texts: Input and Output Impedance of a TTL NAND Gate

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Basically I wanna know how to calculate the input and output impedance of this basic TTL NAND gate I have looked at several books and websites but found nothing useful , can anyone help me please.
thanks in advance.


texts: What is the max current for a monophase RCCB?

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Images tagged with 1 are before the incident, and 2 after the RCCB burned off.
I am guessing that this has happened because of overload. What is the max current for this monophase RCCB?
I could also use some tips to prevent a future incident like this.

Whole breakerbox was replaced and the burnt cable cut off. The burn in 2nd image went halfway through the RCCB unit. Thats why I thought it could be because of overload. Am I wrong in assuming the max current should be lower than 40A?

Replacement was done by a professional, dont worry. I appreciate the good-will though. Thanks.


texts: what device should be used to measure the torque of 3 phase induction motor? The motor is of 3000 rpm or greater


texts: How to check protection circuit in lithium battery

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I've recently bought a single cell, 600 mAh lithium battery (like this one) and a TP4056 battery charger module, which I intended to use with the battery. The charger has an integrated protection circuit based on a DW01 IC with a 8205a dual MOSFET IC. I have already replaced the resistor connected to the TP4056 to limit the charging current to 500 mA.

I'm not sure if the battery has its own protection circuit. The guy that sold it to me didn't have a clue and I have found contradictory info in several websites. Is there a way to check if the battery has its own protection circuit (hopefully without having to push the battery to a condition where this protection would trigger).

My main concern is what would happen if I connect a battery with a protection circuit included to a second protection circuit. Would it work correctly?


texts: Transient Voltage Suppression Diode with no current limiting component

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BATT= 16V

27V Rated TVS Diode spec - TVS Diode Datasheet

The circuit :

My questions:

I want to understand what happens when the BATT voltage goes above the TVS diode clamping voltage. For both positive profile voltage and negative profile voltage.

My understanding, suppose, if the BATT = 50V. The D101 will be forward biased. The D102 TVS diode will clamp at 27V (its nominal rated TVS voltage). But won't this create a short circuit? There is nothing to limit the current through the D102 diode. Won't this circuit fail?

For negative voltage, the Diode D101 itself will block the voltage. So, the D102 will not face any voltage.

How to understand on the TVS diode behaviour during positive and negative transients in this circuit when there is no series element to limit its current?


texts: Quick Question about ohms law and resistors

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This may have been asked before, but I'm currently I'm an argument about whether or not passing 12v through a .1 ohm resistor would result in 120 amps due to Ohm's Law. (I=V/R)
Providing that the power source has a negligible internal resistance


texts: Connecting a 10 bit camera to a CPU with 8 bit camera interface

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I have 10 bit camera (MT9V032) that I need to attach to a processor that has only 8 bit camera data interface. (no LVDS) What is the best way to connect these two?

My current plan is to leave data 0/1 pins floating or pulled to ground with 10K resistor. The image will not have these bits but I suspect it still will be pretty good image quality. I want to ask experts if I am missing something?


texts: I2C Addressing after device address is known

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I have an I2C device that I know the address is 0x70 (probed when connected to Raspberry Pi using i2cdetect -y 1). My issue is that the bytes I want to look at need to be called in WiringPi. The output string is seven bytes long and WiringPi looks at the device address and then looks at the byte address I want to read.
That being said, would the addressing look like:

Device Addr.= 0x70:
   First Byte Addr.= 0x01
----or----
   First Byte Addr.=0x71

Does the address need a 'new' address identification (starting from 1) or does the address number get 'appended' (yes, I use that loosely) to the device address?

New Information:
I found this documentation after sifting deeper:
Upgrade Guide
and Short Communication Guide

It seems that from the upgrade sheet the slave's internal address for the address byte is 0xE0 for write. The command byte I want to use the command(#3.5): 0b000001100 (which I assume in hex is: 0x0C). It then seems that the address byte for read is 0xE1. From this point how would I read from the data bytes since their registers aren't explicitly shown (look at the Upgrade Guide)?

Here is my current code in WiringPi (C++):

#include <iostream>
#include <errno.h>
#include <wiringPiI2C.h>

using namespace std;

#define SLAVE_ADDR 0x70
#define DEV_ADDR_W 0XE0
#define DEV_ADDR_R 0XE1
#define DEV_COMMAND 0X0C //GET STATUS

int main(){
    int fd,writeRes,comm_res,readRes;
    fd=wiringPiI2CSetup(SLAVE_ADDR);
    cout<<"Initial Result: "<<fd<<endl;

    for(int i=0;i<1;i++){
        writeRes=wiringPiI2CWriteReg8(fd,DEV_ADDR_W,0);
        cout<<"Write to Address(write): "<<writeRes<<endl;
        comm_res=wiringPiI2CWriteReg8(fd,DEV_COMMAND,0);
        cout<<"Slave Command Acknowledge: "<<comm_res<<endl;
        readRes=wiringPiI2CWriteReg8(fd,DEV_ADDR_R,0);
        cout<<"Write to Recieve Data: "<<readRes<<endl;
        int readD_1=wiringPiI2CReadReg8(fd,0x0D);
        cout<<"Data 1, VOC= "<<readD_1<<endl;
    }

    return 0;
}


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Hello there at Electrical Engineering SE,

i am thinking about soldering a selfmade micro usb converter for my Acer Switch 10 tablet. After looking at the charger, i found out that it only needs 12 volt and 1,5 amps to charge (considering the tablet can be run while charging, the power requirements are very low). My goal is to make an adapter, so i can charge my tablet on any USB port or with my mobile battery.

In a RasPi project, i already converted 5 volt to 12 volt to power up and run a display. So boosting the voltage is no problem for me.

What i want to know is : considering i can already boost the voltage, do i have to boost the current to 1,5 amps or can i charge my tablet at a lower current without damaging the battery ?

Another question is : Do i have to take other security mechanisms for not to break the internal battery (Like capping the maximum input current to 1,5 amps) ?

Thank you in advance dor helping me making my tab more mobile.


texts: Differential-output op-amp vs. additional inverting op-amp?

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I'm wondering what the real advantages of op-amps with differential outputs are (e.g., AD8138), compared to just taking a signal V+ and feeding it to a unity-gain inverting amplifier to obtain a complementary signal V-.

simulate this circuit – Schematic created using CircuitLab

vs:

simulate this circuit

I have control over the single-ended input (it is the output of the previous stage of my circuit), and it's just that I want to convert it to differential to transmit it to an A/D converter that is on a separate board (and that offers the option of differential inputs).

Are there any advantages with using a differential op-amp such as the AD8138 --- or conversely, any important disadvantages with adding an inverter op-amp to get the complementary signal for the differential pair?

In case it matters:  my signals will be band-limited at 1 or maybe 2MHz.


texts: How to measure the maximum weight that a DC motor can move?

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We are working on a computer-controlled electric vehicle project which is based on an ATV chasis.

While I was looking for a DC motor to move this vehicle (which is estimated to be 350kg), I found an electric wheelchair motor. It is 500 W 108 rpm 24V DC motor and has its own differential. The salesman told me that it can move up to 540 kg. I don't know which fact this number is based on.

I also have a 500 W 1500 rpm 24 V DC motor. If I decrease rpm and increase torque with the same ratio of electric wheelchair motor via reductors, can it move up to 540 kg? Or does the max weight that a motor can move depend on another factors? How can I measure this?

Thanks in advance.


texts: Reducing signal noise arduino to simulink analog read

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I'm using an op amp to amplify the input of a pressure sensor from milli volt to volts using with arduino. Both the amp and the sensor are externally powered using a DC power supply.
I'm trying to read this analog signal off the arduino using Matlab Simulink, But I am getting a lot of noise while trying to read. I'm not sure what is causing the error, any suggestions?

I would need to read the voltage value so that I can make a lookup table from it ( relating corresponding voltage values to pressure values)


texts:
so I got a ups with a 12v lead acid battery that was constantly on so the water inside the cells has disappeared, initially the reading voltage was 0.3v, and when I added distilled water it generally started to go up by its own to around 3v ish.

now I am charging it, and its voltage is rising but slowly, and drops Mv moderately quickly. but what is supper odd is that it's not drawing any amps, from my bench power supply.

also to mention it's not able to go past 8v for now at least.

now, what is my question, why when I am charging the lead-acid battery it doesn't draw any amps? and is it really charging without drawing any amps?

my guess would be it needs to reach a certain voltage until it really starts to charge and hold capacity.


texts: How to "Mirror" or "Split" bar code data scanned by one USB scanner to two computers using Y cable?

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I have searched this site and many others looking for a way to "split" or mirror data from an USB device (bar code scanner) to two computers. We need to do a parallel cut-over from a legacy asset management system (whose interface, at each loading dock, is a LAN connected PC with an USB bar code scanner) to a Web application using a laptop with the same USB scanner.

Years ago I designed a RS-232 serial port Y cable that allowed the SMDR data from a PBX to go to both a data capture serial port on a computer and another device by utilizing signal diodes on each device transmit lead.The PBX transmit lead was split to each device's receive lead.

Not anticipating the firmware/software/timing and control logic involved, I thought all I needed to do was match a pair of diodes that would block the computers from sending or receiving data from each other, as I had done before. I've tried biasing the signal diodes with the T+ of each computer USB, to no avail. USB is much more technologically complex.

All the research I have read, so far, leads me to believe that I would have to design a "black box" which would interface between the scanner and the two computers. The box would look like a computer (host) to the scanner, a scanner to each computer, and thereby spoofing each component.

I hope that I’ll be able to find someone with a workable solution to this question.


texts: Why does there flows no current through the common part of the circuit?

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I saw there was a post asking the same question here but I still don't understand it.

I am reading the book Code: The hidden language of computer hardware and software and the book shows the following circuit:

where the red wires show the flow of electricity in the circuit. I don't understand why there flows no current through the common. Could someone please explain? Why doesn't the electricy flow like this:

So from the the negative terminal of battery 1, through the right bulb, and into the positive terminal of battery 1? Is it because the currents (the one coming out of the negative terminal of battery 1 and the one coming out of the negative terminal of battery 2) are exactly equal and opposite so they cancel eachother out?

If that is the case why don´t they cancel out in this image?


texts: What is the derivation for the error due to opamp open loop gain in this case?

