texts:
I have an issue to solve. I'm going to measure an object that looks like this.
My question is if the sensor VCNL4040 have a very wide spread light or very "laser-like" light that concentrates everything in a small area? Because I have walls that I don't want to measure at.

VCNL4040 using an IR-led that consumes 200mA
Datasheet: https://www.vishay.com/docs/84274/vcnl4040.pdf


texts: Total capacitance at output of source follower

texts:
This is the voltage gain of source follower at high frequency.

What I am confused here is why Cdb1, Cdg1 are not included in the pole of the transfer function?

Should it be Cgs2 + Csb2 + CL + Cdb1 + Cgd1 instead of Cgs2 + Csb2 + CL?

Thank you.


texts: Use transistors for controlling two LEDs

texts:
I'm sure this is a pretty basic question, but I wanted to run it by you guys before creating my PCB.

I want to have two LEDs on the board to indicate the global state of the board. When the board has power, but the MCU is not in an active mode I want the Red LED to light up, and when the MCU puts a pin high I want the red led to be replaced by a green led instead.

I want to solve the problem using simple electronics, and not with RGB led, etc.

My idea is to use two transistors. One which is normally closed (the green one), and one which is normally open (the red one), and then toggle them on/off using a signal from the MCU.

Does the following circuit make sense?

Edit: Lots of good suggestions here. The MCU is a Teensy 3.2, which has 3.3V output, and 25mA Max current on the digital GPIO pins. I have both 3.3V and 5V powersources available on the board.


texts:
I'm relatively new to EE, sorry if this is newbie territory.

With an Arduino, I am trying to emulate a device that outputs NEGATIVE 3.3v PWM (0V or -3.3V, square wave) at around 500 hz.

Obviously, the PWM out of an arduino is 0V or +5V  (or +3.3v depending on the arduino) but there is no way to output negative voltage.

I've researched feeding the signal through a ICL7660 but it's unclear if the 7660 will produce a clean-enough negative square wave.

I also researched the MAX749, which will produce a negative voltage from a PWM, but it's unclear to me if the MAX749 will actually output a negative PWM square wave, or if it will instead output smooth negative (but variable) voltage output based on the duty cycle of the input PWM'd positive voltage source.

I've also heard that maybe I could accomplish this with a MAX232 since the RS232 standard has negative voltage signals as part of the communication standard but have no clue how to go about this.

Thoughts?


texts:
I have successfully created an ATtiny406 binary using avr-gcc in Linux, and I can program it to the device via Atmel-ICE under Atmel Studio in Windows, and it behaves correctly.
I would prefer to be able to program the device using my Atmel-ICE in Linux. So I did pip3 install pymcuprog-3.7.4.95-py3-none-any.whl and it says:
Successfully installed appdirs cython hidapi intelhex
pyedbglib pymcuprog pyserial pyyaml setuptools-20.7.0

It seems that the packages were installed... but how do I run the utility? As suggested on the mymcuprog website, I tried pymcuprog --help but that said
pymcuprog: Command not found.

I also tried python3.5 -m pymcuprog --help but that said:
/usr/bin/python3.5: No module named pymcuprog.__main__;
'pymcuprog' is a package and cannot be directly executed

I also tried python3.6 -m pymcuprog --help but this is even worse:
/usr/bin/python3.6: No module named pymcuprog

I don't think Ubuntu16 supports Pip in Python 3.6 (I am at the latest python-pip3, and it seems to be Python3.5). In my experience, it's best not to go beyond versions tested by Ubuntu.
Regardless, it seems that pip3 installed the pymcuprog modules in Python3.5 without complaining. I thought pip3 would install the main module as well? (it has worked for me in the past, on other software). If not, then how do I get the main module and run it?


texts: Does a gyroscope require calibration? (MPU 6050)

texts:
If it does, what is the method that I need to follow? Any suggestions?

Edit:
Are these the offsets?


texts: Unable to program Freescale Kinetis KL26 microcontroller over SWD

texts:
I just assembled a board that I have created that basically acts as a breakout board for a MKL26Z32VFM4. Today, I am trying to get it to communicate over SWD so I can program the initial bootloader. I've never done anything like this before and this is basically an experiment for myself to see what it takes to go from datasheet to working device with one of these microcontrollers.

I have another microcontroller emulating the SWD interface and it might not be emulating it properly (I haven't yet actually counted the pulses to make sure it is using 50 pulses to initialize). In any case, the KL26 failed to respond when I held RESET_b low.

I decided to see if the processor was even starting, so I put the oscilloscope on the RESET_b pin when it was left floating to see what would happen. According to the datasheet, it is pulled up internally and during the boot sequence it is driven low until the processor reaches a certain state. It then releases the pin and sees if it is rising fast enough (KL26 family reference, 6.3.3). If it isn't it keeps the processor in reset mode.

I see the following waveform on the RESET_b pin (pin PTA20):

This doesn't look right at all. I should see it just simply high, not making a nice RC curve between 0 and 3V at approximately 30kHz (it's really wiggly as can be seen).

My theory: It is somehow stuck in a boot loop since it is driven low quite rapidly.

I could put a resistor on the reset to raise it to 3.3V, but I'm curious as to why this is happening. There are possibly a few mitigating factors:

This is my very first QFN chip that I have soldered by hand. I soldered it by tinning every pad, laying down flux, setting the chip on top, and then heating up a via-connected thermal pad on the back of the board for approximately 5 seconds while tapping the chip with tweezers. It appears to have soldered well and the 3.3V usb regulator seems to be working fine (at least the voltmeter and oscilloscope say so). It is possible that I have a void somewhere or a cold joint.
There was an ESD incident when the device was powered off and not connected to anything. I touched it with both hands to lift the board from my breadboard and felt a slight shock. The regulator still works and the chip doesn't let out smoke or heat up when powered on, so I'm not sure what happened here and if it is a problem. I have 2 additional backups that I could use, but that would require assembling them. I swear, if this is the problem I'm going to buy an ESD strap right away (yes I'm assembling this in my apartment, on a computer desk, sitting on a carpet, and it's cold outside (i.e. low humidity inside)).

In any case, my questions are:

How do I properly connect the chip for SWD? It's powered on, reset held low, and SWD connected to the appropriate pins, right? Am I missing something? My SWD program outputs 50 clock cycles, issues the SWD switchover command, outputs another 50 clock cycles, and attempts to read the IDCODE register.
What could be causing this strange RESET_b behavior? Did I break something and have to start over?

EDIT

I have some additional waveforms from my programming attempt that might help. Clock frequency is 26Khz (KL26 says it can go up to 25Mhz).

Rise time on the SWD_CLK: 37nS (KL26 datasheet table 17 says this should be max 3ns...hmm)

My transaction: 50 pulses, 16 bit switchover command, 50 pulses, read IDCODE

The switchover command:

The read IDCODE command and lack of response from the KL26:

Edit 2

Enabling the DSE bit on the PCR register for my SWD clock decreases the rise time to 7ns, still above 3ns. It also causes a ring that peaks at ~3.7V (the line settles at ~3.2V).


texts: Single switch circuit to turn on/off an LED

texts:
I have very basic knowledge of electronics.

I am looking for a circuit which can turn ON/OFF an LED from a single switch.

If the LED is OFF and the switch is pressed (even if not released) then the LED should turn ON.
If the LED is ON and the switch is pressed (even if not released) then the LED should turn OFF.

A switch can be a push to ON switch but turns OFF when released. It is not like a toggle switch.

Thanks in advance


texts: What resistors to use to read several buttons with a single analog pin

texts:
EDIT: Thanks, all of you helped a lot! Ricardo summed everything up nicely so I'll mark his answer as the best, but all of the answers helped me understand. Thanks again :).

I have an Arduino Uno R3 and I want to connect a circuit that will allow me to read several buttons using a single analog input pin. Basically I want the circuit to mimic a discrete potentiometer, but I want to use buttons instead of a knob. How can I do that? And how do I know which resistors to use in my circuit?

Here's a picture of the circuit I have in mind:

What values should I give the resistors? And why?

How can I connect such a circuit so my arduino won't fry?


texts: How long would a 150 Farad Capacitor light up an LED

texts: I have a bright white LED from a flashlight. Aproximatley How long will it light up with a 150 farad 2.5 volt capacitor. Do I need a resistor? And if so how many Ω? The capacitor is a maxwell 150 farad 2.7 volt boostcap here.


texts:
I am using an ESP32 to generate a 113 kHz, ~3,5 V output. I then intend to amplify this to a ~50V peak-peak waveform. For that I am trying to use a DC-DC converter based on the LM2577 (to boost from 12 V to 50 V) and the Logic Level MOSFET IRLZ44N.
The DC-DC part seems to be working fine, as I can get a 50 V output. However, once I connect the output of the ESP32 to the IRLZ44N (like the diagram below) I cannot get a waveform at the output, just a 50V DC voltage. Is anything wrong with the circuit?
The IRLZ44N seems to be working fine. Below is also a picture of the ESP32 output from the oscilloscope. From what I've been reading, the current source capacity of the ESP32 is 40mA (I am not sure this is true for the LED PWM output I am using, this might be the problem). Cout = 220uF electrolytic.
Will appreciate some feedback. Thanks in advance.


texts: How can I find the time at which the diode charges the capacitor every cycle(half wave rectifier)

texts:
Half wave rectifier is given and given values are :

V_p = 10V, V_d = 0.7V, 1/T = 60Hz, R = 10.

I want to know when C = 0.1F, how can I find the time at which the diode charges the capacitor every cycle.

I failed to approach this problem because I'm not sure at which parameter I should find out. I'm understanding capacitor charging time is T, but I don't think T=1/60 is answer.

I tried so far on this :

$$i_{DMAX} = \frac{V_p-V_d}{R} + C\cdot V_p\cdot \frac{2\pi}{T}\sqrt{\frac{2V_R}{V_p}} = 65.02A$$

$$ dv/dt = V_P\cdot  \omega \cos(\omega t)$$

---redo---

Now I find when charging time is \$ \Delta T\$

$$v_0(T-\Delta T) = V_p-V_d-V_r$$

and

$$V_r =\frac{(V_p-V_d)T}{RC}$$

$$v_0(T-\Delta T) = V_pcos(\frac{2\pi}{T}\Delta T)-V_D$$


texts: Common Source vs. Common Drain for N-Channel Switches

texts:
Most discrete load switches I have seen (Using N-Channel FETs) have been in the common-source configuration. What, if any, are the operational differences between this and the common-drain configuration? I understand that a gate driver with a charge pump is necessary in both cases, but do they need to be driven in different ways?
Common Drain

Common Source


texts: Why is recombination rate in an intrinsic semiconductor proportional to product of number of mobile electrons and number of holes?

texts:
I know that when an electron falls into a hole the number of mobile carriers reduces to zero from two. And when an electron jumps into conduction band the number of mobile carriers increases to two from zero.

