texts: Board review: is this PIC16F877 RS232+ICSP board correct/robust?

texts:
I want to make my own development board based on a PIC, to make a RS232 bootloader from scratch. It's been a while I haven't used a PIC, and it was on a ready made development board.

I've looked around on the web and designed what I think is a minimalistic RS232 and ICSP board based on a 16F877. Could you review it and tell me if it'll work, if it can be made more robust (for future projects as well)?

Sorry if the symbols look funny, I use DesignSpark PCB and I usually go first with the models in the ModelSource database.

In particular, the ICSP is going to be a ICD3 which is apparently high voltage... Not good for the MAX233 and the LM340.

P.S: Those are SMD components, therefore my "breadboard" will actually be a draft PCB from a PCB house


texts: Is there a material that conducts heat well and has a very high melting point, but is also an insulator?

texts:
A lot of insulating materials are also non-metallic, which typically don't have a high specific heat. However, I am interested in experimenting with insulators that conduct heat as well as metal, but impede currents just as effectively as typical insulators. Does such a material exist?

Glass for instance can act as an insulating material, but it has a pretty high specific heat. On the other hand, rubber often has a lower specific heat, but it will melt rather easily. Copper has a low specific heat and a high melting point, but, it conducts electricity very well. You can see there is some challenge in figuring this out without explicit experience with such a material.

The temperature range is high, which when you talk about electrical components that can tolerate high heat means it's at least high enough enough to burn your skin. Since I am concerned with melting points in materials like rubber, glass and different metals, the range is least a few hundred degrees (either ºC or ºF) to 2000 degrees, depending on the actual impedance of the material. However, it should be publicly viable for experimentation, the highest possible grade material like diamond is not necessary.


texts: What is the purpose of those capacitors on this DC DC switching mode step down circuit?

texts:
I am designing a PCB board with a 12V to 3.3V DCDC switch mode regulator. I am checking some circuits and datasheets, and I found some capacitors that I would like to understand.

I will use the Analog Devices ADP2301. It is my first SMPS, and I would like to go with something easy.

But I found these capacitors in some other circuits:

I think that they will protect the ON/OFF circuit, and the other will filter the incoming feedback.

What do you think? How I would calculate the capacitance and rated voltage?


texts: Arduino interface with I2C Pressure Sensor

texts:
I have a Honeywell ASDXRRX100PD2A5 I2C Pressure Sensor that I want to read using an Arduino.

Looking at the datasheet, I know that the I2C address is 0x28, and I have had a play with bits of code I've found on the internet, but none of them make any sense. Numbers do increase as I increase the pressure, but not on the scale shown on the datasheet.

Here is a link to said datasheet: http://www.farnell.com/datasheets/1676926.pdf

Here is a datasheet that has information about communicating with Honeywell sensors using I2C: http://sensing.honeywell.com/index.php/ci_id/45841/la_id/1/document/1/re_id/0

Without having much experience with I2C in the past it's hard for my to get my head around it.

Also, here is a picture of my setup:

The code I am using to test it out at the moment is as follows:

#include<Wire.h>
#define sensor 0x28 //Unique bus address

void setup()
{
  Wire.begin();//Wakes up I2C bus
  Serial.begin(9600);
}

void getdata(byte *a, byte *b)
{
  //Move register pointer back to first register
  //Wire.beginTransmission(sensor);
  //Wire.write(1);
  //Wire.endTransmission();
  Wire.requestFrom(sensor,2);//Sends content of first two registers
  *a = Wire.read(); //first byte recieved stored here
  *b = Wire.read(); //second byte recieved stored here
}

void showdata()
{
  byte aa,bb;
  float pressure =0;
  getdata(&aa,&bb);
  Serial.print("byte 1: ");Serial.println(aa,DEC);
  Serial.print("byte 2 ");Serial.println(bb,DEC);
 delay(1000);

}

void loop()
{
  showdata();
}

I am getting the following results at the following pressures:

0psi    byte1: 31
        byte2: 246

10psi   byte1: 34
        byte2: 102

20psi   byte1: 32
        byte2: 30

30psi   byte1: 39
        byte2: 167

Any help pointing me in the right direction would be much appreciated.


texts:
I am trying to build a heater based on Nickel-chromium 80%/20% wire (nichrome) to heat tubes of solutions for an electrophysiology research setup. The plan was to wrap a length of nichrome around each tube, then chain the tubes in series by joining each end of the nichrome to a short piece of hookup wire with a gold connector on the end.

BUT I just tried to solder a length of hookup wire to the nichrome and found that the nichrome won't accept my standard rosin-core lead solder at all. I'm using a Weller iron at around 750°F (400°C), but playing with the temp made no difference except for increasing my frustration. My suspicion is that I need to use some other kind of solder, or if the soldering technique is too cumbersome, some other way of joining the nichrome to the circuit. What are my options for getting this nichrome stuff to play nice?

UPDATE: Thanks for all the responses. I ended up using a type of gold connector we had around where I could trap the nichrome wire by filling the hole for the wire with solder. Hopefully this will hold up.


texts: Calculate values of resistors in a given BJT amplifier circuit

texts:
I have the circuit shown below and i have limited resistors to make it work. The LED's rated current is 10mA so Ic = 10mA. I know that beta for the transistor is 100.

The resistors are (I have 2 of each):

47ohm
100ohm
470ohm
10k
15k
20k potentiometer


texts: How to design RF PCB to ensure the 50 ohm impedance

texts:
I do not have any experience designing RF circuits and I am finding many challenges for my project.

One of them is to match the 50 ohm impedance that some components demand. In the input of my PCB I will have a mixer (RF=10 to 15 GHz, LO=15 GHz and IF=DC to 5GHz), which needs these 50 ohm in the RF, LO and IF pins.

The inputs, RF and LO, will go connected to SMA connectors (is that enough for the required impedance or I have to design the PCB trace to match the 50 ohm?).

The output, IF, needs the load of 50 ohm, which I guess I can get with the PCB trace. The thing is that right after it I'll have a LC low-pass filter at 1 GHz cut-off frequency. Will this 50 ohm transform the filter into a RLC?

All these questions may sound a bit stupid for RF engineers, but for me is very confusing. Everything is so easy in the DC domain..

Thanks


texts: Can power of an electromagnet be changed like frequency of a motor is changed using VFD?

texts: I am from a commerce background and am not technical. I want to use an electromagnet to lift up Iron and Steel but since I have a retail shop, I have to lift up varying quantity as per the demands of my customers from the whole lot I have. There are electromagnets working in iron and steel all over the globe but they all have fixed power. I want to know if it is possible to change the power of electromagnet using a regulator sort of a thing so that it may lift up only 100kg out of a lot of 10000 kg and also 2000kg out of the same lot as and when demanded. I am not looking to do it myself but want to know the possibility and if there is any specific device that helps do it like there is VFD for motors.


texts: Can I connect a 15A surge protector to a 13A extension cord?

texts:
As someone who’s studied engineering, I should be able to answer this question. However, a quick search online has me confused.

Provided what I’m plugging in (a laptop drawing relatively little power) doesn’t exceed the extension cord rating, there should be no issue.

Advice online suggests otherwise. Is there something about consumer electronics I don’t know? Or, perhaps online advice is merely simplified (and presented inaccurately) to be foolproof.

I see a similar question here, but again I suspect those answers are inaccurate so as to be foolproof.


texts: How to measure frequency of AC Voltage(In range of 0.05-5v) using micro-controller?

texts:
I have one sensor which outputs in the range of 0-5v AC voltage and I want to measure a frequency of this signal using the microcontroller ?

Is there any IC which gives digital pulse in output when input of 0.05-5v AC voltage is given? and using that pulse i can measure the frequency using micro-controller?

Frequency range will be within 0.5 Hz to 1500 Hz and Voltage range:- 0.05 - 5v
Thanks in advance.


texts: Optimizations for LM2596, Positive and Negative Voltage

texts:
I'm working with the LM2596 to get a positive and negative voltage using two separate IC for each. I'm having trouble optimizing them for a 1 A load. I followed along with TI's WEBBENCH designer to optimize them resulting in the circuit below, but I was wondering if some adjustments can be made for a smoother output voltage with lower ripple? The parameters include a 10-20V input range, with an output of 5 V, 2.5 A. I found the adjustable model in LTspice, and I'm using that to simulate the results, but it seems I'm getting around 2% ripple voltage at the output even though my design is supposed to get 0.02%.

Regarding the negative output circuit, TI's webbench didn't allow for a negative output using the LM2596. I followed the negative output example as best as I could to get the output voltage that I wanted, but are there any suggested optimizations I should take for the design, or is it fine as it is?

EDIT: Sorry, wanted to note. The input voltage is taken from a rectifier, so it's a positive, rectified, unregulated DC voltage.

EDIT: Wanted to add more information. Regarding the negative voltage circuit, when I ran it with a 1 amp load as shown below, the input voltage oscillates between 6 to 8.4 V. According to the datasheet, the input should take from 4 to 20 V, but is this okay given how my negative output is -9.5 volts? Does this limit the current output by the circuit?

simulate this circuit – Schematic created using CircuitLab


texts: How do I detect 1-Wire peripherals without constant polling?

texts:
I'm looking to bit bang 1-Wire from an Atmega uC. My design calls for the Atmega (acting as Host) to detect the presence of a single 1-wire eeprom when it's physically connected to the uC.

I don't want to continually poll the line, as that seems a waste of battery. I've not used 1-wire before, so I might be missing something obvious; for instance, can a peripheral assert a logic low on power up that I could use as an interrupt to wake the uC?

(I'm working on the assumption that the eeprom will be powered by the uC over the data line).

EDIT: I'm thinking something like this: http://datasheets.maximintegrated.com/en/ds/DS28E05.pdf

From what I understand, it will respond after the bus master initiates a reset pulse. But, this gets back to the polling method, which I don't want to use.

Does applying power to the EEPROM "look" like a reset pulse to it? (I doubt it).


texts:
I need to suspend an object attached to a magnet over a coil (don't worry about stability problems), and measure the current required to levitate it to a certain height.
There are a number of possible configurations:

Air core coil with a cylindrical magnet over the coil
Air core coil with a cylindrical magnet which passes into the coil
Ferromagnetic core coil with a cylindrical magnet over the coil

The downside of the last one is remanence in the core material, which may distort measurements.
So, do high permeability low (or zero) remanence materials exist?
How do the efficiencies of the first two approaches compare, in terms of current? How much better, if at all, would the third approach be given a typical core material. Frequencies expected to be below 100Hz.


texts: 4-20 mA analogue signal conversion to flow rate

texts:
I have the following control setup:

For that, I have data recorded for every I/O block, and I am asked to determine the function used by the AIN block to convert from an analogue 4-20 mA signal to a flow value in the range of 0/32 L/m. The plotted data looks like this:

How would you obtain that function?
Thanks for your time


texts:
All powerbanks that have car-jump function have some thingy between the clamps and powerbank socket:

What's inside that thingy?