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For an ideal opamp the unity gain buffer has a voltage gain of exactly 1; so Vin = Vout:

But if we neglect all non-idealities except the DC open loop gain Aol, how can we mathematically/analytically demonstrate the effect of the Aol to the error between the input and the output voltage? I have read once that if Aol=infinity then Vin = Vout but if Aol=10000 then Vin is not exactly equal to Vout. But I cannot derive myself why neither I can find a source in internet for derivation of this.


texts: Does the STM32F469I DISCOVERY board allows the user to perform Digital to Analog Conversion?

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I have a question on DAC (Digital to Analog Conversion) capability of the STM32F496I DISCOVERY board, which uses the STM32F469NIH6 (216 pins) microcontroller.

According to the microcontroller's user manual, the PA4 and PA5 pins provide the DAC function. Please note that PA4 pin can provide both the DAC_OUT1 and ADC12_INT4 functions. According to the STM32F469I DISCOVERY board's user manual, the PA4 is connected to the A5 pin of the CN8 Arduino connector. The function of the A5 pin is defined as ADC12_INT4 (Analog to Digital Conversion) and not DAC_OUT1 (Digital to Analog Conversion).

My question is :

Does the STM32F469I DISCOVERY board allow the user to perform DAC operations through the PA4 pin of the microcontroller (A5 pin of the CN8 Arduino connector) or not?

If yes, How is it possible to change the function of A5 pin from ADC12_INT4 to DAC_OUT1 on the CN8 Arduino connector of the STM32F469I DISCOVERY board?


texts:
So I have this RLC circuit:  And its equations for voltage addition, current conservation, ohm's law and a solution of those equations (Vo).

Then there's this RLC circuit:

With another set of new equations for current conservation and voltage addition, since a capacitor and inductor have been added in series with the resistor.

I want to obtain new equations for the current conservation, voltage addition and the solution (which is the output voltage Vo) to this other RLC circuit,

which is just like the 2nd RLC but with another resistor added in parallel with the capacitor and inductor. Thanks in advance!


texts: Has a CPU with Highlevel language (C/C++) as machine code ever been designed?

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I got a question popping directly from reading Tanenbaum's Structured Computer Organization.
Stating from Chap. 1 Sec. 1.1 :

A machine with C++ or COBOL as its machine language would be complex indeed, but could easily been built in today's technology.

And let's assume this strictly means that the language is actually the machine language.
Now, I understand it would be pointless to build such a thing, but I wonder if someone ever tried. At least as a soft-core.
Does something like this actually exists? This book is from 1998 so I guest today would be even "easier".
I'm asking this for pure curiosity.


texts: How an equation in s domain is converted into z domian using zero hold method

texts: I am just reading a research paper on matrix converter and i came through transfer function conversion from s domain into z domain. which i am unable to understand. how the equation 3.4 is transferred into 3.5 using zero hold method. can anyone explain step by step? attached is the screenshot.


texts: Sensing Light Differences in Photo-Resistors

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I'm planning to make a little device that detects when a path of laser light is broken. The device will have 3 photo-resistors and three corresponding lasers. Like so:

|-(PHR)    <---(Laser)
|
|-(PHR)    <---(Laser)
|
|-(PHR)    <---(Laser)

I know that the environment that this will be in has variable non-laser light, which may throw off the sensors. So I want to design the circuit so that a trigger is set off when one of the three resistors is substantially more resistive than the others. I can't seem to figure out how to implement this circuit though. Does anyone have any useful information for this? I understand basic DC and AC circuits, but I guess I'm a little rusty.

Edit: I'm assuming this can be done with passive components. Not that it's a strict requirement, but it's the reason I'm asking. If this can't be done with passive components, then it's suffice to say so or explain why.


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I need help with starting on the design of amplifier design project, given the following listed below specifications.

To be more precise, having learned about the different BJT amplifiers, such as the CE, CB, and CC amplifiers: How do I chose which one of the three and or in which order do I stage them, in order to accomplish the required specifications?

It is required to design a BJT amplifier that meets all of the listed below specifications.

The designed amplifier must be AC-coupled for the load and the signal source, but the coupling between its intermediate stages may be of AC or DC type, as per the designer’s choice. There are no restrictions in terms of using NPN or PNP transistors.

Note that there is no right or wrong design, as long as the aforementioned specifications are met.

The following below is a sample attempt at a possible solution.

Before starting to find a possible solution out of many possible combinations, and avoiding unnecessary calculations, I first started with an amplifier circuit with the amplifier block replaced by its equivalent-circuit model.

I found and identified the next following listed below parameters:

I am lost on how to continue this problem and find a possible solution.
I need help with finding a possible circuit design that can be analyzed using DC analysis and AC analysis, with their corresponding equivalent circuit models.

Here is what I got close to.

Now got a distortion.


texts: PIC getting each bit value of an integer value

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I need to send some integer value that is between 0 and 100 to another PIC by using 8 bits of PIC18F26K83. The problem is pins are from different ports not from the same ports. So I cannot follow a way like: PORTA = integer number.

bit should be sent to RC0.
"  ""      "   "   " RC1.
"  ""      "   "   " RC5.
"  ""      "   "   " RC6.
"  ""      "   "   " RC7.
"  ""      "   "   " RA5.
"  ""      "   "   " RA6.
"  ""      "   "   " RA7.

How can I make it from the easiest way? I couldn't accomplish it with bit shifting because I could not get individual bit by using that way except the first bit.

Edit: In C language and I use Micro C compiler. I thought I could make bitwise and operation but that might be unnecessarily long.


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What does "For secondary 4 wires of 24SWG in parallel" means?
Does it mean I take 4 wires and wound them 47 times in the primary side?


texts: Implementing LM339 comparator to count analog peaks

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Updates after applying Trevor's advice:
I have attenuated the output of the CPS to between 2 and 2.5 volts, as shown in the scope pic: , channel 2 is the constant "high" output from the schmitt trigger, which is not connected to any input in that screenshot.

the issue now is that when I connect the trigger input it drops the voltage way down and the scope looks like this:

I have absolutely no idea why it is dropping the voltage so much, any advice on what to change? see Trevor's answer for schematic.

original question below:

I am an ME lost in a EE world... Overall problem is need RPM input from an engine to an arduino for PID control. Went to the shack and picked up some stuff to experiment with. Seems that the LM339 should be able to pickup the peaks of the analog signal from the crank position sensor and output a logic signal that the arduino can count and convert to rpm.

I have referenced the TI datasheet and application guide [see figure 6] in my efforts so far. See attached schematic for my starting point. Also attached the scope reading of the analog signal from the cps.

My question is basically can this work or am I missing some fundamental EE reasoning? Input/advice on resistor values, decoupling caps, and the proper Vref value would also be greatly appreciated.

would not let me post links to the application guide or my search results, found some info on decoupling caps for IC's but not sure how to apply it to my circuit.


texts: How to calculate Junction to Ambient temperature of LED?

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I'm trying to calculate the Junction to Ambient temperature for this Cree LED:

https://www.mouser.ca/datasheet/2/90/ds--XHP502-1093532.pdf

I know how to calculate this:

Junction Temp = Junction to case + Case to Heat Sink + Heat sink to Ambient + Ambient

However, If I want to know what is junction to ambient temperature (aka no heat sink), how do I calculate this from the data sheet?


texts: Can I use a stepper motor driver to control a brushed motor?

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I'm doing a bit of shopping lately and I pretty much see stepper motor drivers everywhere, although I couldn't find any for brushed DC motors. I attempted to use a 2n2222 but it's probably a bad idea as it may will burn it out. Now, I found several small-sized stepper motor drivers that are perfectly sized for my needs, but I'm not sure if it can run these kinds of motors. Can a stepper motor driver run small, high-speed motors?

EDIT: The control that I'm talking about is speed control (50% from full speed, 37%, etc.)

These motors are what I'm talking about. 4v, more or less 1A

Thanks in advance


texts: I have this red hatched line around a button and Eagle shows an error for this. What is this error?


texts: Novice question: what are attributes in VHDL?

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What is the difference between constants and attributes in VHDL?

I know that both can be declared and later assigned value inside the instatination. There are some pre-defined attributes. Attributes are accessed with '. Both attributes and constants are seen only in their parent namespace i.e. where they are declared.

When is each used?

More specifically, I am trying to understand this code:

Entity TOP is
   generic (
      DMA_BUFF_SZ_BYTES       :natural:= 1024;                          -- buffer size in bytes
      DATA_SZ                 :natural:=16
   );
   port
   (
      n_flaga                 :in std_logic                            -- tx buffer is full
    );
   attribute syn_debug        :boolean;

   attribute syn_debug of     debug,
                              n_flaga   :signal is true;
End TOP;

What would those attributes be for? The name syn_debug is not used anywhere else in the project.


texts: 12V DC voltage drop for second switch 10 meters away

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I have a ground floor main door lock operated by a solenoid (12W, 12 V), the switch (push button) of which is located at first floor, the power to this switch is given by an AC to DC(12V) adaptor - Now I have installed a second switch on second floor of my house (@ 10 meters away from first switch) & is connected to floor 1 switch in parallel (stair case wiring) having supply taken from same AC-to-DC adaptor - but due to voltage drop, the second floor switch is not operative.
Can this issue be resolved by using 'Boost Converter' - if yes, how it should be connected in given wiring set up ?
Or is there any way to fix this - please help


texts: What kind of protection do these Ethernet "surge protection" diodes provide?

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I was considering a network run outside of my home, and purchased a super-cheap "Ethernet Lightning Protector" because there was little to lose, and I wanted to understand its workings.

Below you can see the insides after I'd opened it:

The first thing I noticed was the superb manufacturing quality (ahem).  As for the design, it appears to be just clamping diodes.

I was expecting TVS's, or perhaps varistors, but I want to say they're Zeners because of the typical clear-red appearance, but I wasn't sure if there were other diodes/components of that look. They have no markings on them other than the single red band in the middle.

Q1: Anyone care to say if these are for sure Zeners?

Q2: As for protection, what would this actually provide? ESD protection? Could this really be considered lightning protection?

Also I'm wondering how these diodes would help. I know Ethernet uses a differential signal... The diodes appear to have their anodes at the "shielding" of the jacks.

Q3: So this literally wouldn't do anything without shielded cable (STP)?

That being said, I've little experience with Ethernet hardware design.

