texts:
Back in Sep '12, Olin Lathrop answered a similar question about wiring a digital display to a thermistor, but my situation is slightly different from Jim McDerby's.  I too have solar thermal panels mounted in different places, and have had to replace two of the three delta-T controllers with units from Germany (How is it that we don't make this stuff here anymore?). I had the Aux, on one old controller with a digital display, set up to read thru a rotary switch, a bunch of thermistors scattered around in various places.  The new controllers use more sophisticated sensors, so now I'm left with a bunch thermistors, some embedded in concrete, with no way to read them.

The difference is that unlike Jim, I don't have to worry about Olin's point about "load these signals else it will confuse your existing solar thermal system".  I was going to ask Olin a follow up question, but your website rules forbid that, so I'm here and my question is:

What's the simplest way to read the thermistors?


texts: How to Power a Tank Circuit with Mosfet without the Inductor Undesireably Triggering the Mosfet

texts:
BACKGROUND: I have this circuit that I asked about in a previous question:

Someone kindly explained that the problem I'm having with the circuit is that the mosfet is being triggered by negative voltage in the tank circuit causing the mosfet to stay on longer than I want it to.  It's being caused by the initial field collapse of the inductor before the first oscillation begins.  The result is the appearance of a delay between the end of the gate pulse and the start of the first oscillation.  The result is the following messed up scope shot (green signal is mosfet gate, and yellow signal is mosfet source voltage):

MY NEW QUESTION:  Can some folks give me direction on a better way to power the tank circuit without causing this behavior?  I guessed that using a BJT would probably fix the problem, but I was wondering if there's a way to stick with mosfet.  I'm finding that I'm running into the same problem in other configurations with inductors and mosfets.


texts: Supplying power to GSM Modem and MCU from 18650 li-ion battery

texts:
Currently I'm trying to design a circuit with a SIM7600 gsm/gps modem with an STM32 MCU. I'm stuck with the most important part: the power supply. I want to use 18650 Li-ion battery. The modem needs 3.8V and it's peak current can reach 2A (one of the major problems are the peaks, from few mA to 2A). The MCU won't need more than 500mA. The other major problem is that the 18650 can go from 2.7 - 4.2v and it exceeds the working ranges.
From the beginning, I found the ideal solution, the TPS63806 but it comes in DSBGA and needs a 4 layer PCB. It's hard to solder it and I'm also using only 2 layer PCB in my design. Unfortunately, I can't find an alternative chip.
I came down with 2 alternative solutions:

Use a battery charger from Texas Instrument (BQ2407x not sure about this one, but seems ok) and then 2 step down converters, one for the modem and the other one for the MCU. In this case I will waste energy by stepping up and down.

Use 2 cell battery and then 2 step down converters. The major problem is that I need a 2 cell battery charger, and the design is more complicated.

Note: I'm planning to charge the device with a USB power supply.
Can somebody advice me which design is better and some chips that I could use?


texts: How do I determine expected harmonic frequencies and corresponding amplitudes in a case of synchronous machine?

texts:
1)find harmonic frequencies which source in synchronous machine in a) fault, and b) fault-free operation conditions, in steady state mode.
2) and find how harmonics are depended on power factor, load etc.

There seem to be some literature with equations for finding harmonic frequencies sourced in synchronous machine, however I’m not able to find anything about expected amplitudes.

EDIT: It's for wound rotor synch machine, particularity 20MW Siemens mill drive


texts: iPhone 10W charger, 7Watt Hour battery - takes hours to charge?

texts:
I'm sure this is a stupid question but I can't find the answer.

iPhones have roughly a 6-7 Watt Hour battery according to multiple sources online.

They can also use a 5W or 10W charger (1Amp x 5V - or 2A x 5V) for charging - which I have observed that they reliably draw for the first few hours of charging (then of course, slow down over about 80% charge).

