texts: At what frequency does jumper wire stop functioning properly?

texts: I have designed an IC with some digital circuitry requiring a 25 MHz clock signal. Now I'm designing a PCB to perform testing. My question is, would normal jumper wires be sufficient to pass a 25 MHz clock signal, or would it create signal integrity issues? Should I go for an SMA connector?


texts:
I've been tasked in designing logic for dorm rooms. The design of the dorm is that that two rooms share the one bathroom (roomL-door-bathroom-door-roomR). I'm having trouble designing logic for it. Here are the requirements:

If a person from roomL enters, person from roomR is forbidden to enter.
A person can't move between rooms through the bathroom.
(Desired but optional) If a bathroom is occupied by person from roomL no one from roomL can enter.

Each door will have electromagnetic lock (normally open in case of emergency) so I can lock the door through software. I was thinking this:

Doors are normally unlocked. If a person opens the door from roomL, door from roomR will lock.
He would have, lets say, 30 seconds to press the occupied push button (timer is there to prevent people from leaving the door open).
After it's pressed both doors will be locked.
When the button is pressed again it will unlock the door from which the person came (PLC will remember the last door open).
When a person exits the room and closes the door it will unlock other room's door (again, 30 sec after pushing the button the doors will be unlocked).

Is this a good design?

UPDATE

So I've revamped the design and the logic that can be seen from the diagram bellow. I don't see any holes in this new design but a fresh pair of eyes couldn't hurt!


texts: Are these 433Mhz receivers likely to be able to physically receive signal from this?

texts:
Does anyone know if the 433Mhz receiver boards like the ones I picture below  are physically capable of receiving transmissions from These Trust wall switches?

I have both, and am willing to spend time on the software required to recognize a signal but would like to know if the boards are physically able to receive it. They both claim to be 433Mzh based...


texts:
I am working on physics research, and I am using the DC High voltage supplier ~30KV from the wall AC power.

I am not sure what is happening, but when I apply more than 3kV it start to interfere with other device such as computer monitor is blanking. Not just monitor, I think it make all other electronic device to be blinking, such as some of our feedback control and power supplier.

I don't really have good knowledge about the electronics. What can be possible issue? I am afraid too much voltage is going to ground and that ground is affecting other device's ground? or does it create the magnetic field, so do I need some shield around it?

For more detail, I am applying the power to the Rubidum85 atom contained cell, and apply at the two small plate distanced 2.5mm Which will create the electric field in order to see the energy level shift on atom.


texts:
I was measuring a 10pF 0603 +-5% (Johanson 251R14S100JV4S) using a network analyzer at 319.5MHz. The cap came in their high q/low ESR ceramic kit.

It measured about 10.7pF. But after measuring a few more 10pF parts, I noticed the capacitance was either around 10.7pF, or 11.3pF, give or take .05pF. Even after checking a dozen or so, they were all grouped around 10.7 or 11.3. In other words, NONE were 10.9 or 11.1.

Any idea why? I know the nominal capacitance is different at frequencies other than their test frequency, but I guess I expected them all to center around some value and be randomly sprinkled within 5%.


texts: Two MinIMU-9 v2 with LPCxpresso, or Arduino Uno/Mega

texts:
I am working on  a project that interfaces two IMU sensors to one microprocessor (NXP LPCxpresso). The purpose is to read both of gyro and accelero at two different place on the bodies. I have foolishly rushed to buy this product:
http://www.pololu.com/catalog/product/1268

The sad thing about it is that "The accelerometer’s slave address is fixed to 0011001b", so I cant use two different I2C addresses for two IMUs. (but it is possible in version 1 of this sensor!).

Is there anyways I can overcome this dilemma? I am also thinking about switching to MPU-6050, but sadly, I cant find a library for MPU-6050 for LPCxpresso.

Could you please giving me some suggestions?


texts:
Is it because it can exceed the reverse breakdown voltage of semiconductors?

For instance in low voltage devices say 1-5v is the reverse voltage rated a lot lower than that for damage to occur?

Also I watched a video where a car battery was accidentally connected backwards and the main 80 amp fuse blew yet no other damage occurred. Makes me wonder what failed that drew so much current?


texts: Some Power Supply Questions - Multiple Rails or Single Rail w/ multiple Outputs?

texts:
I'm interested in making myself a 12V power supply. I need one because I often go out to places with little or no power and need some electricity to power my gear (which is basically a telescope, a camera and some accessories - all run on 12V).

I don't want it to be powered by mains and would instead use a 12V deep cycle battery. For regulation, I'm going to be using 7812. I need about 6 outputs, each capable of 4A. My question is this:

Is it better to regulate each output separately with a 7812 (with a power transistor for increased current capability) or use single 7812 with several power transistors, for a current rating of, say, 25A, and then split this into 6 outputs.

Secondly, since I'm using a 12V battery I understand that regulation is not going to be good as Vout is also 12V. Unfortunately, I can't get a new battery so I was thinking, perhaps, stepping the voltage with a DC-DC Converter to about 14V and then feeding this voltage into the regulator will help with regulation. Is this a good idea?

I require some decent regulation as my telescope is quite sensitive to the power's quality. I apologize if these are boneheaded questions, but searching the web did not return good results.


texts:
I am making a "lightbar" for my vehicle which consists of 7x 6" diameter spot lights linked together.
The specs for each of the individual lights are below:

LEDs: 14x 3w OSRAM
Max Watts: 67w
Input voltage: 9-32vdc
Current Draw @ 13.8v: 5.6a

I have just finished wiring the lightbar, which I specced the wire thickness based on some previous bench testing of 2x lights connected to a 40a switching powersupply.
When I did this initial bench testing, 2 lights drew 6.5A @ 12v.
So, when I specced the wiring, I allowed for a total of 28a of peak load (6.5/2)x7 + bit for headroom.
I have just gone to test the whole array and my amp draw has increased considerably and I dont know what to do now, as I have some hard limitations which I need this lightbar to work to.
To bench test the power supply, I plugged in 1 light at a time, to check the amp draw. Instantly, just 1 light was drawing way more amps than my previous bench test!. The next odd thing that happened, was that at light 6, the volts dropped to 7.4 volts, but the amps stayed the same. The lights obviously dimmed as well. 30a was all I could push through the wiring and connectors as I didnt want to start a fire.

1 light: 4.8a @ 12v
2 lights: 8.4a @ 12v
3 lights: 13.8a @ 12v
4 lights: 17.9a @ 12v
5 lights: 17.9a @ 7.4v
6 lights: 22a @ 7.8v
7 lights: 30a @ 8.4v

So, the hard limits I need to work within are:

I use a Switch Pros SP9100 to control lighting circuits, which has a max output of 35a. So ideally, I need the load to be below this. Obviously, I could run a 70a relay to switch more current, but its added complexity.
I dont really want to have to rewire the lightbar, which is currently wired to handle 28a.

So, firstly, I would love help to understand the below questions.

Why did my initial bench test show such a low draw compared to testing today?
Based on the above load @ voltage results, whats the total estimated amp draw the lights would make if they were plugged into my vehicle, which can provide upto 14.6v when running.

for solutions, I have gotten to this point.

Use a 12v-24v step up converter, which will from my understanding, half the amp draw? But, what I am confused about is; A) Does the converter still draw the full watts (7 x 67w = 469w / 12v = 40a)therefore my switch pros 35a output would still need to use a relay circuit?? B) Does the draw of the lights half @ 24v, so I would need a 20a step up like this https://www.ebay.com.au/itm/New-DC-12V-to-24V-20A-480W-Step-up-Boost-Converter-Power-Supply-Module-for-Car-/321846640256 ?
Rip all of the wiring out, beef it up to handle 40a of current and then use a 70a relay, switched from my Switchpros?

Im sure this is all fundamental electrical stuff, but it really threw me how badly I got the draw estimates wrong.
Thanks
Ned


texts: Reommended wire gauge for prototype boards?

texts: What gauge of solid wire is recommended for wiring on prototype boards?


texts: What is this schematic symbol? (Two small circles connecte by a bent line)

texts: What does this symbol mean? It's part number is XM## and is connected in series with the output voltage of a chip.


texts:
I have a customer requirement where we have to design a GPIO controlled switch. We are using NPN transistor, where when the GPIO is high(3.3V) transistor is enabled and it acts as closed switch, when GPIO is driven low(0V) transistor is disabled and acts as closed switch.
When the transistor is enabled the voltage across emitter is used to enable the regulator.
The below is the attached circuit image. When the transistor is enabled what will be the voltage across emitter pin.


texts: Powering Several Electrical Components from Single Three-Phase 240V AC Supply

texts:
A system consisting of various electrical components is desired. Required supply voltages to power these components include the following: three-phase 240 V AC (directly through the supply), 24 V DC, 5 V DC. Are there any reasons in particular one may be hesitant to regulate power through this single available three-phase 240 V AC supply? Is it dangerous to step down from such a high voltage to reach 5 V DC? Are there potential stability issues? Does it not make sense to convert between three-phase and single-phase power?

If this option is indeed viable in practice by what means could it be regarded as both safe and effective to provide voltage regulation? Could a power supply simply be connected directly to the 240 V AC source? Or possibly some sort of custom step-down transformer?

This is a convenient powering option since no other power supply outlet lies within proximity of the system.


texts: Microcontroller USART receiver doesn't work

texts:
I know it's some PIC(18F45K22) specific but I want to ask because I haven't been working for a few days.
Although I see the signal with oscilloscope on the RX pin, I could not any data in software.
EUSART1 = RX pin only
EUSART2 = TX pin only
Sending data with EUSART2 works, but receiving data with EUSART1 doesn't work neither polling nor interrupt.
#define _XTAL_FREQ 16000000 //Internal oscillator
#define USE_OR_MASKS

#include <p18cxxx.h>
#include "usart.h"
#include "stdint.h"
#include "config.c" //There are pragmas

unsigned char Rxdata[32];
unsigned char Txdata[] = "MICROCHIP_USART";
char PM_byte;

void EUSART1_config(void);
void EUSART2_config(void);

void main(void) {

    int i;
    OSCCON = 0x7C; //16MHz
    TRISCbits.TRISC6 = 1; //EUSART1
    TRISCbits.TRISC7 = 1;
    TRISDbits.TRISD6 = 1; //EUSART2
    TRISDbits.TRISD7 = 1;
    TRISAbits.TRISA1 = 0;

ANSELCbits.ANSC6 = 0;
ANSELCbits.ANSC7 = 0;

ANSELDbits.ANSD6 = 0;
ANSELDbits.ANSD7 = 0;

    INTCONbits.GIE=1;
    INTCONbits.PEIE=1;

    EUSART1_config();
    EUSART2_config();

    TXREG2 = 0x35;
    __delay_ms(100);
    TXREG2 = 0x34;
    __delay_ms(100);
    TXREG2 = 0x33;
    __delay_ms(100);

    while(1)
    {

            //UART1 data received Flag
            while(!(PIR1bits.RC1IF)); //Cleared when RCREG1 is read