Q4: It seems that "all" or most Ethernet devices use transformers, so can it be said that there is some protection already inherent?


texts: Running a solenoid pump with N-channel MOSFET

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simulate this circuit – Schematic created using CircuitLab
I'm trying to run a solenoid pump(L2 in the diagram) using a pulse generated by an Arduino. The pump is designed to run on rectified 24VAC, but the manufacturer says that running on a 24VDC 10ms pulsed square wave at varying frequencies works fine. Right now I have the pump set up in the configuration above. When I send my signal from the Arduino , I get no response. Upon testing the MOSFET with my multimeter, I found it to be no good. My question is, before I buy more MOSFET's, is this the best way to set up this circuit or are there better switches for this application? Is this the proper way to wire up my fly back diode? Is there a better way to protect my MOSFET? I apologize if I have not asked this question properly, I'm very new to this.


texts: All I want to do is send text to my Arduino and display it on an LCD Screen via Serial

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I have been working on this for hours and have no idea where the issue is...

So I have the following code...which when I type a letter into the Serial Monitor I get the binary code for that letter on my LCD Screen...

#include <Adafruit_CharacterOLED.h>
Adafruit_CharacterOLED lcd(6, 7, 8, 9, 10, 11, 12);
void setup()
{
    // Print a message to the LCD.
  Serial.begin(9600);
  lcd.begin(16, 2);
}

void loop() {
  char TestData;
  if(Serial.available() )
  {
    TestData = Serial.read();
    lcd.setCursor(0, 0);
    lcd.print (TestData, BIN);  // echo the incoming character to the LCD
  }
}

The issue I am having is, how do I then convert the text from either BIN or HEX or some other ASCII code to literal TEXT...

I have tried leaving the lcd.print as simply lcdprint (TestData) because then it should return just the VAL of the input but it does not, it gives me a few weird symbols and then turns off...Like something is wrong

I also need to then figure out Char Arrays but Ill get to that once I figure out how to display a freakin LETTER

EDIT:
https://vimeo.com/61851351 This is video of what of comparison of lcd.print (TestData, BIN); vs lcd.print (TestData);

Per the last comment the follow works as expected:

#include <Adafruit_CharacterOLED.h>
Adafruit_CharacterOLED lcd(6, 7, 8, 9, 10, 11, 12);
void setup()
{
    // Print a message to the LCD.
  Serial.begin(9600);
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  char TestData='X';
  lcd.print(TestData);
}

void loop() {
  char TestData;
  if(Serial.available() )
  {
    TestData = Serial.read();
    lcd.setCursor(8, 0);
    lcd.print (TestData, BIN);  // echo the incoming character to the LCD
  }
  lcd.setCursor(0, 1);
  int charcode = 65;
  lcd.print(charcode);
}


texts:
I'm hoping to build a simple bluetooth buzzer using a Serial Port BLE module: HM-10. When a slave connected to it, if the slave sends a certain predefined message, the buzzer sounds for one minute.

The HM-10 has PIO pins, so I'm guessing I could use one to power the buzzer. To control the buzzer (or the pins, in general), read the message, etc., would I need to reprogram the HM-10 entirely? That is, the AT interface should be no good and the HM-10 will need to be flashed - is that right? If so, what is the canonical approach to programming it? How about the CC Debugger?

Thanks


texts: Soldering iron tip turns black after first use, and won't melt solder

texts:
I am a beginner in the field of soldering.  Two weeks ago a bought a brand new soldering iron for around $15.  The iron had a shiny tip, but after I plugged it in it turned black pretty quickly.  After doing some research, I found out that this type of soldering iron is made of a copper core with a thin iron coating.  The iron coating is needed because, to my understanding, copper corrodes quickly when in contact with hot solder.  However, at high temperatures, iron reactas with oxygen and forms a super thin oxide layer on the tip of the soldering iron, which makes soldering really difficult.

Essentially, the solder melts only at the top of the tip, and starts rolling into a ball.  It will barely melt at the absolute tip.  I have tried using a wet sponge to clean it off, as suggested by the internet, but that doesn't do anything (the sponge is apparently supposed to be used to clean solder rests from the tip and not oxidation anyway).  Another internet tip was to gently scrape that layer off with a knife until the iron covering is revealed, turn the soldering iron on, and once it heats up immediately cover it with solder to prevent oxidation.  Well, I tried that too, but as soon as the iron heats up, it turns black and repels the solder.

I have heard about using flux (soldering paste) but my solder already has a flux core.

In the two pictures you can see the iron before/after being turned on, (after I had scraped it with a knife).  You can clearly see how it loses its shine.

How do I remove this oxide layer without a knife (which risks damaging the iron coating) and prevent it from reoccurring?

(To reiterate, I am a beginner, and I don't want to spend $100 on a fancy, temperature controlled iron.  I just want to solder some components to a thru-hole board without buying a new tip every time in need one.).

Thank you very much for your time!


texts: transfer function op amp feedback circuit

texts: Does anyone know how to calculate the transfer function for this circuit if Vref is the input an Vo the output? Thank you


texts:
(First, sorry for my English :_D)

I'm doing a school project and I wanted to swap a male/plug USB-C to a USB-C female/receptacle. I thought it was just soldering the cables onto the board and it's ready to go, but that didn't work.

I bought this USB-C female board: https://www.amazon.es/gp/product/B00VRAZMVE/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

If you can see, the A4, A9, B4, B9 (also Vbus) connectors don't exist, but the adapters I am also working with them they don't have any extra cables that I couldn't solder.

My problem is that I want to use a male-male USB-C cable to connect the adapter to my computer but that doesn't work in any way. As I read, the USB-C connector has some cables to communicate to the master device and provide energy, so the cables I didn't solder are the Vbus ones.

Is there any way to use this adapter with a male-male USB-C cable?

EDIT: I noticed that the board itself is capable of soldering the Vbus connectors, but in the adapter there isn't an extra cable to do that, should I put a jumper or something similar?


texts: Output data from computer to light up LEDs

texts:
I'm a complete newbie at this, but the idea is to have a circuit board with, say, 10 LEDs, connected via USB to a computer running Linux. This will periodically (e.g. every second) send data to the board telling it which LEDs to light up. What the lights represent will be flexible, decided by the computer.

I'm considering using an Arduino, but I'm also open to another route if possible.

Any recommendations on where to start? Thanks!


texts: Current rating for 12v plug on 300W in-car inverter

texts:
I have an in-car inverter which is rated 300W.  This is the only labeling:

I need to source a 12V cigarette socket plug to connect to the input.
I have found the following one which is labled:  Carpoint Universal plug 6-24v max 8amp

Assuming I have a 12V car power supply, would the 300W rating on the inverter, suggest that this plug would have an insufficient current rating:
P = IV
  = 8 * 12
  = 96 Watts

Or should I be calculating based on the 230V output device connected:
I = P/V
  = 300/230
  = 1.3 Amp

Of course, with the latter calculation I'm unsure if this applies exactly to the inverter's input.


texts: Depletion Mode MOSFET Modelling in SPICE

texts:
Does anyone know how to model a depletion mode N channel MOSFET in spice?

I have looked online however the majority of resources have shown how to model a depletion type or enhancement type. I specifically want to model a FET that is fully on when there is a 0 Vgs voltage.

Resources i've looked at

A forum
A help link


texts: Is this a well-implemented power supply for driving logic from a LiPo or NiMH battery?

texts:
I'm designing a power supply for a system which requires a 3.3V logic power rail, driven by a user-selected battery.

My requirements are as follows:

Input voltage between 7V and 18V - usual batteries are 7.4 / 11.1 / 14.8V LiPo, or 8.4 / 9.6V NiMH. Some users may choose a 9.9V LiFe PO4 battery, but this is unusual.
3.3V output (AP1509-33's tolerances are acceptable).
1500mA continuous, 1800mA peak.
Quiescent current < 25mA.
Reverse voltage protection.
Overvoltage protection.
Inrush current limiting on the 3.3V side (due to C4 on design below).
Delay-start to ensure stable voltage is available on startup.
Battery voltage sensing (via microcontroller ADC).
Regulated voltage sensing (via INA219 power monitor IC).
Overcurrent and overheat protection with redundancy.
No replaceable fuses - polyfuse only (although many users will install a standard inline cartridge fuse anyway).
Small design footprint.

Here are my schematics:

Datasheets:

U2: AP1509-33 150KHz, 2A PWM BUCK DC/DC CONVERTER (3.3V Fixed)
Q1: FDD4141 P-Channel MOSFET: -40V, -50A, 12.3mΩ
D1: 1N5822 Schottky Diode
D3, D4: 1N47xx Series Zener Diodes
U5, U12: INA219 Zero-Drift, Bidirectional Current/Power Monitor With I2C Interface

In the schematics above the ground net is directly connected to battery negative.

Both F1 and F2 are polyfuses. F1 has a trip time of around 4.0s at 750mA, dropping rapidly at higher currents. F2 is a very fast polyfuse with a trip time of one second at 2000mA. I can't find the exact datasheets or part numbers for them right now.

I used a P-channel MOSFET for reverse voltage protection rather than a diode for efficiency. The FD4141 was selected simply because it's the cheapest MOSFET I found that has appropriate voltage and current ratings and a low Rds(on).

D4 is intended to shunt current once BATT_PP exceeds 20V, quickly tripping F1. This should cover overvoltage scenarios.

The voltage divider and zener arrangement (R2, R3, D3) produces a sense voltage which directly drives an ADC pin on a microcontroller. At BATT_PP = 20V, D4 starts to conduct and VSENSE never exceeds around 3.2V. Below this there is a roughly linear relationship between BATT_PP and VSENSE. I'm using this as a cheap initial "voltage ok" check before powering on peripheral devices.

As per the datasheet, the arrangement of C5 and R1 on the shutdown (SD) pin of the AP1509-33 causes a soft-start and should limit inrush current on the 3.3V side.

L1, C4, and C9 are chosen based on the datasheet and standard advice on power supply design. D1 was chosen based on some other circuits I found online, as the datasheet was not very helpful in this regard.

The remainder of the circuit shown is simply a pair of INA219 power monitor ICs which provide more accurate monitoring of the system voltages. An alert is sounded if expected ranges are exceeded. My design does not currently allow for automatic shutdown of the power supply, although the AP1509 itself has overheat protection built in.

Does this design look ok? Do my decisions sound sane? Are there any improvements you might make?

EDIT:

Some errors spotted by a friend on Twitter:

The battery voltage sensing resistor (R9) should come after Q1, not before it, because the INA219 doesn't support reverse voltage sensing.
D4's surge current limit is 250mA, which is insufficient. I'll replace it with something with a 2A+ current rating.
F1 and F2 aren't 0805 package, they're 1210.

They also pointed out that it's probably worth using tantalum caps for C4 and C9 due to their lower ESR. This seems sensible.


texts:
I have an op-amp circuit that has a block of dip switches that can be used to configure the gain of the circuit. We have had an unusual failure in the circuit that appears to be related to changing dip switches while the unit is powered on. This failure only seems to occur on occasion.