But I cannot understand why recombination rate is proportional to the product of holes and conducting/mobile electrons. Does understanding this requires so much complicated math. I know basic probability but is this possible to explain this in high school level? How does the product of those is related to rate?


texts: Clipping negative voltage with resistor divider as load

texts:
I have a dual-supply op-amp (±12V) that outputs a signal in the range of ±3V. I cannot neither change the op-amp configuration nor add another one. Please not the schematic below is just an example. The actual configuration is more complex, but it doesn't matter about the question.

The output goes to a voltage divider and I need to clip the negative voltages.

The common way is to add a diode on the output:

simulate this circuit – Schematic created using CircuitLab

But when the output swings below the threshold voltage nothing limits the current.

Where should I put a limiting resistor?

in series to the diode? I think it will affect the clipping
on the op-amp output, after the fb node? I think it will affect the resister divider
on the op-amp output, before the fb node? I'm afraid it will affect the feedback gain

Is there a better way to achieve this?


texts: How is capacitance found when there are 2 different regions with dielectric in the in 2 parallel plate capacitors connected in series

texts:
The two capacitors are part of a capacitive pressure sensor, I am curious with reference to electrostatic theories how would capacitance be found in respect to the dielectrics.
The two capacitors have 2 different dielectrics within them too. There is a diaphragm in between (moved by pressure of one capacitor and pressuring the other.)


texts:
I have a stream of signal values (e.g. 10, 12, 13, 11, 15, 12,500, 10, 23, 25, 30, 200).

As you see, some noise like the values 500 and 200 exist on the stream.

How can I eliminate this noise or reduce it?

The peaks are detected using a fixed threshold value (e.g if the signal value +/- 50, then this value is a peak).

My Algorithm is:

I tried to make a mask with 10 values and then calculate the average of it, through sloping this mask on the whole stream, i can substitute the peaks with the mask average and then shift the mask by one value.

are there any other algorithms to solve the issue?

Evaluation
My Algorthim is still influenced by the value of the peaks (of course) and also if several peaks are near to each other( like :  500,600,650,510,.. , 10,50)  so the mask average will be big relatively to the other averages.

are there any solution for this problem ?


texts: How to rewind microwave transformer to isolation transformer

texts: I'm thinking of getting an auto transformer and rectify it to make mains isolated 240V 8A DC power supply. I would like to know if its possible to rewind an old microwave transformer to 1:1 isolating transformer with maximum output of 2kW. I know that the waveform wouldn't be smooth so i'll be using beefy 450V 2000uF capacitor for rectification.


texts: On an old board I have found a strange component with seven wires going in/out. I was wondering if someone can help identifying its function.


texts: Wiring an audio jack to obtain soundwave signal

texts:
I have recently gotten a piece of MLX 87279 audio jack.
It seems to be an old discontinued piece but have managed to find its schematics online: https://www.molex.com/pdm_docs/sd/872791501_sd.pdf

However, I am having difficulty understanding the pin diagram and how I should go about wiring it up to output the analogue sound wave from the microphone.
e.g. Do I need a power source for this and where should I probe the oscilloscope to get the desired signal?

Thank you!


texts:
I'm building a smps using flyback topology with maximum aoutput voltage of 46V. I'm a novice, however I have read a lot about impulse power supply design. Right now I'm about to buy a transformer, and the one I want to buy has output voltage specified for 19V.

From what I understand, the transformer ratio in such a converter doesn't have to be exactly Vin/Vout, because Vout is determined by the duty cycle on primary winding.

Is that right? Is it possible to obtain 46V in this topology when Vout is only 19V?


texts: How do I synchronize my FPGA clock frequency with RS-232 transmission baud rate?

texts:
My FPGA Spartan 3E supports 50 Mhz clock via ocillators. Now I am using RS-232 cable connection to send output bits serially into my computer system using HyperTerminal/RealTerm.

However the baud rates the COM ports/RealTerm support are different. I am using a male to female connector cable.

How do I synchronize them both. I have tried including a FIFO inside my design with one end connected to my Design output (write) and read end connected to the RS-232 Transmitter at the Transmission speed clock, using a clock divider. But that doesn't make the synchronization happen as expected.


texts: F type female to SMA male adapter impedance question

texts:
I have a coaxial cable that I need to connect to a SMA female connect. The impedance of the cable is 75 ohms, and from online the SMA female connect is 50 ohms. Online there are a few places that sell F type female to SMA male adapters however most do not offer datasheets that specify the input/output impedance of the connector and if they do they only list the impedance without specifying.
 https://www.amazon.com/gp/product/B01FQE4BN6/ref=ox_sc_act_title_1?smid=A26SKYU6EEPEEF&psc=1#customerReviews


texts: PWM Motor Driver output voltage is enormously load - dependent

texts:
I've built this PWM motor driver (for a motor which requires 5A at maximum 24V and which I want to drive sometimes with 10V and other times at 24V). Here you find the datasheet of the mosfets.

PS: there is also a missing 10k resistance between gates and GND
The device works and supplies correctly my motor. If I use a 50% of duty cycle, I get an average voltage of 12V across my motor.
But, If I measure the output voltage without load, or with a low - current load (such as a 200mA fan), the device works (it provides an average voltage which is determined by the PWM duty cycle) but not with the right proportion: without load (the only load is my volt - meter) I get 12V (instead of 6V) with 25% of duty cycle and 20V (instead of 12V) with 50% of duty cycle. With fan the result is slightly different but always in contrast with the right proportion.
My possible explanation: the output voltage is, in theory, a square wave. A Volt - Meter, a fan and my motor filter it in different ways, so the result is different. But, if this explanation is true,

I'm surprised of such big differences between the behaviour with these different loads.

I don't know how should I take care of this fact and design my circuit to work properly with a specific load (for my motor, it works perfectly, but maybe it is lucky....I've never thought at this aspect).

I think that different loads will change the amount of ripple, and not the average value. But, in my measures, the average voltage is different.

Can you help me to explain this phenomenon in a more detailed way?


texts: How to convert 5V to 3.3V for all pins of wemos D1 mini when interfacing it with Atmega16?

texts:
I am trying to interface Wemos D1 Mini to Atmega16 and have communication between them using TX and RX pins.According to the datasheet, the maximum allowed current for the Wemos mini is 3.3V for all IO pins while the Atmega 16 is giving 5V at it's IO terminals.For this problem, I could come up with just one solution and that is to use a voltage regulator. But this solution will require three voltage regulators, 1 for powering Wemos D1 mini and 2 for TX and RX lines. This solution seems to complicate the design. So is there an elegant solution for converting 5V to 3.3V?
I am completely novice to the field of electronics and this is my very first project so there might be a mistake in my understanding of basic concepts.So if that's the problem then please let me know.
Thank you.


texts:
In the following AVR code, why do I always see the same voltage for all pins of port A?

I am using ATMega32.

BTW, when I am grounding some pins of port A I do not see any change in the output. It seems AVR neglects what ever I give to port A of it.

#define F_CPU 8000000UL

#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>
#include "lib/hd44780.h"

void InitADC()
{
    ADMUX=(1<<REFS0);                         // For Aref=AVcc;
    ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0); //Rrescalar div factor =128
}

uint16_t ReadADC(uint8_t ch)
{
    //Select ADC Channel ch must be 0-7
    ch=ch&0b00000111;
    ADMUX|=ch;

    //Start Single conversion
    ADCSRA|=(1<<ADSC);

    //Wait for conversion to complete
    while(!(ADCSRA & (1<<ADIF)));

    //Clear ADIF by writing one to it
    //Note you may be wondering why we have write one to clear it
    //This is standard way of clearing bits in io as said in datasheets.
    //The code writes '1' but it result in setting bit to '0' !!!

    ADCSRA|=(1<<ADIF);

    return(ADC);
}

void convert_text(double voltage,char *text)
{
    int voltage_n, voltage_f;
    voltage_n=(int)trunc(voltage);
    voltage_f=(int)trunc((voltage-voltage_n)*100);
    sprintf(text,"%d.%02d",voltage_n,voltage_f);
}

void convert_voltage_text(double voltage,int battery,char *text)
{
    char stext[20];
    convert_text(voltage,stext);
    sprintf(text,"V%d=%s",battery,stext);
}

void main ()
{

    char vtext1[20];
    char vtext2[20];
    char vtext3[20];
    char vtext4[20];
    char line1[20];
    char line2[20];
    uint16_t v_val1, v_val2, v_val3, v_val4;
    double voltage1, voltage2, voltage3, voltage4;

    InitADC();
    lcd_init();
    // DDRA=0;
    // PORTA=0;

    while(1)
    {
    _delay_ms(10);
        v_val1=ReadADC(1);           // Read Analog value from channel-0
    _delay_ms(10);
        v_val2=ReadADC(2);           // Read Analog value from channel-2
    _delay_ms(10);
        v_val3=ReadADC(3);           // Read Analog value from channel-3
    _delay_ms(10);
        v_val4=ReadADC(4);           // Read Analog value from channel-4

        voltage1=((double)v_val1)/1023*5;
        voltage2=((double)v_val2)/1023*5;
        voltage3=((double)v_val3)/1023*5;
        voltage4=((double)v_val4)/1023*5;

        convert_voltage_text(voltage1,1,vtext1);
        convert_voltage_text(voltage2,2,vtext2);
        convert_voltage_text(voltage3,3,vtext3);
        convert_voltage_text(voltage4,4,vtext4);

        sprintf(line1,"%-10s %s",vtext1,vtext2);
        sprintf(line2,"%-10s %s",vtext3,vtext4);

        lcd_clrscr();
        lcd_goto(LCD_LINE1_POS);
        lcd_puts("");
        lcd_puts(line1);
        lcd_goto(LCD_LINE2_POS);
        lcd_puts("");
        lcd_puts(line2);

        _delay_ms(100);
    }

    return(0);
}


texts: Microchip 23LC1024 driver for Atmel XMega

texts: Is there driver or any example code available for 23LC1024 SRAM memory implemented with Atmel XMega or mega-series microcontroller?


texts: KiCad netlist output GND not labeled 0 for Ngspice

texts:
As the title suggests, I'm having trouble generating netlist from KiCad for Ngspice, the problem being that I can't get KiCad to output a "0" node for "ground".

I'm aware that I'm supposed to use the "0" as my ground from the pspice library, but somehow it doesn't work for me.

I found this guide KiCAD Schematic: Naming Nets and ngspice Simulation in Linux, which seems to address the exact issue I'm experiencing; however, when the guide says

  You can use Global labels instead of net name labels. When you use Global labels, the net names in the netlist are OK. Use 0 for reference instead of GND or Ground. That way it will be interpreted as 0 volts in the simulation.

I'm not getting the same result as the guide suggests; in fact, nothing really changed on my end. Attached are screenshots of my schematics and their corresponding netlist outputs.

I'm running KiCad Version 4.0.2+dfsg1-stable release build on Ubuntu 16.04.

