texts: Facing Issue to interface switch relay & potentiometer with PIC16F877a

texts:
I am trying to operate switch relay when Resistance is at peak value (1Mohm) using PIC16F877A.

Now the issue is as below,

When i run the same code with Proteus , Its working fine. But when i run the same code on Hardware i am not getting the output i.e. Relay and LED is not getting ON.

Some observation from my end on hardware are as below.
1> When i try to increase  the value of variable resistor till the peak value, The value of 5 V is getting transmitted at a half variable resistor value
2>The pin at which relay is connected is not getting 5 v voltage as a result it is not getting operated.(highlighted in yellow in attached proteus schema)

proteus schema and C code is attached.

can anyone help me to find what might be the potential issues possible in this,
Appreciate the kind help in advance.

#include<pic.h>
#include<xc.h>

// CONFIG
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = ON        // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = ON         // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3/PGM pin has PGM function; low-voltage programming enabled)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

#define _XTAL_FREQ 2000000

void delay(int cnt)
{
    while(cnt--);
}

void ADC_Init()
{
    ADCON1=0XCE;
    TRISA=0XFF;
}

int ADC_Read(unsigned int ch)
{
           ADCON0=0X81;
           ADCON1=0XCE;
           TRISA=0XFF;

    int result=0;
    delay(50);
    GO_nDONE=1;
    while(GO_nDONE==1);
    result=ADRESH;
    result=result<<8;
    result=result|ADRESL;
    return result;

}
int main()
{
    unsigned int adcValue=0;
    unsigned int channel;

    TRISA0=0x01;

    PORTB=0X00;
    TRISB0=0X00;

    TRISC0=0X00;

     ADC_Init();
     while(1)
     {
         adcValue=ADC_Read(0);

                    if(adcValue==1023)
                    {
               RC0=1;
                       RB0=1;
                       delay(100);

                    }
                    else
                    {
               RC0=0;
                       RB0=0;
               delay(100);
                    }

     }

   return 0;
}


texts:
Is it possible to generate a PLL that has the same clock frequency at the output as the input clock has, but with a phase shift? The output clock should also change if the input clock has changed.

In the Intel ALTPLL (Phase-Locked Loop) IP Core User Guide -> Expanding the PLL Lock Range is only a description how to maximize the input lock range but that doesn't affect the output clock. Do I have to combine the expanded pll lock range with the Zero-Delay Buffer mode or any other operation mode to achieve this?

EDIT

The phase shift is a fixed value that is assumed to be less than 45 degrees. Right now I don't have the exact angle for the phase shift.


texts: Are there errors in the description of this circuit?

texts:
Background

The circuit describes the operation of a variable voltage power supply. In the description below the circuit diagram there are errors. Read through the description and note down any errors. Just describe the error and say why you think it is an error.

Don't need to go into any detail just say way you think the description is incorrect or could be improved.

My Answer

This is what I have come up with so far, please let me know if you can see any other errors:

Point 1 - How can you get 28V from the The 20V output transfer.

Point 2 - Transistor is not ideal, will not be constant current.

Point 3  - The voltage does not remain constant over very wide range
           of temperature with Zener  diode.  When Zener break down,
           voltage decreases as the temperature increases.

Point 16 – R10 is a typo, it should be R6

New Points

Point 16 – If the current is 1A, the Voltage across R6 is 0.47V and this is not enough to turn on the transistor as stated

Point 10 – Says that the load drawing less current will cause an increase in voltage however, according to ohms law this is not true and it would cause an decrease in voltage


texts: Will bridging the collector and emitter of a transistor damage it?

texts:
I have an inverter which uses a thermistor and a transistor to control the fan. The problem is that the thermistor temp is set so high that even when the inverter (transformer) is fairly hot the fan doesn't turn on but only turns on very high loads.
What I am trying to do is to add a resistor between the fan controlling transistor's collector and emitter so that the fan runs in slow mode even when the transistor is not emitting.
Will it damage the transistor if I bridge the emitter and collector?  Will the transistor still work in the circuit?


texts: Voltage Collapse in Power Systems: Loss of steady state?

texts:
I've read some papers on voltage collapse, and it seems to be described as the loss of a steady state solution for the system equations. Where the Jacobian matrix is singular, and voltage is monotonically decreasing.

My understanding is that if the voltage is monotonically decreasing, and bounded below by 0, then this must necessarily converge to a single solution greater than or equal to 0.

Wouldn't this limit then have to be a steady state? (A stable equilibrium, even?)

It seems to me that these statements are contradicting each other:

Loss of steady state
Monotonically decreasing
Bounded below by zero

This figure seems to indicate that there are no steady-state solutions for $$\lambda=1$$

The figure is taken from this paper:
https://www.researchgate.net/publication/3345120_Voltage_Collapse_in_Power_Systems


texts:
I need to make a voltage level shifter. It needs to translate a TTL logic level into a 12 V logic level.

I have applied the 5 V at the base and 12 V Vcc and took the output from the collector (not using any emitter resistor). The output was good, but the current was 0 mA when Vcc was 12 V and the phase was shifted.

I've tried connecting the load at the emitter and the voltage was just 5 V or less.

How do I make such a voltage level translator?


texts:
I am having trouble writing the code for flashing 6 LED's from PORTC on the PIC16F690 microcontroller.  The LED's should flash like the lights on a runway.

With the code that I currently have the LED's are flashing in pairs and out of order.

Here is the code that I have currently:

list p=16F690
radix hex
include "P16F690.INC"
__config _WDT_OFF & _BOR_OFF & _PWRTE_ON & _INTOSCIO & _MCLRE_OFF
errorlevel -302
org 0

count equ 20        ;we're going to need two variables
count2 equ 21

call initial
call Blink

initial         ; initialize registers
    bsf STATUS, RP0
    movlw B'00000000'
    movwf TRISC
    bcf STATUS, RP0
    bsf STATUS, RP1
    clrf ANSEL
    clrf ANSELH
    bcf STATUS, RP1
    return

Blink            ;flip the LED on or off
    movlw B'00000001'
    rlf PORTC,F
    call Delay
    call Blink

Delay           ; waste time
    movlw 0xFF
    movwf count
    movwf count2
Delayloop
    decfsz count,f
    goto Delayloop
    decfsz count2,f
    goto Delayloop
    return

END


texts: where should I place thermistor on lithium battery?

texts: I am going to use ICR18650-26J Li-ion battery, MCP73833 charging IC and BQ29733 battery protection IC.


texts: Chip Antenna -- Two nets to one pad? | Altium Net Tie

texts:
I've got a doozy of an Altium question:

I've got a chip antenna (2mm x 2mm or something like that).

The datasheet of the chip antenna calls for a 50 ohm line (in red in the graphic)

It also calls for a GND line (in blue) that intersects the 50 ohm trace.

Supposing I draw this layout in Solidworks and import it as a top layer fill, so the geometry of the traces are correct?

How would you assign the nets and/or layout the pads to the top layer fill of this shape?

I've tried creating the separate fill and it seems you can't assign just a chunk of the top layer fill to a net.

In this post showing a kind of similiar issue, what did the user do here to create those pad points?  Did he just create a top layer pad and drop it on the fill?

This is like a pro-grade Altium problem.


texts: I have a custom chopper motorcycle wiring issue

texts:
I have a custom chopper motorcycle. I have made a sequencing tail light system in the rear.
The sequencing works fine until the brakes are applied.  The brake lights causes the sequencing to pulse.
I have a DRUGZ unit/relay that has a default to the brake side.  However when the turn (momentary switch)
is pressed the relay cuts off the brake and allows the turn to function.  The problem is the timer/sequencers have a dead spot or triggers the relay to open/close. (clicking sound)  MY thought was to have a latching relay so when the turn signal is applied it maintains the closed position for the turn signal. I can't have any type of relay or component that needs power from the battery as this will drain  the battery and chopper won't start. Any advice would be appreciated.  No motorcycle retailer has a resolution to this issue


texts: Is there any standard size in Custom PCB Manufacturing?

texts:
I have no experience of dealing with the PCB manufacturers except the time that I once used PCBWay's service. I would like to know if there are some standard PCB board sizes that one needs to create when getting a custom PCB made?

My basic idea is to not incur extra cost for the loss of the material PCB Manufacturer faces. For example, Let's say they use a Board of 10*10 Inch to manufacture and I submit a custom board request with dimension of 7*7 Inch, Does that increase cost of PCB?


texts: 12vdc Adapters Outputting 12vdc Plus 20vac-23vac Dual Voltage, What's Going On Here?

texts:
So I have many 12vdc adapters which I buy from the local street which only sells used computer assessories and electronics. I use these adapters for routers, led lights, tiny ventilation fans etc.

Over the years I got several little tingle shocks each time I touch the output leads of these adapters which I learned to ignore. Very recently, I turned the knob of my multimeter to vac for investigation and found out that every single one of these adapters was giving a dual voltage. On the VDC section, it gave 11.5vdc-12.5vdc and on the VAC section, it were giving a reading of between 20vac-23vac.

I have investigated on this and the only explanation I have got is that Y cap next to the transformer maybe of the wrong rating.

Am I the only one to have stumbled on this fact about the commonly sold 12vdc adapters in the market?

Is this normal? For adapters to give dual voltage?

What's going on here?


texts: Why is frequency compensation required here?

texts:
Circuit requirements:

DC voltage gain: 50dB
Unity gain bandwidth: 50MHz
Phase margin: 45 deg(60 deg is recommended).

The circuit is completely symmetric, so M1=M2, M3=M4, and M5=M6. Therefore the DC gain of the first stage without the buffer is

\$A_{V_o}=-g_{m_1}R_{out}, \ R_{out}=\frac{1}{1/r_{o_1}+1/r_{o_3}+1/r_{o_5}+g_{m_5}-g_{m_3}}\$.

Since we need a relatively high DC gain I can choose \$g_{m_5}=g_{m_3}\$ to make \$R_{out}\$ maximum. So \$R_{out}\$ becomes \$R_{out}=r_{o_1}||r_{o_3}||r_{o_5}\$.

From now on let's follow two different approaches in order to satisfy the above requirements.

Approach 1:

The circuit without the source follower M7 and the compensation network.

In this case the load capacitor, CL(=10pF), is directly connected to the drain of M2. Let's first try to find an equation for the unity gain frequency, \$f_u\$. The circuit has two poles with the dominant pole situated at the output node. If we assume that the next dominant pole is located far from the dominant pole, the transfer function can be approximated as

\$H(s)=\frac{A_{V_o}}{1+s/\omega_{p_1}}, \ \omega_{p_1}=\frac{1}{C_LR_{out}}\$

Since \$|H(j2\pi f_u)|=1\$, the equation for \$f_u\$ becomes roughly

\$f_u= \frac{g_{m_1}}{2\pi C_L}\$.

