texts: MCP16301 fail on power up - Vin shorted to Vout

texts:
I have designed a step-down converter PCB (4-layer) with MCP16301. It converts voltage from 24V to 5V.

When I connect it to power source and then connect a 100ohm resistor (50mA@5V) it works normally.

But when the load is applied before I power it up MCP16301 dies instantly and shorts Vin to Vout (Vout is 0.5V lower than Vin - probably a voltage drop across internal mosfet).

No other components are damaged. When MCP16301 is replaced it works again. I've already destroyed 3 of them.

Schematics is an exact copy from datasheet:

Components:

input cap 10uF 0805 35V

inductor 22uH

boost cap 100n 0603 50V

schottky diode 60V 1A

1n4148 diode 100V 300mA

PCB layout (gnd plane hidden):

with ground plane:

I've been troubleshooting this for a couple of days so any ideas/solutions would be greatly appreciated.

Note:
PCB was powered by connecting an alligator clip (not a proper switch) and there was a small spark. Power source is a Chinese lab power supply.

Edit:

I followed Andy aka's advice and added a zener diode (30V) but the chip still got fried.

Luckily i was able to get an oscilloscope this time. Here are the photos (because of stackexchange link limitation i can't post clickable links)

(blue - inptut voltage, yellow - output voltage; 10V/div)

There is a 2us 60V spike at the beginning (despite 30V zener diode) so I guess zener diode is not fast enough?

Edit2:

I added an electrolytic capacitor (100uF, ~0.5ohm ESR) as suggested by @Peter Smith. It now works and the voltage is also a lot cleaner (ignoring some high frequency ripple):


texts: Using Audio Input of computer as Oscilloscope for Hobby Electronics

texts:
I just discovered an app for mac that uses the Audio Input of the computer and the AD-converter in the sound card as an Oscilloscope.

First, I was thinking this can't work... but theoretically, it's a great idea! I know it can only measure for frequencies starting from ~20 kHz, but if you need to measure MHz, then it's just fine.

my question is: How reliable is this technique, independent form the Software? If you build a nice adaptor with overvoltage protection (max 2V), then I suppose there is no danger for the sound card on the computer, right? Any other experiences?

Thanks


texts: Can 12.74V (iso 12V) result in a PC not booting anymore?

texts:
My desktop PC doesn't boot anymore (no leds, no fans, ...).
Last week, we could get it started by toggling the power switch a couple of times
but this doesn't help anymore.

I tried

replacing the 3V CMOS battery and resetting the CMOS
visually inspecting the capacitors
measured the voltages on the 24 pin ATX connector of the PSU

I measured 12.74V on the 12V pin which falls outside the 5% tolerance.
(all other pins measured well within the tolerated ranges).

Can this 12.74V be the root cause of the not-starting?


texts:
In the left hand side part there is a diode in series to parallel RC network. And in the right hand side there is a zener diode in parallel with series RC network.

How do these sub circuits operate? Is the second one (on the right) used for filtering electronic noise?


texts: Regulating square wave signals of varying amplitude

texts:
I'm looking to capture the output of some Hall Effect sensors on a microcontroller/SBC, operating at a logic level of 3V3.

The Hall Effect sensor voltage range could be 0-5V, 0-9V or 0-12V. What is the recommended means for shifting a variable voltage to 3V3? Would a simple LDO regulator (such as the LM2936-3.3) be sufficient? Would a comparator (such as the LM339) be another option? The square wave frequencies will be in the range of 20Hz - 400Hz.


texts: How did we separated/broke down this phasor expression?


texts: Is it possible to use USB port with a transmitter to control a robot

texts:
I have a project in mind that works as a robot accepting input from the computer through a male connector.

I have seen the circuits that use a wire system to connect to the robot. But is there any way to build a transmitter in the size of a USB modem and use it to transmit the signals.

Will it work or damage my laptop. Never tried connecting such wireless stuff to my laptop, so a bit nervous


texts: How to make a landline phone ring periodically

texts:
How can I use a capacitor to ring a landline phone over and over again. I assume I need to develop such a circuit like below with a cap placed on one of wires. I think the cap would charge, and when decharging, it can ring the landline phone. If such a scheme is possible, does anybody know how I can calculate the needed capacitance for the cap.

simulate this circuit – Schematic created using CircuitLab


texts: Friends, I did this once but don't remember the detail. A very sensitive circuit which switches a relatively heavy load. I used a 7555 IC to momentarily blank out any ripple or instability caused by the switching. It was feedback from the 7555 output to another pin on the 7555. A very useful circuit, but I have lost the diagram. What was it?


texts: Microcontroller output override another signal, protect uC when powered off

texts:
I have a digital signal from somewhere else and a microcontroller. The microctontroller can set it's output pins to be high, low, or high-Z.  If the uC pin is high or low, I'd like the output to match it. If the uC pin is high-Z I would like the output to match the other signal, and ideally the uC can read it. But I'd also like to be able to turn the microcontroller off completely, and not have it damaged by an overvoltage on the pin. Expressed as a table:

| uC Power   uC out   Ext in | output |
+----------------------------+--------+
|    H         H       -     |   H    |
|    H         L       -     |   L    |
|    H       HighZ     H     |   H    |
|    H       HighZ     L     |   L    |
|    L         -       H     |   H    |
|    L         -       L     |   L    |
|    -       HighZ   HighZ   |   L    |
+----------------------------+--------+

The external input could come from a few different sources, most likely +-12V or 0-5V logic. I would like to be compatible as wide a range of bench test equipment and PLCs etc as possible without adding too many more components.
The output goes to a typical CMOS digital input. I may add a Schmitt trigger.
The microcontroller can source or sink about 10mA on that pin (limited by total through the port). The absolute maximum voltage rating on it is 0.3V below GND or 0.3V above Vcc.

Here is my solution so far:

simulate this circuit – Schematic created using CircuitLab

Will this work, and is there anything I might have forgotten to think about? Or a simpler all-in-one IC option I wasn't aware of?


texts: A switch that activates a horn when power is cut

texts:
I am running a wire around the perimeter of my field for approximately 1/4 mile. The wire is not going to be energized but could be. I want to have a horn set up that will blast when the wire is cut. I have an idea how of how to do it but I can't quite figure how to get the horn to blast when the wire to it is cut. There will be power to the horn but it will be switched off until the power is cut. I am sorry if I am not being clear but this is the only way I know how to describe my situation.
To be more clear what I am trying to do is to run an electric wire of very low voltage, maybe 12 volt battery powered, that will trip a switch when cut. When it is cut a switch will trip sounding a horn that requires 12 V dc to blast.


texts:
I'm just beginning with electronics, with the goal of building synth and audio effect modules. I'm currently building and tweaking projects from http://tagboardeffects.blogspot.co.uk.

One mod I'm very keen on is adding the option to use a 0-5v control voltage (CV) instead of manually turning a pot. On commercial modules this is achieved by plugging the CV source into a TRS socket on the unit, which overrides the pot.

I've been able to construct a simple version of this using an LED and photoresistor wrapped in electrical tape (a "vactrol") and hooked up to an expression pedal that provides the control voltage, but I'm running into the following problems with the photoresistors I can find online:

They only seem to be available in a small range of resistances. I'll need to replace quite a wide variety of pots -- typically combinations of 10k, 25k, 50k, 100k, 1M and 2M on a single unit. Some are linear, some log, though that's less critical.
They don't seem to go down to zero; typically I see something like "50k to 100k" instead. I'm not sure how (or whether) I can translate this into a replacement for (say) a 0 to 100k pot. That may be my lack of basic understanding showing through though.

I suppose it must be possible to do this, since many modern units include it, but maybe the vactrol scheme isn't the right one. I'd accept an answer that shows me how to adopt a vactrol solution to a particular circuit (see below) or one that suggests an entirely different approach. I'm specifically looking for a low-cost solution, ideally not costing more than the pot itself.

EDIT: For the sake of concreteness, if that helps, suppose I've built this circuit and want to replace the three pots with CV inputs.


texts: How do you reprogram an XMEGA after you have disabled the `RESET` pin using the `RSTDISBL` fuse?

texts: With chips like the ATMEGA and ATTINY you can use high voltage programming even after the RESET pin has been disabled using the RSTDISBL fuse, but the XMEGA family does not seem to have a high voltage programming mode, so how do you program one of these chips after setting the RSTDISBL fuse?


texts: 5MM Blinking (Candle) LED replacing a White 5mm LED in a Solar Garden Light

texts:
I'm looking to replace the standard white LEDs I have in my solar powered garden lights with the same size yellow blinking (candle) LEDs.  My garden lights use the ANA618.

I know the blinking LEDS use an internal IC within the LED to achieve their random blinking.  Would the wave coming out of the ANA618 interfere with the IC inside the LED and make it useless?


texts: Simplest possible circuit for charging a li-ion cell

texts:
I want to create an ad-hoc single cell li-ion charger. I have a buck step-down that can supply 4.2 volts. If I connect a 1 ohm resistor in series with the lithium cell, the current should go down to 0 when the battery is also at 4.2 volts. A 1 ohm resistor should supply a maximum of 500 mA when the battery is at 3.7 volts.

The battery has protection. Will this be safe? Do I really need that tiny resistor?

Forgot to add: 500 mA is well within the charging capability of the battery 1C (2200 mAh)

Also, I am aware that this will not fully charge the battery, since I am sort of skipping the constant voltage phase.


texts:
Please take a look at this link about biasing input for single ended op-amp topology: http://www.analog.com/library/analogDialogue/archives/35-02/avoiding/index.html

In figure 1, I notice they put a capacitor in SERIES with the non-inverting input.

What exactly is the purpose of this capacitor? Is it input offset elimination? Does it affect overall op-amp performance and make the op-amp unstable by any chance?


texts: how many volts will it take to run a 12 volt motor

texts: I am attempting to repair a lemax Halloween decoration for my wife. The power adapter says 9 v output but there are 2 motors inside the decoration that shows 12 v. Does this mean the adapter is rated too small to operate the motors?


texts: If there are multiple poles at origin, that system is unstable. So a type 2 system will be have s^2 in denominator. So this should be unstable right? Correct me if I am wrong.


texts: is briefly connecting same voltage/different capacity batteries safe

texts:
Ok, so I am working on a project that has two battery packs:

a: 7.4v 2Ah - 8 x 3.7v 500mAh

b: 7.4v 500mAh - 2 x 3.7v 500mAh

These packs will be powering a raspberry pi clone, a handful of servos, and possibly an arduino. I want to try a setup where the pi gracefully switches to the smaller pack when the larger pack is running low, switching the smaller one on while the larger is connected, then disconnecting the larger when the smaller is connected.

