texts: Measuring speed with Input Capture Mode [STM32 & CubeMx]

texts:
I have the L432KC Nucleo. I'm trying to measure low speeds with a 1 PPR (pulse per revolution) sensor. For low PPRs, using the Period Measurement Method is suggested. If I get the period of the signal, then I can apply the formula:

RPM = 60/(Pulse Period)

This is what I have:

In CubeMx I've set Timer 2, Channel 3 Input Capture Mode. My APB2 frequency is 1 MHz. The TIM2 prescaler is 1000 and the counter period is 10000. Everytime a pulse is given, a falling edge occurs.

Now, in the code I have:

void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim)
{
  /* Prevent unused argument(s) compilation warning */
  UNUSED(htim);

  /* NOTE : This function should not be modified, when the callback is needed,
            the HAL_TIM_IC_CaptureCallback could be implemented in the user file
   */
  if(htim->Instance == TIM2){
      inputCaptureVal = __HAL_TIM_GetCounter(htim);
      __HAL_TIM_SetCounter(htim,0);
  }
}

In the while loop I have another variable:

counterVal = __HAL_TIM_GetCounter(htim2);

Is this the right way to get the period? I would appreciate any guidance as this is my first time using input capture.


texts: Vcc and multiple USB Devices on one board

texts:
I'm working on a prototype board which has multiple USB device connectors (e.g. the one for a microcontroller thing I'm communicating with, and a second one for JTAG).

Now I wonder how I should treat the VCC line, because I'd like to power the board from either USB connector.

Sure, I can put a Schottky diode in line with each VCC and call it a day. I don't want the voltage drop though. I power some things from 5V and on some USB hosts I already see voltages as low as 4.5V instead of 5V. Loosing another 0.3V or so would be critical.

Since I'm going to power the device from a single USB Hub anyway, would it be okay to just connect the two VCC lines? The only other option I can see now is to forget about USB power, leave VCC open and use an external power supply.


texts:
I've just ordered some sample LCD displays. The only model available for now is hot bar solder (instead of a regular connector).

Do you have any experience soldering regular thin wires to this type of connector? It seems like a 25 mil pitch.


texts: Considerations for switch mode power supply with microcontroller and sensors

texts:
I'm fairly new to this forum and the entire field of electrical engineering. I have a microcontroller (Atmega328P) project that includes a current sensor and several radios (900Mhz-2.4ghz). It is battery powered from a lithium 36V nominal battery. I was looking at using the LM46002 simple switcher from texas instruments to power my project.

However, as I delve deeper into the design I'm not sure what switching frequency to use, and also what supporting circuitry I might need such as bypass capacitors and the such to help smooth the output. I will be making ADC measurements and the same question applies to the ADC circuitry - what considerations will I have to make with the design to best power my project and get the most accurate measurements.

Thanks for your time :)


texts:
So I am taking a signal processing course in EE and my professor is an Engineer who really likes math however his book which we use for the class falls in the dreadful purgatory of math books in my opinion: too "rigorous" to be intuitive and way too abridged and takes leaps which make it impossible to consider rigorous.

It leaves me scratching my head on the chapter on the relationship between z-transforms, Fourier transforms, DTFTs and DFTs.

Here are some extracts from the book:

  Comparing \$V(z)\$ (implicitly meaning the z transform of a sequence say v[n]) with the Laplace transform \$V_s(s)\$ we note that the two transforms are realted by a simple change of variables. In particular letting  \$z = e^{Ts}\$
  we have:

  \$V(z)|_{z = e^{Ts}} = V(e^{Ts}) = \sum\limits_{n = - \infty }^{\infty}v_c(nT)e^{-nTs} = V_s(s)\$ (where \$V_s\$ is the Laplace transform of the ideally sampled function-with --fs = 1/T--\$v_c\$ which itself has a Laplace transform)

Now this is where he starts losing me:

  We note that the transformation  \$z = e^{Ts}\$  transforms the axis \$s = j\omega\$ into the unit circle : \$z = e^{j\omega t} = e^{j\Omega}\$ where \$\Omega \triangleq \omega T\$ which is the relation between the discrete-time domain angular frequency \$\Omega\$ in radians and the angular frequency of the continuous-time domain frequency \$\omega\$ in radians/s. The vertical line \$s = \sigma_0 + j\omega\$ in the s plane is transformed into a circle \$z = e^{\sigma_0 T } e^{jT\omega}\$ in the z-plane. In fact a pole at \$s = \alpha +j\beta\$ is transformed into a pole \$z = e^{(\alpha + j\beta)T}\$ of radius \$r = e^{\alpha T}\$ and angle \$\Omega = \beta T\$ in the z plane.

That last paragraph doesn't mean much to me and I am having a hard time with the following concepts which seem pretty important:

What does a discrete-time domain angular frequency stand for?
What does he mean by the z plane in that context
In the end if we consider transforms as morphism (I absolutely have not enough serious math background to consider morphisms for functional spaces but have some intuition into the concept form isomorphims in abstract LA), does he mean that the substitution \$z = e^{j\omega T}\$ is a morphism from "a sort of functional space resulting from the application of the z transform to sequences " to "a functional space consisting of complex functions defined on the circle?" (sorry if that last bit was cringy for some of you, just trying to get a grasp, thanks)


texts: What is the difference between CMSIS RTOS and Keil RTX?

texts:
I have read the articles about them separately, but there are no information about the relation between them.

What I understood is that there is CMSIS RTOS that ARM created and Keil extended it to CMSIS RTOS RTX? If this assumption is not correct then what is the relation between them?


texts:
I have a system like this:
RPi -> FTDI(USB UART IC) -> RS485 transceiver -> RS485 TO USB board -> PC

I'm having some trouble testing RS485 communication between the RPi and the PC.
I'm using a simple python based tutorial: https://www.waveshare.com/wiki/Raspberry_Pi_Tutorial_Series:_Serial

I'm using putty on PC to read 'hello world'. However when I run the python code on RPi, I don't see anything on putty.
I have verified the tty port, COM port, baud rate, and wire connections.

What am I missing?
Please help, thanks.

EDIT: I've attached schematic of USB to RS485 circuit. The USB data lines are connected to the RPi USB. I want to test RS-485 interface functionality. Please advice


texts:
We're working on a car where we've replaced most of the electrical system.
We've also replaced the transmission, and the new gear box doesn't have a speed sensor that we can use for the instrument.

We're replacing that with signals coming from the ABS-sensors but passed through an ECU.

The signal generated by the ECU is a 0-12V square wave with frequency linear to rotation speed (0-800Hz). The instrument takes a sine wave signal with varying frequency. We need help designing a circuit to achieve this conversion.

We've previously tried simple solutions

But for whatever reason (not sine-like enough?) it's not working.

Super thankful for any help! At work right now so my only tool for drawing graphs is paint. Sorry.


texts:
I have a simple (yet probably stupid question, since my knowledge of analog circtuits is very limited) about voltage dividers.
The final goal is to measure AC current for a mains load; to that end, a Hall 5A sensor (ACS724) followed by a RMS-to-DC (LTC1966) conversion circuit is tested.
It is not working, so I'm breaking down the problems I see.
Here's the first one.
Since I'm measuring AC, the Hall sensor's output should be a voltage proportional to the AC current, offset by Vcc/2, right ? Ideally a sine wave at 50Hz; so I'm trying to feed its output along with Vcc/2 to the next component that has a differential input (the LTC1966.)
On the breadboard, I use a 5V power supply (from a USB charger,) followed by a 3.3V LDO regulator (an LD1117V33) and a 1000uF capacitor.

simulate this circuit – Schematic created using CircuitLab
The voltage divider uses two 10k resistors. On the multimeter, the values look ok (3.3V and 1.65V,) but on a DSO (a Nano DSO,) I get this for the Vcc and Vcc/2 :

Vcc
Vcc/2

It seems very noisy, and I can't see why; everything else is disconnected. I don't expect the value to be mathematically Vcc/2 due to tolerance, and probably the DSO itself is a bit crappy, but:

Why is this happening?
What can I do about it?
Could this have a significant impact on the comparators, or I'm worrying for nothing?


texts: What connector type is this 3-pin connector from an HP printer power adapter?

texts:
I have this HP 0950-4404 AC Power Adapter, from a discarded printer, that I want to re-purpose. I'd rather keep the connector intact and buy a jack that it fits. I can't find anything online about it. It looks like a Molex connector of some kind with the usual pins and sockets. Does anyone know what this is?

7 http://s1.postimg.org/475a7x8kt/IMG_2471_cr_rotated_annotated_2.jpg


texts: ERROR:Xst:827, Signal next_states1 cannot be synthesized, bad synchronous description

texts:
it shows

  ERROR:Xst:827 - "C:/Users/namec/Desktop/Class/VHDL/Traffic_Light/Traffic_light.vhd" line 46: Signal next_states1 cannot be synthesized, bad synchronous description. The description style you are using to describe a synchronous element (register, memory, etc.) is not supported in the current software release.

Highway: process(CLk)
    variable counter: integer := 0;
begin
    case traffic_states1 is
        when H0 =>
            if (Input='0' and rising_edge(clk)) then
                next_states1 <= H0;
                counter := counter + 1;
            elsif (counter <=20) and rising_edge(clk) then
                next_states1 <= H0;
                counter := counter + 1;
            elsif Input='1' and rising_edge(clk) and (counter >20) then
                next_states1 <= H1;
                counter := 0;
                -- else next_states1 <= traffic_states1;
            end if;
        when H1 =>
            if counter = 3 and rising_edge(clk) then
                next_states1 <= H2;
                counter := 0;
            else
                next_states1 <= H1;
                counter := counter + 1;
            end if;
        when H2 =>
            if rising_edge(clk) and counter = 9 then
                next_states1 <= H0;
                counter := 0;
            else
                next_states1 <= H2;
                counter := counter + 1;
            end if;
        when others =>
            null;


texts:
So, if a resistor, inductor and capacitor in series sum algebraically, how do they work in parallel?

Is it \$\dfrac{1}{\dfrac{1}{R}+\dfrac{1}{\dfrac{1}{L}+\dfrac{1}{C}}}\$ ?

Many thanks in advance

Joe


texts: Are both ground pins on the ATMEGA internally connected?

texts:
I think the title is self-explanatory but should I make the connection on PCB or they are already connected? If so, should I still connect them externally? Why?
I'm working on ATMEGA328p-pu if it matters.

(source: instructables.com)


texts: Can a low amps 48v battery handle big DC motor

texts:
I have a 48V DC motor, 3500W at 300A, combined with a dc controller with 60A constant and 120A peak discharge rate.

Can a 48v li-ion battery with 20A constant and 40A peak discharge rate, safely drive the dc motor?