With \$f_u\$=50MHz, \$C_L\$=10pF, the above equation gives 3.14mA/V for \$g_{m_1}\$ (Neglecting parasitic capacitances). So that's for \$g_{m_1}\$.

Now with the \$g_{m_1}\$ already determined and the DC gain 50dB (or equivalently ~320V/V), it's just left to figure out \$R_{out}\$, which, as per equation for DC gain, should be ~100kohms. So I can easily modify \$r_{o_1}\$,\$r_{o_3}\$, and \$r_{o_5}\$ in order to make the parallel combination of them 100kohms. That's for \$R_{out}\$.

Phase margin is 90 deg since the other high frequency pole doesn't affect the phase margin. A 90-deg PM doesn't have ringing and overshooting but trades off speed. But I think that's fine.

So it seems that the first approach did work well without the need for the source follower and the compensation network.

Approach 2

The complete circuit.

Here comes my confusion. I do not know as to why we need to consider those added parts while approach 1 worked out fine. Could anyone please explain as to how the second approach can be better than the first (if it's better at all)?

I think compensation is only required if the phase margin's dropped less than 45 as the result of subsequent stages, or if we want good unity gain bandwidth (?). But I do not see any good reason to invoke compensation in the above circuit.


texts: Send a frequency impulse when switch is active

texts:
I'm a newbie when it comes to electronics, so please forgive any glaring mistakes!

I am trying to create a simple circuit that sends an audible frequency/tone to a line-in/mic input when the mercury switch is active. Could anyone help me to identify what component I would need in the circuit to generate and send the frequency to the microphone input?


texts: Platforms for a small, programmable camera + wifi?

texts:
I would like to build a project with the Raspberry Pi Zero and the camera module. I'd like to write custom software to capture video, do minimal processing and send it on using wifi and/or bluetooth. The really small form factor is very important for me.

Unfortunately, as anyone interested in the RPI Zero would know, it is perpetually unavailable.

What are some alternative platforms that may be interesting for me to investigate that will allow me to do the same thing, hopefully with similar ease of development?


texts: When do capacitors "decide" to discharge?

texts:
I am a beginner electronics designer, but I have never been able to grasp "when a capacitor discharges".

What causes a capacitor to discharge? Is there a way to calculate a capacitance value to discharge with certain voltage and current values over a specific amount of time?


texts: Power supply circuit for a PIC16F88 Microchip

texts:
I'm coming from the world of software, where I feel quite at home - I spend a lot of time writing code. I do not feel at home in the world of electronics and designing circuits. I really REALLY would like to learn more about electronics and designing circuits. I know I could be good at it, too, if only I had the intuition for it - which I'm so obviously and desperately lacking.

One project I thought up to try and bridge the gap between these two worlds is by programming a Microchip, specifically the PIC16F88 (not super attached to this model in particular, I just picked this one because from what I've heard it's relatively straight-forward to play around with). I'm sure that once it comes to writing code I'll be more comfortable, but first I'd like to build the circuit.

I'm guessing there won't be a lot of components involved. I was thinking the first thing I'd like to try and do is to simply have the microchip toggle an LED on and off at 1-second intervals. Cool, so now what? That's kind of where my problem starts.

My first impulse is to design the circuit the same way I'd design a simple LED-light-up-circuit. Pick the desired current (in the case of a single garden-variety LED ~20mA), determine the corresponding voltage drop from the LED's datasheet, subtract the voltage drop from the total voltage provided by the power supply / battery, and finally use Ohm's law to determine the required resistance to limit the current to the desired value.

Well, how much current does an IC draw? How much is too little, how much is too much? I realize an IC is a completely different animal from an LED, but that's where my understanding ends.
Obviously there must be something wrong with my approach - the datasheet doesn't even mention current (at least not in any terms I can understand), however, other people are obviously able to design and power this chip just fine. I'm aware that how much current an IC draws depends on the IC and the application, and that there's things like Quiescent current and Input Sink / Output Source currents (just because I know these words doesn't mean I understand them fully) - so where do I find this information? Concrete numbers? Should I even be using this naive approach to build this more complex circuit? I know there isn't a conspiracy trying to hide information from me, but honestly sometimes in my journey through electronics and circuit design it feels as though there is hidden knowledge that's being denied to me.

If anyone can shed some light on my issue(s), or provide an intuition or general guidelines for knowing how to find the information you need to build a circuit, I would appreciate it. Also, if possible, explain it like I'm five years old.


texts:
I keep getting oscillation / uncontrollable noise with the following circuit.  My input is a balanced audio signal which goes through a TL082 op amp configured as a differential amp.  The output of the op amp feeds an STA540 power amp IC.  What's frustrating is if I use either circuit independent of the other, I have no issues.  I get a great, clean signal through headphones at the output of the op amp, and I get great, clean signal if I feed it directly into the STA540 and bypass the op amp.  BTW - the balanced inputs arrive at the op amp decoupled.  The output of the previous stage (not shown) already has decoupling capacitors.

I'm stumped.  Any help is appreciated.


texts: I would like to build a circuit similar to the two alternating flashing lights circuit, but using two disc vibration motors instead. I’d like it to have a speed control. The vibration motors have 30ohm resistance and my voltage is 4xAA batteries (~6V). When I set this up with a 555 timer based on schematics for flashing lights both motors run continuously rather than alternating. Can anyone offer advice?


texts:
As per shown in the below schematic, I have two ADG714(datasheet) octal SPST analog switches connected in the daisy chain configuration.
IC7 is connected to the STM32F303 controller. connenction of IC7 and the controller as follow:
SCLK-SCLK
MOSI-Din
Enable/CS - Synch
IC8's SCKL, Synch pins are tied with controller and IC7's SCLK and Synch pin respectively. Dout of IC7's is connected to Din of IC8 through 4.7k ohms pull-up resistor because Dout is open drain. SLCK is of 18Mhz.
Supply voltage:
Vss : -2.5V
Vdd: 3.3V
as per datasheet, abosolute operating condition Vdd to Vss is 7V
Configuration of the controller's SPI as follow:
Half duplex transmitter, 16bits data frame, CPOL = 0, clock phase is negative edge, MSB first and Enable or CS or Synch is controlled through GPIO pin.
I am not getting correct Dout output which should be 8 bits delayed as per the datasheet.
Below image is of Logic Analyser.
Channel0 is SCKL
Channel1: MOSI
Channel2: Synch/Enable/CS
channel3: Dout of IC7

Could you please tell me where I have made mistakes?
EDIT:
is it also possible that Pull up resistor's value is high and because of parasitic capacitance, time constant is high and switch can not 'drive' the output correctly?
as per the datasheet, sclk raise time to Dout valid output max time is 20ns


texts: Synchronising two microcontrollers for LED sequence and piezo speaker

texts:
I am making a piano keyboard which has a subsystem that plays a song whilst lighting up the corresponding notes that are to be played.
I have used a PICAXE 20M2 microcontroller for the LED sequence and a PICAXE 18M2 with a piezo for the actual sound.

They work well separately, however I am struggling to get them to play together in time, as they are at different speeds.

Is there a way I can make them sync? Or is it literally a case of trial and error until they work?


texts: Circuit analysis of mono audio preamp (K1803 Velleman)

texts:
For a school project I have a question about the first part of the circuit below (amplifies at 20*log(220k/2.2k)=40dB). I know that U2A is the amplifying part of the circuit. The problem is U1A and what is the role of this? I think in many ways it resembles an active low pass filter but it lacks a capacitor on the feedback. Isn't the RC on the input a low pass filter and how can I tell what the role of the first op-amp is?

EDIT: I will not use a lm324 but a lm358n (ST), the battery is just a symbol for 12V DC input.


texts: How to keep the signals at the pins on a Arduino upon software restart

texts:
I have a Arduino board, connected to a relay. When the digital pin on the board is set to HIGH, the relay closes. If the digital pin is LOW, the relay opens.

Now that from time to time, I will have to (software) restart the Arduino. The digital pin refresh, and therefore if the relay is closed, it will bounce open. Untill the Arduino board sends out a signal again.

Should I add a switch/ other electric components before the relay? Such that the signal could be "memorized"?

I have thought of using a time-delay relay. But once it is invoked, you'll have to wait until the delay time have pass to turn it off...


texts: How can this driver power a high-Side MOSFET?

texts:
I have seen several high-side MOSFET drivers which are internally isolated. As I can understand, isolated gate driving is a fairly new technology, since they encapsulate all the complexity in a single chip.

One such driver is the ADuM3322x (thanks to comment below), which is an isolated 4A Dual-Channel Gate Driver, designed to drive N-channel MOSFETs:

In the datasheet it is stated that,

  The ADuM3220/ADuM3221 digital isolators require no exter-nal interface
  circuitry for the logic interfaces.

If this driver is indeed intended to drive a high-side MOSFET, there needs to be an added bootstrap circuitry, which I couldn't find any mention of in the datasheet, unless it does not even require the bootstrap circuitry.

As explained here,

  You must drive the MOSFET between its gate and source terminals. Since the source terminal voltage of a high side MOSFET will be
  floating, you need a separate voltage supply (VBS: VBoot Strap) for
  the gate drive circuit.

I cannot understand how this circuit provides the needed voltage to power the MOSFET.

My first question is: How can this particular driver actually drive the high-side MOSFET?

Followed by: If this requires additional bootstrap circuitry, are there isolated high-side drivers which come with in-built DC-DC converters?


texts: 3D stacked ICs; why are they not common yet

texts:
I have heard/read in the past that people are not looking at constructing integrated circuits as stacks of individual dies, connected together inside a package. This has been done for example where a die for pure memory was connected separately to a bigger circuit of digital circuit within the physical package before the device leaves the factory. This makes customization easier and cheaper.

However, I do not read about this methodology becoming pervasive.

Why are the reasons that "3D ICs" have not become pervasive yet?


texts: SRF and Operating frequency for inductor

texts:
As a rule of thumb the SRF(self resonant frequency) of an inductor should be higher than the operating frequency. I need to know why this inductor has lower SRF and why the operating frequency is much higher than SRF.
As I know the inductor and a chock are the same for using them with the same inductance and SRF. How is it possible the WA8514-AE(SRF<250Mhz) inductor is used as a RF chock for this application which frequency can be up to 2.7Ghz.


texts:
While using MATLAB's Pwelch function, I am not able to match the noise floor of the "Modelled" ADC to (Delta)^2/6 {1 sided Spectrum}.