My suspicion is that the issues is caused by the switches being set they pass through a state such that no switch is turned on but have no evidence at this. In addition I would that expect that if all switches are left open this is effectively becomes a voltage follower and should try to drive the voltage to zero volts.

This is a simplified version of my schematic OPA1 is supplied from +- 15V rails, Input voltage is +-10v In- is connected to zero volts in a separate section of my circuit. The output load is a second amplifier stage and would present a load of approximately 100k

simulate this circuit – Schematic created using CircuitLab

Is there anything that adjusting these switches could do to destroy my op-amp to the extent it releases the magic smoke and leave a small crater in the surface of the op-amp.


texts: Activating Electronic Speed Control with Arduino

texts:
For anyone else looking at this, most of our problems seemed to result from not having the pulse range quite right. We eventually hooked our ESCs up to a standard RC controller and used an oscilloscope to figure out the exact pulse range they would respond to.

I'm working on an Arduino-controlled quadcopter using Tower Pro W18A (which are actually labelled Toward Pro). I'm using the Arduino Servo library to control the ESCs ( Electronic Speed Control).

The problem is that the ESCs don't start responding immediatley. There is some sequence of throttle commands that has to be sent before they will turn on and begin responding to commands.

At first, I created a program to let us set the value being sent to the speed controllers manually from a slider. Using this, I've discovered that starting at 0, sliding up to around 70-90, and then sliding back down to zero activates the ESCs. After that, they respond normally.

For some reason, I haven't been able to replicate this in code, though. This is what my code looks like at the moment.

  Serial.println("Setting all to 0...");
  setAllESCs(0);
  delay(2000);
  for(int i=0;i<70;i++){
    setAllESCs(i);
    delay(20);
  }
  for(int i=70;i>0;i--){
    setAllESCs(i);
    delay(20);
  }
  delay(2000);
  Serial.println("Ok, trying at 50...");
  setAllESCs(50);
  delay(500);
  Serial.println("Going in 1 sec...");
  setAllESCs(0);
  delay(1000);

I've tried several variants. 0 to 90 to 0. 0 to 180 (max) to 0. 0 sliding up to 90 and back to 0. No luck yet.

Does anyone have experience with getting this activation of the speed controller to work?

There are numerous mentions online of the (limited) documentation that comes with the ESC being wrong, but nothing providing more detail about this.


texts: How to scan for all available beacons with BLE?

texts:
I'm working with a project which involves Bluetooth Low Energy beacons. Super simple schematic will just broadcast an unique number of the beacon. These beacons are used in a warehouse which is about 100 x 100 meters, with possible expand to more and bigger warehouses, and they are used to identify cartons.

We plan that operator will carry iPhone 4s/5, where our small application would scan BLE channels, find our beacons and collect numbers.

However, there is one thing I cannot grasp. There is an Advertising mode in Bluetooth LE specs, with the summary like this: "An advertiser uses the advertising procedure to perform unidirectional broadcasts to devices in the area. The unidirectional broadcast occurs without a connection between the advertising device and the listening devices. The advertising procedure can be used to establish connections with nearby initiating devices or used to provide periodic broadcast of user data to scanning devices listening on the advertising channel. The advertising procedure uses the advertising physical channel for all advertising broadcasts."

So, as far as I understand, we will have to include some header information to help our app differentiate "our" BLE beacons from other BLE advertising devices around. Is it overall possible to just periodically scan the channels and read beacon data? Or is it like "old" Bluetooth so we will have to introduce all beacons to our devices first before it will be possible to read data from them?..

Also I wonder how much beacons would it be possible to read in, say, 10 meter radius in, say, 5-10 seconds?.. There may be about 500 beacons in this radius.

Opinions and suggestions are very welcome.
Thanks.


texts: How do I find voltage value at the a node point in the schematic?

texts:
As one can see that a circuit of DC to DC buck converter (Vin = 100-120 ,Vout = 5V,Iout = 2.5A) is shown which is obtained from Texas instrument's webench software for schematic .

As per the datasheet of UCC28C40 PWM controller specifications, the VDD should be 18V.

But as you can see from the schematic, Vx=Vin-Vaux . Vin is 100 to 120 Vdc ,Vaux should be around 20 V. Also,there is zener diode D12 which has breakdown voltage of 18V. So as per my calculations Vx comes out to be 100-18=82V. But  for ucc28c40 to work VDD must be 18V.

So can anybody tell me where am I getting wrong in doing calculations? what is the right value obtained at Vx?

NOTE:I have tried to simplify the concerned circuit by neglecting other components. Here, Vaux is the voltage obtained from auxiliary winding.


texts:
On my project, I plan to have a user configurable setting set using a switch. Unfortunately, it looks like I don't know how to read from a port.

I'm using PIC18F4680 and C18 compiler.

Here's the picture of the circuit:

Circuit description:

The pin 19 is set as high and resistor R3 is set between pin 19 of the PIC and pin 3 of the switch. Pin 20 of the PIC is connected to the pin pin 2 of the switch. Pin one of the switch is connected via R37 to the circuit ground. Using a multimeter, I can see that when the switch is set so that the switch's pins 2 and 3 are connected on the PIC pin 20, there is at logical high voltage (around 4.96 V). When the switch is set so that switch's pins 1 and 2 are connected, I can see that the PIC's pin 20 is at logical low voltage (around 40 mV). The pin settings are exactly as shown below. As far as I know, on this PIC there are no internal pull-up resistors on port D.

Pin 19 is RD0 on this PIC and pin 20 is RD1 on this PIC.

I've set the RD0 like this:

TRISDbits.RD0=0;//Set as output
LATDbits.LATD0=1;

and RD1 like this:

 TRISDbits.RD1=1;//set as input

When the switch is set so that the RD0 is connected to RD1, I can read 4.96 V on the RD1 pin, so after reading, I should get high value. Unfortunately, when I read it using this code:

PortD1=PORTDbits.RD1;

where PortD1 is a char.

I always get PortD1 value of zero, no matter in which position the switch is.

I'm not using any of the devices which are multiplexed to pins RD0 and RD1.

So what am I doing wrong here?

UPDATE 1:

I added

CMCON = 0;
TRISEbits.PSPMODE=0;

to the start of my program, so comparator and parallel slave port should be disabled and shouldn't interfere with port D. Also I'm not using hardware PWM, so it shouldn't be causing problems.

UPDATE 2

On this chip, I'm using port E to drive an 8 bit multiplexer, which is working correctly. The strange thing is that when I try to read status of port E, using

PortD1=PORTE;
PortD1=LATE;

I get zeroes both times although I know that the value isn't zero. So it looks like the problem isn't specific to port D.

UPDATE 3

After some more testing, I was unable to repeat the problems with reading LAT registers. It seems that they are read fine now.

UPDATE 5

After doing some more testing, it appears that ports A, B and C provide results same as LAT A, B and C registers. Ports D and E always read zero, no matter what is written into their LAT registers. It turns out that port E was zero because it was set as analog input. After setting ADCON1bits.PCFG=255;, port E works now.

UPDATE 6

I've also disabled the ECCP module using ECCP1CONbits.ECCP1M=0; and it didn't make any difference. I've accounted for all multiplexed modules on port D and they are all disabled.


texts:
I need a favor
I was trying to recreate this circuit but apparently for some reason, it doesn't work. The idea behind this project is that when the user makes a phone call from his phone to the phone, which is attached to the circuit, the load gets activated. Similarly, to turn off the load, the user need to again make a phone call.
In the diagram, the LED in the phone's keypad is attached to the circuit. (I stated this because I don't think it's clear from the diagram)
Can you guys please tell me if the circuit is correct or not and if not, can you please provide me with the correct circuit diagram? And please try to make it as similar to the previous circuit i.e., similar type of components.
Thankyou.


texts: Can the acetic acid base silicone sealant damage the lacquer layer of the enamelled copper wire?

texts:
I know that acetic acid silicone is not the best choice for electronics.
There is a passive audio crossover with large air core coils (70mm diameter, 20mm hole in the middle) .The coils are glued with acetic acid silicone. The board is in a vented box.
The first question:
Can the acetic acid that may be trapped under inductor, damage the lacquer layer of the copper wire and then the copper over time?
The second question: Is acetic acid silicone corrosive even after curing?
Thank you all for your replies!


texts: Boost converter, how does diode allow current from inductor to flow towards capacitor?

texts:
So I watched this video to understand how DC-DC boost converter works.

Here's circuit diagram:

And I don't get, when switch is off, and polarity in the inductor is such that positive is on the right, negative is on the left.

Then in order for diode to conduct, anode should be at higher potential than cathode. In other words, voltage across inductor needs to be higher than voltage across capacitor.

Now video said, there's gonna be a spike in voltage in the inductor after switch is off due to collapsing magnetic field to keep current constant, but how big is this spike? And wouldn't charge, and therefore voltage across capacitor be so big, that the spike in inductor will no longer be higher, so diode would not conduct at all?

Correct?


texts:
How do I send a pattern into an 8x32 LED matrix? I'm using the AT89S52 microcontroller with a 74HC154 4-16 line decoder, programming in C with the Keil IDE. I've done vertical scanning, but am stumped at the next step. I will include the schematic if needed. The circuit is the same with the one I include below only I don't use 74HC138, common anode matrix and I use UN2803 as a driver, I'm not using the memory

Port 1 is the column, port 2 is the row...the code :

 row = 0xFF;
     //for (j=0x01; j< 0x08; j<<=1)  {   /* scan left to right */
     for (j=0x00; j<=0x0F; j++)
     {
          E1=0;
          E2=0;
          P1 = j;
          P2 = row;
                                   /* Output to LED Port */
          for (i = 0; i < 100; i++)
           {  /* Delay for 100 ms */
              delay ();                       /* call delay function */

           }


texts:
I am trying to get a 74HC14 hex  inverting schmitt trigger to work. First thing I did was connect it to a power supply.

When I connect the Vin and Ground ports to my bench power supply (5V), some noise is added on the 5V signal. See the figures. The first figure just shows the 5V from the power supply without the schmitt trigger connected. The second pictures shows the situation after connecting.

I tried a few different ones, but they all give the same result

Am i doing something wrong here. I intend to use the trigger to clear up noise from a signal, not to add noise.

Any idea is appreciated.


texts: Potential issues with mounting tiny PCB directly to piezo transducer?

texts:
I am designing a very small signal conditioning daughterboard with the intent of mounting it directly underneath a cylindrical piezoelectric force device/"sensor" to rectify and filter the differential voltage generated across the two pins.

