texts: Constant current source for an alternating magnetic field of varying frequency and constant amplitude from a solenoid

texts:
The project I am working on requires me to oscillate my sensor. I am doing this by coating a ferromagnetic material on the sensor and applying a sinusoidally varying magnetic field. I was applying the magnetic field using a solenoid and driving it using a sinusoidal wave from the function generator. The function generator was giving me a maximum of 3.33Vpp after setting 10Ohms load. I was getting enough oscillation amplitude from the setup, but I also wanted to take the frequency response of the sensor.

On increasing the frequency of drive signal from the function generator, the current in the solenoid is decreasing, which reduces the magnetic field and I am not able to get enough oscillation amplitude. To measure the frequency response I want the magnetic force to be constant throughout the sweep, but it is decreasing with increasing frequency.

I looked into designing some operational transconductance amplifiers, but couldn't find something that could give me a constant alternating current source (most of it was for DC). I also found some stuff about Howland current pump, but they say it isn't suited for reactive loads. I also looked into audio amplifiers for this purpose (since I have a very cheap guitar amplifier I can sacrifice :-D ). But I am not sure if the audio amplifier can work as a constant current source.

Experimental details:

L = 3.387mH
R = 12Ohms
Z = 24.54 ohms at 1kHz & 211.9 ohms at 10kHz
Maximum Magnetic field requirement is 40 Gauss which I get from around 150mA current in the solenoid.
range in which i want to find out the frequency response is upto 20Khz

Any help and suggestions will be greatly appreciated! Cheers


texts: Why does a motor not work after the power supply?

texts:
I have a fairly cheap breadboard power supply and a motor.

Now if I touch the wires from the adaptor (the thing that plugs into the power supply to provide it with electricity) the motor works fine and spins happily. I can adjust the voltage of this adapter to 3 volts - 12 volts, and the motor spins fine at all voltages. So I know the motor is working fine.

However if I plug the adaptor into the power supply and then try and power the motor from the power supply, it doesn't work. I try with both the 5 volt and 3 volt output of the supply. In fact the power supply appears to shut down - the led on it turns off.

What gives, why can this power supply not drive the motor? Is it just broken or is there some law of electricity I am not yet aware of (likely)?

EDIT

Ok, so this is the motor I have : motor

And the power supply I have is something similar this : power

I can't find many details about the motor. But I have noticed for the power supply it says :

  Maximum output current: <700 mA;

So I am guessing this is the problem? The motor likely needs more than that, especially if it needs 10x its requirement to get going.


texts:
I have a device, Neptune Apex, that has programmatically controlled 24VDC outputs.

Using the 24V I would like to trigger a relay that is built into another component, that has the specs of: 3-12VDC, 3-30mA.

Since the current draw is very minimal and will be constant, what would be the cheapest and easiest way to reduce the 24VDC to 12V to trigger the relay?

I don't really want to have to purchase and introduce another component like a buck converter, so could I do this with a voltage-divider or some other simple components and not burn anything up?

Update:

The 3-12VDC device is a Power Switch Tail II (http://powerswitchtail.com) and it it does appear to use a opto-isolated relay.

Does this help to nail down the best solution?


texts:
I am reading this App Note. On page 6, Figure 5, they have provided a circuit which helps with the soft start and input protection circuitry.

I am not able to understand the "Capacitor Reset" block on the bottom right. They have mentioned that when there is a power disconnection, the capacitor reset blocks helps to reset the RC time constants of the 1uF and 332k resistor & the 0.1uF and the 10.2K resistor.
I am not able to understand as to how the current or the charge from the capacitor will flow to the ground through those diodes. Can someone help me with the capacitor voltage polarities and the direction of the current flow of those 2 RC sections during that power disconnection?
I have seen diodes placed in parallel to the resistors on microcontroller circuits so that when a power cycle happens, the capacitor is discharged through the diode instead of the resistor so as to provide an indication that there was a power interruption. But I am not able to understand the current flow over here.
Please help to understand.


texts: At which set point (frequency) will a VFD dissipate the most heat?

texts: On a typical application for a variable speed centrifugal pump, at which percentage speed setting will the VFD dissipate the most heat, in other words have the highest losses?


texts: How to connect LCD display to a potentiometer?

texts:
I am new in electronic therefore please bear with me about my explaination.

I have a LCD display made by TGK model TM12864L, please see manual and diagram attached.
https://dl.dropboxusercontent.com/u/71681740/TM12864L-1-TGK-manual.pdf

It requires a potentiometer connect to pin 3 and pin 18 of the LCD.

pin 3 is Vo ( operating voltage )
pin 18 is Vout ( negative voltage output )

The potentiometer diagram shows: Vo connects to the middle wiper, Vdd and Vout connect to the other 2 legs.

The manual also indicates: Vlcd - Vo = - 4.7 Volt

I am really confused which leg of the potentiometer should connect to pin 3 and pin 18 and where the other leg should connect to ?

Many thanks for your help.


texts: Why is "trimming" a carbon compositon resistor not possible?

texts: I read that carbon composition resistor can't be trimmed and thats a big reason why the tolerances for them are so high. What I don't understand is why I can't just carefully cut some of the resistive material out to increase the resistance value.


texts: HDMI Receiver Sense Logic and TMDS Capacitor Coupling

texts:
Does anybody know how is the "receiver sense" logic done?

As the datasheet for Sil9612 4K video processor puts it in section 2.13.8 "receiver sense and hot plug detection": it is "by sensing the termination in the attached device". How exactly the termination is sensed?

The HDCP specification explained the use of HPD (hot-plug detection) and RSEN (receiver sense): When HPD is high, the source reads EDID through I2C from the sink. Then when the RSEN goes high, the source turns on the TMDS signal in an appropriate format.

Now we have a board that uses 100n capacitors on each of the TMDS lines to make an AC coupling of the signal. Would that be a problem to this receiver sensing?


texts: Is there such a thing as a wireless solid state relay

texts:
I want to control multiple baseboard heaters in my house, but I don't want to put a raspberry pi connected to a solid state relay behind each baseboard heater, or even connect it to the thermostat, as the raspi is rather large and it requires a clunky power adapter. Is there a wireless/bluetooth/RF solid state relay which also gets powered by the AC line (208V)? I will have sensors all over the house, I just want to be able to send an ON or OFF signal to these solid state relays without having to have miles of cabling

EDIT:
I essentially want to build something like this product, but connecting to the baseboard using wires rather then an electric outlet, and being able to communicate to it through a computer. Also, I don't believe these guys need any other power source (ie. batteries)


texts: How can I charge 3 12V batteries with 2 24V solar panels?

texts:
I use three 65Ah/12V VRLA batteries connected in series to a 36V UPS to power my computer. I will soon have two 200W/24V solar panels. What do I need to charge the UPS batteries with these panels? It's not clear to me if normal charge controllers can handle this situation, and I've received conflicting answers from the dealers I've consulted.

In the long term, my plan is to get a solar inverter and four larger batteries, but right now I'm looking for a stopgap that allows me to reuse my existing batteries and UPS for a while longer.


texts:
I've got a variable pulse wave (that looks like a square wave) ranging from 5Hz to 60Hz.

The peak voltage is 5V. I'm trying to design a low pass filter that effectively gives the average voltage as a DC output but am struggling to get an acceptably flat output, it currently fluctuates 0.5V. I've got 100n and 470n capacitors on hand so they are ideally the values I'd like to use. Can also run through up to 4 op amps filters if that would improve the result.


texts: UART give garbage values after waking up from sleep(arduino)

texts:
I've made a arduino clone which has a PIR sensor, I intend to run it on 2AA, I'm using LT1302 boost converter, because the PIR sensor works at 5V, if motion is detected the message will be sent to my website using cc3000 breakout board from adafruit. All is working, but now I'm adding the sleep code block to save power, for testing purpose I've written the following code.

#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/wdt.h>

//PIR sensor,led and disconnect button
#define PIR 2  //INT 0 PIN 4
#define DISCONNECT 19//A5 pulled up, not used for now
#define LED 16 //A2 high on

volatile int pirState = LOW;             // we start, assuming no motion detected
volatile char sleep;
int val = 0;                    // variable for reading the pin status

void static inline pwrDown(void);

void setup() {
  ADCSRA = 0; //Disable ADC
  // turn off various modules
  //PRR =0x81; //0b10000001; TWI and ADC off
  // 7  1     0
  //TWI uart  ADC
  pinMode(LED, OUTPUT);      // declare LED as output
  pinMode(PIR, INPUT);     // declare sensor as input
  Serial.begin(9600);
  attachInterrupt(0, motion, RISING);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep = 1;
  //  cli();
  //  pwrDown();
}

void loop(){
  delay(500);
  Serial.println(pirState);
  digitalWrite(LED,pirState);
  cli();
  pwrDown();
}

//ISR for INT0
void motion() {
  pirState = !pirState;

}
void static inline pwrDown(void)
{
  //PRR =0xFF; //turn off all modules
  MCUCR = MCUCR | bit(BODSE) | bit(BODS); //timed sequence
  MCUCR = MCUCR & ~bit(BODSE) | bit(BODS);//to turn off BOD in sleep
  sei(); //enable int
  sleep_mode(); //sleeping set SE got sleep and clear SE when waking up
  //sleep_enable(); //slee_mode() does all three.
  //sleep_cpu();
  //sleep_disable();
  // PRR =0x81; //0b10000011; turn off all except uart and spi
  //  sleep = 0;
}

This working, the LED is lighting on and off as its supposed to, the loop is not running continuously means the AVR is going in power down mode , but for Serial.println  I'm getting garbage value. eg j for 1 and Lc for 0


texts: HAL_CAN_Transmit_IT and HAL_CAN_Receive_IT simultaneously use problem

texts:
Synopsis: STM32 HAL Library functions HAL_CAN_Transmit_IT and HAL_CAN_Receive_IT can't be used simultaneously effectively without data loss risks.

Details:

When you build a receive/transmit cycle like below (simplified)

main() {
  HAL_CAN_Receive_IT();
  HAL_CAN_Transmit_IT();
}

HAL_CAN_RxCpltCallback() {
  HAL_CAN_Receive_IT(); // Rearm receive
}

HAL_CAN_TxCpltCallback() {
  HAL_CAN_Transmit_IT(); // Rearm transmit
}

In some situations HAL_CAN_Receive_IT/HAL_CAN_Transmit_IT drops with a busy state. This occurs because both of Transmit & Receive uses a lock via __HAL_LOCK(hcan).

When you call HAL_CAN_Transmit_IT and interrupt HAL_CAN_RxCpltCallback occurs, the state is locked by HAL_CAN_Transmit_IT and rearm rx fails.

What is the solution to solve this?

I can't find an easy way now. In my opinion, a general mistake is the unified HAL_CAN_StateTypeDef State used for three independent flags - General CAN state, rx state, and tx state.

I think the solution is to split State for {State, rxState & txState} and never lock the same thing in both of Receive/Transmit.