Even a 10W charger takes 3 or 4 hours to get to 80% from no charge. Doesn't that mean it should have a 30 or 40Watt Hour battery? What am I missing?

thx.


texts: Analog Sensor output signal accuracy and sensitivity

texts:
I have to decide between 2 load cell models. the only difference between the two is  that the output on one is 2mV/V and the other is 3mV/V. Both are rated at 2.5klbs.
Which one of them would be more accurate with less fluctuations?


texts: Half-wave rectifier with diode connected nMOS and pMOS

texts:
I am reading about half-wave rectifier and there are two questions below. Hope anyone could help me out.

Q1: the text said that the diode-connected PMOS body is tied to source. However, in the figure, body is tied to the drain.

Is this a mistake?

Q2: Why connect the PMOS transistor in parallel with NMOS transistor improve the circuit performance?


texts: How do these capacitors in this BJT Darkness Detection circuit work?

texts: This circuit detects darkness and produces a beep alarm. I simulated the circuit in LTspice and verified it works, but I still don't understand how the capacitor (4.7uf & 100nf) function in the feedback. Kindly help me understand how they are working.


texts: Reset the configuration of FPGA without reprogramming

texts:
I am doing an experiment on Xilinx VC709 board. The experiment involves removing and plugging in the DDR3 RAM while the FPGA is running. But every time I plug back the RAM I have to reprogram the FPGA. I am using JTAG to program the FPGA, which  takes time to program. I tried reseting only the Microblaze which still couldn't detect the RAM when plugged back while it's running. Is there any other way that I can reset the configuration without having to reprogram?

Thanks


texts: Collector must be more positive than the emitter

texts:
My book (The Art of Electronics by Paul Horowitz and Winfield Hill) is stating something that seems to be the opposite of the example it is using. I am not going to school for my studies so I apologize for having no go-to resources but here. Can anyone shed light on where I'm getting confused?

I'll type out the relevant bits:
"A transistor is a 3-terminal device available in 2 flavors (npn and pnp),  with the properties that meet the following rules for npn transistors:
1. The collector must be more positive than the emitter.
2. ....
3. ....
4. When rules 1-3 are obeyed, IsubC is roughly proportional to IsubB and can be written as
IsubC = (hFE)(IsubB)
where hFE, the current gain (also called beta), is typically about 100.
...
When the switch is closed, the base rises to 0.6 volt (base-emitter diode is in forward conduction). The drop across the base resistor is 9.4 volts, so the base current is 9.4mA. Blind application of rule 4 gives IsubC - 940mA (for a typical beta of 100). This is wrong. Why? Because rule 4 holds only if rule 1 is obeyed; at a collector current of 100mA the lamp has 10 volts across it. To get a higher current you would have to pull the collector below ground."

My question is isn't the collector more positive than the emitter in this case? The collector has 10 volts and 100mA. The emitter is literally connected to ground. The collector is therefore more positive than the emitter. Is it not?


texts: What metal(s) are old game console RF shields made of and coated with?

texts:
I'm restoring my old game consoles (like NES) and am having trouble finding what the RF shields are made out of and coated with so I can sand out the corrosion and re-plate them.
I thought it might be steel sheet metal plated with Zinc and chromate because of the dark corrosion on top and light rust spots over the output section, but have been unable to verify that. Someone suggested that it might be coated in tin, but was unsure.


texts: Modifying an irregular length bit field in a register in C/C++

texts:
Suppose I wanted to modify the field ADD[7:0] in the following register:

I wrote this to make things more convenient.
  {
    const uint8_t Character = USART_TERMINATION_CHAR; //8-bit ASCII termination character

    //masks to modify register
    uint32_t Zero_Mask = ~Character;
    uint32_t One_Mask = Character;

    //shift so mask will apply to appropriate location in "CR2" register
    Zero_Mask = Zero_Mask << 24;
    One_Mask = One_Mask << 24;

    MODIFY_REG(USART1->CR2, Zero_Mask, One_Mask); //USART_CR_ADD[7:0], address or character match symbol
  }

But if the field, in question, was an irregular number of bits, for example DIVR[6:0]:

How would I actually do this? Because in the code snippet above I was relying on the uint8_t type being the same length as the field. But there exists no 7-bit data type and if I use something like uint8_t the mask is going to be modifying bits outside of the field due to the presence of extraneous bits.


texts: Impedance matching with transformer and resistor

texts:
I want to drive a 8Ohm load with a tube amp(Push-pull 2xEL84) that needs a ~8kOhm impedance on its outputs.