My question is: Is this "safe"? Meaning, is there anything I should worry about (spikes/oscillations/etc) by doing this? I've done some searching and can't find enough to make a call I can feel good with, only things regarding permanently having them connected.

I would like to do this so the build has some reserve power to make its way over to its charging station and send me a notification so I can plug it in. Maybe possibly running pi from low cap pack while the big one charges.

Should I refrain from having the two packs connected for a second or so? Any suggestions as to how to do this properly?

Edit: More relevant info about build

both of the packs are wired into a relay (separate channels) controlled by the pi, with a hard switch for the low cap batteries (as a main power switch), and from the relays into a power regulator/monitor, which provides the mains in the build. When the build needs to switch batteries, it disconnects the servo power supply before doing any switching so the only active load is the pi (and power monitor).
Everything is hooked ready to go, but I havent plugged in the batteries because, well I dont know what will happen when the relay switches from low capacity (initial state) to the higher one.


texts: Signal placement in flat ribbon cable, FPC or FFC with digital and power signals

texts:
I want to interface different boards with FPC/FFC or ribbon cable and I was wondering about the placement of the signals in the cable.

I plan to have a 39 signals FPC with :

1 SPI bus (SCK, MOSI, MISO)
4 GPIO for SPI Slave Select
4 other GPIOs
1 JTAG bus (TDO, TDIO, TMS, TCK)
17 GND power wires
7 +5V power wires

I plan to have that many GND wires in order to isolate signals from each other and in order to provide enough return path. The 7 +5V are here in order to provide enough current through the connector.

I placed a GND between almost every signal.

My question is about whether or not there is any issue with placing +5V power signal between SPI lines for example. Will it provide additional EMI or crostalk protection ? Or will it create more parasistic capacitance ?

PS : Similar question has already been discussed in previous topics and the conclusion is almost always the same : place GND between your digital signals. However I have not found any piece of information concerning other power signals such as +5V.


texts: How to switch a leaded solder soldering station over to lead free solder

texts:
I have a soldering station which used leaded solder. I now want to switch over to lead free solder and as such I want to clean the tip.

How can I clean the tip of the soldering iron such that I can use the lead free solder with it?


texts:
I'm trying to work with 32Mhz 4-SMD Crystal. (ASX3F-32M-FA100A4) with two capacitors: 10 pF (attached datasheet)
The IC I choosed is the PIC16f1575. And using MPLABX-IDE MCC
I performed the connection as in the pictures below.

When I select INTOSC in MCC everythings works fine, but if I change the selection INTOSC to ECH in MCC as at the picture below the IC doesnt work.

It only LED blink code in main loop.

void main(void){
    SYSTEM_Initialize();
    INTCONbits.GIE = 1;INTCONbits.PEIE = 1;
    while (1)
    {
        LED_Toggle();
        __delay_ms(500);
    }
}

Is there a wrong connection between pic and crystal?
Is that crystal not suited for this usage?
Something missing on the code?

Rest of the configuration Code:

// CONFIG1
#pragma config FOSC = ECH // Oscillator Selection Bits->ECH, External Clock, High Power Mode (4-32 MHz); device clock supplied to CLKIN pin
#pragma config WDTE = OFF // Watchdog Timer Enable->WDT disabled
#pragma config PWRTE = OFF // Power-up Timer Enable->PWRT disabled
#pragma config MCLRE = ON // MCLR Pin Function Select->MCLR/VPP pin function is MCLR
#pragma config CP = ON // Flash Program Memory Code Protection->Program memory code protection is enabled
#pragma config BOREN = ON // Brown-out Reset Enable->Brown-out Reset enabled
#pragma config CLKOUTEN = ON // Clock Out Enable->CLKOUT function is enabled on the CLKOUT pin
// CONFIG2
#pragma config WRT = OFF // Flash Memory Self-Write Protection->Write protection off
#pragma config PPS1WAY = ON // PPSLOCK bit One-Way Set Enable bit->PPSLOCKED Bit Can Be Cleared & Set Once
#pragma config PLLEN = OFF // PLL Enable->4x PLL disabled
#pragma config STVREN = ON // Stack Overflow/Underflow Reset Enable->Stack Overflow or Underflow will cause a Reset
#pragma config BORV = LO // Brown-out Reset Voltage Selection->Brown-out Reset Voltage (Vbor), low trip point selected.
#pragma config LPBOREN = OFF // Low Power Brown-out Reset enable bit->LPBOR is disabled
#pragma config LVP = OFF // Low-Voltage Programming Enable->High-voltage on MCLR/VPP must be used for programming

And Initialization;

void OSCILLATOR_Initialize(void)
{
    // SCS FOSC; SPLLEN disabled; IRCF 8MHz_HF;
    OSCCON = 0x70;
    // TUN 0;
    OSCTUNE = 0x00;
    // SBOREN disabled; BORFS disabled;
    BORCON = 0x00;
}


texts: How to determine correct mosfet for application?

texts: I would like to turn on a thin film heating element.  I will be controlling the on/off with a 5VDC pin, possibly PWM, using an ATTINY85.  The thin film heater votage is 24 VDC at 2A (max. constant).  I currently have an IRF540N MOSFET to do this but I imagine there's something better suited for the task.  How do I detemine which MOSFET would be best, subject to the contraints.  I am very new to this but I'm here to learn.  I also would like to avoid a heat sink, if possible.


texts: PCB design: power tracks under the ground plane - is the capacitance going to be disturbing?

texts:
I'm designing a PCB that currently looks like this:

I stumbled upon an idea of moving the main power section (especially including 3.3uH coil) and the GSM modem (the one with several drills) to the bottom side of the board and leave all other components on the front side so that those 2 types of functionality are separated. The assumption is also that the ground is going to fill all the empty spaces of the both layes (filled zones).

My only concern is: if at one of the PCB's layer I have a ground plane and at the other one the power line (3.8V @ 2.5 A in peaks) doesn't that make a capacitance that may disturb the operation of the circuits?


texts: Thermocouple effect on low voltage/current signals in PCB and connectors

texts:
As part of my studies, I am designing a measurement setup for measuring leakage current of SMD capacitors in the ranges up to pico Amps.

At the moment I am in research periond and later I will have access to some high end measurement devices such as a picoammeter, a SMU and a low leakage relay switch matrix.

What I have in mind at the moment is soldering 10 SMD capacitors on a cartridge and connect each capacitor to the SMU and picoammeter through the switch matrix

One of the concerns, as I approached here, Is thermocouple effect. If I know that my measurement performance should be in nano and pico Amps range, would this make a huge issue? I am asking this because when I go to PCB design phase, I would have to consider using connectors and PCB routes of same material (Copper).

For example, considering the connection between the test fixture and SMU, picoammeter and relay matrix should be done using coaxial or triaxial (the later can be the best option, but I do not have at the moment any idea of how economic will it be, considering the co to tri converters and theire own price).

So my question, in short, is that should I be worried about this effect having in mind reaching picoamp measurement?

Please let me know if I am not clear enough with the question.


texts:
In the OPTO-Isolator used above, I am not getting flow of ckt.

According to my understanding, in case of PS8821-2, RD ( of MC ) will connect to SCL( of TPS2384 ) and MC_SCL ( of MC ) will connect to SDA_I( of TPS2384 ).

Is it correct? And why we do so?


texts: How can I control more than 64 LEDs using a Uno?

texts:
I finished working on my 4x4x4 LED cube. I want to make a larger 6x6x6 cube. Is this possible ?

Which components should I use to control the LEDs ?


texts:
I'm trying to average 8mV 490Hz PWM signals to analog voltage. I could do it with a passive RC filter, but I want to use an active filter and gain with an okay response time.

So the PWM freq. is 490Hz.

Pulses are 0...8mV.

The PWM average will go to a MCU pin to be read so the range after gain should not exceed 5V.

I have been trying tools and filters in simulations and all failed until now.

What should be the approach to design a simple active filter topology here.


texts:
I am looking for Biasing circuits which can provide gate voltage in the range of -4V to -0.5V.
In the application note of AMPLEON AN-11130, there is a table mentioning the specifications of the circuit.
It is mentioned that "gate voltage adjustment" range is 700mV typical. As per note1, "Resistor values may have to be changed for part of range."
In the "6.4 Gate voltage adjustment" by adjusting resistor values of R13 and R14 the gate voltage can be trimmed.
Is it possible to get my gate voltage requirements by using this circuit?

Edit:-
Added schematic snapshot

Is it possible to meet my requirements by changing the resistor values of R13 and R14?
Edit 2:-
"R21 determines the supply voltage at which operating VGS is applied"
What is the meaning of this? I know that these resitors are being used for setting threshold voltage for the "FB" pin. When there is transition from low to high on FB pin thresold voltages, PGOOD generates high signal. How this will control VGS generation?


texts: I've bought packages of this connector from Digikey. However, according to the manufacturer, the crimp tool for the USB cable onto these connectors are no longer sold. For the DIY hobbyists out there, I would like to read about your suggestions on crimping the kit onto the USB cable after soldering is complete. Thanks!


texts: For MRI imaging, during quadrature detection, if sine carrier has phase shift about some angle, what would change on the image? I could imagine real and imaginary parts of signal separetely but i can't exactly decide the image combining both. How quadrature and in phase images combine together to form the resulting image?


texts: Effect of three PID gains on each other?

texts: Do the three PID gains - Kp, Ki and Kd relate to each other or are they independent?


texts: Transient analysis error(missing value) with OrCAD PSPICE 9.1

texts:
I am new to PSPICE, and just tried an example given in the book I'm using (SPICE by Sedra/Roberts).