I've poured hours in this trying to find an answer online, but none of the existing Q&A's seem to address this problem fully. Is there something I'm missing?


texts: I have a single phase industrial control transformer 480 V/ 120 V, 1000 volt amps. Should I fuse the primary or the secondary?

texts:
Single phase industrial control transformer 480 volt/120 volt 1000 volt amps.
Should I fuse the primary or secondary?


texts:
I was thinking; If a relay is used to power a circuit AND itself, if the circuit is shorted - the relay should lose its own power and turn off - almost like a resettable fuse.

To power it up, I would have to bypass the relay temporarily.

Is this a valid use case? I was actually planning to use it as a "suicide switch" for my robot, but it seems this is an additional benefit?

PS: I'll keep my main fuse as well.


texts: How to set up signal generator in lab to obtain an output voltage?

texts:
In one of my laboratory assignments, I am to study how to work with square signals in RC circuits (low pass filter). Please keep in mind this is an introductory Electronics course. Basically, I am thinking of using a 1k\$\Omega\$ resistot and a 6.8 nF capacitor. My square signal has an amplitude of 5 voltage peak-to-peak. Then, I am asked to start by setting the frequency of the generator such the output voltage as measured accros the capacitor is 63% of the input voltage.

This seems fairly easy: I need the Vpp of the output signal to be \$0.63*5V = 3.15 V\$, so then I just move the frequency button on the generator until I get this value on the screen, right? And the time constant would be half the period since a capacitor charges to 63% in one time constant, right?
Another part asks whether we can measure the peak to peak voltage of the output. To me, this is confusing since the capacitor has not enough time to completely charge and discharge, so wouldn’t the peak to peak voltage change continuously? It would just make sense to define these limits for one period.

I appreciate any help I can get. I know these are basic questions but I have to be at the lab tomorrow and I want to be prepared to work as well as possible. Thank you.


texts: Transform 5 2xAA battery power supplies TO 1 power supply

texts:
I bought some LED stripes here : https://fr.aliexpress.com/item/Neon-LED-Light-Glowing-ELWire-Strip-Tube-Car-Party-Decoration-1M-Lemon-Green-3-Modes-Waterproof/32797496356.html

They are all powered by two AA batteries (1,5V).

I would like to wired them all together and power them by a single USB battery like this one : https://fr.aliexpress.com/item/Universal-5V-9V-12V-6-x-18650-Dual-USB-Portable-External-Power-Bank-Battery-Charger-Box/32242946314.html

I'm a little bit afraid by voltage and amp risks, to be sure it will work perfectly.

If I did my research correctly, 1 stripe needs 3V to work correctly.
Then to wire 5 of them I'll need 15V right ?

I'm a little bit lost but I don't want to wear 5 to 10 power supplies with... 10 to 20 batteries !! (I want to create a LED outfit)

Thanks a lot for your advices !


texts: Unexpected sinusoidal wave at low voltage setting on oscilloscope?

texts:
I'm fairly new to electronics in general, and I'm learning to use an oscilloscope.

I have a 10X probe attached to a 1uF capacitor that is completely discharged. When I set the time interval on the o-scope for that channel at 10ms, and the voltage interval at 50mV I can quite clearly see a very low amplitude sinusoidal wave.

In fact, completely removing the capacitor and making a connection between the probe and ground produces the same sinusoidal wave.

Is this just a tiny bit of output voltage on the probe, or something external?


texts: What is the expression for the load current of the following Operational Amplifier circuit?

texts:
I have been battling to find the theoretical calculations to find the expression for the load current of the following Operational Amplifier circuit exercise I have in my "Electrical Engineering, Principles and Applications, Fifth Edition" by Alan R. Hambley? Unfortunately, there is no solution for it available.
I simulated the circuit in LtSpice, I know the input to feedback resistor ratio will result in a gain of 1 at the difference amplifier stage, with that taken into account I can figure out Iload = Vin*(Rload/Rf) and Output impedance is Rload. Download LtSpice Circuit here. - https://gofile.io/d/LukKU0
I'm definitely missing something with my theoretical analysis of the problem and would be really grateful if someone can assist me.
Thanks in advance
Stephan


texts: Identifying components on circuit diagram

texts:
I am interested in Linux device drivers development and needed a cheap and tiny USB supporting device that I could control, so that I could write software for both the gadget and the host.
I decided to use the ATmega328P AVR microcontroller, for which there is a USB supporting library - V-USB.
However, I cannot connect USB to it as it requires some electronic skills. Connecting the components in the circuit is rather simple, I just have a problem identifying them. Here is the diagram:

What is the difference between C1 and C2, C3, C4 capacitors?
What diodes should I use as D1 and D2? Description says "D1 and D2 are a low cost replacement for a low drop 3.3 V regulator chip, such as the LE33," but it doesn't mention their parameters.
Which oscillator should I use? I understand it must be a 12 MHz oscillator but it must also have 1 coulomb charge?


texts: Help identify waterproof tactile button cap

texts:
I’ve been searching for a special kind of tactile button cap that mounts to a panel and effectively makes it splash-proof, while still allowing the button beneath to be used. I’ve seen it on motorcycles, but haven’t found what it is called.
They look really handy for projects that don’t require a full custom key panel and they’re a lot smaller than screw-in waterproof buttons. They are mounting in the housing itself and transfer the push down to a PCB-mounted tactile switch.
Has anyone seen them before and maybe know what they are called?

Figure 1: Button panel with three rubber caps, one partly removed


texts: Vacuum Fluorescent Display (VFD) serial connection ~ Debugging Questions

texts:
I am attempting to display information on a Futaba Vacuum Fluorescent Display (VFD) (apologies for the google-drive link to the datasheet. I lost the original and couldn't find it again). I'm intending on using a MSP430 to do so (though I'm not so far ahead yet).

My intent was to test the device using a serial-connection from my PC, firstly via a COM port, now via a Platronix USB RX/TX thing. However, despite having the correct baud-rate (and trying others to be sure), I keep getting garbled text on the display.
Of course I've no doubt some of the experienced people here could tell me the correct way to archive this, what I'd like to know is "how can I figure out what's wrong?"

I've a tiny hobby budget of tools and not even enough for a second-hand oscilloscope, I've two (barely) decent multimeters, a Very Cheap Nonspecific USB logic-analyser from China, as well as a surprisingly decent stock of PIC, ATTiny, and MSP430 chips, opamps, etc (that I got as a "job lot") from a friend.

Every thread/tutorial/etc I see recommends either using a oscilloscope (that I don't have, and I will buy when I can afford to) or just "a logic analyser will help". Worse I can find very little information on the "SBUSY Handshake" serial communication this device uses.

Thus my question is:

How, given my limited resources, how should I go about debugging the connection to control this device?

Should I consider trying to build other circuits to debug this one?
I considered trying to use the ADC of the MSP to make a "ghetto" USB oscilloscope
Can my PC (with several RS232 ports, that is very powerful by enthusiast standards) be of any help to me?
Should I give up without better tools?

What should I look for with my logic analyser?

Is watching the RX and TX line enough? Should I look on the VFD module itself?
Is there anything "obvious" in the "SBUSY handshake" the datasheet describes that I have missed?

Am I trying to do particle physics using a stone-club and a burning twig?

Apologies if this is somehow a duplicate ~ All the similar questions seem to be more along the lines of "show me how to do this thing." Which doesn't sit well with myself, I would much rather a "show me how best to approach debugging".

I've years in hardware-level C/C++ development, but mostly though PC architecture (rarely does one need to set their own registers and such). And for the last year I've been broadening my horizons with EE - I'm not afraid of hard work, or hard learning (you don't spend years programming C++ if you are). I want to understand what I'm doing properly, and I do appreciate not having the best tools isn't going to do me any favours, however giving up until some point down the road doesn't do it for me. Nor does plug & play shield-things.

I apologise for the generality of this question, unfortunately I don't know where else to go, or how better to phrase it.


texts: Skew angle in squirrel cage induction motor

texts:
The rotor in the squirrel cage induction motor are shorted end to end by aluminium bars; however the are placed parallel at a certain skew angle.

Wikipedia states that "The conductors are often skewed slightly along the length of the rotor to reduce noise and smooth out torque fluctuations that might result at some speeds due to interactions with the pole pieces of the stator ."

However I am unable to understand the above statement.


texts: Contradiction:Maximum Power Transfer and High resistance of load

texts: Whenever we load a circuit, there's a drop from the open circuit voltage \$v_{oc}\$ due to the internal source resistance or Thevenin's resistance\$R_{th}\$. So we need to have  an \$R_{load}\$ that is very large compared to \$R_{th}\$, (i.e) $$R_{load}>>R_{th}$$ so that almost all the voltage drop occurs across \$R_{load}\$ . But according to maximum power transfer theorem we need to have an \$R_{load}\$ that is equal to the \$R_{th}\$ to obtain maximum power transfer. Aren't these two statements contradictory, maybe contradictory isn't the right word, but you get it. So, which one do we need to follow while constructing a circuit.


texts:
When it comes to measuring electron beam currents with a Faraday Cup (or any that will pick up electrons and act as an anode), primarily AC and transient signals, my understanding is that one can:

(1) add an ammeter in series

(2) add a resistor (or capacitor) in series and measure the voltage across that resistor

(3) use a current loop and measure via induction.

It seems like there are pro's and con's to all of these, but I'm wondering, when trying to measure the current in an electron beam in a vacuum, which of the three above methods (if any) is the proper or ideal way to do this?  Where does the impedance of the circuit come into this?  If I want to use an oscilloscope to get time-resolved measurements, how does this come into play?  If the anode/Faraday Cup is biased to prevent secondary electrons, how does this affect things?


texts:
I've attained most of the material I need to build my first power supply. The specs are mostly dictated by the parts I have. My intention is a dual isolated variable output power supply that I can connect in series to give negative voltages.

Below is the "final" draft of the circuit that I'll be implementing. I'll add in fancy pass transistors and capacitor discharge transistors and other things once I completely understand how they work.

I've set up a basic form of this with a single output and no decoupling capacitors or protection diodes on a breadboard and it worked well.

Clarification: I pulled a single bridge rectifier package out of an old TV which is why I have both a packaged bridge and a diode bridge on the schematic. Other than that and the transformers, the circuits are identical.

EDIT: Fixed schematic.

So here are some things I would like to ask:

I'd like to solder the primary of the 500mA transformer to the primary lugs of the larger transformer so I don't have to branch the mains wire to it separately, is this fine?
Is it fine if I stack the two transformers on top of each other?
If I had both outputs connected in series, would I be limited to 1A due to the second transformer only providing 500mA? I don't need that much current but I'm just curious if I'd run into trouble since the transformers are unbalanced. I have a 9V 15VA transformer as well, would that be better matched?
What amperage of fuse should I use? I'm worried about magic smoke....
How damaging would a shorted/max current output be on this circuit?
Any general advice/improvements?

