwire, is that the same?

Apologies in advance for possible duplicates of this matter, I've tried to use this http://onlinecalculators.brainmeasures.com/Electric/SolenoidCoil.aspx

When I fill in:

Current = 2A
Area = 0.00439m2 = Cilinder with a diameter of 20mm and a length of 60mm
Number of turns = 25 turns
length of the gap = 0.001m = 1mm gap (I intent to touch the magnet if the intented object)
Results = 0.069N = 7 grams.

However, the calculator doesn't seem to care about the coil thickness/wire diameter which I doubt the results of it capabilty of lifting that amount of weight.


texts:
I have a load (resistance 3.4Ω) connected to a 6-volt DC supply, with a 2-watt 100Ω potentiometer which is set to ensure the current flowing through the load is set to 200mA.

It works fine but the potentiometer starts to get warm after a while.

I assumed a 2-watt potentiometer would be sufficient (0.2A * 6V = 1.2W).

Am I doing my calculations incorrectly?

Thanks.


texts: For Enhancement MOSFET why the threshold voltage absolute value be considered?

texts:
For the below question:

Why did he take the absolute value for the threshold voltage as shown below?

As far as I understand we plug in the values with their signs. Am I right?
This is from Sedra book:


texts: How to interpret wireless communication signals after being recorded?

texts:
Hypothetically, lets say you had a radio plugged into your computers microphone port. You record a certain specific signal in audio format to an .wav file. This signal is meant to be a small digital communication between small devices. They are using standard protocols, so no proprietary crap to worry about.

Does anything exist to be able to analyze this signal in this format?

I have been trying to manually analyze the captured signal just by looking at the waveform and comparing it to other waveforms I have seen on the internet, this is not working. I have looked everywhere for an automatic way of doing this, but all solutions seem to be hardware.

So I guess what I am looking for is a program that will take an audio file, analyze the waveform and spit out the original binary data.


texts: RC integral and differential functions, Schmitt triggers. How does this circuit work?

texts:
I'd be happy if someone explained me why this circuit is the way it is; how does it work ? Also i would like to know what the value for C1 is.

Taken from https://www.electroninvest.com/shop/items/sensors/801sshocksensorspecpdf.pdf


texts:
I have the following problem: I use to perform electrical experiments in a small room in an apart where other persons repair computers. It sometimes happens that I make the main differential switch break the power, causing inconvenience to the other persons. The cause of the failure is almost always a wire connected to the device under test that touches the box of the device, which is itself connected to the main ground. Of course, I could call an electrician to install a separate main lines for my room, but this is expensive and exaggerated for what I do. Instead, I've imagined to replace the main ground by a "virtual ground" that will play the same role, but without turning on the main differential. Here is a picture of the circuit, which works in simulations, and where the 2A fuse and additional LEDs have been omitted (the picture can be zoomed to see the details).
Let me examine if the operator is well protected:

1) If there is a short or an over-current flow, the (non represented) fuse will break, and even if it not breaks, the short circuit breaker of the main power line will still stop the current flow;

2) if some current flows from one of the wires to the earth (not the virtual ground labelled "GND" in the picture), the differential of the main power line will stop the current as usual;

3) finally, if one of the wires touches the virtual ground labelled "GND" in the picture (even through a reasonably small resistor), the solid state relay will stop the current too, and the main differential will see nothing.

My question is: have I missed something ? (I prefer to ask professional regarding safety).

EDIT: details regarding the operation of the circuit:
First, the whole circuit is inside a box, the input is the phase and neutral of the main power line. The output is 3 terminals labelled "phase", "neutral" and "GND" in the picture: the user use these 3 terminals as if they were the 3 terminals of the main power line.
Regarding the operation, the (opto) solid state relay input is powered by the 5V independent floating voltage source and is normally on because the 2P4M thyristor is not conducting. So, the current flows normally. If now "phase" or "neutral" come into contact with "GND" (through a failure of a connected device), then the thyristor is fired, bringing the voltage of the SSR input near ground. This causes the relay to shut down and the current is stopped.
NOTE: the 4k resistor in the circuit simulated a load in my simulations, and is actually not part of the circuit (I forgot to delete it before posting this image; sorry if this has confused some readers).


texts: Is there a popular footprint for right angle SMT LEDs?

texts:
I am designing a PCB with SMT LEDs at the edges. The LEDs have to be right-angle type (ie. shine sideways).

With regular LEDs I can use an 0805 or 0603 footprint and tell the assembly house to place whatever fits (the type/brightness/etc. is non-critical).

I have looked at right-angle LEDs and of course there is an abundance of them, but they seem to have many different footprints.

Is there a popular footprint for small and cheap right-angle SMT LEDs?


texts:
I'm new to AtmelStudio. I need to know how to generate a servo control signal using timer modules of atmega2560. I'm using an Arduino Mega board. (please refer the last paragraphs of this page for more info about servo control signals).

I'm not sure about how to do exact timing. The clock selection part is a bit confusing for me always.

How should I configure the timer module (TCCR registers) and how to do the timing? It's better if there's a working code example.

(I've tried using timer 0 under fast PWM mode. It gives pulses accordingly but I don't how to calculate proper timing pre-scalers. I've doubts about the primary clock used. Is it the 16MHz crystal on the Arduino board or is there some other inbuilt clock source inside the atmega2560 so that we have to explicitly mention which clock to use??)


texts: Getting a more stable signal on very long strips of adressable RGB LEDs

texts:
I need to drive a 12m strip of APA102 RGB LEDs (144 per meter). I use a Raspberry Pi for this Job.

This LED driver IC (APA102) takes an SPI signal and hands it to the next LED in the series and so on.
You can find the datasheet here with the circuit used on the strips I use shown on the last page: https://cdn-shop.adafruit.com/datasheets/APA102.pdf

I need to drive this LED strip at a rather high clock of 8MHz+ to get my desired frame rate.
This is working fine until I hit about 10m. Then the LEDs start to show wrong colors, start to flicker or just do nothing at all. The setup starts working again if I lower the clock to 4 Mhz but this is too slow for my application.

I need to use 5V PSUs with insane amount of current (30A for this one strip, a larger setup with strips in parallel will use multiple 120A PSUs) and they show some horrible noise (200-300mV) on the 5v output.

So I was wondering if there is anything I can do to improve my signal integrity?

I have a guess that the noise of the power supply slowly degrades the signal as its "refreshed" everytime it goes through a LED. Atleast thats what I gather from the schematic in the datasheet.
Attaching a 220uF cap to the power input on the LED strip improves the noise but it doesn't seem to have any affect on the signal degradation.

I understand that this is a bit of a ridiculous setup but I unfortunately don't have any other choice than to use this type of LEDs.

Edit: I feed power into the strip every meter, connecting directly to the PSU with 14AWG wire. So its probably not a power issue.

This is how clock (blue) and data (yellow) look on the scope after just ~60 LEDs.

This is after ~1500 LEDs. Purple is the 5V line.


texts: I'm doing a project which consists of 2 big parts: a control part (a microcontroller with I/O pins expanded, USART-to-USB, a RTC, an EEPROM, a LCD) working @ 5V and an actuators part (optocouplers for interfacing with the microcontroller's I/O pins, MOSFETs driving DC motors working @ 24V and TRIACs driving AC motors @ 230V~). Both parts of the project are supplied by a DC 24V power supply. So, am I achieving galvanic isolation between the control part and the actuators part using optocouplers, even though they have the same power supply, consequently the same GND signal?. Should I bother to separate the control part's GND from the actuators part's GND?


texts: Micro-controller drives solenoid 12 volt through interposing relay 5 volt issue

texts:
Purpose of attached circuit: driving a solenoid (cabinet lock) from microcontroller through relay with a 5 volt coil.
Components:

ATMEGA8
Relay 5 volt  with NO Contact
Solenoid 12 volt
power supply 12 volt
Regulator 7805 to generate 5 volts

Operation:

On state of controller pin: relay is energized and the contacts close and 12 volt feeds the solenoid and it is working well.
Off state of controller pin: relay is still energized and for sure the solenoid is still active. ( 3.9 volt is still there on the output pin of the controller.)
Off state of controller pin (in case the solenoid is disconnected from the circuit): relay is ee-energized, and it is working well as expected.

Note:

Logic in controller drives the output only.

The 7805 regulator is not mentioned in the above circuit.
Can you help me to find the issue which leads the output of the controller to be forced to high when the solenoid is connected and the controller output should be low?


texts:
I had so many problems with CircuitMaker (Free version of Altium), that I never want to use it anymore.

The problems I had so far:

Very cumbersome to deselect trace mode in PCB mode (having to get to find a free area outside the PCB borders)
Very hard to select items (e.g. to remove them)
Committing changes takes up to minutes
Lost several times some work due to CircuitMaker not responding (so committing is needed, but this takes a lot of time)
Access violations after having to wait for 30 seconds
Not able to place vias (see access violations)
Not able to deselect items (see access violations)
Even sending the bug report shows: Operations successfully: 503 Service Unavailable? Try again and shows the same file ... so even the bug send report is buggy.