Will the battery be damaged by a dc motor that will draw more current than the battery can give, or will the dc motor run at a reduced (proportional) power/torque, given by the battery's capabilities and the battery remain intact and safe?

The DC controller has current limiter protection at 120A fixed.


texts:
Most small LiPo batteries from any online retailer normally ship with a built-in over-voltage protection IC between the battery leads. I'm working on a single cell LiPo charger circuit and I wondered if I could just integrate that same protection circuit onto the charger PCB in case the end user attaches a battery that doesn't have one installed.

My questions are:

1) If the user's battery has the protection IC already installed and then attaches it to the PCB with its own protection IC, would having the two safeguards be redundant or interfere with each other in any way?

2) Is it a bad design practice to have this kind of a backup system if most batteries already have over-voltage protection built-in?

I couldn't find if anyone asked any similar questions before. If someone has asked before, please link them. Thanks!


texts: Falling and reflected impulse waveform - short circuit and void

texts: What causes the signals to reflect differently when \$Z_L\$ = ∞ and when \$Z_L\$ = 0?


texts: Is there a free cross-platform tool for pure digital gate-level schematic design and simulation?

texts:
I'm searching a software tool for teaching purpose in order to teach students digital hardware (starting from logic gates level).

Do you have something in mind that will allow making simple graphical schematics and simulate them?

In best case it should be free (or at least with time-unlimited demo) and run on Windows, Linux and Mac OS.

If it could simulate VHDL or any other HDL it would be a plus.


texts: Voltage regulator getting hot after relay is switched on. Then uController burned after one day of testing

texts:
The circuit below aims at switching the relay according to user need while interacting with the display and push buttons.
Everything is fine before the relay switches on. But after the relay switched on, the voltage regulator gets very hot. After that, when the program switches the relay off it cools down and everything is fine again.

I thought at the beginnig that I just have to add a heatsink, and went through this question

I measured the current consumption: total current is around: 150 mA.
95mA for Relay. 15mA for the buzzer. 40mA for the Arduino and the rest of the circuit.

After one day of testing, the uController (Arduino nano) burned!
What could be the source of the problem and how to solve it?

Components used
Arduino nano.
Optocoupler CNY17.
Pololu 5VDC Relay Board.
128X32 0.96" OLED display.
Voltage regulator 7805.
voltage Source: Wall adapter, 12V 1A.
Electromagnetic Buzzer.
BS170Small Signal MOSFET.

Notes:
* the relay Module has a freewheeling diode.
* I can't use two voltage sources for this application


texts: DIAC datasheet's circuit is not in series with TRIAC's Gate

texts:
Being my first time to use a Triac and a Diac to control an AC signal, I read many questions/answers in this forum related to DIACs controlling TRIACs, all being very helpful.
Now, I see in a MOC302 DIAC's datasheet page 8, something that I dont understand:

Won't the Triac conduct if the R1 is low enough? I do not understand the reason to use R1 there, it should be an open circuit in R1, so that the DIAC could be in series with Triac's Gate.
And I saw the same conficuration at this question:

But no one commented why his R6 is there.
EDIT:
Regarding mainly @Spehro Pefhany's answer, since the R1 makes the Base less sensitive,
I guess R1 has to be high enough so that It wont cause the Triac to conduct when the photo Diac is off and AC voltage is on this stage:

So if Triac conducts at Holding current= 20mA, we need the Resistor to be at least (more than) R=100/0.002=50kOhms, Right?
(As long as the voltage on its gate does not exceed (lets say) 1.3V where it conducts, the 50Kohms will do the job, but still, I do not know how to calculate if the Voltage at the gate will surpass 1.3V on the above schematic with R1=50K)


texts: Implementing a mains appliance into a PCB

texts:
For a college project I am implementing heat via the use of one of those heat-pads you can get for lizards. The problem is the heater is direct to the mains.

Am I being dumb or is there a way to allow mains electricity into a PCB to then power the mat directly from the PCB? I am using an IC chip to control the mat.

The mat is 8w at 240v AC

I'm just struggling to work out how to implement the mat into the PCB as I have no idea if its possible wiring earth, live and neutral into a PCB.

Many thanks


texts: Why use a ten-percent rule-of-thumb for a bleeder current on a voltage divider?

texts:
A book I am reading recommends "The 10 Percent Rule" as a method for selecting resistors for a voltage divider:

The book claims it is a standard method. My question is: why choose a bleeder current that is ten percent the load current? Why not less? It seems to me that a smaller bleeder current would be more efficient: less bleeder current would result in less power consumption by the bleeder resistor (P=IV, I decrease) and the first resistor (the current in the first resistor is the sum of the currents through the bleeder and the load. The bleeder current decreases while the load current stays the same, so overall current also decreases)


texts: Help with understanding the Memory Map of MLX90393

texts:
(Using a Raspberry Pi 3 Model B+ and python)

I needed some assistance in understanding the memory map of MLX90393
I've attached the memory map here and you could also find it in the datasheet.

I'm a newbie especially for data processing. The information provided in the datasheet is a problem to me. I've spent last 7 days trying to understand it with nothing solid to work with. The sample code from the product page works very well and gives intended output. So far I've been just able to change just GAIN_SEL property because it's already in the sample code and has a variable for it to be changed and done a lot of trial and errors with non-sensible output. I know Bitwise conversions and I've worked with them before but I can't understand how exactly the host specifies the address register and the values for it in reference to the memory map. I've gone through all of the tutorials on Sparkfun and Adafruit and some other websites to understand I2C again. I know how I2C works about sending bytes and waiting for the responses and then reading data blocks but I simply don't know how to configure the sensor.
(For example, how am I supposed to set DIG_FILT (digital property)?, How do I start it in burst mode?)

It really seems like a stupid question to me as well but I just don't know what I'm doing wrong.

If you guys can help me understand it or point me to link which will be useful that'll be great!

Here is the sample code for your reference :

# Distributed with a free-will license.
# Use it any way you want, profit or free, provided it fits in the licenses of its associated works.
# MLX90393
# This code is designed to work with the MLX90393_I2CS I2C Mini Module available from ControlEverything.com.
# https://www.controleverything.com/products

import smbus
import time

# Get I2C bus
bus = smbus.SMBus(1)

while True:
    # MLX90393 address, 0x0C(12)
    # Select write register command, 0x60(96)
    # AH = 0x00, AL = 0x5C, GAIN_SEL = 5, Address register (0x00 << 2)
    config = [0x00, 0x5C, 0x07]
    bus.write_i2c_block_data(0x0C, 0x60, config)

    # Read data back, 1 byte
    # Status byte
    data = bus.read_byte(0x0C)

    # MLX90393 address, 0x0C(12)
    # Select write register command, 0x60(96)
    # AH = 0x02, AL = 0xB4, RES for magnetic measurement = 0, Address register (0x02 << 2)
    config = [0x02, 0xB4, 0x08]
    bus.write_i2c_block_data(0x0C, 0x60, config)

    # Read data back, 1 byte
    # Status byte
    data = bus.read_byte(0x0C)
    #FROM HERE
    # MLX90393 address, 0x0C(12)
    # Start single meaurement mode, X, Y, Z-Axis enabled
    bus.write_byte(0x0C, 0x3E)

    # Read data back, 1 byte
    # Status byte
    data = bus.read_byte(0x0C)

    time.sleep(0.096)

    # MLX90393 address, 0x0C(12)
    # Read data back from 0x4E(78), 7 bytes
    # Status, xMag msb, xMag lsb, yMag msb, yMag lsb, zMag msb, zMag lsb
    data = bus.read_i2c_block_data(0x0C, 0x4E, 7)

    # Convert the data
    xMag = data[1] * 256 + data[2]
    # if xMag > 32767 :
    #   xMag -= 65536

    yMag = data[3] * 256 + data[4]
    # if yMag > 32767 :
    #   yMag -= 65536

    zMag = data[5] * 256 + data[6]
    # if zMag > 32767 :
    #   zMag -= 65536

    # Output data to screen
    print "Magnetic Field in X-Axis : %d" %xMag
    print "Magnetic Field in Y-Axis : %d" %yMag
    print "Magnetic Field in Z-Axis : %d" %zMag


texts: Transimpedance amplifier calculating feedback capacitor

texts:
What is the correct way to calculate \$C_F\$ of the transimpedance amplifier? Since I have two different documents,  each has a different way to calculate it.

Base on these two documents:
1. Maxim
2. TI

On the first link Maxim, \$C_F\$ calculate by this equation where \$f_{GBWP}\$  is 60% of unity gain bandwidth of opamp.

On the second link \$C_F<< 1/(2\pi R_ff_P)\$ for pole frequency, fp


texts: Capacitor stitching for high speed differential pairs

texts:
This is the first time I have designed a 4 layer board and the reading I have done says to use stitching vias for the differential pairs due to the stackup I am using.
The stackup is as follows
SIGNALS+COMPONENTS
GROUND
POWER
SIGNALS
I have pasted an image that I used for reference when designing my board.
For context the board I am laying out is for a Raspberry Pi compute module 3 IO board.
It is a section of pins from the SODIMM connector with traces going to a DSI display connector.
I am wondering if I really need 2 capacitors for each side of a pair or can I just put single capacitors between the pairs due to space limitations (as I have it laid out now).  Also should I be getting the vias from the caps a little closer to the signal vias?
The capacitors are all 0402 size with 100nF value (X7R 10%).
Thanks in advance!


texts:
I just started to learn FREERTOS with atmel studio.
At first, I tried to make the most simple code "toggling LED".
I can build solution of the code, but when I try to debug my code, it stops at disassembly file every time.
What is wrong with my code? I think this code can't enter the main function also.
I used 'ATSAMD21G18A' in 'MKR1300'
I stop this part in assembly code.
00001B68   push {r0, r1, r2, r4, r5, r6, r7, lr}
#include <asf.h>
#include <FreeRTOSConfig.h>
#include <FreeRTOS.h>
#include <task.h>
#include <io.h>

#define LED0 IOPORT_CREATE_PIN(IOPORT_PORTA, 20)
#define LED0_ACTIVE 1
#define LED0_INACTIVE 0

void vLED_ON(void *pvParameters)
{
    const TickType_t xDelay = pdMS_TO_TICKS(500);
    ioport_set_pin_dir(LED0,IOPORT_DIR_OUTPUT);

while(1)
    {
        ioport_set_pin_level(LED0,LED0_ACTIVE);
        vTaskDelay(xDelay);

    }
}

void vLED_OFF(void *pvParameters)
{
    const TickType_t xDelay = pdMS_TO_TICKS(500);

    while(1)
    {
        ioport_set_pin_level(LED0,!LED0_ACTIVE);
        vTaskDelay(xDelay);