Thanks for your assistance.


texts: Phase shift a data signal by about 200ns

texts: It would be very nice to be able to insert a little "phase shift" circuit into a data line of mine to shift it by one clock - about 200ns - instead of doing it in software which will be difficult and break compatibility with other hardware which runs the same software. The timing will always be fixed. I was thinking of a series C with parallel R but wasn't sure how if it would phase shift; also, it would remove the DC component which might cause issues with the following logic. The solution needs to be as small and as cheap as possible, ideally involving no "phase shift IC", if such a thing exists.


texts: Accurately measure relative intensity noise (RIN) using RF spectral analyzer?

texts:
I'm trying to measure the relative intensity noise (RIN) of a laser using an RF spectrum analyser. It's a fairly common method (outline: How to measure relative intensity noise in lasers) although I wondered if someone more experienced might be able to help clarify some of the nuances of noise measurement for me.

As I understand, RIN is defined as the mean square intensity-fluctuation spectral-density of an optical signal divided by the average optical power. To measure this, we often put the laser into a photodetector, use a bias-T to measure the DC voltage (which is proportional to photodetector current and hence gives a measure of average power) and connect the AC output of the bias-T into an RF spectrum analyszer.

To plot RIN as a function of frequency, the measured RF spectral intensity values are divided by spectrum analyzer resolution bandwidth (i.e. put into dBm / Hz units) and then divided by the average electrical power

$$P_{avg} = \frac{V_{DC}^2}{50 \Omega}$$

This apparently gives a value with units dBc/Hz or dB/Hz.

dB is a relative scale, so dB/Hz makes sense in that we're measuring AC power at a certain frequency in reference to the DC power. However, dBc/Hz is the power referenced to the carrier and I'm not sure what that is in this case. Additionally, some authors present system noise floor measurements in units of dBc/Hz. Is this wrong since in this case there's no carrier? Or is this a system noise floor with reference to the power from the laser being measured?

Finally, in some cases I find that the trace on the RF spectrum analyzer shows harmonics as a series of peaks (EDIT: my laser is pulsed, so the harmonics are at the repetition rate of the pulses, as expected). The levels between peaks is at the same level as the background level (i.e. when there is no signal input). Can we therefore infer that the RIN at these points (i.e. if we integrate from 10 Hz, say, up to the 1st harmonic) is equal to or less than the system RIN? Or would we need to amplify the signal just to ensure we can see it above the system noise level.

This seems a complex topic and perhaps I'm overthinking it, so any tips or pointers / good references would be greatly appreciated!

Thanks


texts: Warning : Actual for formal port a is neither a static name nor a globally static expression

texts:
This is the code I have implemented :

entity tinyMultiplier2X is
Port ( x : in  STD_LOGIC_VECTOR (3 downto 0);
       y : in  STD_LOGIC_VECTOR (3 downto 0);
       ml : out  STD_LOGIC_VECTOR (3 downto 0);
       mh : out  STD_LOGIC_VECTOR (3 downto 0);
       mc : out  STD_LOGIC);
end tinyMultiplier2X;

architecture Behavioral of tinyMultiplier2X is

component ThreeXthreeMultiply
    Port ( x : in  STD_LOGIC_VECTOR (2 downto 0);
             y : in  STD_LOGIC_VECTOR (2 downto 0);
             mul : out  STD_LOGIC_VECTOR (5 downto 0));
end component;

component Multi4x3
    Port ( x : in  STD_LOGIC_VECTOR (2 downto 0);
             y : in  STD_LOGIC;
             mul : out  STD_LOGIC_VECTOR (5 downto 0));
end component;

component FastBin2XDecConvert
    Port ( bin : in  STD_LOGIC_VECTOR (5 downto 0);
         dec : out  STD_LOGIC_VECTOR (8 downto 0));
end component;

signal b,s1,s2,s3,s4 : STD_LOGIC; --THIS IS LINE 59
signal p0 : STD_LOGIC_VECTOR(2 downto 0);
signal p1,p2,p3 : STD_LOGIC_VECTOR(5 downto 0);
signal p4,p5,p6 : STD_LOGIC_VECTOR (8 downto 0);

begin

s1 <= x(3) or y(3);
s2 <= x(0) or y(0);
s3 <= x(0) and y(0);
s4 <= x(3) and y(3);

m3x3 : ThreeXthreeMultiply port map(x(2 downto 0), y(2 downto 0), p1);

p0 <= y(2 downto 0) when x(3)='1' else x(2 downto 0);
b <= x(0) when x(3)='1' else y(0);

m4x3 : Multi4x3 port map(p0, b, p2);

p3 <= p2 when s1='1' else p1;

bndc : FastBin2XDecConvert port map(p3, p4);

p5 <= "101000100" when s2='1' else "100101000";
p6 <= "101100010" when s3='1' else p5;

ml <= p6(3 downto 0) when s4='1' else p4(3 downto 0);
mh <= p6(7 downto 4) when s4='1' else p4(7 downto 4);
mc <= p6(8) when s4='1' else p4(8);

end Behavioral;

ISE creates schematic but a warning exist and I think because of that syntheses report is not created.
the warning is :

  WARNING:HDLCompiler:946 - "C:\VHDL\SignificantSquarer\compactMultiplier.vhd" Line 59: Actual for formal port a is neither a static name nor a globally static expression

and is pointing to the place I have implemented my signals.

any help?


texts:
I am working on a small wireless sensor platform and trying to figure out power supply options.  My power budget is approximately: .2mA constant, ~15mA for .1s every 2-3s, and 60mA for 10s very intermittently (once or twice per hour).  This works out to about 50mAh for the lifetimes I'm looking for, and ideally it would be rechargeable.

I've found some button cells by Panasonic that fit the bill (VL2330 - PDF), but can't find much information on the Lithium Vanadium Pentoxide chemistry.  The data sheet suggests a "continuous standard load" of .1mA, which presumably is just the rate required for the nominal capacity.  Beyond that there's no more information as to maximum pulse currents, derating, or otherwise.  A 1C pulse would be nothing for a regular Lithium chemistry, but I haven't used these before.

Does anyone have experience with these, or know of another direction to look for this kind of application?

Thanks,
John


texts: Lowering voltage in a circuit to spin fan more slowly

texts:
first post here!
[DISCLAIMER] I know little to nothing regarding electrical engineering, I am already in the process of buying a good book to start off, but this issue would need to be solved quickly, hence my question here.
I am in the process of replacing a dead 12V fan with a new one, but the replacement is too powerful (the new fan simply moves too much air for the task). To move less air I decided to lower the fan voltage in order to make it spin more slowly, which I can accomplish with a dc buck converter.
Instead of using a bulky converter, given that I also don't need voltage tuning after I am satisfied with my fan speed, I wanted to go the manual voltage drop route. After some research, I discovered voltage divider circuits, which drop voltages to a desired one thanks to resistors. I tried to drop the voltage to 6V, which I could test with my multimeter, so I connected the fan.
The solution didn't work, and after some more research I stumbled upon this thread which explains exactly the issue that another guy made with the same task: he didn't account for the fan resistance in the circuit.
Now, since I know very little about electrical circuits, I don't really understand the explanation they gave to him and I don't have the tools to solve my issue alone without burning resistors or messing up my new fan, and would gladly like your help :)
Technical details:

DC input: 12V
Old fan: 12V 0.04A
New fan: 12V 0.08A
New fan at lower speed: 6-9V

Sorry if I can't provide more details, I really am this new to electrical engineering


texts:
first time using StackExchange so please be gentle (and pardon my ignorance with wiring and USB standards). I'm trying to create a USB power booster that allows Android Auto to function over my car's USB port, while receiving power from an external 2.4A cigarette lighter charger. I have created a wiring diagram of a design that I think will accomplish my goal, but I want to make sure that I won't fry anything (or that it will even work).

The USB breakout boards are to both increase the longevity of the device, and avoid cutting and soldering the tiny wires inside the USB cables. Also, I don't believe I have to worry about the 56k resistor in the type C cable? In order to improve this design, would it make sense to add diodes anywhere to prevent sensitive electronics from being fried?

I would be happy to provide any clarification necessary, thank you very much for your help!


texts:
I bought an LM2596 board from amazon, and I want to control it's output voltage from an arduino. My plan so far is to replace the trimpot with a network of 2 resistors and a AD5206. One resistor will be in parallel and one in series with the AD5206 to clamp the output voltage between 3V and 11.4V:

simulate this circuit – Schematic created using CircuitLab

The only problem is, from the data sheet for the LM2596:

  When using the adjustable version, special care must be taken as to the location of the feedback resistors and
  the associated wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor,
  especially an open core type of inductor.

If I build this circuit on a breadboard PCB (with solder) and then wire it to the trimpot terminals on the board, will it be too noisy? The switching frequency is 150kHz.


texts: I am doing my FYP in which I am using AD620. I have problem in simulation. Attached is the circuit which i am implementing. Basically I need a gain of 5000. i.e My input should be amplified by 5000 times. I have calculated the value of the resistance as 0.0101194 ohms.When I place this resistance in my circuit and simulate it on proteus, it gives the error that the timestep too small.


texts: Why is "wavelength" used as a unit for the length of an antenna?

texts:
We often refer to antenna size relative to wavelength. For example: a
  1/2 wave dipole is approximately half a wavelength long. Wavelength is
  the distance a radio wave travels during one cycle. (Here)

Why is antenna length measured in terms of wavelength? Wavelength is not even a universal unit or SI unit. Wavelength is not a fixed constant and varies from wave to wave. So why is an antenna measured in terms of wavelength?

There are formulae for calculating antenna length in metres (here) but why are antenna lengths not described in metres in the first place, and why do we have to use formulae to convert wavelength to metres? What is the importance of wavelength as a unit of antenna length?


texts: Current / power measurement using ACS71020

texts:
I am having some hard time in understanding and comprehending the value for ACS71020 current and power measurement. In the manual, rms_avg_1 and rms_avg_2 has been mentioned stating that "The
combination of the two accumulator allows the user to select how long to average for as well as how often the values are updated. The exact time this averages over depends on n (the number of
samples per cycle)". if I choose rms_avg_1 = 120 , wouldn't this be taking average of 120 rms values (hence averaging over 1 sec , given 60 Hz frequency and rms calculation done every half cycle). what is significance for rms_avg_2 ?? Can somebody help on this.
Thanks in advance !


texts:
So I have recently been interested in Radio electronics, and I have been looking around to buy a HAM radio transmitter,but they tend to be very expensive (and you learn nothing by just buying it). So I came up with an idea, I do not know if it will work with what I have planned but that is why I am asking. my circuit diagram will tell you what you need to know.

The computer does all of the modulating with PureData (AM, FM etc.) at 10 KHz and it pipes the signal out into the mixer, where a signal from a signal generator will up convert the signal to the desired frequency. I know i didn't use the correct symbol for the filters but I didn't want to draw out the whole thing.