Transient Response of a Linear Network
* input signal source
Vi 1 0 SIN ( OV 10V 60Hz )
* linear network
R1 1 2 1
C1 2 0 2.65m
Rload 3 0 10
E1 3 0 2 0 10
*analysis*
.TRAN 1ms 50ms 0ms 1ms
.PRINT TRAN V(3) V(1)
.PLOT TRAN V(3) V(1) (-100,+100)
.end

When I run the simulation, I get an error :

* input signal source
Vi 1 0 SIN ( OV 10V 60Hz )
-------------$
ERROR -- Missing value
* linear network
R1 1 2 1
C1 2 0 2.65m
Rload 3 0 10

I tried changing the input signal line to vi 1 0 sin ( 0V 10V 60Hz 0 0) but the error persisted. What am I doing wrong here?


texts: Can a too powerful battery damage a circuit?

texts: I have an IOIO board, a 13V 10A Battery (when I tested with my multimeter). For the IOIO board, 5-15V, ~10mA is enough. Can a 13V 10A Battery do wrong to the board or is it okay?


texts: What happens to current in a Parallel Circuit

texts:
I am wondering what are the affects to current in a parallel circuit and if the current can be run in parallel in the same way as with voltage (eg. To power 3 phones in Parallel would I need 3 times the current)
Edit: I am using the phones simply as a example
I am trying to power 10 laptops at 19.5 volts (running them in parallel) . And each laptop needs 8 amps to run  So my question is to power the 10 laptops  in parallel do I need 8 amps (the power necessary for one laptop) or 80 amps (The power necessary for 10 laptops).


texts: Generating high frequency sine wave (up to 100MHz)

texts:
I am in the trying to design a sine wave generator. This generator should be able to sweep through a range of frequencies and the range would be 150 KHz to 80 MHz. the sweep rate is not more than 1.5*10^-3 decades/s.
There are different oscillator topoplogies, but I can't use, say a purely RC oscillator or a crystal oscillator as they offer a static method of generation (single frequency).
As I want a more dynamic design, I think I would need a varactor diode or a FET transistor in its resistive region, but as this is a new area for me, I don't know if the ranges of the mentioned devices would be sufficient. Or alternatively a simple potentiometer which one can manually rotate and change the output frequency, as the design is not focused on either automatic or manual change of frequencies.
I was hoping a more experienced individual could direct me towards the right topology to look at.
Any help is highly appreciated.


texts: How to transfer energy generated from electromagnetic induction to a USB port?

texts:
For a school project, I'm creating a shake-powered phone power bank that will generate current similarly to a Faraday flashlight, which will in turn power a usb port.  A simple enough concept.

Now to my (limited) knowledge of electronics, as I understand it, this process of electromagnetic induction will induce an AC current, which I believe can be converted to DC via use of a rectifier.  My problem lies in that I'm not sure how to store this charge.

My original idea was to purchase and disassemble a power bank and rewire its input to my "shaker" circuit's DC current.  However, I've been advised that without knowing what voltage my shaker will produce, this may not work as well as I'd hoped, and could end up frying the whole circuit.

I know of supercapacitors, but there appears to be a wide range, with varying volts and Farads, of which I don't know what to choose.  I would have assumed that more Farads would be better, considering that it is a unit electrical capacitance, which would give the power bank more capacity, however in this video that partially inspired the project idea, the narrator opts to use a 1.5F supercap instead of a 22F one, which has added to my confusion.

(sidenote: if I use a supercap, I'd need to wire the USB port myself, which I'm hoping I can simply take off of the circuit of the store bought power bank, but let me know if that is a bad idea that will just cause more problems)

Hopefully you people a lot smarter than I am can clear up how to go about wiring this thing up.  Thank you in advance.


texts: Does the Sparkfun SAMD21 Mini/Dev Breakout work with the ATMEL Studio

texts:
I'm new to the SAM product line from ATMEL. I purchased the original ATMEL Xplained board, which works nicely with the ATMEL studio for programming & debugging. I know that the Xplained board carries it's own chip for programming (I guess this is like a small ICP device).

I now want to bring the SAM D21 to my own PCB. As a starting point, I came across the dev breakout board from Sparkfun (see https://www.sparkfun.com/products/13672).

I don't see an additional chip on the sparkfun board, and I'm wondering if I can use the ATMEL Studio for programming/debugging with the ATMEL-ICE device?

Many Thanks
Christian


texts:
This is the first question in stack exchange.Ok, Im trying to initiate UART of pic microcontroller(PIC24F family). I studied uart related registers in the datasheet and wrote the code to transmit a character 'K', after compile the code, hyperterminal doesn't show anything.

Here is my header file code:

void init_uart1()
{
 //initiate uart1
 RPOR4bits.RP8R = 3;   //pin8
 U1MODEbits.STSEL=0;
 U1MODEbits.PDSEL=0;
 U1BRG = 25;
 U1MODEbits.UARTEN=1;
 U1STAbits.UTXEN =1;

}

Here is my main file:

    TRISB=0x0000;  //0000 0000 0000 0000
    PORTBbits.RB8=0; //set outout PORTB 8th pin

   init_uart1();
   while (1)
    {
       while(U1STAbits.UTXBF == 1);
       U1TXREG='K';
    }

whats wrong in my code?

Thxns...


texts: sign extend for addition and subtraction problems

texts:
I have this project for Computer Architecture, I already got to the point where I draw a 1-bit ALU for add and subs 2'C numbers.
Suppose if I want to add an overflow output, how do I add to this 1-bit ALU?


texts: Interfacing retriggerable oneshot with optocoupler

texts:
I'm trying to interface 74HC123 monostable with 6N137 optocoupler. Signal from optocoupler will turn on MOSFET driver. Monostable outputs correct signal when optocoupler is not connected - 200 ns pulse. When I connect optocoupler with monostable the voltage on monostable pin 4 is pulled down. I thought that it was due to low output current of monostable, but this is ok according to datasheet. Maximal monostable output current is 25 mA, LED in optocoupler will take around 10 mA.

Monostable is activated by pushbutton. I need positive pulse on optocoupler output. IC's are setted according to highlighted fields in truth tables below. Monostable output pulse width is setted byt C3 and R2.

Osciloscope images of button click, and output monostable pulse with  not connected optocoupler are below.

Monostable datasheet:
http://www.ti.com/lit/ds/symlink/cd74hc123.pdf

Optocouplet datasheet:
http://www.mouser.com/ds/2/239/S_110_6N137%2020140411-596065.pdf

Circuit diagram:

C1 and C4 are decoupling capacitors.

C1, C4 = 100 nF, C2 = 82 nF, C3 = 100 pF

R1 = 8k2, R2 = 2k, R3 = 330, R4 =2k2

74HC123 monostable truth table:

6N137 optocoupler truth table:

Pushbutton click:

Monostable outputpulse:

Any idea what may be wrong? Is this correct way for interfacing this two parts ( high output idle state of monostable )?


texts: clearing out voltage of a synchronous circuit

texts:
I apologize if this has already been answered, but i can't seem to find this question anywhere, maybe because i'm not using the right terminology in searching.

My understanding is that most processor chips use MOSFET transistors. I imagine that the circuit (chip) is in some sort of neutral state before use, and then a control signal sets off a chain reaction whereby one mosfet activation allows voltage to rise/drop in a circuit, causing activation/deactivation of another mosfet and so on.

At some point, we say (i think) that the circuit is settled, and the output voltages are correct representations of the computation. So we store them in a memory cell and it's time to run the whole process over again.

But now my circuit has a different voltages in the circuit than it's initial configuration!  I would imagine the solution would be draining the voltage, but every solution i think of seems to have some issue or other.

How exactly do we drain the voltage of a reusable circuit to ensure it has the same start conditions every time?


texts:
I currently have the following circuit shown below on a prototype PCB.

The circuits intended purpose is to do the following:

Receive two 5V PWM signals from a microcontroller.
Boost the current a little using the FDS6912A N-channel MOSFET
The signal then passes through a 4N25 optocoupler. Each optocoupler has its own independent battery, which isolated the microcontroller power from right hand side.
The output of the 4N25 optocoupler is passed through to an ESC (Electronic Speed controller). To me the speed controller is a "black box", but it is used to drive a motor.

The problem I'm facing is that the FDS6912A N-channel MOSFET fails (for a reason I can't understand). The PWM signal at the input of the PWM_CH1 and PWM_CH2 is fine when I scope it. The output of both optocouplers remain at 0 V.

What I've found is that after replacing the FDS6912A mosfet the PWM tends to work fine again. My observations lead me to believe that the mosfet is blowing when I initially connect the batteries but I can't work out why. This is my theory but I can't be sure.

Because the circuit is already on a PCB I am severely restricted in what I can do to try and fix it. If I can put in a better replacement MOSFET that suits an SOIC-8 package or a suggestion can be made as to the cause it will greatly assist.

I've attached datasheets of the mosfet and Optocoupler in the links below and any help would be appreciated.

Update:
I Re-Examined the Gate voltage after another mosfet Failed and yes.. The PWM duty dropped from 5V to approximately half a volt (0.5v) after it failed. If I disconnect the mosfet it returns to 5V. Can anyone suggest a more resilient mosfet... Or will i have to resort to somehow modding the PCB to try and include a series gate resistor?

FDS6912A datasheet

4n25 Optocoupler datsheet


texts: What does this symbols means on the LCD pin outs?

texts:
I am trying to understand this product : NHD-C0220BIZ-FS(RGB)-FBW-3VM

It is a LCD with back light in reg, green, blue (not clear for me if they are mixed or you can only choose one)

What do you think that A , RK, GK, BA means? how I should connect it to the MCU and voltage?


texts:
So I'm new to the battery banks. One bank is (6) cells made of (2) 6v, 12 amp hour sealed lead batteries each. Wired parallel to make a 12v, 144 amp hour bank. Is that correct?
Next I have a smaller bank, that is (2) 12v, 18 amp hour sealed lead batteries, paralled Making a 12v 36 amp hour, is that correct?
If I'm on the right track I'm glad. So my last question is. If break my 2 battery bank down, so they are 18 amp hours. Will it hurt to tie them into the other bank where each cell is 24 amp hours? I know with big differences it is hard on the smaller amp hour batteries, but was hoping it wouldn't be the case here and I could get 180 amp hours if I'm correct. Thanks for any advice. Hope I'm on the right track....


texts: I2C - Certain Slaves not Pulling the Lines down fully

texts:
I have a large number of boards deployed with a TI CC3200 microcontroller and a variety of sensors for an industrial monitoring application. I have been having an issue for some time now, on some of the boards, where an infrared temperature sensor, TI's TMP007, cannot be read from. This includes any manufacturer/device ID registers. They communicate via I2C, and there are 10k pullups on both lines.

I have been looking at the lines on a scope, and found that when communicating with the TMP007 the voltages are only pulled down about half as much as when communicating with some of the other, working, I2C sensors. It still seems like it meets the I2C spec at least though, and the TMP007 appears to ACK when I write its manufacturer ID register to it.

My question specifically is, has anyone had similar issues before where different devices are pulled down to different levels and what possible causes this could have. For instance, could it be a problem with the hardware or could another I2C device be trying to drive the lines at the same time?

Edit: I believe Ali Chen has rightly pointed out a power supply starvation issue, switching off some of the other I2C sensors when reading from the TMP007 appears to have solved the issue.


texts: how can the current flow if the potential difference is 0 volts?

texts: I have read so many articles on so many websites about transistors and everywhere it says that when transistor is acting as a closed switch and conducting the voltage across collector-emitter is 0 volts, so how can the current flow if the applied voltage across two points is 0 volts?


texts: What is this circular rod with wired wrapped 'coil' and ceramic capacitor?

texts:
Found this in a battery compartment, glued with white gum, however not connected to anything.

It is a ferrite circular rod of 3cm, diameter 6mm and wrapped with some wire (12/13 windings) and connected to a ceramic capacitor of unknown size (very small capacity I think).