For example, the current structure,

typedef enum
{
  HAL_CAN_STATE_RESET             = 0x00,  /*!< CAN not yet initialized or disabled */
  HAL_CAN_STATE_READY             = 0x01,  /*!< CAN initialized and ready for use   */
  HAL_CAN_STATE_BUSY              = 0x02,  /*!< CAN process is ongoing              */
  HAL_CAN_STATE_BUSY_TX           = 0x12,  /*!< CAN process is ongoing              */
  HAL_CAN_STATE_BUSY_RX           = 0x22,  /*!< CAN process is ongoing              */
  HAL_CAN_STATE_BUSY_TX_RX        = 0x32,  /*!< CAN process is ongoing              */
  HAL_CAN_STATE_TIMEOUT           = 0x03,  /*!< CAN in Timeout state                */
  HAL_CAN_STATE_ERROR             = 0x04   /*!< CAN error state                     */
}HAL_CAN_StateTypeDef;

typedef struct
{
  ...
  __IO HAL_CAN_StateTypeDef   State;      /*!< CAN communication state        */
  ...
}CAN_HandleTypeDef;

split to

typedef enum
{
  HAL_CAN_STATE_RESET             = 0x00,  /*!< CAN not yet initialized or disabled */
  HAL_CAN_STATE_READY             = 0x01,  /*!< CAN initialized and ready for use   */
  HAL_CAN_STATE_BUSY              = 0x02,  /*!< CAN process is ongoing              */

}HAL_CAN_StateTypeDef;

typedef enum
{
  HAL_CAN_TXRX_STATE_READY             = 0x01,
  HAL_CAN_TXRX_STATE_BUSY              = 0x02,
  HAL_CAN_TXRX_STATE_TIMEOUT           = 0x03,
  HAL_CAN_TXRX_STATE_ERROR             = 0x04
}HAL_CAN_TxRxStateTypeDef;

typedef struct
{
  ...
  __IO HAL_CAN_StateTypeDef     State;      /*!< CAN communication state        */
  __IO HAL_CAN_TxRxStateTypeDef RxState;    /*!< CAN RX communication state        */
  __IO HAL_CAN_TxRxStateTypeDef TxState;    /*!< CAN TX communication state        */
  ...
}CAN_HandleTypeDef;

But that is an awesome library modification. Maybe there exists a better solution?
The same problem affects the USART library, I think.


texts: With today's technology, is it possible to charge a battery over 100% without exploding?

texts:
We all know who Iron Man is.

Hollywood makes a nice job to make him look like a genious in electronic.

However, there is a scene where his suit charges it's batteries to 475%.

There is another question, on another website, adressing one part of this issue.
You can read it on Can Iron Man recharge his suit from lightning?.

What I'm asking here is if it is possible to charge a battery (no sci-fi stuff, please), with current technoligy, to over 100% of it's charge without exploding?


texts: How is a one-hot code called, if zero is acepted, too?

texts:
All know the one-hot code (aka. 1-out-of-N code).

This strict code has exact one One in each binary word. But what if I allow also zero Ones?

A 4-bit onehot example:

0 -> 0001
1 -> 0010
2 -> 0100
3 -> 1000

Is there a name for the following code?

0 -> 0000
1 -> 0001
2 -> 0010
3 -> 0100
4 -> 1000

(I hope it's on-topic at EE.SE)


texts: LCD 16x4 is shifting the columns of the third and fourth lines

texts:
I'm using the PIC 18F4550 to write to an LCD 16x4. I used MikroC Pro for PIC to write the code  and the Proteus to simulate.
      I'm using the library Lcd and Lcd_Constants already present on the MikroC Pro for PIC. I'm just modifying a pre existed code that was originally designed for a 20x4 LCD, but I didn't find any declaration about the type of the LCD (16x4 or 20x4 ) in the code. As a example I tried to wrote the following messages:

  Lcd_Chr(1,1,'F');
  Lcd_Chr_Cp ('I');
  Lcd_Chr_Cp ('R');
  Lcd_Chr_Cp ('S');
  Lcd_Chr_Cp ('T');
  Lcd_Chr_Cp (' ');
  Lcd_Chr_Cp ('L');
  Lcd_Chr_Cp ('I');
  Lcd_Chr_Cp ('N');
  Lcd_Chr_Cp ('E');

  Lcd_Chr(2,2,'S');
  Lcd_Chr_Cp ('E');
  Lcd_Chr_Cp ('C');
  Lcd_Chr_Cp ('O');
  Lcd_Chr_Cp ('N');
  Lcd_Chr_Cp ('D');
  Lcd_Chr_Cp (' ');
  Lcd_Chr_Cp ('L');
  Lcd_Chr_Cp ('I');
  Lcd_Chr_Cp ('N');
  Lcd_Chr_Cp ('E');

  Lcd_Chr(3,2,'T');
  Lcd_Chr_Cp ('H');
  Lcd_Chr_Cp ('I');
  Lcd_Chr_Cp ('R');
  Lcd_Chr_Cp ('D');
  Lcd_Chr_Cp (' ');
  Lcd_Chr_Cp ('L');
  Lcd_Chr_Cp ('I);
  Lcd_Chr_Cp ('N');
  Lcd_Chr_Cp ('E');

  Lcd_Chr(4,2,'F');
  Lcd_Chr_Cp ('O');
  Lcd_Chr_Cp ('U');
  Lcd_Chr_Cp ('R');
  Lcd_Chr_Cp ('T');
  Lcd_Chr_Cp ('H');
  Lcd_Chr_Cp (' ');
  Lcd_Chr_Cp ('L');
  Lcd_Chr_Cp ('I');
  Lcd_Chr_Cp ('N');
  Lcd_Chr_Cp ('E');

But, in the simulation, appeared the third and fourth lines shifted by 6 columns positions. So, does someone know why it is happening ? Below is a print of a part of the schematics and simulation:

[EDITED]

I programmed a device here and the same happened. I think that, probably, the problem is on the library.

I did the following modification of th code above:

  Lcd_Out(1, 1, "First Line");
  Lcd_Out(2, 2, "second Line");
  Lcd_Out(3, -2, "Third Line");
  Lcd_Out(4, -2, "Fourth Line");

It worked. Is not a elegant way, but worked. I needed to shift the column number negatively.


texts: Three output voltages not adding up to input voltage – how?

texts:
I have a 12 V power supply that connects into a custom made power board that then has three 5 V outputs. There are three things connected to it's working all the time.

How does that work, because 3 x 5 is 15 not 12?


texts:
I'm building a kit car with a bike engine and want to strip down the original bike wiring loom as much as possible.

I'm trying to work out how the junction box that controls the starter motor works.

It has a relay that supplies 12v to the starter when the starter button is pressed. but only in certain circumstances.

Starter lockout pin is earthed
Side stand pin is earthed
Neutral pin is earthed
starter button is pressed

The starter button is obvious, I understand how a relay works, and the basics of diodes. But I cant understand how the three diodes in parallel affect the relay latching?

I'm planning on removing the junction box completely, and supplying the starter with 12v directly from the key/starter button.

The only part I'm worried about is the igniter pin. Igniter is basically the ECU. I cant tell if I need to supply the igniter pin with 12v, ground it or just disconnect it completely?

full wiring diagram for ZX1100-D1, D2 (originally posted here)


texts: Powering a custom Arduino compatible - 5V regulator or no 5V regulator?

texts:
I'm building a custom Arduino compatible with an ATMEGA328P.

Would it be better to get a 5V power supply that plugs into the wall to power the project and gives me a barrel jack, then connect that directly to the uC, or should I instead use something like a 9V power supply, then use a 7805 to regulate down to 5V?


texts: How to estimate settling time of an overdamped system?

texts:
I've been trying to figure out how to estimate the settling time of a second order system in response to a step input of magnitude 5.
The systems transfer function is $$G(s) = \frac{1}{(s+2)(s+4)}$$ and I have already determined the time response with the step input R(s): $$C(s)=R(s)G(s)\qquad \therefore c(t) = \frac{5}{8}+\frac{5}{8}e^{-4t}-\frac{5}{4}e^{-2t}$$
Now I need to estimate the 2% settling time of the response using this information, but I'm not sure how. I know the system is overdamped as ζ>1, so I can't use the normal settling time equation $$T_s =\frac{4}{\zeta\omega_n}$$
I looked into this post: (over and critically damped systems settling time) but the answers only explain long winded ways to get an accurate result. I've already used MATLAB to obtain an exact result of 2.3 seconds, but I need to be able to estimate it without MATLAB.
I was thinking I could try trial and error with different values of t until c(t) is within 2% of the steady state value (which is 0.625) but while this would work I doubt its the correct way to do it, so is anyone able to help me out with a better method?


texts: What hardware limitations limit the number of stations connected to and access point chip?

texts:
I am designing a Linux based embedded access point that needs to support as many connected stations as possible.

I understand the first limiting factors like CPU, RAM, and available bandwidth.
https://serverfault.com/questions/192905/whats-the-maximum-number-of-wifi-connections-for-a-single-wifi-router

I also imagine there are limitations, hardcoded or otherwise, on the driver side of things.

What I would like to understand is what will be the limiting factors in the radio hardware? When comparing the features and specifications on Broadcom, Qualcomm, NXP, and other chipset makers, what will limit the number of stations outside of the above?


texts: How to properly connect a crystal to a Network Analyzer?

texts:
What is the correct way to connect a crystal or ceramic resonator to a network analyzer so as to be able to measure the series and parallel resonate frequencies?

Should non-attenuated probes be used? Assuming that the input and output of the analyzer is 50ohms, can the crystal be connected as follows?

simulate this circuit – Schematic created using CircuitLab

If the Analyzer has a high-impedance input or if I were to manually plot this with a signal generator and an oscilloscope, should there be a 50ohm resistor between the right side of the crystal and ground?

The series and parallel resonant frequencies will be used to calculate the motional perimeters (Lm and Cm) of the crystal.

This appears to be a new question. I searched here and Google.


texts: Response of a first-order filter to a step input

texts:
I've been asked to estimate the half-power cut off frequency of the filter and sketch the frequency and phase response.

I think the 63% mark is around 1.9 usecs and I need to use the equation f=1/2pit

Is this correct? Any help or workings are much appreciated.


texts: Converting Altium STP/STL model into solidwork

texts:
I need my STP/STL model to be re-captured in the 3D workspace environment from Altium to SolidWorks.

Can any one help me on this and can it indeed be done?
Norman


texts:
I'm trying to make a stationary remote control that doesn't have to move. Basically I need to use a high intensity IR LED (I think). I'm assuming if the LED is not facing the TV etc. it will bounce around the room more effectively if its more intense. However, I'm a little worried after reading the datasheet for SFH 4550. It says:

"Depending on the mode of operation, these devices
emit highly concentrated non visible infrared light
which can be hazardous to the human eye"

Do I actually need to be worried about eye damage? Is there a way to avoid it causing damage (a filter over the LED?)


texts: My laptop uses a standard clover-leaf 240v 3A UK power lead. I bought a "laptop power lead" for use in Europe. However, it seems to be rated for 16A, is this normal or is it overkill for use with my laptop?


texts: Many lamps are supplied by 220v and a circuit breaker through a PCB as in the picture. The total current of this circuit is 1A. For this implemintation I am going to use 2A circuit breaker. I am afraid that a short circuit could happen at the load and the traces of the PCB may explode. How can I determine the safe width of the PCB traces so that they withstand the momentary short circuit current before the circuit breaker trips? Any tips would be appreciated.


texts: Can I find the loss tangent of a substrate if I know the thickness of substrate and its relative permittivity?

texts: What is the formula to calculate loss tangent for a substrate with relative permittivity 4.4 and height 1.58 mm? I need the value for designing a PIFA with 35-micron copper ground conductor.


texts: How I can read optical encoder pulses on High RPM

texts:
I am working on a project in which I am using two DC motors with encoder but after certain speed ( my DC motor operating voltage is 24 V but when I give it more than 15V )my MCU CC1350  start missing encoder pulses. I don’t want replace my MCU for now is their any alternative to read the pulses A , B with accuracy
I am using interrupt (Rising)
MCU Cc1350
Encoder datasheet
Motor datasheet


texts:
The germanium transistor era was long over in the west when the Berlin wall came down.