Would this work? If not what would it take to make it work?

simulate this circuit – Schematic created using CircuitLab


texts:
In my project I am using WeMos D1 R1 to which I have connected I2C display 1602A , infrared LED (for remote control) and DHT11.
As display and sensors are working on 5V I am using voltage level shifter.
Everything is working fine so I have completed my project and decide to power it with 12V power jack. But without success. When I power it with USB power source it works fine. But when I connect it to 12V source display does not work. The boards itself seems working fine as it is connecting to my cloud and sending data.
Does anybody have idea why I have such strange behavior ..? Thanks


texts: Perdiodic thermocouple signal buffer for hot tub

texts:
I'm not exactly sure what to call this technically, which has hindered my ability to research solutions, so I think best just to describe the challenge and see what we can figure out.

I have an older model hot tub, with a thermocouple that provides temperature readings to the control board.  Once it reaches temperature, the heater and motor will cycle off.  After a few minutes, the temperature will drop below the target temperature, and turn the heater and motor back on.  Since the temperature is only fractions of a degree too cold at this point, the heater only runs for about 20 seconds before turning back off again.  This on again/off again cycling I'm sure is causing a lot of undue strain on the system, and is a bit annoying to hear.

What I would like is to buffer the thermocouple signal with some sort of device so as to create a longer hysterisis loop, on the scale of minutes instead of seconds.  The heater is very slow, raising the temperature by only a degree per hour or so, so the responsiveness to the thermocouple signal does not need to be as agile as it is now.

I don't want to modify the control board, so I was thinking to intercept the thermocouple signal, store it, and send the buffered signal which is updated after X amount of time, say 1 - 15 minutes.

Some concerns are:  use lowest technology possible to keep cost down, must be small enough to fit in control panel area (smaller than 1 cubic inch), or an external device that can be put in a waterproof enclosure.

Safety concerns: A fancier version might also keep track of the differential so that if the signal changes more than expected (say heats up more than a degree), the signal would update more often, as overheating could be a concern.  With the body of water involved, this is unlikely, and the heater is also protected by a flow sensor, so this may not be critical.  Other options, only buffer is signal is dropping, as this would only happen when the heater is off and there is ambient cooling.  So, maintain a signal level, and hold highest value for X minutes, replacing either with new higher value and resetting the timer, or until time has expired and reset value to current.

Would be nice if there was some sort of device out there that already does this, or I could build my own with the appropriate components.


texts:
I am part of a team project involving baseball where we would like to determine whether a runner stepped his foot on the base (first base, for example) before or after a fielder (the first baseman) catches the ball, and then make the correct call of out or safe depending on which event happened first.
We know that relative time synchronization is the core of our project, and we also know that we will need 2 modules - one module on the first baseman's glove or wrist (to determine when the ball was caught), and another module on the first base itself (to determine when the runner stepped on the base). We plan on having an accelerometer in the glove module, and a force sensor on the base module.
My question is, what is the best way to wirelessly transmit the timestamps of the event between the two modules? In our scenario, we would like the glove module to transmit the timestamp to the base module (glove=sender, base=receiver), so we need some sort of wireless communication that also has very precise time syncing (less than 10 milliseconds accuracy, preferably).
At the moment, we are looking for some sort of microcontroller or development board that can accomplish this. Current candidates are the CC3220SF and CC2540, but if anyone knows of a better solution, it would be much appreciated.


texts: Given the surface area, volume, and temperature of an IC, can you calculate how much power is dissipated?

texts:
Assume the temperature of the IC is uniform and constant and the surface area and volume are known.

Can you calculate from these values the power dissipated by the IC through heat? If not, what other variables do you need to do this calculation? Can you make a fairly accurate estimation with just surface area, temperature, and volume?


texts:
I have the following component controlling a garage door. I had hoped to wire it directly to my smart home system, which has outputs of 24V 500mA DC. (Output Module)

Based on the following schematic and with my limited knowledge of electronics, I gather that I cannot directly control this circuit. I have no further specifications.

I wish to replace the (non-existant*) pushbuttons T1 and T2 and control them using the relays in my existing system. At the same time, I would prefer something small enough to physically fit in control unit case for the garage door, but I can install a separate box if necessary.

What would be the simplest, most stable way to control this with the 24V outputs from my smarthome system? Preferably without requiring SMD components or a particularly steady soldering hand.

* I only have the circuit, there are no actual buttons attached to the module. The T1 and T2 in the schematic are the intended use of the module - to add two external physical buttons.


texts: What are noise and accuracy improvements that can be made to the classic "error amplifier + transistor" linear regulator?

texts:
simulate this circuit – Schematic created using CircuitLab

A linear regulator is typically an error amp (OA_error), which changes how much the pass transistor Q_pass dissipates in order to bring Vout and V_ref to the same voltage.

I'm curious what improvements there are in topology to this basic linear amplifier design.  For the moment, I'm mostly interested in improvements in accuracy and noise performance.


texts:
The following table represents the FCC radiated emission limits for class A devices at a distance of 10 m :

How do we convert this table for a distance of 5 m?

Edit : There is an approximation in which we can calculate the values at that distance. The new value of the field intensity at 5m (absolute value) = absolute value at 10 m *10/5. I don't know if it is a good approximation or not and also I don't understand how it was derived


texts: Is a resistor trimmer a good idea for adjusting the gain of an op amp circuit?

texts:
I'm designing this circuit to measure temperature with PT100.

R10 must be calibrated to obtain the desired gain.
I have thought of using a resistor trimmer to adjust the gain similar to the following:

Considering that the humidity and temperature conditions are within the ranges described by the manufacturer, is it a good idea to use this potentiometer?
I mean if the internal resistance can change over time, or the screw can move over time.
I once thought I saw it being used in thermocouple conditioning board, but the screw had a glue on it, which I imagine is to avoid the problem I mention.


texts: how to convert a normally closed curcuit to normally open

texts:
Just got a problem at work and I need help fixing it.

I have a water meter that is normally closed and after 5 litres of water has been used it opens that circuit, now the input board that I have been given reads a NC as a read.

So, I was wondering what is the easiest way of changing the circuit to allow me to have a NO circuit going NC.

Thanks


texts:
i recently came across an exercise involving solving for the energy released in a freewheeling diode. This is the circuit:

The problem is that i'm not understanding the current equations for the inductor(L) when the transistor is on and off:

Transistor ON:

Transistor OFF:

This is because when the diode resistance is really small, the constant (L/R) is going to be small as well, thus, not dissipating all the inductor energy in the diode resistance in a cycle. Because of this, in the next period, iL(t0) is going to be larger than 0, and this cycle will continue to go, and allways increase the
inductor current till infinite.

As that cannot really happen in real life, i´m asking where my thinking is going wrong. Thank you guys for all the help.


texts:
I will be connecting a 30A analog DC ammeter in a project soon.  It comes with an external 75mV shunt.  See http://www.amazon.com/dp/B00A4TQY02 for details.

A reviewer stated the shunt was more flimsy than he expected, and my installation will be subject to stresses, so I'd like to substitute it with a better quality shunt.  However, where I'm looking for shunts, I'm finding only 50mV ones.  Eg. http://www.bandc.biz/ammeterloadmetershunts-1.aspx

Will a 20A 50mV DC shunt take the place of this 30A 75mV DC shunt with minimal loss of accuracy?

My understanding is that the 50mV or 75mV is the measurement at full needle deflection, and if 20A creates 50mV, then it scales linearly, so 1A would create 2.5mV, and 30A will create 75mV.  In fact, the gauge even has a cryptic 2.5 mark on the face, I believe to indicate 2.5mV per (1A) mark.


texts: Flush Mounted Threaded Through Hole on PCB

texts:
I am looking for the name of the component in this picture:

Does anyone know off the top of their heads?

I'm working on designing a product that requires 2-56 threaded holes in a PCB, and I need it to be as flush to the surface of the board as possible due to physical size constraints.  The component in the photo looks like it inserts into the through hole and solders in place--that's exactly what I need, I just can't figure out what it is called so I can order some.

Thank you in advance for the help!
Eric

EDIT:
A user on another forum pointed me to the original site for the image:
http://www.robotroom.com/Yummy-Robot-4.html

They say:
"The mounting holes in the PCB were sized to accept threads (0.067-inch hole for 2-56 screws). I’ve been threading holes in PCBs for many years. I assumed that the plating on the interior of the hole would be the material that would get threaded. However, now that I get a close look, I can see that the through-hole plating is lost in the process, and that the threads are made in the garolite substrate. I suspect that the threads in the substrate will have a much more limited life span of having the fastener installed and removed."

So it looks like this indeed just a hole with threads cut by the screw as it's installed.  Thanks for all the help, everyone!


texts: ADC sampling frequency two signal in 1 degree phase

texts:
I have two signal (1.5Mhz) on one degree phase.
I want to use two AD9642 to convert these signals
my question is : what sampling frequency should I use to get a significant result.
regards


texts: How To Properly (and efficiently) Regulate Battery Inputs

texts:
I am trying to design the power hierarchy if you will for a PCB that I'm designing. My choice in battery is flexible but at the moment I have a 3.7V source. I have two main power rails, 3.3V and 5V and I am having trouble picking the correct solution for my project. At first I had:

3.7V battery -> MCP1826 (3.3V LDO) -> TLV61220 (5V Boost)

I heard that chaining these regulators together reduces the efficiency, so I changed my hierarchy to

3.7V battery -> MCP1826 (3.3V LDO)
3.7V battery -> TLV61220 (5V Boost)

I am relatively new to PCB design, I've only done 3 boards so far and I am trying to learn best practice for conditioning the power inputs to my board. Efficiency is key, as my battery powered device needs to last as long as possible.

Is an LDO the right choice here? Its dropout voltage is 400mV so I believe it should be fine to output 3.3V. Should I consider changing my battery voltage? Is there a standard when it comes to powering a 3.3V board?

Also, if anyone has any resources whether they be links, books, PDFs etc about choosing the correct solution to condition the power inputs to a PCB that would be much appreciated.

Edit: After posting, and thinking about possible ambiguities, my system should never draw more than 500mA at a time, it will likely remain around 200mA when active, and a few hundred uA when sleeping, depending on the quiescent draw of my regulators.


texts:
I read about it recently, that the packing density of MOS is more when compared to BJT and hence they are more preferred when it comes to memory design.

Why is it so?


texts:
Converting frequency to voltage using LM 331 is causing me problems.

Frequency range: 0-200 Hz
V.out ref: 3,5v at 100 Hz (3000 RPM)
5,0V at 150 Hz (4500 RPM)
V.cc: 12v.

A sensor picks up the mpulse from a two point cam on a shaft to detect RPM. Rising RPM causes rising frequency.
via the LM331. Increasing frequency creates increasing voltage as it should, but suddenly at a certant level of voltage it drops down to a new level. From this level the voltage increases with the rising frequency again.
Example: Shaft starts a rising RPM from 0 to 4500, the voltage output from the LM331 follows linearly. At f.ex 80 Hz the voltage is 3 V. Increasing to 81 Hz voltage drops down to 1 V. From this level voltage rises linearly again up to the end at 4500 RPM / 150 Hz / 5 volt.
Why this drop down at 80Hz?
NB: I have tried to make this with LM2917, but it will not work at all with this inductive sensor.


texts: Electrostatic in an Arcade Machine (Arduino)

texts:
I set up an arcade machine, which consists of an Arduino, a coin validator, a 12 V adapter, and a PC. It works as expected, when I insert a coin, a signal is captured via Arduino. The output normally stays at 0 V, goes to 5 V when a coin is inserted for a brief period.