F_tone = 1e3;                       %Frequency of Tone
OSR = 64;
Fs = F_tone * OSR;                  %Sampling Frequency
time_step = 1/Fs;                   %Time between samples
total_number_of_cycles = 2^12;      %Total number of complete cycles to
                                    %                      simulate for
FFT_number_of_cycles = 2^7;         %Number of cycles used in 1 FFT
                                    %                      computation
Amplitude = 100;                     %Amplitude of the sine wave
Bits = 8;
q = 2*Amplitude/2^Bits;             %Quantisation Interval q = 0.7812
NG = 0.375;                         %Noise Gain for Hanning Window
CG = 0.5;                           %Coherent Gain for Hanning Window
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
time_period = 1/F_tone;
t = 0:time_step:time_period * total_number_of_cycles;
y_noiseless = Amplitude*sin(2*pi*F_tone * t);
%%%%%%% Adding Noise
y = y_noiseless + (1.5*q)*(rand(size(y_noiseless))*2-1); %Adding 1.5LSB noise
y_quantised = floor(y/q) * q+q/2; %Quantising
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
N_fft = (OSR) * FFT_number_of_cycles;
Fmin = Fs/N_fft;
sn = (NG * Fmin) / (CG)^2;
[S,F] = pwelch(y,hanning(N_fft),N_fft/2,N_fft,Fs,'onesided');
S = S * sn;
semilogx(F,20*log10(S));
%[![This gives the following image][1]][1]

N_Floor = 10*log10( ((q^2)/6) * (1/max(F)) ) % = -54.9772 dB

The Signal strength in the plot is matching theoretical expectation.
Theory says it should be 20*log10(2*Amplitude^2/4) = 73.9794 dB, and I am getting 73.9798 as shown in the image.

The noise floor spread by theory should be -54.9772dB, but I am getting ~-75dB in the plot.

I am not sure of the following things.
1. Am I modelling the quantisation correctly?
2. Which of my noise floor numbers are wrong? Theory or Simulated?


texts: Arduino ECG sputtering out totally random values

texts:
I have encountered a problem in my ECG/EKG design.

I am trying to make an ECG using an Arduino as a microcontroller to send/retrieve heart rate measurements via Bluetooth (JY-MCU.)

I know my circuit is working because when I place an LED in op-amp output and its ground, I get a slight dimming of the light if I gently put my hand on the leads.  I know the issue is with my code.  I have been working on this project for a while and still can't find a solution.

Here is my schematic:

Here is my code that I think is incorrect.  The code is just the bare minimum.

// External variables
const int  signal = 8;    // Pin connected to the filtered signal from the circuit
unsigned long time;
unsigned long frequency;
char freq[3];

// Internal variables
double period = 2000;
double starttime = 2000;
double input = 0;
double lastinput = 0;
unsigned long death = 0;

// initialize the library with the numbers of the interface pins

void setup() {
pinMode(signal, INPUT);
Serial.begin(9600);
}

void loop() {
delay(500);

time = millis();
input = digitalRead(signal);

 period = time - starttime; // Compute the time between the previous beat and the one that has just been detected
 starttime = time; // Define the new time reference for the next period computing
 death = time;
 frequency = 60000/period;
 freq[0] = frequency/100+48; // Sort the hundreds character and convert it in ASCII
 freq[1] = (frequency/10)%10+48; // Sort the thents character and convert it in ASCII
 freq[2] = frequency%10+48; // Sort the units character and convert it in ASCII
 Serial.println(freq);
}

All I'm getting is either 120 or 119 as my value.  It fluctuates between those two.  I tried changing my resistors out but that didn't do anything.  I also completely took the wire between pin 8 and the breadboard out, and it still fluctuated between 119 to 120.  I don't have any idea what is going on here!  I would appreciate it if someone could help me out here.


texts: Using ESP32 and external WatchDog STWD100NYWY3F

texts:
I want to use ESP32 with the STWD100NYWY3F external watchdog timer. Below is my connection diagram.

On WDI with 33 pin, periodic pulses are sent to the watchdog timer.
If the timer is not reset, then a low level is sent from WDO to the EN output, which should reset ESP32. EN output is constantly raised to a high level, which should block its operation, as soon as a low level is applied to 32 outputs - the timer starts and controls the system.

Questions:

I correctly understood the principle of operation and the scheme?
Will it work with ESP32 or do I need to change something?
On one of the forums I saw the following:

Is this a problem for ESP?


texts: 2 Bit Synchronous circuit that operates only with clock [Q]

texts:
I am attempting to make the following digital telephony circuit by applying Time Division Multiplexing(TDM).

I am having trouble figuring out how to create a 2-bit counter that counts from 0 to 3, adding one at a rising edge of a clock, and then resets the count to zero and so on.

The 2-bit counter will act as the selector line for the MUX, DMX, and the 2-bit decoder.

I am planning on implementing a synchronous J-K Flip-Flop, but it requires two inputs (J and K) in addition to the clock. According to the diagram below, the only input into the counter and that runs the counter is the clock. So how can I implement a J-K without needing the J-K inputs and only needing the clock, or is there a better flip-flop / latch that can be used? Note I am only 2 weeks new to digital circuit design so don't know much..


texts: Power regulation and isolation for low current device

texts:
I'm looking for a solution to regulate power and provide isolation for a 3.3VDC system. I am using a 5VDC 500mA power supply that needs to be regulated to 3.3VDC with isolation to protect analog sensor signals from noise.

The circuit can draw up to 200mA and as little as 2mA. I've been looking at isolated regulators and it seems that there is a minimum load for the component to effectively regulate voltage based on my understanding of the datasheet. Is this accurate and if so is there a good solution for isolation and regulation of this circuit?

Example regulator: MEU1S0503ZC


texts: How can I know the number of units consumed by each A.C. in a home

texts: The question is fairly simple. I have three air conditioners in my home and the bill for their electricity consumption comes combined as only a single meter is installed. My question is Is there any other way possible to calculate the amount of electricity consumed by every A.C. separately without installing any new meters?


texts: Two issues, re: driving relay with logic levels

texts:
Hey people I'm driving a relay with a arduino-teensy with 3.2v logic levels.

Some background. I'm going with a mosfet because the coil voltage is relatively high. The relay will have 20a/220v contact voltages. I'd like to have an LED turn on when the relay is active, and I'd like to have a manual switch to override the logic control of the circuit.

Two questions.
1) could someone verify that this is the best way to  light up the LED? I read on line the parallel circuit is better than running the LED in series, if it fails then the relay fails.

2) Which choice would be best to use a circuit to override the logic level coming from my arduino? If the arduino pin mode is:
pinMode(relayPIN, INPUT);
does it care if I put 3.2v external on that thing? Or would it be better to just connect the drain side of the mofset (Q2) to ground?

thanks much.


texts: Internal resistance of Function Generator

texts: I'm using a function generator that has a 50ohm internal resistance. Does this affect any circuit that I may connect it to and if so, how would it affect the results?


texts: uC platforms to consider for faster CPU and 30+ GPIO pins

texts:
I am building a Persistence of Vision project with 120 RGB leds (=360 total lines to be controlled). We have settled on the TLC5940 for driving the LEDs (and could be open to changing this), however, now we have a problem getting the data fast enough to the LED driver chips. Currently we are using ATmega328/ATmega128-class chips which top out at 20Mhz, and we aren't able to process the data to be loaded onto the TLC5940s fast enough. Should we consider another uC?  The desiderata are:

Low cost/uC
Low startup costs (For instance, CPLDs require a certain initial investment to get started with)
3.0-5.0V
Ideally available in a DIP package for easy prototyping
30+ GPIO lines (to load the LED controllers in parallel)

This question may be an intellectual poor cousin of this question, however, I think our requirements are somewhat different.

Details: why ATmega328 isn't fast enough (so far)

In the ideal world, we should be able to load the data for all LEDs in under 746uS (that's the project requirements), and again, in theory, if we bitbang at 2clocks/bit we should be able to do it in 108uS @20Mhz, however, all the bit shifting to decide what intensity to send to each LED right now gives us 1536uS load times. This is with avr-gcc OPTLEVEL=2 or OPTLEVEL=3, all sorts of loops manually unrolled, parallel loading of all LED controllers, and every time-saving technique we can think of.


texts: Whats the metal plate on some transitors with the big hole meant for?

texts: A lot of transitors have this metal plate on the back with a hole in the middle. Whats the purpose of that?


texts:
I want to build a circuit that will output multiple voltages (one at a time) to supply an FPGA.  The core volt will be constant voltage. I want to be able to supply different voltages for the FPGA output and input pins.  Virtex4,5,6 and 7 all can support 1.2v, 1.5, 1.8, 2.5  to name a few. I would like to have a MCU or another FPGA select different output voltages with SPI, I2C or GPIO.  I was looking for a TI regulator module that supported I2C or SPI and found none. I also was thinking of using a LM317 adj regulator ( open to your input) and switching in and out resistors. I could switch the resistors in and out with a FET controlled by GPIO with a decoder.

I know it can be done, because I used a board in College that did just that. It was controlled through a FPGA and usb software. I did not have a schematic of this board and the vendor who sold it wouldn't give me any info.

I want to be able to supply the above voltages with 1A, 2A, 4A and 10Amp - depends on the FPGA used.


texts: Are alternate connection points on a PCB bad?

texts:
If a PCB is designed to provide two connection options for the same signal, for example it has a banana plug connector on one side of the PCB but also exposes the same signal on another side of the PCB through perhaps a large row of pin headers (so that the PCB can be used as a plugin module).

Would there be any negative consequences when one of the options is disconnected. Would the unconnected trace be especially susceptible to producing or receiving noise over a case where it would be connected?

Would this generally be considered bad design practice to even have multiple options on the same PCB far apart?


texts:
Regarding Altera's MAX10 Cpld, I got some questions regarding the interface of this CPLD with 3.3V devices.
I have set pins to 3.3V LVCMOS and I got this warning message in quartus:
"Warning (169177): 100 pins must meet Intel FPGA requirements for 3.3-, 3.0-, and 2.5-V interfaces. For more information, refer to AN 447: Interfacing MAX 10 Devices with 3.3/3.0/2.5-V LVTTL/LVCMOS I/O Systems."
Looking at the AN447 document, it mentions on page 2
To my understanding, if VCCIO is set to 3V, there is no need for anything to be done when it comes to interfacing with a 3.3V device.
But that makes little sense to me, I don't understand the reason why when VCCIO = 3V, then all issues are solved:

Why bothering using 3.3V as VCCIO then, why the trouble?
Could anyone confirm I'll be fine interfacing directly with a 3.3V device when VCCIO = 3V?

Thanks for your inputs. I'm sure there is a big misunderstanding there and I want to clear that out.


texts: Op-amp output wanders over the course of a few seconds

texts:
In one of our designs we are doing signal conditioning of a load cell (Wheatstone bridge)

We have an issue where the main instrumentation amplifier an AD8224 has an output signal that wanders by around 20mV over the course of 10's of seconds.

We have gone through troubleshooting the signal chain and tracked the issue back to here, the above plot is taken with the inputs to the amplifier shorted out and connected to 0V via 500ohms.