The manufacturers typically claim 300A of starting current for powerbanks as small as 8Ah, which cannot be drawn directly from Lithium batteries they have inside.

There's a related question I found here Jump start car from lithium ion laptop battery, but I don't believe it's just the protection circuitry, it has to have some kind of "boost storage".


texts: Transformer for 2 lights and time lag switch

texts:
I've looked and can't see an answer to this but my lack of knowledge on the subject may not have helped.

I'm have 2 lights from B&Q which are normally battery powered but can be powered by a transformer with a regulated output of 6 Volts 0.5A DC. I would like to set up the lights to be powered off the same transformer but don't know how to calculate the voltage and current the transformer would be required to output (in either series or parallel).

I'd also like to add a time delay switch to the circuit - would this one work:
http://www.ebay.co.uk/itm/Danlers-Plated-3-Wire-Time-Lag-Switch-6A-Resistive-or-Fluorescent-TLSW-A20-/271266710463?pt=UK_DIY_Material_Electrical_Fittings_MJ&hash=item3f28c183bf


texts:
I am designing a wireless sensor node that will be operating off of 1.8V. I am using an Atmel ATtiny861a MCU with a CC2520EMK radio and a 23A1024 External memory chip. I have a chip select pin for each component, however I still need a resistor value for both pull-ups. Where in the datasheet(s) should I look to find out what Resistor value I should use? I want to conserve as much energy as possible.

If a higher resistor value consumes less power, what exactly is the downside to having a high pull-up resistor?


texts:
I'm building an alarm system (paradox EVO192 with ZX8 extension modules) and was hoping to have separate sections of the system each powered by it's own battery backed up power supply (something like this http://www.communica.co.za/catalog/Details/P0726831591).

The panel communicates and powers extension modules over a 4-wire bus - red/black/green/yellow. Unfortunately, if I just connect the panel to the module using yellow and green and then power the module independently using a different power supply, the panel doesn't see the module. The panel's red and black must also be tied to the module in order for them to communicate properly.

My question is, can I just add the extra power supplies in parallel?


texts: Multiplexing 2-Seven Segment Displays using ARM 7

texts:
I am currently trying to control two seven segment displays from the same 7 pins (P0.0 - P0.6) of an ARM 7 micro-controller. I am first testing this on Proteus simulation software.

I am following the schematic from this 8051 multiplexing tutorial, however my 7 segment displays are connected from Port 0.0 to Port 0.6 and the two controlling transistors are connected at P0.7 and P0.8.

I am pretty sure that the seven-segment display and transistors from my simulation are connected correctly, and that the problem is arising from the following code. I have also tested my code to make sure I am displaying the correct numbers and that the transistor pins are configured as required.

The problem I am encountering is that both digits are being printed on both displays, instead of the first display showing 1 and the second display showing 2.

 #include <LPC21xx.h>
 #define a 0x00000001
 #define b 0x00000002
 #define c 0x00000004
 #define d 0x00000008
 #define e  0x00000010
 #define f 0x00000020
 #define g 0x00000040
 #define T2 0x00000080
 #define T1 0x00000100

 void small_delay (void);

 int main (void)
{

PINSEL0 = 0;                        //Set P0.0 - P0.15 as GPIOS
PINSEL1 = 0;                        //Set P0.16 - P0.31 as GPIOS
IO0DIR  = 0xFFFFFFFF;               //Set all port0 pins as outputs

    while (1){

    IO0SET = e;      //displaying number 1
    IO0SET = f;      //displaying number 1
    IO0SET = T1;     //switching on first display
    small_delay();   //calling short delay
    IO0CLR = T1;     //clearing first display

  IO0SET = a;       //displaying number 2
  IO0SET = b;       //displaying number 2
  IO0SET = g;       //displaying number 2
  IO0SET = e;       //displaying number 2
  IO0SET = d;       //displaying number 2
  IO0SET = T2;      //switching on first display
  small_delay();    //calling small delay
  IO0CLR = T2;      //clearing second display
    }

}

void small_delay (void)
{
unsigned int i, j;

for (i=0; i<10; i++)
 {
    //do nothing
 }
}

This is what I am trying to achieve with the above code:

Send data 1 to both displays.
Enabling left seven segment by using IO0SET = T1;
Calling a short delay.
Disabling left seven segment by using IO0CLR = T1;
Sending data 2 to both displays.
Enabling right seven segment by using IO0SET = T2;
Calling a short delay.
Disabling right seven segment by using IO0CLR = T2;
Repeat.

Are there any flaws in this logic ? Any suggestions/ideas regarding what I am doing wrong in my coding would be greatly appreciated.


texts: Most cost effective way to test USB 3.0 eye diagrams

texts: I saw this question addressing testing USB 2, but I was wondering what the most cost effective way to test USB 3.0 superspeed was. Obviously the frequencies are far higher (multiple GHz), so the test equipment gets more expensive. The Infiniium 90000A is one that people use, but it's >$40k. Are there any cheaper options or methods?


texts: Which capacitor value for current limiting of a transformer?

texts:
I rewired a microwave oven transformer to have an output of 40V and a center tab. With no load the primary gets hot really fast. I measured the current draw with no load and it pulls about 10 amps. So if my math is correct that is 1.2 kilowatts and that is way too much.

I need an output of 40 volts 10 amps that is 400 watts. If I am correct you can limit the current to the primary winding using an oil filled capacitor. So with some leyway, if I current limit the transformer to only pull 450 watts it should run much cooler.

What value capacitor to use? Is there a formula?


texts:
Disclaimer: I'm a noob.

I have the following schematic (updated as per @Transistor):

I had first tried this out on my breadboard. It worked fine. From what I read online, this was two capacitors set up in parallel.

When I do the setup on a PCB prototype board, it short circuits (I'm assuming it is a short circuit because the lights of my Arduino Uno go off.)

Is this enough information for someone to be able to tell me what I'm doing wrong? I can post a picture of what the setup actually looks like if needed.


texts: Armature and field mmf axes in synchronous machines

texts: In the book "Electrical Machines and Technology" by J.Hindmarsh, in the chapter about synchronous machines, it stated that for the machine to develop a uniform torque, the armature and field mmf axes should be stationary with respect to each other, my question here is why? Why should they be stationary with respect to each other and what would happen if one was faster than the other?


texts: How to Clip The Negative Portion of a Signal?

texts: What is an easy way to remove the negative portion of a signal without distorting the positive side of it?


texts: Arduino frequency measurement to 2 or 3 decimal places

texts:
I am in the process of building a Proton Precession Magnetometer to calculate the earths magnetic field strength by measuring the precession frequency of protons in distilled water. I am using an Arduino Nano as my micro controller to control the energizing or the magnetometer, which is basically a resonant coil wound around a tube of distilled water, and then reading the returned precession frequency.

My set up is the Nano switches a DPDT relay to energise the coil from a 12v source then switch over to a receiving set of opamps / schmitt trigger IC into Pin 5 of the Nano to read the frequency which has a  around 2.35 kHz with a bandwidth of +/- 500hz.

The problem I have is at the moment I can only get a frequency reading to 0.1hz resolution after counting the frequency for 5 seconds (ie 2351.5Hz).

But the result is quite stable compared to some other frequency codes I have tried.

I really want to get a stable result at least to 2 decimal places or better 3 decimal places over a shorter counting period ie (2351.523Hz).

Can someone help me please.

Also I'm pretty new to arduino and coding.

My code at the moment is as follows:

#include <FreqCounter.h>
#include <LiquidCrystal.h>

LiquidCrystal lcd(2, 3, 4, 8, 6, 7);

int mosfetPin =  9; // sets mosfet pin to pin 9 on arduino
int relayPin = 10; // sets relay pin to pin 10 on arduino

void setup() {

lcd.begin(16, 2);
pinMode(mosfetPin, OUTPUT); // sets mosfet pin, pin 9 on arduino as output
pinMode(relayPin, OUTPUT); // sets relay pin, pin 10 on Arduino as output
digitalWrite(mosfetPin, LOW); // sets 0v to pin 9, creating open cicuit and no power going thru negative line
digitalWrite(relayPin, HIGH); // sets relay pin, pin 10 to 5v and switches relay and connects the common to the NO and creates circuit from sensor to amp.

}

float frq = 0;

void loop() {

digitalWrite(relayPin, LOW);          //set relay to NC and connecting polarising battery to sensor
delay (50);                                // small delay prior to polarising the coil
digitalWrite(mosfetPin, HIGH); // connects negative power supply through mosfet and polarises the coil.
Delay(4000);                              // polarises the coil for 4 seconds
digitalWrite(mosfetPin, LOW);      // cuts power thru negative supply
delay(50);                                  // small delay prior to switching relay to sensor circuit
digitalWrite(relayPin, HIGH);        // switches relay over NO state to allow sensor signal to amp.

lcd.clear();
lcd.setCursor(0,0);
FreqCounter::f_comp= 300;         // Set compensation
FreqCounter::start(5000);            // Start counting with gatetime of 5000ms
while (FreqCounter::f_ready == 0)         // wait until counter ready

 frq=FreqCounter::f_freq;            // read result
  lcd.setCursor(0,1);
    lcd.print(frq/5);
    lcd.print(" Hz");

 delay(1000);
}


texts: How can I measure the current and voltage of each source in a DC circuit with multiple sources?

texts:
In my off grid house I have a hydro-electric turbine and two separate solar arrays, each producing power at between 0 and 14.7 volts; nominally 12. The amperage varies, but the while system can peak at 50A on a clear day.

These sources are brought together so as to be in parallel through a main disconnect, at which point they are also in parallel with my AC inverter/charger and battery bank; there is a load-diverter that works with the inverter/charger to manage the batteries. Each has their own disconnect and fusing as appropriate.

I want to create a pretty comprehensive metering system using resistive shunts and Yoctopuce miliVoltRx units (posting to a RPi) that can measure and record current and voltage for each power source, as well and the battery bank. This is within the capability of the devices.

My Question is: because the DC system forms "one circuit", is it even possible to directly measure the sources; shunts are usually placed on the (-) side, does that isolate them at all? What does this look like? How can I do it?

I'm writing the software for the Yocotopuces myself, so if there is calculation combined with measurement necessary, that will be possible for me top implement. But designing that is beyond my layman's reckoning.

Sorry for not having a schematic. If it's necessary to understand the problem I can sketch something up.

Thanks for any advice!


texts: Dithering Modulation Frequency and Dithering Rate

texts:
I have a question regarding dithering.
I was reading this Application note and under section 4.1 page 5,they have given below,

I understand that we perform dithering in the DC-DC Switching converters to reduce the emission magnitude at the switching frequency and spread it across different harmonics.
In doing so, we would get a maximum switching frequency and a minimum switching frequency. In the above case, they have mentioned as 72kHz and 58kHz. But what is the meaning of dithering rate of 2kHz? Can someone explain me what is the meaning of dithering rate and how that value would impact or be helpful in this scenario?


texts:
Below is a MOV varistor:

Does a varistor have anode or cathode or polarity?