I have a transformer that has a impedance turns ratio of 0,048. link

So if I just plug in my 8Ohm speaker to the output side, I will get 8 / 0,048^2 ~= 3,5kOhm. This might damage my amp so I am looking for a solution.

My idea until a proper transformer arrives, is to series connect a 10 Ohms resistor to the speaker like this:

simulate this circuit – Schematic created using CircuitLab

So now the impedance on the tube side will be 18 / 0,048^2 = 7,8kOhm.

Is my understanding of impedance matching transformers correct?

Apart from burning more than half of my output power into the resistor, does this have any negative effects?

EDIT:

The transformer has many taps on its primary for things like ultralinear output, but I use it as a simple center-tapped transformer. Also the other side seems to have 4 windings, but if you look closely, they are all connected.

DC resistance of primary: 18,2Ohm.
Secondary: <0,1Ohm - Couldn't measure.

I assume this low DC resistance will have negligible effect on impedance, so my previous assumptions are correct.


texts: I'm looking for reputable vendors to purchase phase stable cables for VNA measurements of body area networks. I found Huber + Suhner and Pasternack Enterprizes, but can't find anyone else reputable. Do you know of other reputable vendors that sell high quality RF products? Thanks in advance for the answer.


texts: Ground offset or common mode noise voltage

texts:
This is just a small doubt I would like to clear.

Suppose I have a buck regulator providing output at 5V and 1A.

Suppose I measure the output voltage at the ground pad of the output capacitor and it measures like 0.2V.

Is this 0.2V common mode noise or is it ground bounce or what is the 0.2V? The neutral (return path) is not at 0V potential but at 0.2V. So, can I call this as common mode noise voltage or ground offset/ground bounce?


texts: What does the e3 or e4 printed on an IC mean?

texts: So after staring at a few ICs today, I was wondering what the "e3" or "e4" stands for on the top of an IC. For example, here is an e3:


texts: How do I track the strength of a magnetic field to 1:20,000?

texts:
I need to track the change in field strength of a (nominally) 1 Tesla Samarium-Cobalt magnet as a function of temperature. It is specified to be less than 50ppm/degC.

Is there any simple technology available that will do this? I was thinking along the lines of magnetoresistive materials, but any tech suggestions welcome.


texts: Importance of Body Transconductance MOSFET

texts:
I am currently studying about small signal models of Common Drain & Common Gate configuration, where the body transconductance has significant effect on voltage gain and output resistance (when body effect is significant).
I also know the principle of body effect - body effect occurs when Vbs < 0; for NMOS device.

Common-Gate T-model

Common-Drain model

I am curious about how a designer of electronic circuits deals with the body transconductance values, since its value isn't given by data sheets. I doubt its can be neglected when performing hand calculations.
Can body effect occurs, although it is connected to most negative potential of NMOSFET? (Perhaps oscillations can make Vbs ≠ 0)
Can someone gives me an example or two, where body transconductance (it can be also referred as "body current generator" or "back gate") has a significant affect on a circuit as a whole?


texts: Ceramic capacitors: how to read 3-digit plus 1-letter markings?

texts:
It seems that reading a ceramic capacitor value out of its written values is harder than decoding enigma machine.