Supply to the op-amp is +-15V, and has 0.1uF bypass directly near the IC, and 10uF about 3cm away. We are using a gain resistor of 49.9ohm which should give a gain of around 991.

We are not worried about the high frequency noise, this gets tidied up latter in the chain.

I am keen to hear peoples thoughts on what could be causing this, as I am out of ideas.

EDIT:
A bit more poking around and I was able to find one of our old board revisions that does not show the same issue, these boards are modular, and I was able to slot in the new and old next to each other to compare the results.

Channel 0 is the old revision and shows what I would expect of changes due to thermal effects.

Channel 1 shows the same board as per above.

I note that the old board used a TI INA2126 instead of the AD8224

From poking around the datasheets I also found the AD8222 is very similar to the AD8224 but with a better temperature co-efficient and will order some in for testing, however I feel this is clutching at straws.

EDIT:
An additional interesting observation is that if I remove the gain resistor (setting a gain of 1) the wandering goes away, from this would I be correct to infer the issue is in the input stage?


texts: How can I use/convert the touchpad, keyboard and screen of an old laptop to use them with a desktop PC?

texts:
Is there a common way for all the laptops' hardware, like screen, touchpad, and keyboard, that can be followed in order to use them with a desktop PC?
What I need to do, to use screen, touchpad, and keyboard of my old laptop with my desktop PC?
Would be fine if I disassemble my laptop, then I remove the screen connector from the motherboard, and I try solder pin-by-pin of the laptop screen connector with a VGA cable?
Is there a standard connector for laptops' screens?
Concerning the keyboard and touchpad I was thinking to do the same thing but with an USB cable, would it be ok?
The purpose of this question is also to become a sort of guide for all the people that are trying to reuse the hardware of their old laptops.


texts:
Several communications standards use LFSR-based self-synchronizing (multiplicative) scramblers that are never reset to an initial state after initial power on. For example, 10GBASE-R Ethernet specifies the following scrambler:

According to IEEE 802.3-2015 clause 49 "there is no requirement on the initial value for the scrambler", however it seems clear that the initial value should be non-zero, otherwise an all-idle signal will keep the output at zero for all eternity.

I have not done the math, but I suppose the circuit guarantees that an all-zero signal (idles) will never cause the LFSR to return to zero, given a non-zero state. However, it seems clear that there is always some pattern that will cause it to return to zero. If an all-zero signal follows, the output is essentially broken until another packet is sent, which can be never.

I realize that the scrambling technique is fundamentally imperfect since it can provide long series of zeros or ones, but isn't this situation more serious considering that it will potentially never resolve itself?


texts: Determining the state of this BJT transistor

texts:
My question is about the state of Q2 in the following circuit.

For the above differential amplifier a text says when Vin1=+1V and Vin2=-1V, the transistor Q1 will be active but Q2 will be in cutoff.
I'm having a bit confusion for this conclusion.

If I start thinking first from Q1 then I can say that since Vbe1=0.7V the voltage at point A=1-0.7=+0.3V.
This means since Vin2=-1, Vbe2 is reverse biased hence the Q2 is in cutoff.

But if I initially start thinking from Q2 then I can say that initially Vin2=-1V and Vee=-9V, hence Vbe2 is forward biased and the transistor Q2 is active.

Where am I logically wrong here?


texts: I have 0-5 V analog value coming in, and I need to convert it to a high or low 5V digital signal.  Essentially, I need to create a 1-channel A/D converter.  The idea is that when my analog voltage goes above a certain threshold, it will set the digital output high, and vice-versa.  I saw something about being able to do this with op-amps, but I don't remember where I saw it.  I also want to do this without using a microcontroller.  Any ideas?


texts: constant voltage drop at (relatively) high current

texts:
I'm making a power supply using some decade switches and resistors.  The idea is to dial a voltage, much like a resistor substitution box, but get a voltage out instead of a resistance.  I'm using the LM350 (high current version of LM317), but the LM317 voltage drop makes it nearly impossible to get a circuit that will make that work (set up like a standard resistor box, but with 160 ohms, 1.6K and 16K resistors at the three decades, and a 500 ohm between out and adj.  To compensate, I'm currently thinking of just adding something to drop the voltage 1.5V-2V after the regulator, and compensate with a pot in front of the switches. The problem is, a simple diode drop is too inconsistent across temperature and current, and I can't seem to find another good solution.  I was thinking setting up another LM350 in constant current mode, but set to something like 50A, or set to regulate to something like 100V so that it keeps the voltage as high as it can go, minus the drop.  It wouldn't actually pass that much voltage or current, it would only be given maybe 24V at a couple of amps, but because it is set so high, it should try to bring the voltage as high as possible, but I don't know if that will work.
The schematic is approximately what the final circuit would be (minus filtering caps and some diodes) The three boxes with resistors are rotary switches.  The part I'm asking about is basically just if there will be a 1.25V drop between N$2 and VOUT. Thus, if whatever voltage is dialed by the rotary switches (as in a resistor substitution box) will be present at VOUT.

TLDR: I need to drop a DC voltage by 1.5-2V at about 6A, the exact value doesn't matter, but it must be very constant (\$< \pm 0.02\text{V}\$) across reasonable temperatures and currents, and not overly complex or expensive.  Is there any easy or "correct" way to do this?


texts:
First of all - I am just reading up and will not perform any real life installations! ;-)

If you have some 400V 3 phase equipment (e.g. a 3 phase motor), what is the practice for controlling the power to it using a relay? Can you use a single phase relay(e.g. TERMSERIES TRZ 5VDC 1CO 16A 250V/30A) and break one of the phase, or do you use a special 3-phase relay that breaks all phases?


texts:
I have a MSP430G2231. My ultimate goal is to communicate with a device that wants 1 bit of data each microsecond. I believe this is too fast for timers, meaning I need to handwrite assembly code that uses correct amount of cycles for timing.

ti.com says the CPU's frequency is 16MHz. The manual says that "call" takes 5 cycles. Does this mean it takes 5/16000000seconds?

To verify this, I tried to make a simple program that's supposed to toggle the LED every second by counting down from 65536 61 times. This should use ~65536*61*4 (about 16 000 000) cycles. Assuming the previous paragraph is correct, that should take 1second, but it takes 12-13 seconds.

hello:
    mov.w #62, r15
    clr.w r14
hello_next:
    dec.w r14      ; 1 cycle
    subc.w #0, r15 ; 1 cycle
    jnz hello_next ; 2 cycle

    xor.b #LED1PIN, &P1OUT
    jmp hello


texts:
I have a police scanner that has a couple of modules in it.

One of these modules is marked 390G (Data Sheet)

I can't see the other modules number but it looks identical. I know they are NOT the same however because the 390G needs a flat head screwdriver and the unidentified one needs a phillips.

Now from what I can tell the unidentified module is the one that controls the frequency. When I turn it with a screw driver I can hear the static pitch in and out. The 390G however doesn't seem to change anything so I don't know what that does.

My question is, how does tightening or loosening this module effect the frequency that it picks up?

Also, the police scanner is a digital one so it still cycles through the same frequencies on the LCD. I suspect that it thinks it's cycling through the same frequencies but in reality I have changed the scope of frequencies it is scanning. Is this a correct assumption?

Note: I am not attempting to modify this device to intercept cell phone traffic. I read the warnings. Please refrain from posting FCC guidelines and regulations.


texts: Need help with generating a bi-phasic current

texts:
I'm trying to generate a symmetric biphasic current pulse using a Grass S88 Stimulator.

Here's a diagram:

SG is a signal generator with two outputs, S1 and S2, which are generating a periodic pulse wave (same period in both). SIUs are transformers to isolate the signal. One of the SIUs is set to reverse the polarity of the input. CCUs are constant current units that as supposed to (I think) convert the voltage signal to a current signal.

I need a biphasic current output so I need to combine the outputs of the two CCUs somehow. How should this be done? How do I get my final biphasic current as given in the diagram?
Also, what should be done to ensure that S1 and S2 are exactly out of phase? I don't want amplitudes cancelling each other out.


texts: Why does ST recommend 100 nF decoupling capacitors for a 72 MHz MCU? (And not 10 nF.)

texts:
I've been reading about decoupling capacitors, and I can't seem to understand why ST recommends 100 nF decoupling capacitors on a 72 MHz ARM microcontroller.

Usually 100 nF decoupling capacitors are only effective up to about 20-40 MHz due to resonance. I thought 10 nF decoupling caps were more suitable since their resonance is closer to 100 MHz.

(Obviously, it depends on the package and its inductance, but those are just ballpark values from what I've seen.)

According to the STM32F103 datasheet, ST recommends 100 nF capacitors on VDD and 10 nF on VDDA. Why is that? I would think I should use 10 nF on VDD too.


texts: LED to music sync barely blinking even with amplifier

texts:
I am currently working on LED to music sync circuit. The schematic is displayed below:

simulate this circuit – Schematic created using CircuitLab

Mostly I am using this schematic image: . Because I was unable to find TIP31 transistor I used quite similar - BD243C. What I found out, I also needed an amplifier for my headphones signal, because the voltage is to low to activate transistor so I bought TDA2822M and build directly from documentation the amplifier: http://pdf.datasheetcatalog.com/datasheet/SGSThomsonMicroelectronics/mXqwxzy.pdf

After all of this unfortunately LED is barely blinking. To be honest I am not an expert in electric circuits and I have no idea what is wrong with it. Can someone please give me an advice what am I doing wrong.

EDIT:

I've edited my initial circuit due to the Spehro Pefhany answer. Now the outcome is quite interesting. When I plug in jack to the mp3 player the diode is turning off. When it is not connected it is turned on.

EDIT2:

I suppose I might have just found an error. The amplifier isn't working. All the time I've been connecting my wire to the mp3 player and now I connected it to pc jack. With PC connected everything is working even without an amplifier. Even it is working better, because from amplifier I have outputs with resistors.

Now I need to check somehow my amplifier and probably get the new one. I'll update this questions when I'll know if my bet is correct.


texts:
I need a precision decade voltage divider. And there is a product from Visahy just can do what I want. But it's soooooooooo expensive! So

Why they are so expensive?
I need the ratio tolerance at least ±0.05%. And if it's acceptable the absolute ratios may not be in 'decades' precisely. Can I use several discrete 0.1% metal film resistors in series to achieve this?


texts: Better way to divide voltage for input to an ADC DAQ?

texts:
I would like to monitor relatively higher voltages (up to 160V) using an ADC type DAQ.  Most DAQs that I come across can handle around 5-10V of analog input, requiring the voltage to be divided.  Here is one I like https://labjack.com/products/t7 .  I was planning on running a simple voltage divider to an op-amp buffer (voltage follower) and finally into the input of the DAQ.