Can I connect the legs in any way or does it have an orientation like diode?


texts: Can a solar inverter be damaged if installed capacity is much larger than demand?

texts:
I had a dispute with my fellow. In his opinion, a power inverter can be damaged if the load is much lower (e.g 100W) than installed capacity (e.g. 10kW) of the solar system.

I am of the opinion that even in case of zero load, the inverter will not be damaged. Because as far as I know, power is "pulled" from the system and the current is not "pushed" from PV panels to inverter. The lower the load on the power inverter, the lower the load will be on PV panels. Right?


texts: Can I connect to my car's CAN bus with an ELM327 interface?

texts:
I've been fiddeling around with a Bluetooth ELM327 device I bought a few months ago and am able to get standard OBD information like vin, rpm, speed, etc. But as I just read about recently, OBD-II and CAN are not the same.

I've tried to sniff on my CAN bus with the AT MA command, but I get no response, so I guess the CAN network is decoupled from the OBD-II interface. Is there any chance to get access to the CAN network? Or might I need a different device to do so?

Maybe this information helps: I have a 2011 Škoda.


texts: How to write simple text or display image on the SSD1322 OLED display

texts:
As anyone been successful to display a simple text or a grayscale image to the OLED display using the SSD1322 controller like the Newhaven Display 25664?
I have managed to initialize the display using the provided sample code, now battling to display a simple text or image, I'm kind of stuck as the datasheet and application note doesn't guide much.
Any hint or reference example will be appreciated.
I am using PIC16F18877 with XC8 compiler but anything with an 8-bit microcontroller will be appreciated.


texts: Is setting software flags an effective use of interrupts?

texts:
I'm currently working on a microcontroller(Arduino) project in which I wish to use interrupts generated by pushbuttons and timers. However, I'm not sure if I'm 'effectively' using the interrupts. Here is my following architecture approach:

Let's say I have three interrupt sources: one tied to a digital input, and two tied to internal timers. Upon a hardware interrupt flag being set, the associated ISRs will run.

I also implement a 'main loop'. This main loop is untimed in the sense that it will continuously run as fast the processor allows. Within this loop, there is a series of software flags that are checked. These software flags are set in the ISRs. This loop is demonstrated in the pseudo code below:

/* main loop */
while(1)
{
    // Check digital input flag
    if(digi_in_flag)
        // do some routine

    //check timer 1
    if(timer1_flag)
        // do something routine

    //check timer 2
    if(timer2_flag)
        // do something routine
}

Now the reason I'm doing this is to keep the ISRs short. Essentially, my ISRs only set a software flag that is then checked in main loop. Some of these routines lead to SPI/I2C communications, so I didn't want to place those comms in an ISR.

So my question: does this make sense? Does this actually create a more efficient program? I feel like I'm still 'polling' by checking software flags. Alternatively to using interrupts, I could have written a loop that just checks a digital input (as opposed to a software flag set by an interrupt), or I could have just made a function to check time duration (i.e. curr_time - prev_time) instead of relying on a timer interrupt to set a software flag.

Any thoughts on this? Also, I'm limited to a single thread in this design.

Thanks


texts:
When button is pushed , active low RES pin is activated till Vc reaches 2.5 Volts. I have two questions  here
1. What is the role of Diode which is connected reversed biased?
2. Which loop capacitor discharges when button is pushed ?

Thanks beforehand!


texts: Why are these LEDs listed as 3W when the forward voltage is 2.4V, and forward current is 700mA?

texts:
The title of this listing says 3W:

http://www.ebay.com/itm/50PCS-3W-RED-80lm-640nm-LED-Plant-Glow-Light-Emitter-with-20mm-star-base-/221518318191?pt=LH_DefaultDomain_0&hash=item3393854a6f

But the specs that follow show a forward voltage (max) of 2.4V and forward current of 700mA. Wouldn't the power in this case be 2.4V * 0.7A = 1.68W and not 3W?


texts: What is the difference between RMS and DC?

texts:
The "RMS" value of an alternating voltage is equivalent to a DC voltage that would generate the same amount of heat in a resistor as the AC voltage would.  And RMS = 0.707 * Peak value  [N.B. Sine wave]

But the DC equivalent of the same wave is 0.636 * Peak value [N.B. Full wave]

I've seen the mathematics related to it for many years. But what does this mean? If the RMS is the heat equivalent, then what is DC? How are they different?

AC - RMS Reference
AC - DC Reference

I've included a full-wave rectifier and it's filtered output below.

1.Full bridge rectifier circuit.

2.Input of rectifier.[RMS]

The output of the rectifier.


texts:
I'm doing a project in which I will need these and I bought two to learn how to use them and daisy chain them. I'm using the 74HC166, and I'm having some problems. I'm using them according to the table function of the datasheet, which I attach:

So, it is a 8 bit PISO shift register. This is how I'm interpreting the table. I don't know how to read it so I had to guess and I obviously made mistakes.

If I want to load the states into the register, the PE and CE have to be LOW before I trigger the CP from LOW to HIGH. After that I can just start reading values from Q7, and to shift the value I will read from Q7 I have to trigger again the CP with PE being HIGH and CE being LOW. I don't know how to use, or when I should use the "hold 'do nothing'" row. and this doesn't work because I'm not reading the correct states. Right now I have just plugged the Dn pins to HIGH or LOW directly to try it.

This is the code I'm using:

/* Trigger a parallel Load to latch the state of the data lines,
*/
digitalWrite(clockEnablePin, LOW);
digitalWrite(ploadPin, LOW);
delayMicroseconds(PULSE_WIDTH_USEC);
digitalWrite(clockPin, HIGH);
delayMicroseconds(PULSE_WIDTH_USEC);
digitalWrite(ploadPin,HIGH);

/* Loop to read each bit value from the serial out line
 * of the SN74HC166.
*/
bitVal = digitalRead(dataPin);
digitalWrite(clockPin,LOW);
bytesVal |= (bitVal << ((DATA_WIDTH-1) - 0));
delayMicroseconds(PULSE_WIDTH_USEC);
digitalWrite(clockPin,HIGH);

bitVal = digitalRead(dataPin);
digitalWrite(clockPin,LOW);
bytesVal |= (bitVal << ((DATA_WIDTH-1) - 1));
delayMicroseconds(PULSE_WIDTH_USEC);
digitalWrite(clockPin,HIGH);

This should read the first two states. and I would loop over the "reading" parragraph to read them all.
PULSE_WIDTH_USEC is 5. (5 microseconds).

So, how do I use these registers.

EDIT: Ok, I just rewrote the code from scratch and it worked... It was probably something silly.


texts: Why are there only PID controllers, no PIIIDDD (higher order) controllers?

texts:
Transfer function of a PID controller is: \$I\cdot s + P+\dfrac{D}{s}\$

Are there controllers like:  \$A\cdot s^2 + B\cdot s + C+\dfrac{D}{s} + \dfrac{E}{s^2}\$ ?

If so, are they common? Why do people usually just use a PID controller?

Someone asked me why I asked this question. It is because of this post actually:
https://robotics.stackexchange.com/questions/7853/how-to-tune-pid-for-a-yt-kxt-system

I asked a question on PID controller and there are arguments that the PID controller shall not be followed by an integrator. However, in both real tests and simulation, PID-integrator controller(I only used PI-Integrator) beats pure PID controller. A PI-Integrator Controller is actually an I-II controller with transfer function of \$\dfrac{D}{s} + \dfrac{E}{s^2}\$.

Please correct me if I made any mistake.


texts: Is a full-wave rectifier really required with a 7810 regulator?

texts:
I'm possessed of a 12-0-12 500mA transformer.

To supply a stable 10V, I seek to connect a bridge rectifier, roughly filtered with a 1000uF/50V electrolytic capacitor and a 7810.

Is a bridge, or even a FWR really required with the 7810?
Is the 7810 capable of handling the pulsed output of a HWR?


texts: How to have a micro-controller detect doorbell?

texts:
I live in an apartment were everyone has an individual doorbell on the front gate. When the button is pressed for my apartment, 21VAC rings a bell in my unit. I would like to have a micro-controller detect when this is happening.

My initial thought was to put a reed switch next to the bell, but it seems the reed switch is too sensitive and would get triggered when my bell was not on. My guess is that this is due to interference on the line from other apartment's doorbells, but I have not been able to verify this.

Now I'm thinking of using an AC relay, but I'm having some trouble finding one that would work with my voltages. I'm also looking into using an optoisolator, but know very little about them and am not sure of the pros/cons vs. a relay.

So my questing is, should I use an AC relay, an optoisolator, or something else?
And for whatever solution, which part would be best?

Thanks.


texts: What do I risk by putting a 40W tip on a 50W iron?

texts: All I have on hand is a 40W tip and a Weller WES51 (50W). I plan to work for about 8 hours. Can I do any major damage to the iron or the work?


texts:
The formula for the characteristic impedance is below

So the characteristic impedance is a complex number. But why is a complex termination generally not used?
With complex termination I mean a transmission line terminated by more than just a resistor. Maybe a resistor and a capacitor.


texts: How is it possible to have high voltage that is safe?

texts: I am aware that current is very dangerous and only 0.2 amps is enough to stop a heart. However I always see that high voltage is dangerous. Tasers produce a high voltage but since there is low current it is considered safe. How is it possible? According to Ohm's law, Current is equal to voltage divided by resistance (I=E/R). So if you are being tased by 10,000 volts and your resistance is only 1000 ohms, wouldn't there be 10 amps flowing through you and killing you? (10,000/1000= 10)


texts: Feedback on USB-C Power + LiPo Battery + Nema 17 Stepper Motor PCB Design

texts:
TL;DR: I need a technical check on my circuit design that utilizes LiPo battery & USB-C charging.

Hi everyone,

I've been working on a project to build my own camera slider. It's powered by Sparkfun Pro Micro and A4988 Stepper Driver Modules. Right now, I'm using only one stepper motor but I do want to have the option to have two more stepper motors for more degrees of movements in the slider. Each motor is rated at 12V and 0.4A/phase.

I'm designing the PCB (on EasyEDA) and I have a few constraints in terms of how it will be powered; either through a USB-C connector or the LiPo battery. The battery itself can also be recharged by the USB-C port. As for the power through the USB-C port, I'm going with the standard 15W option (5V & 3A) so I don't have to deal with the whole USB-PD circuitry BS that comes with it. There is a switch that will turn on the Arduino & motors from either the battery or USB-C power source. When the switch is off, the battery can still be recharged if the USB-C is plugged in.