I have really no clue what it supposed to be, any ideas?


texts: Vo in this simple circuit with forward biased diode

texts:
So what's   $$ V_{o}?$$ if V_s is 4V

$$R_1 = 3k$$

$$R_o = 1k$$

It seems like such a simple question, do I assume diode is short and then combine the resistors in series?

Do I find current across R1 and then multiply it by Ro?

Or is it just KVL??

Like 0 = V0 - Vs + (voltage across R_1) + 0.7V (diode) ????

Or do I just intuitively say, oh I start with 4V then I go clockwise, experience first drop of 4V-0.7V across R1, then again 0.7V across diode, to finally 2.6V across R_o ???

Also, I know that diode is on if cathode is not at a higher potential, since the cathode side is 0V, diode will conduct (be on).


texts:
I have a basic doubt about electromagnetic waves emitted by a certain source.

Depending on the shape and on the physical properties of the antenna, its electromagnetic waves may have different wavefronts. But it is known that in the so called far field region, the emitted wave is like a spherical wave (since its electric and magnetic will be like \$\frac{e^{-jkr}}{r}\$) which may be locally approximated with a plane wave.

Now my question is: how can this behaviour be true for any antenna? Let's consider for instance the following examples:

1) Dipole antenna:

It is not an isotropic (spherical radiator), as we may easily see from its radiation pattern: if I take a sphere in the space and I move along its lateral surface, I see different powers.

2) Parabolic antenna: it is an high directivity antenna, so it is a lot different from an antenna which generates a spherical wavefront

3) All kinds of antenna with pencil beam pattern

How can we say that the far field wave is spherical for those types of antennas? It seems an absurd to me.


texts: Struggling with serial communication over RS 485 using modbus protocol

texts:
I have around 60-70 inverters that I want to talk to using arduino over RS-485. The connection that I am making with arduino is according to the attached image.

Now I think that my connection part is okay! Where I am falling behind is the coding part I guess. As for every request I am not able to make even one successful request.

The modbus library that I am using is SimpleModbus Library here's the link to it:  https://drive.google.com/folderview?id=0B0B286tJkafVSENVcU1RQVBfSzg&usp=drive_web

The data format that the inverter manufacturer is using is as follows: start byte, slave address, function code, data, check, end byte.

Whereas the request I am sending through my master device looks something like this:

packet1->id = 25;
  packet1->function = READ_HOLDING_REGISTERS;
  packet1->address = 3000;
  packet1->no_of_registers = 3;
  packet1->register_array = regs;

I am not including any start byte or end byte. Is it the reason why I am not able to receive any response from the slave device? or is it because I have to program the response of the slave devices as well?

As of now I am only playing around with the master device code and have not figured out on how to receive the response of the slave and how to decode it. Every modubs library seems to have two kinds of program one for the master and other for the slave. Whereas I use only the master code for sending requests to the slaves.

Do I have to program for slaves as well? if yes then how to program for both the master and slaves together on my master device arduino which is talking to my inverters?

I am new to arduino but experienced in programming. Just lack some basics in electronics and modubs protorcol over RS-485. Kindly please help me

Thanks in advance.

P.S: I have wired all my inverters through RS_485 ports correctly, I am connecting the negative end to the pin 7 on RS-485 chip and the positive wire to the pin 6 on the chip


texts: Large signal vs small signal analysis of Differential amplifiers

texts:
Here is a question from the textbook "Design of Analog CMOS Integrated Circuits" (Razavi)-
Assuming the circuit shown is symmetric, sketch Vout as (a) Vin1 and Vin2 vary differentially from zero to VDD, and (b) Vin1 and Vin2 are equal and they vary from zero to VDD

I did solve it but I don't think my technique is correct. I am finding it a little difficult (and non-intuitive) to write equations and solve for large signal variables in complicated circuits like in this problem, and none of the solutions I have seen so far have explained how they got the final Vout vs Vin plots. Please help! Thank you.


texts: What does a capacitor parallel to a resistor do in the feedback of op-amp circuits?

texts:
What is 10Mohm for?
What would happen without it?


texts:
Implement the following circuit:

Note that this is a latch, so a Quartus warning about having inferred a latch is expected.

This is my implementation

module top_module (
input d,
input ena,
output q);
always @(*)
    begin
        if(ena==1'b1)
            q=d;
        else
            q=q;
    end endmodule

Can someone help me why there is a inferred latch even though i am solving q for every case possible?


texts:
With the TM4C123G board, I'm using Code Composer Studio v6. I want to read the GPIO pins that are connected to the user switches on the board (Pin F4 and Pin F0). The code at first did not work but after a search on the Internet it worked after I added this function:

GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_0 | GPIO_PIN_4 , GPIO_STRENGTH_2MA , GPIO_PIN_TYPE_STD_WPU);

I opened the TivaWare documentation, I kinda got an idea on what this function does. But my questions are:
Why to specify the drive strength for the input pin ?
And why should I choose between pull up or pull down resistors ?


texts: CPLD High-Z pin - safe to drive over the high logic level voltage?

texts:
I have a CPLD connected to a BUS and an EEPROM. The bus has 3v logic and is 5v tolerant. The CPLD is 3v only.

If I configure the CPLD pin to be in the high-z state and the eeprom drives that pin to 5v would that damage the CPLD even though its now "floating"? The eeprom/cpld are connected in parallel to the bus.

Sorry if this seems like an obvious thing - I'm quite new to all this :).


texts: How to test high voltage Zener Diodes with multimeter?

texts:
Given an unknown Zener Diode taken from a circuit board, is it possible to measure the Zener Voltage without a datasheet?

I tried to make a circuit like the one below and I add batteries in series till reached 96V. No Zener Voltage met yet. (how to https://youtu.be/WdDFI1IRQds]1)

simulate this circuit – Schematic created using CircuitLab


texts: I stripped a USB cable to use in a power supply and instead of the usual 4 leads inside the cable, I found only 2--red and black. I'm assuming that's 5v and ground, but I was kind of confused by what I saw. Is there another USB spec that uses only 2 leads?


texts: 3V and 5V supply Topology (Embedded Design, Mixed Signal)

texts:
I am developing a mixed-signal embedded system that requires both 5V and 3V rails.

The 5V rail powers an analogue sensor and a precision ADC.  The nature of the sensor is such that its output will be DC most of the time and slow-changing the rest of the time.  Low noise and low temperature coefficient are the most important aspects of this rail.

The 3V rail supplies the digital circuitry (ADC digital interface, MCU (SPI & UART comms), modem).  There are two SPI slaves - the ADC and a DAC.  The noise, tempco and regulation of this rail are not critical.  Low cost is most important.

The ADC is continuously sampling, the SPI transactions are periodic and the UART communication is on-demand (and infrequent).  The microcontroller's internal oscillator runs at 1MHz and is sync'd to a 32768Hz watch crystal.

There needs to be a wide input voltage range (10 - 40V DC).  For this reason I intend to use three series LDOs; the first will connect to the input and will output 5.5V.  The reason for 5.5V is that the 5V supply has a dropout voltage of 200mV, which needs to be maintained over a large temperature range.

This 5.5V rail will feed the two other LDOs.  Two ways of achieving this are shown in the image below (the 40 ohm resistor is integral to an IC - all circuit current flows through it):

With reference to the image, please evaluate the truth of the following statements:

1)  Topology B is much superior, even if the supplies are bypassed well, as changes in demand will still have some effect on the 5V rail load regulation.

2)  There is not much difference between topologies A and B, if the supplies are well bypassed and the 5V rail has good load regulation.

3)  Statements 1) and 2) can't be meaningfully evaluated without more information about the system and components.

4)  The greatest effect by far will be due to the grounding scheme (e.g. daisy-chained ground connections back to the 40 ohm resistor as opposed to a star configuration).

5)  Both topologies are a strange/inefficient way of achieving the objective.  There are solutions that are much better in terms of cost and performance.

6)  This question shows a lack of understanding.

EDIT: 7)  LDOs are generally better at dealing with line variation than load variation.  So while topology B might have more of an effect on the 5.5V rail, the 5V LDO will handle this better than if there was an effect on its load (as there is in topology A).

EDIT: To clarify, the circuit is low power - only 3.1mA in total is drawn from the input.


texts:
What are the mathematics behind twisted pair cabling? I know that the twists are there to help eliminate cross talk and interference, but I want to know about the math of how they find the specific twist rates.

Is it just experimentation ("Oh looks, it works better now"), or is there actual math behind it that says based on the size of the cable you should twist it this many times per inch/foot to get the desired effect?


texts: How do induction cookers measure temperature?

texts:
This is not exactly about electrical circuitry, but I hope it's close enough not to get me kicked out. Please redirect me if necessary.

Almost all induction tops advertise possibility to "keep temperature", usually in 10°C steps, so I guess that is the precision they can measure temperature with.

I would like to understand HOW temperature is measured and what are actual limits of technology, including precision.


texts: Controlling Valve Actuators with PWM signal

texts:
I want to control ME-4340 Syncube Non Spring Return Modulating Valve Actuator - 0/2-10Vdc ME-4340 with an STM32.
The Timer configurated as PWM generator of the STM32L073RZTx gives 3.3V at 100% So I used a voltage follower with gain of 4 + RC filter with cut off frequency of 160 Hz.

The op amp I am using is NCS20074DR2G Datasheet. it has Maximum Output Current of +-100mA and it is capable of sourcing 60mA when it is supplied with 10 VDC.
My questions :

Is this valve even controllable by PWM signal?
What is the max frequency of the PWM signal I can use ?
What is most crucial factor for the valve ripple voltage or response time of the filter? ( for lower cut off frequency I get less ripple in other hand the response time increases to about  100 ms)


texts: Suitable processor for a Robocup Junior Soccer robot?

texts:
Last year, I entered into the Robocup Junior Soccer competition using a robot built from the Lego Mindstorms NXT kit. It worked well, but we were thrashed at the international level, mainly because of the sheer speed and strength of the opposition.

This year, I'm intending to build the robot from scratch, as interfacing non-lego motors and sensors with the NXT is troublesome at best. However, I have absolutely no experience with any other microprocessor, and am wondering what to get.

The microprocessor needs I2C and PWM outputs (to drive 3-5 motors), and preferably should be cheapish, and programmable in some object-oriented programming language.

Would an arduino be suited to this purpose, or this that insuffient/overkill?


texts:
Need help identifying this SMD component which is shorted.  I suspect it is a Zener diode. I have searched the markings ad nauseam but could not find an answer.
The length is 5mm, so I believe it is a SMA package
Markings are:
LT7B27
HE
Any hints are greatly appreciated, thanks!


texts:
This is a Fourier waveform question that I am struggling with.

$$x(t) = \frac{8}{\pi}\left(\sin(8000\pi t)+ \frac{1}{3}\sin(24000\pi t) + \frac{1}{5}\sin(40000\pi t) + \frac{1}{7}\sin(56000\pi t) + \text{...} + \text{...}\right)$$

Updated with shown attempt.