I made quite a big circuit in CircuitMaker (btw, drawing circuits works very well). But now I want to convert it to KiCAD (which I used before and worked much better). Is this possible?


texts:
I am trying to derive the Type 2 Compensator by using TL431, and I read the C.Basso document
and I know how to derive the Type 1 Compensator, but I don't know why adding the capacitor (C2) at the Vfb will generate a pole and get this equation (the red line).
Can someone tell me how to get the red line equation?


texts: What is omega supression for a lock-in amplifier?

texts: I'm using a lock-in amplifier for PSD measurements.  The lock-in amplifier has an option for omega supression (in dB.) I'm unable to find resources on the lock-in amplifier's manual or online about what exactly this means.


texts: RF transmitter connected directly to sensor

texts:
I am trying to implement the following :

I got 2 (more than 1 anyway) distinct sensors and an arduino and I need to get the sensors' state wirelessly.

Here is what I have thought of so far:

As for the wireless part, I am going with 2 RF transmitters and an RF receiver (433Mhz - found this on ebay)

My problem is, I need to distinguish between the 2 RF transmissions. I do not expect them to go off at the same time, but I can't simply send a simple HIGH transmission. And I don't want another arduino controller simply to handle the sensor.

My thoughts were to implement a custom bit sequence per sensor using the following :

a 4-bit counter plus some logical gates to create the sequence
a 555 IC in astable mode serving as a clock
a 555 IC in monostable mode triggered by the sensor, triggering the RF transmission

Would this work? Will I have a problem receiving the sequence with my arduino?

This is actually my first try in electronics, so any help will be appreciated. I am open to suggestions if my thinking above wouldn't work.

Thanks in advance!


texts: How to determine the angular frequency of phasor?

texts: If I've got a voltage/intensity generator expressed in complex numbers, how can I determine \$w\$ to calculate the impedances?


texts: Detecting location of infrasound noise in a building

texts:
I am working in a large office building with a lot of people. Pretty frequently there is a very weak and low frequency noise that is very irritating. Unfortunately, I have found just one other person that can perceive it, so it must be at the utmost borders of what a human can hear. I have started searching for equipment that can detect the origin of this sound, but after some hours worth of effort I have not come up with much except some postings on this site about array microphones.

My questions are:

is an array microphone the correct way to solve the problem?
which types of microphone / sensors can detect weak, low-frequency sounds? I figure that a high amplification will also amplify noise.
are there other ways to locate the source of the sound? Maybe I'm overlooking ways to solve the problem.

EDIT: A sensor or other electronic part would help me as well.


texts:
I'm trying to put together a constant current sink circuit for discharging small Lithium-Ion coin cells. I need to be able to sink from about 200 uA to 12 mA. My first thought was to use some voltage regulators like the LM317 or the LP2951. Unfortunately for the LM317 as the battery discharges from 4.2V to 3V the sink current doesn't remain constant at low currents (see attached picture2.png).

I've attached the circuit (picture1.png)- I'm measuring voltage across the 10 Ohm resistor to measure current. R2 is a 256 step digital potentiometer to set sink current. In Multisim it seems like I shouldn't have a problem getting down to ~200 uA, but in practice, I don't get the same currents when the voltage source is at 3V or 4.2V (I'm using a power supply to simulate a battery). In the attached graph of current vs. pot value, I can only maintain stable current between 3 and 4.2V at currents > 1mA.

I tried the LP2951 in the same circuit but got even worse results (picture3.png). What gives? I thought the 2951 was a low dropout regulator, and so should have no problem with the low output voltage?

Does anyone have a suggestion for a better voltage regulator or circuit design for sinking such low currents?

Thanks!


texts: bldc motor, esc and battery draw, nominal vs peak

texts:
I want to better understand how Electronic Speed Controllers (ESC) work for BLDC motors. Specifically, I am trying to understand battery current draw.

Question 1:
When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.

Question 2:
If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that? I'm now thinking the draw will be more along the RMS value of the output pulse wave. This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.

Question 3: (slightly off topic)
To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear. I just want to understand the theory of how ESC's work at a high level.

Much thanks!


texts:
I have a circuit in my car which emulates the protocol the radio uses to communicate with a CD changer. The goal of the emulator is basically to make the radio open up it's audio channels.
The circuit works, but the audio lines pick up noise from the data lines (evidence of this is that for instance when a button on the radio is pressed, a different sound burst will occur).
When the audio cable is connected to my phone, the noise will be attenuated a bit, but nowhere near eliminated. Using a ground loop isolator does not do anything at all (I put it between the audio connector and my phone).
In the circuit, the left right and common audio signal wires are effectively directly connected to my phone, with only the connectors in between.
I would like to eliminate the noise by effectively making the audio signal go only 1 direction.
What would be the best way to achieve this? I was thinking along the lines of using a 1x gain amplifier, but I wouldn't know where to start with that.
Schematic:

PCB layout:


texts: Determine the node voltages va and vb for the circuit

texts:
I set up the equations $$ -\frac{V_a}{4\Omega} - 3A - \frac{V_a - V_b}{2\Omega} = 0 \\\frac{V_a - V_b}{2\Omega}  + \frac{V_b}{3\Omega} + 4\Omega = 0$$
However when I row reduce them I get $$V_a = -12 \\V_b = -12 $$
but the solution is:


texts: Switch between two digital signals with no microcontroller

texts:
I'd like to use an Arduino to send wirelessy (RF 433MHz, probably) two different digital signals to pilot two different relays (later they will be much more).

I know probably this is something very basic but is there a way to use just one RF and switch between two digital signals without the need of another microcontroller on the receiver? If so, which ICs do I need (demux, maybe)?

Very quick schematic, U1 is what I'm looking for

simulate this circuit – Schematic created using CircuitLab

A very dummy truth table could be this one:

SIG1 | Y1 | Y2

NONE |    GND  |      GND|

01  |     ON   |      GND|

10  |     GND |       ON |

Thank you for your help,


texts:
I know that in a gilbert mixer, you need to input the LO and an inverted LO.
Assuming the signal is about 100 mhz.
How could the signal be inverted, while keeping with the original amplitude, without an Op Amp?
The key is to not distort the shape of the signal, while inverting it.
Options I thought of:

Op Amp - but typically doesn't support 100 mhz

Common Emitter - won't keep a unity gain to voltage (especially if the hfe or beta of the transistor is uncertain).

Differential Amplifier - seems like the most promising option as the voltages across the two load resistors are inverted.

Are there any other fairly simple ways to invert an anslog signal?
Thanks kindly..
Edits:

The single transistor phase splitter idea suggested in a comnent is simpler than option 3 above (using a diferential amplifier). Thanks for the suggestion.

In an answer below, it is suggested that a Gilbert cell could be fed with a signal relative to ground, and not to its inverse. Would that hold generally or is it an enhancement provided by the NE602 to the basic Gilbert mixer?


texts: Double-throw switch with no common connection?

texts:
I need a DT, ON-OFF-ON switch to control two independent circuits with no common connection. I need something that behaves like either A and B, or C and D in the diagram below. Does such a thing exist?  This seems pretty straightforward, but I haven't been able to find one.

In the diagram, A closes one circuit and B closes the other; the other possible configuration would be one in which C closes one and D closes the other.

update:

Thanks for the suggestions.  Here's how the switch I bought works and how the pins are configured.  I just need to put a jumper across 2 and 5, which are common, and connect one circuit to 1 and 4 and the other circuit to 3 and 6.


texts: Protecting a wire linked to a power supply

texts:
I have a power supply of this kind: https://www.makerlab-electronics.com/my_uploads/2017/06/36V-Switching-Power-Supply-01.jpg
and wires linked to it like on https://i.ytimg.com/vi/DrZ8oupvzSE/hqdefault.jpg

But I often need to move all of it, this makes the wires turn and eventually the wires break. Would someone know which additional system could protect the wires, please?


texts: signal clipped despite q point is middle

texts:
Why is that the output signal is clipped despite the fact that the transistor's q point is located halfway of Vcc???

here is the schematic

and clipping here

From my analysis, as you can see, supply Vcc is around 40 volts and the multimeter reading of the collector voltage is around 20 volts (half of 40 so the q point / quiescent point is in the middle to avoid cut off and saturation)

Finally, you can also see that the output voltage swing is around 12 Volts rms (so that translates to 34 volts peak to peak, way far from the 40 volts of DC supply voltage)

Ref. http://www.mediafire.com/download.php?htnopk49oj1y9sj multisim


texts:
Fairly simple, I have a small 8pin chip on a board, and I have no idea what its doing, and cant find any information about it online. There are no manufacturer logos on it, and the serial number doesnt seem to come up anywhere. All 4 pins on the left side are connected to ground, and its difficult to see what the pins on the right are connected to. It may be connected to an SPI bus (the component on the right is a microcontroller).