            //if error
            if(RCSTA1bits.OERR)
            {
                RCSTA1bits.CREN = 0;
                NOP();
                RCSTA1bits.CREN = 1;
            }

            //Get char UART1
            PM_byte = RCREG1;

            //Send char UART2
            TXREG2 = PM_byte;
            while(!TXSTA2bits.TRMT);

        //__delay_ms(1000);
    }

    return;

}

//TX only
void EUSART2_config(void)
{
    SPBRG2 = 25;
    SPBRGH2 = 0;

    TXSTA2bits.BRGH = 0;
    BAUDCON2bits.BRG16 = 0;

    TXSTA2bits.SYNC = 0;
    TXSTA2bits.TXEN = 1;
    TXSTA2bits.TX9 = 0; //8bit
    TXSTA2bits.CSRC = 0; //dont care
    RCSTA2bits.SPEN = 1;
    RCSTA2bits.CREN = 1;

    PIE3bits.RC2IE = 1;
    PIE3bits.TX2IE = 1;
    PIR3bits.RC2IF = 0;
    PIR3bits.TX2IF = 0;

}

//RX only
void EUSART1_config(void)
{
    SPBRG1 = 25;
    SPBRGH1 = 0;

    TXSTA1bits.BRGH = 0;
    BAUDCON1bits.BRG16 = 0;

    TXSTA1bits.SYNC = 0;
    TXSTA1bits.TX9 = 0;
    RCSTA1bits.SPEN = 1;
    RCSTA1bits.CREN = 1;

    PIR1bits.RC1IF = 0;
    PIR1bits.TX1IF = 0;
    PIE1bits.RC1IE = 1;
    PIE1bits.TX1IE = 1;

}

//__interrupt() void ISR(void)
//{
//
//    if(PIR1bits.RC1IF==1)
//    {
//            TRISAbits.TRISA1 = 1;
//           //if error
//            if(RCSTA1bits.OERR)
//            {
//                RCSTA1bits.CREN = 0;
//                NOP();
//                RCSTA1bits.CREN = 1;
//            }
//
//            //Get char UART1
//            PM_byte = RCREG1;
//
//            //Send char UART2
//            TXREG2 = PM_byte;
//            while(!TXSTA2bits.TRMT);
//    }
//}

I apply all register setting reading datasheet, i don't receive data from EUSART1. What can i do to find the solution?
EDIT1
I realized that pins which are used by EUSART also can be analog. Disabling it from analog, i can get data from RX pin now. Is my detection correct?
ANSELCbits.ANSC6 = 0;
ANSELCbits.ANSC7 = 0;
ANSELDbits.ANSD6 = 0;
ANSELDbits.ANSD7 = 0;


texts: Differential amplifier and random signals

texts:
I would like to ask if I can amplify a random signal (picture 1 right hand) with a differential amplifier(picture 1 left hand) and how this will work.I know how the differential amplifier will work with sinusoidal signal but I have no idea with a random signal.Can someone help me?

Example of simulation result when input signals is sinusoidal and when input signals is random


texts:
I am reading the Intel D1000 Reference Board Schematics. I see the following block:

I located the J8 chip on the physical board. But I only see PIN1~PIN20 marked on it.

So what does the MH1~MH4 mean? It seems MH1/3 and MH2/4 are connected, respectively.

ADD 1

Inspired by @bitsmack 's answer, I replaced my image to include more details.


texts: Combining MUX 4x1 to represent 5 variable function

texts:
I have the following function

x’y’zw’v’ + x’yz’w’v’ + x’yzw’v’ + xy’z’w’v’ + xy’zw’v

I should implement it using only 4x1 MUX (more than one allowed, of course). I'm clueless on how could I combine 4x1 MUXes to handle 5 variables.


texts: Relation between transit time and rise time

texts:
In the homework I have been working on, I encountered with such a statement:

If the rise time over transmit time in a circuit element is greater than 6, the circuit element can be treated as a lumped circuit element.

However, I couldn't understand where 6 comes from. If somebody can explain this, I will be really happy.

Thanks.


texts: change software configuration of a BLE device with a smartphone app

texts:
Would it be possible to change the software configuration of an nRF51822 over the air from an iOS application for instance ?

I'm interested in being able to change the UUID, the MINOR and MAJOR and the IDENTIFIER if it's possible (more info here on what the just mentioned terms mean).


texts:
I'm trying to design a BLDC motor controller rated to run a 200kW electric motor, 240v dc ~833A. Looking at MOSFETs I've found a TO264 n-channel which is rated for 500V 100A. How are the legs not going to immediately act like fusible links and vaporise?

Edit: I've found a more suited MOSFET [IXFB210N30P3][1] which is 300v 210A Rds of 14.5mOhm continuous power of 1890W.

[http://ixapps.ixys.com/DataSheet/DS100463A(IXFB210N30P3).pdf][1]

Edit Dos: it appears, in the data sheet, that there is an external lead current limit of 160A and that the chip capability is 210A


texts: Ungrouping synthesized modules in Synopsys Design Compiler for better synthesis results

texts:
I have a large multi-input multi-output design where each primary output is written in terms of primary inputs. Because the design is so large, DC is unable to synthesize the circuit. A straightforward solution is to synthesize each output individually and later, synthesize the bigger design by instantiating these smaller modules. However, I think there is a lot of room for optimization because all output functions share the exact same inputs.

Does ungrouping different designs optimize mostly around the boundaries or will optimize the whole design regardless of whether each smaller module has been synthesized before or not? If it optimizes the design as a whole, is there an advantage to synthesizing smaller modules first?

In other words, I like to use a divide and conquer method that synthesizes smaller modules first, but takes advantage of the fact that small modules share the same inputs and optimize around boundaries. Is there a set of DC commands that can achieve this?


texts: Protect against large current spikes while not reducing consistent current input?

texts:
simulate this circuit – Schematic created using CircuitLab

I have a fairly straight forward transimpedence amplifier to convert collected current from ions into a voltage.

My biggest problem is the cup has to be placed far away from the ionization source. Because (And this has happened quite a few times) even a very brief arc from the ionization source onto the cup is a huge surge in current and just fries the op amp.

So this has the dual problem of frying a bunch of my op amps and causing me to place the faraday cup so far away from the source that even with such an enormous gain, I'm still experiencing an 100mV output at most.

What are potential methods I may use to protect my op amp from these large current spikes while maintaining the constant current I expect to be coming from the ions?


texts: Measuring low voltage AC current with a multimeter

texts:
I know that with DC you can measure current by putting your meter in series with the positive supply.

I have a project running off a low voltage AC supply.  Can I do the same?


texts: Why is my VHDL clock signal so far off from what I thought it would be?

texts:
I'm new to FPGA and VHDL.  The following code was supposed to be 5MHz but I'm getting 4.167MHz on my scope.

The FPGA board I have is a Mojo v3 that has a 50MHz clock.

What am I doing wrong?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity clock is
    port (
        clk_50mhz   : in    std_logic;
        rst         : in    std_logic;
        clk_out     : out   std_logic
    );
end clock;

architecture Behavioral of clock is
    signal prescaler    : unsigned(4 downto 0);
    signal clk_out_i    : std_logic;
begin
    gen_clk : process(clk_50mhz, rst)
    begin -- process gen_clk
        if rst = '1' then
            clk_out_i   <= '0';
            prescaler   <= (others => '0');
        elsif rising_edge(clk_50mhz) then   -- rising clock edge
            if prescaler = X"5" then        -- (50_000_000 / 5_000_000) / 2
                prescaler   <= (others => '0');
                clk_out_i   <= not clk_out_i;
            else
                prescaler   <= prescaler + "1";
            end if;
        end if;
    end process gen_clk;

    clk_out <= clk_out_i;

end Behavioral;


texts:
Refactoring the question as requested:

I'm doing a small home automation project. The circuit I'm trying to control using an ESP8166 is this:

LOAD: 220VAC / 1A

To be able to control the circuit using the ESP and the mechanic switches, I need to plug a 4-way switch in the middle.
Something like this:

My idea is to use a latching DPDT relay with crossover NO/NC, like this:

So, in the end, I'll have something like this: (minimal schematic, missing protection circuits, external source for relay, relay in's, ..)

simulate this circuit – Schematic created using CircuitLab

My main question is: Is this correct ?

My second question is: Is it possible/better to use a mosfet+bridge rectifier instead of the relay since 1. a mosfet switches faster, 2. the relay wears-off faster


texts: Battery Bank - How to achieve full amp-hour ratings with simultaneous series & parallel connections?

texts:
I have four 12V batteries (all with the same watt-hour rating), and I would like to achieve dual voltages by interconnecting them, while achieving the following:

48V at the full amp-hour rating of the combined batteries.
12V at the full amp-hour rating of the combined batteries.

I am building a robot for my thesis and have the following constraints:

Space limitations - I cannot put as many batteries as I want to achieve the high amp-hour ratings with multiple voltage levels.
I have a 12V inverter (12Vdc to 120Vac) that is feeding 120Vac to my stepper drives - this means that I need lots of amp-hours as I can't run out of power after a short time. Essentially I need 12V with the full amp-hour rating of at least 2 batteries (connected at a single location - a true parallel).
The 12V to 120Vac conversion is wasteful, and in general steppers are very wasteful as well, so I bought servos which are powered with 48Vdc - this means that I need 48Vdc at the full amp-hours of my battery bank.

Solutions that do not fly:

Connecting the 4 batteries in series and grabbing a single 12 volt tap form one of the batteries to feed the inverter. This means that the 12V will have watt-hour ratings of only one of the batteries which will not be enough.
The inverter takes only 12V. I cannot change the range of the voltage input to the inverter.

I am fresh out of ideas. I am hoping someone can think of a novel idea with connecting high watt diodes.

If I may provide any additional information please let me know.


texts:
Is it possible to access USART1 on the NUCLEO-F030R8 board? the datasheet does not mention it at all (only bringing up USART2), but according to the specifications of the processor it should be possible as the PA10 and PA9 (rx and tx) pins are on the developement board.