F1 =2π/W1 =1/4000

F2 = 2π/W2 = 1/12000

F3 = 2π/W3 = 1/20000

F4 - 2π/W4 = 1/28000

F1/FN RATIOS

F1/F2 = 3

F1/F3 = 5

F1/F4 = 7

LCD OF RATIOS = 35

35 X F1 = .00875
F0 = .00875

Fundamental frequency = 2π/F0
=360Hz


texts: Voltage regulator misbehaves under certain conditions

texts:
Okay guys, this one has me baffled. Take these two circuits:

Typical stuff; Power in goes to the + rail, GND to the - rail. This is a 19V power supply going in. It goes through the voltage regulator (rated for up to 35V, 1 A), output pin goes through the load and back to ground.

Now, In the circuit on the left, taking a multimeter and measuring voltage between the positive rail and negative rail (total voltage) gives 19V. Measuring from A to B (output pin of the voltage regulator to the negative terminal) gives 5V.

Now replace that resistor with a different load: The Raspberry Pi. It's wired correctly (i.e. converted to USB correctly, it's supposed to run on 5V).

In the circuit on the right, measuring voltage between the positive rail and negative rail gives 19V. Measuring from the A to B, output pin to end, gives 2.5V.

It just does. The Raspberry Pi doesn't even turn on. Take it back out and put a resistor back in, you measure 5V at the output pin.

Is this a dysfunctional regulator? Or am I not understanding something?


texts: Convert select / trigger coils to direct fire

texts:
Working on ignition system controlled by prehistoric ECU, it has 2 signals: select and trigger. Select switches CoilA and CoilB. Trigger controls dwell time.

I want to purge old broken coils and install modern ones with integrated ignitors. So need to convert select/trigger signals (0..5V) to 2 direct outputs for each smart coil (0..5V). The power applied via different inputs so these signals can be considered as logic only.

That can be easy done with a few general purpose logic elements, but I feel this is very common case in electronics and there should be simple existing solution (simple -> single chip).

Any ideas?


texts: Does my electric clearing field actually make ions?

texts:
I am using an electric clearing field of 15v/10cm (~150V/m) to remove ions from a test chamber, however I'm wondering to what extent the localisation of the field's reference voltage plays a role.

simulate this circuit – Schematic created using CircuitLab

If, regardless of what reference value the "ground" is at, the clearing field is at 15V, does the field always remove both positive ions and negative ions?

Or does a field of -7.5 to 7.5V behave differently to a field of 100 to 115V, say removing mostly negative ions?


texts: How does the current and voltage affect the torque and speed of a brushed motor?

texts: My 28-turn motor is attached to a ducted fan. When I put 8.4 volts and 3000 mAh into it, it starts emitting an unpleasant odor. I was wondering if I should lower the voltage and/or current and what would happen?


texts:
I'm trying to connect multiple components (same components) to an FPGA output. The FPGA runs at 30Mhz and transmitting both a clock and data on lines connected to these similar components.

Each component is located in a different distance from the FPGA where the shortest is 10mm and the longest is 300mm

When the difference is 290mm and the frequency is 30Mhz, do I need to worry about one signal reaching before the other?
Is there a rule of thumb or a way to calculate what is the maximum difference in distances that is allowed for a specific signal frequency?
Should the trace be thicker or thinner for fast data? will 8mil do?

PCB is flex 2-layer, no right-angle folds, 1OZ copper, signal can be 3.3V or 5.0V

Gilad.


texts:
Pretty new to LED wiring, so need a little advice, please.

Project includes 16 LEDs in all, 4, different colors with, of course, 4 slightly different requirements: 4 Red, 4 Blue, 4 Green and 4 Yellow, each combined on a separate "leg" of the project and a 12v power supply.

Wiring them ALL in series is problematic for this project......so, my question is asking what is the best wiring method?  I've seen posts about wiring legs in series but connecting the legs together in parallel to the power source, but this is still so new to me, I get quickly lost in the calculations.

Related question, when using an online resistor calculator, should the legs of 4 use a resistor that applies just to that single-color-4-LED-leg?

Thanks for your time in advance.

EDIT:  Sorry, but those schematic elements are still new to me as well....here;s the best I can offer at the moment.  Each of these "legs" are  not adjacent, so I would prefer handling them as bundled, either in series or parallel.  Thanks]1


texts: Is USB host always protected from reverse current?

texts: Does the USB specifications require that USB ports of a USB Host device are always protected from reverse current? If one connects a USB host to a different USB host for some reason, is it natural that one breaks? For example, one can connect two PCs using a USB cable. If this is really a serious problem, then I think USB would not be as popular as how it is now.


texts: Optimal configuration for PLL on LPC17xx

texts:
I'm trying to write an algorithm that would pick the best available PLL0 configuration for the user based on F_in and F_cclk.

The manual says that I should pick higher F_ref if possible for a more stable PLL, for low frequency input clock. It doesn't specify what frequency is considered low, though.

Given the NXP's spreadsheet for PLL options calculation there are two variables: F_cco and m/n pair to use.

What is the optimal value to use (performance-wise? stability-wise? what does it change, actually?): bigger m/n vs. smaller m/n vs. bigger F_cco/pll divisor vs. smaller F_cco/pll divisor?

I don't care about USB special case for now.

TL;DR: what is a better option and why:

Given F_in = 12MHz and expected F_cclk = 100MHz

m=50, n=3, divisor=4 or m=325, n=26, divisor=3?


texts:
I just want to know if a 24v 2.2A output power adaptor can be use on a 24v 0.75mA unit? I have not tried it because I'm afraid that it might harm the unit due to a huge difference in Ampere..

I would really appreciate if someone can answer me this..

Thank you so much..


texts: What is the best way to store date & time in eeprom using less bit possible?

texts:
I want to save data associated to a timestamp (like a datalogger) along a month, in a very small memory (probably only 1024bytes). I was thinking using epoch time to save timestamp but it already take 4bytes. So I'm looking a way to save size of date or time data, idea?

EDIT: To be more accurate, the periodicity of the records will be change according the range of period (max a month): should be every 15min or each hour for example. Anyway, in this case it's a non-sense to have 'second' resolution.
I though also to record a start date/time value and just a time offset for each record !


texts: Sources about the working of Intel's new 3D transistors

texts:
I've been searching the net for an explanation about the working mechanism of Intel's new 3D transistor, the most "thorough" explanation I found was this 4:20 minutes long Intel video that doesn't really explain anything.

I'm looking to know about its regions of operation, how the solid state of the device changes in different regions of operation and what improvements does the 3D transistor offers over the 2D.

(Explanations that contain formulas, and professional lingo are preferred)


texts:
I wan to dimmer an halogen lamp 12V DC 20W with PWM from Arduino Nano (3.3V). I was using an IRF520 Mosfet then a guy advice me to use an IRLZ44N, but didn't explain me why. I've tried to read the datasheet but my poor electronic knowledge didn't help me a lot.

What is the difference between the two components? Why I should use one instead the other?


texts: Simulation doubt with Zener diode & MOSFET

texts:
I have the below circuit in which I am trying to perform simulations.
Simulation Tool used - Falstad Simulator
12V Zener Diode
Top MOSFET
Bottom MOSFET
Question 1 :

The Zener diode is 12V Rated.
I want to simulate a current of 12A through both the MOSFETs
So, for my 16V input voltage, I calculated my Resistance to be 1.33Ohms to get a current of 12A.
But when both the MOSFETs are ON, my drain current through them is only 91mA. Can someone tell me what is the problem and why am I not getting a drain current of 12A? And I tried to change the Rds(on) MOSFET parameter in the tool, but not able to find and change it.
Next Question :

When I apply a negative voltage of -14V to the gate of the bottom MOSFET as shown below, I get a voltage at the Zener cathode as 2.195 and a voltage between the MOSFET nodes as 2.7V with 6.4mA of current?
Can someone tell me how this 2.195V and 2.7V is appearing? Just want to understand the circuit behaviour in these conditions. Please help.


texts: If a 110 volt motor asks for 4W does that mean I will have to change the wall power?

texts: I am new to electronics like motors so help on how to set this up would be awesome.


texts: Change LCD information from PIC using push buttons

texts:
I can connect my PIC18F4620 to an LCD and I can display my sensor information with no problems.
Now I came into an issue, I have 3 sensors - 2 digital and 1 analog - I can perform the readings, but I can't show their results in the LCD - since it is a 16x2 - I was wondering If I can use push buttons to swipe the sensor's information in the LCD, I could do that but since my sensors have a delay_ms(5000) whatever I do in this 5 seconds range does not happen anything - it makes sense since it is a delay - I thought about interrupts, but I came with the very same doubt, how can I swipe the LCD screen to show another sensor information even if I have this delay?
Are there any other solutions I could use here?
I forgot to mention, I am using PIC CCS as the compiler.


texts:
In a standard diode voltage doubler (multiplier):

Does the capacitor also plays the role of smoothing out the output voltage?


texts:
I'm using an ADC (adc081c021) with a pretty noisy input:

There is also a 5-second video here:
http://tinypic.com/player.php?v=2ue47cm&s=5

The objective is to detect the two peaks. How could I smooth this input in order to have better ADC readings? Is there a better option than a LC filter? Any recommended values?