Nowadays, new old stock Russian germanium transistors are appearing on world markets.

Some musicians prefer germanium transistors due to their more gradual characteristics for applications like fuzz boxes.

Did the Russians persist with germanium for longer than the west? Is there anything different about the Russian devices that would make them better?


texts: Receiving input from RS232 and reading it with Arduino board

texts:
Let me begin by stating that I don't have much experience in hardware-related projects.

I need to obtain info from a machine that outputs its data from an RS232 cable.
http://i.imgur.com/fkqnf.png

My goal is to then take this data and send it to a server. I thereby plan on using an Arduino Uno Board, attached with the Arduino Ethernet board, and write a looping program that will send the data every few seconds.

What device should I use to collect the information from the machine? Can I simply use an RS232 to USB converter and plug it directly on the UNO board, or are there RS232 boards for this?

And finally, are there better alternatives to my current problem?

I'll gladly clarify anything that is not clear enough, thanks.


texts:
One of my microcontroller projects requires dual outputs, 5V and 3.3V.

Instead of using a dedicated LDO for 3.3V, can a zener get the job done efficiently? Wouldn't that be easier and equally stable?

Any reason to stick with an LDO?

Thanks.
Just so you know, current required for both voltages is 200ma.
Supply voltage from USB or 3.7V battery with boost.


texts: Choosing Fuses or MCB in 24VDC vehicle circuit

texts:
I am currently designing a 24VDC circuit for a small vehicle. I personally prefer using MCB's since they are simple to reset and easy to detect faults in the system, although i do find it rather hard to calculate the correct size and type of MCB for the circuit due to its changing characteristics compared to normal AC circuits.

So it opens up a few questions on this matter:

If i use MCB, how do i handle a short-circuit if the battery is unable to supply enough current to break (eg. under-voltage guard?)?
Should i forget all about AC/DC MCB's and use normal fuses instead?
What is the best practice when calculating MCB for DC circuits, in means of size and type?

Since i have a very restricted budget, pure DC MCB's or electronic fuses are pretty much out of the picture (unfortunately).


texts: Can someone help me figure out what resistor to wire to this LED for maximum brightness?

texts: I know that you're supposed to wire a resistor with an LED to stop it from being damaged, but I don't know how resistant a resistor to put in. My input voltage will be from a 3.7V Li-Ion battery. The LED says it's 12w, and the LED is red (no info on the led besides that). It has a heatsink. What resistor should I wire up to prevent the LED from being damaged while maximizing it's brightness? If this isn't enough info, let me know what else I need to answer this question. The LED was running fine connected to a 6v (1.5V x 4 aaa batteries) with a resistor in series that was heatshrinked and couldn't be read once I took it off.


texts: Volt/Amp dependent RLC band pass -> Loudspeaker expander using lightbulbs

texts:
I want to create a input energy dependent frequency shunt network, which goes in parallel with a loudspeaker,

At low volumes, a certain midrange frequency should be shunted off the loudspeaker. The shunt effect should go down as the power from the amp goes up, and more midrange signal reach the loudspeaker

Edit: I should have added that it's for guitar amps: Strum the guitar lightly and the filter eats some midrange and the sound from the speaker thins; hit it hard and the lightbulb's resistance goes up exponentially, so that more midrange gets to the speaker and fattens up the sound. That's the basic idea.

Behavior:

At low voltage/current from the amplifier, the shunt network impedance should be low and reduce a certain audio band that reaches the speaker; let's say center f 500Hz, with a bandwidth of 300Hz , -25dB

As the energy coming from the amplifier goes up, the shunt network impedance should go up, therefore eliminating less signal and delivering more to the speaker.

The center f and bandwidth should stay the same as the energy goes up or down.

My idea is to use an LC band pass resonance network in series with a lightbulb. As the energy increases, the lightbulb heats up, resistance increases,
which raises the impedance of the shunt network, and directs more energy to the loudspeaker.

A cold 100W bulb reads around 40 ohms, it goes up tenfold when hot. I imagine 3 bulbs in parallel would be 13 ohms when cold.

I realize the following issue:

The lightbulb's resistance apparently does not influences the center frequency but the bandwidth! When cold and measuring 10 ohms, the bandwidth is around 300Hz. When host and measuring 100 ohms, the bandwidth goes up to around 3000Hz (which I do not want).

But:

The 16 ohm loudspeaker resistance will effectively be in parallel with the lightbulb resistance.

Would this deliver a stable low resistance, to keep the bandwidth in a narrow range?

Also the damping factor of the shunt network goes from 0.3 at 10 ohms, up to 3 at 100 ohms. Can someone explain the damping factor for me? Can this be translated to a total volume loss in dB? Or in voltage or current?

Is this whole thing even a possible approach or are there other issues with this idea?

Thank you for any help in advance :)


texts: How to amplify 0-10V 100Hz-1µHz sine wave to drive 24V 5A LED module?

texts:
For an experiment on photosynthesis, I would like to amplify a 0-10V 100Hz to 1µHz (~a day) sine wave from a function generator to drive a 24V 3A LED module.

I already did that with a square signal and a MOSFET as amplification system and everything worked fine.

For the sine wave, I can't use MOSFET, so I was looking at OPamp but I read in some various places (here for example : Very low frequency instrumentation amplifier) that, as far as I understood, classical OPamp based systems were not well suited for low frequency and DC amplification.

I also thought to an other option which could use a higher PWM base frequency and then modulate the duty cycle to simulate the sine wave.

Would you have any advice to guide my search ? Thank you !


texts:
I'm familiar with standard ESD control procedures (such as a grounding strap and/or mat) while working inside of a desktop PC. The general guidance for a standard ESD strap is to connect the strap to either an unpainted part of the system unit chassis, or to a central ground point (e.g. a specialized connector that connects the strap to the ground prong of a properly-wired AC outlet).
I'm wondering if in the case that these two options are unavailable whether it is as effective to connect an ESD strap clip to the ground prong of the desktop power supply (see attached photo).
Thanks.


texts: Why is the output of a series LC circuit sinusoidal?

texts: How to analyze this circuit? Why is the voltage across the inductor(red plot) and capacitor(green plot) sinusoidal?


texts: ECG Shield electronic circuit explanation

texts:
I have this electronic circuit which is from a shield for the Arduino which allows me to collect ECG signals. However I do not understand what is happening. I am familiar with op-amps and amplifiers in general but do not understand this circuit.

There is a INA321EA (PDF) instrumentation amplifier and a OPA43040U (PDF), which I can find on the internet, however I would like an explanation of what is happening in the circuit so I can learn how each component works.

http://i.stack.imgur.com/zXL2A.png


texts:
I have a need for a push pull circuit which can drive a line to either +12V, -12V or leave the line floating. The circuit needs to be able to source and sink 2 amperes to and from the line.
A 5V microcontroller is to control 2 transistors which should control the 2 mosfets

The general idea is that R3 keeps Q2 off by pulling the gate of Q1 to the source so that Vgs = 0V. Liikewise, R6 should pull the gate of Q1 to the source so that Q2 is also off in idle state.
Will this circuit work like I hope it will work?
EDIT:
I completely forgot about the forward diode effect of the MOSFETs. As such I shorted the +12V to -12V directly.
I have no real need for a galvanic isolation. It was merely the best thing I could come up with. I believe I can replace them by conventional transistors
EDIT2:
I replaced the optocouplers by a pair of transistors. And I fixed the symbols for the mosfets.
I think with this schematic that the P channel MOSFET will work but I am not 100% sure about the N channel. If Q4 is on, the Vgs of Q1 will be aprox. 12V + (5V - 0.7V) = 16.3V. This N channel mosfet is a P65NF06 and can handle a Vgs of 20V.


texts:
I use atmega328p.
I'm trying to read data from a variable resistor using an ADC.
The microcontroller also has LEDs connected. If I ignite them, the data from the ADC increases noticeably.

Initializing the ADC:

/***** ADC *****/
ADCSRA |= (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0); //128
// 16MHz/128 = 125kHz
ADCSRA |= (1<<ADIE); //enable interrupt
ADCSRA |= (1<<ADEN); //enable adc
//ADMUX |= (1<<REFS0) | (1<<REFS1); //1.1В
ADMUX |= (1<<REFS0); //AVcc with capasitor as AREF pin

ADCSRA |= (1<<ADSC); //new start
ADMUX |= (1<<MUX0) | (1<<MUX2); //ADC5

How can I solve this problem?

I apologize for the scheme, but I do not have the right program at hand.

Extra info due to answers:

In the normal state, the ADC value is 2. If I light the LED, the value is increased to 20. I changed the 220 Ω resistor to 1 kΩ, now value increases from 2 to 7. Voltage comes from USB 3.0.
In an attempt to make the PSU stronger I tried to solder the second USB connector and energize in parallel. Nothing changed.


texts: I'm trying to make an OOK modulated signal in ADS. I need a random bit generator, and a block to multiply a sinusoidal signal with that random pulse. I did this in Cadence by the 'rand_bit_stream' and 'pvcvsp' blocks. Are there any similar blocks in ADS?


texts:
I got a Decatur Si-2 Radar from Ebay. The brochure that I found online has this as the pinout:

+12VDC Power        1 (red)
RS232 TX            2 (black)
RS232 RX            3 (green)
Ground(shield)      5 (brown)
Ground              9 (black)

How should I hookup my Arduino to get the data, and do you think it will be readable?


texts:
This may sound over ambitious and silly but I think I should just ask. Lets assume a college campus (I mean a whole campus with buildings, gardens and workshops and stuff). I am thinking around 17 Acres of land. The signal of cellular phones is full just outside the campus, but just as you cross the first building you lose it totally. And then throughout the core of the campus, you don't have any signal at all.

Now how can I do a survey of such a situation for parameters like signal strength, causes of signal drop, places where I get a much better signal etc. There has to be some methodology to do it scientifically. What equipment will I have to use, are there any pre-existing DIY designs for these?

Also once I workout the cause of the signal drop, how can I boost it. Are there any signal booster for cellular network? I am thinking DIY type, something I would build myself and learning a lot of things in the process.


texts:
I have say, 4 170 MHz signals coming in on 4 BNC cables.  I would like to add these signals together.  Is there a name for a piece of hardware that does this?  Are there any special considerations I should make, is there a reason why I can't just use something like a BNC T-converter to add two lines into one?