I'm not getting any errors when trying to print from it, but i'm not getting any output. The same code works great when using USART2.


texts: Need guidance for latching output of op amp (N-channel mosfet)

texts:
There are a lot of schematics online for high side switch latching using a p-channel mosfet or PNP transistor, (I) couldn't find any for low-side so I tried to design my own:

simulate this circuit – Schematic created using CircuitLab
I want to when output of op amp goes high mosfet stay "on" even when the op amp output goes low until SW3 is pressed. the circuit kinda/sorta works in a crude simulator but there are two problems:
First; When op amp output goes low from high, mosfet gate voltage reduces to ~2.5V even if I disconnect Q1 emitter from Q2 collector and connect 12V supply to Q2 collector. obviously because the base is at 2.5V...
Second; I want to use a normally open push button instead of normally closed.
Note: I know adding a diode from op amp output to the non-inverting input of op amp can keep the output of op amp latched but that will disturb/change the voltage at non-inverting input which is not desirable.
How can I solve the described problems? is there a better approach to do this?


texts: Most bare-bones way to use a CPU? (How to learn)

texts:
I know a bit of programming but am brand new to lower-level stuff so please forgive the naivety of this question. What would be the most direct way of executing a series of commands on a CPU to do a basic addition of 1+2=3? For example, at a relatively high-level, I could buy a micro-controller such as an an Arduino and write C code and compile it/execute it on the device, for example:
int main() {
    int a = 1;
    int b = 2;
    return a + b;
}

Would it be possible to purchase something like an Intel i7, and, execute the assembly (compiled binary) on the chip without a whole bunch of peripherals? I guess my question is, given a CPU, what is the bare minimum that would be needed in order to execute instructions on it and return/receive some sort of output? I know in "build-your-own-computers" there's the CPU, Motherboard, RAM, monitor. power-supply, etc. but what would be the most bare-bones way to do this?
The point of this is I'm learning assembly/instructions and I'd like to go as low-level as I can go to understand how the components work, without going into the actual electronics fabrication (other than settings things up/connecting them).


texts: Non-isolated circuit question (connecting to notebook)

texts:
I want to build a non-isolated circuit on the protoboard and connect it to the notebook via USB port.
That is, neutral of power line/outlet will be connected to GND of USB port... in short...
I want to use a isolation transformer between the power supply of the notebook and the power line/outlet. Will my motherboard blow?
Regards.


texts: Could someone identify this variable resistor?

texts:
I'm trying to find this part online, to replace it, as it broke. However, using the text on the part, I wasn't able to find anything.

Could someone help me? The board itself would be 200$ to replace, so it'd be way better if I could just use the old board and repair it.


texts: What does the AND gate do to prevent electrical current?

texts:
I’ve been learning about Boolean algebra and I’m curious as to why 0 AND 1 is 0. In a computer’s circuit, I’m imaging 1 being electrical current flowing through the circuit, and 0 being no current is there. 1 meaning “something”, 0 meaning “nothing”.
Internally, what does the AND gate do to prevent electrical current from flowing through the gate even if there’s some current coming in from one side of the circuit?


texts: How can you increase the speed of an external GPIO interrupt in stm32f4?

texts:
I am trying to measure the speed of a DC motor using IR sensor. My motor had a disc attached to it with only 1/4th part of it reflecting. I wanted to enable the interrupt at both falling and rising edge so the interrupt routine will be called twice in that 1/4th reflecting region whose distance I already know.

My ISR will enable the timer the first time around and disable it the next time the interrupt is called. The problem (which I found by studying the behavior of a variable) is that when I make the sensor react quickly, my interrupt is generated only once and not when the reflecting surface disappears. But, when I move something slowly in front of it, then both occur perfectly.

So, my conclusion is that my interrupt is not reacting fast enough.What do you think is the problem?


texts:
I'm interested in calculating series termination resistors for my communication lines for a system I'm designing based on the Zynq-7000 SoC. The system runs on a 33 MHz clock but I'm sure the bandwidths I need to consider are much greater due to the rise time of the signals (I'm interested in just the processor right now). I tried looking for rise times of this SoC's signals, and even tried to find it for generic ARM cortex A9 processors, but wasn't able to come up with anything.

How would I go about finding the rise time to ensure the termination resistance I implement are appropriate for my system?


texts: Can I drive a low voltage stepper motor with an A4988 driver?

texts:
I have this stepper motor with the following specs:

Model: 17HS4417
Rated voltage: 2.55V
Rated current: 1.7A
Phase resistance: 1.5 ohms
Phase inductance: 2.8Mh
Holding torque (min): 40N-cm.
Detent torque (max): 2.2N-cm.

I want to know if an A4988 stepper motor driver would be appropriate for this motor.  I suspect not because the driver specifies an 8-35V rating, while the load is rated for 2.55V.

If not, should I look for a driver with a lower voltage rating?


texts:
I was reading the datasheet of a switching powersupply RT8251. In the layout recommendations there is a statement -" Connect feedback network behind the output capacitors.
Keep the loop area small. Place the feedback
components near the RT8251"
What does it mean by behind output capacitors. Consider the chip->Inductor->Output Capacitor->Feedback resistor tap point or is it chip->Inductor->Feedback resistor tap point->Output Capacitor
A screen shot is attached. For that matter which is the apt point where I should tap the feedback resistor from the Vout ?


texts:
I need to make a computer fan powered by 12v that turn on when the heat is like over 40 degree and to power off if the heat drops down.

I asked in many Facebook pages and some told me i need a thermistor, and no body have a clue what type of thermistor that works for this solutions.

Any help please.


texts: Is it possible to connect Xbee module (Using Xbee shield) as well as Bluetooth module at the same time to any of the Arduino boards like Uno? Most of the sites give information about connecting one module at a time to Arduino boards.


texts:
I am rewiring a relatively old GE OEM motor and the high voltage part of the wiring diagram is marred. I know the motor works on 120V so its not an issue of functionality. If someone who is better versed in wiring could sanity check my interpretation that would be greatly appreciated. I don't want to cook this thing. Comparing the colored wires to the low voltage on the left, I read this is as:

Purple P1 to L1
Brown P2: Insulate
Red J10, Orange T3, White T2: pigtailed
Black T5, Yellow T4: to L2
Ground


texts: DO-160 indirect lightning requirement confusion

texts:
I am looking at many tvs diode online, and I wanted to know how to calculate to check if it complies with DO-160 indirect lightning surge protection.

For DO-160, there are Waveform 3, 4, 5A&B, and each waveform has its own requirement. Can some please give me an example on how to check if the tvs diode complies with each waveform.

I am also worried about certain phrase such as pin injected, cable injected, and multiple burst, single burst. I don't know what is going on.
Please help out.

Please explain what is going on with the requirement and how to calculate as an example.


texts: Ground loop, Notebook to PC audio daisy chain

texts:
Good evening fellow electro experts,

please bear with me. My knowledge about circuits is somewhat basic.

I've recently set up an audio chain from the speaker/mic combi jack of my notebook to the line-in jack of my PC. This way, I got the notebook sound on the headset connected to the PC.

The setup was working fine until I decided to plug an monitor to the notebook (in addition to the integrated one). Unfortunately, I hear an annoying electrical noise/interference whenever hold the HDMI cable of the monitor to any port of my notebook. Not just the HDMI port either, any port.

According to my research, I might have created a ground loop but I've no idea how to fix it.

The overall setup is like this:

One outlet, one outlet strip (kind of hanging from the desk atm), PC (under desk), Notebook (on desk), PC monitor (on desk), notebook monitor (wall mounted) and a simple ethernet switch (under desk) are connected to the outlet strip. In addition to that, notebook and PC are both cable connected to the switch. Notebook audio jack / PC line-in jack are connected with a male-to-male 3.5mm cable.

Unplugging the notebook from the outlet strip and from the switch didn't make any difference.


texts: when do I need to have a floating/non-floating input at a SMPS?

texts:
I am studying reference designs for my PSU, and they all have a floating earth connection (or have no earth connection). When I inspect industrial power supplies, some have earth connection, some have only L/N inputs. How do you decide when one must have an earth connection or not.

Secondly, how do I convert a non-floating AC PSU input to floating type? E.g., on the below circuit


texts: Can I charge a super capacitor with a MPPT?

texts:
I already did some testing.
I have a 220mW solar panel that charges a 3V supercap (takes a long time) which eventually powers my wifi module that needs ~1.5W (1.5 J/s) for 1 second then ~90mW (0.09 J/s). I have a boost converter after the supercap to keep steady voltage for at least 30 seconds until module dies out, which is okay for now.
My main question is, is it possible instead of using the MPPT to charge a battery, can I use it to charge my supercap? I want to maximize the charging time. Right now with my solar panel, the efficeny is terrible. I can get 2.85V, but the current is around 0.03 amps. Which charges my capacitor super slow.


texts: Is there a term for something like a "routing scheme"?

texts:
I would like to know if there is any common term to describe the routing of devices to conceptually understand the setup. E.g. something that explains how the devices are connected to each other on a "macro scale" like this:

And not a concise routing between the single components like this:

Hope you get the idea of what I mean. The upper one is more for people who aren't really involved so they get a rough understand on what is going on while the lower one targets people who need precise information to realize it.


texts: L298N Module 5V pin behavior on above 12V power supply

texts:
I have a lead acid battery that is barely above 12 volts (at 12.6) volts.
This seemed enough to trip the switch in behavior that changes the 5V pin from output to input in the L298N motor driver module.
The 5V pin which is input now, is necessary for board IC powering.
My big worry is whether the L298N will switch back to output when the voltage eventually drops.
Say I was using the aforementioned battery and the battery suddenly dropped, while at the same time, I was powering the L298N IC with a 5V external power supply. What will happen? I am very worried.
All batteries drop in voltage, so I assumed this would be the case and started looking for suitable regulators, which was fruitless.
I have an idea where I use 6V battery and a step-up converter, is it a more economical and portable choice?


texts: What kind of setup can take portable solar USB power & charge a AA battery charger that is usually designed to plug into a wall?

texts:
I have a portable solar panel that generates 21w of power, seen here: enter link description here . It has a USB connection wired into it that will accept a USB cord to charge small devices via USB. Separately, I have a Panasonic wall charger device (model BQ-CC75) seen here: enter link description here that will plug into a wall outlet to charge 1-4 rechargeable Ni-MH AA batteries. I would like to figure out if it is possible to find a way to connect the solar panel to the wall charger device in order to charge the AA batteries by solar. I know there are other devices out there that are designed to charge AAs from a solar panel, but I am wondering if the Panasonic can do it using an appropriate connection, and if yes, what that connection type might be.

So far, I have considered running this connection cable: enter link description here that would go from the solar USB connection to a cigarette-lighter plug, which is connected to a "wall outlet" style plug, such as this: enter link description here or this: enter link description here , and from there, plug in the Panasonic AA charger ... the hope is that this would charge 1-4 AA batteries successfully via solar.

Would this approach work?
If not, what would work?
If it works, but there is an easier way, what would that look like?

Thanks so much in advance for your advice, and thanks again for forgiving me for not knowing enough to figure out the good and bad of this idea on my own, and for not knowing the proper terms to describe things.


texts: Help me calculate the total voltage loss of circuit - DC

texts:
I am trying to anticipate the total voltage loss in my circuit.

Useful info:
I have a power supply (12V, 60A, 720w)
Wire used has a cross section of 2.5mm2
Each 6A represent the power consumption of an LED striplight of 5m
Each segment (shown with length in meters) will start and finish at the power supply.


texts:
I have my CAN configuration as shown in the below drawing(automotive application), the uC that I’m using has both the CAN controller and the physical layer transceiver built-in so I don’t need a transceiver outside the uC. I have a doubt regarding the common mode choke, I have read that the common mode choke will degrade the signal, below is the link to the question where this is stated  Are Common Mode Choke Coils needed on USB?
1)  I would like to understand how the signal degradation can be evaluated, I'm trying to select a common mode choke for CAN network with 500kbps baud rate and want to know things I have to consider while choosing a common mode choke. I understand that there will be some delay in the signal, but is there any way to theoretically calculate this time by simulation ? Or is testing required ?