My thought is to use something like 3.3 MOhm (R1) and 105 kOhm  (R2) to divide the 160V by ~32 (~5V).  Then run that output to an op-amp voltage follower and finally into the input of the DAQ.  I'm not sure how to size the resistors since the op-amp buffer should be high impedance and limit the current draw.  I sized them so big to ensure I'm not drawing much current.  Since I am monitoring the voltage, I do not want to load down the source.  I want to know if this is a good way to do it, and if there are any better ways.


texts:
First some background information.

There is one product (a sensor) bought from a far eastern manufacturer, bless their white cotton socks, that uses the STM32F103V microcontroller. The firmware that was originally supplied, along with any updates has some nasty bugs that turn the product into a brick at random intervals (and the product is expected to work without any downtime for months).

At the beginning they were responsive and eager to provide support; after the purchase they are not providing any reply to any of the e-mails sent.

So the solution is to rewrite the firmware by myself.

On to the problem now.

The microcontroller already has a bootloader and there is no JTAG port available on the boards. Is there any way to find - from the bin files I have - what is the start address of the firmware? Due to the bootloader, it is not 0x00000000. Also, is there any other thing I should be aware of when writing the firmware (ie: certain settings for registers, aso)?


texts: Why there are two diodes instead of one used for an LM35 negative temperature circuit?

texts:
See the system examples of the LM35 temperature sensor datasheet on page 16, see picture.
This should be used for negative temperatures. However, the voltage change is 10 mV/C and it supports -55 C minimum, resulting in -550 mV. A diode (1N914) has a typical drop of 600 or 700 mV .... why are two diodes used, and not one?

(I play to use a 1N4001 or 1N4148 since I have plenty of them).


texts:
I want to set a delay of around 5s between power supply turning ON and my circuit getting power.

Here is the circuit I have come up with:

Datasheet of mosfet

I am using a 555 timer to set the startup delay and N-channel mosfet to supply power to the load. Most of the through hole mosfets have Rds minimum at around 10 V. Luckily I had 12V supply readily available so I am using 12 V to switch the 5V line as shown above. P4 is input and P3 is load.

Is my circuit correct?

Besides initial turn ON delay, I want the circuit to reset when power is disconnected (in half a min or so. if it happens within 1-2 seconds, it will be even better). To achieve this, I have put R7 (100K) discharge resistor on the capacitor which will discharge it and get the circuit in working state again. Is there a better way to do this?


texts: When is a differential choke preferred to an LC filter and vice versa?

texts:
Both single LC and differential choke are used for attenuating differential mode noise.

I only know that LC filter has resonance issues. Is that the only reason a differential choke is preferred?

Can a differential choke be considered as a powerful inductor and be used as used in an LC filter?

I cannot find information about such comparison. Can you give two scenarios where one is preferred to another?


texts:
I have a 12V 8A 35mm-stroke solenoid from eBay (similar to this listing) which I am powering with a 12V 20A PSU. I am using two of them for a homemade pinball game. At the moment they are hooked up directly to the PSU via a couple of arcade style buttons.

Problem: They have only just enough power to flip a 19mm steel ball up a 90cm playfield.

After doing a little research, I think I can use a similar circuit to this, using a Teensy board and a P30N06LE 30A 60V mosfet (also have some NDP6020P P-channel if that's better suited?)

simulate this circuit – Schematic created using CircuitLab

I have read a few articles which talk about adding a capacitor and resistor into this circuit to provide more initial "power" and then a lower "hold" current. I think the design for the "hold" part adds C1 and R3.

simulate this circuit

My Question

Where and how can I add another capacitor to give it the initial boost of power and what values should I be using for the passive components please?

Update:
I have found this article by Paul Rako / Bob Pease which seems like it could help, although mine are 8A solenoids.


texts: Performance affected by bending flexible PCB antenna?

texts:
I am doing an electronics project that involves transmitting and receiving information on the 915MHz ISM band. I need to make the enclosure as small as possible. However, that means that I don't have a lot of space for my antenna that is tuned for the 915MHz ISM band.

Here is the picture of how it would look like in the enclosure:

Hwow will the performance be affected by the fact that I am folding the antenna like this? Am I better off just using a helical antenna in this case?


texts:
I'd like to make a little device I can stick onto a Frisbee that could measure stats such as RPM/speed of the Frisbee when thrown. Would this be realistically possible?

I was looking into near-field communication to transfer the data from the Frisbee into a smartphone, but it's just an idea. It seems like it would be difficult to make something small enough to not affect the flight of the Frisbee itself. Can anyone think of any ideas for this?


texts: How is this 5-24V input circuit working?

texts:
Since I require some kind of wide range input (going to a microcontroller) for a new project, I looked through some designs that are already in use (or were considered at some point) for other products in my company.

I found this circuit, which seems to accept anything between 5-24V to drive the optocoupler. I have trouble understanding how the MOSFET works in this constellation, since i don't have much experience this those.

My guesses regarding the function of the diodes and the resistor:

D17: probably reverse polarity protection
D18: transient voltage suppression
R18: basic current limiting

The MOSFET seems to "regulate" its resistance in a way, that it just provides enough current to supply the LED, independent of the input voltage.

How does it work in principle?
How to calculate the voltage range that is actually supported?


texts: Is this deal on anti-static foam too good to be true?

texts:
Currently, my integrated circuits are free to bump around in one of the compartments in my parts organizer. I used to have a bunch of anti-static foam rectangles to keep them plugged into, but I threw them (the foam) out because I was annoyed that I didn't have enough to hold all my ICs (strange logic, right?).

I found this deal on Amazon: http://www.amazon.com/Techni-Stat-Foam-Anti-Static-Pink-12/dp/B000PDJ5CQ/ref=pd_cp_hi_4

It's about $5, including shipping, and I get a square foot of material. Is this a viable solution to keeping my ICs safe? I haven't researched Techi-Tools too deeply but they seem like a legitimate brand.


texts: How to create a delayed clock pulse, then return to regular clock cycles

texts:
I am attempting to configure an LCD with just IC chips and I've been having problems. I've worked out that the main problem I am having is in the initialization of the lcd. It needs a goodly amount of time to initialise, and then in needs a couple of more configuration instructions.
I would like to give the lcd time to initialise at startup, and then change to a regular clock pulse after 3 delays. So rather than the regular clock pulse (shown in red) 3 long pulses, then back to the regular 555 spacing (shown in blue).

Is there anyway to do this using a combination of IC chips? The delay on the bottom of the clock cycle could be the same long delay, the off time isn't really relevant.


texts: Let's take an example in which the recommended beta for a transistor's(NPN) saturation is 10.If you use a forced beta smaller than 10,will the transistor still be saturated succesfully?Can hFE be small enough to damage the BJT?


texts: How to safely connect the Arduino 5V Pin with a 5V wall wart and USB TTL converter for data transfer?

texts:
I'm currently developing a project that involves components with about 2A current draw. These are controlled by an AVR Atmega168 processor with Arduino bootloader over a CH340G USB TTL converter. The controlling is done by a program I've written in Windows, so there's an data transferring additional to the USB powering. (CH340 datasheet: https://www.olimex.com/Products/Breadboarding/BB-CH340T/resources/CH340DS1.PDF).

Since there's no way a USB port can supply a current close to 2A, a wall wart will be required to supply additional power. ATM I've found no other solution than to tie all 5Vs together. At now 5Vs and GNDs are planned to be connected through 5V and GND planes on a manufactured PCB. And that of course makes me bump into some serious concerns about the safety of the ICs:

What will happen if e.g. the wall wart supplies 5.1V and the Computer
USB delivers 5.0V? Will either the ICs or the computer USB port get
bricked, maybe both since it is somehow some kind of a short circuit?
What could happen if I connect the wall wart first and connect USB
afterwards? Or USB first and then the wall wart? Is there a chance of
generating magic smoke?
I've heard about ground looping. Is that a problem in my circuit? If yes, what can I do about it?
Is there any good protection circuits or things like that to make sure that connecting 5Vs to each other directly is safe and data transferring still works?
The CH340(G) datasheet says that for high current applications, it's safe to tie 5V USB to 5V external if bridging the USB 5V over a 1 Ohm resistor. Does that make much sense? Does the resistor act like a protection?
I've seen the Vin and VCC solutions for Arduino Unos, Megas and Nanos. They all have protection circuits but require higher input voltages <6V. That would require an additional step down regulator and would give additional unwanted heat since 6-8V wall warts are rather uncommon, so 9V would be next. Is it possible to get rid of the VReg and maybe use other parts of protection circuitry?
Are there some other problems that exist but I forgot to mention?

Sadly components can't be turned off while being connected to USB - that would make my project senseless after all :-)

Thanks in advance for any kind of help!


texts:
I have been using Eagle for quite a while now but there is one thing that continues to bother me while I am using it. I have made the ground plane cover the shape of the board, however, when I am making minor and frequent changes to the design I have to keep clearing this layer and then making the changes, rats-nesting it again to make sure the ground plane goes through properly (especially for decoupling caps). If there is a problem I will need to 'ripup' the polygon that makes the ground plane in order to clear it and then make my adjustment and repeat.

This really bothers me because if I am making tiny adjustments, I will be fully zoomed in and have to zoom all the way out, find the board edge and clear the ground plane.

So my question is:
Is there a quick way to clear the ground plane flood, a tool like 'un-rats-nest' would be fun but I doubt that will exist.

Note: I do not want to delete the ground plane, just temporarily hide it if you will.

Another thing that bugs me is 'CTRL-Z' will not undo the flooding but that is pretty much the same issue.


texts: Logic Analyzer with ground probe missing

texts:
I'm playing around with a USB logic analyzer (DSLogic Plus) to look at some RS232 signals. Everything seems to be working fine, but I just noticed that the probe to ground wasn't connected properly. So only the RX and TX lines were connected to the logic analyzer.
How was I getting any kind of good data without the ground being connected?
Just to set the expectation level: I'm a software guy who knows something about programming low-level devices, but my electronics knowledge is extremely basic.
A description of the connections between the devices:
The devices communicating over the RS232 link are an iMX6-based board and a device that is based on a Nordic nRF chip.  The RS232 link is not TTL level, it's level shifted to RS232 levels:
     +-------+                        +--------+
     | iMX6  | <====== rs232 ========>| Nordic |
     +-------+           ^            +--------+
                         |
                         |
                    +---------+
                    | DS Logic|
                    +---------+
                         |
                        usb
                         |
                    +---------+
                    | PC      |
                    +---------+

The devices are powered by:

iMX6:   a 12V DC brick
Nordic: a bench power supply at 9V
PC:     household main
DS Logic: a powered hub connected to the PC


texts:
The basic puzzle: how to conveniently view stepper motor current on a scope?

Edit 2014-04-14: More-sophisticated schematic and description.