Any help would be appreciated or even keywords I could google!


texts: I have to amplify a microphone signal to be in the range -2.5 to +2.5V. It is currently providing a signal that has a peak amplitudes of around 2V. This, however, is highly dependent on the situation (how close you hold the microphone to your mouth etc.). I need to be able to variably amplify it somehow to make the signal be in the required range. Is there a method of achieving this? I have read a bit about automatic gain control. Do you think this is the way to go?


texts: Designing a synchronous frequency divider to 13

texts:
First post here, so sorry for mistakes or inappropriate posting.

This was one of the tasks in a digital logic exam I failed today. The exact request was "Design a synchronous frequency divider to 13(state diagram, truth table, electronic scheme). Draw the signal/time diagram for the outputs Q."

As I understood from the course, frequencies can only be divided by powers of two (2,4,8,16 etc). Is this divider even possible at all? I had no idea even where to start.


texts: Usage of "initial" in Verilog module description

texts:
I'm writting a code and I have 2 dumb questions:

1- Is it a bad practice to use "initial" in the module description?

I'm asking this because I have a frequency divider with 2 signals (clk_in and clk_out). If I want to see the behaviour in simulation, I have to give an initial value to clk_out, otherwise clk_out will always keep as X.
Then, I used "initial" instead of using a reset signal.

2- Why the code without initializing the output works fine in the FPGA but it doesn't in simulation?

My code basically do this:         Clk_out <= ~Clk_out;

Thanks in advance.


texts: Understanding sampling rate and frequency of logic analysers

texts:
Below shown is the screenshot of the GUI for Saleae logic analyser http://www.saleae.com/logic

I would like to know what is the meaning of "number of samples to collect" and "sample rate" ?

As per my understanding, sample rate is how often samples are collected. Here it is shown 16MHz. so that means in one second, there are 16 mega samples collected.

But then what is this "1 M samples" ? Is it 1 million samples per second (but then what is 16MHz) ?

Or is it like this

in one second, we sample 16 Mega times
and in each of this 16 Mega sample, we will take 1 Million samples ?

Please correct me. I am so much confused.


texts: I would like to know the difference between dBo and dBe in relation to dBm. Does fiber optics have a specific matching impedance like the 50 ohm reference? Is this just a convention or is there an equation that specifies dBo for optics and photons to a dBe for RF or electrical parameters. These are all power related where the equivalent will be a watt or J*s answer.


texts: Keyboard mod - Replacing original red LEDs with white

texts:
I have a CM storm Trigger with blue Cherry MX, it's a good keyboard that I got a few years ago and still works perfectly. My only problem is with the backlighting, since my setup is now mostly white/black/wood and the red is not looking good.

I'd like to switch to white LED backlighting, I thought I could buy a pack of white 3mm LEDs and solder them in place of the red ones. I'm concerned about forward voltages, red diodes are usually ~2V and white ones are ~3V.

Many thanks.


texts: Selecting input and output caps and Schottky diode for buck convertor circuit

texts:
I have searched and googled until my brain hurts. I am designing the circuit shown, which will operate from an automotive electrical system and I was trying to ensure a clean power supply for the convertor and the IC. The buck convertor gives a value of 33uH for the inductor, and shows an input and output cap as well as a schottky diode in the output circuit. However, it does not give vales for the capacitors or the schottky, or how to calculate them.

In my searches I have come up with widely varying information as to how to calculate, some of which ask for things that I do not know (such as the maximum allowable voltage ripple of the load (in this case the MCU and the solid state MOS FET relay). I have gone through all of the relevant data sheets, but I can't make heads nor tails of this.

I am not asking someone to do my calculations for me or tell me what values and or parts to use. I just need some guidance on how to calculate these items.

ATTINY4-TS8R MCU data sheet:
http://www.mouser.com/ds/2/268/atmel-8127-avr-8-bit-microcontroller-attiny4-attin-1065795.pdf

G3VM-61GR2 MOS FET relay data sheet:
http://www.mouser.com/ds/2/307/en-g3vm_61gr2-780127.pdf

AP1506-33K5G-13 DC-DC buck convertor data sheet:
http://www.mouser.com/ds/2/115/AP1506-464471.pdf

I also used this TVS diode to help protect the regulator from transients -
MMBZ15VALT116 TVS diode data sheet:
http://www.mouser.com/ds/2/348/mbz15val-e-1077132.pdf

Thank you for any guidance you can provide!

simulate this circuit – Schematic created using CircuitLab

EDIT - The schottky has been identified and the schematic corrected for that.


texts: Power-supply made of battery+solar cell, ultra low power

texts:
In various scientific calculators, we can see that they have "twin" power, basically a mixture of a solar cell and a battery. I would like someone to tell me what kind of circuit usually takes both power sources to power efficiently a small low power MCU for example.

I would like to replicate this kind of circuit. I suppose there are ICs for that, as that would make sense in order to lower the quiescent current to the maximum, but I'm not much knowledgeable in this area. Take my Sharp EL-546w (picture here for example. I can put two LR44 or SR44 button batteries inside, and they last a few years even with frequent usage. What I don't understand as well is that these batteries are technically not rechargeable (is it  only a trickle charging solution found on these calculators then?).

I would really be interested in a solution that always takes the solar panel current first and somewhat "mixes" it with the battery current, while also making the voltage somewhat constant without the need to sink the excess current with a diode (as it draws power uselessly).


texts: Why use ground in oscilloscopes and what's the difference between it and a volte meter?

texts:
I am a high school student
And we lately started studying rc and rl
circuits
And my questions are
What is the difference between volte meter and the scope?
Why we use the ground as reference in the scope but not the volte meter?
Which one is the most accurate
Thank you in advance


texts: Single pole or dual pole relay for switching a 3 kW water heater?

texts:
I have bought a WiFi controlled device to control a 3 kW, 240 V water heater (immersion heater) wirelessly but despite being advertised as 15 A, it actually has a 13 A relay which has "push fit" contacts. I'm not sure I trust it to run for several hours at its maximum rating. I want to replace the relay with a 25 or 30 amp rated relay which will therefore be operating well below it's rated load.

However the original isolator switch to the immersion heater is dual pole. Should I therefore use a dual pole relay behind the isolator switch, or is this not necessary? Is there any advantage of using dual pole in this scenario? Given it's just a resistive load, I'm not sure if there's any particular merit of using a dual-pole relay in this situation?


texts: Trying to have NMOSs in parallel while passing current through only one at a time

texts:
If I wanted to have  a bias current I1 going through M1 or M2 and I want M1 to alternate between on off (M1 on/M2 off, M1 off/M2 on) would this work? I simulated this with spice and for the first cycle the nmoss have the bias current through one and none through the other but after the first cycle of the square wave they both have less than the bias current but not zero.  What would I be doing wrong? And what configuration would I need to achieve the effect I am looking for?  (Clocks go 0V-1.8V)

simulate this circuit – Schematic created using CircuitLab


texts:
This part came out of a Logitech nanoVX mouse. It is the IR sensor that is  part of the scroll wheel mechanism.

It has letters LT written on top and on the back it seems to have "H0fVE" or "HOfVE" or "HllfVE" engraved. Can anyone identify it?


texts: Voltage fluctuation on button cell battery

texts:
We had this display device which operated on button cell battery.  It allow us to do a read back on battery voltage which on display.
The voltage was found stable if leave the display device un touch.  However, it start to fluctuate upward or downward as and well we shake the device for a while.
Is this condition normal ?  Any explanation to the cause of it ?
Please advise.
Thanks.
Best regards.


texts: Does a 555 astable dissipate more power at higher frequencies?

texts:
I'm planning on running a circuit on a 9V battery and it uses a 555 in the astable mode to generate pulses.

I want this circuit to be as efficient as possible, and not have to replace the battery very often if it can be avoided.

Looking at the 555 datasheet, the max power dissipation is 1180mW (page 4) -- but is this lower at smaller frequencies? Or is the chip designed to dissipate the same power at any frequency?

I can't find any graphs on the datasheet (p6-7) regarding power dissipation with frequency, which is why I'm asking :/


texts:
I see the following statement in my iMax B6 manual:

It isn't necessary to connect an external balancer for balance charging.

Do I understand right that this entails that I can charge a serial-connected pack of 18650 elements with just one iMax B6 device and without disassembling them? If I do, do anybody can confirm that I understand the schematics right?


texts:
I hear about this technology, I read about it, I even see a bunch of MEMS microphones with PDM output.  I can perfectly understand how it works  (I have worked with DSP).  However, I can't seem to make heads or tails regarding how do I deal with it in practice.

I expect that there would be Digital Signal Processors that have built-in (hardware-based) PDM inputs;  I would even expect microcontrollers to have that  (since MEMS microphones typically used for mobile devices seem to use PDM interface quite often).

However, I do a search in Digikey, and not a single one lists PDM among the included features or interfaces  (not a single DSP, not a single MCU).
I did find a PDM-to-I²S chip (in 8-pin BGA --- *ugh*) , but it doesn't make sens that that would be the only option --- in that case, I might as well get a microphone with I²S output!

I think I understand enough of the math that I would be able to implement in software a bit-banged PDM decoder --- however, I also understand enough to know that that is unthinkable in practice.

I guess my concrete question for the audience is:  what's up with that?


texts: Calculating base resistors of a NPN driving a LED

texts:
I am a beginner in circuit analysis. I have a simple circuit and I want to get the right value of R1 & R2 resistance, to turn on the LED on collector of BC547. I need 20mA to turn on the LED and want 3.3V on base of BC547 transistor.

I tried to get the value of R1, R2 but the result is not correct.

My steps:

         5-IR1-IR2=0
         5-IR1-3.3=0
         1.7-IR1=0

[IR1=1.7v]

         IC=β*IB
         20m=110IB
         IB=0.181mA

to get approximate value of IB. I do it 5 times.

         IB=0.181*5=0.9mA

and I put the final value of IB in [IR1=1.7v]

So, the next:

         0.9m*R1=1.7v
         R1=1.8k

and go back to the first equation: 5-IR1-IR2=0 and add the value of R1 to get the R2 value.

         5-0.9m*1.8k-0.9*R2=0
         5-1.62-0.9m*R2=0
         R2=3.75k

This my analysis for the circuit, but I simulate it on Circuit Simulation Program like Multisim the result not match. I need help to know the wrong thing that I did.


texts: DC-DC SPMS Boost Converter DCM Prevention

texts:
Sorry for the long question, it's really opinions I seek which is why I felt I needed to explain the scenario and how much I know/don't know. I would really like some input on my design. I am designing a DC/DC SMPS(switch mode power supply) boost converter.

The general advice about DCM(discontinuous conduction mode) in SMPS boost converters is to try and avoid it. This advice is usually backed up by a barrage of equations. Unfortunately I am not very good at Engineering Maths, but if the DCM is anything like the equations, I get the point, I'll stay away :D ! Aside from adjusting switching frequency, increasing the inductance value looks the biggest way to avoid DCM. In my boost converter the output voltage can be varied(it's microcontroller based) and I expect the load to make the input current vary from 10mA(high inductance needed) to 4A(relatively high saturation current needed). I have had some problems in finding an inductor that would fit my specification, I used Digikeys' Parametric search.