The board actually seems like it should be fairly simple (just a microcontroller, a radio unit, and a keypad with some LEDs), but then there are a load of components connected near the battery and I have no idea why. One of them is a Vreg to bring the voltage down to 3.3V, but the rest...
I feel like this chip possibly has something to do with it. The board is also supposed to be very low power.

If you cant see the image, the serial is:
ATH342
08CM  Y
W0853RC


texts: Is the diagonal 10k too close? Am I good?


texts: Unsure of the role of these transistors while reverse engineering a keypad PCB

texts:
I am trying to reverse engineer this PCB from a keypad to use it with an Arduino, but my transistor based knowledge is a bit lacking.
I have gotten this far with regards to the architecture of the board; JP1 Pins 1-8 are connected to the bottom pin on TR1 to 8. All the bottom pins of TR1 to 8 are common, and go to Pin A on JP2. The middle pin on the transistor is connected to some of the switches, and the other side of the switches goes to pins 9 to 15.
I have drawn out the scenario for SW13 (In the orange box).
My issue is I don't really know where to go from here.

I can see maybe one of three scenarios;

I apply a voltage to pins A and 4, and monitor the state of pin 10
I apply a voltage to pins A and 10, and monitor the state of pin 4
I apply a voltage to pins 4 and 10, and monitor the state of pin A

I know I will have to scan it like a matrix, but I am fairly confident in how that works once I have things figured out electronically.
Or, I have things completely wrong.
For the sake of completeness, JP3 goes to a daughter board with another button and two LEDs on, and TR 9-13 seem to be LED related.(D1,D2)
The writing on the transistors appears to be 24 0E (or 0E) but I can't seem to find anything for this on google to help me find what type of transistor and what the pinout might be.
Any help on the right direction would be much appreciated.


texts: What should be considered when sizing trace widths for digital logic signals?

texts:
For traces that carry a static DC current, it's pretty easy to calculate the minimum trace width based on the required ampacity of the trace.  However, I'm not sure what should be considered when sizing a trace for CMOS, TTL, etc.

For example, if you've got flexibility in the board stackup and can make the trace thinner or wider and still meet the impedance requirements, what are the reasons for making the trace wider/thinner?

Do different logic families require different considerations for trace widths?

Are there reasons not to make digital logic traces as thin as possible to allow higher routing density with less crosstalk?


texts: 12v LED Strip Lights controlled by PIR *Want to add LDR to project*

texts:
I want to add an LDR (Light Dependent Resistor) to my Motion activated stair lights, then On/Off switch can be removed as well as the single Led (On Indicator Only) from my project (I want the LDR to control the On/Off). This is basically the first project I've done, so if someone could explain/show me what I need and how to set it up that would be great. Also, does anyone know of a great place for a beginner to learn about electronics? I would love to be able to build my own projects with out asking for help, thanks.

This is what my PIR LED stair lights look like

This is the link to video of the system working My Video


texts: How does this OP-AMP offset voltage measuring circuit work?

texts:
In the Operational Amplifiers part of Analog University from National Semiconductor, I saw an offset voltage measuring circuit for an OP-AMP. Here is the page. I've included some details and the schematic below:

It says that this is a very accurate way of measuring Vos. In LTspice, I've built this circuit with two LT1001 s and the output of the OP-AMP saturates to +5V. I used +5V and GND for the supplies.

In the page, it says that if +1V is applied to the "Servo Input", the output of the DUT will be +1V. I can understand that since the Servo OP-AMP will try to make its both inputs the same by changing its output voltage accordingly. Since there is almost no voltage drop across 10k in the non-inverting input of the Servo OP-AMP, output of the DUT will be +1V.

  For example, say the DUT has an offset voltage of +500 μV and NO gain errors and the Servo Input is set to +2.5V. The DUT's output will now be set to 2.5V and VOS will be at +500 mV regardless of the Servo Input setting. Any gain error would be summed in along with the offset voltage, and the result is multiplied by the loop gain (1000). With the Servo Input grounded the circuit basically functions as a "gain of 1000" test circuit. The Servo amp contributes very little in the way of offset errors (the servo amp's offset is divided 'down' by the loop gain).

I couldn't understand why Vos (output of the Servo OP-AMP?) will be at +500mV (that is the gain multiplied by the offset voltage of the DUT)? Both OP-AMPs are in each others feedback loop, however, DUT is in the positive feedback loop of the Servo. Why is that? It would be great that you include Vos as a voltage source when you are explaining.

(I am so puzzled and thus maybe I was not clear. Please notify me and I will edit accordingly.)


texts:
I've got an old analog (0-5ma) ammeter and want to convert it to measure 0-±5 volts, as an output for my Arduino.

I'm a programmer and my knowledge of electronics is limited. I know what components do but obviously not how to use them properly.

I tried to place some 2k (1 and 2) resistors in series with the ammeter but it doesn't work as expected. This was sortof working but is wasn't a linear movement even with a capacitor attached to + and - (+ and - come from the Arduino PWM/analog output)

simulate this circuit – Schematic created using CircuitLab

I know its a ammeter so it needs current and if theres nothing asking for current there will not be any so i put a very high resistor between + and - but that didn't really change anything.

So how can i change my am meter to measure 0-5v?

This is it opened, the resistance is about 2.9k (if I measured it correctly)

Could it be microAmps?

Hope some one can help, Thanks in advance.


texts: What is the strain gauge resistance variation of a 3-wire loadcell?

texts:
A 3-wire loadcell have two strain gages with a no load resistance of R.

When a load is applied, the resistance of one strain gauge will change to R+dR and the other will change to R-dR (because one stretches and the other one compress).

How can I calculate dR?

How can I calculate the dR for this sensor especification for example? Where I have a capacity of 50kg and an Output Sensitivity of 1mv/v ?

Thanks


texts: I have a 2000VA ups that contains 2 batteries ( 12V 9Ah ). I think that something happened to the batteries, since now they can barely handle an average laptop for about 3 minutes before shutting down the whole ups. there is any way to resurrect the batteries, or should I just buy new ones?


texts: ATX PSU turns off under heavy 12V load, unless increased gradually

texts:
Following the well known instructions I've built the PSU from a spare 500W ATX. I've used 10 Ohm resistor for artificial load on 5V line.
When I connect 1A load to 12V line, the ATX shuts off. I need to wait a bit and restart it.
This only happens if I connect the large load rapidly (i.e. turn on the LED driver with around 1A load).
When gradually increasing the load, I can reach 2.5A with no issues.
Say I connect a 0.5A load and it works. Let it run for a few minutes, then load it with 1A, let it run again and eventually I can have my 2.5A LED light connected.
I can turn off the ATX and turn it on again and it still works.
If I however keep it off for a few minutes and turn on again, connecting anything above ~0.8A causes immediate shutdown.
According to the sticker, 12V lines are rated 15A / 17A.
I've tried increasing the load using 3.2 Ohm (10R and 4R7 in parallel) but that didn't help.
Is the ATX faulty or have I overlooked something?
The only possible explanation that came to my mind is that the LEDs driver I'm using has some extreme power peak when warming up. So maybe it's not about turning off the PSU but about turning off the LED driver... will test it against some 12V motor


texts:
Can someone please help solving for my circuit connection, I'm new to this and somehow didnt manage to simulate the circuit correctly as the software stated this

Warning: Inductor-voltage source loop found: L1, Vdc4. Since inductors are short-circuited during the DC bias point calculation, the loop will cause a problem for most analyses. Consider breaking the loop by inserting a small series resistor.

. This topics is about RLC Transient Simulation.
Original question : In the circuit shown below, Vo = 5V, and Io = 0A. Plot vc versus t for R1=1.923Ohm at t>0.


texts: Is a low pass RC circuit the same thing as a first order Butterworth filter?

texts:
Is a low pass RC circuit the same thing as a first order Buterworth filter?

I was just curious because i googled Buterworth filter and they always show the filter with an inductor in the circuit.