texts: adding relays to power headlights in a ford transit custom van

texts:
first off i am a beginner/diy chap soley trying to improve my personal vehicle and i am  in no way in my comfort zone here with electronics i am extremely basic a friend gave me advice on the relay set up over the phone and all i did was carry out from the guidance. Allow me to provide what i have done thus far may be far from adequate for you guys to help me but i am hoping we can muddle threw, Allow me to start with the basic plan
I have a 2014 ford transit custom with standard H7 headlight bulbs
I have replaced the front panels on my van with the new shape panels to give the van a modern look,  2018 2019 design in turn i have replaced the both front headlights.
My original headlights have DRL lamps standard bulbs,  my new headlights have led drls.
I fitted the new shape headlights,  and the led drls worked,  my main beam did not nor do the drls dim when the main bean is turned on (they should dim 50%) nor do them dim when we indicate again should dim 50%.
So i tackled the lack of low and high beam first and this is how i go them to work
i used a 4 pin 12v 20amp relay,  i took ground from the body to pin 2, then 12v with a inline 10amp fuse to pin 3 relay,  the headlight plug i cut pin 8 and took that wire to pin 3 on my relay and returned the harness side on pin 5.
I did this on both headlights so they both have a relay each,  and my main bean and dipped work.
I have two sets of headlights for the facelift model,  one is fitted with standard h7 bulbs the other set are factory hid bi xenon lights, both sets now work.
the only issue i had was i would get a error msg on my dash complaining the dipped headlights are not working,  i have two fault codes for low beam circuit both left and right = the 2 fault codes. B1D00 and B1D01
i used croc clips temporary for testing connected a h7 bulb to pin 1 and 2 on the relay,  both sides and the error codes were gone,  so i have tried numerous resistors 50w 4.7ohms 5-6 ohms and nothing worked again i put them across pin 1 and 2 relay,  the h7 bulbs when connected across pin 1 and 2 were given me 120ohms the draw 2.78amps per bulb
question 1 is are my calcs way off with using 4,7ohms in a resistor (i am going off what's available online with titles for h7 canbus errors)
question 2 is i cant figure out to be honest why the van is fitted with h7 from factory but will not work with the new headlights again with h7,  if anything i expected them to work (h7) and the bi xenon to require relays only thing i can think is the leds draw more power and that was taking the power away from the main beam?
the next issue i had was i had no sidelights,  i had at this point
high beam
low beam
corner lights
drls
indicators
but no sidelight,  so i bridged harness side pins 2 and 3 together (the drls are used as the sidelights normally on the new shape model anyway)  and that gave me sidelights.
i plan to resolve the dim with a drl auto dim kit i have bought on amazon,  that i intend to look at at some point once i figure out the original question 1
i am sure my design has many floors and i wanted to run it by you guys here and see what you made of my attempts.
there is an additional issue that has raised its head today which i wont go into detail just yet as i would like to discuss my first stages at this point in time.
i have uploaded the original ford wiring harness (plug to headlamp) for my van and the facelift new shape wiring harness diagrams they are quite similar left is my original wiring the right is a new shape wiring .


texts: How to use external power supply for Arduino Uno?

texts:
Can I use an AC power adapter that can be connected through USB port? My board is Arduino Uno and usually connect to my computer through the USB cable.

AC power adapter <-> USB port <-(USB cable)-> Arduino USB port

What kinds of components can be used as external power supply for Arduino board? It's really nice if you have some images or names about them.


texts: How do integrator circuits serve as memory devices in continuous time system?

texts:
I didn't understand the yellow-marked sentence clearly, and even I did, what does it have to do with the conclusion that follows it? (marked in green).
Thanks in advance..

Source: Modern control engineering 5th ed, chapter 2, state-space, page 30


texts:
Frankly, I'm overwhelmed with this circuit that I have to start building in lab tomorrow.  Last week we built an octal decoder that takes a 3-bit binary input from 000 to 111 and displays a unique character of our choosing on an LED display (common anode). It was all combinational logic and I understand it fairly well. Now we're expanding on the circuit and I don't understand a lot of the circuitry or how it works. I will briefly describe the assignment and then try to explain what I do and don't understand. Here is the schematic:

Note that n=3 here.

The assignment:

We have to design and build a circuit that will display 9 bits of data on 3 separate 7 segment (common anode) displays. A DIP switch controls the three inputs of the decoder built last week. The three separate digit devices have corresponding segments wired together (e.g. a to a, b to b, etc.). The output only appears on one of the displays at a time, but if they are scanned fast enough they should all appear lit.  For the multiplexing I have to use 7403 open collector logic. For each digit, we must design a transistor to function as a "high end digit driver" in order to source/sink appropriate current to light the digit adequately. We must design a counter circuit that produces the digit drive signals sequentially from right to left.

My Understanding:

Multiplexing

My prof described multiplexers essentially as electrical switches; they choose which signals to transmit. I think my biggest misunderstanding is rooted in what purpose the multiplexer serves in this circuit. Is the multiplexer represented in the schematic where it says "buffers"? Is that common? Originally, when we were using one display with the decoder, we didn't need a multiplexer. If the ultimate goal is to display the output on two additional displays, why couldn't we just wire the all the a's, b's, c's, etc. together? He also mentioned demultiplexing, but it's not clear if that's necessary here.

High End Digit Driver

The purpose of the transistor drivers are to supply/sink current to/from the LEDs, but it's unclear to what it's connected to electrically in terms of the emitter, collector, and base. If the drivers are simply sourcing or sinking current, why are they connected to the multiplexer?

Counter Circuit

I've built a counter circuit once before using a 555 timer. This is the schematic:

I believe I could use this circuit and tinker with the R values until I get a desirable output. However, what is considered a desirable output here? The procedure just says the counter circuit has to produce the digit drive signals - this seems vague.


texts:
I recently have had electrical roller shutter installed on my windows. They are wired (I put a home automation system behind, based on Shelly 2.5 (wiring)). It works great, except that the motor, when solicited, starts very abruptly.
It is powered from 0 to 230V instantaneously and therefore starts with full power which is actually a bit frightening (I still jump when it starts, especially in the morning).
The motor is a SOMFY LT 50 METEOR 20/17, its power is 160 W, current 0.75 A and the couple is 20 Nm.
Is there a way to ramp up the power supply?


texts: Plastic platform for THT electrolytic capacitor?

texts:
SMD capacitor looks like this

I did not see "plastic platform" to be sold separately.

But I want such to put under THT capacitor

so that it looks like exactly the way as quarts crystal with the gasket

I just like the way it looks, mechanically holds the the electrolytic capacitor, and separates the cap from the other components.

Does such technique exist for THT electrolytic caps?

Update:

I desoldered one of the SMD caps of the required size, and compared the constructions and tried to put THT cap in:

Both models appeared to be covered by the protective material, but up to different point at the bottom - SMD cap is required to be put into the platform/spacer. I also see that it is bad idea to put vias or anything else conductive under the THT cap as it has very small exposed area (however risk of shorting is minimal, just to be sure and have a "good practice").

Putting the THT cap into the SMD cap's spacer has failed: THT is having rubber protruding at the bottom, effectively eliminating bottom of the capacitor seating onto the conductors. However, per datasheet, it is only for some packages:

Smaller sizes are having flat rubber, and must be able to seat into the repsective spacer salvaged from SMD cap.


texts: Transmission line and termination and input impedance

texts:
I'm confused why sometimes when we look at the termination effect on a transmission line, we don't consider the overall input impedance looking into the transmission line including the load? For example, I have this:

We say, the voltage at node A before the wave propagates down the transmission line is only 1/2 of Vin because we treat it as voltage divider of Rs and Zo (voltage at node A = Vi * Zo/(Rs + Zo)). Why in this case we are not considering the total Zin (blue, the impedance looking into the transmission line) for the voltage divider? Why do we only use Zo to form voltage divider with Rs? But, sometimes, why do we try to calculate for Zin?
Thanks.


texts:
So my device has an input of 5V 0.7A, but the cable isn't detachable from the plug so I need to use a different USB to micro-USB cable.

My power bank can output on 2 ports, DC 5V 1A and 5V 2.4A

If I plugged in the device to the 1A port, it should only draw 0.7A and not 1A right? And would the same go for the 2.4A port?

The device is a wireless charger, if that's relevant. I just want to make sure I don't fry my device or watch.


texts: someone can help me explain why is ~6V at source terminal?


texts: Low-pass filter to delay pull-up on powerup

texts:
I would like to integrate a Si4703 breakout board into a project. I’m only going to use its two-wire interface, without much intelligence to drive any of the other pins. Therefore, I need to initiate the startup sequence with the most primitive means; my intention is to initiate it every time the circuit is powered up. (Resetting the thing during operation is not really a requirement—if at all, it’s OK to require a power cycle for that.)

As part of the startup sequence, I need to keeep RST_n low for at least 300 ns 30 ns after powerup, then pull it high (and keep it high). The board has an internal 10 kΩ pull-down resistor on that pin, with an extra 330 Ω resistor between the pin and the header (see linked schematic).

While some sources suggest playing with the impedance of the pull-up resistor, increasing it to introduce a delay before the threshold is reached, I am wondering if a low-pass filter is maybe a better idea.

I figured that for a delay of t, I would need to aim for a cutoff frequency of f = 1 / (2 t).

Assuming I’d use an RC filter with a 1 kΩ resistor (1/10 of the internal pull-down resistor), I would then need a 10 pF capacitor to get within the neighborhood of the delay I aimed for.

Is this going to work as intended, or am I making a mistake here? Especially, are my calculations quantitatively correct? (Admittedly, I’m more a software than a hardware guy…)


texts: Ambiguity in the Definition of Resonance Frequency

texts:
we know that in a series LC circuit the resonance frequency is defined as that frequency in which the total impedance offered by the circuit is zero.

We also know that in a parallel LC circuit the resonance frequency is defined as that frequency in which the total admittance offered by the circuit is zero.

I have seen several times analyzes of much more complex circuits (composed of several series and more parallel elements of L and C) in which the resonance frequency was defined as that frequency in which the total admittance was infinite, for example.

My question is: what is the general definition of "resonance condition"? With what criterion do we define the resonance condition for a given circuit?


texts: Constant Gain-Bandwidth product in amplifiers

texts:
Can somebody explain to me how the gain-bandwidth product is constant in an amplifier or op-amp? I want to know the mathematical expression behind it if possible.
As said here: https://en.wikipedia.org/wiki/Gain%E2%80%93bandwidth_product


texts:
I just bought this product: "Jackson PT1USB" as an attemp to get a portable charger for my netbook, ipad 2 and smartphone.

Now I am bit worried after reading in the product "total connected load to both usb sockets must not exceed 1 amp"

From my other usb chargers I read that they provide 1 amp and read that the Ipad can use up to 2. I connected my S3 phone and ipad2 for some seconds and they seemed to charge fine.

My netbook charger only outputs 2.1 amp so I guess it should be fine with the overall 10 amp limit.

I don't know much about this so I would like to know if there is any risk connecting all the devices at once. Can I damage them?


texts: I want to connect solar panels in parallel, not sure whether connecting the terminals together will work. If one solar panel produces high voltage, it will block the voltage generated by second solar panel and it never contributes to the total power generation. This is my theoretical assumption. If I have a Multiple DC input which can take range of DC voltages, it can convert variety of voltages to a single constant DC voltage output. Not finding how to achieve. Please help.


texts: How do I connect a 1 pin array to a module in pcb using KiCad

texts:
Because I searched in you tube tutorials, internet and KiCad help guide and I didn’t find anything that can tell how to connect 1 pin array to a module.

this is the type of the 1 pin array. But I'm using just one of this pin array and trying to connecting a resistor (0805) to one end and the other end use it as voltage source.


texts: Designing adjustable current source 30A to 60A

texts:
I am looking to design a constant current source that can give between 30A and 60A used for electroplating. Obviously, an LM317 isn't going to cut it for this project. Does anyone have any thoughts for a design that would allow for 10A steps (5A preferably).

My power source is an HP Model PS-3701-1 725w 60A PSU.