Since inductance value is mostly inversely correlated to saturation current, I understand why it may be hard to find my golden inductor. I have found about 8 out of tens of thousands on Digikeys' site, but they are unshielded(which I don't want for this application), large :( and expensive :( .

I understand how DCM works well enough, that the converter enters DCM when the load current is so low that the discharge cycle of the inductor lets the inductor current slip past zero.

So here is my take, since this application is microcontroller based, couldn't one simply just stop the discharge of the inductor when the current nears zero? I know this means distorting the PWM. What I am suggesting is having two microcontroller pins connected to the base of the MOSFET(or gate driver to MOSFET) that controls the inductor charging. One is switched based on the PWM while another simply goes high when inductor current value drops to the microamperes range. I plan to use another MOSFET (Q2) in the inductor discharge path to measure the inductor current. I'll be using the Vds of the MOSFET (Q2) to calculate the inductor current and decide when step in to charge the inductor. So do I get the IEEE prize for SMPS design :D ? Well I doubt it, as while I was learning how to design a boost converter(which I did off the internet thanks to so many kind people), most of the designs I saw used a SMPS controller so I can understand that there wouldn't have been as much flexibility as with a microcontroller based approach because I never saw anyone discuss this.

So my question is, what are your thoughts? I haven't had the opportunity to test it on a breadboard yet, will do soon, but whether it works or not, I want to know if there is something I am missing, or the opinions of anyone on this idea. I am not an experienced circuit designer so I could do with some input.

Thanks for taking the time to read the question. :)


texts: Can someone help me understand this H-Bridge?

texts:
I have an old RC car but without the transmitter so I built my own Rx/Tx using MCU and 2.4Ghz transceiver, however, I want to use the car's original H-Bridge but not sure if I understood how that circuit works.

Here is the schematic for the bridge:

My understanding is that P1 and P2 are for forward direction and provide different speeds!?, while P3 is the reverse direction. Correct me if I am wrong.

My questions are:
1- Can I use logic level to drive P1-3 (directly from MCU pin) ?
2- When setting one of them high should the other two be low? Can P1 and P2 be high at the same time?
3- What is the purpose of R1?, Why only 1Ω?, Why 10W? and Why it is only connected to Q1 and Q2 and not T9 (since all three are PNP high side transistors)
4- Why does it have a diode D4 for only one of the inputs (P1)?
5- What is the purpose of D1, D2 and D3?
6- How does T1 drive T5 and Q2? Since its collector and emitter are connected to the base of the other transistors! no ground or vcc!? I am confused.
7- Can I use PWM to control the speed of this bridge? (default frequency for Atmel Atmega328 is 32K)

(Note: C1, C2 and C3 are actually polarized electrolytic capacitors)

----- Updates ------

Here is the modified design after fixing the swapped transistors pins, removing the slow forward circuit and adding flyback diodes:

So how does it look? anything that need to be changed? removed? added?


texts:
I need to make a robot within a month for a competition. I used to use Arduinos for my projects, but graduated to just flashing code with avrdude to standalone AVR microcontrollers.

I was thinking, just because I don't use the Arduino hardware anymore, is there any reason not to burn an Arduino bootloader on to my microcontrollers for some projects? Are there scenarios (like my current task) in which doing so would actually be advantageous?

It is a little easier to write code for an Arduino, and there are several open source libraries. I am sure there are other key advantages (and disadvantages) which I am not aware of, but would like to know about.

Essentially, under which scenario(s) would it be a good idea to burn an Arduino bootloader to my micrcontroller.


texts: Mesh Current Method Circuit Analysis For AC Transient and Steady State Solution of RL Circuit

texts:
Hi everyone, I'm trying to find the currents through each branch for the above circuit using mesh current method (as I don't really know how else to do it), and end up with two simultaneous differential equations:

$$Mesh 1:  R_si_1+R_1(i_1-i_2)+L_1\frac{d}{dt}(i_1-i_2)=155cos(377t)$$
$$Mesh 2:  R_2i_2+L_2\frac{d}{dt}i_2+L_1\frac{d}{dt}(i_2-i_1)+R_1(i_2-i_1)=0$$

These simplify to:

$$Mesh 1:  (R_s+R_1)i_1-R_1i_2+L_1\frac{d}{dt}i_1-L_1\frac{d}{dt}i_2=155cos(377t)$$
$$Mesh 2:  -R_1i_1+(R_1+R_2)i_2-L_1\frac{d}{dt}i_1+(L_1+L_2)\frac{d}{dt}i_2=0$$

The problem I am having is that I cannot figure out a linear combination of these equations to eliminate either i_1 or i_2 variables to solve the system.

Am I going about this the wrong way? Or is there an easier way to solve this?

I can readily find the steady state solution reducing everything into impedances but I need to find the transient solution as well.


texts: Controlling output voltage using Arduino

texts:
I want to control the temperature of a heat pad, which heats up using a power and ground pin, and is controlled by a pressure sensor.
The micro controller I am using runs onl 3.3V but the desired amount of heat I would like to generate needs between 5-12V.
I’ve done some research and I have come across a step up module or a relay, in order to increase the voltage.
Would one those be sufficient? If not what would work best for this project? Would I need two different power supplies?


texts: 38999 contacts for pcb through-hole pass through connectors

texts:
So I'm working on a board that will act as a pass-through for a m/f pair of connectors interjecting to trace off some of the contacts to connect to another device for monitoring the signals. We did something similar for another project and the following image shows what I'm trying to find. I've found the right side's contact is called "PC Tail contacts" but I've been through like 500 pages of catalogs trying to find the contact on the left. Does anyone know what this contact is called and maybe where I can order them?

The right pins are going to get soldered to the board in through-holes and then the other connector will mate with the rest sticking out creating the pass-through for the two connectors. Any help would be appreciated as I've spent way too much time googling this and digging through catalogs.


texts: Flip-Flop Made with 74xx Chips not Latching Consistently

texts:
I'm trying to connect two latches made by 74xx chips (normal output: 7404, 7408, 7432...), so that the inverted main output signal is latched into the first circuit on the falling edge and into the second circuit on the rising edge. Thus the main output will switch from low to high and vice versa every clock cycle.

The clock is a debounced push-button connected to a inverted to create sharp edges.
The timing is done by sending the clock signal through more inverters.

Each circuit works perfectly when tested individually, but as soon as I connect the output of the first one to a input of the second one, it only latches correctly about 20% of the time.

To fix this problem I added a 1uF capacitor.

When testing the circuit, I found that on one AND-gate the output goes low before any input goes low. I tested it with a simple S-R-latch to check wich signal goes low first.

Here's the schematics:

simulate this circuit – Schematic created using CircuitLab

Here's the breadboard:

The yellow wires at the bottom create a S-R-latch that I used for testing.
The testing showed that the output of the first AND-gate on the third chip goes low first, then the clock signal (first input), then the output of the first OR-gate (second input).

What should happen (3rd chip, 1st gate):
Clock goes low -> output goes low -> 2nd input on the 2nd AND-gate goes low AFTER the clock on the 2nd AND-gate goes high -> latch successful

What seems to happen:
Output goes low (??) -> clock and 2nd input go low (on time) -> 2nd input on the 2nd AND-gate goes low BEFORE the clock on the 2nd AND-gate goes high -> latch unsuccessful

One might think that the output goes low too early, because the 2nd input goes low before the clock does. But that can't happen because the signal of the 2nd input depends on the same clock and goes through more transistors (is delayed). Yet holding the second input stable with a capacitor solves the problem.

So, how can the output of that gate go low before any of the inputs?

Why do both circuits work when separate (which means the 2nd input of their first AND-gates is manually pulled high or low) but not when the second latch gets its signal from the first one and vice versa?


texts: Development board with cellular capabilities smaller than Arduino

texts:
I would like to build my own cellphone (phone calls and texts at least).

Having experience with Arduino, I found several cellular shields and libraries that could allow me to do so with Arduino.

However, this would make my phone pretty big (for a phone) as it would be the size of the arduino plus the shield.

Is there any smaller alternative for this?

I know a lot of development boards exist, and some of them are smaller (even Arduino mini for example), the only problem is I can't find one that has (or can have via a module) cellular capabilities in small size.

(and unfortunately I need to find something not too expensive of course)


texts: Driving 4 100mA motors using GPIO pins and BS170s

texts:
I'm trying to drive 4 tiny vibrating motors which draw 100mA at a maximum of 5V. I need to control them using PWM from the GPIO pins and would like to accomplish this in the smallest form-factor possible as it's for a portible device. I've looked at other motor driver hats and see that most require external power supplies which turns me off as all I want to use is the supply that is powering my RPi.

I've been asking some friends what they think and I've been advised to use 4 BS170 MOSFETs each with a 1N4001 diode to protect against voltage in the wrong direction when turning off the motors.

I'm here essentially to verify that this is a good setup and hear other recommendations as I'm not super familiar with this level of hardware. I'd also love some help with diagramming out how I would go about wiring these (in regards to the MOSFET and diode) coming off the Pi.

Thanks for your help!


texts: Can we measure reflected power in a transmission line?

texts:
This is a question related to radio transmission, I hope this is the proper forum to ask it. It relates to transmission lines connecting a radio transmitter to its antenna.

In his book "Reflections", at the start of Chapter 8, M. Walter Maxwell says "Energy reflected by a mismatched line termination can be entirely separated from the forward-travelling wave, and then be dissipated in a temperature calibrated resistor, and accurately measured as I^2R heat."

He later says "I have performed these measurements many times"

Now I find this book long-winded and too assertive, so I haven't read it all. Is he right? How can we do this measurement? What does it really measure?

I believe that forward and reflected power are mathematical artifacts used to make the calculations possible, and do not exist as separate physical entities. Am I right?


texts: VK3BHR LC meter inductance measurement problem

texts:
I am making the LC meter V2 designed by VK3BHR Phil Rice.
https://sites.google.com/site/vk3bhr/home/index2-html
I have seen many have done this and it works fine, but in my case it is not measuring inductance properly. For example a 90uH coil shows 52uH, 3.3uH shows 0.3uH. The measurement is completely wrong. Capacitance measurement is looking OK. Calibration was done using a 1% 100pF NP0 capacitor. I checked F1 and F2.
F1 = 00042879 (little lower than recommended value of 00050000 +- 5%)
F2 = 00032223 (within 71% of F1)
I have used all new components and L is a 100uH +/-20% toroid whose internal resistance is 0.3 ohm. C and Ccal are 1000pF NP0 +/-5%. I am using the PCB designed by VK3BHR. The relay is driven by a BC548B transistor as I cannot find a low current relay and I have checked the relay, it's clicking and contact resistance is less than 1 ohm.
I am thinking that the +/-20% tolerance for the 100uH toroid is too high. What else could be wrong? I will provide any other info that is useful for troubleshooting.
Can anyone help me to find out the problem?
Circuit diagram:


texts:
I am trying to simulate the transfer characteristics of a CMOS inverter using LTspice.
I want to sweep the MOSFET width and length and observe the effects on rise and fall times of the CMOS inverter.
Is there any way of setting up a sweep of MOSFET width and length ?


texts: How to import ECG file into verilog as input

texts:
I am trying to import the ECG file into the verilog as input for the hardware implementation. In Matlab, I can just simply load the input ECG (.mat file) and processed the input signal as per desired through the commands.
However, for hardware implementation I will be using verilog. Is anybody is can share the sight on this?
Really appreciate for the help.


texts:
I have come across a gate driver circuit (proprietary) that measures open-collector current and sets a flag if the current exceeds a threshold (say 20 mA) to protect the NPN transistor.