I am building a test fixture to examine the behavior and parameters of small stepper motors and various inexpensive stepper driver ICs. The motors would be size NEMA 8 to 23, < 3A windings, bipolar. The drivers are Allegro A4988, commonly available mounted on a carrier with a standard pinout, such as Pololu A4988 Carrier, with related models of chip and carrier having different voltage and current specs.

I want to be able to display various voltages and currents conveniently; this question focuses on the winding current.

The schematic shows the basic idea: A stepper driver IC implements an H-bridge which can switch current to flow in either direction through a motor winding. There are two such bridges in a typical driver IC, to drive the two windings in a typical motor.

So, the "obvious" approach is to interpose a a sense resistor (here Rsense, say 0.1 ohm), across which to measure a voltage with a differential amp, providing a voltage to the scope. Example current-sense amps: Linear LT1999; Analog AD8216.

Problem:

Although the DC Common-Mode Rejection Ratio of such amps is adequate (100dB = 100,000) to avoid the 30V difference between low and high states from impinging much on the 0.1V/Amp sense voltage, there is almost definitely a problem with the AC CMRR.

The stepper ICs control the current using PWM, presenting pulses with durations as short as the low microseconds, and rise-times in the tenths of microseconds. To be clear: These pulses are distinct from the change of state when going from one step to the next, and are ongoing even when the stepper is held in a specific position (or micro-position).

So Vsense is in the range of 0 to 0.3V, on top of frequent common 0-30V pulses which we wish the differential amp to reject. Yet for current-sense amps that I've examined, CMRR drops off to about 60dB (=1000) at 1MHz, and 40dB (=100) at 10MHz. It seems that an amp with specs in this range is likely to produce quite a large unwanted output from the PWM pulses.

I've considered various ways to reduce the bandwidth of the two signals seen by the differential amp, but any imbalance in their frequency response, I suspect, for the PWM pulse edges, will precipitate a differential which will get amplified.

Question:

Is there some cleverer way out of this puzzle that manages to evade the problems noted above?

Answers that are less than ideal:

Some literature on stepper drivers advocates putting the current-sense resistor in the V+ leads of the upper FETS of the bridge (for example locations 'X' in the figure). This certainly avoids the AC CMRR issue. However, that location is not exposed in stepper drive ICs.
One could put a sense resistor at 'y' or 'G' in the figure, but this could not distinguish the two directions of current, and also sums together current for the two windings that an IC controls.
Though not brought out to the carrier board's pins, the A4988 Sense1 pin would afford connection to the voltage across sense resistor Rs1 (location z).  There is a separate Sense pin for each of the two windings, and the location avoids the CMRR problem. However, it still doesn't distinguish the winding current direction. Also, I had hoped to use the fixture with unmodified driver carrier boards, for easy interchange.
A proper scope current probe: Expensive, and hoping to build the current-viewing capability into the fixture.


texts: Low-noise amplification of microphone signals, tubes or chips?

texts: When trying to capture faint acoustic phenomena, are vacuum tube amplification designs superior to ICs? In this type of application sensitivity and low-noise amplification are the desired objectives. Should I be satisified with typical modern low-noise op amps, or if I want the best possible performance do I need to dredge up old books and plan for having a custom vacuum tube constructed?


texts: In practical terms what does the Prefix on ICs usually mean?

texts:
In this case I am  using 4538 retriggerable mono-multivibrators, i have bought them from all over and i have HEF14538 CD14538 MC14538's

Is this representing the different internal technologies used in the chips?
Does this make ANY difference for standard use?
Can I work of one datasheet for all of them!

They also end in BP BC  and BCP in that order.
Does this indicate the tolerance like in BC range transistors or the package type or something?

If anyone has a comprehensive "how to read components guide" or rule-of-thumb syntax I would appreciate a link as similar occurs with capacitors, transistors and other ICs.


texts: Supercapacitor bank charging process breaks down dc/dc converter

texts:
I'm an undergraduate student and I'm member of university's team, which deals with the development of an electric vehicle. One of our projects, is the implementation of a complete regenerative braking system. We have almost achieved that but there is a problem with our charging system. To be more specific let me tell you some basics about our system:

1) during decelaration of the vehicle, the 3-phase electric motor functions as generator and transforms kinetic into electric energy,

2) the ac of the motor (generator) passes through an ac/dc inverter that produces a dc output voltage with range 0 to 34 Volts,

3) that dc passes through a dc/dc converter (buck converter) which produces a fixed output of 15 Volts,

4) that dc/dc converter (buck converter) is used to charge a supercapacitor bank (156 Farads) with rated voltage 15 Volts.

You can see a graphical depiction of the topology in the following image. The green arrow shows the direction of the dc current that flows from the motor to supercapacitors via the ac/dc inverter and the dc/dc converter during charging process.

During laboratory tests, we increase gradualy the rpms of the motor (by using another motor) and then the charging system smoothly starts to charge the supercapacitor bank.

Unfortunately when we took our vehicle for a ride to test the regenerative braking system on a real deccelaration, the dc/dc converter (see the orange box in attached pdf) burned.

The difference, in relation to laboratory tests, is that during the real deccelaration, the vehicle is moving with a high speed and suddenly the charging switch (see attached pdf) turns on for the charging process. We think that at those moments (while the charging switch is turning on), instantly some dc current spikes are produced with result the disaster of the dc/dc converter.

We think that a solution to that could be the placement of a coil either at the input of dc/dc converter or at the output, so as to eliminate the spikes. Is our thought right or something else happens?


texts: How can I step this voltage source in "transient analysis" in LTspice?

texts:
I try to step a DC voltage source in transient analysis in LTspice.
Below there are five almost identical biased transistor circuits and plots for 1 sec duration. The only difference is that their DC bias is is increased from 500mV to 900mV with 100mV increments. So this DC bias is the DC voltage source in the question(V1, V2, V3, V4, V5). I know that such step is possible in DC analysis.

(left-click to zoom)

As you see above, to obtain those plots I had to create five circuits.

Is it possible to obtain the same plots above by using only one circuit and writing a SPICE command in LTspice?


texts:
Im begginer and currently Im trying to make DIY laser alarm (while laser is pointing at LDR sirene should remain silent and when laser is turned off, sirene should make sound). I found online following schema

As sirene Im using KPE212A
for transistor I have bc337-40
and LDR is VT43N1

Problem is that instead of sirene going on/off based on laser pointer, I get only change in pitch of sound (Sirene is constantly on, but only increases its volume while laser is pointing at LDR). Could you please advice what is wrong and how I could fix it ?


texts:
In the image below the circuit sometimes works perfectly, but sometimes the SDA and SCL lines appear to be pulled to a middle voltage value rather than Vcc and GND.

Also, this circuit works when using a digital multimeter to read the voltage values of SDA and SCL near the I2C master (downstream of a logic-level shifter) but stops working when it is removed.


texts: In my design (eagle cad) I have used BC548 PTH transistor. Now I want to change design to use SMD components. I am not getting BC548 SMD component while adding component in schematic (eagle cad).


texts: Will the DC offset of signal affect the slew rate in an op amp?

texts:
I'm curious if the DC offset of a signal going into an op amp will affect the slew rate.  Lets say you have an op amp configured to drive a 150 Ω load and is spec'ed to provided an output swing of ±3 V (say an AD829 or OP27).  If I drive the op amp with a signal that has a DC offset of 2.7 V (close but not at the limit of its range) will this affect the slew rate?  Here assume that the amplitude of the AC components are stay close or within the ±3 V.

I'm guessing the answer to this question will depend on whether the limiting factor is in the compensation or output driving stage of the op amp. I'm wondering if this is something that is known, that you shouldn't expect an op amp to provide its full slew rate unless its around the center point of its supply range or if it doesn't matter as long as you are within the output swing range.

I guess a good follow up question is whether it matters that you are starting with a DC offset that is positive or negative?


texts: What are the chances of failure if I drive a 34v device with 34.5v supply?

texts:
I have a power supply(DC) rated ~7.2A @ 34.5v. I am looking forward to drive an amplifier rated ~6A @ 34v(upper limit. actually 15 - 34VDC).

So my question is about the difference between supply and amp (0.5v excess). What are the chances that the difference(0.5v) is not tolerated and the amp is fried?

For me 0.5v difference is just ~1.5% higher then rated voltage, so assuming should be tolerable. But, since there is no datasheet available I could not confirm the same.

I could see similar question but for lower voltage like 4.5 vs 5 or 5 vs 6 or max was 12 vs 14.4 where the difference % of voltage is much higher then my scenario, so did not help much.

So, I would like your help to learn about your experience on similar scenario, you may have seen earlier. Or perhaps a theory for a possible outcome.

Extra Info:

Amp board: TDA7498 based chip (TDA7498 2*100w amp @ ebay)
Power supply: Salvaged from a broken Philips Sub-woofer
Power supply delivers exactly 34.5v under no load condition, I could not test it under load until now.

Options received until now:

Use diode to drop some volts(will research on the spec)
Do nothing, use as it is (last resort)
I have seen similar chip being rated for higher voltages as well (15-36v),
so assuming chip may tolerate the difference. Supports do nothing conclusion. Ref TDA7498E 2*160 amp @ ebay

Final

Added 2 6a diodes to drop around 1.2 volt (actual result -1.5v, net 33v)
Attached 2" of heat sink to control heat (looks ok, not very hot under load)
Added few caps(~3000uf) to stabilize voltage (was dropping to 15v under load)

Result is great, amp drives great. Thank you guys for the assistance.


texts:
I have to make a circuit in which i have to produce three outputs(on speaker buzzer sounds)

First is for 20 seconds on 5 sec off
10 sec on 5 sec off
5 sec  on and 5 off( this alarm sequence  for 3 minutes)
Second one is 5 second on 5 second off (this alarm for two minutes)
Third is 10 seconds on 5 sec off, 5 seconds on 5 seconds off (this alarm for 3 minutes)

I have to use 3 push buttons/switched for this.can anyone guide me how to use 555 ic for this.. I have resistor and capacitor values for times but i am not sure about circuit.


texts: How diffusion constant vary with temperature in Semiconductors?

texts:
Diffusion constant = Mobility*Thermal Voltage

            *Where,Thermal voltage = T/11600*

From above equation it is clear that Diffusion constant should increase with rise of temperature as it is Directly Proportional to Thermal voltage. On other hand    Mobility Decrease with rise of temperature because of high Kernel vibration with rise in temperature that will reduce Diffusion constant. I am not able to conclude Whether Diffusion constant should increase or decrease with temperature.


texts: What does the 1k resistor do in this schematic?

texts:
I'm very new to circuit design and have been doing lots of reading and research in order to understand everything going on in this schematic. I think I understand all of it except for the purpose of the 1k ohms resistor going from the control signal to the emitter.

Can someone explain what that does?