Consider the transfer function for a low pass RC circuit:

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

and the magnitude response for a first order butter worth filter:

$$|H(j \omega)|= H(j\omega)~H(-j\omega)=\frac{1}{\sqrt{1+(\frac{\omega}{\omega_c})^2}}$$

The same thing or different animals?


texts:
I have an electronic load that I want to use to help me with some ATX switch mode power supply repairs.  The instructions that came with the load were rather sparse and I haven't found much for my particular situation on the net.  The electronic load is a CSI3710A sold by Circuit Specialist.  It is a rather inexpensive model and may not have lots of features but I may not need much. I just don't want to damage it or add more damage to the power supplies. I am confused about the Constant Current, Constant Voltage and Constant Resistance Modes and which one to use. When working with a PS that has the +12,+5 and -5 should I tap the +5 or does it matter? Does it matter if the PS is not putting out any voltage or a low voltage would that damage the load?  Anything else to watch out for?
Thanks


texts: I am trying to find a motor to use to spin a cardboard wheel to drop balls through a hole. I want this to happen pretty slowly, around 10rpm. It also needs almost no torque, as it is spinning cardboard. However, when trying to find a motor, all I can find is extremely fast motors with low torque  or slow motors with high torque. Both options are expensive. Does a very low cost, DC, low speed, low torque motor even exist? Thanks


texts: Is this an adequate design for a +3.3V / +9V / -9V power supply?

texts:
I'm building a small audio processing unit for my own needs and because of all the ICs used I need to use bipolar supplies + 3.3V for the digital parts. I'm going to build this over a pref-board, this might not be the best solution but I'm not going to spin a PCB for a single unit.

I think the general design is pretty clear from the schematic however some pointers:
* Diode is for reverse polarity protection. This circuit is powered from a 9VDC power brick which is already regulated. The diode might burn if the reverse polarity is for a long time but I am OK with that.
* The LCL filters are for removing high freq. from the analog supplies.
* I did not include a diode from the 3.3V to the Vin port (anode to 3.3V cathode to Vin) however it might be a good idea so that the caps form the circuit won't discharge into the regulator.

The grounds are shorted at a single point to prevent current from the digital part going through the analog part. Pointers and suggestions are appreciated.


texts: I need to understand the circuit diagram of a Klöckner Moeller relay output unit

texts:
I am working on the automation of an old servo driven feed system for a mechanical power press. I have come across these relay output units from Klöckner Moeller (machine make year 1980`s) pictures added.
.
I have a mechanical engineering background with a little know how of electronics.


texts: How is the extinction angle for a half wave rectifier with RL load calculated?

texts:
I have a couple of notes about the half wave rectifiers with the RL load, but I dont quite undestand how is obtained the extinction angle  \$\beta\$ ?

simulate this circuit – Schematic created using CircuitLab
Questions

\$I_{ODC}\$,\$V_{ORMS}\$

Resolution
First it is calculated the impedance
$$Z=\sqrt{R^2+L\omega^2}$$
$$Z=\sqrt{9^2+((18mH)(60)(2\pi)^2}=11.268\Omega$$
then the angle \$\phi\$
$$\phi=\frac{L\omega}{R}$$
$$\phi=tan^{-1}\frac{18mH*2\pi*60}{9}=36.99$$

Then it is calculated \$V_{ODC}\$
$$V_{ODC}=\frac{V_m}{2\pi}(1-cos\beta)=\frac{\sqrt{2}*180}{2\pi}(1-cos215)=52.11V$$
$$I_{ODC}=\frac{52.11}{9}=5.79A$$
for
$$V_{ORMS}=\frac{V_m}{2}\sqrt{(\frac{1}{\pi}(\beta-\frac{1}{2}sin2\beta))}$$
$$V_{ORMS}=\frac{\sqrt{2}*180}{2}\sqrt{(\frac{1}{\pi}(3.75-\frac{1}{2}sin2*215))}=91.997V$$

Discussion
While this seems to be an appropriate use of the definitions of DC and RMS values based on the definition using integrals and taking the idea that this is valid under a sine signal, the main issue is how is calculated the \$beta\$ angle since I see the value of 215 degrees but how was calculated?, I understand that the \$phi\$ angle its the difference of phase between the voltage and the current because of the induction effect, so I'm guessing this is added to \$pi\$ but this would yield 216.99 degrees not 215.

I calculate the \$\beta\$ from
$$\frac{V_m}{Z}\sin(\beta-\phi)+\sin(\phi)e^{\beta/\omega\tau}=0$$
using the circuit values
\$\omega\tau=2\pi*60*\frac{18mH}{9}=.753\$ in rads and the actual value from \$phi\$ in rads=0.645 so making the substitution on the equation before, it would be
$$\frac{\sqrt{2}*180}{11.268}\sin(\beta-.645)+\sin(.645)e^{\beta/.753}=0$$
Solving for \$beta=0.642\$ rads or 36.78 degrees, then this added to \$pi\$ would be 216.78 not 215. But why or how its justified I don't know.
I cant attend the lectures because of the job so I don't have more info and the people that I contacted does not know, even didn't notice this. It seems that the \$phi\$ value is used instead of \$\beta\$ and in this case are almost the same, but I have tried to solve problems like this and the values have a greater difference of 30 or 40 degrees, so I cant assume that the \$phi\$ values are used as an approximate to avoid solving the last equation, that I understand does not have a closed form solution.


texts: Booting multiple FPGAs using a single SPI Flash

texts:
I am using 3 Artix-7 FPGAs in my design.
Is it possible to use single SPI configuration Flash to program 3 FPGA device.
I have found information about multiple boots for one FPGA but not multiple FPGA booting using one boot memory.


texts: Modify MEMORY component to more sensibly Load/Store value?

texts:
I have created the following electrical circuit using Logisim:

My ALU takes in 2 8-bit values and performs the operation set forth by the [Op Setter].
In particular, when the [Op] code is [100], the 2 input values are added together.
If [Op] code is [100], and the [Sub Flag] is enabled, then B-input is subtracted from A-input.
The 8-bit result is output into Memory.

My [Memory] component as it stands currently allows me to specify which of the memory addresses to place the result in, with a CLR flag to clear out memory and a [R/W] button to complete the circuit and display value out to a single 7-segment display (with current circuit can only display first 4 bits of the ALU result).

How can I modify my Memory Component to function better as far as loading and storing the values sent to it? Currently the ALU result is simply stored in the specified address, but I would like to modify it where the circuit normally displays the ALU result in the 7-segment display, and IF, only IF, I have a [STORE] button enabled, STORE the value into memory for future use.

I would then like to incorporate a [LOAD] button to take place of either A-input or B-input in the ALU for the specified operation.

Can anyone offer some insight into this? I've thankfully started connecting the dots when it comes to Circuit Design, but I'm at a bit of a loss as to how to incorporate this LOAD/STORE functionality.


texts:
So I’ve wrapped my head around Differentiator. I understand how a small R will produce allow Vc to be ~Vin, for DC. And adding a load will mean that the current across R (not labeled but there) will decrease, and increase Vc. So there is: an output proportional to the rate of change of input.

The output proportional to the rate of change of input is dVc/dt in I = CdVc/dt. Here the proportion is times C. Attaching a load, it would be a fraction of I (aCdVc/dt) and then the voltage across it would be Rload * aCdVc/dt. Correct? And now, I imagine there are mA to uA and a resistor of 100k to get some voltage drop. Thinking quickly to get help, I’d love to know the uses of an output proportional to the rate of change of input and if this is how that output is used (i.e. Rload * a*CdVc/dt).

Kind of a tangent: a while ago I considered using an integrator to produce an LED that glows brighter.


texts: Storing data for a really really long time

texts:
How might one store data for the far future? (100 years and up, possibly centuries)
This is entirely hypothetical but would it be possible for semiconductor based data storage to have similar longevity compared to, for example, indents milled into a slab of metal?
Common NAND flash have rated data retention of somewhere around 20 years and I'm sure environmental factors like temperature and humidity would play a role as to the integrity of the silicon itself.
Assuming pretty reasonable physical conditions, what are some possible solutions to achieve much longer retention? I've heard periodic conditioning of the storage device by rewriting data may increase retention by a good amount. Would, say, an FRAM chip with memory controller that is powered on every month or so while kept in a favorable environment possibly achieve data retention of 100 years and beyond?


texts:
I would like to know how STM32F2 chips and below that doesn't handle floating point unit, perform float operation.

I read here, it mentions that the floating point is handled by library functions, but when I am writing my firmware code and I didn't include any library to handle those floating point operations.

Example: if I perform a simple float computation

float gain = 1.2 * 1.5;

I didn't include any external library, but it still able to compute the floating value? Or when I compiling, the compiler will handle it automatically for me?


texts: Opamp Inverting Amplifier: The case of non-inverting input not being connected to ground

texts:
What is the relation between \$V_i\$ and \$V_o\$ when the non-inverting input is supplied with a non-zero voltage level?

I have shared my formula derivation below, but I can't validate it since I can't find this special case anywhere on the internet.