The piezo device is about 60mm in diameter, and the PCB will be near the same with two through-holes for attaching the piezo device.

Thus, from the "top down" view, the footprint of the PCB will not add any new area, rather be directly under the transducer.

Having selected EMF hardened components as well as other common practices like copper pour, do you think this physical design has any glaring issues from a signal standpoint?

The transducer generates a fairly large signal at around 1.5Vpp. my main concern is some sort of capacitance issues being so close to the transducer.


texts:
Ok, please bear with me I am relatively new to the electronics scene.

I am trying to reverse engineer a pump controller.  Basically there is a switch that connects 12v to the pump to make it run and a lead that is connected to some kind of processor and a GPS that will increase the flow rate of the pump as the GPS detects a faster speed. I am trying to figure out how the second lead communicates with the flow regulator.

I was assuming from research that a simple pwm signal would be used to control the pump's output but that does not seem to be the case after connecting an oscilloscope to it.

Can anyone tell me what kind of a signal this wave may be so that I can research it?

Also, not sure if it is the oscilloscope (it's new for me) auto scaling or something else, but the pattern will slowly scale down in size over time.


texts:
I am working on Control of Power Converters, I was reading TI's piccolo DSP ePWM guide and came across symmetric vs asymmetric PWM, I have a good basic understanding about converters, DSP and all.

My question : According to ti's note http://www.ti.com/lit/an/spra278/spra278.pdf [page 10] symmetric PWM generates less harmonics, Can anyone please explain How?
Thanks


texts: Using 2x CAT6 cables for 3D Printer Hot End

texts:
Question was previously posted on 3D Printing Stack Exchange who recommended that I repost my issues here.

I'm looking to replace the troublesome ribbon cable of my Duplicator 6 with a 2x CAT6 arrangement for all things extruder.

I wasn't paying attention when I bought my cable and got 26 AWG cable instead of 24 AWG, I think signs are pointing to me needing to get better cables (CAT6a?) if this idea works at all.
How many CAT6 wires do I need to dedicate to the hot end 50 W at 24 V?
Can I consolidate ground connections of the low power fans/sensors to free up more wires?
Is it okay if I have some pins carry 24 volts (like for the heater) and others carry 12 volts (for the fans)?

EDIT: Updated table to show proposed changes to pinouts. I've obtained 24AWG CAT6 stranded cables to maximize my ampacity.


texts: Choosing an accelerometer for collisions

texts:
I currently have an ADXL345 accelerometer.

For a project, I need to be able to detect if my device has a heavy collision with a wall / hard surface. I need to trigger other events on a big collision. Which accelerometer with a range up to 200G would be the best? ADXL193? I'm using an Arduino Uno, so i'd prefer if it could easily be integrated with existing library/ code.


texts: Why isn't the current split between the transistor and the LED in this NOT transistor circuit?

texts:
In the following NOT transistor circuit diagram, the current flows through the 1K resistor and through the LED when the switch is open. This turns the LED on. When the switch is closed, however, the transistor turns on and the current flows through the same resistor, but bypasses the LED, turning it off.

Why isn't the current split between the transistor and the LED? Why does the transistor path get all of the current when the switch is on? Shouldn't there be some current flowing through the LED as well? Why is it being starved of all the current? What would happen if we moved the 1K and placed it in series with the LED? Would it cause a short circuit? Let's say you replaced the transistor, the switch and the gate resistor with a small resistor. Would it split the current then?

I prefer a math-free explanation using analogies since my working memory isn't optimized for it. In other words, my brain has a slow ALU and a tiny set of small registers.


texts: OpAmp circuit with diodes: conduction conditions

texts:
Consider the circuit below, where \$\ v_2\$ is an arbitrary input voltage and not necessarily equal to 3V as in the image. Both diodes and the OpAmp are ideal.

If only diode 1 is conducting or if both are, the output voltage, \$\ v_0\$, would be given by $$ v_0=v_2 +2V$$ If only diode 2 is conducting the output would be $$ v_0=2v_2$$ those two results where obtained by application of the standard rules (negative feedback, infinite input impedance...).

What I can't figure out is for which values of \$\ v_2\$ each situation is verified. According to the solutions the first situation is verified for \$\ v_2\leq 2\$ and the second for \$\ v_2\geq 2 \$.


texts: Custom Arduino board beeps and process freezes while I'm uploading firmware to it. Why?

texts:
The strangest thing is happening to a standalone Arduino board that I've designed and built. The board (whose schematics are below) has the following features:

It has an ATmega328P with a 5V voltage regulator.
It controls a scoreboard with several 7-display digits linked through the connectors on the right (JP1 through JP12).
It has cursor buttons decoded using a voltage ladder through ANALOG_0 (A0).
It has a Real Time Clock to keep time when the board is turned off.
It has an RF receiver module.
It has a UART header (JP17) so I can program the board using a serial port.
It has a speaker attached to digital pin 3 (D3).

I upload firmware to it using a RS232-to-TTL adapter that I've also built (schematics also below) and a Serial-to-USB cable. When programming it, the board behaves much like an Arduino Severino board.

What's strange is that, when I upload the firmware using Arduino IDE 1.03, the process is paused in the middle and then the speaker starts to beep continually. It just sits there waiting for me to do something. When I press reset on the board, the beep stops, the upload continues and the firmware is uploaded successfully to the board.

So, my questions are:

What is making the upload process pause?
Why is the buzzer beeping when the process pauses?

PS. This is a cross post from the newly created Arduino private beta site, but I thought that the question would be on-topic here, too.


texts: Is it worth worrying about propagation delay differences when dealing with relatively slow protocols like I2C @ 400kHz?

texts: At the moment I'm working on a system which will use a 400KHz I2C bus. The bus wires (SCL, SDA) are different lengths by a few cm, so the delay between them will be in picosecond to nanosecond range - I don't think I need to worry about this but am I misguided?


texts: Why is Rack Mounted Step-Up Transformer Not Industry Standard?

texts:
I'm tasked to source a 1U step up transformer so that customers with only 120 VAC mains power can utilize 240 VAC for our products.

I've contacted TrippLite and APC who both offer a 2U (2 rack unit) form factor of step down transformers for 240AC input -> 120AC output (they're the only ones I could find that provided any form of rack mounted transformers).  In chatting with them, they've given me a short answer that "step up transformers in this form factor is not an industry standard as it's easier to step down the incoming voltage.  It also has to do with the wave form".

I come from a mechanical background and interpreted that as "there are physical/electrical component limitations to creating a step up transformer".

Can someone elaborate on why it is would be easier to develop a step down transformer in a 2U form factor vs a step up transformer?


texts: Supplying NTC by different voltage from VCC

texts:
I would like the sense a material temperature that is located outside of panel. My NTC thermistor is 10meter far from my STM32 MCU based control board. I don't want to use VCC at outside of the panel because there are alots ot motors and noise sources.
MCU is energized by 3.3VDC and my panel have 24VDC. So I want to connect 24VDC to top of NTC.

My questions are:

Using more voltage divider resistors to decrease Vout to 0-3.3V range
is enough? If yes, how can I connect grounds while keeping isolation?

For better way How can I make true isolation between MCu and Vout of thermistor


texts: Fringe field effect: calibrating vs guard electrode

texts: Which method is more effective at limiting errors associated with the fringe field effect when performing a liquid conductivity measurement, using a guard electrode or using a reference liquid to calibrate the measurement. Is it even worthwhile using a guard electrode?


texts:
I am trying to solve a Sedra/Smith problem involving NMOS transistors. Given that both transistors are biased at the same point. Question is to find \$g_{m2}, i_d, v_{d1}\$ and the value of \$R_D\$ for which \$v_o\$ is pulses of amplitude 1V.

However I can't manage to find the value of the voltage pulses at the drain of \$Q_1\$ I actually found the solution manual for the corresponding text book, however I think that the solution is not well implemented as it suggest that the solution would be determined by: $$V_{D_1}=i_{D_1}50\Omega$$ which have no sense.


texts: Notation for switches in ladder notation

texts:
I was reading https://www.allaboutcircuits.com/textbook/digital/chpt-10/monostable-multivibrators/,

and at the bottom of the page it has

I read their page on switch notation, but it did not say what the arrows, like the weird one for TD1 means. So what is the difference between the switch TD1 and TD2 on the second line?


texts: Exceeding Maximum Voltage Rating of a BJT Transistor

texts:
I am wondering how the maximum voltage ratings of Vce and Vcb work for BJT transistors.

Are they like MOSFETs in the way that the instant the maximum voltage is exceeded, they are damaged/destroyed? Or are they different in a way that there is some sort of pulse rating for them?


texts: How durable is the insulation on magnet wire?

texts:
I'm planning a light sculpture.  It will consist of a large number of RGB LEDs mounted on a tree-like galvanized steel frame.  Each LED has four wires -- GND, +5V, data-in and data-out.  For aesthetic reasons, I would like to use magnet wire to connect the LEDs, intertwined with the steel frame.  So if one looked closely at the sculpture, one would see a twisted bundle of thick steel wire (non-conducting!) and several strands of conducting magnet wire.

I'm worried that the thin insulation on the magnet wire might wear off and cause a short circuit, either with the steel wire frame or with other lengths of magnet wire.

How much jostling/rubbing/abrasion can magnet wire take before the insulation is compromised?

Once the sculpture is complete it will not be handled very much, but during assembly there could be a fair amount of jostling.

[edit] I know there is no way to give a precise answer.  I was looking for something like "I've done project XYZ which subjected magnet wire to a certain amount of abrasion, and based on that experience I would guess this project will [or will not] work."

Also, I should have specified that I plan to use magnet wire with multiple coatings.


texts: Maximum operating temperature of power supply

texts:
I am using a 12V (1A) SMPS power supply to power up a device that draws about 70mA when idle and up to 200mA when active (every 3 seconds).