For the components, I'm thinking of choosing this battery from Adafruit as it should provide enough power for now. I also found this YouTube video from Electronoobs on battery charging and boost converting so I followed along for my circuit design. I mixed and matched to try to fit my need. I've attached a screenshoot of the circuit that involves the power management. Note that the "C" and "NO" nets are the common and normally-open pins of the power switch. The diode "D2" is to force the anode (+ side) to flow the positive/conventional current from the battery to the boost converter and not back into the TP4056 recharging IC. Diode "D1" is to prevent the 5V current from the USB-C Vbus to flow to the anode of the battery which is 3.7V.

If you see any potential problems with my design or got some questions, please comment on it. I'm still very new to this area of circuitry. Thanks!


texts:
The circuit that I am simulating is a Vishay PTC thermistor model number PTCTL7MR100SBE.
I have a timestep too small error when trying to simulate.
The link for the SPICE model.
I tried running the PTC through a pulse voltage of 500V with a rise time of 0.4us and a fall time of 1ps. The error seems to be happening at the fall time.
Can anybody advise me on how to solve the error?


texts:
I wish to find out the right combination for my quadcopter.
I have 2300 KV motors (4), 12 Amp ESC (4) and 3S 2200 mah 20C Battery. I have read this combination is great for a 300 mm quadcopter. However, it seems my math is slightly off.

The battery will provide me 44 Amp current at any time. However the 4 ESC will demand 48 Amp. Should the battery be changed to higher rating.

I don't know how to determine 2300 KV motor requirement. Will the above ESC and battery be sufficient for the motor? I know weight of QC and size of propellers are also additional factors. Hope someone can explain how these must be matched.


texts:
I am designing a PCB with an RJ45, discrete magnetics and an ethernet phy that can support 10/100/1000 speeds. I am considering the implementation of ESD/TVS diodes. For this I gathered the following:
-> Working voltage Vrwm of diodes must be greater than the signal voltage. Voltage levels are +/- 2.5V.
-> Junction capacitance must be less than 2.5pF (according to TI) as we're dealing with high speed signals
I am, however, unsure about the following design requirements:

What must the clamping voltage of the diodes be? Will this depend on the phy selected?
I mostly see the diodes be placed on the secondary side of the magnetics, what is the reason for that? It makes sense to me to place the diodes as close to the RJ45 as possible, ensuring shortest possible path to GND during ESD strike.
Since the ethernet diff pairs are truly differential and not referenced to GND, how must the diodes be arranged? What rails will the signals be clamped to if the diodes aren't GND referenced as in the image attached? Where will the ESD strike feed into?
Some designs use integrated diode with 'steering diode' and TVS diodes. What is the purpose of having both?


texts:
This may seem like a dumb question, but I want to be sure. In the below datasheet, what is the DC voltage the relay can handle? I am assuming it is the Contact Capacity 24 VDC, 1 A.

Micro 1A SPDT Relay
(275-0240)                 Specifications             Faxback Doc. # 45621
Contact Form: ....................................................... SPDT
Contact Gap: ..................................................... 0.15 mm
Contact Pressure: ....................... 3 grs. Min. at center of contact
Contact Capacity: ........................................... 125 VAC, 1 A
                                                               24 VDC, 1 A
Coil Voltage: ...................................................... 5 VDC
Min. Puck-Up Voltage: ........................................... 3.75 VDC
Nominal Coil Current: .............................................. 90 mA
Coil Resistance: .......................................... 55 Ohm +/- 10%
Operating Time: ............... 10 milli Seconds Max. at nominal condition
Release Time: .................. 5 milli Seconds Max. at nominal condition
Temperature Range: ................... -25 to +55 Degrees C. @ 60% RH Max.
Humidity Range: ...................... 95% RH Max. from 5 to 35 Degrees C.
Dimensions (HWD): .............................. 0.35 x 0.41 x 0.29 Inches
                                                     (9.0 x 10.3 x 7.3 mm)

Specifications are typical; individual units might vary. Specifications are
subject to change and improvement without notice.

(EB 11/26/97)


texts: Is the STM32 DMA destination address restricted?

texts:
I'm using a stm32f446 and would like to use the TIM4_CH2 request with the DMA1 in Memory-to-peripheral mode to transfer data from an array to the ODR (output data register) of a GPIO port.

For some reason it only works with some destination addresses (and not with the &GPIOx->ODR address), even through the reference manual states at 9.3.6 Source, Destination and transfer modes:

  Both source and destination transfers can address peripherals and memories in the entire 4 GB area, at addresses comprised between 0x0000 0000 and 0xFFFF FFFF

Is there any further restriction I should be aware off?

HAL_TIM_OC_Start(&htim4, TIM_CHANNEL_2);

uint16_t buffer[] = {1,2,3,4,5};
uint32_t dataLength = sizeof(buffer)/sizeof(buffer[0]);
uint32_t srcAddress = (uint32_t) buffer;
//uint32_t dstAddress = (uint32_t) &(TIM4->CCR2); // Works
//uint32_t dstAddress = (uint32_t) &(TIM4->CCR4); // Works
//uint32_t dstAddress = (uint32_t) &(TIM5->CCR4); // Doesn't work
uint32_t dstAddress = (uint32_t) &(GPIOC->ODR); // Doesn't work

HAL_DMA_Start_IT(&hdma_tim4_ch2, srcAddress, dstAddress, dataLength);
__HAL_TIM_ENABLE_DMA(&htim4, TIM_DMA_CC2);

The DMA initializing code:

hdma_tim4_ch2.Instance = DMA1_Stream3;
hdma_tim4_ch2.Init.Channel = DMA_CHANNEL_2;
hdma_tim4_ch2.Init.Direction = DMA_MEMORY_TO_PERIPH;
hdma_tim4_ch2.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_tim4_ch2.Init.MemInc = DMA_MINC_ENABLE;
hdma_tim4_ch2.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
hdma_tim4_ch2.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
hdma_tim4_ch2.Init.Mode = DMA_NORMAL;
hdma_tim4_ch2.Init.Priority = DMA_PRIORITY_LOW;
hdma_tim4_ch2.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
HAL_DMA_Init(&hdma_tim4_ch2);

__HAL_LINKDMA(htim_base,hdma[TIM_DMA_ID_CC2],hdma_tim4_ch2);

Timer configuration:

TIM_ClockConfigTypeDef sClockSourceConfig;
TIM_MasterConfigTypeDef sMasterConfig;
TIM_OC_InitTypeDef sConfigOC;

htim4.Instance = TIM4;
htim4.Init.Prescaler = 0;
htim4.Init.CounterMode = TIM_COUNTERMODE_UP;
htim4.Init.Period = 72;
htim4.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
HAL_TIM_Base_Init(&htim4);

sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
HAL_TIM_ConfigClockSource(&htim4, &sClockSourceConfig);

HAL_TIM_OC_Init(&htim4);

sMasterConfig.MasterOutputTrigger = TIM_TRGO_OC2REF;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
HAL_TIMEx_MasterConfigSynchronization(&htim4, &sMasterConfig);

sConfigOC.OCMode = TIM_OCMODE_TOGGLE;
sConfigOC.Pulse = 0;
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
HAL_TIM_OC_ConfigChannel(&htim4, &sConfigOC, TIM_CHANNEL_2);


texts: Do MOSFETs have voltage drop across source and drain when turned on?

texts: Like diode and BJT having around 0.6V drop, is there any voltage drop across the MOSFET drain and source when the MOSFET is turned on? In the datasheet, they mention diode forward voltage drop, but I assume that it for the body diode only.


texts: Why are these two same rated metallized film capacitor physically different

texts:
I ordered a 2.2uF, 250VAC metallized film capacitor from ebay http://www.ebay.com/itm/NEW-CAPACITOR-225K-250V-2-PIECES-/270914925705 to replace a capacitor in my APC UPS of the same rating.

In the picture of the two below (larger one is from APC UPS; the one I intend to replace), there is a disparity in the size, and that worries me.

Although both are of the same thickness, the difference in the length * breadth between them concerns me, as given the same dielectric, the amount of the film determines the capacitance and ESR, among other things.

I don't have an ESR meter with me, but I measured both capacitors and they were around 2.2uF, so their values agree.

Hence, I would like to ask what the difference in size might imply as far as their characteristics are concerend, given that both measure the same value?

More importantly, would it be safe to replace the original cap with the smaller one I bought on eBay?


texts: Does the transformer in this circuit cause a voltage drop to the DC motor?

texts:
In this circuit:

Is the transformer and the circuit on the secondary side of the transformer only there for the test-point or does it affect the voltage to the DC motor?

The DC motor is a 90V motor and the AC signal that is switched on with the relay is a 120VAC signal.


texts: What other units can influence the way a wire glows than watt?

texts:
I have a vape device with a mod that lets me  configure the power I want to operate it with and also as an additional setting that is called vape strength which can be set to soft/medium/hard.

When operating it on soft it generates just medium amount of light vape. On hard it tastes most of the time burnt.

So my question is, what electrical unit can influence this options, given that the power is set fix?


texts:
I made a board with an AVR Attiny MCU and an ISP connection. I missed that I made the SCK pin an output for an LED. Luckily, this arrangement seems to work; I can program the chip just fine. But, during programming the SCK signal from the programmer is driving the LED on. Is this ok in principle or did I just get lucky that it works?

Please see the attached schematic which shows basically how my board is connected during programming. Assuming the following- the SCK pin (PB2) must be used as the LED output pin, the value of R1 cannot be increased, and the programmer will never be connected while the SCK pin is driving the LED- what could I have done to the circuit to improve the situation?


texts: Why are microcontroller flash memories separated into sectors?

texts:
Take as an example the stm32f429. The flash memory is separated into 11 sectors:

sectors 0,1,2 and 3: 16KB each

sector 4: 64 KB

sectors 5-11: 128 KB each

What is the deal here?


texts: How to power 24V/5V equipment on mains and battery

texts:
I'm trying to power some scientific equipment that requires 24VDC/~4A on both mains and battery with solar eventually coming to the mix. In addition, I'm using a Raspberry Pi as the datalogger, which requires 5V/~1A. I'm trying to make sure that I don't start a fire when I do this. As will be evident below, I'm a scientist and not much of an electrical engineer.

This is my current plan: Mains (120V) -> some sort of 120V->24V converter, like this one ->two 12V batteries connected in series (I suppose I just connect the 24V to the + of one and the - of the other)-> split to a 24V->5V converter like this one and to the equipment.

The batteries will be expected to power the unit for ~4hr, so I am aiming for 18Ah batteries. The mains->24V will be expected to be inside, but we will disconnect the batteries et al and expose them to the elements from time to time. The current plan is to house them in a pelican case. That only needs to contain the Pi and everything from the battery onward.