    }
}

int main(void)
{
    system_init();
    system_clock_init();
    ioport_init();

    // RTOS start
    xTaskCreate(vLED_ON, "LED_ON",128,NULL,1,NULL);
    xTaskCreate(vLED_OFF, "LED_OFF",128,NULL,2,NULL);
    vTaskStartScheduler();
    while(1);
}

void vApplicationMallocFailedHook()
{
    while(1);
}

void vApplicationStackOverflowHook()
{
    while(1);
}
```


texts: If a large AC generator is overloaded, will it lose frequency or voltage?

texts:
If a large AC synchronous generator, like one from a hydro dam, were to receive overdemand from the grid, would it start losing frequency or losing voltage?

I know they have several safeguards to keep this from happening, but if these safe guards were not in place, what would be expected to happen?

Edit: Supposing there is only this generator in the whole grid.


texts: Control 12 solenoids with a raspberry pi

texts:
I'm a musician and I'm working on a funny project : control solenoids with a midi keyboard.

So I have a MIDI keyboard connected to my raspberry pi connected to my breadboard. Until now everything is working correctly with 12 LEDs, every time I press a key, a different LED is turned on.

Where I'm stuck, mainly because I lack of electronic and electricity education, is where it come to control the solenoids, I don't really know how to power them, and how to prevent the raspberry from frying.

I've planned to use 12v solenoids using 1.4A

Here is what came out of my researches on the internet. Please warn me, correct me, (help me) if something is wrong...

When a pin on the raspberry is turned on, it's delivering 3,3v power.
The pin should be connected to a resistance (1k), then to a LED (for witness), then to a transistor (TIP120 ?).
The "ground leg" of the transistor should be connected to the ground of the raspberry and the ground of the power supply without any resistance or diode. (I'm really in doubt of that, afraid of frying the raspberry...) .
The 12v power supply (+) should be connected to the solenoid (+).
The solenoid (-) should be connected to the middle leg of the transistor (the one activated when it receive the 3,3v from the pin) and also to a diode (1N4004 ?). That diode should be connected to the + of the power supply.

Is that correct ?

Questions :

What to use as power supply ?
Can I use batteries ? one for each solenoid ?
Any idea for supply all the solenoids at once ?

I hope I was clear, thanks you very much for your time and answers :)


texts: Testing regulated power supply: 100 mA current sink

texts:
Disclaimer: I'm trying to learn about circuits on my own.  I'm reading as much as possible to avoid any basic mistakes, but if there's any, please point it out and I'll investigate further in that direction!  Sometimes the problem is not lack of interest, but not knowing what you don't know (if that makes any sense). :-)

I want to build an Ammeter circuit to measure currents with an Arduino.  But before I do that, I was planning to build my own current sink, in order to be able to connect it to my regulated power source and be able to draw currents to verify the measurements.

Since I have many LM358Ns, I figured I could try to reproduce the "High Compliance Current Sink" from page 18 in this datasheet.

The maximum current that I want to sink is 100mA.

I've designed a prototype and simulated connecting a 5V power source:

The current values in Cload1 and 2 seem to be perfectly aligned with the voltage in Vreg1 and 2.

I have a few questions though:

I've split the circuit in two different LM358Ns because I believe the 2n2222s are dissipating 250mW each (5V, 0.05A).  Is this correct?
Is it ok to use a single POT like I'm using for both LM358Ns?

And last but not least: let me know if there's any improvement, or anything else that's obviously wrong with either the theory or my implementation of it!

Thanks!


texts:
I have just picked up the TLC5940 chip from TI that provides 16 PWM outputs.

The data sheet is here.

As mentioned in the data sheet, the max current at each output can be set by connecting a corresponding external resistor at the Iref pin.

What I am not sure about is the wattage rating of the this resistor. Does it depend on the current being sunk by the chip (higher the current the beefier this resistor needs to be)?

Looking at the power dissipation equation in the datasheet, there's no dependence on this resistor mentioned but I would like to be sure.

Thanks!


texts: Ethernet Data Transfer (ARM M3-Cortex to PC)

texts:
I am having some trouble trying to understand how I can use Ethernet to transmit some data to a computer.
To be clear this would be a direct connection (an Ethernet cable will run from my development board to a usb-c connection on my laptop via an Ethernet to usb-c adapter). I have seen many tutorials talking about getting an Arduino to communicate to a PC over ethernet via a server, but I don't think this is what I would be looking for since this is a direct connection to my laptop.
Currently I have some code that transmitting "Hello" from my development board, but I'm not sure where it is going (or if it is even sending at all). Is there anyway I could ping the device from my laptop? Really could use any advice/help on how to make this communication work.
I apologize if this question is vague or lacking information, I am just getting into Ethernet so there is a lot I don't quite know yet. I can provide clarification as needed.
The Development board I am using is a M2S150 FPGA Dev board that has a ARM Cortex M3 On-board


texts:
I am working on a project and have encountered a problem with one of my modules.
I am trying to add offsets to 11 bits input from another model and output them to vga controller.
My inputs are declared like so -
input   logic signed  Player_TLX [10:0],     //Current Player Top Left X pos
input   logic signed  Player_TLY [10:0],    //Current Player Top Left Y pos

and the calculation I am trying to do are -
            if (Fire && !In_Air) begin //Projectile Launch
                    topLeftY_FixedPoint <= (Player_TLY + Player_Height)*FIXED_POINT_MULTIPLIER ;
                    topLeftX_FixedPoint <= Player_TLX + Player_Half_Width ;
                    In_Air <= TRUE ;
                    Enemy_Hit <= FALSE;
            end

Where player height, width and the multiplier are constants.
This lines give me the error -
Error (10686): SystemVerilog error at Projectile_moveCollision.sv(65): Player_TLY has an aggregate value
Error (10686): SystemVerilog error at Projectile_moveCollision.sv(66): Player_TLX has an aggregate value

I have tried using local parameters for the calculations but got similar error ,
is there a way to make such calculations?
am I using the wrong data type for this?
help would be appreciated.


texts: ADC preamp using Schmitt trigger, opamps and transistor reset

texts:
I would like to validate this design I use for input to a microcontroller for a piezo microphone trigger. I use 3 lines: a Schmitt trigger for use with an interrupt, an analog line for measuring the voltage level in the ADC, a reset line connected to a transistor to discharge the ADC capacitor.

The first path going from L1 (ferrite bead) to Q1 rectifies and RC filters the the AC signal comming from the mic piezo.
The result is then split to both op amps U1 and U3.

I have a couple of questions regarding this design:

Do I need R2 and R3 to stabilize the input of U3 and U1?
Does it makes sense to control Q1 with a microcontroller to discharge the
C1 capacitor after the reading was done the the ADCInput line in the
micro?
Is it overkill to put a ESD protection TVS diode at the
very start of the signal chain?

Here are the signals I expect from LTSpice:

Red = Piezo signal (-5v/+5v)

Green = D2, C1, R1 filtering result before going to the opamps.

Blue = Schmitt trigger ouput

Any other comments/suggestions/links would be greatly appreaciated.


texts:
I want to measure a very low temperature (<-50C) with an NTC thermistor, but the error in my system is dominated by my ADC frontend characteristics due to the high resistance of the thermistor (>500k). Are there any downsides to putting two NTC thermistors in parallel next to each other? Assuming that they are very close, and thermally bonded, it seems like this would decrease the resistance measurement error of my system, and not really increase the resistance error of the NTC readings at that temperature?
It seems like you could do the same thing for high temperatures, with NTCs in series?
Obviously both of these approaches have downsides in the other end of the scale (parallel is bad for high temp, series is bad for low temp). Its also possible to get thermistors with lower resistances for the low end range, although they seem to be in short supply.


texts:
Can anyone confirm the correctness of D27, D28 diode polarities or should they be in opposite direction?
Please suggest an which diode is suitable for this purpose OR is it better to use a zener diode in place of simple diode?
Also what is the purpose of C69 capacitor and what will be its appropriate value?

edit: picture added now.


texts:
A problem in my textbook gives this task:

A solution is given as:

I tried to work this problem using a different method. I simply calculated the areas of the triangles as if the height of the triangles was A^2. This gives me this result:

I was confused by why these answers should be different. I rearranged the first integral from the given solution into 1/2 * base * height form to see what triangle they are using. It's this:

In other words, if they calculated it with triangles, the base of each triangle is squared as well. Why should the base of the triangle be different? Shouldn't the value of the function simply be squared for each point in time?


texts: PIR sensor (HC-SR501) with n-Mosfet transistor not switching off

texts:
I have none to less electronics background, with limited knowledge whatsoever. I've used some schematics from the internet https://www.youtube.com/watch?v=ugDPdgGekNo to put in place the below setup :

A PIR sensor (HC-SR501) + n-Mosfet transistor irfz24n + 9v battery to power on a 9v led light bulb.
The problem is that with this setup, the led light bulb doesn't turn off when no motion is detected, it remains opened.
I have measured aside the PIR sensor outputs: it's 3.6V when some motion is detected and when no motion is detected it drops to 0v.
Any advice on what is wrong is appreciated.


texts: Polling several buttons from an interrupt

texts:
I am trying to poll 3 different buttons from a watchdog time out interrupt, on an ATtiny13.

My code works perfectly for individual buttons, however I can't seem to be able to poll all 3 in a loop.
All buttons are associated to an arbitrary number for identification in 0x01,0x02 and 0x04.

For example, this code polls the button 0x02 and works fine:

ISR (WDT_vect){
if (debounce(0x02)==1){
    PORTB ^= _BV(PB1);//flip led 1
}}

However, if I try to poll all 3 in a loop, no detection seems to occur. In this example I simply toggle the same led for all 3 buttons:

ISR (WDT_vect){
    for (int d=0x01;d<0x04;d<<1){
    if (debounce(d)==1){
        PORTB ^= _BV(PB1);//flip led 1
    }}}

Stacked if-else don't work either:

ISR (WDT_vect){

if (debounce(0x02)==1){
    PORTB ^= _BV(PB1);//flip led 1
} else  if (debounce(0x04)==1){
    PORTB ^= _BV(PB3);//flip led 2
}
}

The rest of the relevant code shortened for clarity:

/***
 * curbtn: one of 0x01,0x02,0x04, matches mute, vol+,vol-
 * returns 1 if the button is considered pressed
 */
uint8_t debounce(uint8_t  curbtn){
static uint8_t button_history = 0;
uint8_t pressed = 0;
button_history = button_history << 1;
button_history |= read_btn(curbtn);
if ((button_history & 0b11000111) == 0b00000111) {
    pressed = 1;
    button_history = 0b11111111;
}
return pressed;
}
/**
 * sets up ports to read a specific button
 * returns 1 if the selected button is pressed
 */
uint8_t read_btn(uint8_t  curbtn){
uint8_t ret=0x00;
if (curbtn==0x01){
    DDRB &=~_BV(PB2);//PB2 en entree
    PORTB |=_BV(PB2);//pull-up actif
    ret= ( (PINB & _BV(PB2)) == 0 );
} else if (curbtn==0x02){
    DDRB |=_BV(PB2);//PB2 en sortie
    PORTB &=~_BV(PB2);//PB2 a 0
    DDRB &=~_BV(PB0);//PB0 en entree
    PORTB |=_BV(PB0);//pull up sur PB0
    ret= ( (PINB & _BV(PB0)) == 0 );
} else if (curbtn==0x04){
    DDRB |=_BV(PB0);//PB0 en sortie
    PORTB &=~_BV(PB0);//PB0 a 0