This is the "schematic" from the datasheet.  How would such circuit be implemented to be inexpensive and reliable?

Edit:  My question is how can this open-collector circuit be modified to also measure the npn transistor current?  The basic open-collector functionality is obvious.  I'm interested in how to protect this open-collector circuit from excessive currents caused by too small value of R_pullup.


texts:
I want to start an electronic project, and found that an  ARM based MCU, like STM32F103C, fits my needs more than AVR like Arduino Uno (mostly because of CPU and RAM.)

I was wondering if I can use any Arduino sensor with my STM32 board?

Looking a list of the sensors related to STM32, they seem much more expensive.


texts:
I am Doing a electronics project for school.
I need the arduino on request from a button to input to commuincate to the computer to open a media file, this is to help a deaf person be able to play his dvds with out having to put them in the dvd player as he is mostly blind anyway

Any Help will be gratelly appreciated


texts:
I need to limit a signal to the following range: [-0.25V, 0.25V]. This signal is comming from a shunt resistor in series with a load with variable impedance on a 220V power grid.

The project contemplates loads up to 1A peak, but I can't guarantee this restriction will be obeyed all the time. But I need to guarantee the resulting voltage don't exceed the specified range.

To give a small guarantee, I'm using a shunt whose equivalent resistence is approximately 0.235 ohms, which generates a voltage slightly below the limit when 1A is consumed.

I cannot use normal diodes because its forward voltage is too high. I've tried to use two low forward voltage Schottky diodes (BAT46), but didn't worked in my simulations.

How can I do this? I need a solution that uses simple components, because where I live they don't have a big component variety and to buy those components on the internet it takes more than one month to arrive. I already have this BAT46 I mentioned.

First edit

Here is my current schematic:

Where:

R_IC is the IC's input pin impedance, according to its datasheet.
R_LOAD is the already mencioned variable load. In most circumstances, it will consume less than 1A peak, in another words, its "average" impedance will always be above 311 ohms. But I'm trying to avoid the range of the input pin to be exceeded in possible peaks (when the load is connected, for example).

Since I've asked the question last night, I kept searching for alternatives. I found a clipping circuit voltage in a Malvino and Bates' book. The difference compared to my original circuit is the presence of R_C resistor. The book says that its value should be somewhere around 1% of the load value (which in this case is R_IC).

I must say that the simulation result improved considerably with the presence of the R_C. And I think I understand its purpose: it is to "consume" the potential difference that exceeds the threshold that the diodes will establish. But still the established limit is not being respected.

I'm open to suggestions on how to ensure that the limit is obeyed with less "tolerance." But as I said, I need solutions that use simple components (diodes, transistors, op amps, etc).

Second edit

Now I'm offering a little bounty (in accordance to my low reputation).

I looked for other solutions and I managed to assemble the following circuit:

Now I'm using "normal" diodes (forward voltage about 0.6V). The first stage of opamps are to don't mess with equivalent resistance (I think this is officialy known as "impedance transformation"). The second opamp is to invert the bias.

This way I can "remove" voltage from the diodes and put them in short with less voltage.

As you can see, this apparently works (input on the left, output on the right):

But when the input is below the threshold, the output is slightly lower than the input:

This isn't a real problem, but if I can avoid it, it would be better.

Now... the questions:

First of all, will this work?
I've used this simulator because it is very simple. But I didn't choose a opamp. The only opamp that I know is the 741. What opamps can you recommend to me?
About the diodes... 1N400x serves this purpose?
How can I make negative supply for all opamps?
How can I better calibrate the components values to get even closer to the threshold?


texts:
Recently I have gotten myself in to buying USB flash drives in order to back up some of my data, however once I got into the detailed specs of the consumer flash drives I have gotten worried, about the quality of the NAND flash chips inside them. The most recent flash drive I bought is a 32GB 3.0 USB with Micron TLC chips. Now I know that these chips have about 1,000 program/erase cycles, but the problem is that I can’t find any real explanation what it takes for one of these cycles to happen. Basically, this is the question:

If I copy a 1KB txt file to the 32GB flash drive and then erase it does that use one P/E cycle, or do I have to actually write over time 32GB of data to the drive and erase it over time, for one of these cycles to be completed? Also does formatting the drive destroy some of its cycles?

Sincerely,

Neil


texts: Integrator with Voltage on IN+ and measuring Vout and V-?

texts:
I know the ideal integrator topology and output equation. But - what is the affect of connecting a supply at the positive input (instead of GND)? How can that be calculated mathematically for NODE1 and NODE2?

simulate this circuit – Schematic created using CircuitLab


texts: Assembly language that corresponds to machine instruction in MIPS

texts:
I am working on a problem that asks for the assembly language that would correspond to the following machine instruction in MIPS:

OX3062FF80

Here is what I've done:

step 1: convert to binary

0011 0000 0110 0010 1111 1111 1000 0000

opcode: 000000 <--- im not sure about this part ( I thought it should always be zero)
rs: 00011
rt: 00010
rd: 11111
shamt: 11110
funct: 000000

add $15, $3, $2

Is this correct? I am going off an example but I am not entirely sure if its correct. Any help, advice would be appreciated. Thank you.


texts: I have a 12V pulse square signal coming from an RPM sensor. I would like to translate it into 5V pulses since I will need to use it as input in an Arduino. What do you guys think is the easiest way? Can a comparator be used?


texts: Why create clk and clk NOT with 2 inverters instead of 1?

texts:
I see many circuits use this topology

Why dont we use just only one inverter like this:

Thanks very much!


texts: Can I connect an amp directly to an adc?

texts:
My question is simple. I'm designing a circuit and read some articles saying that you need to provide a DC bias current return path. These articles always referenced using them with floating inputs and when ac coupled. I've also seen this referenced in many adc datasheets. I have a return path for the inputs of my amp.
My question is do I need a return path between the amp and adc or would that be taken care of innately by the amp?

simulate this circuit – Schematic created using CircuitLab

My design is like the bottom one. I have quite a few amps connected to the adc so if the resistor is unnecessary that would simplify the design a bit. Thanks for any insight you guys can provide. Not sure if this affects anything but I'm using instrumentation amps.


texts: What is the biggest stable memory overhead for SSDs?

texts:
With an HDD, the largest overhead in accessing stable memory (where we measure access time from the moment the instruction passes the MEM stage in the pipeline) is the I/O costs for seeking the right track on the disk.

Overall, the contribution to time is probably something like this (I'm guessing, please correct me if I'm wrong):

Seek > Rotation > Copying to buffer > OS page replacement code
     > Actual bus I/O costs and copying to in-memory location
     > Context switches

I'm pretty certain about the first one, though.

What is the order for flash memory?


texts: Is it ok to leave analog switch inputs floating?

texts:
Will I run into problems if I leave a few of the analog pins on a CMOS switch (such as the DG409) floating?

I know that CMOS digital inputs should never be left floating due to the fact that the transistors tend to both partially conduct (resulting in excessive power consumption and heat), but I'm not sure if this rule also applies to bidirectional analog pins, even if they use CMOS internally.


texts: Fixing logic for a relay-driven bidirectional AC Motor

texts:
I'm trying to diagnose a relay control for a motor which was wired by someone else.

QUESTION: How does this theoretically work?  What is it called?

Pictured here is the relay which controls a bidirectional motor.

I believe the way it works is

there are two poles for this single relay, represented by A1 and B1
by default, when no control voltage is applied across terminals (C+/C-),

pole A1 is connected to A3
pole B1 is connected to B3

when a control voltage is applied across terminals (C+/C-),

pole A1 is connected to A2
pole B1 is connected to B2

The confusing thing for me is the way this relay is wired: It seems like both circuits are never completed.

How does this theoretically work?
Am I confused about how the relay works?
Is the relay miswired?

It seems like something should be connected to A2,A3,B2,B3. But what?


texts: Values got from programmed PID are different from ones simulated in Simulink

texts:
Please also read Update
I created a PID simulation in Simulink:

where the Step block is set with parameters:
Set time = 0
Initial value = 0
Final value = 100
Sample time = 0.01

And I coded the above PID in MATLAB:
classdef PID < handle
    properties
        Kp = 0
        Ki = 0
        Kd = 0
        SetPoint = 1
        Dt = 0.01
    end

    properties (Access = private)
        IState = 0
        PreErr = 0
    end

    methods
        function obj = PID(Kp, Ki, Kd, SetPoint, Dt)
            if nargin == 0
                return;
            end
            obj.Kp = Kp;
            obj.Ki = Ki;
            obj.Kd = Kd;
            obj.SetPoint = SetPoint;
            obj.Dt = Dt;
        end

        function output = update(obj, measuredValue, t)
            err = obj.SetPoint - measuredValue;
            P = obj.getP(err);
            I = obj.getI(err);
            filter = lowPass(obj,t);
            D = obj.getD(err*filter);
            output = P + I + D;
        end

        function val = getP(obj, err)
            val = obj.Kp*err;
        end

        function val = getI(obj, err)
            obj.IState = obj.IState + err * obj.Dt;
            val = obj.Ki * obj.IState;
        end

        function val = getD(obj, err)
            val = obj.Kd * (err - obj.PreErr) / obj.Dt;
            obj.PreErr = err;
        end

        function val = lowPass(obj,t)
            N = 1;
            val = 1-exp(-N*t);
        end
    end
end

The transfer function same as the one in the Simulink:
function r = getResponse(t)
r = 0.2 - 0.2*exp(-5*t);
end

And the code for the programmatic simulation:
sr = 1e2; % sampling rate 100Hz
st = 10; % sampling time 10s
ss = st*sr+1; % sample size
t = 0:1/sr:st; % time

input = ones(1,ss)*100;
output = zeros(1,ss);
measured = 0;

pid = PID(0,1,0,input(1),t(2)-t(1)); %Kp=0,Ki=1,Kd=0
for i = 2:ss
    rPID(i) = pid.update(measured, t(i));
    output(i) = rPID(i)*getResponse(t(i));
    measured = output(i);
end
figure;
hold on;
plot(t,output)
plot(t,input)
plot(t,rPID)
legend('Output','Input','PID')

I have confirmed that when Kp=1; Ki=0; Kd=0;, both simulations yield the exact same result. But when I set Kp=0; Ki=1; Kd=0;, the results are different.
Simulink result:

Programmatic simulation result:

As you can see, not only the final values are completely different, but the difference starts from the very beginning at the first time stamp 0.01s. I can't think of how Simulink does the calculation and where my mistake is. (I know I must have some mistake in low pass filter -> the derivative term, but they are isolated from this example.)
The last time I did control system was years ago in undergraduate, so I must have made some very fundamental mistakes.