No strong weight restrictions other than "not absurd". Aiming to have low electrical noise on at least part of the circuit- the instrument separates into a heater and instrument part, and the relatively low power instrument part (~500mA) should be pretty clean, but the heater can be pretty noisy. Appearance doesn't matter that much, but something that is clean/"looks safe" would be preferred as it's scientists working with this.

Three main questions here: will I start a fire/electrocute myself? Do I need a charge regulator for this setup or will that only need to come when I move to solar panels? Have I appropriately designed this setup to work?

Finally, one dumb question (although these may all be dumb): what kind of wires/terminals are safe to use to hook this all up? Should I get some kind of fused mains plug to go to the 24V power supply?


texts: How to make LT1168 instrumentation amplifier work with single supply?

texts:
I am using the LT1168 instrumentation amplifier for my project and I am trying to figure out how to make it work with a Li-Poly 3.7 Volts battery. I am not able to understand the single supply operation theory from the datasheet. I have given +3.7 volts to the V+ pin and the V- pin is grounded but I am unsure what has to be given to the Ref pin of the opamp.

Here's the link to the datasheet: http://cds.linear.com/docs/en/datasheet/1168fa.pdf

It would be really helpful if you guys can kindly help me with the connections to make it work with a single supply. Thanks.


texts: Ultrasonic module Water proof vs non-water proof types

texts:
Ranging SR04 Ultrasonic modules are available as water proof and non-water types.

In the water proof types SR04 modules there is only 1 sensor while in the non-water proof types SR04 there are 2 sensors, 1 as transmitter 1 as receiver. How does the  single sensor SR04 water-proof modules work with single ultrasonic sensor?


texts: Is there a current in \$R_1\$ in this precision rectifier if so, where does it go?

texts:
So Wikipedia on Precision Rectifier says that :

... when the input is greater than zero, \$D1\$ is off, and \$D2\$ is on, so the output is zero because the other end of \${\displaystyle R_{2}}\$ is connected to the virtual ground and there is no current through \${\displaystyle R_{2}}\$

Now when we see \$R_1\$ it has a potential drop of \$V_{in}\$ across its ends , so a current must flow through it. But then where does it go? I cannot see a closed loop in which current can flow. It can only go through \$D1\$ but then it cannot flow back into op amp.
So my question is : In which path does the current flow? or If there is no current flowing through \$R_1\$ how is there a potential difference across it?


texts: Difference in output between digital codec and analog filter

texts:
I'm working on a project which deals with filtering audio signals with a Low Pass Filter and amplifying the output. Currently, we are solving this using the TLV320AIC3111 audio codec by Texas Instruments, controlled by an STM32L476RG.

Using TI's proprietary software PurePath Studio, I've coded this filter below.

Our test setup is described below

Function Generator -> External Class D Amp -> External Speaker -> Microphone(codec input) -> Codec -> Speaker(codec output) -> External Microphone -> Oscilloscope

Using basic python code, we plotted the frequency response graph as below.

However, when we directly connect the frequency generator to the codec and the speaker output to the oscilloscope, we get a much better response as below.

When I connect the external speaker to the external microphone directly, (with no codec in between) we get a response as below.

Due to the similarity between images 2 and 3, I think the setup is not appropriate as external speaker and microphone are interfering with response.

However, when we use the same setup with an active analog filter with op-amps and similar filter specifications we get a proper response with none of the spikes observed in either of the aforementioned images.

I am having trouble figuring out why there would be such a difference between analog filter and codec filter. Can anyone guide me on this matter?


texts: How can V-USB screw up the built-in SPI of an ATmega328p?

texts:
I'm working on a V-USB project that shows up as a Keyboard using an ATmega328p. The USB part is working great (it's not my first V-USB project), but after I start the V-USB stack with usbInit(), all calls to the SD card library fail. If I call the same functions before usbInit(), everything works perfectly.

I use an Arduino clone called Diavolino, but without the Arduino/wiring framework. I have the USB connected to digital I/O 2 and 3, and the SD card to 10-13 (built-in SPI lines).

I looked through the SD card library and found no sign of it using any interrupts or registers other than SPxx. I also grep'd though the V-USB code, but it doesn't even touch the SPxx registers.

The first sign of the problem was when the device disconnected when it was supposed to access the SD card. Then I put usbPoll() and wdt_reset() calls into all SD card handling loops, and found that in case of writing, the card waits forever for acknowledgement from the card after having sent the last two bytes (CRC-16).

The SD card library I use is sd_raw by Roland Riegel.


texts: Best method to eliminate alternator whine from a 12V line?

texts:
I've purchased a Miccus Mini-Jack Rx BlueTooth audio receiver.  This device will accept a bluetooth signal from my phone and output it to a headphone jack that I plug into the AUX-In on my car stereo.  Works great.

Current setup

I do get a little alternator whine when I have the USB charge cable plugged into the device.

I was thinking of purchasing a DC-to-DC power convertor like this one and install it inline with a new 12V power line from the fuse box and take the 5v output straight to a female USB plug.

Is this the best route?  I've read quite a bit about people installing capacitors between the 12+ and the ground as well to help dampen the noise.


texts:
I'm experimenting with an Arduino Mega, using it to test some relay logic. The Arduino is powered from my benchtop power supply via the Vin and GND pins.

I have digital output pins connected to some 2N2222 transistors to drive the relays. Here is a rough schematic:

The relays are four DPDT relays configured as a full adder.

The problem occurs when I try to reset the Arduino by removing the the power. When I disconnect the +5v pin, the Arduino stays on and the relays stay energized. If I short the +5v pin to ground, that successfully resets the Arduino and the relays turn off.

How is the Arduino receiving power when +5v is disconnected? Does it have something to do with the transistors? How can I ensure that the Arduino is only turned on when I want?

EDIT It looks like this was a PEBCAK error; I had the Arduino board resting on top of my breadboard where some detritus was apparently shorting one of the power pins on the bottom! Problem is fixed now.


texts: How to repair accidentally removed solder pad?

texts:
Disclaimer: Pardon my lack of knowledge on the following
So while I was trying to de-solder a keyboard switch I accidentally removed the solder pad (top arrow) and not only that lost it as well in the process... Perhaps the damage is done but is there a way to fix this and to test the keyboard switch before re-soldering? Right now there is no response by just "attaching" the key to the board and pressing... any ideas or direction on to how I could fix this?
Thanks a bunch!


texts: Instrumentation Amplifier Connection Problem

texts:
I am trying to build a circuit capable of measuring ECG signals following the scheme attached.

Since AD623 was out of stock, i ended up buying something like this: https://www.arduino-tech.com/cjmcu-8221-ad8221ar-precision-instrumentation-amplifier-module/.

My concern is now: how should i or better said, where should i connect the GND pin from the module?

As far as i can tell, after analyzing the breakout board, the module comes equipped with the input resistances, gain resistance and the capacitors outlined by me in the red square.
I followed the presented scheme accordingly, built the driven ground circuit and connected the +VSS pin to the V+ output, the -VSS pin to the V- output and the GND pin to the AGND. Afterwards, since i don't want diode protection for the time being and since the previous assumption, that the module already has the input resistances, i took the 47K ones and put them on the left of the 1M ones with the view of acting as protection resistors.
Everything else was kept intact, i only disconnected the right driven leg circuit, because i also don't need it from now, but i was unable to obtain any output.

I should mention that i tried to isolate only the INA block to see if it works, and this is ,i think, where the problem is located. The datasheet (https://www.analog.com/media/en/technical-documentation/data-sheets/AD8221.pdf) specifies to tie REF to the appropriate local ground, so i assumed it must be linked with the AGND.
So this is my configuration at the time being:  -VSS pin to V-;  GND pin to AGND; +VSS pin to V+; REF pin to AGND. On the IN+/IN- i tried to gather signal both from electrodes located on the skin and from a 5khz generator but i got nothing. The generator was connected with its ground to AGND, and with its output to one 47K resistor and then on both 47k resistors tied together and no result. The only concerning result i had was the fact that at one point i was reading from the output a 50Hz signal, whereas both my circuit and the generator where powered from 9V batteries, and the oscilloscope, a Hantek 6022 one, was connected to the PC, which was not plugged into the power-line socket.

So, again, what i am asking is:
How to properly connect the breakout board, since there must be a problem with the AGND driven ground potential and the mismatch with the REF/GND pins from the module. (I will also recheck my soldering job for any discontinuity, just to be sure.)

Thank you for your answers!


texts:
I know that the first instruction stored in BIOS is "mapped" to memory address 0, and that a signal on the reset pin to the microprocessor causes this instruction to be fetched, beginning the POST and all the chain-loading involved in the boot process.

I also know that there is a Memory-Management Unit (MMU?) at the hardware level. Is it in charge of doing this redirect (away from DRAM to the BIOS firmware) so that the processor can interact with the memory of the computer in a blissfully naive way? If so, what other areas (in addition to BIOS) does the MMU map into the total address space?

I know that for modern operating systems with a GUI, the displays are "bitmapped". Does the MMU map a portion of the video RAM on the video card into the global address space as well?

What about virtual memory and paging? Does the hardware MMU have any intrinsic capabilities that facilitate the virtual memory feature provided by the OS?

I may be way off.


texts:
Which is the difference between doing a voltage dividers from 5V to 3.3V with 10k and 20k resistors vs 4.7k and 2.4k?

It s easier to use the first option.


texts: The reason the advantage of Single conductor transmission line be changed to non-singular conductor transmission line

texts:
Question:
If Single conductor of EHV(Extra high voltage) transmission line be changed to  non-singular conductor of EHV transmission line,there are some advantages about this changing

1.Decrease the potential gradient in the surface

2.Decrease the inductance of transmission line

3.Increase the capacitance of transmission line

4.Improve Corona discharge

5.Improve radio interference

It is easy to understand the reason of "3.Increase the capacitance of transmission line ",does anyone know the reason about the other advantages?


texts: How suitable are GaN half-bridges for small brushless motor drives (ESCs)?

texts:
The drone world uses ESCs (Electronic Speed Controllers) to control brushless DC motors.  Typically there are six discrete FETs, a driver IC, and a small MCU to sequence things.  Typical currents range from 5-100A at 3-25V.  For many of the smaller drones weight and PCB area are at a premium.
I'm wondering if GaN Half-Bridge arrays would help out here.  With typically lower gate capacitance, Vt, and great Rds(on) at a 5V drive would we really even need to have a driver ?  Could the MCU logic outputs (assume to be 5V levels for now) be utilized directly ?  If so the package count would drop from eight to four, and with CSP GaNs the area would be dramatically reduced.  I've not found any small multi-phase GaN half-bridges specifically in the 5-10A @5-10V range, does anyone know of any ?


texts: A passive differential to single-ended load match

texts:
I'd like some suggestions for some passive differential to single-ended speaker audio level matching circuits for a particular situation where an external power source for an amplifier is not available.
Ideally as little as possible attenutation from input to speaker, but essentially what is a common simple practice in the audio world that one might consider ?