Note: My interest comes from the circuit in this document (page 32, figure 25).

simulate this circuit – Schematic created using CircuitLab

My work:

Let \$A\$ be the gain of the opamp at linear region, and \$\pm V_{cc}\$ is large enough not to saturate the opamp.

$$ V_o = A(V_p - V_n) $$

From node voltages method:

$$ V_n = \dfrac{\dfrac{V_i}{R_i} + \dfrac{V_o}{R_f}}{\dfrac{1}{R_i} + \dfrac{1}{R_f}} = \dfrac{R_iV_o + R_fV_i}{R_i + R_f}$$

Then we have:

$$ V_o = A\left(V_p - V_n\right) = A\left(\dfrac{(R_i + R_f)V_p}{R_i + R_f} - \dfrac{R_iV_o + R_fV_i}{R_i + R_f} \right) $$

Rearranging the terms:

$$
V_o + \dfrac{AR_iV_o}{R_i + R_f} = A\left(\dfrac{(R_i + R_f)V_p}{R_i + R_f} - \dfrac{R_fV_i}{R_i + R_f} \right) \\
\left[ \dfrac{AR_i}{R_i + R_f} + 1 \right] V_o = A\left(\dfrac{(R_i + R_f)V_p}{R_i + R_f} - \dfrac{R_fV_i}{R_i + R_f} \right) \\
\dfrac{(A+1)R_i + R_f}{R_i + R_f} V_o = \dfrac{A(R_i + R_f)V_p}{R_i + R_f} - \dfrac{AR_fV_i}{R_i + R_f} \\
\left[(A+1)R_i + R_f\right] V_o = \left[A(R_i + R_f)V_p\right] - \left[AR_fV_i\right] \\
V_o = \dfrac{A(R_i + R_f)V_p}{(A+1)R_i + R_f} - \dfrac{AR_fV_i}{(A+1)R_i + R_f} \\
$$

If the gain \$A\$ is large enough, we can write:

$$ \lim\limits_{A \to \infty} V_o = \lim\limits_{A \to \infty} \left[\dfrac{A(R_i + R_f)V_p}{(A+1)R_i + R_f} - \dfrac{AR_fV_i}{(A+1)R_i + R_f}\right] = \dfrac{R_i + R_f}{R_i} V_p - \dfrac{R_f}{R_i} V_i $$

Then the formula is:

$$ \boxed{V_o = -\dfrac{R_f}{R_i} V_i + \dfrac{R_i + R_f}{R_i} V_p} $$

If \$V_p=0\$ we get the inverting amplifier equation:

$$ V_o = -\dfrac{R_f}{R_i} V_i $$

And, if \$V_i=0\$ we get the non-inverting amplifier equation:

$$ V_o = \dfrac{R_i + R_f}{R_i} V_p = \left(\dfrac{R_f}{R_i}+1\right) V_p $$

This looks like to be a mixed case in which it both works as inverting and non-inverting amplifier.


texts:
I am confused about the ground part of a voltage converter.

This is a typical voltage converter. As you can see the the main voltage is 230V, and the output is 5V. Look at the output 0V, which is connected to the diode node, so I know, yes, this is the ground node.

Here also comes the question: As we know, for the main voltage power plug, especially in Europe or Asia, there is a ground line in the plug, so how I am going to do with the GND line in the main gate? Where is it in this circuit? There are just two lines input!

Also for Europe, there is only two inputs in the plug, but also, if you look carefully, there is actually a GND node in it.

If I simulate the main power voltage in the circuit by the sinusoidal source, how I am going to do that?

One sinusoidal source power, one end is grounded, or
Two sinusoidal source power, opposite connected, and the node between them is grounded
Any other option?


texts:
I have a project where i need to run a python script on a microcontroller. The python script is basically a GUI based script using pyQt and the internal ram of a microcontroller isn't enough. After surfing the internet for hours I came to a conclusion that I will need a powerful microcontroller and an external SDRAM to support Linux and then run the script.

I don't know if that's the best way to run a python script, but if it is then how do i interface the Allwinner A13(or any cortex A microcontroller) with a huge SDRAM(about 200MBytes).

If you could guide me the right direction or suggest anything, it will be deeply appreciated.


texts: Hi all, I am very new to electronics. In the diagram shown here, where should I connect the pin of R4 variable resistor.


texts: speed control of Permanent magnet synchronous machine using digital signal processor

texts:
From a literature I found the entire speed control algorithm include SVPWM is implemented by a DSP TMS320F2808 with a clock frequency of 100 MHz.The speed loop and both d and q current loop sampling periods is 250 and 60 microsecond.
My question
Q.1 how the sampling time are different for both loop if they are sampled in same interrupt routine to calculate the necessary switching signal for field orient  control?
Q .2  How I set different sampling time for different loop in same program?
Q.3 Here actually what is the meaning of Sampling time?Is it related to Dynamics or stability in field orient control?
 I can't relate this to sampling of signal at required interval   I am confused little how field orient control actually work in PMSM using DSP.


texts: Ruggedizing a home-made High-Current SSPC

texts:
After establishing that we're not going to use our load bank in PWM mode (see here), I'm now trying to draft up a circuit that would be controlled by an µC (Arduino or else) and a multiplexer (this).

I'm also trying to protect the input from reverse voltage and overvoltage / making it able to cater with 1,8-24V digital input.

OK so here's my design thinking

1N4148 for reverse voltage protection
1,8V Zener diode for overvoltage protection (able to take 24V as a digital signal)
Resistor for current protection (500R ==> 10mA@5V)
This one I'm really not sure about : a 0,1µF in order for the whole contraption not to turn-off between two "cycles" of the multiplexer. I know that'd definitely be a no-go in a fast-switching application but that's not the case there...
I'm also guessing that the MUX chip will not change an output state between two update cycles but...

So anyway, I hope I'm not completely off on this and wait for your feedback.

So far what I take away :

My // diode is useless
I could use a P-channel transistor instead of a diode for reverse protection (avoids the diode Vf). Say something like this

But it also brings one question to my mind : would such an input protection be compatible with some high-speed input? Wouldn't the rise time of this p-channel transistor also add to the whole chain?

I cannot use a resistor to limit the current since my input voltage has a wide range

Where I'm still lost :

What should I use to limit current ? :-)
Is a zener diode used this way (through it's breakdown voltage) will really work at 10-40mA? If I refer to the datasheet Zener diode datasheet the Vz is way above the nominal 1,7V when above it's nominal 50µA. It's way above 3V at only 10mA
Would maybe just using a LDO such as this one solve all of that?

Thanks for the help!

Hi everyone,

OK so I'm still not confident in my zener overvoltage protection...

After some reading, I found that I have to make sure the zener is always going to be conducting some current or it might not be very effective at all...
So I'm going to add another resistor in // with the zener to ensure this minimum current. Not just completely sure that's the right way to do it.


texts: How does this compensation network work?

texts:
By accident I stumbled upon this Linear Technology application note (LT1074/LT1076 Design Manual):
https://www.analog.com/media/en/technical-documentation/application-notes/an44fa.pdf
Just for fun I simulated the positive to negative converter in Fig. 16. exactly as it is.

The authors state on page 26:

Positive to negative converters have a “right half plane zero” in the transfer function which makes them particularly hard to frequency stabilize, especially with low input voltage.

Why is this the case especially for low input voltage?
I see that the compensation network R1, R2, C4 is very important for input voltage Uin=5V and that there is ringing oscillation at the output when it is omitted.
I would like to understand from a theoretical point of view, what this network does: Why is it especially required for low input voltages and not for higher? Most interestingly, at higher input voltages it can be removed and the circuit is stable. I wonder also, why it is connected to the switch side of the inductor and not at the output?
At least in LTSpice it is very critical to use the stated values; changing the capacitor by factor 2 or 0.5 leads again to ringing in the output.
What is the key to understand this sensitive design?


texts: What is the best way to design voltage monitor with tri-colour LED?

texts:
I've built a power supply with regulated +15v, +12v, +5v, -12v and -15v outputs and I'd like to build a voltage monitor to let me know if any of the rails are above or below their stated voltage.

I have some tri-colour RGB LEDs (common cathode), the plan is that when the rail is at the correct voltage, the LED is green, it goes red when it detects over-voltage and blue if there's under-voltage (say, ~20mV either way).

I've tried building a circuit with the LM3914 bargraph driver chip but the problem with this is it requires a common anode LED if I want to use an RGB.  Also the chip is a 10 LED output and it seems wasteful to only use 3 outputs.

I've done some research and it seems like I could get something to work with op-amp comparators and either zener diodes or regulators as a reference but I don't really know enough about this yet.

Could someone please give me some advice with regards to the best way to go about this?


texts:
I have a DIY project, with the aim of building an (LED-based) stage/theatre light from scratch.

One of the challenges I've hit with this is getting DMX control to dim the LED. I spent some time looking for an 'out of the box' solution, but to no avail. This lead to researching some DIY options, and I've thought of three potential solutions. I'm unsure as to the feasibility of each, so your feedback would be much appreciated!

50W COB LED (32V): https://www.aliexpress.com/item/2Pcs-DIY-10W-20W-30W-50W-100W-IC-SMD-led-Integrated-cob-chips-High-power-Epistar/32742712881.html

1: Using an LED Strip DMX Controller and then boosting the (12V max) PWM output signal to 32V max. Unsure if there is equipment to boost the PWM signal correctly to match the 50W (32V) LED dimmer curve.