    DDRB &=~_BV(PB4);//PB4 en entree
    PORTB |=_BV(PB4);//pull up sur PB4
    ret= ((PINB & (1<<PB4)) == 0);//lecture de PB0
}
return ret;
}

This is the circuit layout:

I'd like to know if I'm going in the right direction, and in what way my polling code should be corrected.


texts:
The communications channel between a QPSK transmitter and receiver can introduce an arbitrary phase change. For this reason, differential QPSK is used.

Differential QPSK seeks to solve the phase ambiguity problem by encoding data using changes in phase between data points, as opposed to their absolute phase. However, now I have a question:

What kind of circuit can measure phase between two signals at different points in time?

On page 2 of this pdf a demodulator is shown, using a delay element. But in the analog world, how do you build such a delay element?


texts: Do MRI magnets oscillate due to parasitic capacitance?

texts:
Moved here from SE Physics.

Do MRI magnets oscillate during charging or even during persistant mode due to parasitic capacitance? What problems can this cause?

I am planning a low temp superconducting toroid inductor with multiple layers operating in persistent mode under liquid Helium. I am considering if I have to plan for a serious a problem with LC oscillation due to parasitic capacitance between layers.

I can imagine that this may cause quench problems, problems with heat causing Helium boil off etc.

Do MRI magnets, superconducting magnets in general experience an electrically quiet ramp up, or does oscillation have to be mitigated. I've never read that there is a problem, but a physicist friend with some experience with DC circuits mentioned the possibility. I know that there will be parasitic capacitance and so it seems reasonable that all such equipment would have that problem.


texts:
I use proteus to debug the operation of the PICs.

Now I am going to use a dsPIC33EP128GP502 and in Proteus libraries it does not appear.

I have searched if there is any library of this type of PIC but I have not found anything.

Does anyone know how I can add these dsPIC to proteus?


texts: Output voltage of NPC1403 boost converter circuit 0 during simluation

texts: Currently, for my needs I'm trying to boost a 5v input to 15v with a minimum of 20ma current at the output. I found the NPC1403 to require my needs however, when i'm trying to simulate using EasyEDA my output voltage is constantly 0. I'm currently doing a transient analysis with 1s steps and a maximum time of 100s. I feel like there is a minor issue that i'm messing up but have been unable to figure out what. The current circuit setup can be seen below.


texts: How to quickly switch power to a LED strip?

texts:
I need to switch a three sets 8 LEDs (1.2V each) in series with a current limiting resistor (~100mA) powered from 15V in under 500ns, about 2000 times per second, separately. The signal will be 3.3V, and at most 20mA.
I considered using a MOSFETs with a driver but that seems really overcomplicated. What would be the best solution?


texts:
I have multiple devices that need a DIO connection with 8 wires back to a central device. Would using an Ethernet cable for this purpose be reliable, or would using something like DB9 connectors be better?

I was thinking that because of the twisted pairs that using two separate signals on a pair may cause interference, but I don't know if it would.


texts: What does the term 10GA CT-PT means for a CT-PT wiring?

texts: We have a MCC in our garage of commercial outlet facility. The bucket with the metering unit needs to be configured with the GE-PQM 2 (Power Quality Meter),and CTs and PTs are required to provide the signal to current and voltage inputs to the meter respectively. However, the specification for the bucket mentions, "the CT & PT wiring should be 10 GA". What does the term GA means ?


texts: How calculate standard deviation of ADC histogram for rms noise analysis?

texts:
Some papers from Analog Devices (like this one - page 2) and other sources indicates that the rms noise of a histogram plot of an ADC output can be found by calculating the standard deviation of the distribution. So, the standard deviation is in fact the rms noise.

I'm trying to calculate the standard deviation using an online calculator (to speed up calc) for some histograms in the same application note but the values that I get are always wrong from the application note, so it's clear that I'm totally lost here.

Can anyone help me to calculate the rms noise of a given ADC histogram considering that I have the ADC values x number of ocurrences of each value?


texts:
I need to replace two LED diodes on a TP4056 board (bottom right corner on the picture).

The board is going to be in a box and I want to move diodes to the small holes in the box.

There are two resistors with marks 102, and that is 1 kilohm. I measured voltage on diodes and my multi-meter said 2.7 V.

I want to use something like this:

Those diodes are 3 V 20 mAh. Can they replace exiting diodes?

update:

Thank you guys. You helped me a lot.

Btw, current LEDs are blue and red


texts: Running 220v and 110v power supply on same computer

texts: I'm trying to run a 13 card Ethereum mining server and I have dual 1,600W PSUs on 220V but it's not powerful enough for the 13 R9 290s that run @ 300W a piece, totaling 3,600W in power. I have a spare 700W PSU that runs on 110V, so I was wondering if I could connect the cards to that PSU to get it all running.


texts: How to bias BJT using Widlar current source?

texts:
Here is Widlar Current source driving load:

It gives almost constant current for wide range of load resistances:

Here is one circuit involving BJT:

You can see it is biased using one voltage and one current source.
My question is, how I can use Widlar current source to bias this circuit?
I mean, how should I connect it?


texts: What's the point of a MOSFET in a synchronous buck converter?

texts:
I can't seem to understand the point of the second MOSFET in a synchronous buck converter. The second (Q2) MOSFET has a body diode which seems to act like a normal diode in an asynchronous buck converter and when the MOSFET is conducting there is no inductor current flowing through the MOSFET, just through the diode to my understanding.
By the way the following image is not my circuit, it's just an example.


texts:
I have a device that I am pre testing to find possible issues with unintentional rf radation.  The processor is a pic32 running at 80MHz, and is connected to a ti dp83848 ethernet phy in mii mode using a 25MHz crystal.

I see peaks at 75MHz, 150, and 175.  I am a little unclear where these harmonics could be originating.  Could I get this activity from a 25MHz crystal, all the way up to 175?  The peaks are pretty much spot on, at least according to the rigol dsa815.

Addition:  I have done more testing here, I see most of these harmonics are generated in the phy area, and between the phy and jack.  I have some traces that run in an internal layer that go through that area and come out right at the indicator switch legs, and they are picking up these harmonics.  Its a little unclear to me whether or not these are over the limit, I may just have to test and see.  My understanding is that near field probes pick up a signal whether or not there is an unintentional antenna or slot big enough to pass the signal.  I suspect most ethernet devices have some harmonics in this range.  The pic32 ethernet starter has similar results.

I may have just have to pay the test house for this education.


texts: How can thermal electrical noise be uncorrelated yet appearing at a certain frequency?

texts:
Say we look at the thermal noise spectrum of an ideal resistor. Now we know it will behave like  $$ \langle U^2 \rangle = 4 \, k_B \, T  \,R \,\Delta f $$

We also know that two subsequent voltages are uncorrelated:
$$
\langle U(t) U(t+\tau)\rangle = c\, \delta(\tau)
$$
where c is a proportional constant.

Now my question is: How are these two relations compatible with each other? Phrased in words of the experimentalist, what causes a certain \$ U^2 \$ to appear at frequency bin \$f\$? Shouldn't it have some component \$ ~\propto e^{iwt} \$?


texts: Doubt with the conversion from output PID signal to PWM on inverted pendulum control problem

texts:
I am working on the design of a PID controller to control an inverted pendulum. The last days i got stuck in trying to understand the relationship between the PID's output, and how can relate it with the PWM signal (or percentage).
At first i supposed that it is necessary to measure the force that is generated by every percentage of PWM, so i can get a linear relation between both values. But then, looking for information on the internet and papers, i found that some of that papers say that the PID's output is the PWM signal, and the conversion is a scalling of the control signal in order to map it to a interval that the microcontroller can understand.
So, my question is, which of them is the correct answer?


texts: I am running 12 x led strips controlled by a 0-10v dimmable controller however the led strips are 12v dc and are not operating at their full output at 10v.  How can I amplify the 0-10v output to produce a 0-12v output to get the full brightness out of the leds?  When I connect the strips to a 12v dc source they operate perfectly but I need to use the programmable 0-10v dimmer to control them.


texts: Choosing proper stepper motor, motor driver and power supply combination

texts:
I need to run 15 stepper motor simultaneously with different duty cycles for a mechanical study. However as a mechanical engineer my knowledge on the electronics is not much more than none. Could you please guide me how I should approach this problem?
Stepper motor:
According to my estimations stepper motors called 17HS4401 will work for me. The link below shows the datasheet for these motors. It has a rated voltage of 3.6 V and a rated current of 1.5A/phase
https://m.media-amazon.com/images/I/71ZPjYkgxwL.jpg
Motor Driver
I am planning to use one driver for each of the stepper motors as each of them will rotate in independent and variable speeds. The one I am planning to use is A4988. The datasheet is available in the link below. It says it has a maximum current of 2A.
https://www.pololu.com/file/0J450/a4988_DMOS_microstepping_driver_with_translator.pdf
Power Supply
I haven't decided on the power supply yet.
My questions:

I am planning to feed the motor driver with a 12V supply. Will the motor driver be sufficient for the stepper motor I will use? (I don't know how much current the stepper motors can draw at max with this voltage, that's why I cannot make sure)

Generally for this motor driver it is suggested to use an electrolytic capacitor between VMOT and GND. They say if it is not done spikes can be a problem. Does it mean that it will damage the driver or can it have other impacts? And does it have to be an an electrolytic one? The electrolytic ones I was able to find was SMD and I don't know how to fit them.

I have found a CNC shield for Arduino Uno. But the shield has sockets for only 4 drivers. It seems that I will need to run 4 Aurdinos at the same time. Do I have any other option? If not is it possible to run 4 of them properly (as my laptop does not have 4 different USB ports I will need to use a splitter)?

I am planning to use a 12V  power supply. How much total current should I expect at max? I need to choose the current capacity of the power supply.


texts: Selection of filters (common mode and differential mode)

texts:
I am designing a flyback converter that works at an operational frequency of 100kHz. Now, I need 2 levels of filtering at the input phase viz - common mode filter and differential mode filter. The common mode filtering is done using a common mode choke while the differential mode filtering is done using a pi filter composed of ferrite bead and capacitors. The current requirement is about 3Amps.

Now, my doubt pertains to the selection of these filters. For the common mode choke I went through the datasheets of different chokes that had decent impedance at the frequency of 100kHz. Likewise for ferrite beads.

But most of the said filters show impedance curves at frequencies greater than 1MHz. So, how can I select one for 100kHz ? Or is my thought process wrong ?


texts:
I am ordering a graphic lcd NHD‐12864AZ‐FL‐YBW and most of the interface code seems pretty simple.  On the datasheet it has the following list of commands

I don't understand what is put in the write display data command to draw something to the screen.  For example, how would the pixel at (5, 8) be turned dark).  I looked through the datasheet but could not find anything.


texts: What IC should I use to make a binary clock?

texts:
I am wanting to make a binary clock.  A lot of the schematics I've found are for Arduinos or Raspberry Pi.  As much as I appreciate the use of minicontrollers, I don't want to do that for this project.

I don't want to to lean on any programming knowledge as my primary background is software.  Because I'm trying to learn digital electronics, I would like to know which integrated circuits should be used.

I have fiddled with the CMOS 4520 and a 555 to make a simple binary counter.  I just can't see
how a 4520 would be enough.

Being that a binary clock is a common project for beginners, I was hoping to see what you have used and in what fashion in order to accomplish this.


texts: Need a circuit to convert 230V sine wave into 5V square wave

texts:
We have already obtained our result using transformer for our college project ,but can't find circuit to convert 230V sine wave into 5V square wave which is supplied to microcontroller.

Edit:
Our team got this circuit from web,but not sure whether it can handle 230V main supply and generate 5V square wave.


texts: What is this component, and how can I use it?

texts:
Please see the attached photograph of the component:

My guess is that it is a solenoid, but I am not sure. If it is a solenoid, I would really like to use it. The problem, however, is that I do not know anything else about the component. There are no part/model numbers or any identification of any kind on the component.
In a situation like this, how do you go about putting a mysterious component to use. I generally don't throw away things simply because I don't know what they are, and am sure I could use this for something.


texts: Help making a adder/subtractor on Logisim

texts:
I have attempted to make an 4 bit Adder and Subtractor circuit on Logisim, but i've came across a problem. So the Adder works but the subtractor doesn't. When i do subtraction the 1 thats carried in is carried throughout the circuit. When i do 1000 - 1000 it gives me 10000.
How do i solve this?


texts: Visa payWave, MasterCard PayPass and ExpressPay, NFC and RFID

texts:
Since all those technologies use RFID contactless smart card and
EMV, are they compatible? Is contact-less Visa card compatible with the
Mastercard system?
Are the systems compatible with NFC? I.e. can the smartphone with NFC controller and antenna emulate e.g. Visa smart card either in SIM card or built-in secure element?


texts: How do I find the fourth order transfer function from this step response diagram?

texts:
I have the following diagram of a system's step response:

I'm having trouble understanding how to calculate the system's transfer function for fourth order.
hir: How do I find the second order transfer function from this step response diagram?
I have learned how to do it for the second but I do not know how to calculate this for the fourth order.


texts: Possible to Solder top of through-hole header?

texts:
I have designed a small 2-sided PCB with through-hole parts, which I plan to have fabbed professionally.  Given the lack of space (2"x2" was a design constraint to keep costs low, as I will need a number of these boards), I'm using my through-hole component pins/leads as vias in some cases.

Looking at the render (KiCad), I believe I will be able to solder all of the pins needed on the front of board with one possible exception- I have three 3-pin male headers on the board, which will be used with shunt jumpers.  A few of these pins have front-side copper connections and will require front-side soldering.  I'm concerned the the plastic spacer on the header will prevent me from soldering the pins on the front side of the board.

With some force, I can slide the spacer up and down the pins, so it occurred to me to:

solder the bottom of the header pins
slide the spacer up the header pins with small pliers
solder the top of the header pins
slide the spacer back down into place.

However, I'm concerned about the amount of physical stress this would put on the solder joints.  Is this a reasonable method?  Is there another method I should use?  Or is there an alternate component I should be using?

For reference, here's the render:

The three 3-pin vertical headers on the right side of the board are the components in question.


texts: battery voltage supply too high for electronics

texts:
I am driving brushless DC motors with an STM32 blue pill. My application includes said STM32 blue pill, L6234 motor drivers, 2 MPU5060 gyros and 2 AS5048a encoders.
I am using a 14.8V battery to feed the drivers. STM32, the gyros, and the encoders need to be fed with 5V.
My question is: what is my best (and perhaps easiest) option to feed the STM32 and the sensors?
So I was thinking about a buck (DC/DC) converter, but I am not sure how it is usually done. The STM32 and the sensors are low power, the motor drivers are high power.

Or is it possible to do such a thing with voltage regulators that can be found in Arduino Uno without them shutting down?


texts:
I have designed the attached power selector circuit, it has a 12V input and a 15V input, and should prioritize the later.

It operates in three different scenarios:

1- 12V source R76+R79 divider polarizes the Q25 BJT, driving the gate of the the Q9 P-MOS low, sucessfully generating -12V Vgs and opening the channel for current to pass. That way, I can switch this line without having the voltage drop on the intrinsic diode from Q9A.

2- 15V source R80+R84 divider acts in the same way as mode of operation #1, instead driving the gate of the MOSFET Q9B through BJT Q28.

3- Both Sources The 15V supply has priority, so when it is connected, it drives not only Q28, but also Q27 - This transistor brings the base of Q25 to GND, effectively bringing the Collector of Q25 to 12V, so that Q9A is not in conduction mode anymore.

What I'm observing, is that even when I'm in mode of operation #1, it seems that Q27 gets polarized in some way, as if the 15V supply were present. That closes the channel on Q9A and all the current supplied by the 12V source has to go through the intrinsic Diode, thus heating Q9A by a considerable ammount (we are talking in the 7 Amps figure here, so a diode drop is quite significant in terms of dissipated power).

I designed this circuit with the intention of having no diode drops, and have fallen exactly on that scenario...
The question is: Why is Q27 still driving the gate of Q25 to GND if I haven't fed the 15V input?


texts:
I apologize if this type of question doesn't belong here, but I recently completed a circuit diagram for an upcoming project, and realized upon review that I didn't include any resistors...  There didn't seem to be anywhere in the circuit that required resistors.

Here is the diagram in question:

Long story short, did I omit something obvious?


texts:
The bypass capacitor is seen on almost every amp out there but is it really necessary? As in many text book, it serve 2 purpose:
1. Act as short to ground at high frequency which shunt noise from other noise source that couple into the power supply through the power supply trace.
2. Act as a power source for fast transient current at high frequency.
But in reality, i see many amps connect the power supply directly to the V+ or V- leg of the opamp, if we want to maximize effect (1), it should be power supply -> bypass cap -> ic legs. So i think most of the time, the bypass cap is there to serve for purpose (2) but, here is the impedance plot of a 0.1uf x7r capacitor from kemet:

You can see that at audio frequency, the impedance of the capacitor is very high, so when a "high" frequency audio signal need to be produce by the amp, the current should flow from the power supply because it has much lower output impedance at audio frequency, not the capacitor. The capacitor is only good at 1->100Mhz which is far above audio frequency. So what is the real benefit of a by pass capacitor?

Edit: the bypass here is some 100nf or 1uf ceramic capacitor from V+ or V- of opamp to ground. I just want to disscus the benefit of bypass capacitor in audio application, especially with opamp as headphone amplifier. Here is my simulation which take account of trace impedance and inductance, the load is about 5cm from the power supply and is bypass by a 10uf 70mR esr tantalum and 1uf ceramic which is the bypass strategy often seen in headphone amplifier. The blue trace is without bypass and green trace is bypassed. As you can see, the bypass capacitor only has effect from 300khz which is far above audio frequency.


texts:
I have a superbright LED desk lamp that had a two-line power cable fed from a sealed AC-to-DC converter on an EU-style 2.5A two-prong plug that fed it 12V (unknown amp draw; not specified on converter). However, the cable wore through at the point where it emerged from the converter and is impossible to repair.
I attempted to use other converters that supply 12V, but the lamp flickers with them. I made a connector with a 220 microfarad cap on it to see if that would improve matters (which it didn't). Am I correct in my suspicions of the cause(s) of the flicker? These are that ...

the lamp requires more current than the converter supplies
the cap is too small to supply adequate smoothing/charge and/or is not the right component to solve this problem.
The black box "converter" has additional circuitry (which the others don't) that deals with the flicker issue and I should add this (what?) to my adaptor/connector.


texts:
I have been looking over multiple designs for ideal diodes using FET transistors such as the circuits from these posts:

PMOSFET Ideal Diode for 24V

Understanding an 'ideal' diode made from a p-channel MOSFET and PNP transistors

and from this site:

http://jiggerjuice.info/electronics/projects/power/ideal-diode.html

The part that I don't understand is why they use so many other components in their designs.  My question is if the following circuit I designed functions the same as the ones linked above.

simulate this circuit – Schematic created using CircuitLab

The zener diode is being used to protect the gate terminal on the FET.

edit: for use as a high side half wave rectifier:


texts: Is it a good habit to route wire under chip resistor/capacitor?

texts: Is it good/safe to route under resistor/capacitor? As below, it's a 0.5mm wire under a 1206 chip resistor.


texts:
I am trying to add an amplifier to a transceiver to increase the range but I am not sure how to add the reference schematics together (eg what components to remove, combine, etc).

The top schematic is for a RF switch design, so part of the circuit is to match to the 50ohms of the switch. By using that design with a 50ohms in-out amplifier I can reuse most of it without too much trouble. Basically the amplifier will go where the switch is on the schematic.

Here are the schematics with the corresponding values for each component and their description pulled from datasheets / reference designs.
Hopefully my unaesthetic illustration explains my problem clearly...

I suspect that C3 from the second circuit is redundant with C1 on the first and could be removed. Same for C1 (2nd) and C2 (1st). I think C9 (1st) and C7 (2nd) also serve the same purpose, but I'm not sure which value to keep. Finally I think C3 and C4 (1st) are equivalent to C2 (2nd) and so I could remove C2.

I don't know anything about RF, so all these guesses are just that. I am really looking for confirmation.

This is what the circuit would look like :


texts: Buck-boost converter dropping source voltage

texts:
I have two solar panels connected in series, and I'm using them to charge a phone. Together they provide about 7 V when I connect their leads to a multimeter or a basic circuit (i.e. Resistors/etc.). To regulate the voltage/current, I connected them to a step-down buck-boost converter.

The problem is that the output voltage of the solar panels drops significantly as soon as I connect them to the converter, from 7 V to about 1.5 V. This does not happen when I use a regular source (i.e. A laboratory voltage source - a machine).