The circuit below is what I had in mind, with the input from an external amplifier for driving a small speaker or a headset speaker. The actual speaker on the far-end is always ground-side connected. The input however could be differential or single-ended so having an option to short one of the 16 Ohms resistance with a MOSFET or a depletion mode analog switch would be great but not essential...

Any thoughs would be greatly appreciated ...
regards, Mike


texts: Possible causes for sore ear when using audio amplifier (PAM8302A) and speaker at a reasonable volume

texts:
I've been working with a PAM8302A analog audio amplifier from Adafruit and added a second order low pass filter (2 x 470Ohm resistors and 2 x 2.2uF capacitors) to get rid of some of the audio feedback that occurs when the analog mic (Electret condenser mic with MAX9814 mic amp) is near to the speaker.

I've noticed that when I am testing it out and have the speaker near my ear (less than a foot away) for even less than a minute then my ear starts to bother me even when the audio from the speaker is not very loud.  I do have reasonably sensitive ears and pay attention to when they start to hurt and don't like loud concerts etc because of that.  I would classify my hearing as pretty normal.
I've used an app on my phone (an instrument tuning app, Tunable) to detect the frequencies from the speaker and I've noticed that when I turn the amplifier on and off by connecting or disconnecting the power (and not changing the SD signal prior to shutdown) that there is a 10kHz burst of noise.  I sometimes hear a little crackle but the audible noise doesn't seem like it could cause a problem because it is not loud.
Here is a screenshot from a spectrum analyzer.  There is a spike over 22kHz (I'm able to tap on the far right and it displays 22165Hz and that is to the left of the rightmost spike)

I am considering getting an oscilloscope to search for frequencies from the audio out.
What could be the cause of the ear issue or how can I troubleshoot it?
*** Edit to add spectrum analyzer screenshot. ***


texts: Create variable mechanical resistance to dynamo spinning

texts:
I want to make a system with a dynamo where the dynamo can be made harder to turn (as a fitness device) and I want to be able to use an electrical signal from an arduino or similar to control the turning difficulty.

I guess that if I put a lot of small ohm resistors in parallel then this will make the dynamo harder to turn as more power is required, then relays could be used to connect and disconnect these resistors, with more resistors being connected to make turning harder?

Or is there a simpler way to do this with transistor control?


texts:
This is a really basic topic but it's getting me confused.
The truth table for any gate remains the same for both positive and negative logic, right?
like for a NOR gate the truth table would always be,

x    y    x nor y
F    F       T
F    T       F
T    F       F
T    T       F

for both positive and negative logic. right?
Then for a negative logic nor gate the truth table would be,

 x       y        x nor y
1(F)    1(F)       0(T)
1(F)    0(T)       1(F)
0(T)    1(F)       1(F)
0(T)    0(T)       1(F)

now look at this. the table for negative logic nor says 1 nor 0 = 0. So what am i missing?
thanks..


texts: Why did a hot/neutral reverse lead to an HDMI cable shocking me?

texts:
I recently set up a new TV/home theater system for my dad. The TV had 3 HDMI devices plugged into it. I plugged a 4th HDMI cable into the TV, and as I reached for the opposite end of the cable with the intent of plugging it into another HDMI device, I received a shock from the metal shield on the HDMI connector. This was not a brief static electricity shock--it was a sustained, AC shock that went up my hand into my wrist.
I investigated the outlet powering the TV and associated equipment (all plugged into the same surge strip), and I found that 1.) hot and neutral were reversed, and 2.) although the outlet had an earth ground prong, the house actually has no wiring for an earth ground (it's an old building). I replaced the outlet with a new GFCI outlet, correcting the hot/neutral reverse. After making this change, I found that the HDMI cable no longer shocks me.
I have found several posts around the internet discussing similar situations, and suggesting that a hot/neutral reverse is a common culprit. However, I am struggling to understand why exactly this wiring issue would lead to the HDMI cable shocking me. Most of the devices plugged into the power strip at the time of the shock (TV, cable box, AV receiver, etc.) were 2-prong, double-insulated devices. My understanding is that these devices do not "care" whether hot and neutral is reversed, and electrically isolate their shield/chassis from both hot and neutral. There was one device with a 3-prong plug (a computer) plugged into the surge strip (but not the TV) at the time of the shock, but I'm not sure whether that's relevant.
So, could someone please help explain: how does a hot/neutral reverse lead to mains voltage leaking into the HDMI shield of a double-insulated device?
Many thanks!


texts: How to use an H-clock tree in a pipelined adder

texts:
This is for a lab at my university. Normally I don't have a problem with these things, but this one is poorly written and the professor hasn't discussed the H-clock tree, which is where I'm getting confused. Essentially, the goal of this lab is to create an 8-bit pipelined adder and use an H-clock tree to provide the clock pulse to the sequential elements of the design. We'll just consider the gate/component level schematic here.

Here's what I know:

How to create the pipelined adder: use two 4-input adders (already created) and stick D-Flip-Flops (also created) in between the stages and at the inputs/outputs to synchronize the calculation. Basically, do what's shown below, but with only two stages instead of three:
How to create the H-tree for the clock. It should like like image b) below:

However, I'm unable to connect the two concepts in my mind, or even understand why the clock tree is necessary. Here's the part from the lab manual that I'm stuck on:

  Use the buffered H-tree clock distribution scheme to provide clock signals to the
  sequential elements in your design.

How do I use the clock tree to distribute the clock signal to the flip-flops? If I have X flip-flops, do I need a tree with at least X branches, and use one branch for each flip-flop? How is using the tree different from just wiring the clock input directly to each of the flip-flops?


texts: Quality Factor and Frequency Bandwidth in a matching network

texts:
it is known that the Quality Factor appears in the formulas for transformation of an impedance series bipole to a parallel one. A simple example is this one:

Now I have three questions:

1) I have always been told that the quality factor is the reciprocal of the fractional bandwidth (calculated by using as reference an attenuation of 3dB with respect to the peak of the impedance/admittance of the circuit considered). Is this relation true for any circuit with (at least) one reactive element and a resistance? Or is it necessary to prove it for each circuit?

Now, let's consider a L network, for instance this one (ignore the values of Cp and Ls):

It may be used, as in this case, if we have a certain resistance RL and we want that an external device sees a value R. Therefore:

2) We insert a parallel capacitance and then a series inductance. The second one is used to balance the reactive part introduced by the capacitance. Precisely, its admittance has to cancel that of the capacitance. In this way the total impedance seen by the external device would be totally resistive and equal to:

Rp = RL (1 + Q^2).

So we may impose that Rp = R (known); we know RL. Therefore Q^2 is determined.

Have I understood it correctly?

3) The quality factor is function of frequency. Therefore, it seems to me that a certain transformation from series model to parallel one (or vice versa) is true only for a certain frequency. But we have said that Q is related to the fractional bandwidth, so it seems to me that the transformation is true for all frequencies inside that bandwith. Which is the truth?


texts: Analog/Digital ground vs Power/Signal ground

texts: Are these ground plane separations on a PCB equivalent, or if I am already separating my ground into analog and digital parts should I also divide it in power and signal areas?


texts: Increase the size of ltspice error log file contents

texts: In my circuit when I am sweeping many values and total combinations are higher (>2K), only initial values are captured when using .measure command for each combination. I want to increase the amount of text being saved in spice error log, so that .measure output gets saved till the end of all combinations.


texts: How to determine received signal strength including reflections?

texts:
I have an RF system with known transmit power, transmit antenna gain, receive antenna gain, distance, and frequency (900MHz ISM band).

I can calculate direct received signal strength based on those parameters alone, but how does that change with surface reflections? I can easily figure out the incidence angle, but how do I calculate the resulting signal strength as a superposition of the two waves?


texts: Need help with incorrect operation of the HIP4082

texts:
Trying to run HIP4082 according to the Datasheet. I use 1uf, delay resistor - 10k capacitors. At a constant 12 volts on the BHI BLI and ALI pins, the motor rotates with some pulsation. But  if i give PWM in ALI pin, then chip stop working and gets very hot. What could be the problem?

DataSheet


texts: Cannot find ATSAMS70N21A-AN lead width and lead length?

texts: I have trying to make a breakout board for ATSAMS70N21A-AN. I then tried to design the footprint in KiCad, so when I was looking for the dimensions on the datasheet I couldn't find the lead width or length. Where would I find these dimensions? It is an R-LQ100_U Package.


texts: Replace an Analog Pot with a digital one?

texts:
I have a Boost converter with a constant current mode that allows me power a high power led (Vf 34, 3A). I'd like to be able to control the current potentiometer on this device with an arduino.

To do so, I was thinking I could swap out the analog potentiometer with a digital one. I looked it up, and found this page from Analog Devices about their digital potentiometers. However, I have no idea which to choose. The potentiometer I'd be replacing is a 3 terminal, Baofeng 1/4W 10K
potentiometer.

I don't have much experience with DAC/ADC, so I'm not sure if this is the best way to do it.
I also looked into replacing the PWM chip on the boost converter with the arduino's pwm output, but the chips are unmarked.

I also looked at using a TIP120 with the arduino's PWM to change the brightness, but I don't think this would be the best, as it might cause surges of power.

I can include actual photos of the device, but this is the device in question. I'd ideally replace the current potentiometer, as it would allow me finer control.


texts: What type of 24 VDC to 730 V converter is this?

texts:
The circuit below converts 24V DC into 730V. The circuit looks like a flyback converter but from what I know with the full-bridge rectifier at the output it can't behave like a flyback.
The feedback connection is actually via a voltage divider and an optocoupler but I just simplified it for easing the sketch(when the output is 730V optocoupler is activated and the PWM generator decreases its duty cycle).
Transformer's N2/N1 ratio is 40, and the PWM generator's output is at 33 kHz.
I thought this is not a special type of converter what it does only boosting the voltage which is kind of AC because of PWM switching by dividing the input by turns ratio of the transformer but after some measurements I'm a bit confused.

Here is the drain terminal voltage of the MOSFET( in yellow) and the gate voltage( in pink):

From the drain voltage measurement it can be said that the primer voltage of the transformer oscillates between -14 and +16 V, but from what I think how this circuit works the peak value of the output is supposed to be 16*40= 640V which is not true. This is where I'm confused.
I've tried disconnecting the bridge rectifier and replaced it with a diode and circuit works almost exactly same.(except the current increased with time but that must be because of the heat on the diode)
What I want to know is that how this circuit can output 730V with the full-bridge rectifier at the output.
I'm sorry for the lousy hand sketch and photo quality.
Here is the schematic I got:

https://i.stack.imgur.com/IKsMZ.png


texts: Understanding when certain components need a lower voltage

texts:
When looking at electronic modules to buy (WiFi, sound etc) many descriptions say that the module cannot use a 5V input. But the 5V supply can be used if it's stepped down to 3.3V (or whatever is needed).