DMX Controller: https://www.aliexpress.com/item/Wholesale-4CH-4-channel-RGBW-Easy-DMX-Dmx-512-Decoder-Dimmer-Controller-Drive-DC5V-24V-for/32552218694.html

2: Taking a 12V power source, stepping it up to 32V via a variable boost converter. Then can dim the LED via a potentiometer connected to the 'voltage adjuster' on the boost converter. Figure out a method to control the 'voltage adjuster' / potentiometer via DMX. Unsure as to this part of it.

Boost Converter: https://www.aliexpress.com/item/1PCS-LOT-150W-Boost-Converter-DC-to-DC-10-32V-to-12-35V-Step-Up-Voltage/32444460864.html

3: Going full breadboard, building a controller from scratch. Something from the following documents. While I'm sure I could replicate the PCB designs shown, I would have absolutely no knowledge of what each component does.

http://www.mathertel.de/Arduino/DMXSpot.aspx
https://bluestampengineering.com/student-projects/matthew-h-3/

If anyone has any suggestions as to which approach would be best (or a seperate approach), or any improvements that would be much appreciated!!!


texts: How do I measure CO and CO2 concentration in a gas?

texts:
I'm looking for a document with a description of a method to measure CO and CO2 concentration on a gas.
I found some information about how to do it with infra red absorption, but not enough information to run a test.
I also saw something using a wire and a wheatstone bridge, but don't know what king of wire was that.
Is there another way?


texts:
I'm trying to make a board for controlling a reversible single phase induction motor. The board simply needs to be able to turn on/off the motor and control the direction.

My understanding is that for single phase motors some kind of capacitor is used to shift the phase of the AC input. So by switching which "line" the capacitor is connected to, direction control is established.

Going from a black box view of the motor would look something like this:

simulate this circuit – Schematic created using CircuitLab

To this:

simulate this circuit

Does that seem correct?

In reality it seems that 1 phase motors come with more complicated configurations. Some have 7 wires and support different voltages.

How should a control board interface (connections) look like if it is intended to support a variety of motors?

Maybe something based on this:

simulate this circuit

Would the above be considered a general interface to such motors (allowing the user to select his own)?


texts:
I want to design a circuit to control the output voltage generated by car alternator in a way that it shouldn't allow voltage to exceed 15V and also when the output voltage of alternator is less than 10 V, it must have the output voltage around 0 V. Actually it should approximately be able to convert The output Voltage of alternator between 10-14.7V to output voltage of 0-14V. The maximum output current of this device doesn't exceed 8A. I designed a circuit with MJ11016 and it worked well, but the problem is the size of this transistor, it makes my board very large (I used the similar circuit three times in my board). Can I use MOSFET instead of MJ11016 to control the voltage?

I designed another circuit as below, but the problem is that the drop voltage is 1.5V? How can I boost the voltage?


texts: Sizing the input current of a isolated standalone MOSFET gate driver for a stable output

texts:
After a suggestion from my previous question I'm planning to use this Photovoltaic isolated MOSFET gate driver to trigger a trigger input of this DAQ. It seems these devices do not require an auxiliary power supply. Below V1 is a 33Hz 0-5V pulse train input to the gate driver. Rtr is the input impedance of the trigger input of the DAQ where I guess it is at least 10Meg:

Digital input limitations of the DAQ is given as follows:

And here is the gate driver input current output voltage curve:

How can I size the input current hence R1 so that the trigger receives guarantee always between 1V to 5V input? The plot doesn't have much detail for 5V output.

The datasheet shows that the forward LED voltage drop is 1.4V at 5mA. In my case from Figure 3. it will be around 1.1V assuming I need 1mA input current.

So for 1mA R1 = (5V - 1.1V) / 1mA then R1 = 4k. But if I set the input current to 1mA; between 0 to 5mA Figure 1. curve is very steep which doesn't look stable. How can I size the resistor and current in that case for a more stable output around between 3V to 5V? A voltage divider at the output? I have no experience with this device.

edit:


texts: KSZ8863RLL and external PHY (KSZ8051RNL)

texts:
I'm designing an Ethernet switch with KSZ8863RLL. It's a 3-way switch but only has 2 integrated PHYs and for the 3rd port it has an RMII interface.

Datasheet says that the 3rd port can work in 'MII MAC mode' or 'MII PHY mode'. On power on the default is 'MII PHY mode' (page 58 -> Register 53).

For External PHY I'm going to use KSZ8051RNL.

Which mode do I need to use to connect an external PHY?


texts: 6 Wire Stepper motor with only 1 Center tap

texts:
I salvaged a stepper motor from an old computer i had laying around, it has 6 wires. The problem is that when i try and measure the resistance between the wires i only get 1 Center tap where the resistance is halved. All other 5 wires are connected to the same coil. I thought this was weird so i opened the motor and tried measuring the resistance directly from the leads on the board, but i got the same result as before.
Could it be that i have a 6 wire stepper motor with only 1 coil? Because all of the leads are connected in some way i have tried connecting them all (2 at a time) to an led, while turning the motor around, and the did lit up every time/combination i tried. Does anyone know what type of motor i have, because i have never seen one like this before. The yellow wire is the center wire (15 ohm, connected with all other 5 wires) the rest is 29,8 ohm (connected 1 by 1 except the yellow of course):


texts:
I recently put together a keyboard and had an issue with a couple switches so I decided to re-solder. I resoldered 2 and that fixed the issues but for this last one I started smelling something different than the solder/flux heating up. I'm thinking it was the pcb/fiberglass, and then it seemed as though the through hole plate started to come up so I was possibly making it too hot trying to remove this switch.

I removed the functionality of this switch so the keyboard is useable. I was wondering though if anyone has experience dealing/fixing these kinds of mistakes. And if you had any possible solutions? I thought about trying to drill it out but didn't have a small enough bit on hand.

Definitely learned some things from this experience and got some proper soldering iron rosin flux, tinning compound and brass non-abrasive cleaner for next time.

Edit: temperature setting I had it at was 350 on the dial.


texts:
simulate this circuit – Schematic created using CircuitLab

\$V_{cc}=20V\\V_{BE1}=V_{BE2}=0.5V\\V_{BE3}=0.6V\\\beta_1=\beta_2=100\\\beta_3=50\$

I need to find V in this circuit. I tried to use the path for KVL with the least unknowns but a lot of times I end up with linear dependent equations that leads to nowhere. It's been 3 hours since I'm trying and I didn't get anything close to a result on this. I think my major issue is (1) figuring out what path to take on KVL's equations and (2) figuring out when the KVL equation will be linear dependent of another one. What's a good approach to analyze circuits like this?


texts: If I re-scale my input range for differential input to ADC, can I double resolution?

texts:
I'm just building my first separate ADC circuit, after deciding Arduino was limiting me too much / it is just time to start understanding how to do things properly.

I currently am using a LT1290 ADC with a LT1027 5V reference. I have essentially stuck to exactly the example circuit given in the data sheet to get started, it is what I need anyway. I am currently sticking with single-inputs.

I was just wondering if by re-scaling my input signal from 0to5V to -5Vto+5V, and feeding this in as a differential input, is this an easy way of doubling the resolution (2 x 4096)? Or is there a high price to pay in accuracy compared to the increased complexity of the needed circuit?

Thanks


texts: Help identify 6 pin SMD - top mark MAW - found near BIOS on motherboards and GPUs

texts:
I need help to identify a SMD component of 6 pin, without manufacturer. Only mark "MAW". Seems it is commonly used for BIOS circuit on motherboards and GPUs. I need to replace it by a new one.
Attached an image as example:


texts: NRF24L01+ (RF Module) for Smart Home Device Communcation

texts:
A while back I purchased these RF modules (NRF24L01+) and I am starting a project using them; the project is implementing a network of smart devices as slaves connected to a central wifi-enabled hub (Esp8266 or Raspberry PI, most likely). I've done some research on wifi, BT, and Zigbee-based sensor/slave networks, but I am having trouble seeing where these RF modules fit.

Specifically, I'm having some trouble understanding if these RF modules can be used in a similar way to Wifi, BT, or Zigbee-based home automation setups. I can't find many resources for implementing a slave network with this kind of RF communication module nor many commercial products that appear to use these, and my question is: do these modules have any technical barriers that would not allow them to be implemented in or that would make them less-suited for this application?


texts: FIFO Buffer (Circular/ring buffer) for packet storage

texts:
I am developing a simple radio transmission network using B-L072Z-LRWAN1 boards. The network structure is formed by:

One board acting as a gateway (where data is received).
Multiple boards acting as nodes (which send data to the gateway).

The packet payload sent by nodes is N bytes long and I want to store this packet's information in case gateway stops working and nodes cannot communicate with it. I want to keep data that could not be sent by the node and send it once the gateway is active again.