The problem is time to time, when I touch the metal part of the coin validator (see picture), it mistakenly sends a signal as if a coin is inserted.

When the metal part of the coin validator is removed, this problem stops.
We use grounded AC socket and connected it to the ground of adapter and Arduino, but it did not solve the problem.

How can I solve this problem, or what might be the source of the problem?
I talked with the seller, and he said our circuit is correct, but he never heard such a problem. It is also possible that wooden part (MDF) plays a part here.

Schematic is below (1K resistor)

EDIT:
I connected only Arduino to PC directly with USB cable, and removed the coin validator, resitor and adapter from the system. When I touch the interrupt pin with a jumper cable, it reads a signal.


texts: SIZING steps and Interpreting Mosfet datasheet

texts:
After reading those

Interpreting Maximum Power of a MOSFET from the datasheet

How to interpret Vgs(th) min/max in a MOSFET datasheet?

https://www.infineon.com/dgdl/Infineon-ApplicationNote_Linear_Mode_Operation_Safe_Operation_Diagram_MOSFETs-AN-v01_00-EN.pdf?fileId=db3a30433e30e4bf013e3646e9381200

what i understand :

clarify coniditons :

fet calculation :

1)Vgs min  :

from zero thermal coeffcient , from gaph : Ids , Vgs , to prevent thermal runaway

2)Vgs max : from datasheet Vgss

3)Vds max :  From Safe operating Area graph , before thermal instability line,        and keep in mind power limit .

project calculation :

1) first model my load , to know its impedance , resistance
2) calculate Vds = Vbattery - Load Voltage drop  , Vd = Vb  , Vs = Vd-Vds

( stated in pdf that Vds depends on voltage drop of load )

3) controlling Vg so it can be variable or constant , connect it to ground so it becomes zero

4) calculate Id ,from Id , Vds graph at known Vgs

Does these steps are correct , fully understood or i miss something  ?

i want to know in Ids ( Vds graph )

is linear region ,  when Vds before V pinch ? and this region correspond to Rds on limit in SOA graph  ?

also does saturation region corresponds to package limited ?

if these are correct what does max power limit corresponds to in Ids Vds graph ?


texts: How can I get FROM and TO times of trig on measure statement of LTSPICE?

texts:
I need to measure the voltage on two signals which have a difference of phase, so in order to do the measure that I need I have to get V1 (t) and V2 (t + delay_between_signals). One way to that is by finding when the reference value occurs and finding the second by adding the time of occurrence + delay_between_signals.

To acquire the time when the reference value occurs I use:

.meas tran tving trig V (vin) = 0 rise = 1 targ V (vin) = 1.5 rise = 1

But it gives me only the time between 0V and 1.5V. I know that is the result that the command is supposed to give, but on the error log it shows the time where the measure starts from and the time where measure ends. Is there a way to get these values?

Or even better, is there a way to get the time (and use it a variable, of course) where the measure occurs on the .measure spice directive?

As requested, here is the original circuit, the graph and the directives used:

It is hard to see but there is a difference of phase between the V(vout) and V(vin) waves. Since I want to measure the gain, V(vout) must measured not in the same time as V(vin), but in t + delay_between_signals.


texts:
I run a DC analysis of a buck-boost converter to generate the steady state waveforms of different currents and voltages. I am interested in the inductor current and voltage and capacitor current.

The circuit I have used to generate the waveforms is depicted below with Vin is a PWM signal.

The waveforms generated are shown below

If we look closer to the waveform of VL (In red), we notice that VL is decreasing during the ON Time. But since it is connected in parallel to Vin during the ON Time, I expect to get a flat inductor voltage during this time. Why do I get a decreasing voltage?


texts: I want to build a DC powered computer, what are the gotchas, where are the parts?

texts:
Google builds its servers with a Battery in the box so that they don't need a UPS.  I'm wanting to do the same, but I'm wondering what all the gotchas might be for doing this, and where I'll find the components to put it all together.

I'm wanting to figure out how to eliminate the DC -> AC -> DC conversion (and all its losses) and just run the system off a DC power supply with a battery in place of the current ATX power supply.

I'm thinking a standard ATX power supply to give me the 12 volts for normal operation, then a kick over onto a gel cell battery when the power goes off, eliminating the UPS.  I'm looking for ideas on how to do this economically using off the shelf parts and whatever amount of soldering needed to make it work.


texts: signal propagates in bending transmission line (unequal length between signal path and return path)

texts: Suppose I have a square wave signal generated from a signal generator and its outputs are connected to the two terminals of a paired PCB traces (left side of the picture below). The other end of the paired PCB traces are connected to a oscilloscope. V+(I+) and V-(I-) should arrive the red dash line at the same time according to transmission line theory. However, the outer transmission line is longer than the inner transmission line because of the bend, thus, V- travels a longer distance than V+, so should I see a the two signals appears on the oscilloscope in different time with V+ arrives at oscilloscope earlier? I don't think this is right, but I cannot think of a reason why. My gut feelings tell me that the two signal should arrive at oscilloscope at the same time, but I cannot explain it in physics. Can anyone help me to explain it? Thanks


texts: Reading values on continuity test but there is no beep

texts:
When checking traces of my PCB I realized that checking continuity between one of the output trace and GND some values appear on multimeter screen but the buzzer does not beep.

On the Vcc trace there are two different capacitors. Does that depend on these capacitors?


texts: Combining and Charging multiple Lithium Ion Battery Cells (3.6 V or 3.7 Volts)

texts:
1] Voltage: 3.6V or 3.7V
Are all 18650 lithium ion battery cells 3.6 or 3.7 voltsor or are there different voltage Lithium Ion cells in the market as well?

2] Possible Voltage Shortage?
Do all 3.6/3.7V li ions work the same standard way with a + a - and a T or do they really differ? What does the T stand for? Temperature sensor?

3] Physics Voltage Reason
Whats the reason for the 3.6/3.7 Volts per Li Ion Cell? I never saw a 3.0V or 5 Volts... Curious...

4] Parallel Charging of many Li Ion Cells
I was thinking of putting two or four of those Panasonic/Sanyo 18650 Li Ion cells in parallel, soldering together from the instant the are new, that way giving me lots of mAhs. Can I use the same Li Ion charger that was made for charging just 1 cell, and let it be in the charger for longer time?

5] Charging Wiring... How?
I found a nice small cheap charger about 30~40$ called Turnigy Accucel-6 (there is also an Accucel-8 for double price and double weight). Could I attach the + to + of all the cells and the - to all the - poles of the cells without needing any extra in-between-wiring?


texts: Effect of switching supply on a Hall effect sensor

texts:
I have a Hall effect sensor and an electric motor, with both the sensor and the motor powered from the same supply. I'd like to use PWM on the supply to vary the speed of the motor. The sensor and motor aren't separable.

However, I've been told that Hall effect sensors don't respond well to being supplied with a PWM-modulated supply, and its output might not allow reliable speed readings for the motor. I haven't been able to find anything online saying this, but the resources I have found on Hall effect sensors all say that the sensor should be given a "constant voltage supply."

Will using PWM to vary motor speed make the Hall effect sensor unreliable? If so, would using a high switching frequency and a filter on the sensor's output (to remove noise from the high switching frequency) solve the problem?


texts: Using a UA741 IC as sensor for an existing AA LED

texts:
I am trying to know if an air conditioning is ON/OFF (Daikin with only Wired Remote Control). I want to read its LED.  The circuit is fed by a simple 17.8 V two wires from the machine.  I've read the base of the LED respect to the GND, and both extremes are at 6.13 V when OFF and at 1.9 V one over the other when ON.  I don't dare to interfere the circuit at all, but simply tell the state to a Shelly 1 relay to expose it into a HomeKit system.
In my really poor knowledge about electronics I understand 741IC, yet a bit old, could make the work, as it doesn't drain any current from the Vin and could simply connect the pin 7 (V+ pin) with pin 6 (Output pin) which I would directly connect to the SW pin in Shelly 1.
So the final scheme would be:

Would it interfere, could damage the AA circuit?


texts: Center-Aligned PWM when to trigger current measurement STM32F4

texts:
I try to implement the Center-Aligned PWM on an STM32F410 and the current measurement triggers from the PWM generation timer. I have some trouble in finding the right measurement point for my currents, because somehow I'm never able to get all three phase currents in full resolution. The Center-Aligned PWM works fine as this image shows:

(UV-Phases Center Aligned PWM)

I first tried to synchronize the measurement when all low side MOSFETs are open, since this makes the most sense to me, because I measure at the low sides. This is the result:

(Low Side Currents UVW in RGB)

(Osci Triggering Measurement in Blue)

From the V Phase, I always get only half the wave correct. It has nothing to do with saturation, the driver is able to measure up to 7A per phase, where here is only around 700mA applied. Also the ADC goes not in any saturation at all.

Then I tried to measure when all the high side MOSFETs are on, but this is even worse, but expected:

(HIGH Side MOSFETS ON)

(Osci High Side Triggering Measurement in Blue)

Here can be seen, that the V-phase is measured correct, but this time U and W have only half the resolution.

Has any one an idea what is wrong here, that I cannot measure the currents of all three phases? The Center-Aligned PWM works fine as the first image shows, so all phases are centered correctly. Also the measurement triggering is perfectly synchronized. Do I need to measure at a different point?

**Edit: **  A solution I just found is to assume Iv = -(Iu + Iw), this seems to work pretty good. Is it possible, that not all three phase currents can be measured simultaneous?


texts: Which of these marks signifies Pin 1 on the STM32F (LQFP64)?

texts:
I'm using the STM32F105, in a LQFP64 package. It has two circular markings, on opposing corners of the IC.  This picture is for a different ST ARM, but the markings and silkscreen are similar:

The larger mark in the upper-right of the picture has a flat bottom, whereas the smaller mark in the lower-left is slightly concave.  This package doesn't have an exposed pad, so there are no clipped corners underneath.

The datasheet only mentions one mark:

and I haven't found any other package documentation that mentions it.

Does anyone have a clue for me?

Update:

The project is completed and the answers are correct. Pin 1 is the smaller, concave mark in the lower-left. Don't forget to upvote the good answers!

Interestingly, I've since purchased another batch of these chips and they only have the one mark.  Thanks, all!


texts:
Does someone recognize this microcontroller?

It has 100 pins, and looks like LQFP package.
UART is 5V out, so it's not 3v3 IC.
It also has 2 CAN channels.

https://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1005
gives ATSAMV70/71 but they fail 5V criteria, so I don't think it's Microchip.


texts: How much power does a GPU actually use when only doing PCIe I/O, or only compute?

texts:
I hope this is the right sight to ask such a question, if not please be kind and direct me elsewhere.