What I don't understand is that when I create a series circuit with a 9V battery and some LEDs that have a drop of 2V I don't need to step down the battery to 2V, the LEDs use only what voltage they need.

So why don't modules just take only the voltage they need? Why does the input need to be explicitly reduced?


texts: There are modules that I have purchased that are already built on a PCB, and I would like to integrate them into my board. There is a TO-220 case which is a transistor on the bottom side, and it is bent into the board(legs are bent at 90* and tab is soldered on the board). Integrating it to my existing PCB, is it possible to lay the black side/front side into a copper area? Would this help with the cooling or make no effect at all?


texts:
Just been reading this where this statement is made:

  If the patient is in Ventricular tachycardia (VT) or ventricular
  fibrillation (VF) on the monitor, immediately apply the pads and shock
  the patient with 120-200 Joules on a biphasic defibrillator or 360
  Joules on a monophasic defibrillator.

That seems like a huge energy to dump into someone. Do they really do this?


texts: Using an MCU with built-in CAN controller vs. external CAN controller

texts:
I'm planning to use the Atmel ATSAMC21J18A microcontroller in an automation project which has a built-in CAN controller. The CAN bus network may contain 32 devices, each generating data packets in 1 second intervals. There will be 16 such CAN bus networks connected to a single gateway node which has an NXP LPC1768 MCU (Cortex M3).

What are the factors and parameters that should be considered when deciding whether to use the built-in CAN controller or an external CAN controller?
Are there any pros/cons/constraints while using the built-in CAN controller?
Since the CAN gateway node will be handling traffic from all 16 networks, would it be a good idea to use an external CAN controller to avoid buffer overflows?

Note that I'm anyway planning to use an external isolated CAN transceiver.


texts: Why the actual charge current of a battery is not improving when I shifted to larger current capacity battery charger power supply?

texts:
I'm trying to change my current battery charger power supply to the higher current capacity power supply but I cannot see much variations in the o/p of battery current.

I'm using two battery charger power supplies (initially used):

1. Charger 1: with i/p= AC 100-240V, 50/60HZ 0.18 A
                   o/p= DC 5.0V, 1.0A
2. Charger 2: with i/p= AC 100-240V, 50/60HZ 0.5 A
                   o/p= DC 5.0V, 2.0A

Battery specs: 3.7v 6400mAh 23.68 Wh lithium polymer battery pack

When charger 1 is connected to my battery, the charging current (measured by a connecting ammeter in series to the USB cable) is 1.12A and the current used by the battery is 109mA (measured by a connecting ammeter in series to the positive side of the battery)
When charger 2 is connected to my battery, the charging current (measured by a connecting ammeter in series to the USB cable) is 1.332A and the current used by the battery is 110mA (measured by a connecting ammeter in series to the positive side of the battery)

How can I increase the o/p current of my battery by using charger 2?


texts:
I am completely new to electronics, and am trying to learn by building an electronic drum set. I've found lots of examples online of circuits to condition the output from a piezo to be read by a controller (a Netduino in my case). The circuit I'm using looks something like this.

A Piezo (connected from the drum to my breadboard w/ some cat5 cable)
A 470k resistor in parallel
A Schottky diode in series (on the + line)
A Zener diode in series (3.3v on the + line)
A 1M resistor in parallel
A 0.1uF capacitor in parallel
A Netduino analog pin (and the ground line connected to the Netduino ground pin)

I currently have 6 of these circuits attaching to the 6 analog pins on my Netduino. The circuit is doing a great job of both not missing any hits on the drums as well as giving a pretty good dynamic range of velocity/volume readings. The problem is that when I strike any of the drums very hard, I'm getting some nasty crosstalk (i.e. I hit one drum, but multiple drums are signalled). I've been stuck on this for a few weeks now and have tried tweaking the circuit in every way I can think of, but can't seem to fix the issue. The closest I can come is to put a voltage divider at the end of the circuit. This does remove the crosstalk, but at the cost of significantly less dynamic range (i.e. no matter how hard I hit the drum, I don't get more then around half of the max ADC readout value). I've checked and double checked that everything is connected to the same ground. The Schottky should be keeping any negative signal from getting to the Netduino, and the Zener should be making sure I'm not getting anything above the 3.3v that the Netduino wants.

I think an oscilloscope would probably help a ton in figuring out what's going wrong, but as this is my first electronics project/experiment it's a little hard to justify a couple hundred dollar purchase to the wife ;)

Can anyone point me in the right direction for figuring out what's going wrong?

EDIT:

Here is my attempt at a schematic. I've just downloaded Eagle and am not entirely sure how to use it, but hopefully this is close enough to give the idea. The piezo symbol on the left doesn't look right to me, but that's what Eagle gave me.

EDIT #2:

Per several requests below, here are some pictures of my circuit (slightly updated from several peoples suggestions). Also, I've included some pictures of the drums. The drums use a special "screen" drum head that makes very little audible sound. There is a small piece of foam that transfers the drum head vibrations to the piezo.


texts: Why is P9_14 GPIO input using Adafruit's library giving me -1227689624 on my BeagleBone Black?

texts:
I know I should really be writing my own GPIO libraries so I know how they work and can fix them when they break, but for now I am following a simple tutorial using Adafruit's GPIO library, which I have successfully installed.

Note that in the command line output below I am using P9_14 instead of P9_12 (shown in Adafruit's photo below), but both gave the same result when I tried them.  I have tried rebooting the Beaglebone, same result.  Connecting GND to P9_14 gave no change.  Connecting GND to P8_14 gave no change (thinking maybe Adafruit mixed up their connector labels).  Connecting 3.3V to P9_14, or 3.3V to P8_14 gave no change.

Any ideas?

Also note below that the Adafruit Tutorial is listing the wrong pin to use, it should be P9 not P8, according to the photo in their own tutorial.


texts:
What is Offset null in 1st and 5th pin in IC 741 (Op-Amp)? Why it is used, though it is not used in many circuits? Give me explanation regarding the offset null!
Why offset voltage was formed in IC 741?


texts:
I was browsing through the example code that MikroE provides for PIC programming using MikroC, and they always set PORTx before setting TRISx. What is the reason for this?

Since TRIS just selects whether the port or pin is output/input mode, why does it matter what the pin is set to before we set the mode?

Example code

  PORTA = 255;
  TRISA = 255;                        // configure PORTA pins as input
  PORTB = 0;                          // set PORTB to 0
  TRISB = 0;                          // designate PORTB pins as output
  PORTC = 0;                          // set PORTC to 0
  TRISC = 0;                          // designate PORTC pins as output


texts: View the LED driver signal on the ground and op-amp output

texts:
I create a simple LED driver and op-amp circuit. I used a mid-IR LED with a 200 mV voltage and 1A current. A 2 kHz signal is input to the LED driver and Surprisingly, this signal is observed on the ground and at the output of the op-amp, causing a distortion in the photodiode signal.

Is this problem due to the high current of the LED?
How to remove the LED signal on the ground?

simulate this circuit – Schematic created using CircuitLab


texts: Timing violations in interfacing Flash with MSP430 using SPI interface

texts:
I was going through a schematic where MSP430 is interfaced with SPI flash, w25q128fv

During Data transfer between Microcontroller and Flash:
Flash timing specification states that its Data in hold time as 3ns(Minimum) , and microcontroller output data hold time is -8ns(minimum) , which means master changes its state before 8ns before the clock change. Whether this is hold time violation?

During Data transfer between Flash and Microcontroller:
Flash timing specifications states that its data out valid time is maximum 7ns , but the data in set up time of microcontroller is minimum 25 ns. Whether this condition is set up time violation?
In both above conditions whether faithful data transfer would take place between microcontroller and flash. If it’s a violation whether it can be taken care in Firmware coding?


texts:
Ok, here's my problem:

I need to create a needle that can rotate continously in both directions and an infinite amount of "loops". I guess the ideal is to use a servomotor, isn't it? I couls use steppers but I want to keep the price as low as possible.

The problem is tht the most important thing is the precission of where the needle is pointing. I have found already several links that explain how to modify servos so they can run continously, but I lose that precision I'm looking for. I am asking whether there exists a way to achieve this. The only thing I can think of is using some kind of sensor that tells me where the needle is pointing so I can stop the motor when I want it to. Inexpensive sensor if possible...

Does anybody know a solution for my problem? As my last choice, I would use a cheap stepper of about 7.5 degrees of min. rotation and a gear to get a better resolution, although even those cheap steppers are about 8$ while I can get cheap servos for a third of that.


texts: Connecting LORA SX1278 1W to Arduino UNO (LORA 5V Supply voltage but 3.3V communication voltage)

texts:
I bought this LORA modules: https://aliexpress.com/item/32791508935.html
in the datasheet it says that the module needs a power supply voltage of 5V but the communication level is 3.3V.
I've searched the web on bidirectional level shifters like this one: https://www.aliexpress.com/item/32713594384.html?spm=a2g0s.9042311.0.0.4a174c4dCJFkbm but in the connection examples the power supply voltage in the lower part is also 3.3V like this example: https://cdn.sparkfun.com/assets/learn_tutorials/1/4/7/LogicLevelFixed.png
And I can't find any information on how I can connect the LORA Module to the arduino throw a bidirectional level shifter.
Thanks for your time and help.


texts: how choose transistor for driver circuit of stepper motor?

texts: I need to drive a 1A stepper motor coil from a digital output that can source only 5mA.  That would require Hfe of 1A / 5mA = 200, but I can't find a transistor with that much gain.  Is there any transistor that would fit, or is there something else I can do?


texts:
I am trying to analyse the basic circuit of a dimmer. I don't have much experience in AC circuits, so I am not sure how do I need to proceed. My circuit is the next:

I have something like this:

I have found some interesting relationships. Like the output vrms based on the firing angle θ:

Using:

$$ V_{rms} = \sqrt{ \frac{1}{T} \int_0^T v^2(t) dt } $$ we obtain:

$$ V_{rms} = \sqrt{ \frac{1}{ \pi } [ \int_0^{ \theta } 0 d(\omega t) + \int_{\theta}^{ \pi} Sin^2(\omega t) d(\omega t) ] } = \sqrt{ \frac{ V_{max}^2 }{ \pi} \int_{\theta}^{ \pi} \frac{1}{2} [1-Cos(2 \omega t) d(\omega t)]} = \sqrt{ \frac{V_{max}^2}{2 \pi} (\omega t-\frac{Sin(2 \omega t)}{2} ) \Big|_{\theta}^{\pi}}  = \sqrt{ \frac{V_{max}^2}{2 \pi}  [ \pi-\frac{1}{2}Sin(2 \pi) - ( \theta - \frac{1}{2}Sin(2 \theta) ) ]} = \sqrt{ \frac{V_{max}^2}{2 \pi} ( \pi \theta + \frac{Sin(2 \theta)}{2} ) } = V_{max} \sqrt{ \frac{1}{2} - \frac{\theta}{2 \pi} + \frac{Sin(2 \theta)}{4 \pi}  } $$

But I don't know how to obtain the phase angle based on the values of the resistance, the capacitance and the load


texts: How long (in hours) will a 6 Amps LED light last if powered only by 12V 18Ah Lead Acid Battery only

texts:
I have assembled a 300 units of 3650 LED lights which draws a total power of roughly 6 Amps (130Watts) and I want to power it using a 12V 18Ah Lead Acid Battery.