Let's say I want to keep the last M messages that node could not send to the gateway. The buffer size should be M*N bytes long, but how do I implement this type of buffer in C?

Thank you in advance!


texts: Suppose I connect an AC voltage source (frequency = 7hz) to a coil, the coil will resonate and radiate an electromagnetic wave. What's the frequency of the radiated wave and does it depend on the dimensions of the coil and its number of turns? Thanks!


texts: PIC microcontroller programmer/debugger tools for beginner

texts:
I am a final year student and am going to use a PIC device for my project, so am getting familiar with it early.

I will be using MPLAB X IDE to program the PIC. How is the code actually downloaded onto the microcontroller? I have read that the 'PIC KIT 3' programmer/debugger is the easiest.
With the PIC KIT 3, is it possible to debug online in real time and see the status of I/O pins and registers etc?
What other methods are available to program a PIC?


texts:
I need a radar system to sense a movable object within [0..150 meter] range. The desired accuracy is around 100 micron. However, at far distance 1 mm could be fine.

As far as I read, 3D Lidar systems can not achieve this level of accuracy (correct me if I am wrong please).

Stereo camera systems can achieve this level of accuracy theoretically. However, designing such system is not practical at all due to the high focal length and baseline needed.

What are other possible options that are practical for the desired working range and accuracy?

Edit (More information):

The object moves relatively slow (less than 1 meter/sec, most of the time few centimeters per second)
The object size is around 30*30*30 cm^3. However, the reference point of the object can be added. For example, in the Stereo Vision suggested solution I was about to add a very small red led. So, the reference point can be customized for the application.
The object can rotate around itself.


texts:
How to find the voltage rating of a capacitor after knowing the capacitance value.

Example,
For a power supply, If the input voltage is 60V and output is 5V. The input capacitor(C1) value is 100uf and output capacitor value is 1000uf.

What is the voltage rating for both the capacitors and how to find them.


texts: MAX999 draws current through negative input

texts:
I have two versions of the input signal:

5V inactive level, 3.2V active;
5V inactive level, 0V active level.

Thinking on making universal circuit to support both signals, I decided to use comparator, having threshold voltage at about 4V. Here's the circuit:

I built a prototype, and it shows unexpected (for me) behavior:

Red is voltage on positive input pin, yellow is on negative. Capacitor C58 was removed.

Searching through internet I found this question. It is about operational amplifier, and not about comparator. But I took a closer look into the datasheet, and found the following:

  Differential Input Clamp Voltage --- VCC = 5.5V, VIN- = 0V, IIN+ = 100µA --- 2.1 V

Is it the information I should be looking at? Does it mean that voltage between + and - inputs must be not larger than 2.1 V, otherwise there will be current path between the inputs? Is it naive to assume that if I have comparator powered from 5V, that it must be able to properly handle differential voltages on the whole power scale? And why datasheet does not state that there's such a limitation in its headline?

Update:

After considering answers below I decided to stick with MAX999 so far, and designed the following circuit:

I still think it is an overkill, but at least it is expected to work properly:

supply current is about 8 mA. In my previous simulations MAX999 model was failing when IN+ was approaching IN- starting consuming about 60 mA, most probably because of issues in definition of the input stage circuitry.
digital input was resized and re-leveled (green), with reference voltage placed into the exact center of the worst case for the input signal;
circuit draws less than 1 mA from the positive input, and almost nothing through the negative input;
power on current is much less than 10 mA, limited by the 470 Ohm resistor;
differential voltage does never go out of 2.1 V range.


texts: Translate low logic level to higher voltage range

texts:
I need to shift a digital signal from an MCU to a higher voltage range. The MCU outputs 0-5V and I need to give this Signal inverted to a higher voltage rail.

In the picture you can see what I try to achieve. The blue graph is the output of the MCU. The yellow graph is the Output I would like to generate. Here the HIGH Signal is 20V and the LOW Signal is 15V.

The voltages given are 0V(gnd), 5V and 20V.

I thought of using a opamp to shift the Signal to a higher voltage but I am confused on how to generate the 15V I need

Thanks for any advice :)

EDIT

I need the level tranlation in both directions!


texts:
I just bough 2 MFRC522 RFID reader from a different store. Both of them work well to read a standard 13.56 Mhz tags.

However, one of them have "MH" marking while the other doesnt. The one with MH marking able to read UID of a e-money card in my country (as of now I'm still looking for the tech detail of the card), while the other one cannot read it.

I try to swap the inductor (L1 and L2) between them and surprisingly, the original reader with MH marking now unable to read the e-money card, while the newly-swapped reader now able to read the e-money card.

Unfortunately, I dont have access to precise LC meter to measure the inductance of L1 and L2.
So, what is the different between MFRC522 with "MH" marking with others?


texts: Recommendations for 24V to 5V AC/DC converter

texts: I'm working on an ESP8266 thermostat that should be powered by the 24V AC from the furnace. I'm looking for a converter to 5V DC that would be small enough to fit in a smaller enclosure and not dissipate too much heat. Not fully sure about the current, but I'm planning for up to 500 mA for short periods of time. I found on ebay this, but it accepts input from 85V upwards. What would happen if I would feed 24V AC to it? Would it still work. Or alternatively doesn anyone have a link for something similar that would work with 24V?


texts: Resistor near point-of-contact for better ESD-protection?

texts:
This question is about ESD-protection while installing/removing components (RAM, SSDs, etc.) inside a PC.

When grounding the GND of an USB-port to earth or to my wrist strap (as advised earlier) the moment-of-contact would be the moment i plug the USB-cable (which is attached to my wrist strap somehow) into the USB-port.

So, the USB-port is the point-of-contact where an ESD-event (due to a potential-difference) could happen at the moment-of-contact.

In theory, is the USB-port better protected when the resistor is nearby?

(Maybe far fetched question, but i'm wondering on which end of my self-made cable i should place a resistor.)


texts: Oscilloscope as monochrome bitmap image viewer

texts: Iam a beginner in arduino and other open source platform programming and  I came across a DIY project which involves using oscilloscope as an image viewer,but this project involves ATmega16 AVR IC1 microcontoller (the schematic is given in the image following)  .Can this project be done using arduino,if possible can anybody give me the sketch for the program.Thank you.


texts: What data is typically stored on RFID cards and why?

texts:
I understand that all RFID cards contain a UID in their memory from manufacture, normally in sector 0. But they also have additional sectors for data storage, my question is what is some example data that would be stored on these cards?
Saying for example that the example data could be user access rights, I can't seem to understand why this data would be stored directly onto the card itself and not on the backend where the readers do a UID check, is it to prevent easy cloning?

In my experience from some extremely limited RFID security research is that most organisations implementing RFID cards are simply utilising the cards UID and the rest of the storage is blank.


texts: Mechanism of transformer secondary current

texts:
When a transformer has the secondary open and it's driven by an AC source, the only current that the primary draws is the current needed to produce the flux to magnetize the core (like ferrite) of the transformer.

Then we put a load on the secondary, that is, a resistor across the secondary coil. Now the primary draws more current: Let's say this is a step-up transformer, so we know that the voltage across the secondary coil is some multiple of the voltage across the primary coil. To get the current on the secondary, we divide the stepped-up voltage by the resistance of the resistor. To preserve energy, the primary must now draw more current to make the power (product of voltage and current) the same on both sides.

But what is the actual physical mechanism (for the lack of a better word) why this extra current must be drawn by the primary? I mean, the nature doesn't know that we have a law of energy conservation, or that the product of voltage and current must be the same on both sides.

I suppose this has something to with fluxes. The magnetizing current sets the flux that puts the stepped up voltage across the secondary coil. This voltage causes current to flow on the secondary. This current oscillates and passes through the secondary coil, therefore producing magnetic flux. Now the core has flux from the magnetizing current and from the bigger current now flowing in the secondary. So apparently now the primary "wants to" combat this flux from the secondary with a flux of it's own, therefore "pushing" more current (more than the initial magnetizing current) through it's own coil (the primary coil of the transformer). I also understand why it makes sense that the current ratio is the same as the coil ratio: If the secondary has more turns, the primary needs more current to produce the same flux as the secondary (secondary has more turns so with smaller current the magnetic fields from all turns add).

I'm also familiar with the equivalent model of the transformer and how the ideal transformer differs from a real one. Looking at the equivalent model has not helped me. So what is the physical reason why more current "has to" flow into the primary when current is drawn from the secondary?


texts: How to receive 40V-DC to 100V-DC range analog output into 9V-DC to 24V-DC analog input?

texts:
I am software guy and this is my first time here. So pardon me for my lack of understanding.

I have a device with analog input, that can read analog input in the form of DC Voltage within the range of 9V-DC to 24V-DC. The source of analog output emits the analog output in the form of DC voltage in the range of 40V-DC to 100V-DC.