I wonder if experienced users here does have a trick to quickly figure out these values. Some examples:

I know that 103M is 0.01µF but how does one figure this out?
Another example 104Z/LK ...this one I cant get it at all. All I know is that Z is for assymetric capacitors with tolerence between 80% and -20% ... Am I right? If not would be nice to correct me and tell me where these Z ceramic capacitors are used mostly?


texts:
How much watt I need for LED bulb to get the same amount of light produced by 32 Watt CFL bulb?
So, comparing lumen is the right way to find out the difference between these two light source?


texts: Hummm Sound from stereo speaker when used on inverter

texts:
I have a normal 2.1 Stereo speakers with an aux 3.5 cable coming out as input source, i plug this aux cable to a source when needed else it remains hanging, whole speaker this is plugged in to an inverter output for power,

now when there is mains power everything is fine but when power fails and system comes on inverter power suddenly a noticeable Hummm sound comes out of speaker, loudness of hummm sound depends on the volume knob of the speaker, aux cable when touched the sound drastically increases, when mains power comes back again things come back to normal.

Note : On inverter power when speaker is creating hmm noise if i plug aux cable into a phone, computer or headphone with female 3.5mm input then the HMMM sound is completely nil and things work fine.

What may be the reason behind this sound ?


texts:
Can there be 3 select bits in a 4to1 MUX?

I needed it for a particular application and have no alternative.


texts: Suppose i'm charging the capacitor of an integrator until it reaches 5V, again after reaching 5V, Suppose I've designed a circuit so that, it starts discharging the capacitor of an integrator circuit until same negative polarity voltage. Will the time of charging and discharging remain same or different? Why? I have this question tickling on my mind while grasping concept on Dual Ramp ADC.


texts:
The datasheet says the PGOOD signal is open drain but I want to use a 3.3V microcontroller to read PGOOD

with the internal pulldown resistor, when PGOOD is asserted - will the voltage at the pin be 12V (my input voltage to the TPS56221)?
The example design in the datasheet has PGD tied to BP through a 100k resistor - why do they do this?
For my case using the 3.3V logic level microcontroller should I untie PGOOD from BP and use a voltage divider to get 3.3V ?

Thanks in advance!


texts:
I would rephrase my question:

What I'm trying to do is to measure the battery voltage. Based on STC3100 datasheet, the battery voltage value is located on address 0x08 and 0x09 where the value 0x00E6 was read from.

The actual value of the voltage based on the datasheet is voltage(mV)=Voltage_code * 2.44

With this equation, i presumed that voltage(mV) = 230 * 2.44 which results to 561.2mV which is very low compared to the actual reading from the multi-tester.

So my question is how should I calculate the value that was read from the STC3100 (location 0x08 and 0x09) ic so that I can get the voltage?

Here's the schematic diagram of what I'm doing:

I hope I made my question a little bit clearer now. :)

I have a question regarding the voltage calculation.

How should I calculate the voltage that was pulled from the STC3100? I pulled the following value:

REG_VOLTAGE_LOW = 0XE6

REG_VOLTAGE_HIGH = 0X00

When I tried to calculate it using the formula: voltage(mV) = Voltage_code * 2.44, I get a result of 561.2 which is very low compared to the actual reading from the multi-tester.

I know I missed something with the calculation and I hope you can guide me to the right direction.

Thanks!


texts:
I have a latch but I can't understand what are the meaning of Un/Stable state and "don't care".

I found a reference about the definition of the state, but I didn't understand that fluently.

I try to understand these questions:
Statemanet A: while Q2=1, Q1=0 we get stable state.
but why?

Statemanet B: while A=1, B=0 we get "don't care" situation.
but why?

And then I understand that i don't really understand what exactly the meaning.

I made a truth table:

But still, im not sure I understand the conclusion


texts: How is this simple counter implemented on an FPGA without a clock?

texts:
As part of an assignment, I must create these blocks that tie in to a larger top level module.   (there are more blocks not pictured).  I have everything working fine, except this UP/DOWN counter because I can't really work out how this can possibly be implemented without a CLK.