My question is, how long or how many hours the assembled light will last before the battery gets fully discharged?

Is there a certain formula that I can use to get the total hours consumed?

Many thanks in advance for your help.


texts: Dual Power Supply Build with Buck Converter

texts:
Im looking to construct a dual power supply capable of supply about +/-25V and hopefully up to ~5A. I already have a SMPS capable of 30V but it has only one output terminal.

I have opted for a LM317/LM337 regulator design to keep the adjustability. Unfortunately this limits me to 1A (1.5A MAX) due to the limitations of the LM chips. After searching previous threads I think a buck converter is the way to go here but have never used one before so I have some questions about their use:

Will i run into any issues connecting the output of the regulator circuit directly to the buck? The only one I can think of is that being a step down, the LM regulator circuit will just need to be set to a higher voltage than the desired final output.
Ive found only one other reference to this question and without a real clear answer; to boost the current for the negative half of the regulator output, can this be connected to a seperate buck by just reversing the polarities? i.e would the top level circuit look something like this:
On a less important note, im looking at grabbing these from ebay as its likely only a one time build and i prefer the finished look of PCB. I have found these two seperate listings for the regulators with the only difference I can note being the OP AMP and a few extra resistors in the second link. any ideas as to what this is for? is this likely to act as some sort of feedback? a buffer?
Regulator 1, Regulator 2

Also if there is a less complicated way of achieving this for around the $50 range Im open to suggestions.

Thank you for any and all help


texts: Is it possible to get Flux in a magnetic circuit with zero mmf?

texts: From an Example that I stumbled upon on A.E. Fitzgerald's book on electric Machines. He assumed that there is flux in a circuit with zero mmf. Which I find very confusing. I would appreciate it if anyone can put some insight of how it came about.


texts: Why is this resistor only connected on one side?

texts: I have taken a photo against the light so you can see through the board. It seems the circled resistor is only connected on one side. My hypothesis is that there is more than one version of this circuit board and another version has a capacitor or something in the empty space below the resistor. But for ease of manufacturing all boards have the resistor. Is this correct or am I missing something?


texts:
This is kind of a hobby project (I'm an informatics professional but I always was fascinated by electronics). I want to build a baby call (basically, a one way intercom); to simplify the electronics (soldering, etc), I was wondering if I could use my home wireless network (I have a very good signal covering all my home) to connect the transmitter with the receiver. Of course, I want the transmitter and the receiver to be embedded.
I would like to know what kind of micro controller do you recommend me, and what other electronic tips could you give me: for example, how can I attach the microphone/speaker to the micro controller.

Thanks in advance,

Federico


texts: nrf24l01+ returning incorrect payload value

texts:
I have 10 nrf24l01 modules, 5 from the german web shop, 5 from the local finnish offline store.  I'm using them in pair, one module sends exactly one byte to another one module with period of ~100ms.
I have ack enabled on both sides, CRC enabled on both sides and tried to enable/disable dynamic payload. I also did tried changing channels.

So, on the sender side everything works perfect - TX_DS is set on successful transmission and MAX_RT is set, when receiver is off or not listening.

On the receiver side everything also looks perfect - IRQ line goes low on receive event, RX_DR is set on receive, status register contains correct number of a pipeline with data (pipe 1), RX_EMPTY in fifo_status is (0).  With dynamic payload size R_RX_PL_WID returns correct size of payload (1 byte). When i issue R_RX_PAYLOAD command, RX_EMPTY in fifo_status goes to one and status register goes to 0b0xxx111x, thus i'm quite sure, that i'm sending proper read command.

The problem is that R_RX_PAYLOAD always returns same value 0x46, which is not the value i send, obviously. Even more, if i will try to read  without actually receiving the data, it still will be 0x46. If i try to read more data, then in buffer - still 0x46.   I did checks with logic analyzer - on wire payload is correct on the transmitter side and on wire payload is incorrect on the receiver side, so it is not an issue with  firmware writing/reading to a wrong location.

I would suspect broken chip, but it tried 6 chips out of 10, 3 by one supplier and another 3 came from another supplier. I doubt that i can have 6 chips from different batches with exactly same problem. What i can be missing and why it returns same weird value as payload?

PS STM32F1, libopencm3, homebrew nrf code


texts: Switching power sources with a FET while avoiding brownouts

texts: I've got a power bank powering a SBC with 5V, and I want to be able to power this SBC with 5V to not waste batteries. The SBC in question consumes around 500mA, with peaks up to 1A - so diodes are out of question. How do I make 5V source switching circuit which would prefer the external input (thus detaching the power bank's input), would be capable of switching the said load and not cause brownouts in the process (that excludes relay-based circuits)? I am familiar with MOSFETs but I don't yet understand the thing well enough to make sure it'll work correctly with body diodes. Also, would it be possible to base the circuit around really basic components? It's not that simple for me to buy specialised ICs, but I do have access to simple MOSFETs and such.


texts: Why collector current is small in value in saturation mode?

texts:
Why is the collector current smaller in value when a transistor is in saturation mode of operation? My guess is that although both the junctions are forward biased, the (forward) currents are 'opposing' each other and hence the net current is a small value. Is this explanation true? And if not, why is it so?

(The comparison of current in saturation mode is being made with the current in active mode for an NPN transistor in CE configuration)


texts: Linear Transformer and Ideal Transformer: electric circuit question

texts: The question is to determine k in so that no current flows in Zx. I literally have no clue how to start. If there is no current in \$Z_x\$ that would make it an open circuit, so for it to be possible the votlage across the 400-turn inductor must be equal to the mutual inductance. Is that right? How should I tackle this problem


texts: Possible to connect MPPT via the load distribution bus?

texts:
Is it possible to connect my solar charge controller (MPPT) to my load distribution bus? This would mean that the cables from the bus to the battery would transfer both the load current and the charge current. Anything to consider if possible?

It is a 12 volt system with appropiately sized cables.  I am trying to avoid a double cable run for two meters.


texts:
A parity bit lets a receiver know whether or not the an input is correct, given the number of 1's matches the logic behind the parity bit (be it even = 1, or odd =1). This seems very ineffective to me, and even 'corrupting' (not sure what the right word would be).

What if the message is not corrupted, but the parity is corrupted, does this means the message has to be resent? Or does the parity check have a way around this? And what if 2 bits flip, so the number of 1's doesn't change, so there is no parity error, but now the message has changed.

Am I understanding parity checking incorrectly, am I missing something more with the parity, or is it really that ineffective of an error checker? The reason this is throwing me off is because if it really is this ineffective, why is it taught so much (at least in my program at my university), and these issues are practically ignored.


texts: does 8085 CPU have an extra register within ALU?

texts:
From the 8085 CPU architecture, when ALU done calculation, the result is clocked back to accumulator A on next clock edge. But accumulator A is directly wired as ALU input, what if the clock edge didn't raise fast enough to cause A is being added twice or many more times, it would be extreme difficult to detect such an error, such a design is very "fragile" to me.

Unless, there is an extra register within ALU to temporary save ALU results?

https://en.wikipedia.org/wiki/Intel_8085#/media/File:Intel_8085_arch.svg

https://en.wikipedia.org/wiki/Intel_8085


texts: What is the use of PWM over brushless control

texts:
I just saw this question How do I eliminate PWM noise when driving a fan? but cannot think of the reason why is doing PWM over brush-less control useful.

I am assuming people are trying to control the torque or speed of the motor by PWM. But ultimately the torque, the speed and the mechanic resistance will reach a balance. So controlling one of these three factors should achieve the original goal. For a brush-less motor, it's much easier to control the speed because the controller is doing that anyway - it determines when to energize a coil based on the current rotor position. If the controller delays energizing the coil, the torque will be reduced.

From the answers to the original question, it seems this (doing PWM over brushless control) is rather common. However to me it's more like a dirty hack when there is no access to the controller.

Am I missing anything?


texts:
let me know what I state below is correct or not.
Regarding the DNL and INL of a DAC, DNL is the error difference between actual step width and ideal value (1 LSB). INL is the deviation of actual transfer function from the shown straight line (Shown in image below).
My understanding is, that to guarantee no missing codes and a monotonic transfer function, the DNL must be less than 1 LSB.
Regarding my DAC ICs, the DAC IC #1 I found has a INL of +/- 0.4 and DNL of +/- 0.1. Now, the previous DAC IC #2 had a DNL value of +/- 1 and INL value of +/- 4. All the other specs regarding these two different DACs are the same.
Do you think this is a very crucial thing to consider in choosing a DAC IC and did I make the right decision by looking and choosing DAC IC #1 over the previous DAC IC #2?
Notes
Essentially, this DAC takes in a SDA and SCL I2C signal. It also takes in a 7-bit address selection.
The output signal is DC.

Data Interface: 400 KHz I2C interface.
27 selectable addresses
Number of Bits: 14
Number of D/A Converters: 1
Settling TIme: 9 uS
Output Type: Voltage - Buffered
No Differential Output
Voltage - Supply, Analog - 2.7 V ~ 5.5 V
Voltage - Supply, Digital - 2.7V ~ 5.5 V


texts: Mechanical time constant of PMDC Motor in starting and after switching off the supply is same or different?

texts:
In my MATLAB/SIMULINK model of the PMDC motor the mechanical time constant has same value in the case  starting of motor and after switching off the supply but in experimental setup there is a difference?
I have taken many experimental readings, in which starting mechanical time constant is around 0.05 seconds and after switching off the mechanical time constants is around 0.254 seconds.
 .

If any one have any idea, please reply me.


texts: Understanding how bypass caps work, mathematically

texts:
Assume there is a band of noises that you you want to filter with center frequency Fn.  Then The complex voltage representing noise at frequency F is V_(F, T) = V(F) e^(i W(F) T), where V(F) is the peak value of the sinusoidal voltage and W(F) is the angular frequency = 2 pi F, and T is time.  I went ahead and LaTeXified this to be more readable:

If this voltage were applied to a bypass capacitor C, then

is the current through C that associated with the noise voltage at that frequency.  This is valid for complex voltage and current since we already know that i = C dv/dt in real quantities, but

After some math we see that there's a corresponding complex equation for every real equation involving linear combinations of derivatives of voltage and current.  I'm not so much interested in making this rigorous as figuring out now how to calculate the best value for C if it even matters.

Let me know if I can clarify anything.