Thanks!


texts:
I'm using BS170 N-channel enchantment enhancement mode MOSFET and have the following circuit:

The idea behind it is that the MOSFET should act as a simple switch and turn the LED on and off depending on the status of its gate.

Well, my problem is that the LED is always on, even when the gate is connected only to ground, or directly to ground with no resistor. I've tried this with several transistors. At one point, I've had the gate floating and (as expected), I'd get various levels of light from the LED when I touch the gate. Also some of them can be now turned OFF by connecting the gate to the positive side of the power supply and with some, the LED actually is brighter when I connect the gate to the ground than when the gate is floating. From what I've read, such behavior is expected from depletion mode MOSETs, right?

Could I have killed the transistor or did I get bad parts? How susceptible to static electricity are they?


texts: What's the best method for generating 5V at 2A?

texts: I'm trying to make a crank DC charger.  I understand the voltage regulation circuitry and (if needed) the bridge rectifier circuitry, but I'm still a total noob.  I'm wondering what is the best/easiest method for getting the electricity generated?  I assume a motor will work just like an alternator, but I can't find any suitable 2A motors.  Am I looking in the wrong places?


texts:
The following is the state transition table for a Moore state machine with one input, one output, and four states. Implement this state machine. Include an asynchronous reset that resets the FSM to state A.

My Code

module top_module(
input clk,
input in,
input areset,
output out); //
reg state,next_state;
parameter A=2'b00,B=2'b01,C=2'b10,D=2'b11;

 always @(*)
    begin
         case(state)
                2'b00: next_state= in ? B : A;
                2'b01: next_state= in ? B : C;
                2'b10: next_state= in ? D : A;
                2'b11: next_state= in ? B : C;
            endcase
    end
always @(posedge clk ,posedge areset)
    begin
        if(areset)
            state<= A;
        else
            state<= next_state;
    end

assign out= (state==D);
endmodule

It is showing 29 mismatches. Please tell me where did i go wrong.
The images of output is as  shown


texts: How to build a 18650 battery pack without a spot welder?

texts:
I'm building an autonomous boat (which needs to get me a bottle of fine whisky from Scotland) for which I want to build a battery pack. The boat is currently powered by a cheap Li-ion battery pack, but I want to build my own battery pack so that I can better determine the shape of it to fit it in the boat

After reading around I decided I want to build a LiFePo4 battery pack, mainly because it's more chemically stable and heavier (I actually need the weight). The battery format 18650 seems to be the most standard, so it seems logical to go for that. As far as I understand I need a spot welder to connect the batteries together. A spot welder seems really expensive though and I don't really need it for anything else.

While searching I also found these batteries with tabs on the poles (see image below). My question is whether these can be used to build a battery pack without the need for a spot welder? Maybe I can simply connect them by soldering wires on to them?

The battery will only be charged very slowly by day, and be discharged relatively slowly by night (maybe 12V*1.4Amps=16.8 Watts or so discharge), so I don't think the wiring will become very hot.

Are there any downsides to not using a spotwelder? Is there any serious drop in performance? Or any other dangers I'm unaware of? All tips are welcome!


texts:
I am looking for a small USB to RS232 (or TTL serial) converter. FTDI was the first stop, but the smallest IC they have is in SSOP28 or QFN32. I'm looking to go even smaller. I don't need high speed - max probably 38400 baud, and USB Low Speed or Full Speed class. I can see how the pins are used up: some for data (TX, RX, CTS, RTS), USB pins (D+, D-, 5V), voltage regulator, crystal, etc.

I'm not sure what product category I should be looking for, other than FTDI's website, which I already checked. I suppose I could also use a USB micro (I already have two micros on the board), but this adds size and complexity to an already complex product. Does anyone know of any possible chips? (preferably also low component count, this is not critical but would be nice.)


texts: Dual power supply gives higher voltage as soon as load is connected

texts:
I have a +5V/+12V dual output power supply. They share a common ground. When no load is connected to 5V, both outputs read 5V/12V by multimeter. As soon as I connect a load (LCD) to 5V line, the multimeter still reads 5V fine, but suddenly starts reading 14V instead of 12V on the other output. The voltage also visibly fluctuates between 14.1V ~ 14.5V. The 5V line does not fluctuate at all. The LCD connected to 5V probably draws less than 300mA at best, which is way below the 3A maximum given from the specification.

Is this behavior normal? Why does the 12V power supply suddenly jump to 14V?


texts: I am restoring an old ROTEL turntable and have come across a "NEC MPC1003C" chip, acting (I think) as voltage regulator. I can not find any information on the internet. Does anybody know any info on this chip? Thanks!


texts: Is this a reasonable way to switch a circuit on and off?

texts:
I'm using optical slotted switches to detect the position of a wheel. I may have a dozen or so, and at any given time I only need to have one switched on. The device might be battery powered, so I want to conserve power where I can (the opto switch draws about 25mA and I guess the comparator a little bit too.). Also, I want a way to quickly see that a) the opto switch is powered on and b) if the beam is broken. This allows me to simply connect a 5V source to the circuit and fine tune the positioning of the plastic tab that breaks the beam without having to connect and run the whole system.

Here is my stab at a diagram of what I've got so far on the breadboard:

simulate this circuit – Schematic created using CircuitLab

Is there some glaring deficiency in this circuit? I suppose there must be, because although there are plenty of examples of common emitter configurations, there don't seem to be many examples of sticking a NPN transistor below a whole circuit to power it on and off.

Edit: The Slotted Optical Switch is part no HY505. It specifies an IR diode forward current of 50mA, which I took to be the max. Experimentation revealed that 20mA seems to provide adequate distinction between a blocked slot and not. The op amp was just one corner of a quad comparator I had lying around.


texts:
I am using Proteus Ares 8 to create a PCB for a simple RF circuit. I have a double sided copper board, filled with groundplane on both sides, with a single 50 Ohm microstripline across the board to two SMA sockets, just as an example:

What I am trying to achieve is what is called RF stitching between the bottom and top copper along the edge of the strip-line. Something like the following:

Here I have placed a track alternating between layers, which works, but gets unworkable when the design is more elaborate. I would like to place vias alone, but, then the copper is releaved around the via, because it's not connected to ground.

About the best I can seem to do is to use a small drill hole through the board, set up to be the same size as the via. I can make the hole coated.

However, using this method, I cannot seem to remove the relief around the board. The best I can get is is the thermal relief around the pad, but since my concern is RF grounding, I would like to remove this thermal relief.

In the pad settings, I can select different options for the relief, such as Thermal (shown above) or Thermal-X (45 degree rotated cross), but, I am unable to remove the relief completely with either the Solid or None option.

Any help or suggestions for this would be greatly appreciated.

George, M1GEO.


texts:
When Designing SMPS we calculate all the parameter on minimum DC bus voltage (eg 85Vac*1.414=100VDC), and we get require inductance for primary winding is Lp (eg 0.97mH). But in real we run on Normal nominal line ( eg 240*1.414=340), so as per calculation I observe we require inductance change to  3.2mH. How this extra inductance will be compensate.

As i understand at minimum DC volt what we get is Max primary inductance.

Formula used
Vrefleccted=110V
Fsw=100Khz
Pi=14W
Dmax=Vref/(Vref+VDCmin)
Ip=2*Pin/(VDCminDmax)
Lpri=VDCminDmax/(IpriXFsw)

Case 1:- When VDC=100V (Minimum DC)
Dmax=0.5, Ip=0.53A, Lpri=0.9mH

Case 2:- When VDC=340V ( Normal Line)
Dmax=0.24, Ip=0.33A, Lpri=2.4mH

So as DC bus volt goes up, require ind increase then why we calculate Inductance using minimum DC bus voltage.since all winding is fixed at low Vdc calculation.


texts:
I have a handheld, Li-ion battery powered project involving dual path power input (USB and AC). Initially, the circuit is wired like this:

It wasn't before long I found the problem when both USB (from a PC) and AC are present. The current from AC adapter will not only flow into PMIC but also into PC’s USB port (approx. 100mA). We consider PC’s USB port sinking current not safe and add one IC likes below:

And this is one of the many power MUX TI supplys:tps2115a

The added IC called load switch, power MUX or ORing controller has a fixed or cpu controlled priority, for example: if both USBin and ACin are attached, USBin will be connected to OUT while ACin is disconnected (via internal mosfet). This workarround is OK until I saw the absolute maximum ratings for IN1 and IN2 is 6V. I was told by my teammate that even protected by TVS, the 6V max IN pins which directly connected USB or AC adapter connectors will still be damaged by ESD. And I should looking for an IC with 18V or greater IN maximum ratings. My question is, does my teammate’s suggestion correct (I read the PMIC (which is used in my project)’s datasheet, the USBin pin is rated at 16V, so his suggestion at least makes sense…)? But with the 18V or higher voltage rating in mind, I found almost all IC classified as load switch or power MUX in Texas Instruments is 6V rated. It seems all those load switch and power MUX is for internal use only (does not connected to external connector which is threatened by ESD)… So I am confused.

Can you give me some suggestion on choosing the load switch or power MUX?

Or dose my initial direction is wrong?

Updated power MUX from TI and fairchild:
TPS25942A
FPF3042


texts: Axial inductor between the plates of a cylindrical capacitor

texts: What happens if you put an axial inductor between the plates of a cylindrical capacitor (capacitor supplied with AC signal)?


texts: Make two bluetooth modules communicate directly?

texts:
Can one buy two cheap (and identical) bluetooth chips and make them talk to each other without needing a PC or a mobile phone?

I'm guessing the answer is a basic 'NO', but I might as well ask.

i.e.:
I want to design a PCB and make a number of copies that can talk to each other, but also to a PC or mobile app.

Bluetooth still seems good for the device to app case,
but when you take the mobile or the PC away, can you leave it with the devices paired to each other and not require the mobile to host it?

Can this be scaled further to make a basic network of bluetooth. ie: if i put 5 of these one of them pair to all the others? I don't have very high bandwidth requirements.

Like I said, probably not, but it is called "pairing", which I feel implies that the devices are equal somehow.
So, what exactly is in the mobile phone or PC or bluetooth dongle that makes it different from a bluetooth device?

Also, if it just so happens that one can recommend a module, I would be really great to be able to get it for under USD$10 each at volumes. : )


texts: I'm quite confused on using this matrix equation to find the voltage across the 3ohm resistor. Once I fill in the values of the resistors for the Y values where Y=1/Z I get stuck. I'm not quite sure how to continue with it any help or tips would be greatly appreciated. I have to use the given matrix equations in the form YV = I


texts: How can we understand the motivaton and the derivation of Thevenin theorem from scratch?

texts:
There are many questions on this site abut the Thevenin's theorem. The closest question I found: Proof of Thevenin's and Norton's Theorem? but I dont understand anything from the answer.