This circuit is part of a bigger project outlined here: http://victorbush.com/2015/01/arduino-rfid-door-strike/


texts: What is a good single conductor wire-to-wire connector?

texts:
I'm currently using 3-position JST connectors with two of the wires cut off, but this is unsatisfying. The 3 position JST is also bulkier than I'd like, and has lots of "barbs" and corners to catch on things, which is undesirable for my application (wearable electronics.)

The connector will be carrying signal at 5V, so the current requirements are low.


texts: Velocity limit of UMTS and (or) CDMA2000

texts:
If the client is moving relative to the base station, the Doppler shift would compress or extend the packet. If the effect is strong enough, the PN generator in the receiver will eventually get out of sync with the signal and the packet won't be received completely.

What relative speed can UMTS and (or) CMDA2000 tolerate?

Or is this somehow compensated for?


texts:
I am currently a Mechanical engineering student and I am trying to create a device that will balance two weights by moving the fulcrum between them. The whole thing looks like a see-saw with a motor and gyroscope attached, mostly because that's exactly what it is.

The problem I am having is getting the motor to move the board to place its center of mass above the motor in order to balance the load. The motor has a large gear on it that meshes with a linear gear across the bottom of the board. I am using an arduino mega to control a Spark motor controller using PWM. My first idea was to simply measure the angle from the gyro(between -4 and 4 degrees) and activate the motor whenever it did not read 0 degrees(level). This threw the board off of the motor. Later I decided that a PID loop would be a better solution. I wanted to have something like this video shows. https://www.youtube.com/watch?v=fusr9eTceEo
The problem is that as far as I know, PID only works in one direction. A gas pedal in a car is a good example because the PID loop can only give more or less gas and cannot hit the brake pedal. In my case I need two PID loops in order to control the position both left and right. Currently I am running the two loops side by side using the Arduino library with the angle as the input and the motor power as the output. I take the difference between the outputs and the resulting positive or negative value goes to the motor. I really don't think this is the right way to do this as I still cannot even balance the board itself. What do I need to do in order get the right motion?


texts:
I am working on a vhdl/fpga project using the vga module. I am trying to make an object fall with an acceleration (gravity). I found an answer on another problem, and it suggest to implement something similar to these equations:

Position_next <= Position_reg + timestep*Velocity_reg ;
Velocity_next <= Velocity_reg + timestep*Acceleration ;

Where timesetp in my case is the frame time, which is 1/60fps. The acceleration(gravity) is going to be a constant number. The result of the two equations are a floating point. Which is a problem, since the minimum step my object can take is 1 pixel per frame.
Any idea how to solve this problem.


texts: Is BeagleBone Black a microcontroller or computer?

texts:
I started working on BeagleBone Black, and I cannot find out whether BeagleBone is a microcontroller, or some kind of computer? If computer, what makes it a computer?

I worked on different Cortex-M microcontrollers, but I am not sure what BeagleBone really is.


texts: How to deal with non UL DCDC converters?

texts:
We have a product, and we're trying to get it MET marked for export from the UK to the US.  It uses an APD S10 converter [datasheet] to generate +-250V rails from a 12V supply. It's an isolated converter, but we're not using it as such, we've tied the negative input and the centre output together.

The relevant standard for our product is EN61010. Since the converter is not bridging an isolation barrier, I assumed that the only relevant part would be the flammability requirements.  APD can provide us with datasheets showing V0 flamability for the PCB and potting compound, and the whole thing is in a metal case, so that seemed sufficient.  And initially the test house agreed.

The test house has now changed their mind.  Apparently MET labs think the converter should be tested separately to EN 60950. This seems like a sensible choice of standard, but the converter does not have a UL number and has not been tested. The manufacturer says the norm is to just test it as part of a complete product, in the same way the rest of the circuit is tested. I realise we'd be better off with a UL recognised converter, but there aren't many at the right voltage and it's too late to change - we've already passed EMC tests with this one, and we need to ship ASAP.

What am I missing here? What is the norm?  APD is an American company, serving an American market, so there must be some way for them to sell these non-UL-recognised components for inclusion in a UL listed product.  But now MET seem to be telling our test house that that is not possible.  Yet APD are telling me that it happens all the time. I feel like I'm in the middle of a game of Chinese whispers, and want to understand the American system better.


texts:
I want to unambiguously refer to an assembled PCB that has been tested. I am familiar with the terms:

PCB - unpopulated printed circuit board
PCBA - PCB assembly, a PCB with all the parts fitted and soldered

Does anyone know a standard term for a PCBA that has been through test (assuming a single testing procedure)? I would probably refer to it as a tested PCBA (TPCBA) but this seems clumsy.


texts: In PCB DFM process; manufacturer have highlighted Gullwing Issue. What is Gullwing?

texts:
In PCB DFM process; manufacturer have highlighted Gullwing issue saying "Gullwing is not optimal robust SMT process.

What is "Gullwing"?


texts:
I am designing a custom PCB with ESP32 PICO MCU. I am going to use BLE peripheral mostly in my application. I have some questions regarding

Which type of Antenna should I choose for my application?
The flash memory of ESP32 PICO is 4MB according to the datasheet. My code size is not anyways going to exceed that memory size. So, can I skip integrating the external flash module or is it compulsory to have it?

Basically my application involves collecting data over I2C from an MPU6050 gyro sensor and transmitting those values through BLE. I must be able to read data using my terminal app in the phone. I am planning to use this ceramic antenna.

I have another doubt regarding the impedance matching circuit. The input impedance of the antenna is 50 Ω and the ESP32 PICO's impedance is also 50 Ω according to the datasheet. Can I remove the impedance matching circuit on my board or should I have it as the theoretical values might swing around a little bit?


texts: Converting DisplayPort to 24 bit RGB parallel. Possible?

texts:
Is it possible to interface a DP1.1 complaint source to a TFT Module that uses 24 bit RGB? I'm investigating the possibility of interfacing an Atom D2550 with This Display.

I have 3 options to connect the Atom to the display: displayport, HDMI or VGA.

Based on comments, displayport would be the most difficult one. I guess it's either HDMI/DVi for VGA.

Any ideas?


texts:
I have gone through Volatge multiplier circuits like, doubler ,tripler, quadrupler. And seem to understrand circuits like them shown in the figure.

With these in mind, I find it very difficult to apporach these circuits shown below. What are thing I have to keep in mind solving them? And I dont know how approach these power sources.


texts: Cheap solid equipment wire for breadboard from online shop?

texts:
I need breadboard wire for fast prototyping. It can apparently be 22AWG or 24AWG, acccording to this reply about stranded VS solid wire. Because it is for prototyping, I am not looking for expensive wires with excellent electrical shielding and such things -- just simple wires to plug into breadboard and reuse it fast: connect, reconnect, etc without getting them broken. Where do you get your solid experimenting wires?

Example

  Huge price differences: Farnell Finland 66.7EUR, Farnell UK CPC 23Pounds, cannot find in eBay or Dealextreme, nearly out of stock in CPC Farnell.


texts: Confusion with relating transmitter and receiver antenna size to carrier frequency

texts:
I have been wondering about this for long time.I see the AM transmitter antennas are quite tall. This is due to the fact that the wavelength of the AM carrier wave is not as short as a cellular communication's carrier wave.
At 1MHz the wavelength is 300m.

I also know that the AM radio receivers I encounter do not have that long antennas.
In a question in this site I remember one was writing that the receiving antenna size do not need to be half of the wave length to detect the radio signals. It could be much smaller. How much smaller I dont know.. A mystery.

So in antenna theory some texts relate the wavelength to antenna size. But when it comes to practice I see that wave length antenna size relation is followed by transmitter size but not at the receiver side.

I mean transmitter antenna size is more or less similar to carrier wavelength. But receiver antennas can be much much smaller..

If we can receive the AM radio signals by a realtively much smaller antennas, why then the AM transmitters also not short but very tall?
Is it possible to radiate AM modulated signals by a lets say 1m size antenna for a radio broadcast?


texts:
I want to use a 555 timer to generate a ramp to my soft starter. The problem is, I want it to be continuous after reaching it's value. Unlike this shown below,

Instead of discharging I want it to remain on. How can I adjust this basic 555 ramp generator circuit to do this?


texts: Calculate the Li-ion battery remaining capacity

texts: How can I calculate the remaining capacity (exact or approx value) of a Li-ion battery by measuring its voltage. The battery is connected the load and i know only the battery voltage and the value of current drawing from battery by the load. Is there any formula?


texts:
I have some codes like below. This is initialize stage and there is no problem here. Communication are OK.
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_I2S3_Init();
  MX_CAN1_Init();
  MX_I2C3_Init();
  /* USER CODE BEGIN 2 */
  USER_CAN_FilterConfig();
  USER_CAN_Start();
  DEVICE_TAS1_Init(hi2c3,DEVICE_TAS1);
  DEVICE_TAS2_Init(hi2c3,DEVICE_TAS2);
  PCT2075GVX_Init(&hi2c3, DEVICE_PTC);

After that, there is a function runs in my main.
 EngineSoundPlayer();
This function takes a constanst size of sound data from my soundsamplearray according to another data comes from CANBUS and send it via i2s.
HAL_I2S_Transmit_DMA(&hi2s3, SoundPack, SIZE);
After sending soundpack it takes volume parameters from CANbus and arranges amplifiers volume via I2C.

    if(SimRxData.SpeakerModeSelect== FRONT_REAR)
    {
        SetVolumeFR(TempVolume); //WARNING: CHECK MAX VAL.
    }
    else if(SimRxData.SpeakerModeSelect== RIGHT_LEFT)
    {
        SetVolumeRL(TempVolume);
    }

At this moment. After dma transmit function runs my i2c connection getting start to break and. I get bus busy error. If I comment dma transmit function, there is no problem at I2C.
I'm using I2C3 and I2S3.
This pictures belongs to SDA line, before and after i2S transmit dma fuction. At after, there are little bit noise over sda but seems not so much. This noise may cause adress mismatching ?


texts: Why are the pins on the official arduino motor shield so long?

texts:
Here is the Official Motor sheild website.

The shield has pin connectors at the bottom that are 2x longer than on any other shield I've seen. Why is that?


texts: Powering two 8-Ohm speakers in parallel with a 4-Ohm per channel audio amplifier

texts:
Are there any possible problems powering two 8-Ohm speakers in parallel with an audio amplifier designed to drive 4-Ohm per channel? (Both the speakers and amplifier are generic, and the speakers are identical). The amplifier's power rating is greater than the sum of the speakers, and would not be pushed beyond the combined power rating of the speakers. I can't think of  any reason for there to be any drop in audio quality, or for there to be any other issues, but I just wanted to do a sanity check by asking.