Update
I recalculated the inverse Laplace transformation. It turns out my previous calculation is incorrect. The correct getResponse function is:
function r = getResponse(t)
r = 1 - exp(-5*t);
end

After this correction, the result looks much similar:

However, there is still some minor differences. Here's a figure showing the difference (programmatic simulation result - Simulink):


texts: Why can't I send data from a PC to an Arduino?

texts:
I developed an app which sends data to an Arduino by serial port, but I can’t t understand how to receive the data in the Arduino. I send a string by serial port to the Arduino and the Arduino receives something but my code doesn’t work. In the Arduino the data is received byte by byte.

The C# code which sends the data:

using System;
using System.Windows.Forms;
//
using System.Threading;
using System.IO;
using System.IO.Ports;

pulic class senddata(){

    private void Form1_Load(object sender, System.EventArgs e)
    {
    //Define a Porta Serial
        serialPort1.PortName = textBox2.Text;
        serialPort1.BaudRate = 9600;
        serialPort1.Open();
    }
private void button1_Click(object sender, System.EventArgs e)
{
    serialPort1.Write("1");  //This is a string
}

}

The Arduino Code:

#include <Servo.h>

Servo servo;
String incomingString;
int pos;

void setup()
{
    servo.attach(9);
    Serial.begin(9600);
    incomingString = "";
}

void loop()
{
   if(Serial.available())
   {
   // Read a byte from the serial buffer.
   char incomingByte = (char)Serial.read();
   incomingString += incomingByte;

     // Checks for null termination of the string.
     if (incomingByte == '\0') {

      if(incomingString == "1"){
                servo.write(90);
          }

       incomingString = "";
    }

  }
}


texts: Laplace transform to Z-transform for filter design

texts:
I was given an answer to the following question I can't understand, that how is the Impulse Invariance transformation of
$$\frac{(s+a)}{(s+a+jb)(s+a-jb)}$$ is
$$\frac{(1-e^{-aT} cos(bT) z^{-1})}{(1-e^{(-a-jb)T} cos(bT) z^{-1})(1-e^{(-a+jb)T} cos(bT) z^{-1})}$$ ?


texts: How to calculate the phase difference between current and voltage?

texts:
Using the next circuit and the components of

simulate this circuit – Schematic created using CircuitLab

\$R=20\Omega\$
\$L=25mH\$
\$V_{DC}=36\$
\$v_{s}(t)=50+\underset{n=1}{\overset{\infty}{\Sigma}}(\frac{400}{n\pi})sin(200n\pi t)\$

The idea is determinate the average power absorbed by R.

So using the Fourier series based on the generalized Parseval identity
\$\frac{1}{L}\int_{0}^{c+2L}f(x)g(x)dx=\frac{a_{0}c_{0}}{2}+\overset{\infty}{\underset{n=1}{\Sigma}}(a_{n}c_{n}+b_{n}d_{n})\$

\$P=V_{o}I_{0}+\underset{n=1}{\overset{\infty}{\Sigma}}\frac{V_{m}I_{m}}{2}cos(\theta_{n}-\phi_{n})\$

\$I_{0}=\frac{V_{0}-V_{DC}}{R}=\frac{50-36}{30}=0.7\,A\$

\$P_{0R}=(0.7^{2})(20)=9.8\$
\begin{array}{|c|c|c|c|c|c|}
\hline
n & V & I & Z & Angle & P\\ \hline
\hline
\hline
0 & 50 & 0.7 & 20 & 0 &9.8\\ \hline
\hline
1 &\frac{400}{\pi}=127.32 & \frac{V}{Z}=5.00 & \sqrt{20^{2}+(200\pi25mH)^{2}}=25.43 &  & \\ \hline
\hline
2 &\frac{400}{2\pi}=63.66 & 1.7& 37.24 &  & \\ \hline
\hline
3 & \frac{400}{3\pi}=42.44 & 0.829 & 51.19 &  & \\ \hline
\hline
4 & \frac{400}{4\pi}=31.83 & 0.4827 & 65.93&  & \\ \hline
\hline
5 & \frac{400}{5\pi}=25.46 & 0.3141& 81.04 &  &  \\ \hline
\hline
\end{array}

But where Im stuck is how can be calculated the phase difference (the angle column) between the current and the voltage, since I think the second angle of \$cos(\theta_{n}-\phi_{n})\$ would be zero for every term of the series.

UPDATE
Whith the idea of The Photon that the inductor current indeed is out of phase but this can't cause the resistor voltage and current to be out of phasem and using the RL impedance

\begin{array}{|c|c|c|c|c|c|}
\hline
n & V & I & Z & Angle & P\\ \hline
\hline
\hline
0 & 50 & 0.7 & 20 & 0 &9.8\\ \hline
\hline
1 &\frac{400}{\pi}=127.32 & \frac{V}{Z}=5.00 & \sqrt{20^{2}+(200\pi25mH)^{2}}=25.43 & 0.665 & 250.47 \\ \hline
\hline
2 &\frac{400}{2\pi}=63.66 & 1.7& 37.24 & 1.003  & 29.099\\ \hline
\hline
3 & \frac{400}{3\pi}=42.44 & 0.829 & 51.19 &  1.169& 6.879\\ \hline
\hline
4 & \frac{400}{4\pi}=31.83 & 0.4827 & 65.93& 1.262 &2.334 \\ \hline
\hline
5 & \frac{400}{5\pi}=25.46 & 0.3141& 81.04 & 1.321 &0.988  \\ \hline
\hline
\end{array}

So the average power absorbed by R is \$299.57 W\approx300 W\$


texts: Understanding Master/Slave trigger configuration through open-drain GPIO

texts:
I am working with two industrial cameras that I want to trigger synchroniously through hardware triggering. For this the STROBE_OUT pin (which is an open drain pin) from one camera (Master camera) does trigger the other camera (Slave camera) when an image is taken by the master camera.
The camera manufacturer gave me an connection schematic on how to connect the pins of both cameras.
The connections diagram they gave me looks as follows:

From the datasheet of the camera I know that the STROBE_OUT pin is a mosfet open drain configuration (pin 2 with corresponding ground on pin 1). The TRIGGER_IN (+/-) pins internal connections are given below (pin 3 and 4):

This way of connecting it really seems strange to me. In my understanding, when the mosfet is closed the pin 3 of the slave would be pulled to ground, but when the mosfet is open the pin 3 would be in a floating state, am I right? In my understanding this could lead to undefined behaviour?
I would rather assume do a connection with a pull up resistor for example something like the one below:

(Sorry for that ugly drawing)
Am I misunderstanding something here? What would be the proper way of connecting this?


texts:
I had been using these modeling technique for counting number of clock cycles.

Delay is created and inverted - to get small positive edge of the clock and count numbers is charged based on the number of pulses. But this needs to change value of  R2 and C2 and counts are sometimes greater or less than integers.
Is there any other alternatives so that we can count number of clock cycles and reset it?


texts: How to control over-voltage at high voltage?

texts:
Suppose we're using a voltage multiplier to charge a high-voltage capacitor (C Big in the diagram).  If you significantly exceed the capacitor's voltage you'll destroy it.

simulate this circuit – Schematic created using CircuitLab

Now suppose we're talking about something in the 4kV range, and the capacitor has very low ESR (10 milliΩ).  What are good methods to protect the capacitor from overvoltage?

One idea I had was to put a Zener clipper on the AC input, and then construct the multiplier to not exceed the design voltage knowing the input voltage limit.

But of course there's all sorts of exciting "Stuff" happening on the C Big side of the circuit that could lead to feedback spikes.  Because of the big capacitor's low ESR I'm assuming there's no way to use diodes to protect it by diverting voltage spikes.  So, if we care, is the only other protection going to be via FETs – presumably regulated off of resistor voltage dividers?


texts: What is protective bonding (PB) and protective earth (PE) in IEC terminology (fx 60364 and 60204)?

texts:
I understand the basic/overall meaning of both, just as well as my electrician co-students. However, I really would like some more precise definitions than what I have been able to find so far. I find it frustrating not having proper definitions, because a) I am constantly in doubt if I am using the terms properly when writing reports or other school work, b) when reading about fx requirements for PE conductors, do those requirements also concern PB (and vice versa).

Here are a few specific questions that I would like settled once and for all if possible.

Are PE-conductors a subset of PB-conductors? You could argue this, since any two objects connected with separate PE-conductors both ending up in the same PE terminal, will be equipotential. Obviously, a PB-conductor directly between the two will have lower impedance and thus be better at achieving equipotential, but still.

Are PB-conductors a subset of PE-conductors? That depends on the definition of PE-conductors, but often PE-conductors are described as if their main characterization is that they allow either an over current detection device or a fault current detection device to shut off the power if an object is electrified. And if that is the characterization, then an equipotential bondings directly between objects will also help make sure that this happens, and in some cases these bonds are the only reason why it happens.

Are they disjoint sets? So that any of these protective conductors is always strictly either a PE-conductor or a PB-conductor?

Or are they overlapping? That means some of these protective conductors are   PE but not PB, some are PB but not PE, while some are both. If so, please provide an example.

If possible please provide sources for your answer, and please provide examples.


texts: For audio work, Arduino work and other electronics projects, why would you decide NOT to buy esd-safe screwdrivers, pliers, cutters and tweezers?


texts: Motor driver using only a 2N2222 transistor?

texts:
Is it possible to build a motor driver using only a 2N2222 transistor?

If yes, then how?


texts: DC Power Supply: Turns Ratio Calculation

texts:
I am an electronics newbie looking to broaden my horizons, so I'm going through The Great Courses's Understanding Modern Electronics course. In Lecture 4, they give a project in which the goal is to simulate a DC power supply.
The supply should step-down a 120-volt rms, 60 hertz AC signal to a 5-volt DC signal. I got the correct schematic, but I came up with a different turns ratio than the one given in the project solution. The solution gives a turns ratio of 28:1, but I calculate a turns ratio of 21:1 by solving: $$5.7V=\frac{N_2}{N_1}(120V)$$
where 5.7 volts is the voltage before the voltage drop across the diode.
I simulated the circuit in LTspice XVIII, and it confirms that the turns ratio should be approximately 28:1, not 21:1. The closest guess I have as to why this would be would be that I ought to use a value of 4.3 volts instead of 5.7 volts, which corresponds to 5 volts dropping across the diode. However, this conclusion is contradicted by my simulation below, which has the expected value of 5V, not 4.3V, across the load.
How can I correctly calculate the turns ratio for my transformer?


texts: Can we use a ground plane and a VCC plane in a 2 Layer PCB?

texts:
I am designing a custom PCB of 2 Layer in the eagle CAD with SMD components. It is difficult to route the VCC and the ground for all the planes. I used a ground plane on one side. But for the VCC I thought of using a power plane but I have AC mains trace also in the top and bottom plane. Either can I use a power plane in a specific area or I shouldn't use the power plane itself. what are the advantages and disadvantages of using power and ground plane in 2 layer PCB? Whether can I use the power plane with the ground plane in 2 layer PCB?
Thanks in advance.


texts:
Objective
Our gate opener remote receiver works much better with the antenna horizontal than vertical? By much better, I mean 300' vs 100'. Why?
Background
The distance the remote will operate the gate appears to be independent of time of day, and/or weather conditions.
The antenna is directly connected to the receiver which connects to the gate controller with a 3-wire cable. As best as I can determine the receiver sends remote codes to the controller on one of the 3-wire cable conductors, the other two are for power and common.
Frequency is ~320MHz, and the antenna is ~9” long.
The antenna originally was near vertical, but it sagged under gravity to a more horizontal orientation. I know the antenna will continue to sag and I'm thinking distance will suffer as it becomes more vertical.
I could straighten the antenna to vertical and the range would suffer, I 'know' it is antenna orientation but can't explain it to myself.
Imagery


texts: Is a modern radio wave broadcasting station a very fast spark gap transmitter?

texts: In a spark gap transmitter, is that a "real" radio wave that is produced?  I know you can hear it on an AM radio, if you are close to the gap, but is it a radio wave the same as from a radio station?  Except from a radio station or modern transmitter the "gap transmitter" would be very, very fast?


texts: Most efficient way to drive an LED from 9v source?

texts:
I have a circuit that I am powering from a 9v battery. I bought little 3mm flat LEDs and I want to use one for a power indicator, but don't want to use a voltage divider that will consume too much power. The rated voltage is 3.2-3.4v and it came with a current limiting resistor of 430 ohms.