In books and tutorials I always find such definitions: "Thevenin’s Theorem states that any linear circuit containing several voltages and resistances can be replaced by just one single voltage in series with a single resistance connected across the load" Sources should be independent ect ect..

Wikipedia says superposition theorem is employed.

Im wondering if this theorem is so simple why no one is explaining it step by step from scratch starting from the motivation.

I dont want to memorize this theorem without understanding how and why it was derived at least as a big picture.

Lets say we have a black box a network and we have input output ports with sources attached to this unknown network. How can we logically derive Thevenin theorem from this point? Theorem involves superposition theorem, linearity, being independent source and Kirchhoff's laws.

Some says Thevenin’s theorem is a direct consequence of the Superposition theorem.

Is there  a way to explain the concept in a simple fashion?


texts: A question on op amp selection in an active filter

texts:
Below is a Sallen-key type active LPF which filters out all the ac components and integrates(averages) the incoming 1kHz 1V pulse train.

There are tools to design these filters, but my question is about the op amp part:

If I change this op amp with any other single supply op amp in LTspice I get totally different results. I must say Im not into details of op amps and active filters so please answer as to a beginner.

Why is any generic op amp doesn't work for this circuit?
What determines us to choose this particular op amp here?
What is so special about LM358 here?

Edit:


texts: Can you turn a non-USB audio mixer into a USB mixer?

texts:
Ok. Pretty sure this sort of thing isn't possible but hey ho,

I have a Behringer Eurorack UB1202 multi-channel mixer.

I'm just curious if there is any way way to turn it into a USB mixer/audio-interface? Ideally with each channel being recognized separately by the computer.

If it is possible, my assumption would be that I would have to disconnect each channel from the consolidated stereo outputs of the board itself and re-route them to the computer via some sort of USB bridge thingy.

I have no idea, not in any way tech savvy :)


texts: Is reverse polarity protection required for the ZXTR2005Z regulator?

texts:
I am trying to figure out whether reverse polarity protection is required for the ZXTR2005Z regulator.
On the one hand, the datasheet is "suspiciously" explicit that the input voltage must be greater than 10V, on the other hand, if I drop 1V of an automotive supply across an additional protection diode, the whole thing drops out at 11V which seems too high. At cranking there is a chance it would drop out, right?


texts: Are FPGAs more intuitive to learn than microprocessors for doing DSP

texts:
I want to learn to make DSP hardware

I have never done any DSP and only a little bit of programming, but I have been making analog circuits for 15 years. I like the idea of learning FPGAs because it sounds more like building circuits, but people often say FPGAs are really difficult. Maybe these people are used to sequential programming. I am wondering if FPGAs are more easy to learn than microprocessors if doing the things that FPGAs are good at. For example if I want to make an FIR filter, will an FPGA will be more intuitive?


texts: Rectangular selection for component designator in altium

texts:
I noticed that is not possible to use rectangular selection for designator in Altium (PCB view). I have to select them by clicking on each of them.
And for moving a group of them I can't use keyboard shortcut.

I understand that designator is not a object by itself but is attached to a component (unlike the text objet)

but there is a way to rectangular select on a group of designator and change value of them ?

EDIT :
Partially found a way. Go to top layer, select the component via rectangular selection (with component filter activated), then, click on the blue text "Designator" for all selected component. It select the corresponding component's designators.


texts: Identifying a four-pin IC labelled EL 8+7 G8025

texts: I want to know the purpose of a component named "EL 8+7 G8025" which was found inside a Nokia charger.


texts: Physically determine unknown wire's gauge

texts:
Is there any way to easily and accurately determine the gauge of stranded wire by measuring it?

I know you can pretty easily determine the gauge of solid-core wire with just a pair of calipers by measuring the conductor diameter, but with stranded wire, wouldn't there be variance in packing-efficiency of the strands? I also had little luck finding a wire-gauge to stranded-wire-diameter table.

I have a bunch of spools of wire that are incorrectly labeled. It appears that someone has respooled a number of the reels, as there are (at least) multiple reels all labeled "22 gauge" with different diameter wire on them.


texts: Sinusoidal voltage source not being sinusoidal in LTSpice

texts:
I'm trying to obtain the output resistance (resistance from collector node) of the following circuit

By inspection, it should be the output resistance of a common emitter amplifier with degeneration

$$R_o = r_o(1+g_mR_1)$$

This transistor has

$$I_c = 20 mA $$
$$V_A = 36$$
$$r_o = \frac{36 V}{22mA} \approx 2k\Omega$$
$$ g_m = \frac{20 mA}{25 mV} \approx  720 m\Omega^{-1}$$

So its output resistance should be

$$R_o = 2k\Omega(1+720 m\Omega^{-1}250\Omega) \approx 360 k\Omega$$

However, the simulations are giving strange results. I tried simulating a small sinusoidal voltage at the collector and measuring the current as to get the resistance of the node, but trying to get the voltage amplitude below 1 V yields very strange results. Here are some captures of the voltage at the collector, which should be sinusoidal, but it isn't. The frequency of operation is 1 kHz

1000 mV ampltiude:

100 mV amplitude:

10 mV amplitude:


texts: Extreme Fiber Coupled Laser Diode Power Loss Causes

texts:
What could cause a laser source with fiber coupled laser diodes to have extreme loss of power? The laser diodes have a wavelength of 658nm and have an output rated at 60mW but it seems as though the optical channels actually output ranges between 58 to 70mW.

During some troubleshooting I noticed that one of my optical channels had a loss of -13dB (95%) so I cleaned the fibers to make sure there was no blockage but when I remeasured I was only given a small gain of maybe +30dB (0.1%). I decided to spot check other channels and noticed that they also had significantly dropped in power.

The sources had been on for awhile so I thought that perhaps the sources had been on for too long. I shutdown everything down and proceeded to do a power check the next day after they had cooled but unfortunately the output was still extremely low.


texts:
I need to use mt9p111 (LI-5M05CM-AF), but I can't find any initialization examples in Internet. I found drivers for linux and android at github: (Link in comments).

I didn't see any results of mt9p111 initialization with I2C. A sent registers table but didn't see any data on cam data bus.

Sun time later I saw, that serial interface not initialized (look upper linc, code string 3278) and tryed to change it to parallel. But I didn't see any data again.

Should I switch on data exchange, wrigting some command in some register? Later I reduced init code http://pastebin.com/Zyv2zPfY

Here is datasheet: https://drive.google.com/file/d/0B1V89BcPR7z7RmlnWDRhLVdoem8/view


texts: Can someone tell me if my doorbell wiring is low voltage?

texts:
I've not seen a pink and black wire-combo. Does that mean it's low voltage?
here is a pic...


texts: How do I find the resistive energy deposition of a flat braided aluminum?

texts:
I have a flat aluminum 6061, and the measured resistance is 0.5mOhms.
I have read that the resistive energy deposition is proportional to the action integral of the lightning current.
In the end, I would like to know the amount of power deposited into the aluminum.
I was able to find the formula, and it's shown below.
How do I find the action integral.


texts:
I've got a 220 volts fishbowl pump that is conected and working 24x7.

However, when a power outage happens (they happen often where I live) I need to switch to a 12 volts version of the same pump, so the pump never stops working.

I can, buy 2 different version of the pump, one ready for 220 and the other one for 12 volts, or, if possible, use the same pump.

Do you guys know of any circuit that maybe already exists for this?, or should I make one "home made"?.


texts: Can Two Or More ATTinys Share One External Crystal?

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I've got two I2C Slave ATTiny85 chips both running at 16MHz with external crystals. Can they both share a single crystal with the 22pf caps? Is there anything wrong with this?

I don't have any free pins on the ATTinys to route a clock signal out of one ATTiny into another.

If there's some type of external clock circuit, how is that constructed and connected/shared with both ATTinys.

simulate this circuit – Schematic created using CircuitLab


texts: DC Motor Efficiency at a given operating point

texts:
I'm trying to select a motor for a design application that cares mostly about efficiency. Given a required torque and RPM output from the motor, I feel like it should be possible to calculate the efficiency of that operating point given a spec sheet. However, take the spec sheet on page 8 of this pdf for example:
https://www.magneticinnovations.com/wp-content/uploads/2020/07/Brochure-Frameless-High-Torque-Motors_MI-F18V1web-std-res.pdf
There doesn't seem to enough information to calculate the efficiency for a given operating point. I feel like you would need the viscous drag (Nm/rpm) and static torque (Nm) as constants to be able to then multiply by the RPM to get the iron losses, and add them to the copper losses which can be found using the resistance (which is included). The total loss can be then compared to the output (torque * rad/s) to get efficiency. However, most data sheets don't have those two constants. Is there another way using the other constants? Is there something obvious I'm missing? This is a PMSM. With some BLDCs, given the no-load current, Kv, and R, you can match a supply voltage to get to the right torque-RPM point, and then find the efficiency that way, using (torque * rad/s)/(V * I).


texts: Why doesn't an RC circuit change the shape of an input sine?

texts:
In above picture, red square wave is the input and blue wave is the output of an RC circuit. I'm not able to understand why I get a perfect sine wave when I feed a sine wave as input. The capacitor has to take some time to charge and discharge. So my intuition cries the output to be some periodic wave whose period is half the input. Could somebody clear this up for me ? Thanks!

In time domain shouldn't it do something like this ?
At t=0, the capacitor has 0 voltage. Since the input voltage is large, the capacitor keeps charging and meets the input sine wave when its falling.

Then the input voltage goes lower than the capacitor voltage, so the capacitor starts discharging and again meets the input sine wave when it is rising.


texts:
I am designing a blinker circuit in Eagle. These blinkers are used at roadside for indication purpose. These blinkers contain two PCBs. One is PCB contains 555 timer circuit which generate timing. Another PCB contains all the leds. I will be using 12v. I have connected 4 leds in series to make a string and then using 25-26 strings in parallel. I have designed the schematic. But need some help regarding board layout.

As these PCB needs to be in circular shape, so for that I have drawn circles in board layout and planning to put leds on them. Is this the correct way of designing board layout for such kind of PCBs. I also need to put every led at an equal distance to make a proper PCB. Does any one has any experience in designing board layout for these PCBs. Any help or any link would be very useful to me.

Following is the way I am doing it.:

I have drawn circles and putting leds over them. After routing, I will delete the circles and the circuit will be in the proper shape. This is all I can think about designing this circuit. And for the equal distance between leds, I am not using any measuring technique, just putting them with random guess.


texts:
I was reading a document where it says

  Adjust the signal generator to apply a 1mV peak-to-valley input 6Hz
  triangular signal at a gain of 0.001mm/µV.

What does peak-to-valley mean hear? Is it same as peak to peak?
And, what does mm/µV mean?