I tried adding a diode/Zener diode to the solar panel to make sure the current is going in only one way, but that didn't work. Additionally, I tried to isolate the solar panels from the converter by connecting it to a voltage follower circuit or any IC, but that didn't work either.

I'm not sure why this voltage drop is occurring or how to prevent it from happening. Any help would be greatly appreciated.


texts: How to use a SN75441 h-bridge (not working as expected)

texts:
I am trying to figure out how to use an SN75441ONE h-bridge. I have it hooked up like this:

Pins 1, 8 and 16 are connected to the positive rail (+5 V). Pins 4, 5, 12 and 13 are connected to ground. Everything else is left alone. My expectation is that since all the input pins are LOW (here unconnected), the output pins should also be LOW. However, the output pins are all HIGH. What is going on here?


texts:
I recall at one point reading about embedded development where the programmer took into account things like memory corruption and possibly other hardware issues. For example:

If an instruction in memory is somehow corrupted, the program would run correctly anyway.
If the value of some variable in memory is changed, the program will still produce the correct result.

Dealing with #2 seems like a reasonable application of error correcting codes, but #1 seems to me like it would be very difficult. Does anyone know of any references or examples of someone doing that in software?


texts: How do the hybrid-pi models between N-channel and P-channel JFETs differ?

texts:
This is the hybrid-pi model of an n-channel JFET.

An answer on here claimed that the only difference between p-channel and n-channel JFETs is that voltages are reversed. How would this apply to the hybrid-pi model?

I would guess that the model would be identical to the one above except for changing the sign on \$v_{gs}\$, so that the source is positive, gate is negative, and current flows from source to drain. But I don't have sufficient understanding to know if this is correct. Is it?

If so, what about the h-parameter model for bipolar transistors? What would differ between N-channel and P-channel?


texts: DC-DC Converter Unusally Low Load Capability

texts:
I've been working on trying to get this SMPS to work for a while. I'm using an LTC1872, a step up DC controller with current limiting. The circuit used is the typical application provided in the datasheet:

With a couple of slight differences (since I'm not always able to get the correct parts):

Capacitor at pin 2 is 200pF
Output filter capacitors are a 100nF ceramic, 10uF electrolytic, and 2200uF electrolytic (scattergunning here a little)
Inductor is ~3uH (calculated from an LC circuit)

The good news is that the converter does seem to work. I input 3V and was easily able to generate 6V (with no load) out of it:

(2 volts/div)

However, when any sort of substantial load (<1kOhm), the output voltage rapidly drops - this is definitely undesirable since I need to be able to provide hundreds of milliamps to an amp for my project. When I used a 100R load, the waveform became this:

It appears to be pulsing towards target output voltage, but then abruptly terminating and thereafter switching off for the rest of the cycle (resulting in Vout = Vin). To me, this suggests that the current limiting is kicking in - the voltage is rising until the current gets too high, and then falls off as the converter stops boosting.

I've used a jumper cable for the sense resistor, but I have a feeling this has too high a resistance (compared to the one suggested). However, I've also tried shorting pins 5 and 4 with a piece of wire in between (the pins on the IC are less than a millimetre apart, so it's definitely going to be low resistance), and this doesn't seem to have too much of an effect. I'm not sure what else could be the problem. Perhaps the inductor saturating?

UPDATE

I've tried using a 45mOhm sense resistor (repurposed variable resistor) - doesn't seem to work. It's changing something, but I'm definitely not seeing an improvement.
I've also tried using two inductors in series, which should give me something like 6uH. Also no luck.


texts:
I need to use a shift register to control multiple leds, but I need to control each one individually. The idea would be to send a buffer with the data, however I need to have several active leds and just want to change the state of each one at a time.
For example: change state of led in PIN 1 of the PORTC to HIGH,
then the led in PORTC PIN 2 to HIGH, then the led in PORTC PIN 1 to LOW etc ...
Can someone give me and advice or some example code?
Thanks for listening


texts: Inverting video signal on op-amp on positive rail only

texts:
I wish to invert a video signal, keeping the signal positive.
Initially I believed the analogue signal would be 0v->5v, so I used the inverting input on an op-amp, and biased the non-inverting input to be approximately 2.5v. This worked well, but then I discovered that depending on the analogue source, the voltage range can be 0v->2v or 0v->3v.

This means that biasing the non-inverting input to a single voltage doesn't work. Can anyone think of a way to use an op-amp so that the signal can be inverted (180o phase, keeping it positive though), whilst retaining 0v base?

I have searched for similar questions, but they all seem to be based on people that have a fixed source signal range.

Many thanks!

I'm attempting to convert old CGA arcade Nintendo RGB signals that use untraditional inverted colours.  Each one of these colours is created from multiple TTL outputs (with different resistors), and through a transistor. Arcade monitors accept 1-5v p-p signals, but after measuring multiple sources they tend to be 0v to 2 or 3v max.

This means that on a standard monitor, black is displays as white and vice versa. Therefore, if we imagine that the signal goes from 0v to 2v, I need to invert that so that is goes from 2v to 0v to invert the colour.
The composite sync signal is negative (standard), and so doesn't need to be altered, and the sync signal is 15.75khz, so we're not talking about large bandwidths.


texts:
Information show that flash memory have a limited number of write cycles (usually ~10'000). Many MCUs emulate EEPROM in flash, hence some document this write_life_cycle.

A look at any MCU datasheet reveals something odd though - this flash memory is just a bank in the MCU memory unit. It shares the overall memory with "control and data REGISTERS" (see attached photo).

Hence my question: Suppose a program continuously writes to these registers (eg const ADC temp readings written to ADC1_DR), then this write_life_cycle may be exceeded in under a second. However, as we know MCUs outlive that by some margin.

I tried to assume that maybe, registers are implemented differently in HW, but then, why would their memory addresses overlap with the flash space and their widths be same?(a 32 bit bus can obviously access an 16 bit register -> case in point: all those reserved bits in some registers; might even reduce cost)

What have I got wrong in my understanding of how MCU memory works?


texts: How does this 4-transistor DC-DC 1.5V to 9V boost converter work?

texts:
While searching for DC-DC boost converters to replace 6F22 9V batteries by 2 NiMH rechargeable AAs for my cheap multimeters, I came across this circuit:

The circuit was posted by Popescu Marian at ElectroSchematics.com at the link below:

3V to 9V DC Boost Converters

Unfortunately, the circuit was posted without any explanation whatsoever.

As most boost converters, I imagine that this one works by using an oscillator (Q1 and Q2) in conjunction with the inductor (L1) to store and release energy with the right timing and regulates the output with help of D2 (the red LED), Q3 and Q4.

But I'm just guessing. I was hoping that someone could give me a more authoritative answer regarding the circuit workings.

My questions are:

How does this DC-DC boost converter work?
Do those transistor configurations have a name? What are they, so I can look them up and learn more about them?

I built the circuit on a breadboard, but I don't think it's working correctly yet. Using some inductor calculators out there, I figured that the inductor value is about 18uH. I replaced it with a 10uH 20% 2.5A PANASONIC (ELC09D100F) inductor (the closest value that I had handy - next up is 100uH). I've also replaced C1 with a 270pF ceramic capacitor.

When powering the circuit with a variable voltage power supply and no load, what I get is some sort of voltage amplification, according to the table below (approximate values from memory):

            +----------------+---------+
            |    Voltage     | Current |
            +----------------+---------+
            | input | output |  input  |
            +-------+--------+---------+
            |  1V   |   6V   |   50mA  |
            |  2V   |   8V   |  200mA  |
            |  3V   |  10V   |  450mA  |
            |  4V   |  12V   |  600mA  |
            +-------+--------+---------+

Well, that doesn't sound right, for two reasons:

The output is not regulating 9V;
The input current seems a bit excessive. It is almost all going through the inductor, which gets really hot to touch.

Can you tell what may be wrong with my breadboard circuit. If that's not enough detail for debugging, that's ok, I'll check it myself once I learn how the circuit works.


texts:
I am currently working on a project related that I asked before here. The purpose is to have 2ns rise time 30ns pulse width at 250V (with 50ohm load). Repetition is 30hz.
I tried avalanche transistor ZTX415 and I don't know why it didn't work. I will look at it another time. While I was searching, I saw this research. I am going to try a similar one but I am not sure how they done it. I have 1kV reed relays. But none of these relays are rated for nanoseconds rise or fall times. I didn't quite understand how this relay have that much short rise time. In datasheet it says operate time is several milisecons
Coax cable is storing voltage and after triggering the field coil it discharges trough it to 50ohm load. Is it important to choose a fast driver to switch relay? I tried this circuit with 300pF capacitors  (instead of coax) and 250V. But rise time is about 6-7 ns. What can I use to decrease rise time. Is length of oscilloscope probe and speed of driver important?
Btw I didn't use 50ohm environment. Does it effect rise time?
Here datasheet of relay I used
Here is the circuit:


texts: Signal buffer with op-amp clamping and voltage bias

texts:
I'm new to EE and have a question about signal buffering. I'd like to use two brief paragraphs to give some background and context.

I live in the SE Asian country-side. Mains supply (230VAC 50Hz) is unreliable and noisy: voltage occasionally drifts down to 200V and contains transients from old irrigation pump relay switches, and who-knows what else. In response to frequent power outages anyone with a desktop PC also has a UPS but many people report that their UPS simply dies after 6 months. I've had a cheap one burst into flames after it switched rapidly under low mains supply.

To provide my electronic equipment with "cleaner" and steady power, I am designing a power regulator that transforms mains AC down to 36V rectified DC and then regulates its voltage and current to 24V and 16A. My question relates to the circuit that indicates the output voltage of the transformer/rectifier stage.

My design emulates the LM3914 LED bar display: receive the signal, shape and buffer it, then pass it off to a resistor ladder with an op-amp array driving the LED display bar. The signal buffer sub-circuit is shown below. It uses an op-amp clamp circuit outlined on wikipedia, with a 5V reference clamping voltage, and a negative (2.5V) clipper on the output.

The signal comes in hot from the transformer just after having been rectified to DC. At 230VAC the transformer should yield 36VAC but due to the gruesome state of the mains supply it could drift down to 26VAC several times during the day, as well as spike to 60VAC on transients. So, although expected to be a nominal 36V, the DC input ranges between 0-60V and I want to visually monitor its variance. The circuit above immediately divides the signal down to 0-11V range (at node W) and a zener diode clips spikes above 8.2V. The signal is then below the 12V supply to the op-amp.