2)  Below is the link to an application note by TI, titled “Common Mode Chokes in CAN Networks: Source of Unexpected Transients”, which states that “extremely high transient voltages that maybe generated by the inductive flyback during a short circuit of a CAN bus line to a dc voltage.” Should I test my circuit during short circuit conditions to see the voltage that the uC pins will see.
http://www.ti.com/lit/an/slla271/slla271.pdf

3)  Apart from EMC tests, is there any other electrical test that I can conduct to look at the effects that the common mode choke has on my circuitry.

4)  I also want to see the effect the capacitors C2, C3 and diode D1 has on the circuitry during ESD pulses. Is there a ESD pulse model available in LTspice and is it possible to simulate and see the results in Ltspice ? Is it feasible to do this ?


texts: What is the power specification for SATA?

texts:
We are designing a product which needs to provide data and power to an SSD connected using SATA. However, we cannot find a specification of the power requirements for a SATA connector. How much power should a power supply behind a SATA power connector provide at a minimum?

I have acccess to the SATA specification. However, we did not find a specification of a minimum power supply. It only mentions the 1.5 A rating of the individual pins. It seems to define how to deliver power, but not how much.

I found an answer on power connector pins and the wikipedia entry on SATA power connectors. However, it seems to me that the 1.5 A specified there is the minimum the connector should support. That is, the connector should not melt if I put 1.5 A per pin through it. I don't think it means the SATA device connected to it can expect 1.5 A per pin to be supplied.


texts: From where does the Common Mode 1.2V of LVDS comes from?

texts:
I am trying to understand the LVDS signalling.

But from where do we get the 1.2V common mode voltage?

Please help.
Thanks


texts: circuit in neither series or parallel (is wye delta transformation necessary?)

texts:
I have been trying out this one problem and I just want to know if I am on the right track, because it feels like a large amount of work based on such a simple circuit and it is getting quite messy. I have attached the picture of the problem along with my work thus far. This is not listed under the wye-delta transformation under the problems section, which is in fact after this section, so that is another reason for my uncertainty. I feel like I may be misunderstanding some concept. Anyway, I appreciate the help.
The work gets messy the end but basically at the very bottom it kind of goes clockwise.
EDIT: I feel like ground is indicated by the bottom node, such that 10 + 4 + R are all in series, but that still confuses me as to where to go from there.
EDIT 2: Using the method suggested: R = 20 = 60 || 14 + R = (60(14+R))/(60+14+R); R ends up being 16 ohms, which is correct. Are there any other methods for conceptual understanding?
http://puu.sh/ikefM/d13ac8777a.png


texts:
Finally built up the circuit below that I've been designing/toying with in LTSpice and its working OK but I'm wondering if an experienced eye might be able to quickly label what/why the oddities are in the signals I see on my oscilloscope.
I'm probably missing a crucial component/layout choice and I'm hoping its a typical beginner mistake I'm making!
Circuit

Input: 300Hz sine wave:

I notice that with the 300Hz input, when I increase the input level
the 'width' of the distorted parts widens - if that is a useful
observation for me to diagnose my issue?

Input: ActualMusic:

Actual Build

Let me know if I can/need to explain any of the spaghetti!


texts: PIN-diode lowest operation frequency limitations

texts:
I have a need to implement RF switch for HF circuit (~10 - 30 MHz) and I've been browsing options for that. Electromechanical switch would of course work, but I want to consider other possibilities too. Researching the options I have determined that PIN-diode based switch could be an option (need for low <2 pF OFF-state capacitance and low <5 Ohm ON-state resistance), but the low frequency sets some limitations for the diode.

I have been reading and in my understanding the width of the intrinsic layer is what limits the lowest usable frequency (based on this), but I do not understand how the minority charge carrier life time affects the PIN-diode characteristics. Seems like it's the main contributor for intermodulation distortion, but does it somehow relate to the I-layer width or are those independent of each other? Does it limit the lowest usable frequency? And is there some other parameter which does limit the frequency?

I can of course read from datasheets what's the frequency range for a specific PIN-diode, but I'd like to know what's limiting it.

EDIT
According to this the thickness of the intrinsic region determines the minority carrier lifetime. The wider the I-layer the more time the charge carriers have before they recombine. So, wider I-layer width leads directly to longer charge carrier lifetime. To use a PIN diode at relatively low frequency, a wide I-layer width is needed.

I did some measurements with BAR6403WE6327HTSA1 PIN diode (I-layer width of 50 micrometers), with a TEE compound switch topology, here's the used circuit:

It worked quite nicely as a switch, insertion loss of less than 0.7 dB and isolation of 60 dB with up to 30 dBm input power at 13.56 MHz.

Don't know if this edit was really necessary, but hopefully somebody can find the information useful.


texts: 433 MHz receiver consumes too much power

texts:
I bought one of this modules (link), with the SYN470 chip on it.
In the datasheet it's mentioned that in continuous mode with 433 MHz the current consumption is 3.9 mA which is a lot in my case.
But there's a polled operation mode which uses way less current and it also have a WAKEB pin, which I don't know what they are or how do I use them and there is no example of such circuit in the datasheet.
How can I configure this module to consume less power?


texts: Is the there an intended PCB layout for the MAX7219/MAX7221 I'm missing?

texts:
The ordering of the segment pins (14-17, 20-23) on the MAX7219/MAX7221 common-cathode LED display driver is unusual, to say the least:

The order of these pins is similar, but not identical, to the standard pin layout used by 4-position 7-segment displays, e.g.

It's similar enough that I feel like there should be some really neat way to lay it out on a PCB, but if there is, I can't seem to figure it out. Is there a particular board layout that this pin ordering is supposed to allow for? If so, what does it look like? (Or is this part intended for a different type of display?)


texts:
Is there any in built mechanism to simulate a charged capacitor in simulation software like Multisim or Proteus?

If not, is there any alternative method for simulation of partially charged Capacitors?


texts: PCB trace is 50 ohms, for reflection can we detect the discontinuity point?

texts:
all,

I've searched some information but still have questions.

If it is all impedance control from the whole trace (driver -- PCB trace - device input), does this mean no any reflection in the real world?
if it is a very longer line, sill no reflection but concern about line degrade rise/fall times due to the series resistance?
I used a system ATE, automatic test equipment) to drive a voltage to a IC's input, I can also do Smith when driving.
From the Smith chart I found there is a flat voltage at ~50% and looks like it is due to the signal reflection.
The flat voltage stays for ~16ns and per a general calculation the trace length is ~44 inches.  ---> 16 ns / 180 ps/inch (FR-4) x 1/2 (round trip)

The IC datasheet indicates the Generator is required for 50 ohms so I think the IC's input is 50 ohms impedance as well.

My question is, ATE driver, PCB traces and device's input are all 50 ohms impedance control but the reflection still occurs.

I was thinking the reflection is due to the device's input, I tried to short a 50 ohm resistor to device's input as a far-end parallel termination but no help.
Does this mean somewhere inside the ATE the impedance is not perfect 50 ohms?
I won't be able to find out the problem location as it is inside the system without some other equipment to support?

Much appreciate all your inputs.

Comment#1: added the shmoo chart

It is the shmoo result from ATE for ATE driver.


texts: Delay between steps, given speed in mm/min [stepper motor]

texts:
I'm building a device that have to move in orders of thousandths of mm per minute. I've got suitable stepper motor and driver, it is working correctly but I'm unable to figure out the formula needed to calculate delay between steps to get to proper speed. I have Nextion display connected to an Arduino, that sends the speed (in mm/min), but I just can't figure out how to calculate the delays. I've measured following:

1 step = 0.000004767mm
Driver is set to 1/6400 resolution

I have two end switches that will trigger interrupt once it reached end/start, so no worries about length. I also need the delay to be in us (microseconds). So far I've tried (0.000004676 / speed)x60000000. It seems to be OK in 0.0x range but when I go lower, it just doesn't work properly.
Thanks for replies.

EDIT: So the formula seems correct, but I don't get why 0.01mm/min is pretty much perfectly accurate and 0.009mm/min is done in 28s.


texts: Finding Rise time and Fall time with Slew Rate Specification

texts:
I am using this QSPI Flash Memory IC

I'm operating the QSPI clock at 48MHz. I am probing the Clock and Data signals in my scope.

On Table 54 which is on Page 128, we have Rise time and fall time specifications. But the specification is given in terms of slew rate instead of seconds. How to convert it into seconds format.

I tried doing the below approach :

Considering figure 12.4.1 in page 129, rise time and fall time are given with respect to Vil max and Vih min which is 0.99V and 2.31V respectively.

So, 2.31V-0.99V = 1.32V.

But rise time is given as 0.1V/ns.

So, if 0.1V is for 1 ns, then 1.32V should have a rise time of 13.2ns?

I think this is wrong approach. Can someone help me with this on how to find the rise time in terms of seconds instead of slew rate?

Waveforms (Please check the Y-cursor is kept as per the Vil max and Vih min as per the table)


texts:
After learning that some devices can be charged up wirelessly through inductive means (which https://powerbyproxi.com/wireless-charging/ illustrates), I want to try to invent a simple one myself, but I have a few questions.

For the charger circuit, could I get away with creating a simple one-transistor transmitter? If so, what frequency will I need to set it at and why? and will I always get better results if I use high-value inductors?
I assume for the receiver circuit (circuit to be charged) that the frequency must match, but should the inductance also match or be different?
How is it possible that such technology works if a dead battery powers the receiver? does one have to solely rely on crystal radio technology and have the transmitter almost sandwiched next to the receiver?


texts: My Atmega328 seems to be overkill, what should I use instead?

texts:
I'm using an Atmega328 chip with the arduino bootloader in a very small circuit. The sketch simply plays a tune using the tone() function to play a melody through a piezo speaker on a single pin.

Clearly using this chip is overkill, but the programming environment is so simple for arduino, and easy for me to use.
Can I use a Attiny with the arduino bootloader or something similar? What would be the right way to miniaturise this project, so I don't feel like I'm wasting components. If it's a case of using a different chip/environment entirely, where do I start?

(for clarity, I am not using an arduino in the circuit, just the Atmega328 chip)


texts:
I'm having a problem with my multimeter. It has a opto-isolated connection for external instruments which uses a LED on the multimeter side. The LED is normally placed inside of a plastic case which mates with a cable. In normal operation, the LED is held by friction inside the plastic case, but in my case the case turned loose and the LED keeps falling inside the multimeter body.

My first idea was to use some cyanoacrylate glue to fix the diode to the plastic part, but I'm concerned if CA glue would be safe to use on a diode.

So what type of glue should I use to fix the LED to the plastic part?


texts:
thank you for taking your time to read, im hoping someone can help me out!

I am looking to drive a piezo transducer at its resonant frequency(20khz) to generate sound waves. I am doing an application similar to sonar technology.