What would be the optimum method of reducing the voltage and limiting current such that I minimize power drain? I'm assuming it will be a voltage divider and/or a voltage divider, but what would be the optimum values?

(Update to question) Is it possible to use a single large resistor in series with the LED to both reduce the 9v down to 3.3v and provide the required current limiting function?


texts:
I am looking for recommendations for a strong adhesive that would be easy to apply by hand in production quantities. This is for fastening an ABS plastic riser in between two PCBs.

Epoxy would work, but we would need to make sure the set time was long enough to prevent hardening too quickly.


texts: I have seen images online that show the current of electrons going from Negative to Positive in electrolysis with water but with my knowledge, the electron flow should flow from Positive to Negative. I am having issues finding out why this is which is why I have come to the Electrical Engineering side of this website. For electrolysis, is the flow POS ---> NEG or NEG ---> POS? Thanks and sorry for dumb question


texts:
Did not know where else to ask about this, so if it is off-topic I would gladly take some pointers as to where the correct place would be. I would like to make one of those spinning LED fans that can project an image that looks like a hologram. I am not looking for anything with big resolution, just want to try it out, see if it is possible.
So I have a couple of questions:

Is 30 Hz frequency for the fan enough to be able to see images without lag? I'm basing this off of the fact that 30 fps is needed for a video to be smooth for a human, so if a fan is spinning 30 times in a second, that means a human won't be able to see it?
If this is correct, would a 6VDC 340mA motor which can spin at 14400rpm (thats 240 Hz) be enough?
What LED density should the LED matrix on the fan be in order for the images be recognizable? Or is a LED strip a better idea?
I'm thinking that the controls should go to an Arduino. Is that at least possible? I think I should be able to divide a circle into 30 parts and control which LED's should be on in each section of a revolution.

EDIT:
Let's say I want to control an 4x8 RGB LED matrix (something like this https://www.adafruit.com/product/2945). I want to plot simple pictures like an arrow or a drawn cat face. While searching I thought the MAX72XX ICs would work for this?
The picture I think would be sent via USB (or something similar because MAX72XX support SPI) form the computer, one at a time.


texts: Current consumption by a LDO (5v to 3.3v)

texts: There is a LDO that converts 5v to 3.3v and has a quiescent current of 0.11mA. Suppose it powers a ultra low power digital sensor (i2c or spi based) that uses only 50uA, (there is an mcu too but that runs on 5V, the sensor's data lines are 5v tolerant but not the power lines) Then what will be current through the LDO, will it be in mA or uA ??


texts:
I made a simple window comparator like this:

I'm using LM293, R1 and R2 sets a Vlow and Vhigh threshold, when input is inside Vlow and Vhigh, both leds are off, when input is above or below, one of the leds turns on. This is working ok.

To reduce consumption i changed LM293 by TLV3402, but window comparator does not work anymore. When input is outside window, leds don't turn on.

Both ICs have the same pinout (i use the same circuit, just replace one IC by the other), why TLV3402 does not work? It is not a fault one, i tested with a second one, the same result.

Are these IC the same, or am i missing something?


texts: Can I damage a device using opposite polarity?

texts: I have a device that requires input of 12V DC with positive polarity and a power supply that outputs 12V DC negative polarity (see figures below). Can I plug it in to try to see if it's working or will that harm the device?


texts: ESD protection on perspex electronics enclosure

texts:
I've bought some high power electronics with some sensitive components. Since they are just bare boards straight from the manufacturer, I have constructed a perspex surround with fans facing the underside of the board. The manufacturer warns that they should be used in a static free environment. I wouldn't normally be concerned, but its a lot of moneys worth of gear.

Plastic is a 'magnet' for dust and grease and builds up plenty of static, especially when there are moving parts (the fans?). My rookie question is how do I prevent any build up of charge?

If I strapped aluminium tape to the side of the plastic case and wired a connected cable to the mains ground, would this help? The case is held together with nylon hex spacers, should I ground all sections of the perspex?


texts: Digital circuit for finding minimum vector index

texts:
I'm trying to design a circuit which finds the minimum value in a vector along with its index. I would like this to consume as little hardware as possible and when synthesised in an FPGA, have a good timing. I'm considering using a layered approach as shown in the figure below.

]1

I'm relatively inexperienced in designing tree/layered structures. Is this the best to go about this? I'm also uncertain how to pass in the index. Using a unique number would cause large multiplexers, using relative index w.r.t. each pair would need an adder.


texts: Stair like discharge voltage profile in AGM battery

texts:
please help:

I have a string of 14 AGM batteries in series, when discharged at constant current, the voltage has a stair-like shape with respect to time.

What does this mean?

The batteries are new but were stored for more than a year without charging. They were cycled again and the stairs "softened" a little.

The same stairs are also seen when charging begins.

Any recommendations to troubleshoot this (if possible) are very welcome.

Thaks for your help!

EDITS:

I've noticed capacity has reduced from 17Ah to 12.5Ah, and efficiency is arround 85% (2.46kWh in charge and 2.11kWh in discharge).
Peter , voltage jumps are more or less three steps each 5 V, this is aprox. 1.67 V per jump.
The graph suggested by Henry: y-axys is volts, and x-axis is time, each count means two seconds.


texts:
I am currently working on a project that involves designing some front end electronics that shape the charge pulse from a solid state detector (effectively a current source - I1 on the diagram). Our source produces a pulse that is about 10us long. The design is essentially a charge sensitive preamplifier, followed by pole zero, followed by two Sallen-Key filters in a low pass configuration that act as shaping. I have a circuit schematic  that works, however I should like the outcoming voltage pulse over the load (R13) to be longer. Currently, the pulse is semi-gaussian and lasts for about 200-300us. If I could double or triple this time it would work better with the readout electronics. I would also be interested to know if what i have done is correct, as I don't have a background in electronics so there may be bare faced errors in the design.

On final question on this topic is this - what is the best way to increase the height of the voltage pulse, while keeping the noise to a minimum? I can do this by changing R9 or R10, however I am wondering if there is a better way to do this.


texts: Equivalent baseband communication channel

texts:
I was reading on my lecture slides (I do not put them here since they are not in English) this statement about equivalent baseband channel models:

In typical wireless applications, communication occurs in a passband [fc W/2;
fc
+W/2]
of bandwidth
W around a center frequency
fc. However, most of the processing, such as
coding/decoding, modulation/demodulation, synchronization, etc., is actually done at the
baseband. Therefore from a communication system design point of view, it is most useful
to have a baseband equivalent representation of the system.

Since

it results:

and

and

I do not understand what it wants to get and why. Precisely:

what does it mean with "equivalent channel model"? I'd say that it means a channel with same input, same output, and same transfer function

which is the equivalent baseband channel model between the last two pictures?

So are baseband signal really used inside a channel?


texts: Problems understanding stepper motor data

texts:
I have a stepper motor (M061-CE08) here, and I am a bit disturbed: The manual tells me that it has eight connections, and winding specifications for bipolar parallel connection are 0.89V and 5.4 Amperes. The total current should be between 7.5 A and 8.5 A. Does that mean that the total current through all coils should be between 7.5 A and 8.5 A? If I want to control it, which parameter should I choose for driving it, i.e. should my design be able to deliver 8.5 A max. for all connections, or for each connection? Which is the highest voltage level I can expect when the resistance is at 0.16 ohms?
You can find the manual I get my information from here: http://www.techkits.com/SuperiorM06.pdf


texts:
I don't have much experience with electronics, I'm simply trying to get (at least what I think) is a fairly simple circuit running.

I've got a blower fan that I need to get running. It uses 12VDC at 4.3 amps. I've got a DC converter that converts 120VAC to 19VDC, but that's too high. I want to step down the voltage from the converter to around 12 volts DC, and I was thinking simply using a resistor might work, though I'm none too sure how the calculations are worked out. I tried an Ohm's law calculation and arrived at that I would need a 2ohm resistor for this, but I'm not sure.


texts:
I am working on an embedded Linux project that it is important to be sure that the file system won't be destroyed when some unexpected thing occurs (e.g., power failure during a write operation on SD Card). For this purpose, I am trying to implement a possible failure scenario.

I have read that there is sdctl for this purpose, but in the article, it says that it may take approximately 4 weeks, which is very long time for a single test.

Do you know, or think of, any good scenarios or special combinations (writing data to a certain place etc.) to speed up this fail process?

By the way, I also appreciate the "corruption-immune combination for SD card" ideas (e.g., using a journaling file system). Thanks in advance.

  Edit: Preventing (minor) data loss is not the priority for me. When
  corruption occurs, file system gets destroyed. So, I have to set the
  file system on SD card all over again, manually. This is what I want
  to prevent at least. And the question above is about setting a good
  test environment to shorten the test time.


texts: What is needed to conduct an Accellerated Life Test on rechargable batteries

texts:
What is needed to conduct a life test on a rechargeable battery for a 2way radio?
The chemistry is NiMH.  I have battery analyzer to tell me capacity of new batteries, but I need to figure out how to determine the longevity of the cells.

We are suspecting the cells for the batteries we purchasing are not lasting as long.  How do I prove it?


texts:
Here I have the image of a signal in the output of U2, and the output is shown in green in the graph(sorry for the poor quality). Highest value = 3.3V, Lowest value = 0V, sine wave, 60 Hz.

Now I have the same circuit but with that 1N4728 zener connected across and the output signal behaves like below:

The zener is working under low current(about 24mA) as its main Izt is Izt= 76mA, so I expected to have a voltage less than 3v3 as spice has shown.

Yet, the real question is I don't get the fact the zener is being able to clamp the output voltage without a resistor in series with it. In my understanding the zener should face the whole sinusoidal wave since there's no resistor in series to share the remaining voltage with. I tried that on real circuits with TL082 OpAmp and the same happened. I've also checked the TL082 output resistance and it's about 0.01 Ohm in the 60Hz range(which is the frequency of my signal), so that would for sure not be the trouble.

So, what exactly is going on in this circuit? Shouldn't a zener have a series resistor in order to clamp correctly?

Thank you for any help.