Thanks


texts: (n00b question) I have a small (6 cell regular bike) leadacid battery and want to charge it via solar sheet of 15V - 0.3A. the voltage solar sheet changes and in cloudy day goes below 10V. does the battery keep charging that those levels (though very slowly?)


texts:
I am designing the following circuit for my college quiz club.
I have replaced the bulbs BL1 to BL8 with suitable LEDs and resistors.
Now, the issue here is that given a 5V input (from a USB hub), the logic works fine, but the LEDs are very weakly lit and the buzzer doesn't produce any sound.  If I power it via a 9V battery, all the LEDs glow brightly and the switches S1 to S8 don't have any effect.
To fix this, I was thinking that the buzzer and the LEDs would need their separate power supply to be activated by some transistor based switch.
Is there any way that can be avoided?

Edit:
Here is the website I got the circuit from.


texts:
I'm currently working on a project which requires me to test the functionality of TTL logic gates by making use of diodes and resistors. To do so I must first place them on the breadboard and then calculate their voltage with an electronic tester.

However I lack the skills and knowledge required to accomplish the task, since I don't know how to set up a breadboard, therefore I'm not only asking for a scheme but also, possibly, for some pointers related to the subject, in order to gain some knowledge about it.

Breadboard layout question doesn't cover how breadboards are built from circuits since it lacks any sort of examples, and it doesn't address the main issue, which would be coming up with a scheme for the circuits.

The following are the circuits I must build on the breadboard:


texts: Failed to display on LCD when interfacing with PIC18F4520 using ASM language

texts:
The LCD constantly shows nothing even though I built program sucessfully and found no error. I tried for many times in the past days but it doesn't work.
I tried appling this code on PIC16F877 by replace some necessary instructions and it worked . Below is my code in assembly language:

  PROCESSOR PIC18F4520

#include <p18f4520.inc>

  CONFIG WDT=OFF
  CONFIG BOREN=OFF
  CONFIG OSC=HS
  CONFIG LVP=OFF

  CBLOCK 0x20
    COUNT, COUNT1, TEMP
  ENDC

#DEFINE RS  PORTD,0
#DEFINE RW  PORTD,1
#DEFINE E   PORTD,2

    ORG     0X000

MAIN:
    CLRF    PORTD
    CLRF    TRISD
    CALL    INIT_LCD
    MOVLW   'D'
    CALL    SEND_DATA
    GOTO    $

INIT_LCD:
    MOVLW   0X20
    CALL    SEND_CMD
    MOVLW   0X28
    CALL    SEND_CMD
    MOVLW   0X0E
    CALL    SEND_CMD
    MOVLW   0X06
    CALL    SEND_CMD
    MOVLW   0X01
    CALL    SEND_CMD
    RETURN

SEND_CMD:
    MOVWF   TEMP
    ANDLW   0XF0
    MOVWF   PORTD
    BCF     RS
    CALL    ALLOW
    SWAPF   TEMP,0
    ANDLW   0XF0
    MOVWF   PORTD
    BCF     RS
    CALL    ALLOW
    CALL    DELAY
    RETURN

ALLOW:
    BSF     E
    NOP
    BCF     E
    RETURN

SEND_DATA:
    MOVWF   TEMP
    ANDWF   0XF0
    MOVWF   PORTD
    BSF     RS
    CALL    ALLOW
    SWAPF   TEMP,0
    ANDWF   0XF0
    MOVWF   PORTD
    BSF     RS
    CALL    ALLOW
    CALL    DELAY
    RETURN

DELAY:
    MOVLW   0XFF
    MOVWF   COUNT

DEL:
    MOVLW   0XFF
    MOVWF   COUNT1
DEC:
    DECF    COUNT1,1
    BNZ     DEC
    DECFSZ  COUNT,1
    GOTO    DEL
    RETURN

    END

The hardward connection simulated on Proteus is below:


texts: sine wave generator circuit with OPA604 and LM3900

texts:
I am trying to generate a sine wave signal. I am following this guide http://www.ti.com/lit/ml/sloa087/sloa087.pdf from TI. The thing is I cannot find the IC that they are using (TLV2471) and I only have OPA604 and LM3900 op-amp and the circuit doesn't work. I have tried the Wien Bridge from page 12 and phase shift oscillator from page 17.

For the Wien Bridge circuit, the OPA604 give very small amplitude sine wave (from about 2.3 to 2.7V) and the frequency reading in my oscilloscope jungling around from 50kHz to 40Mhz. the LM3900 give a nearly square wave at about 5kHz.

For the phase shift oscillator circuit, the OPA604 gives a similar small sine wave with jumping frequency while the LM3900 gives no oscillation, the ouput just stay at about 2.5V.

So could anyone please help. Any pointing is also greatly appreciated.


texts:
I've been trying to get this simple FM transmitter to work over the past few days and I could use some help in a few areas.

First iteration was on a breadboard with all parts included.  The exception being I didn't have a 0.1uH coil handy but I had another coil rated at 0.7uH (using my LCR meter).  I also didn't have a C4 value of 4.7pF but I had a 10pF value.  I figured I could just tune it later.  I hooked a scope up to it and got no oscillation.  I tried connecting the probe to the gate and the collector separately and together.  Still no oscillation.

Second iteration.  I removed the audio component of the circuit.  Essentially everything to the left of C2.  I had gotten that working no problem anyway so I figured I would concentrate on the oscillator.  This time I tried different values for the inductor ranging from 20uH to 1mH and different fixed values for the variable cap (10pf, 20pf, 30pf).  These were all ceramic caps. No love.

Third iteration. I tested the transistor to make sure that wasn't the issue.  Seems fine.  PN2222A variety. (Also tried 2N3904 and BC547). I then modeled this up on a piece of perf board.  I even found a SMD inductor of 0.1uH so now I thought I would be good.  Tested all the pieces on the meter before installation. Still nothing. I'm not seeing anything on the spectrum analyzer either.

Questions:

Do you think my benchtop power supply is causing a problem?  All the various versions of this type of FM transmitter circuit on YouTube and the Internet all seem to use a battery.  Any chance the 60Hz main power is messing with things?  I've put .1uF and higher caps on the power rails.
I have a 200Mhz SIGLENT SDS1202X-E scope.  I've built and tested other oscillators up to a few MHz before with no issues.  Any thoughts on that being the issue?
I would expect to see something on the scope right? Any chance the probe is dampening the oscillations?

I know there are a lot better FM transmitter circuits out there I was just experimenting with this (and others like it) and couldn't get any to work.


texts: Is there a way to construct a PLL cicruit which locks on to an input signal's phase but provides an output signal with different duty cycles?


texts:
Back when I was a kid, car batteries used to be huge heavy lumps of plastic filled with lead and acid. They used to weigh almost as much as a mobile phone (slight exaggeration there, sorry).

45 years later, car batteries still look the same and weigh the same.

So, in this modern age and emphasis on fuel economy, why do batteries still weigh 40 lb? Why have advances in technology not been able to make them lighter and more efficient?


texts: Circuit requirements for 'fixed' output switching regulator

texts:
I am considering using one of these switching regulators in a circuit:

TPS560430YFDBVR ( output type PWM )
TPS560430X3FDBVT ( output type 'fixed' )

The datasheet for both are the same thing:
http://www.ti.com/lit/ds/symlink/tps560430.pdf

The datasheet gives this example of a simplified schematic:

The feedback voltage divider RFBB /  RFBT can be used to adjust the desired output voltage.

The datasheet also says "Fixed 3.3-V Output Option". Presumably with a non-adjustable output the voltage divider is not necessary, so the circuit would be somewhat different. However I can't find any mention of how it should be arranged.

Should FB connect directly to VOUT in this case?


texts: GND plane close to LVDS differential pair?

texts:
I have two LVDS differential pairs on my PCB, running from a connector. On the connector, I have the following sequence of nets:

GND
LVDS+
LVDS-
GND
LVDS+
LVDS-
GND

This is as I have seen suggested:

So the GNDs pins are very close to the LVDS pins. However, advice I have seen regarding LVDS PCB layouts suggests that I should keep some clearance between the LVDS tracks and anything else, including the GND plane. This seem to be conflicting advice.

What's the best way to lay out the LVDS tracks running from my connector?

Continue the GND plane close to the track as it is on the connector? Or leave clearance and risk an impedance change?

Added: There is also an unbroken ground plane underneath the differential pairs.


texts: Bidirectional solid state switch for solenoid

texts:
I'm building a circuit to control a flip dot display, which is basically a matrix of solenoids which you control with bidirectional current across the 25 columns and 7 rows of the board.

The attached schematic shows the circuit so far - I'm using a bank of H-Bridges to control the columns, and they switch polarity depending whether I want to flip a particular dot one way or the other.

The challenge comes with controlling the rows, at the bottom of the image. If I'm targeting a particular row, the positive voltage has to go down one path, and the negative down another. So I imagine I'm looking for a bidirectional DC solid state switch that can handle a peak of about .5A.

Any suggestions on how I should implement that part of the circuit? Electromechanical relays are not good because these switches will be used thousands of times a day (in a clock). I also need to be able to handle up to 0.5A.

Edit: I've added a more accurate schematic for the flip dot board (25 columns, 7 rows)

update:

Thanks to all the ideas folks contributed to help me solve the problem. I finally finished the flip-dot clock project - you can check it out at http://www.dhenshaw.com/dottie

If there's interest I'll post a schematic of what I built (I'd also have to draw it first!)


texts: Why is transistor needed when using a relay?

texts:
I will start building a relay based on this answer:

https://electronics.stackexchange.com/a/464345/56969

Why is T1 needed? Every other component has an important purpose. But does T1 has an important purpose as well? Can I just remove it?

What would happen if I remove that transistor?

Edit

I know Arduino cannot supply more than 40mA on each pin and that is the reason why there is a separate power supply to turn on the relay. I guess my question should have been "Can the optocoupler supply 100mA of current?" If so, that means I can remove the transistor and have fewer components.


texts:
How can a GPS device give exact timing even when the number of available satellites are zero?

I'm monitoring GPS data using VisualGPS.


texts:
I have constructed an Audio Amplifier using TDA 2050 single supply but I am having difficulty understanding the circuit.

It contains the TDA 2050, (32W hifi audio Amplifier) with Vs = +15 V.

Can anyone please help explain the detailed functionality of this circuit, such as

1- Why do we need voltage divider (R1 and R2)? Can't we use direct Vs as +7.5 V and remove R1?

2- How do we calculate its gain ? (I got around 33, is that right?)

3- How do we calculate its cut-off frequency? (upper and lower)? (I got 3.2883 Hz?)

4- Why there are different types of capacitors?

5- Can we change non-electrolytic with electrolytic capacitors and vice versa?

7- What is the purpose of C1, C2, C3, C4, C5, C6 and C7?

8- What happens if we remove C4 ?

9- What happens if we remove C6 ?

10- Do we need to change the capacitance of capacitors if we increase/decrease Vs?

11- What is the main purpose of C5? We used that capacitor in breadboard but not in PCB.