I was looking into how to drive the transducer and I thought i would have to generate and feed it sin waves with its resonant frequency. I have access to an Arduino DUE, i was looking into how to do so and it seemed a bit complicated.

I was curious if anyone had any experience driving a piezo and if it would be possible to do so with just square waves. Or if they have experience generating sine waves of any frequency within an arduino please let me know!
Thank you all for your time and help!


texts: Which component to use for a few GBytes of memory available for several years?

texts:
I am working on a project which is supposed to be built in small quantities (less than 50 units/year), but will probably be sold for 10 or 15 years. I am at the stage where I look at the non volatile memory, and we plan to use something like 16-32GB.

In the past, we used SD Cards, but we faced some reliability problems with the holder, as the SD Card sometimes came out of the socket. We also found that a particular card is likely to become obsolete after a few years, so we always have to check that alternative parts would work the same.

I had a look into the following technologies, and I found some inconvenients:

SD Card: need for a mechanical part to hold it, obsolete after a few years
Flash ICs: complex to interface
eMMC: difficult to source
EEPROM: small capacity (<100MB)

Did I miss something? Is there any other reliable solution to replace an SD Card on a design?

Edit: the application would continuously write data (a few kB per second), but during several hours or sometimes days. The retention time is not a big deal, as long as it is reasonable.


texts: How to find the total phase of this transfer function

texts: I'd always understood that in a transfer function, every pole contributes -90 degrees in phase and every zero contributes +90 degrees in phase. Based on this assumption, I would expect the following transfer function to settle at a total phase of 6*90 - 90 = 450 degrees. However, wolfram alpha shows the phase at 360 degrees. Do you know where I've gone wrong with my logic?


texts: Track movements of 500 objects in one single room

texts: Let's say we have a room with a size of approximately 300 sqm. In this room we have 500 objects that are tagged with beacons having accelerometers. Is there any way to process the produced data of these beacons with a kind of hub? Thought about Bluetooth Low Energy but that only supports a few connections at the same time. Also thought about Wifi but I don't know if a hub would be able to handle 500 Wifi connections + battery life of the beacons would be much better with Bluetooth I guess. Any ideas very welcome.


texts: Why exactly is it discouraged to gap the ground plane?

texts:
From time to time I hear (and read) that it is not good to make separate Gnd planes for digital and analog circuit parts. It's all summarized in this rule of thumb: "Don't split the Gnd plane, don't make gaps in it." Usually this comes without clear explanation.

The closest I got to an explanation is this link: http://www.hottconsultants.com/techtips/tips-slots.html .
The author points out that return currents will bend around the gap, such that the surface areas of the currents get large (borders of that surface area are defined by 'departing' and 'returning' current):

The return currents of the different signals are squeezed together at the corners of the gap, leading to cross-talk. The larger surface area of the current loops will emit and pick up EMC.

So far, so good. I do understand that no signals should be routed over such gap. Presuming you keep that rule in mind, would it still be bad to make gaps in the Gnd plane (eg. making a split between analog and digital circuit parts)?


texts: I have a circuit that has the emitter side of a NPN tied to the emitter side of PNP. I need to find the output voltage on the emitter. Base voltage is a sine wave. Can someone help me understand what this kind of configuration is used for? And how should I go about to calculate the power dissipated by the resistor?


texts: Problem in connecting to a server waiting for a TCP request using ESP8266

texts:
I'm using ESP8266 for connecting to a appspot-preview.l.google.com server which listens for TCP request and answers back a number (it's for training purposes).

Problem is from my location, I can't connect to the website properly even from my browser. Firefox and Chrome take about ~40 seconds to render the page (which has a list of people who issued TCP request to that server).

Now, my specific problem lies in ("AT+CIPSTART=\"TCP\",\"%s\",80\r\n", IPaddress). ESP8266 quickly replies a "ERROR" after trying to establish a TCP connection to that IP.

1- I want ESP8266 to wait and try connecting to the website in the same way my browser does (after ~40 seconds). How can I do this?

2- There is a "TCP keep alive" switch in the AT+CIPSTART command from official "ESP8266 AT Instruction Set":

Is this option relevant to my problem? Why is there a comma inside the brackets?

Thanks


texts:
Please I have some couple of 3.6v 3Ah cylindrical li-ion battery, but since I bought them, charging it became a huge problem. I first connected a single one to a 2A infinix phone charger (made in china. According to the ratings, it capable of adjusting output current and voltage to load)thinking that if it's capable of charging a 4Ah infinix phone battery then a 3Ah shouldn't be a problem.
Until I connected the battery directly to the charger output, after some time, i measured the output voltage of both the battery and the charger, the battery was not charging and the charger decreased it output voltage from 5v to 2v and was also giving me an unusual jolt in my finger. I concluded that the charger has damage. I tried it again with a similar charger, but this time a TECNO phone charger, but the same result.
I then found another SMPS charger 12v, 1.2A. In my desperation, I ignorantly implemented a '7805' regulator ic to drop the voltage to 5v(since using a smps to regulate a smps sounds absurd). When I connected the battery, I measured the charging current, and I was so surpries to see 2A.From a 1.2A(short circuit current) SMPS.
So please where did I went wrong and how can I charge my batteries before it damage.


texts: Can I solder a RG316 coax directly to a PCB instead of using the intended SMA connectors?

texts:
I have a length of RG-316 single shield 50Ω coaxial cable carrying a 5.8 GHz signal that I need to connect to a PCB. While cheap relative to most coaxial connectors, SMA connectors are still quite expensive, take up space and are relatively heavy. The PCB was designed for side mount SMA connectors.

Could I replace the original SMA connectors with direct soldering joints like this, without causing a large impedance mismatch?

How could I improve the RF performance of the connection?
The mechanical strength of the joint is poor, and the teflon insulator does not bond well with common adhesives. Can I protect the joint with nonconductive adhesives (epoxy, hot glue) without significantly affecting its RF performance? What would be the best way to secure it mechanically?


texts: How to add specific voltage offset to the "balanced phase splitter" op amp circuit?

texts: I use the basic 2 opamps "balanced phase splitter" circuit to get 2 separate square wave outputs (0 and 180 phase). The input is 12Vpp but I need both outputs to be offset by -6V. So instead of 6/-6V outputs, I need 0-12V. I did solve this problem with 2 offset circuits but maybe there is a more straightforward way to do it? My intuition tells me to offset the input BEFORE inverting. Thanks.


texts: Why is this resistor connected in such way?

texts:
Why is the R2 resistor connected to bias instead of ground? As far as I know, only one of the op-amp's inputs has to be biased, so why such configuration? Also, how does this affect the gain?

Edit #1: Vcc here is 5V.

Edit #2:

R2 connected as shown above:

R2 in series with a 10uF cap connected to ground:


texts: Using Buck converter and LDO from the same power source

texts:
I'm designing a device with several ICs and they require so many different input supply voltages.
18V, 12V, 3.3V, 1.8V 1.3V.

18V will probably use around 80W out of 100W(20V, 5A) main supply budget and 3.3V~1.3V will probably use around 1A~2A.

So, I was thinking of using a couple of LDOs in parallel to relieve thermal issues for the 18V source and use a buck converter to make 20V into 5V and use LDO to supply 3.3V, 1.8V, and 1.3V.

But I'm not so sure if it's ok to directly connect buck converter and the LDO to a single 20V,5A power supply rail.
My concern is that during operation, LDO and buck Vout could be unstable when either one pulls currents hard.

I'm thinking Al caps with high capacitance could help, but is this enough to maintain stability? Are there good guidelines for using linear regulators and switching converters?


texts: How can I use a single port of PIC18F4550 as both input and output

texts:
I'm trying to use port B of PIC18F4550 as both inputs and outputs. What I need to do is to connect a 7-segment-display and also connect 4 push buttons to the same port, this means that I need to use the same port as inputs and outputs and it's supossed that when the I introduce the number from 0 to 15 (F) then the port B must recognize this inputs and then start to work as outputs and send a '1' to the respective pines of the 7-segment-display in order to see corresponding number in decimal.
My code is the following one and I'm using PIC C Compiler:
#include<18F4550.h>
#fuses XT, NOPROTECT, NOWDT, NOLVP, PUT
#use delay(clock = 4M, crystal = 8M)
#use fast_io(b)

int DSPIN;
int DSPOUT = 0;
int DSPVALOR[16] = {
                 0b00111111,//0
                 0b00000110,//1
                 0b01011011,//2
                 0b01001111,//3
                 0b01100110,//4
                 0b01101101,//5
                 0b01111101,//6
                 0b01000111,//7
                 0b01111111,//8
                 0b01100111,//9
                 0b01110111,//A
                 0b01111100,//b
                 0b00111001,//C
                 0b01011110,//d
                 0b01111001,//E
                 0b01110001 //F
             };
void main(){

 SET_TRIS_B(0b00001111);
 DSPIN = input_b();

 while(true){

  if(DSPIN == 0b00000000){
     DSPOUT = 0;
  }
  else if(DSPIN == 0b00000001){
     DSPOUT = 1;
  }
  else if(DSPIN == 0b00000010){
     DSPOUT = 2;
  }
  else if(DSPIN == 0b00000011){
     DSPOUT = 3;
  }
  else if(DSPIN == 0b00000100){
     DSPOUT = 4;
  }
  else if(DSPIN == 0b00000101){
     DSPOUT = 5;
  }
  else if(DSPIN == 0b00000110){
     DSPOUT = 6;
  }
  else if(DSPIN == 0b00000111){
     DSPOUT = 7;
  }
  else if(DSPIN == 0b00001000){
     DSPOUT = 8;
  }
  else if(DSPIN == 0b00001001){
     DSPOUT = 9;
  }
  else if(DSPIN == 0b00001010){
     DSPOUT = 10;
  }
  else if(DSPIN == 0b00001011){
     DSPOUT = 11;
  }
  else if(DSPIN == 0b00001100){
     DSPOUT = 12;
  }
  else if(DSPIN == 0b00001101){
     DSPOUT = 13;
  }
  else if(DSPIN == 0b00001110){
     DSPOUT = 14;
  }
  else if(DSPIN == 0b00001111){
     DSPOUT = 15;
  }
  else{
     DSPOUT = 0;
  }

  delay_ms(1000);
  SET_TRIS_B(0b11111111);

  switch(DSPOUT){

     case 0:
        output_b(DSPVALOR[0]);
     break;

     case 1:
        output_b(DSPVALOR[1]);
     break;

     case 2:
        output_b(DSPVALOR[2]);
     break;

     case 3:
        output_b(DSPVALOR[3]);
     break;

     case 4:
        output_b(DSPVALOR[4]);
     break;

     case 5:
        output_b(DSPVALOR[5]);
     break;

     case 6:
        output_b(DSPVALOR[6]);
     break;

     case 7:
        output_b(DSPVALOR[7]);
     break;

     case 8:
        output_b(DSPVALOR[8]);
     break;

     case 9:
        output_b(DSPVALOR[9]);
     break;

     case 10:
        output_b(DSPVALOR[10]);
     break;

     case 11:
        output_b(DSPVALOR[11]);
     break;

     case 12:
        output_b(DSPVALOR[12]);
     break;

     case 13:
        output_b(DSPVALOR[13]);
     break;

     case 14:
        output_b(DSPVALOR[14]);
     break;

     case 15:
        output_b(DSPVALOR[15]);
     break;

     Default:
        output_b(DSPVALOR[0]);
     break;
  }
     delay_ms(1000);
  }
}


texts: What is the measurement grid in the context of strain gauge?

texts:
The sensor I am investigating is the 1-LM11 by Omega.