The power supply is getting pretty hot (about 70°C) after 1 hour of operation. I own several of these power supplies and all if them seem to have the same issue. How can this be avoided? Is 70°C a safe temperature for the operation of the components on the power supply like the transformer, etc.?


texts: Altering PWM on four pin fans using only transistors

texts:
I have some high RPM 4 pin Tacho PWM fans, they run at 6000RPM and 56.5 DB at 100% duty cycle the noise is enough to drive you insane - there are seven of them total running off of a SAS backplane, they absolutely do not need to be running this fast but the speed control values are burnt into firmware on the backplane.
I have experimented with one of them and found that noise is virtually eliminated by running them at 2400 to 2600RPM and they still push quite a reasonable amount of air.
What I am wanting to do is continue using the hard coded values being feed out to the fans and have all signals operating as normal so that the backplane does not know that anything has changed and thinks that what it is feeding out is actually what is happening but at the same time use NPN transistors to reduce the PWM signal down to the levels mentioned while still returning faked correct values to the backplane.
I am not offay with electronics and I think this acheivable, I would like to keep it as simple as possible as there is no way on this or any other planet that I would be able to surface mount components my skills with soldering and my steadiness aren't that great.
Can someone please help me out with what I need to do to acheive this.
TIA.


texts:
Noob question, but I'm not seeing how an SR latch such as the one in the image can "get started". If each input depends on the output from the other, how can there be two inputs to each gate to set the thing in motion?

In a rudimentary circuit consisting of exactly one NOR-based SR latch, what happens when the power is switched on (e.g. battery connected)?


texts: why my laptop can't use wireless charging technology?

texts:
we start to deal with wireless charging technology in recent years with the booming of smart phones
why wasn't it possible with laptops?
does the smart phone's battery differ from laptop's?


texts: how to place decoupling capacitors on a four-layer board for through-hole components?

texts:
From what I've read online, for SMT components there should be traces from VCC/GND pins to the capacitor and then vias to the ground and power planes.

The situation is a bit different for through-hole boards, because the VCC and GND pins will be directly connected to the ground and power planes. In this situation, are traces to the decoupling capacitor even needed? Can the decoupling capacitor not be placed close to the chip and simply connected to the planes with vias?


texts:
I'm building an H-Bridge to drive some motors I have around.
I'd like to have a bridge that can be powered by different power sources, for example batteries or atx power supplies interchangeably.

I've attached a common schematic. Let's say transistors Q4 and Q1 are ON, so that the motor is spinning. If the transistors go OFF, then the back-emf of the motor will cause a current to flow from GND to the supply through D4 and D1. Am I right?

The problem is, I don't want the power supply to sink current. Maybe a battery can handle this current without any danger, but what about a generic SMPS?

A possible solution I've come across is the use of a sort of "shutdown phase". Doing so, the current flowing in the flyback diodes is kept in the h-bridge and doesn't go into the supply.
As before, let's suppose that Q4 and Q1 are conducting. Instead of switching off them together, I switch off only Q1, and let the freewheeling current flow between Q4 and D1. Only after, Q4 is shut down too. Does this make sense?

If yes, could you suggest me how much time the "shutdown phase" could take? I mean, how can I figure out how long does it take to "discharge" the back emf of the motor?

Thanks, any help would be appreciated!


texts: Understanding Dipole vs Commercially available antennas

texts:
I'm working on a project involving RF. I have a pretty good understanding of "HAM Radio" style RF engineering, but not at a professional level.

I'm trying to find a commercially available dipole antenna for a high altitude balloon. I have no available ground plane, and so my first though was to look for dipole antennas on DigiKey. As I understand it, a 1/2 wave dipole (two 1/4 wave wires -> Balun -> SMA) is the optimal isotropic antenna. I am not interested in directional gain. I'm interested in both 2.4Ghz and 433Mhz. I'd like to spec an antenna for each.

My issue is that none of these antenna types are recognizable to me:

I've found lots of PCB antennas. Some look like dipoles, but are connected to coax with no balun. Some are "rubber-ducky" style, which I don't fully understand. How can they work without a ground plane? How do handheld Baofeng radio antennas work? Some others are just wire, with various twists. Is there a reason there aren't any normal Dipoles? Assuming cost is not a barrier, what's the best (most efficient?) isotropic antenna style?

I was envisioning something like a rubber ducky, but with two arms coming off the feed point. I found one like that (RPSMA sadly):

But per the datasheet it's 14.5cm total, and for 433Mhz it should be 35cm!
link here

I can build my own dipole from wire and measure its performance on a VNA. Why are so few products available along those lines? Help me understand my shopping confusion.


texts: Question on brushed DC motor voltage measurement

texts: I'm operating a brushed DC motor via PWM at 5 kHz. It's a big motor rated at 125V/27A. I don't have an voltage acquisition circuit. Just a multimeter. But I want my microcontroller to know what the motor voltage is. If I have a DC link voltage of 130V for the motor, and I know my duty cycle, can I say that at 50% of duty cycle the motor voltage is about 130/2 = 65V without measuring with a meter? I'm also measuring RPM of the motor. Let's say I give a duty cycle of 50%. This will yield a certain RPM value at a certain voltage input. If I measure 1000 RPM at 50%, the average voltage should be 65V? This is what I think, correct me if I'm wrong. Thank you.


texts: What is the time-constant relation between an electromagnet and its coil?

texts:
If a coil has a time constant of about 30 seconds, will any electromagnet made from this coil have the same time constant, or will it be changed by the core / the surroundings ?

In other term, will the magnetic field persist if the power is cut down ? And how is the time for which it persists calculated ?


texts: Correct Switch / Fuse Locations for Multi-SMPS Power Supply

texts:
What is the proper way to fuse and switch a power supply consisting of a bunch of SMPS like the following:

There would be up to 5 separate output voltages. The outputs shown are about 35W each. Other outputs would be less.

So currently I have a mockup that has a single fuse and a single switch on the AC load line.

Is this safe?

Would it be better to use a 2 pole switch to switch in both load an neutral? Why?

Should I fuse each SMPS separately? If yes, why and where?

Points labelled A, B, C and D are potential locations for reference.


texts: Help me hack this other speaker: Where would I introduce two different DC voltages?

texts:
I already asked a question about a similar speaker. I am also trying to convert a larger speaker in the same fashion.

I open the speaker, and can identify the power supply and rectifier (I believe) just as in the last question. I measure the voltage across the medium-sized capacitors (1) and it measures 24V... now I try to hook up the capacitors in the same fashion I did the first time to 24V DC, only this time it does not work.

I believe that in this system there are two different power systems. Because when I measure the voltage across a second set of capacitors (2) it's 5V, I can't really tell if I'm jumping the shark, I'm wondering if I introduced a second DC 5V source, if I can get this speaker also to operate.


texts: MSP430G2553 Reading from ADC10 Temperature with Button ISR

texts:
This is my lab assignment. When I press the button, the red LED toggles on and off. But, I can't seem to read anything from it. Also, there's an empty loop in the code, but I don't know what to insert there, in order to read the temperature. Also, this code was a template before, I filled out all of it except that while loop. What can I write there?

#include "msp430g2553.h"
#define RED BIT0
long Sample;
long i=0;

void main(void) {
    WDTCTL = WDTPW + WDTHOLD; // Stop WatchDog Timer

    // Button
    P1DIR &= ~BIT3; // P1.3 (push button) as input, 0 input
    P1OUT |= BIT3;
    P1REN |= BIT3; // Enable P1.3 (push button) resistor
    P1SEL &= ~BIT3; // Select P1.3 (push button), 0 selects
    P1IE |= BIT3; // Port 1 Interrupt Enable P1.3 (Push Button)
    P1IFG &= ~BIT3; // Clear Interrupt Flag P1.3
    P1IES |= BIT3; // P1.3 Lo/Hi edge

    // Led
    P1DIR |= BIT0; // RED LED as output
    P1OUT &= ~BIT0; // LED off

    BCSCTL1 = CALBC1_1MHZ; // Set range
    DCOCTL = CALDCO_1MHZ; // Set DCO step + modulation
    BCSCTL2 |= SELM_0 + DIVM_3; // MCLK = DCO/8 These bits select the MCLK source

    ADC10CTL1 = INCH_10 + ADC10DIV_7; // Temp Sensor ADC10CLK/8
    ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + REFOUT + ADC10ON; //+ ADC10IE; //+ ADC10IE-->Int EnablE;
    // Ref voltage/Sample&Hold Time
    // Ref Generator ON/ADC10 ON

    _BIS_SR(LPM0_bits + GIE); // LPM0 General CPU Interrupts Enabled
    while(1) i++; { // Execute some useful computation

    }
    }

#pragma vector=PORT1_VECTOR // ISR for Button ADC10 operation
__interrupt void Port_1 (void) {
    ADC10CTL0 |= ENC + ADC10SC; // ADC sampling and conversion start
    Sample = ADC10MEM; // Read ADC sample
    P1OUT ^= BIT0; // Toggle Red LED state
    P1IFG &= ~BIT3; // P1.3 Interrupt Flag cleared
    _BIC_SR(LPM0_EXIT); // Exit LPM0
    }


texts: How to measure current with an analog multimeter?

texts:
I need measuring the current through a dc motor with an analog multimeter, but I don't know how to select the correct function to that.

The meter is a FT-360TR. I know it can measure currents of miliamps and it also has a function to measure currents <= 10A, but I don't know how to select this function.

FT-360TR http://www.aeletricaararas.com.br/loja/media/catalog/product/cache/1/image/5e06319eda06f020e43594a9c230972d/f/i/file_11_3.jpg


texts: Comparison of the two following rectifier configurations

texts: Could anyone tell me the limitations of each of the two following full-wave rectifier configurations? Since the first one does the job, why a more complex design is better? Thank you.


texts: Is there some type of SPDT device that can carry high-current DC loads while closed, but switches when there is no current?

texts:
In particular, I'm looking for a type of relay-like device that:

Is mechanically latching (or similar)
Is effectively SPDT
Can handle 50+ Amps DC when closed
Is extremely safe and reliable
Will fit in the palm of my hand

I'm assuming the best way to achieve this would be to find a relay that can handle high currents while closed, but can't handle switching under high currents. This would be perfect, as I plan to switch these relays only when the system in question has almost no current running through it, so a low current rating should be fine - however, I also want to be 100% sure that the relays can handle much larger currents that will be run through them after they have closed one way or the other, and ensure there will be no arcing across the relay or failures due to hard jolts.

Does such a thing exist? Or are relays the wrong way to go about this? Would I need to look at custom-designing something?

Obviously, I'm not seeking any specific product recommendations, but I've not really found any good way to look for anything that meets these criteria and was hoping somebody might be able to point me at a type or category of relays that I can use to narrow my own search, or maybe some non-relay device that might do what I'm looking for.


texts: How much effect do everyday EMF fields have on cell phone hardware?

texts:
A friend and I are debating the real world usage of this technique:

http://phys.org/news/2014-04-smartphone-sensors-trackable-fingerprints.html

Basically by watching the measurements given by a specific piece of cell phone hardware researchers were able to identify unique phones by the profile of their hardware signals.