The test signal (top panel), during phase B simulates a few transients and then rises to 50V after which it drops to zero (power outage) at phase C. Since most of the input signal variance is expected to be between 24V and 40V, I am only interested in buffering this range (between the red arrow heads, 24-40V). Hence, the clamping op-amp configuration. To get rid of signal <0V a clipper via D3 removes the lower 2.5V of the op-amp output signal (lower panel).

The buffer can then provide the interesting mid-band of signal to the LED display circuit as a tight and efficient 0-5V representation of the 24-40V range of the wild transformer output.

However, during phase A (start-up) and after phase C (power outage) the op-amp output tends toward the 5V reference voltage. How can this be avoided? When input is zero, the buffer output should, truthfully, tend to its minimum too.

In addition to the main question, I would appreciate comments about the circuit design and choice of components and welcome advice for handling phase A (soft start?) and correcting input/output impedance.

Update

Using @The Photon's advice I went back to reading about clipping and clamping today. The input signal is not AC and almost all of the attempts to clip and clamp in my original circuit diagram (above) were misguided.

So, as suggested in the accepted answer, I got rid of the capacitor, voltage reference, etc and replaced everything with a zener diode, D2, which offsets the pre-opamp DC signal (yellow plot in the image below) downwards into the 0-5V range I require at buffer output (green plot)

Also suggested in the answer: increase the values of R1 and R2 and reduce strain on op-amp. Circuit current is down to micro Amps. The most active component, the op-amp output, is plotted in grey.


texts: If planar coil is used as antenna, then what kind of antenna should it belong to?

texts:
The image below shows the example of planar coil I mean. In my search, I found it is similar to NFC antenna, or in the other words, loop wire antenna. However, I don't see there is a hole in the centre of the coil. By a rough definition, loop antenna can be seen as a short circuit between the two terminals of the signal feed.
So, what is the type of antenna that an arbitrary planar coil belongs to, if it is used as an antenna?
If I manufacture it on a PCB board, is it now a microstrip antenna? Or is there another name or definition of that kind of antenna?
(P.S. This question is more about the definition.)


texts: I want to learn how computer memory sticks can be used as secondary storage using some intermediate FPGA for data processing. Actually I want to design a PCB myself. I'm good with PCB designing but I don't know anything about this device. I did some research on the internet but couldn't find some open-source designs and schematics. So it would be great if someone points me to directions. I need SATA to DRAM adapter reference design like this one. Thank you.


texts: Operating voltage range of frequency mixers using diodes

texts:
Because diodes have threshold voltage, I suspect that there exists operating voltage range of frequency mixers using diodes without op-amps or transistors (anyway op-amps and transistors themselves have operating voltage range). Is this correct?

If so, can diodes' voltage range be pushed up or pushed down easily, without need to increase its size?


texts: Drive multiple LEDs at different voltages from a low current I/O

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I have 2 RGB LEDs that I would like to drive using a uC. All channels draw 20mA, the nominal fwd voltages are 2.0V, 3.2V, 3.2V and the min fwd voltages I've measured are 1.7V, 2.5V, 2.5V

What I would like to do is to be able to control the 3 channels individually using 3 DIOs from the uC in order to mix colours. I would also like to be able to dim the 3 colours globally in analog hardware if possible.

I've attached a schematic of what I was thinking about doing but I have concerns about the two LEDs being different brightness and whether the global control will work. Any advice would be appreciated.

RGB LED Datasheet


texts: Using only stray capacitance for MCU oscillator circuits

texts:
I've included a diagram of typical Pierce oscillator circuit taken from ST Application Note AN2867:

The note suggests that C_L1 and C_L2 should be chosen such that the following equation holds:

Since C_L1 and C_L2 are typically equal, this equation can be rewritten to solve for their value: C_Lx = 2(C_L-C_S).

As a rule of thumb, the stray capacitance is usually taken to be 2pF - 5pF, although I've seen a datasheet suggest 10pF as a rough estimate.

The question: By choosing an oscillator with a low load capacitance C_L, e.g. equal to the expected stray capacitance, C_Lx goes to zero. Is there any problem with choosing an oscillator with a small load capacitance and eliminating the need for the two capacitors C_L1 and C_L2 from a design by depending solely on the stray capacitance?


texts:
I have some basic questions about crosstalk. My reference for this question is this website.
This website introduces crosstalk in this way:

Crosstalk is the unwanted coupling of energy between two or more adjacent lines. This unwanted coupling can change the required signal. Crosstalk size estimations are commonly divided into two separation calculations:

Energy that is coupled from the actual signal line, the aggressor, onto a quiet passive victim line so that the transferred energy "travels back" to the start of the victim line. This is known as the backward or near-end crosstalk.
Energy that is coupled from the active signal line, the aggressor, onto a quiet passive victim line so that the transferred energy
"travels forward" to the end of the victim line. This known as forward
or far-end crosstalk.

If the victim line is not terminated at both ends in its characteristic impedance the induced spurious signals can reflect at the ends of the line and travel in the opposite direction down the line. Thus a reflected near-end crosstalk can end up appearing at the far end — and vice versa.

First question: how can we define the end and the start of the victim line? Since it is passive, I think it is arbitrary if we call a termination "end" and the other one "start" or viceversa. So, I'd say that a backward crosstalk may be seen as a forward crosstalk or viceversa. Is this true?
Second question: which is the cause of the simultaneous presence of both types of crosstalk? Impedance mismatch? If the passive line is closed at the beginning with matched load and at the end with mismatched load, will there be both crosstalks or only forward crosstalk?
Let's see now more in detail the forward crosstalk.

The far-end crosstalk can be considered as an effect caused by the difference in velocity between the odd and even modes of propagation and thus a difference in edge arrival times at the end of the line — see Figures 2 and 3 below.

Third question: odd and even modes have not been defined. What are they and why do they propagate with different velocities? And why this phenomenon determines interference (crosstalk)?
Fourth question: in the analysis of directional couplers I have found an oscillating behaviour of power along the lines with respect to the position (shown in the following picture). This situation is not considered in the previous analysis. Is it a different situation (since the directional coupler have a high coupling factor, while the previous analysis considers weakly coupled lines)?


texts:
I am coupling an electret microphone to the input of an audio codec which does all the amplification, so all I need is biasing and filtering.  I picked up the circuit from a colleague and I'm having some trouble understanding an aspect of the circuit (attached).

The issue I have is the resistors on the right hand side of the drawing - why are these needed.  This circuit was adapted from an analogue solution where the output was to the inverting input of an opamp, where clearly these 22k resistors would be required, but is that normal in a passive filter?

Also, the 1k resistor in parallel is confusing, I'm guessing it may be to set input impedance, but this is defined in the datasheet of the codec, so could this be fine to remove?


texts:
I had a wireless powersocket for my PC peripherals until it stopped working. It just kept closed even if I turned it off and heard clicking. I opened the socket and replaced the board inside with my own relay circuit and the same happened. If I cut power long enough, the relay was opened again, but only until I turned it on.
My question is, if it's possible that the power-supply of my PC-Screen could be the problem, as it was directly behind the socket. It was switched by the relay too and I think the coil in there kept magnetized the coil inside the relay. Is that true?


texts:
I'm using a PIC32MM0064GPM028, all pins are currently used. I would like to use UART2 briefly for sending debug output to a terminal. Datasheet tells me that UART2 and UART3 can be used with PPS (UART1 cannot).

Furthermore, I'm using PGC/PGD1 located on RA0/RA1. These two pins are the only ones not having pull up-resistors or diodes or similiar, because the datasheet tells me having these components on PGC/PGD it will interfere with the programming.

My question is: can I map UART2 to RA0/RA1 without the UART-module interfering with the programming of the chip (using Pickit 3)?


texts:
I am trying to switch on and off a circuit that draws about 0.8 amp at 12 V. The obvious choice is to set a MOSFET. The problem is that the control signal (the one that goes on the gate of the MOSFET) is changing very slowly (1 volt per hour). So when this slow signal reaches MOSFET threshold voltage it is not instantly turned off or on, it is operating in bad non saturated mod for some time.

How do I make a switch that turn on and off instantly?

I tried to use a relay that is controlled by MOSFET with zener diode as voltage sense. That will not work because when relay is switched off the current stops and power supply increases the voltage a little (because no load), and sense circuit thinks that voltage is ok again and turns relay back on. So relay open and closes like crazy near that threshold region!


texts:
Hi, this is from Razavi's Analog CMOS IC Design book (2nd edition) - Pg 49.
He says that " We observe that the circuit provides a gain of about 3 in the input range of 0.4V to 0.6V"

But if you look at the graph, at the input of 0.5V, the output voltage is approx 0.55V. 0.55/0.5 = 1.1. Where is he getting the gain of 3?


texts: Large delay between I2C messages on STM32F303 - trying to read as fast as possible

texts:
I've got a sensor that I'm reading via I2C. My end goal is to be able to maximize the rate at which I can take these readings.

In order to read, I have to write an zero-byte I2C message to the slave to 'wake it', after which I can send a read and receive 2 bytes back with the measurement.

To test my maximum read rate, I set up a basic scheme in which the TX-complete interrupt for the wake message sends out the RX message to the slave, and the RX-complete interrupt sends out another wake-up.

I'm using the HAL libraries, and the relevant code is below:

void HAL_I2C_MasterRxCpltCallback(I2C_HandleTypeDef *hi2c)
{
    //RX finished, wake the sensor back up for a new reading
    HAL_I2C_Master_Transmit_IT(&hi2c1,0x28<<1,0,0);
}

void HAL_I2C_MasterTxCpltCallback(I2C_HandleTypeDef *hi2c)
{
    //Wakeup is finished, read measurement into buffer
    HAL_I2C_Master_Receive_IT(&hi2c1, 0x28<<1, buffer, 2);
}

Right now I have no other code running, either in the main loop or in these callback functions (I will eventually implement data processing, but I want to benchmark the maximum speed first).

When I look at the I2C Bus with a Logic Analyzer, I see the following:

There's a fairly large 'gap' between all of my messages, and I don't know what's causing it. There's no computations or anything that should be delaying the chip.

The bus is configured to run at 400 KHz.

Any idea what's causing this delay, and if there's a way to eliminate it to increase my maximum polling speed? Is this just a byproduct of how the I2C protocol needs to work?

Thanks for your help!


texts: Creating a wireless transmitter/receiver for off-the-shelf siren