I am looking at the specification at there are two metrics which confuse me, the measurement grid A is 1.5mm while measurement grid B is 2.5mm. This really doesn't make much sense intuitively while looking at the picture

Dimensions C and D seem slightly more likely with them being 9 and 4.4 respectively. Could someone clarify what the market grid is exactly?


texts: What does Unvarnished Transmission Mode Mean?

texts:
I am using an ESP8266 Wifi Module and I have come across a command "AT+CIPMODE=X" which basically sets the mode of the wifi to normal mode if X=0 and Unvarnished Transmission mode when X = 1. I have googled the term and cannot come up with what it means. Please tell me what this term means and what is the difference between the two modes. For some reference:-
https://github.com/espressif/ESP8266_AT/wiki/CIPMODE


texts: How do you initialize the target cpu using the usbWiggler API?

texts:
I'm trying to use usbWiggler to communicate with a board that has 4 ICs.

Through the usbWiggler API I have been trying to write and read from the board. However the CPU on the board is not one of the recognized CPUs and although the API giving the option to name it "UNKNOWN" the initialization of the API (through MacraigorApi_InitializeTarget()) fails with "Invalid Parameter" error.

Dose anyone know how to fix this?
I tried contacting their support but they never reply.

Edit 01

The CPU is Motorola 68hc11.


texts: Why do I need to convert impedance to admittance in this problem

texts:
1 = 18 A, 2 = 15 A ,  = 30 A and R2 = 4 Ω.
determine 1 and L .

This is the picture of the circuit:

And this my solution all the way to the point where I have uncertainties:

Now I can solve this in two ways:

I can solve it without converting impedance to admittance (gives the wrong answer)
Or I can solve it with converting impedance to admittance (gives the correct answer)

My question is why will I get the wrong answer when not converting impedance into admittance, it seems mathematically correct, but it is the wrong solution, can someone explain?


texts:
My question surrounds a simple scenario.

I have a 12V DC power source connected to 2.2kΩ/10kΩ/22kΩ resistors in series.

For an assignment, I have theoretically calculated Voltage drops across all resistors, as well as respective current draw for each resistor.  I am aware that the current entering a resistor should be the same as coming out.

I have simulated the circuit in Circuit Wizard (Uni assigned software package), and found that after each resistor the current drops fractionally.
For example - The Total Circuit resistance is detailed as 350.97microA.
Then:
Through 2.2kΩ - drops to 350.92MicroA
Through 10kΩ - drops to 350.88MicroA
Through 22kΩ - drops to 350.86MicroA

Obviously - the difference between my calculated values and the simulated values is only around 0.02%.. However I wouldnt expect the current to change.

When I increase voltage on the power supply - to signifcantly larger values (50V+) - current measurements remain as expected.

Am I right in presuming that this is due to the impedance thats been calibrated into this digital Ammeter?
Im drawing conclusions and this is the only thing I can think of.


texts: The value of the TCC counter on an ATSAM controller always reads as zero

texts:
I use an ATSAMD21 to generate a custom signal with the help of a PWM generator.

Basically, I set up TCC0 as a PWM generator, and use its overflow interrupt to set up the CC registers for the next pulse. It all works fine, the signal looks as it should look like. However, as it is important for the interrupt to occur before the shortest possible polarity change in my signal, I wanted to check the interrupt latency, to detect a possible failure case. That should be as simple as checking the COUNT register at the beginning of the interrupt, shouldn't it?

However, the COUNT register always reads as zero.

It doesn't matter whether I use REG_TCC0_COUNT or TCC0->COUNT.bit.COUNT, it always reads as 0. I can be sure that the actual value of the counter is not zero, because the timer is set to a very fast clock generator, and on the oscilloscope I can see that the typical interrupt latency is where the counter should already be around 100.

Interestingly, I can write to the COUNT register. If I do so, I can verify that the next pulse is shortened by the respective amount. And after the write, if I read it back, I read the value I just wrote.

As the same processor is used in the Arduino Zero, this issue was already asked on the Arduino forums a few years ago, but there is still no answer:

https://forum.arduino.cc/index.php?topic=341655.0
http://www.arduino.org/forums/zero/reading-tcc0-tcc1-and-tcc2-count-register-251

One of the proposed solutions was to wait for the SYNCBUSY to be cleared, but it didn't work, neither for the poster on the Arduino forum, nor for me.


texts: Can I approximate an "intelligent charger" just by charging one battery at a time?

texts:
There seem to be two main classes of domestic battery chargers - "intelligent" chargers which charge batteries individually, until some measurement(s) of the batteries determine that charging should cease, and dumb chargers which charge all batteries at the same rate.

These terms are marketing-speak and have no real formal definition. However, is it possible to approximate the functionality of an intelligent charger, simply by charging one battery at a time?

I am mostly interested in domestic batteries with NiMH chemistry.


texts:
I am trying to draw a footprint of some component which has 8 pins but in the document they shared for outline dimensions and footprint:
Outline dimensions
Footprint

There is some rectangle in the middle of the footprint. That has sx and sy dimensions. That part confused my mind. Is it silkscreen?


texts: Clipped input sine with 1N4148 signal diode

texts:
in my electronics lab at university we were studying diodes and I stumbled upon a behaviour that I cannot understand nor explain (I'm I physics undergrad, not and EE).

The circuit we were analysing is a simple single diode rectifier (a 1N4148 signal diode) with a 100 ohm load in parallel with a 330uF electrolytic cap and a 50Hz input sine wave. I noticed that the input signal was clipped. To eliminate the doubt that the problem was to be caused by something other than the circuit (signal generator, oscilloscope etc) I simulated it in LTSpice and got the same result, whitch is the one in the image.

Why is the circuit doing this? If I measure directly the input signal shouldn't I see a 50Hz sine wave?

If it helps the circuit is this:


texts: How to wire a single phase, 3 wire motor?

texts:
So i bought a motor off of kijiji, it was an old furnace motor. I am trying to build a flat lapidary machine and use this motor to power it. However, there is no wiring diagram on the motor anywhere and i cannot figure out which wires connect to what. Everything i find online says they have 3 wires plus a white ground motor, however this motor only has a blue, red and black wire coming out of it. I think that the black wire is the ground wire. i literally just want to connect it to a switch & a power source which i think should be really simple... thank you for any advice/wisdom you may have to offer
motor label


texts:
I have been working on designing a PCB for a Z80 computer that I plan to sell a few times for interested people. The Z80 will work at a maximum of 8 MHz and has parallel lines going to a system controller and an SRAM chip.
The board is 170x110 mm in size. Currently I use 16 mil traces for the parallel bus and address lines and a spacing of 25 mil between them. I wonder whether this is enough for 5V data @ max. 8 MHz. Do I need termination resistors?

What do you think?


texts: Use of large motor capacitors to stop voltage drops from because of high electrical draws

texts:
Good Day Everyone.
Please bear with me and have patience. I have a feeling I will quickly be considered the village idiot here.
I have trouble with voltage fluctuation especially with high demand draws such as air compressors and welders. What I want to do is wire large motor starting capacitors in line to eliminate this. I did find a little information about this but they seemed to have a pretty sketchy grasp on this.
I'm working with single phase 220 volt any information would be appreciated.


texts: Is there a way that you can get a Portable/Online  Arduino IDE?

texts: I am just starting out with the Arduino, and I want to develop and create sketches at my school.  The only problem is that the school's computer doesn't allow any application to run if app tries to create a folder on its hard-drive.  Are there any ways to make the standard  IDE portable, or is there another portable option?


texts: Why does the astable mode in 555 timer require two resistors, whereas monostable works with just one resistor ? The cap gets charged through R1 and R2 and gets discharged through R2. But in monostable it gets discharged without any resistor.


texts:
I have four LEDS (Red,Green,Blue,Yellow) and want to use charlieplexing to light them up.
I'll use an Attiny13V which needs 1.8 to 5.5V. I think one CR2032 with 3V will be suffice for the µC.
The forward voltages and current of the LEDs are:

        Min   Typ   Max | Max (mA)
Red:    1.7   2.1   2.8 | 20
Green:  1.7   2.1   2.8 | 20
Yellow: 1.7   2.1   2.8 | 20
Blue:   2.9   3.3   3.6 | 10-20

Will I'm able to light the LEDs with the CR2032 and how can I find the right resistor values?


texts: Arduino Razor IMU with Serial.write(id, 2): Can't have 2 parameters

texts:
I downloaded the Razor IMU source code last night from Razor AHRS. This code uses exactly the sensors I need and would solve the problem I have currently (I hope). The only problem is that on line 535 in "Razor AHRS v1.4.1\Arduino\Razor_AHRS\Razor_AHRS.pde" in the above linked zip file they have:

Serial.write(id, 2);

When I Verify, compilation fails at this line with the following error:

no matching function for call to 'Serial_::write(byte [2],int)'

I downloaded and installed Arduino 1.0.2 on a new pc and installed the drivers to Arduino Pro Micro 16MHz/5V.

I checked the arduino documentation on Serial.write and it seems to be a valid command.

On a previous machine I had Ardiono 1.0 installed where I initially had this problem. I then installed Arduino 1.0.2 on that machine and it worked. Now, on this new machine I installed 1.0.2 only and it doesn't work.

What am I doing wrong?


texts: How to constantly power an LED circuit normally controlled with a momentary switch?

texts:
So background: I have a novelty light up Disney Fantasia Sorcerer’s hat that I would like to use a a Christmas tree topper. The hat has an LED circuit built in with pulsating lights in various colors that is powered by 3 AAA batteries (4.5V DC). At the base of the hat is a normally open momentary switch button, one of those “Press Here” things. When you press the button the little LED show turns on with a couple colored LEDs pulsating on and off and a couple multicolor LEDs cycling colors and it lasts a little more than 30 seconds with just a single press of the button.
Since it is at the top of the tree I would like to be able to swap the battery pack for an AC adapter that I can plug into the end of the light string on the tree on a timer, so whenever the lights are on, the hat lights up. The problem I’m having is bypassing the little “Press Here” button to trick it into staying lit up whenever there is power. I tried cutting the switch off and twisting the wires together to provide a constant closed circuit but when I switch the battery pack on, nothing happens. When I take the two wires from the switch and briefly tap them together, the hat lights up. If I sit here and periodically tap the wires together, simulating the press of the button, I can get the hat to stay on indefinitely. But if I leave the wires in constant contact, the lights stay on for their 30 second show then turn off.
In the picture, I’m holding the two white wires from the little circuit board twisted together as well as the switch I cut off. The black and red wire from the top left of the board going out of the picture is the 4.5VDC from the battery pack.


texts: Designing PCB with AC Live and Neutral on two layers

texts:
I'm designing a smart socket that will route 240V AC Live and Neutral to a voltage regulator and also to a relay that will control the current flow. Due to the limited space, it will be easier to route the live wire on the top layer and neutral on the bottom layer as shown in the diagram below where the red track is AC Live and blue is AC Neutral.