I have some discrete GPU with a TDP figure of X watts. Now, sometimes the GPU does

Only computation (executing kernels)
Only PCIe transfers (host-to-device or device-to-host copying, or both kinds of transfer on certain cards),
Both compute and PCIe I/O
Idling

How much of the stated TDP can I expect the card to use in each of these scenarios?

Notes:

If your answer is manufacturer-specific and GPU generation-specific, I'm interested in NVidia Kepler 700 series and NVidia Maxwell (705, or the 900 series). Information about other cards will also be appreciated.
If the answer is "it depends", typical figures under assumptions are also good.


texts: How do I select the best transformer/regulator strategy?

texts:
In my project, I wish to power a Raspberry PI 2 board and a small TV display like this one (http://www.adafruit.com/products/913). The RPi will draw around 1A-1.5A at 5VDC and the spec for this screen says 150mA at 12V to 250mA at 6V.

As I'm somewhat a beginner, I'm hoping to take a 'standard' AC/DC power supply and adjust the voltage up or down to suit my needs but I'm not sure what the best strategy is? I am trying to ensure I can use a fairly generic commodity power supply and keep the costs of components down as much as reasonably possible.

I think these are my options:

Option 1 Use a 5v 3A DC PSU and step-up the voltage to 6v using something like an LM2621 step-up converter. These apparently are 90% efficient typically and a pretty cheap.

Option 2 Use a higher voltage DC PSU and step-down the voltage to power the RPi. A linear regulator will be inefficient (and hot) and a switching regulator is more expensive.

My questions are two-fold:

I prefer option 1 because it seems cheaper and more efficient. Are there any other fairly trivial options I have not considered or are my conclusions sound?
Is there any benefit to using a higher voltage in the display?


texts: Increasing the range of a UHF RFID reader

texts:
Okay, so I've got an UHFReader18 UHF RFID Reader from China, which can be seen here:  http://www.aliexpress.com/store/product/Popular-800mm-UHF-RFID-Desktop-Reader-6B-6C/413622_598715812.html. The unit I have is not the exact model shown on the website, since my unit's antenna is extended outside of the main body. Here's a picture:

The red bar is the antenna.

I've tested the device using the provided RFID cards, and using the provided software sample I was able to reliably read the RFID cards at a range of 30-40 cm. However, I'd like to know if it is possible in any way to increase the range of the RFID reading at one point or area, at the cost of minimising its coverage. The reader is intended to be used in a factory setting.


texts:
I connected the collector to positive (through a 330 Ohm resister) , base to positive (through a 10k ohm resistor) and emitter to an LED which I connected to ground . I measure with a multimeter the voltage drop across LED ; by first pulling the LED from the ground {I'm going into pointless detail to leave out no detail because what happened is strange) and connecting the loose end of the LED to the one of the multimeter leads and one multimeter lead to the ground . I got a voltage drop of 1.2 (as expected). Now I reconnected the LED to ground and touched the multimeter leads to the emitter and ground , here is the kicker , I still got a voltage drop of 1.2 . How is there a drop before the LED ? What happeend ?
I'm sorry that I have no picture for proof , I'm not sure how I can do  it but I'll try .

EDIT : It is also important to note that when I removed the LED and connected the emitter directly to ground there was no voltage drop


texts:
Edited in my LED module current requirements, fixed needed resistance and added a schematic to better illustrate what I'm trying to do. Thanks Tom and asmydolf.

Okay, it might seem like a dumb thing to do, but I'd like to light up a LED at the end of a conductive wire, which in turn I would like to heat up. The conductive wire is Nitinol, which is used to move the LED to a new position, hence the reason for driving them together. The LED is right now a module, rated 12V and 0.36W, so it should require 0.03A, and the Nitinol wire is 0.1mm Dia., and 30cm long. I made some calculations, and to heat to Nitinol wire in 5 seconds I need 0.35A, 36 Ohm, which will create 4.4W - meaning a reasonably priced resistor can be found for that. I thought of running both the Nitinol wire and the LED in parallel, as I hope my sketch will show. Alas, just running the LED module at the end means no heating, and when I place a potentiometer across the LED terminals to divide the current I either short out the LED while heating the Nitinol wire, short out the wire while driving the LED, or getting the potentiometer burning while trying to do both...

simulate this circuit – Schematic created using CircuitLab

Anyway, any and all help on the matter will be greatly appreciated, I'm trying to help my wife's project off the ground in between my exams, and I was never really good with electricity.

Thanks,
Uri


texts: VT pin flashing LED on WT12D RF receiver module even with transmitter not enabled

texts:
The VT pin on the decoder side (signifying a valid transmission) flashes intermittently (sort of imitating a square wave pulse)

This happens without me making any change in the circuit - no address change, or TE' (transmission enable, which I have permanently grounded).

I put together a circuit that follows the schematic:

(Source: https://electrosome.com/wp-content/uploads/2013/06/ASK-RF-Transmitter-600x823.jpg)

on the encoder side and

(Source: https://electrosome.com/wp-content/uploads/2013/06/ASK-RF-Receiver-600x557.jpg)

on the decoder side.

I'm using a Hi-Waote 6f22M battery power source, in case it is important.

Any reason you guys could suggest as to why it's not permanently high on the VT pin?


texts: Low Pass Sallen-Key filter has weird response in bode plot

texts:
I have the following circuit in Multisim and am getting the Bode plot at the bottom. Could someone please explain to me what is happening?

The AD8651 is listed as having a 50MHz bandwidth. Why is it that it goes astray at 17.4kHz?? I think it might be something wrong with my design but I am not quite experienced enough at this to narrow it down.


texts:
I have to design a BJT multistage amplifier to meet a specification provided by my professor. The first stage is to be a differential amplifier, and the second stage is to be a common collector amplifier. However, the first stage won't be a differential amplifier in the traditional sense; it's to be thought of as a common collector fed into a common base. Overall it's common collector -> common base -> common collector. See the circuit below.

simulate this circuit – Schematic created using CircuitLab

The capacitor C4 is to short out the 10k resistor at AC, so the left half of the differential amplifier acts like a common base. The power supply does not have to split, I just found it to result in a higher gain that way.

A couple other restrictions imposed on the design by my prof:

-Can only use three transistors; two for the differential stage, and one for the common collector output stage. They can be NPN or PNP.

-Achieve as much gain as possible. Aim for at least 45dB.

-For each transistor, add a 1nF capacitor from the base terminal to the collector terminal. This is to simulate the effects of high frequency while only using a frequency of 10kHz.

-Output stage is to drive a 1k load.

-Add a 10k resistor to the input of the first stage. This represents the output impedance of a previous stage.

Mainly there are two challenges: 1.) Achieving max gain out of the amplifier 2.) Making sure the gain is effective at the frequency of interest.

So essentially the things that can be altered are the Q-point currents and voltages, and the input and output impedances of each stage, which is tricky because they are not entirely independent of each other.

My understanding: Each stage should be designed to have the input impedance as large as possible, and the output impedance as small as possible in order to minimize loading effects. The two common collector stages should be designed to have gain as close to unity as possible. The common base is the "meat" of the amplifier, in that it is the only source of gain.

There must be a maximum value of obtainable gain, and there must be a way to find it. I'm just not sure where to go from here. I came up with a design that can get approximately 35dB of gain, but it was more a matter of messing around with values in SPICE, so I don't have a good explanation of why it works or how to improve it. I have a decent understanding of basic amplifiers, but was never really taught how to design. Any advice is highly appreciated.


texts: MSP430FR4133 is missing PxSEL1 register?

texts:
Hi there fellow MSP430 programmers!  I'm new at this so maybe you can help.

I'm running into trouble configuring the MSP430FR4133 PxSEL registers.  In the MSP430FR4xx Family User's Guide, it is stated that the pin function select is controlled by TWO 8-bit registers, PxSEL0 and PxSEL1, to control primary/secondary/tertiary functions:

The problem is:   I can only find and access PxSEL0 on all ports, and PxSEL1 seems to be totally absent in both the msp430fr4133.h header definitions as well as in CCS's register browser:

I'm confused as to why the FR4133 version of the device doesn't show the PxSEL1 registers in both the main header definitions or the register browser.

This poses a problem if I wish to configure pin 5.1 for the UCB0SCL function, because I can only set one bit in P5SEL0 and the other bit in P5SEL1 is ... either nowhere to be found, or I've got a case of the misunderstandings.

Any clue as to what is going on?  Thanks!


texts: How to contol the height of blade in a vinyl cutter machine?

texts:
I have a machine that has 3 axis x,y,z.  The machine is a vinyl cutter.

The x and y axis are stepper controlled, but the z axis is a coil so my question is how does the manufacture control the z height.

I need to program it using an Arduino, the machine uses an IC marked A3955 to control the height.


texts: SPICE Modeling voltage during battery discharge

texts:
I am trying to create a spice model of a battery discharging into an LED.

I would like to model the charge remaining (Ah) throughout the discharge and as I understand it this can be acheived by reading the voltage across the terminals of the battery.

I would like to model the discharging of the battery and view the voltage across the terminals over time.

I am just starting to use spice models and have been playing around with pspice, ltspice and now circuit-lab.


texts:
To create a band-pass filter using an RLC-circuit, i drew the following circuit (assuming R is given as 120):

The corresponding transfer function is
$$
H(\mathrm{j}\,\omega)=\frac{120\, C\, \mathrm{j}\, \omega}{1 + 120\, C\,\mathrm{j}\,\omega + C\, L\, (\mathrm{j}\,\omega)^2}
$$
I know it is possible to find the corresponding L and C values to create a band-pass filter at resonance, giving a peak at the resonance frequency and -40dB/dec decrease at higher and lower frequencies in the bode plot. In that case the denominator of the transfer function has 2 complex roots.

My question is: is it possible to find L and C values to create a band-pass filter without resonance. Thus with 2 real roots for the denominator. Since \$\omega=0\$ is a zero of the transfer function, I would assume there is an increase of 20dB/dec until reaching the first pole. Then a steady part and afterwards a decrease of -20dB/dec starting from the second pole.

I did some quick calculations and found example values for C and L (see the circuit picture). I drew the circuit in LTSpice, did an AC-analysis and got this bode plot:

This is exactly what I was expecting. However, since I can't find any resources about this configuration of RLC-circuits (on the internet and in my textbooks), I'm not sure this is actually correct. Is this circuit a real band-pass filter, or just some look-a-like? And is my statement that this circuit is not in resonance correct?


texts: Some questions about a comparator circuit used as a buffer

texts:
I want to hardware-trigger a module from a separate remote data-acquisition system's analog output. The module's hardware-trigger input is optically isolated to prevent grounding problems. And the module's manual mentions the following as well:

And the data-acquisition system's DAC analog output can max source 5mA.

It seems to me that if I can send a single pulse voltage signal with the amplitude between 5V or 10V to the module I can trigger it. But since the current might be an issue for the DAC, I decided to use a buffer for the trigger signal.