texts:
Since I oddly enough haven't been able to find a suitable off-the-shelf product that's reasonable priced (less than 50-60 EUR/USD) and somewhat good looking with Google, I'm about to try a small electronics project as follows:

I have a simple alarm system controller for vehicles that run off 12V with a backup battery. This controller has a siren output with +/- terminals that delivers up to 800 mA when the alarm is triggered. Here's the catch: I want to have the siren wireless so it doesn't have to be mounted in the vehicle, but on a wall some 10 meters away to attract attention. I could run a cable on/in the ground for that distance, but I'd like to avoid that.

I've been googling for weeks for various solutions that doesn't require me to build everything from scratch. My conclusion from these searches is that the neatest solution would be to hook up a wireless (e.g. 433 MHz) transmitter to the alarm controller output and then connect a corresponding receiver to the siren. However, I haven't found a suitable transmitter/receiver combination pre-built, so I'm looking for options to build them.

The closest thing I've found are a couple of Chinese products: the transmitter part e.g. https://www.aliexpress.com/item/433MHz-Wireless-Transmitter-Module-For-Our-Wireless-Siren-For-Our-Home-Burglar-Security-Alarm-System/32917159619.html but those requires the vendor's own siren which is branded (in an ugly way) such as https://www.aliexpress.com/item/NEW-High-Quality-Wireless-Waterproof-Strobe-Siren-433MHz-For-Home-GSM-Alarm-System-Security/32813027446.html.

The question is this: could you please recommend how I would go about building a wireless transmitter like the one above that runs on 12V and max 800 mA and a receiver that can (ideally) be battery powered? I've been trying to find similar threads here, but most people ask for more complicated things like transmitting more than on/off or actually building  building the sending/receiving part from scratch.

What I'm looking for is something that powers up when the alarm goes off and sends an ON signal to the receiver. Upon receiving the ON, the receiver then powers up which makes the siren sound. The receiver should then drop the power to its output (siren) after either a fixed or variable amount of time depending on how much complexity to the build either option adds. In any event, there needs to be some kind of safeguard so the siren doesn't sound until the battery is drained.

The siren I'm thinking I could connect a receiver to is something like this: https://www.aliexpress.com/item/12V-103-Mini-Wired-Strobe-Flashing-Red-Light-Siren-Durable-Alarm-Siren-Home-Security-GSM-Alarm/32858844694.html. Runs on 12V with 300 mA current. The beauty of the receiver should be that it just has a 12V output, so that I can connect another siren if needed.

Bonus: the sender and receiver should be linked to each other, to avoid anyone just sending a ON message on the siren and have it sound. Not needed though, I could rely on security through obscurity if it reduces complexity for the build.

I'm ideally looking for something that doesn't require me to create a PCB, and create PIC code etc. E.g. Arduino is fine I think, but I don't have a clue on how to program it. Soldering I can learn if needed, possibly the programming part as well. I'm looking for the best combination of low price and easiness to build here, rather than using expensive Z-wave controllers (expensive) on one hand or build everything from the ground up on the other (difficult).

Any tips or pointers greatly appreciated!


texts: In light of the new FCC rules that Chinese (and all non-MRA) labs will no longer recognised in July and all EMC tests need to be done at FCC-authorized Telecommunications Certification Bodies, for FCC EMC tests that were previously done at Chinese, etc. labs, will they all need to be redone? If they do, that could probably mean a massive surge in demand in the months following July.


texts: A transformer has a fixed output ratio. E.g. 10:1, for a 23Vac supply from 230Vac. But it is found that under light load the voltage rises above the nominal (at rated load) - why?


texts: Max7219 and Common Anode Displays, choosing the correct transistors

texts:
I've got some common anode 7 Segment displays that I want to use a Maxim 7219 IC to drive with. The Max7219 is designed for direct driving common cathode displays but Maxim do have an app note that describes using the chip to drive higher current and/or voltage 7 segment displays as long as they are in a common anode configuration. In my case I want common anode, but at regular voltage/current levels.

The led's are fairly typical, 25mA max current, 3.3Vf, and I intend to drive everything from a 5V supply voltage.

I am not really sure what I should  be looking for in the transistors though? I went for these two

2n3904 NPN Datasheet

AO3401A Fet Datasheet

as they seem to be able to handle the relatively small currents and voltages involved, and seemed to be quite cheap. My proposed circuit is below.  Does this seem like a good choice?


texts: How to reduce ADC output value fluctuations?

texts:
I'm trying to read the output voltages of some LMC6001 op-amps through an ADS1115 ADC, to get higher resolution.
In the process of doing so, I'm reading huge fluctuations on the serial monitor without giving any input to the op-amp.

How do I reduce these fluctuations, so as to get stable ADC output values?
I tried to measure the offset voltage of just the op-amp at the output which is 0.3mV, but at the serial monitor the readings are varying from 5mV to 20mV.
Please help me to overcome this problem.


texts:
I just downloaded a model from the TI website for the following component : REF3325.
I need to put it in my schematic in order to simulate it after.
But in the .rar I downloaded, there is only a *.LIB file, which I can add to my installed libraries in Altium but it says there is'nt any component in it.

Do I need to convert this file into a IntLib? Or do I have to create the component by myself ?
I don't really understand the difference between this *.LIB and the *.IntLib formats ...

Thanks for your answers


texts:
Hi guys I'm trying to turn 32 volts into 5v using a voltage divider.

The precision of the device concerns me as because it is fed to an 16-bit analog to digital converter. Could someone provide me a circuit that will precisely step down the voltage.

I tried using resistors but the tolerance of the ones I have are too high....

I do not have any degree of electrical engineering, so keep it as simple as possible.


texts: USB digital microscope and ESD safety (maybe power supply problem)

texts:
I have an ESD mat, ESD wrist strap and a Chinese USB (power only) digital microscope(Andonstar ADSM201.)
I  use the microscope for soldering and inspection at home for hobby projects.
The microscope is powered by a USB charger from the wall plug, so it is not connected to the same grounding point of the mat and wrist strap (because the charger has only 2 pins on the plug, not 3 like mine Earth bonding point.)
I know the microscope is not ESD-safe, but I don't know other solutions than maybe buying a professional microscope for 1000-2000USD.
So I thought: I can attach the body of the microscope to a flexible arm outside of the mat, so that it stays 15cm above the mat (and ICs.)
However, when I touch the metal part (aluminum?) of the microscope to adjust focus, I feel slightly unpleasant "pinches" on my wrist, where the ESD wrist strap is. I guess we are not at the same potential and current is flowing through my wrist. Wrist strap has 2MOhm resistance to ground.
I've tried also to let the metal part touch the ESD mat, but no changes.
If I remove the wrist strap and touch the metal parts of the microscope, I don't feel anything.
Also if I put some insulating tape on the focus ring, I feel no pinches, but that's not good for ESD.
Is this normal or should I be worried about my safety?
I see online lots of people using such USB microscopes, but nobody mentions ESD safety.
Is there no other solution than buying a professional ESD safe microscope?


texts: Error caused by Scope or Function Generator?

texts:
This question may not be valid, please excuse my ignorance. I am having difficulty measuring a decent square wave at 500kHZ. The image below shows a 4 volt CMOS output with a frequency of 500kHz connected directly to the scope using a 2' BNC cable.

I am an engineering student so both pieces of equipment are older and on the used side. Kinda like my first car. The function generator is made by BK Precision and is labeled as a 5MHz generator. (Model: 4011). The scope is a Tektronix 465B that is rated to handle at least 5MHz. The function generator has a TR and TF <= 120ps.

Scope Manual

Function Generator Manual

Obviously the output is nowhere close to a square wave. The horizontal scale is set to .5us. The same output generates a square wave at much smaller frequencies. Is there anyway to tell from the image below which piece of equipment is ancient and should be replaced first? I can't imagine a world at 500KHz.

Any help would be much appreciated! Thanks for reading.

Output Image http://itssimplydesign.com/outputwave.jpg

======UPDATE====== 8:30 pm 2012.11.03

I attempted to calibrate the oscilloscope, but all of the tests turned out to be ok. The Trace Rotation screw was about a quarter of a degree off so I adjusted the rotation a tiny bit. The ASTIG screw was already aligned for optimal focus. In the original post I was using BNC to alligator clips to probe the circuit. I just went to the lab and picked up a 100MHz Tektronix probe to replace the clips. The output of the function generator is the same...

HOWEVER.....

When the function generator is attached to a CMOS inverter (ZVP4105A and ZVN2110A) with a 1pF capacitor the output wave is a perfect square wave. The circuit is shown below:

CMOS Inverter http://itssimplydesign.com/inverter.jpg

All of the parameters remained the same. The function generator is still producing a 4 Volt 500 kHz* input wave. The input wave looks exactly like the first picture above (sawtooth) Yet the output is now perfect. (See image below). I have no idea how this could be possible.

CMOS Output http://itssimplydesign.com/OutputWave_CMOS.jpg

How can a function generator attached directly to a scope produce such an under-compensated wave but when the same generator is attached to a network it turns out normal? TEACH ME!!

Edit fyi: Mhz -> kHz.

======Update #2======== 3:07 am 2012.12.03

After pages and pages of my final EE252 lab report I have reached several conclusions. Unfortunately none of the pain staking research has to do with the actual report content. But I am a perfectionist the has to know why things do what they do. Here are the four different scenarios I put together regarding the damping shown in the earlier posts.

Four http://itssimplydesign.com/scope.png

All of the waveforms shown in the image above represent the input waveform only. Refer to the CMOS circuit in the first update for reference. Waveform (a) was produced by placing a BNC to alligator clip directly to the shared gate. Ugly, I know. Waveform (b) was formed by placing the x10 probe directly to the shared gate node. It is almost perfect. Waveform (c) introduces a 50 Ohm termination resistor (to balance the function generators 50 Ohm impedance) between the input and shared gate. This measurement was also taken with the clips placed directly after the terminating resistor. I assume that the continued damping effect is caused by faulty resistor values in addition to a floating output impedance. The final waveform, waveform (c) was created by using the combination of a 50 Ohm resistor and the probe. It was interesting to discover option (b) provided the best results. I assume this is where the probe adjustment would come into play. I will be sure  to take a look in the near future.


texts: How to use a power meter to measure irradiance?

texts:
I have got a Zes Zimmer LMG95 power meter and an RS-ID-5 Fraunhofer ISE WPVS reference cell.

The LMG95 has got simultaneous voltage and current measurement and can do custom calculations. The WPVS contains an monocrystalline N-type solar cell and a Pt100 class A RTD connected to the back of the solar cell.

How can I measure and display the (outdoor) irradiance including temperature compensation?