How do I receive the analog value in my device?

I find on the internet that there is a DC-DC converter but those are usually fixed voltage input and output. And as you can see, my system requires variable range input and output.

For ex:

100V converts to 24V
60V converts to 16.5V
40V converts to 9V

After I read the value successfully, at the firmware level, I can display the value of 24V into 100V. It's just that I cannot read the 100V value directly because the device has a higher limit of being able to read up to 24V only.


texts:
I recently found my old Raspberry Pi laying in a drawer and I took a look at it. I noticed that the conductor traces are in a zigzag form.

What's the reason behind this? Especially because there's plenty of space to just make a straight trace.

I am sure there has to be reason for this because I have never noticed this on the PCBs I deal with at work.


texts: radio having DC 7.4 V 1000 mA battery, giving 3 hours back up play back. Now want to replace battery and directly on DC adapter and do not want back up, but plug and play. So what should be the adapter ratings?


texts: Serial pins, and PC USB port damaged using a USB to Serial converter (PL2303HX)

texts:
I am working in a project for getting data from a Load Cell, in the project I use a very good Shield built by a very good friend, this shield has a PGA (Programable Gain Amplifier), a Fast ADC chip, and a voltage regulator (to get 5.0 +/- 0.1 V). This shield is over an Arduino Uno, and when I get a command from Serial port I start getting and printing the time and the load cell voltage data each 1 ms, and this is working pretty nice!.

The Arduino is powered by a 120 AC to 5VDC adapter (see the photo attached), this 5 VDC are elevated to ~8 VDC by a

LM2587S-DC-DC-Step-Up-Adjustable-Boost-Power-Supply-Module-Converter-Regulator, see this link

https://www.ebay.com.au/itm/LM2587S-DC-DC-Step-Up-Adjustable-Boost-Power-Supply-Module-Converter-Regulator-/192262886299

this was because of I wasn't able to get a 120 AC to 8 VDC adapter, and these 8 VDC (I need 8 volts for the 5.0 V regulator mentioned above) are plugged into the jack power conector of the Arduino Uno,

The data from the serial port goes to a USB to Serial Rs232 cable converter, this use a PL2303HX chip (look the link down), and this is conected to the pc with a 3 m USB extension

https://www.amazon.com/Armorview-PL2303HX-Cable-Module-Converter/dp/B008AGDTA4

The problem is that this is the second time that I heard something like an electric short and all the things conected to the Serial port is damaged, I mean the PC USB port, the Serial to USB cable Converter, the Arduino (once) and the Arduino serial port (in the other time).

Looking for what happened I opened the USB to Serial Cable and I saw something like a fingerprint of a spark (see the photos attached), and how you can see this happened in the power line. According to this I guess that this was an overvoltage or an overcurrent in the PC usb port, but the other things like mouse and keyboard didn't fail.

I was wondering if someone could help me to understand what happened, I appreciate any idea.

thanks
Thanks for your answers, @Ali_Chen this is a block diagram of my circuit

I don't need exactly 8 volts, but I need 7 V or more for the power jack to power the Arduino, so I choose 8 volts, I use the booster because I couldn't find more than 5V or 12V adapters, and with the 12V regulator of the arduino gets pretty hot, so I prefer to use the booster.

@Ali Chen I saw that too, that the damage was in the power lines, and for that reason I guess that was an over voltage or over current from the pc USB port, but do you think that too?

@slightlynybbled, I had purchase a better supplier USB-TTL cable from SEED, but I buy it from Digikey,

https://www.digikey.com/product-detail/en/seeed-technology-co-ltd/321010012/321010012-ND/5487751

I know this is not as good as Adafruit once, but I am in Colombia and it is really difficult to get this things because I have to pay for shipment and some taxes when it get into the country

excuse me for all the comments in the same answer.


texts: High voltage 1100 V current sense on the high side

texts:
I have the circuit that you see below.

My load is a photomultiplier tube equivalent to a 3.63Mohm resistor.

My power supply can deliver max 4W (2kV and 2mA). I use it on 1100V and the load draws ~350uA. I want to monitor the current with the shunt resistor technique. Only high side current sense would work, because the load is tied to the circuit ground. I possess 0.1% tolerance resistors up to 500 ohm and 1% tolerance up to 1Mohm. I can spare up to 10 volts to drop across the shunt resistor.

I can't find a circuit with current amplifier able to withstand the 1100 volts relative to the ground on its inputs.

Any ideas?

PS:

I've seen the Maxim application note with the optocoupler, but it won't work on my simulation package (multisim). I'm currently awaiting the ICs to test it for real.


texts: Original 555 timer transistor output implementation

texts:
I am a beginner casual electronics hobbyist trying to learn about how chips work internally. In order to accomplish, this I went out and got a 555 timer soldering kit and started experimenting with it.... things are not going so well.

I am working my way through the circuit as best as I can but I am currenlty stuck on the output stage section of the circuit, I am simply unable to understand how that works and I was hoping someone could lend me a hand.

For your reference, below is the original 555 timer schematics:

After looking at the diagram and reading throug some of the documentaion, I learned that the output stage constist of transistors Q20 throug Q24. With that in mind, in an effort to try to undetand how all this works, I tried to isolate the output stage from the circuit and recreate it using an online circuit simulator. This is what I did:

The problem is that the circuit does not work as expected (output does not sink and source current). Could someone please tell my what am I doing wrong? What do I need to do to my online symulator circuit to make it work? I would like to get it to work on the symulator so that once working I can mess aroudn with it and see if I am able to figure out how all these works.

click here to be taken to the online simulator

Thanks.


texts: Definition of terms for a Synchronous Current-mode Buck Regulator?

texts:
I was reading the datasheet of MP1482 chip which is buck regulator,
I have read some of terms in the datasheet I did not understand could any one explain it in simple world.

The MP1482 is a monolithic synchronous buck regulator

What is a Synchronous regulator?
Are there asynchronous regulators?

The MP1482 is a synchronous rectified, current-mode

What is a current-mode regulator?
Are there voltage-mode regulators?


texts: ws2812 strips data grounding method & flickering

texts:
I know for ws2812 strips (60ppm) you can ground the data line at the far end to reduce the chance for "echos" and improve performance.

My question is can you:

Short the data tab to the ground tab at the end of the strip (with a resistor I assume?)?
Or do you have to run a line back up to the ground wire going into the strip?
Or does it have to be a seperate line all the way back to the ground on the power source?

For a bit of background I have a Pi3 running 18 x 1m strips in parallel. The strips are powered by 2 x 40A PSU, one is powering 8 strips, the other 10. Everything works if I only attach the data line to the collection of 8, or the collection of 10, but connect both sets and flickering occurs. I've common grounded the Pi3 and both PSU, but still getting flickering. In case it's relevent, when all connected it's the collection of 8 which flicker.

I feel this is more to do with grounding 2 PSU that are supplying different loads? But grounding the data lines is an easy(ish) possibility to rule out.

Additional
The pins are driven by the D18 pin on a Pi3, although i have tried this with a nano with the same result.

When I say flickering I mean that with a changing colour-wheel animation, one set is flicking between inconsistant colours, not matching the other room until i disconnect one or the other.

Solved
In addition to @CrossRoads answer, it turned out that using pygame's mixer at the same time as the led strips causes issues on a Pi3. I noticed that after loading the strips the audio would degrade drastically.

Moving the strips to an Arduino solved both problems:
 - Arduino supports multiple strips on multiple digital pins, where the Pi can only use D18.
 - Removing the strips from the Pi3 solved the audio issues

Now the PI3 sends serial commands, via USB, to the arduino which in turn controls the strips.

Thanks all for your help.


texts:
I have just managed to control an old LCD of type TLX-1013-E0 using an arduino. I would now like to use it for a project. But it needs -10V for the contrast and 170V for the background lighting.

Could anyone suggest a nice way of creating these from a small 5V source. Both obviously won't have a big load.

Cheers
Chris


texts: Do i need additional IOs for this interface board?

texts:
I am designing a UI PCB which has an MCU which will interface with a main system controller (MSC) on a separate PCB.
The UI PCB provides an initial power up to the MSC which then boots up its onboard PSU and everything else. Additionally it should read messages from the main system controller to provide on the UI (LED's, display etc.). Finally it has buttons to power on, or reset the main system controller.
The UI PCB communicates with the MSC using CAN bus.
I was just wondering if I would need additional IO's between the two PCBs? Can I send the data from the buttons on the UI board (like if it was being used as a state machine) as a message on CAN bus? Or would using a simple GPIO make more sense for this?


texts:
For my personel project, I would like to resize an LCD. I know that it is a possible to cut an LCD horizontally with a laser cutter.

However I don't know how they do this.

As far as I understand, I have to seal the LCD somehow. Can you please advise me how can I do that?

I am a PhD student in a technical university, so I can reach more or less all the equipment.