So the following circuit buffers the pulse signal with providing higher current.

R8 is for pull-down when the DAC's connector is unplugged.

R9, D1, D2 are there for reverse voltage protection.

C1 might help for high freq. noise

R1, R2, R3 sets the reference with a hysteresis around 0.5V.

R7 and C2 is to mitigate noise at Vcc of the comparator.

The rest is open collector resistor and PNP transistor to ease the opAmp output current. Here is the sink current info of the comparator(6mA min, 16mA typical value):

Below is the plot by LTspice showing a red 5V input pulse and the blue voltage at non-inverting input Vn(indicates the hysteresis). Other green plot shows the output current of the comparator.

I want to use this circuit for 5V to 10V pulse inputs to obtain a trigger voltage around 12V. It seems in simulation it works for how I want.

1-) But I don't want to cause a delay more than 10ms between the input and the trigger. How can I quantify it? I heard that a large hysteresis can cause delays. Is the best way to check from simulation?

2-) I cannot find the max current that the comparator can source in data-sheet. That's why I used a transistor at the output. Can one help me if he can find/see that?

3- Is there anything fundamentally wrong with this circuit.


texts: Voltages in a circuit with two transformers

texts:
Consider the circuit with two transformers in picture.

simulate this circuit – Schematic created using CircuitLab

I tried to simulate it and I get that on CH1 I see V1 transformed (i.e. V1 times the transformation ratio of T1), while on CH2  I see approximately 0 Volts!

I tried for many values of R and V1 but the results it's always the same, nevertheless when I tried this on a real circuit I saw that both on CH1 and on CH2 I had nonzero sinusoidal voltage (and the difference between voltage was V1 times the transformation ratio).

I do not understand why V on CH2 should be 0 volts at all.., can't current flow in the loop where R is placed? Is this related to the fact that the circuit is open after the second transformer?


texts: I was going through a 5mm blue LED data sheet and found this diagram in it. Couldn't figure out what it is.


texts: LED Bike light - blowing at high speeds?

texts:
My bicycle is equipped with a about 5 year old hub dynamo and a LED front- and backlight.
I suspect the dynamo is a DC-generator though this likely may be false. But if its true, it would mean that with rising rpm I have rising voltage as well, which probably could cause some trouble at really high speeds.

My question is: Would going fast enough on my bike make the LEDs (or other parts of the lighting system) blow? What are feasible ways to test if the dynamo output voltage is limited?


texts: Where to put regulator when separating analog and digital grounds?

texts:
I have an STM32F051 MCU, A XBEE module and an analog sensor I want to read its value using my MCU. I've read (and also practiced in action) that to have a precise ADC readings(which is important for my application), you have to separate analog and digital grounds, like this figure:

I have two questions:

Where should I connect the regulator ground? AGND or DGND? Why?
Where should I choose as a star point for connecting two grounds? Regulator or near the MCU?

Here is what my MCU power pin connections look like now(I've assumed the regulator as the star point, So I've connected the MCU to the AGND):


texts: How to design a switch for my integrator?

texts:
I have an inverting integrator

that integrates the input signal (green) into the blue signal.

If I do nothing, the integrator output will go down and down and down... I don't want this. I want to reset my integrator back to ~9V when the second green pulse comes.
With some knowledge in digital circuit, I already produce the "switch signal" (green narrow pulses) as shown below.

Finally, I need to build a switch circuit that resets the integrator (basically C1) every time it sees the green narrow pulse. How could I build this switch circuit?
My Attempt
I tried using an npn BJT who is on when V_{BE}>0 and V_{BC}>0. However, this is not working, maybe because my green pulse is only 1V (from digital circuit) and the integrator output is as high as 9V. There is no way whereby  V_{BE}>0 and V_{BC}>0. Also, I feel this way, the switch circuit is somewhat "disturbing" the integrator.


texts:
I'm building a simple audio mixer. It's going to be running from a USB power supply, so I'm using a TLE-2426 to derive a 2.5V reference voltage for the summing op-amp.

My question is, what do I connect to the sleeve pin of the TRS input jack? My first thought is to use the 2.5V reference as the ground, but then I thought that if the other component connects the cable's sleeve to its chassis ground, then suddenly there's a lot of current flowing through the cable. So, should I actually use the 2.5V reference as ground, or the actual 0V rail as ground? Should I include a decoupling capacitor, and if so, what size?

simulate this circuit – Schematic created using CircuitLab

Thanks to Transistor for pointing out the circuit schematic editor I completely missed, so I can illustrate what I'm trying to do. My original question was whether to connect Point #1 to Point A or Point B, but as I created the schematic, I realized that I don't know about Points #2 and #3, either. I think, based on Transistor's answer, that #2 should go to B and #3 should go to A, am I right?


texts:
Simple doubt about EMC directive on page 15.

Should I use the varistor, cap and toroidal core on non UTU model? I want it to be compliant with safety directives, but I dont want to interfere with function and know if I can cut the BOM on those components.

Main use will be HPS lamps and similar loads.

Product https://www.mouser.es/ProductDetail/Omron-Automation-and-Safety/G3NA-210B-UTU-DC5-24?qs=sGAEpiMZZMsLmE2CU4Kkzy5Et0ECO1IY

Circuit mentioned
https://imgur.com/a/FE6v7Ud


texts: Why is daisy-chaining surge protectors not recommended?

texts:
I know MOVs inside surge protectors degrade over time, but I also see manufacturers putting notes on the box that the protection warranty is void if I daisy-chain surge protectors.

So questions:

Is there an estimate of what the life of a MOV is if:

i. it has never faced a surge before?

ii. it has faced some surges before?
I'm buying surge protectors with indicators showing the effectiveness of the surge protection: how do they work?

How does that indicator know if the surge protection is still effective?
Why do manufacturers discourage daisy-chaining of surge protectors?

I'm assuming most off-the-shelf/commercial "computer"-grade surge protectors use MOVs.

I was interested in finding out if the MOVs are connected in parallel to the AC output of the surge protectors?

If so, how do MOVs connected in parallel interact (something like connecting resistors or capacitors in parallel or series changes their values)?


texts:
I'm exploring my first arm device the lpc1343, I'm using VIM and ARM GCC, I have managed to light an LED but to blink it, I will need to startup the clock and pll, right now I can't find the right sequence for this in the user manual.
Where can I find the basic startup sequence for clock and PLL for lpc1343 ?

So far I came up with the following not working sequence :

void InitSys (void) {
    InitCpu();
    InitPorts();
}
void InitCpu (void) {
    PDRUNCFG |= 0x00000020;      // SYSOSC_PD = 1 -> System oscillator Powered Down
    SYSOSCCTRL = 0x00000000;     // Oscillator is not bypassed, 1 - 20 MHz frequency range
    PDRUNCFG &= ~0x00000020;     // SYSOSC_PD = 0 -> System oscillator is Powered
    InitPLL();
    SYSAHBCLKDIV |= 0x00000001;   // System Clock Divide by 1
    MAINCLKUEN &= ~0x00000001;    // No change
    MAINCLKSEL = 0x00000003;      // Main clock source select register -> System PLL clock out
    MAINCLKUEN |= 0x00000001;     // Update clock source
}
void InitPLL (void) {
    PDRUNCFG |= 0x00000080;         // Set SYSPLL_PD
    SYSPLLCLKUEN &= ~0x00000001;  // No change
    SYSPLLCLKSEL = 0x00000001;      // System oscillator
    SYSPLLCLKUEN |= 0x00000001;     // Update clock source
    SYSPLLCTRL = 0x00000025;        // FCLKOUT = 72 MHz /// M div = 6 / P div = 2
    PDRUNCFG &= ~0x00000080;        // Set SYSPLL_PD
    while(!(SYSPLLSTAT & 0x000000001)){}  //If 1 -> PLL locked
}


texts:
Let's look at the datasheet for an MMBT3904, just for example. The absolute maximum section talks mostly about maximum voltage differences, and a single current limit - the collector current.

I'm used to using these, and similar BJTs as saturated switches. And I get that once you have a base current that is sufficient that the Hfe causes the collector current to max out... I'm good to go.

When I was a kid, I didn't know this stuff as well as I do now (which says a lot), so I tried setting up saturated BJT switches with no base resistor. So I'd pump way, way too much current from the base to emitter and blow it apart. I'm older and wiser now.

But the question still stands: From the absolute maximums on the datasheet, how do I calculate what is effectively the absolute minimum base resistor? That is, the absolute maximum amount of base current before the blue smoke is released?


texts: Non-inverting-Amp bias current: understanding output error

texts:
I have a book (Tietze, Schenk: Electronic circuits) that shows this equivalent circuit of a non-inverting amp. \$I_B\$ is the bias current, \$I_o\$ the offset current (difference of bias currents).

The output is given as
$$V_o = \left(1+\frac{R_N}{R_1}\right)V_i + I_B\left(R_N - \frac{R_g(R_1 + R_N)}{R_1}\right) + \frac{I_o}{2} \left(R_N + \frac{R_g(R_1 + R_N)}{R_1}\right)$$

Edit & 2. Edit

Although I somehow understand the formula, I do not understand how to derive the parts of the equation with \$I_B\$ and \$I_o\$, see below

I tried to do the math but maybe something with my initial equations is wrong.
I tried the system of these equations
$$ V_p = V_i + R_g I_B$$
$$ V_n = \frac{R_1}{R_1+R_N}V_o + \frac{R_1 R_N}{R_1 + R_N} I_O + \frac{R_1 R_N}{R_1 + R_N} I_B$$
$$ V_p = V_n$$
which gives something similar, but not the same:
$$V_o = \left(1+\frac{R_N}{R_1}\right)V_i + \frac{R_1 R_g - R_1 R_N + R_g R_N}{R_1}I_b - R_N I_O$$


texts: I'm trying to fit two sensors in a shoe each (such that each shoe has one sensor). their purpose being to calculate the stride length of a person, as a person takes a stride, the distance between two sensors will "peak", thus indicating a stride. However, I don't know what is out there or what sensors to use. I was thinking of using RFID 433 MHz sensor, or ASHR, but not sure how to proceed. Thanks.


texts: Getting shocked because of floating ground on psu

texts:
Angus from makersmuse explains here how he got shocked from a printer with floating ground.

https://youtu.be/v1OuYg7AJjw

I don't really understand his explanation.

He basically says that if you don't ground the printer properly it wil shock you if you touch it because the ground wire, and thus the printer will be hot?

But why is there voltage on on the pin in the first place?

Does this mean that if I plug my printer in to an ungrounded wall plug and touch the case while I'm grounded I will get shocked?


texts: No Miller effect in differential amplifiers

texts: Why is there no Miller effect in differential amplifier and cascode circuits? (from the book Art of Electronics)


texts: What software do you suggest for visualizing sensor data on OSX. For example bunch of sensors connected to Arduino and sent to MacBook via serial. Realtime graphing preferred but would be interested also in log-and-graph-later solutions.