The argument is whether EMF from everyday sources would skew these profiles. I just don't think that the EMF from the earth or a powerline would have enough "weight" to even show up in the profile.


texts:
I am new to these types of projects and mostly program so I don't understand completely the functions so it would help if your answer was thoroughly explained.

What my project is we have a python script that sends commands to adafruit which should turn the motor but doesn't. The lights turn on so the motherboard receives the signal, and it seems to get the proper output but it still won't turn

Servo Motor 28BYJ-48
Power Supply: 4 X AA BATTERY HOLDER WITH ON/OFF SWITCH
Adafruit 16-channel 12-bit pwm/servo driver with rasberry pi

"The four batteries are held in series, for a nominal output of 6V DC for alkaline (6.4V when fresh, 4V when dead), and 4.8V DC for rechargeables (5.2V when fully charged, 4.4V when discharged). Using rechargeables will make this work nicely with nearly any 5V project, with alkalines you may want to put a 1N4001 in series to drop the voltage from 6V down to 5.3V."

We use the following code to attempt to turn the servo

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BOARD)

ControlPin = [7, 11, 13, 15]

for pin in ControlPin:
    GPIO.setup(pin, GPIO.OUT)
    GPIO.output(pin, 0)

seq [[1,0,0,0],
    [1,1,0,0],
    [0,1,0,0],
    [0,1, 1,0],
    [0,0,1,0],
    [0,0,1,1],
    [0,0,0,1],
    [1,0,0,1]
]

for i in range (512):
    ### GO THROUGH THE SEQUENCE ONCE ####
    for halfstep in range(8):
        for pin in range(4):
            ###SET EACH PIN###
            GPIO.output(ControlPin[pin], seq[halfstep] [pin])
        time.sleep(.001)

GPIO.cleanup()

All the hardware seems to be correct. Everything is connected and the signal is sent, the lights turn on. The servo motor just doesn't turn


texts: Replace vintage speaker connection by modern one

texts:
So, I have a vintage Pioneer hi-fi installation and I want to use it in a recording studio. It features two passive speakers and one amplifier. My problem is that the speakers need to be connected to the amp by tightening speaker wire to them using screws - and I want to be able to easily attach and detach them.
The amp has speaker plugs (similar to the modern binding posts) which look like
this http://www.ultraelectronicactive.com/Media/Equip/Connectors+Cables/Pioneer-Speaker-Plugs.jpg
and the connection on the speaker side is kind of like a binding post, like

(source: stereobarn.com)
but it's just simple screws holding the wire.
Now, my questions is: does anyone know if there already exists some cable connector which fits these connections? Or does anyone have a suggestion on how to make one myself? I have a basic knowledge of soldering. I would love to just have a 1/4" or banana plug speaker cable which I could easily plug in or remove when I want to. I am aware of the possibility to plug in banana jacks into binding posts, but they would in no way fit mine.
Edit: I also can't seem to open my passive speakers to change out the connections.


texts: How to connect live and neutral and earth connection in AC devices plugged into socket?

texts:
I know that when I have a fixed lamp in my house I have to use a single switch on the live wire. But when the device is connected using a plug the live wire and the neutral wire vary depending on how I connect the plug. I found a lamp with the following schematics in my lab with also a ground connected only to the metal case of this quartz-tungsten lamp (so, to be clear, the ground is not connected to the live or the neutral but only to the case of the lamp). This lamp is connected using a plug to the socket Type F: also known as "Schuko" which does not have any distinction between live and neutral.

simulate this circuit – Schematic created using CircuitLab
Is this connection valid? What is the best connection for a lamp which is controlled by a switch and eventually plugged into a socket? Why when I have to install a lamp in my house I have to take care to interrupt the live wire while in many movable lamps the switch could be in the live or in the neutral depending on how I connect the plug?


texts: Best electronics book for a physics graduate

texts: I'm a physics graduate; I want to learn some electronics so I'm searching for a book which gives an fair overview of electronics (components, analog circuits, digital circuits...) suitable for me (not like electronics demystified or electronics for dummies).


texts: What is the purpose of this layout feature

texts:
I have been researching some TI power supply ICs and came across the following diagram in the datasheet for TPS40200.

Can anyone explain why the trace circled in red is connected as it is instead of filling in the entire plane and joining to its edge? Will it act as an RF filter?


texts:
I'm currently working on an RS485 DMX circuit and am thinking about proper protective measures.
I've oriented myself on this question. I understand that galvanic isolation does not equal ESD protection, so I need some TVS diodes on the incoming signal lines which clamp to chassis ground, not isolated ground (because the isolation devices only work up to 600V/1000V.)
This raises some further questions:

Do I need to filter the input of the DCDC as well (because of switching noise?) If yes, how much? I don't think I need a full CM-filter though, as the signal is relatively slow at 250kbps.
Although the circuits are isolated, they are not allowed to drift apart too much if I use TVS diodes, otherwise they'd trigger randomly. As I use ESD-protected drivers, I don't have to choose tightly specified diodes. I only need to protect the isolation devices, not the driver. But I still need to keep chassis ground and iso ground close enough that the TVS doesn't trigger. Should I just put 10Mohm between the grounds to couple them, or am I overthinking this? (see Edit)
The former point adresses data line ESD events. What about ESD on the ground plane? Usually you don't protect GND from ESD events, but if I don't then the ground has +8kV in respect to the signal lines, which can't be good either - and I'll violate the 600V isolation to the main circuit. So can I just put a TVS on isolated ground to chassis ground? How does this mesh with the ground coupling?

Maybe it's an XY question. What I want to do: Protect my IO from ESD and misconfigured devices down the line. Is this appropriate or am I overthinking stuff?
Edit:
I've read ANSI E1.11 (the DMX Standard), which says that galvanic Isolation for transmitters is not necessary, but can be done (4.2 & Annex A1). I'll go with isolation, because the ports can also act as an receiver which should be isolated. Also, I'll need to connect iso gnd to chassis gnd with >22MOhms.
So question 2 has answered itself. Question 1 & 3 still remain; does the R between iso gnd and chassis gnd pose problems to ESD events? I haven't found a reference implementation for ESD protection.


texts: Protection and charging circuit for LIR2032 or ML2032 battery

texts:
I am designing a tiny device with very low power consumption. The device needs a rechargeable battery which should be charged from USB.
I have found LIR2032 and ML2032 batteries that can provide enough current to power the device. As I understand these two use different chemistry, so need different charging algorithm. Can one circuit support both LIR2032 and ML2032 without external switch? What protection and charging do each of the batteries require?


texts: How do I pick an ADC to monitor the output of a switching regulator?

texts:
I am currenly designing an automatic tester to test the switching regulators on my boards. I will be doing load step tests, and I want to be able to catch defective regulators, i.e., ones that are not able to maintain or fall out of regulation.

If I use an ADC, should the sample rate be 2 times the switching frequency of the regulator or should it be higher? How should I deal with switching noise; a digital filter maybe?

Thanks


texts:
I have a 4Mhz crystal and i connect it in series between the function generator and the oscilloscope probe as shown below:

simulate this circuit – Schematic created using CircuitLab

However i don't know if this testing method for XTAL is true or not but to see if the crystal works or not i set the function generator on 5Vpp and start to increasing the frequency, i was expected to see some change in the output in 4Mhz, but just when the frequency reach 4MHz i find the voltage in the output become 50Vpp !

I know the resonance causes increasing the voltage but there are no Inductor in this case,

So i'm wondering why this happen without inductor?


texts: I am building an oscillator circuit at 4-6 GHz and I am trying to make a band switching circuit to add capacitors up to 10pF. Every band switching diode and low capacitance transistor I have tried have not helped me so far! Which is a good component to use as a switch in my circuit and how should it be connected with the capacitor to control it? Thanks in advance!


texts: Will this battery case be able to sustain 3.5 amps?

texts:
I'm trying to make a 10S Li-Ion battery case, and I'm currently wondering if it will be able to sustain a current of 3.5 amps running through it.

I like to believe I'm pretty good at electricity, however, I have no idea how much current can go through this thin plating (see picture).

I'm looking to add nickel strips between the battery connectors, in order to connect the 10 cells in series. The nickel strips are 5mm wide and 0.2mm thick.

I wanted to solder the plates to the connectors using 63/37 tin/lead solder.

The 3.5 amps calculation comes from the fact that there will be 2 of these (10S2P) powering a 250 W device (at 36 V, so 250 W / 36 V = 7 A, 7 A /  2 = 3.5 A)

Is this doable? If not, what can I do to make it work? I may be able to stack several of the nickel plates together, if that may help. I can also put the plates inside the U shape of the spring contacts.

Thanks.


texts: What is the gain in a non-inverting amplifier

texts:
I am unsure if I am tackling this problem correctly. The input signal is connected to terminal E4 and the output signal is observed at terminal E9

What is the voltage gain when E1 is connected?

What is the voltage gain when E2 is connected?

Neither E1 or E2 is connected. What is the expected voltage gain?

My solution:

Use the formula: $$A_v = 1 + R_2/R_1$$ which then becomes: $$A_v=1+R_{FB}/R_1$$

Use the same formula, now just substitute R1 with R2.

$$A_v = 1+ R_{FB}/R_2$$

My guess is that there is no there would be no voltage gain, since there are no resistance on the top half of the circuit?

Am I totally wrong here?


texts: Powering Negative Vcc on Op Amp with no negative supply voltage

texts:
I am making a shunt current sense resistor circuit. I will place this circuit on my main PCB board to measure the current going through all the different channels. I have a supply voltage of 12V Vcc to go into the OP37 op amp, which is used in my circuit. However, I don't have a -12V supply voltage to power the -Vcc terminal of the OP37 op amp. I know there are some IC's made by to invert a voltage, but the IC is kinda big, and I was looking for a simpler solution. I am using KiCAD to model my circuit in a schematic and LTSpice to make sure my circuit works correctly.