The PCB is two layers with a thickness of 1.6mm. Will there be any problem routing it this way? Will it create a voltage potential or capacitance of any type? Secondly, the relay can handle up to 5A, hence the tracks should be able to handle 5A too. Based on an online PCB trace calculator, the trace must have a width of 2.77mm which is quite hard to fit in the limited space. If I leave the traces to be exposed copper, can I then reduce the trace width?

[EDITED]
This is the alternate PCB layout where it is on a single layer but as you can see it increases the track length quite significantly.


texts: I'm using LM2576 regulator for having variable DC voltage. The output of the regulator specified in the datasheet is 1.23v to 37v. I need voltage to vary between 0v to 10v. I found that using a charge pump circuit a negative voltage of -1.23v can be produced and this compensates for 1.23v. Is there any other method?


texts: I've been using different power supplies for 6 years. But, I'm unable to understand how we make ground in a Power supply? Or from where does this ground come? Or from where does this reference ground come? Is it reference to earth or what?


texts: Drawing a bitmap using 2D DMA on STMF32F4

texts:
I'm trying to draw a bitmap using 2D DMA, so I have the address of the destination which is the front buffer, and then I read a line from the bitmap, blit it using the 2D DMA.. I get scanlines, and garbage image. Not sure where is the problem

void BSP_LCD_DrawBitmap(uint16_t layer,uint32_t X, uint32_t Y, const uint16_t *pBmp)
{
  uint32_t index = 0, width = 0, height = 0, bitpixel = 0;

  /* Get bitmap data address offset */
  index = 0;

  /* Read bitmap width */
  width = 240;

  /* Read bitmap height */
  height = 320;

    uint16_t address = LtdcHandler.LayerCfg[ActiveLayer].FBStartAdress ;

    for (int i = 0 ; i < height ; i++)
    {
       ConvertLineToRGB565( (uint16_t *)pBmp, (uint16_t *) address ,  width , CM_RGB565) ;
         address += (width*2) ;
         pBmp += (width*2) ;
    }
}

static void ConvertLineToRGB565(void * pSrc, void * pDst, uint32_t xSize, uint32_t ColorMode)
{
  /* Configure the DMA2D Mode, Color Mode and output offset */
  Dma2dHandler.Init.Mode         = DMA2D_M2M_PFC;
  Dma2dHandler.Init.ColorMode    = DMA2D_RGB565;
  Dma2dHandler.Init.OutputOffset = 0;

  /* Foreground Configuration */
  Dma2dHandler.LayerCfg[1].AlphaMode = DMA2D_NO_MODIF_ALPHA;
  Dma2dHandler.LayerCfg[1].InputAlpha = 0xFF;
  Dma2dHandler.LayerCfg[1].InputColorMode = ColorMode;
  Dma2dHandler.LayerCfg[1].InputOffset = 0;

  Dma2dHandler.Instance = DMA2D;

  /* DMA2D Initialization */
  if(HAL_DMA2D_Init(&Dma2dHandler) == HAL_OK)
  {
    if(HAL_DMA2D_ConfigLayer(&Dma2dHandler, 1) == HAL_OK)
    {
      if (HAL_DMA2D_Start(&Dma2dHandler, (uint16_t)pSrc, (uint16_t)pDst, xSize, 1) == HAL_OK)
      {
        /* Polling For DMA transfer */
        HAL_DMA2D_PollForTransfer(&Dma2dHandler, 10);
      }
    }
  }
}


texts: I2C protocol in mbed online IDE using two STM32F429ZI board

texts:
I am trying to send message from slave(STM2) to my master(STM1).but it doesnot show anything on my serial terminal .just i want to send and receive data in
between master and slave

my master code:

#include "mbed.h"

I2C i2c(PB_9,PB_6);
Serial pc(USBTX, USBRX);

int main() {
    const int addr = 0xA0;
    int a,b;
    char buff[10]; const char data[]="message master";

    i2c.frequency(10000);

    while(1) {
    /* i2c.start();
        a=i2c.read(addr, buff,10,1);
        wait(1);
        pc.printf("Read %d", a);
        i2c.stop();
        pc.printf("MASTER READ: %s \n\r", buff);*/
        i2c.start();
        b=i2c.write( addr, data, strlen(data)+1);
        wait(0.07);
        i2c.stop();
        pc.printf("Write %d\n\r", b);
        for(int i = 0; i < 10; i++) buff[i] = 0;

        }
 }

My slave code:

#include "mbed.h"

I2C i2c(PB_9,PB_6);
Serial pc(USBTX, USBRX);

int main() {

    const char test[]= "message slave";
    char buf[10];
    int i, b;

    i2c.frequency(10000);
    slave.address(0x01);

    while(1) {

        i = slave.receive();
        wait(0.75);

        switch (i) {

            case I2CSlave::ReadAddressed:

                slave.stop();
                b=slave.write(test, strlen(test) + 1);
                wait(0.75);

                pc.printf("Return Slave %d", b);// only to check return value

                break;
            case I2CSlave::WriteGeneral:

                slave.stop();
                slave.read(buf, 10);
                wait(0.75);
                pc.printf("SLAVE Read G: %s\n\r", buf);
                break;
            case I2CSlave::WriteAddressed:

                slave.stop();
                slave.read(buf, 10);
                wait(0.75);
                pc.printf("SLAVE Read A: %s\n\r", buf);
                break;
        }
        for(int i = 0; i < 10; i++) buf[i] = 0;

    }
}


texts: Options for semi-permanent memory in a low-energy setting

texts:
(Hopefully this will be broad enough to be on-topic.)

I'm looking for options to store several megabytes of data over the period of a few weeks in a coin-cell powered application. The data doesn't need to survive a power outage (dead battery, etc.), but I do expect to perform several hundred reads and writes over the life of a single battery.

What technology type would be the most power efficient? The flash options I'm looking at (such as the m24px80) have fairly substantial current draw on write (15mA @ 3V). What other options are there?


texts: I am trying to read an analog input using a raspberry pi zero W, but all of the GPIO are digital. Can you guys maybe suggest on how to get around this or maybe point me to forums or guide regarding the matter? I am also a beginner in using raspberry pi. all response would be appreciated


texts:
How does one find what base current to use in simulating a phototransistor?
I wish to use LTspice to simulating a phototransistor (LPT80), so I downloaded the model but I have not found information on the base current to use?
And how do I relate the base current to daylight?
Is there a better way to know than trial and error? eg -1mA does turn it on and 0A does turn it off.
The model (in "OSRAM Phototransistors II.lib") can be found here https://www.osram.com/apps/downloadcenter/os/?path=%2Fos-files%2FElectrical+Simulation%2FIR%2FSilicon+Photodetectors%2FPSpice+Libraries%2F
The datasheet for LPT80A is:https://www.osram.com/ecat/Radial%20Sidelooker%20LPT%2080%20A/com/en/class_pim_web_catalog_103489/global/prd_pim_device_2219650/#tools


texts:
I have a solenoid with unknown specifications. I have contacted the manufacturer, but they are reluctant when it comes to sharing information about this product.

The problem

I need to trigger a solenoid from my Raspberry Pi. I want to do this by providing power from a DC power supply that came with the original product (The product is not the solenoid). I am using a Raspberry Pi as the control unit and a relay (http://www.songle.com/en/pdf/20084141716341001.pdf).

We also think that our solenoid is similar to this one: http://www.testco-inc.com/ledex-solenoids/B22-254-M-36

What we know

Before starting this project I have measured the Voltage and Current from the original control unit that shipped with the product. When we want to trigger the solenoid, the existing control unit sends 0,355 Amps at 22,1 Volts through the circuit.

I did make my own power cable using the DC power adapter and that provides 0,375 Amps at 24,1 Volts.

But the solenoid does not trigger

Does anyone have any ideas that I might try out?

Other questions

Could the voltage provided be too high?
Does a solenoid requires more current to trigger, and then less to "keep holding?


texts: What are suitable transformer specs to use with LM1893 PLC modem?

texts:
I'm trying to learn about PLC (I know the risks), so I want to start with the simplest circuit specified in the LM1893 datasheet to use on 220v AC powerline.
The transformer there doesn't have any specs, how can I choose a suitable transformer for that purpose?


texts: 230VAC line voltage sensing using MCU pin

texts:
I Am designing a circuit to detect the presence of AC line voltage.It is basically to detect the switch On/OFF for a load.
Here is the circuit.

Here Input resistor ladder to step down the voltage. Varistor added to get it away from surge (Fuse included). zener to protect the opto. Opto is darlington with transistor to reduce the opto input current and therefor the input resistor losses.

Since this going to commercial product i would like to gather some info on reliability and surge protection.

1) Is this circuit good enough to handle potential surges/Back emf from inductive loads.
2) Is there any better/cost effective alternatives.
4) I am using 8 in my board to detect 8 channels all are powered from same AC source. Is there a way to consolidate these and reduce overall cost?

Thanks in advance!


texts:
I have a SBC (single board computer) that feeds power and i2s signals to a DAC.

The problem is that SBC generates a lot of noise and I am thinking to add a "DC to DC isolated converter" + LDO and use some galvanic isolator on the i2c lines.

My question is: will this help substantially as far as removing noise from DAC analog output  ?


texts: Boundary scan developer and testing tools

texts: I have to choose a tool for production testing of fairly dense PCB's with 4+ FPGAs 10+ DSPs, ethernet controllers and PCI controllers.. Does anyone have any experience with any of the tools available from GOEPEL, XJTAG, Jtag-technologies or if anyone know of any good open source alternatives? That is both the BS hardware controller and/or software..


texts: Mosfet type to drive a 100A DC motor using pwm

texts:
I have a bunch of custom made DC motors. They are supposed to work in a range between 80Vdc and 120Vdc. Nominal power is around 800-1000W (they're custom made for a custom application, so specs are somewhat foggy...).

Now they start just by switching a clean contact, I'm requested to give them a ramp up and be able to choose the rotating speed (not the sense of rotation).

I'm planning to drive the motors using PWM and some industrial microcontroller or PLC (although I'll be prototyping using an Arduino), but I'm having the worst time finding a suitable MOSFET to drive such a bulky motor. Any recommendation on that matter is greatly appreciated.

UPDATE: So, I ended up using an IRFB4115PbF mosfet, and it works great.


texts: Why 2 output currents in LM358 datasheet

texts: When I was looking through the datasheet of the LM358 op-amp, I have seen that they have given two columns in page-4 and page-5 with same parameter name "output current". The first column in page-4 has a  set of source and sink values ans the column in page-5 has a set of source and sink values. So why there are two seperate columns for same parameter with different values. The test conditions are also same in the two columns except for the column in page-4 where the Ta value of 25°C is given and the second column does not have that value. Is there any other reason why there are two separate columns with different output current or else they are only for denoting the current range at different temperatures.


texts: How do I physically work with a hobby motor?

texts:
How do I incorporate a hobby-style motor into a project, physically.  How do I mount it and connect a wheel to it?  (Assume that I have a working H-bridge or even switches, and am not concerned about how to use the motor electrically, just physically.)

I've purchased small, hobby style motors at various times.  Typically, they run on 1.5 V to 12 V, and many of them have no built-in gearing (and thus spin really fast with very low torque).  How do I connect a wheel to it, or a gear or pully?

Next, most motors of this sort are round.  Round!  If it was flat on one side, I could glue it down.  It looks like they are designed to be screwed into something at the front or back, but I don't know how I'd make a surface to mate to it nor make marks to drill holes through it precisely enough.

What have you found works for when you want to make an electronics project move around on its own?


texts: What are the limitations of "fake" balanced audio cables?

texts:
I have an AV receiver providing amplified outputs and preamp outputs.
The pre-amp outputs are in the form of (unbalanced) RCA jacks. My speakers are amplified and have a balanced input.
I was looking for an audio transformer to convert the unbalanced into balanced signal, but I read here that

If everything in your facility is unbalanced and the wires are fairly
short, there's no point to using balancing adapters. But you can still
reduce hum, if you're willing to do some soldering:
Use the same kind of two-conductor shielded cable as you'd use for balanced wiring.
Connect the "hot" conductor -- usually white -- to the center pin of
the phono or phone plug at each end.
Connect the other conductor to
the sleeve of each plug.
Now here's the trick" connect the cable's
braided or foil shield to the sleeve at one end only.
Use shrink wrap
or tape to make sure the shield doesn't touch anything at the other
end.
Be consistent about which end of the shield gets connected... one
way is to always connect the shield at your patchbay or mixer, and
always leave the other disconnected.

Obviously this solution will result in a signal that is 6dB weaker than a real balanced one, but what are the implications concerning noise and hum immunity?
What is the length that should not be exceeded with this solution?


texts: difference between reverse saturation and leakage current

texts:
I searched a lot but I didn't find any answer

For a PN junction diode is the leakage current when the diode is reverse biased

Equal to the reverse saturation current??

If they are not equal so where does the excess current come from?


texts: What is the best way to understand a large existing HDL core?

texts:
Groundhog is a open source SATA host bus adapter core written in Verilog. I was wondering if anyone had tips on how to begin to understand how it operates? Is it to go from the high-level to low-level? or vice versa? Do I draw FSM diagrams for everything I see? What are some of the handy tips and tricks?

Note: This question is in the context of an individual who understands Verilog or VHDL already, but just has trouble getting his or her head around largish HDL designs.


texts: Having trouble running LTC2953-1 simulation on LTspice

texts:
I having a hard time in running the simulation for the LTC2953-1 which is a Push Button On/Off Controller IC , it also has other features which i'm not going to use for time being so they are disabled/ not used.
Here i am expecting the output (EN)[Green trace] pin to be latched high as soon as the Switch is pressed at pin (/PB)[Blue trace] for more than 6.4 seconds (1uF is set to have =~ 6.4seconds)where in the simulation it does not work, i hope it's something i've done wrong. Also i am getting this error which maybe the cause of not getting the IC to work properly..

I would really appreciate if someone would point out what might be the cause of this situation .
LTspice project file here

EDIT1 : Download link updated with a better host.
EDIT2 : I went ahead and put a 100K pullup and set up the switch as per indicated and now it alive but it nearly instantly works at the first falling edge like there is not delay, any idea what could be the culprit ? I'll dig more in the datasheet maybe i missed something.


texts: Proving the formula for parallel resistors

texts:
I am currently studying The Art of Electronics, third edition, by Horowitz and Hill. Exercise 1.3 asks to prove the formulas for series and parallel resistors. I am given the following relevant information earlier in the chapter:

The sum of the currents into a point in a circuit equals  the sum of the currents out (conservation of charge).  This is sometimes called Kirchhoff’s current law (KCL).  Engineers like to refer to such a point as a node. It follows that, for a series circuit (a bunch of two-terminal  things all connected end-to-end), the current is the same  everywhere.

Things hooked in parallel (Figure 1.1) have the same  voltage across them. Restated, the sum of the “voltage  drops” from A to B via one path through a circuit equals  the sum by any other route, and is simply the voltage  between A and B. Another way to say it is that the sum  of the voltage drops around any closed circuit is zero.  This is Kirchhoff’s voltage law (KVL).

I am trying to use this information (and ohm's law \$ V = IR \$, of course) to prove the parallel case \$R = \dfrac{R_1 R_2}{R_1 + R_2} \$. However, I do not understand how the provided information is sufficient to deduce this.
I am told that this is a good textbook, so perhaps it is just that I am new to electronics, and so I am not understanding something. Or, perhaps it is the case that the authors have failed to provide enough information to solve this problem without external knowledge. I would greatly appreciate it if people would please take the time to explain how it is possible to deduce this with the given information.


texts:
I implemented this circuit stripboard layout but when I connected this device to phone, there is no pulse in phone reciever. Please notify me what am I doing wrong!!

And here is my implementation picture. The 2 wires on the right are for output from my implementation to the phone.

The wires on the left are connected to the phone line that is input from the service provider to my circuit.

Please please help me. Please tell me what is wrong in this implementation. I would be very thankful.

edit: Here is the picture of the bottom. I made sure that the lines and connections are not short column wise. It may look that they are short in the picture but they are not!

I measured the voltage across all components in this circuit, But I was astonished that telephone line(Service provider line) has 50V DC and my input wires which are connected to service provider wires are just providing 4.86V DC to the circuit. I am using CAT 5e wires for input and output.
The voltage across every component is 4.86V DC except the voltage across the transistor and 220 Ohm is 4.01 V DC. Now please somebody help me.


texts: I'm working on a project using the MBED 1768, where I would like to connect two different externally powered sensors to one ADC pin on the microcontroller. Since they are externally powered, I need a way to switch between the input signals in such a way that only one sensor is connected to the input at a time, and this switching has to somehow be triggered electrically by the microcontroller. How would I go about doing this, preferably in a cheap way?


texts: Bridge rectifier - min. required protective resistor

texts: Looking at the datasheet for a MYS80 bridge rectifier, at the bottom it states Min. required protective resistor is 8 ohm. I could not find much information about a protective resistor in regard to bridge rectifier on the internet. Can anyone elaborate?


texts: Volume Control for Mixer Circuit using DAC Refence

texts: I am mixing two stereo audio signals together and would like to control the output volume using the (0-3.3v) DAC on my microcontroller. I'm wondering if there is a simple modification I can do to this circuit so that it accepts a 0-3.3v reference for volume or would I need an additional opamp stage? If additional stage is needed, what would you recommend as it's configuration?


texts: Are QSPI Interface and SPI compatible one with another?

texts: I have an SPI device (flash memory) and want to connect it to a microcontroller (nRF52840) which supports both SPI and Quad-SPI. Can the SPI device work in Quad-SPI mode in order to use the Easy-DMA provided by the microcontroller or are SPI and Quad-SPI incompatible?


texts: STM32L100RC and STM32L152RC disco boards fail on LL_FLASH_GetLatency() != LL_FLASH_LATENCY_1

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I have stm32l100 and stm32l152 disco boards and am using stm32cubemx and sw4stm32 IDE.

After creating default project for them in cubemx - I mean I go through board chooser and then leave everything as is except changing library from HAL to LL in project -> settings -> advanced settings for both RCC and GPIO and generate project for sw4stm32 - I import it to sw4stm32, add some code for LED3 blinking (to while loop in main function):

LL_GPIO_TogglePin(LD3_GPIO_Port, LD3_Pin);
LL_mDelay(1000);

build it and run it (it's written to board, I see status LED blinking), but LED3 does not blink.

When I run it in debug mode and step the code it fails at line (in SystemClock_Config() function):

LL_FLASH_GetLatency() != LL_FLASH_LATENCY_1

and goes to Error_Handler() which sits in while loop forever...

This happens on both boards and when I flash them with LED blinking ST's example it works, so it should be some firmware problem and I would say some initialization problem. I read STM32CubeL1GettingStarted.pdf and there is written that I should define right macro in stm32l1xx.h - which should be STM32L100xC or STM32L152xC and I did it - or rather uncomented existing one in that file. I even tried to add it to main.c file - it didn't help. And I tried to do it with and without this macro defined.

The only close question I found is this https://community.st.com/thread/15501 - but in v 1.8.0 of cubemx library this seems to be in right place.

I'm quite noob to these boards and have experience only with arduino so all this setup is quite overhelming for me right now and don't know where the cause could lie... so if anybody could direct me I would apreciate it really much.

UPDATE:
I even tried to generate project with older version of LL libraries (1.7.0 and 1.6.0), but still no progress.

Does anybody at least have some tutorial for blinking leds (or manipulating with GPIO) on L1 processors using LL library based on cubemx generated project?

Or could somebody send me working led blinking (gpio manipulating) code for STM32L100RC or STM32L152RC generated in cubemx using LL library? Thanks.

UPDATE2: Now I tried to do exactly the same steps using HAL library and it works (previously I used ST's cubemx blinking example), so it looks like a bug? I had some problems registering at ST's site so I wrote here first, but now it works, so I'm writing also there - will add link.

UPDATE3: link to my question on ST forum: https://community.st.com/message/177130

UPDATE4: so here is the code, if somebody wants to look at it, but as I said it's basic projecte generated in cubemx with added pin toggling: https://drive.google.com/open?id=1cMD3MVGXOofLq63syTW1itVMJL3xaIMh


texts: Maximize performance LM386 and 4Ohm speaker

texts:
I'm designing a very simple circuit which contains a microcontroller, an LM386 and a speaker.

I've previously asked a question:Help in designing a speaker driven by an LM386
and the answers helped me a lot.
However, there are still some fine tuning I need to do in order to maximize the performance:

The speaker is 4-Ohm (as I measure using a voltmeter). I don't know it's rating (I persume 1W)
LM386 can provide (typically,according to it's datasheet) 325mW.

Now, I just want to make sure the planning I'm doing is correct:

The microcontroller produces 2.4v signal (under 20kHz)
I multiply it by 0.05 (two resistors) and feed the amplifier with it
(I'm using basic LM386 apllication;GAIN=20) the amplifier multiplies it by 20 so we're back to 2.4v
I filter the signal with a simple RC circuit (30-Ohm,200nF, cutoff at 30kHz)
so basically now I have 2.4v on 4 Ohm.

obviously, the LM386 cannot provide so much power! my questions are:

what happens if I try to draw so much power from the LM386? will the signal be distorted? or simply less powerful?
Am I doing the planning right? I mean, in order to draw 325mW I simply need to play around with the resistors until I drop about 1.3v on the speaker,is that correct?

Thanks