TLDR: How can I make my 12V supply voltage invert to power the -Vcc power supply of an op amp for use in a PCB?


texts: Transmission lines with same impedance but different dimensions

texts:
Suppose we connect two transmission lines with characteristic impedances \$Z_1\$ and \$Z_2\$. The reflection coefficient looking into the transmission line with impedance \$Z_2\$ is
$$
\Gamma=\frac{Z_2-Z_1}{Z_1+Z_2}.
$$
Now consider the case where both lines are two coaxial conductors. For both lines, the impedance may be calculated by
$$
Z=\frac{1}{2\pi}\sqrt{\frac{\mu}{\epsilon}}\ln{\frac{D}{d}},
$$
where \$\mu\$ and \$\epsilon\$ are, respectively, the magnetic permeability and dielectric constant of the dielectric between the two conductors, \$D\$ is the inner diameter of the outer conductor, and \$d\$ is the outer diameter of the inner conductor. Assume the dielectric is the same between the two transmission lines, but for one of the transmission lines, \$D\$ and \$d\$ are both smaller than the corresponding values for the other by the same factor. In this case, \$\frac{D_1}{d_1}=\frac{D_2}{d_2}\$, \$Z_1=Z_2\$, and the reflection coefficient \$\Gamma=0\$.
Based on this result alone, I would expect a voltage wave incident on the interface between the two lines to undergo no reflection. On the other hand, there is clearly a geometrical discontinuity at the interface, which I would intuitively expect to produce a reflection. Is my intuition wrong or am I missing something?


texts: What can cause this pin to return to 1 V after connecting it to the Jetson Nano?

texts:
I am working on a project where I make a HAT for the Jetson Nano dev kit. (essentially a pi4 with GPU) I am powering the JN with my HAT, which provides 5V to pin 2&4 of the JN. I have a few buttons connected to the JN which are pulled up with a 10k resistor. (see picture) I have verified the workings of the switches without the JN attached, they are 3v3 when inactive, when switch is pressed they become 0v. I have also verified the working of the GPIO pins by connecting GND and 5V to it, and it read it correctly. I also tested if the pin is floating if not connected, and that seems to be the case as well.

This is where the strange behavior starts: when I connect the HAT to the JN, and set pin 7/BCM4/GPIO126/SW_Off to INPUT, the inactive-voltage drops from 3v3 to 0.98V. This way the GPIO is useless, could anyone explain how this could happen? What other steps can I take to tackle this and find out how to resolve this? If it is useful at all, I included the board layout. I verified that R4 measured 3v3 on 'topside' (relative to both HAT and JN, their grounds differ 6mV), however I measured 0.98V on the other side. Any help greatly appreciated!
Edit: it might be good to mention that the top connector in the layout is the 40 pin connector, the middle stop is the resistor, and the bottom smd pad is the switch connector.
Edit: The resistance measured to ground (with power off) is 11.78K, and the resistance measured to +3.3V is 10K. This calculates to a voltage of 1.78 Volt, but measures as 1 V when the system is on. Any suggestions as where the resistance to ground could be coming from?


texts: Why do we use (0,+V) in digital electronics (eg processors) instead of (-V/2,+V/2)?

texts: Would making the default voltages for 0 and 1 where relevant +|- V/2 save 1/2 power?


texts: I cannot get opto-coupler H11L1 to work as MIDI Input

texts:
I received my H11L1 opto isolators (yeah) to use for my MIDI input(s).

However, I cannot receive anything (and tried various circuits).

According to the H11L1 (see datasheet) an example circuit is:

The red box is the part I expect I made a mistake.

According to the MIDI spec an input should look like

The red part is again the similar part I expect problems with.

The following is a screenshot of my circuit (note I replaced the ferrite beads by cables since I do not have them yet).
 The two cables on the right go to pin 4 and 5 of the MIDI cable (I also switched them so that is not the problem).

I use 270 ohm and 220 ohm resistors as advised.

Does anybody have an idea what can be wrong?

Update: It's improved if I put an Hex inverter (74HC14) after Vo (open collector output). The test LED (not in circuit is now shining more whenever MIDI input is received, the Arduino still doesn't get correct data, probably the signal is too much disturbed somehow).

My sketch:

#include <MIDI.h>

#define LED 13

MIDI_CREATE_DEFAULT_INSTANCE();

void setup()
{
  pinMode (LED, OUTPUT);
  MIDI.begin(MIDI_CHANNEL_OMNI);
  MIDI.setHandleNoteOn(MyHandleNoteOn);
  MIDI.setHandleNoteOff(MyHandleNoteOff);
}

void loop()
{
  MIDI.read();
  delay(1000);
}

void MyHandleNoteOn(byte channel, byte pitch, byte velocity)
{
  digitalWrite(LED, HIGH);
  delay(1000);
}

void MyHandleNoteOff(byte channel, byte pitch, byte velocity)
{
  digitalWrite(LED, LOW);
  delay(1000);
}

Update:

It seems the opto coupler is probably working correctly, but the Arduino does not pick up the signal correctly. I made a new question on that stack exchange:

Arduino question about H11L1


texts: Convert 5V PWM Arduino Signal into 12V signal that can deliver 100mA

texts:
I am an electronics newbie and I want to convert the 5V PWM signal from an Arduino into a 12V PWM signal which delivers 100mA (rms). How would such a circuit look like? I tried with OpAmps and got the 12V running, but the OpAmps I had could only deliver a few mA. Which OpAmp would be the correct one for me? I have supply voltages of 5V-30V.

Since for my application it doesn't matter if the output is a true analog or a PWM signal I also don't mind changing the signal to a true analog one.


texts: LED-Monitor-Firmware reverse engineering / disassembly => replace manufacturer startup logo

texts:
I have a display from a disassembled led-monitor (Wortmann Terra 2446W), that I want to use for a SmartMirror-project.
Unfortunately, the monitor shows a big manufacturer logo when connected to power, therefore I am checking now, wether I maybe could be able to replace that logo or not.

The monitor firmware is possibly located on the only non-volatile memory chip I could find on the controller-board, a MX25L4006E (4MBit SI NOR-Flash). Since this chip is programmable via flashrom-utility (and listed as fully supported) and I have a flashrom-compatible programmer based on a FTDI2232H, I think I should be able to read the firmware from the flash / write a modified version back.

Has anybody ever replaced such an embedded logo, and maybe has got some hints on how to possibly identify/reverse-engineer the address-ranges and format of the integrated boot-logo ? Will eventually binwalk be able to directly identify it, e.g. in the same way that for example testdisk & photorec identify filetypes based on raw data bytes (fileheaders, block-formats e.g.)
I will update this question as soon as I successfully obtained the binary firmware file...
Thanks in advance for any help, Oliver


texts: Is power dissipation for SMD resistor rated only for air dissipation or air + PCB?

texts:
I know that PCB with good copper area will dissipate much more heat than air surrounding the resistor. However, the datasheet for Yageo resistors is vague about whether the dissipation ratings take into account PCB or just air. I am planning to drive this one close to maximum and it got me wondering. Can I give it 3W instead of rated 1W if it is attached to copper layers on both sides with big vias? As far as the current goes, it will be 1/5 of the rated current at 3W.
PS I know the resistance will drift upwards but it is not an issue in this case (as long as not downwards). I just worry about it not blowing up.


texts: Question: AC Voltage and Current variables

texts:
So I know how alternating current is produced, but I'm curious to what determines the voltage and amount of current moving within the wire.

Does the frequency of the alternations give more voltage/current or does the strength of the magnetic field produce that? Or is it both?

Let's consider this energy as raw, before it's been transformed.


texts: High precision soldering of through hole components

texts:
I have a through hole component with many leads spaced closely together, see picture:

I'm looking to unsolder it from the PCB and then solder it back again. Unfortunately, the leads are spaced so closely and the beads of solder are so tiny, that I'm afraid I wouldn't be able to replicate this detailed work with my soldering iron.

What technique was used by the manufacturer of this board to achieve such high precision in soldering this component? What advice do you have for replicating this work at home while achieve the same quality result? I'm open to buying additional equipment if necessary.


texts: How to trigger a "Relay Module With OPTO Isolation Support High or Low Level Trigger" with a momentary switch

texts:
I am a complete novice with anything beyond simple wiring of guitar effects and kits. I have a unit, a Roland GR-55, that has a momentary switch built-in. I want to trigger this switch with a separate unit (Boss MS-3) that contains its own momentary switches, and which allows me to "assign" those switches via a 1/4" TS type jack.  These switches work like regular passive momentary switches.  If I want to control the GR-55 switch externally via this second unit, I need to isolate the circuits so as not to fry the CPU in the GR-55 in case of some ground fault or other issue I might not know about.

I am looking at this relay module: HiLetgo 12V 1 Channel Relay Module With OPTO Isolation Support High or Low Level Trigger, $4.99

I think I understand SOME of how I might be able to use this in this particular situation: use the internal 9V DC power of the GR-55 to feed the DC +/- on the relay. Connect the two leads of the momentary switch in the GR-55 to the relay "open" and "common" contacts. This keeps the logic of the GR-55 isolated from the external switching system and the 9v supply.

What I do NOT understand is this: there is one contact on the transmit side that accepts a high or low level signal, but a simple momentary switch is simply a passive loop connector. Is there any way to use this kind of pre-fab circuit with a passive switch, or does it REQUIRE a second powered circuit/signal to trigger the relay?

If this board will not work, is there any other simple solution to this problem that would not require my having expertise in the area?


texts: UL Clamping Voltage Ratings on Surge Protectors

texts: I have been looking for some new surge protectors for my devices, and I am having trouble understanding the meaning of the voltage clamping ratings on many surge protectors. It seems that all of the UL ratings are much higher than one would expect, as the lowest one is 330v, whereas mains voltage in North America is 120v. Would this mean that even if there was a surge that went to 300v, the surge protector would do nothing to protect the connected devices?


texts: How are voltage dividers used in circuits?

texts:
I am a newbie and wanted to understand in simple terms how a voltage divider maybe used to for instance, power 2 different LEDs of different voltages if they were within a circuit.

The main issue that concerns me is where the drop occurs. Before the resistor or after the resistor. I know from diagrams tutorial videos that the multimeter is usually connected with one terminal before and one after the resistor but that doesn't help with the placement of components according to my inferior understanding of this matter.

Please kindly provide guidance so I may clarify my problems further.

Thank you in advance.


texts: Can somebody explain why normal diode(1N4001 or 1N4007) is used in rectifier bridge insteed of schottky diode

texts: I have 9v AC(1A, 50Hz) as input to 5v DC(500mA) as output rectifier circuit to power up the development board. But I had a doubt if I use Schottky diode instead of normal diode what happens to the circuit. By watching many videos I understand that Schottky diode can operate at high frequency, lower temperature dissipation. But it has more leakage current compared to the normal diode Is that it will affect the rectifier circuit?


texts: I dont really get min/max terms. I think for filling into K-Maps, m1 (minterm 1), I will put 1 into the box for 1. For maxterm M1, I will fill 0 into box for 1? But if the question is "What is the sum of maxterms \$M4+M7\$?". What do I do?