The EN_UP and EN_DOWN signals are simple pulses that should increment or decrement an internal 16-bit value, which gets split into nibbles and put on the output.  I feel as if this should be fairly simple, but I can't work this out.

I've tried multiple approaches.

1) - Inside a single process

count : PROCESS (RESET, EN_UP, EN_DOWN)
BEGIN
    if(RESET = '1') then
        countSignal <= x"0000";
    elsif(rising_edge(EN_UP) and EN_DOWN = '0') then
        countSignal <= countSignal + 1;
    elsif(rising_edge(EN_DOWN) and EN_UP = '0') then
        countSignal <= countSignal - 1;
    end if;
END PROCESS;

This ultimately compiles with no errors or warnings, however the compiler ends up creating the wrong circuit, tying the EN_UP to the CLK of the flip-flip, and the EN_DOWN to the CE (clock enable).  While yes, that is part of the equation, it doesn't mirror that for the opposite case.

2) - Separate processes

countUP : PROCESS (RESET, EN_UP)
BEGIN
    if(RESET = '1') then
        countSignal <= x"0000";
    elsif(rising_edge(EN_UP) and EN_DOWN = '0') then
        countSignal <= countSignal + 1;
    end if;
END PROCESS;

countDOWN : PROCESS (RESET, EN_DOWN)
BEGIN
    if(RESET = '1') then
        countSignal <= x"0000";
    elsif(rising_edge(EN_DOWN) and EN_UP = '0') then
        countSignal <= countSignal - 1;
    end if;
END PROCESS;

This results in: Signal countSignal[15] in unit UD_COUNTER is connected to following multiple drivers:

3) Multiple processes with Hi-Z states

I tried some attempt with Hi-Z which also failed.


texts:
I am trying to interface with an RS485 device (laser) that is full duplex (115.2k).
I am using two SN75176A ics... I can receive data from the laser fine, but I can't transmit any data to the laser.
Looking at one side of the  differential outputs of the SN75176A it looks like the nothing is coming through, the output is just hovering above 1V, but the input side looks ok.
The schematic I am using is attached.  The top SN75176A is RX into the micro and works OK.
Anything wrong with the circuit to transmit data from the micro?

Attached is a scope shot, channel 4 is input, channel 7 is output


texts: Relay back emf cauisng my micro controller reset

texts:
I have a 5V 30A relay in my circuit. I made a PCB with all the connections to microcontroller and relay. At present I am using M7 smd diode as flyback diode. But problem is occuring if I switch on/off the relay fast. I tried some of the IN400 series but nothing takes me out of this problem. I don't know what the exact mistake is. Here is my circuit diagram:

Relay I am using — 5v 30A relay

Optocoupler — EL817.
Please suggest me solution.
Thank you.


texts: Control multiple servos using pic18f microcontroller?

texts:
I want multiple servos to  be controlled through pic18f4550 microcontroller.

I know for a single servo I can use the following code.

unsigned int angle=0,i;
void cs_delay(unsigned int);
void main()
{
   TRISB.F0=0;
   while(1)
   {
      for(angle=0;angle<=180;angle+=45) // Loop to increase the angle by 45°
      {
         for(i=0;i<50;i++) // Loop to provide continuous train of pulse
         {
             LATB.F0=1; // Send high to control signal terninal
             cs_delay(angle); // Call delay function
             LATB.F0=0; // Send low to control signal terninal
             Delay_ms(18);
         }
      }
   }
}

void cs_delay(unsigned int count)
{
   int j=0;
   Delay_us(550); // Delay to move the servo at 0°
   for(j=0;j<count;j++) // Repeat the loop equal to as much as angle
   {
      Delay_us(6); // Delay to displace servo by 1°
   }
}

But I cannot figure out how it can be used for multiple servos..

BTW, using MikroC v8.2 for programming.

Any help?


texts: I am trying to trigger a 12 V relay with an arduino input. All I am doing in the Arduino sketch is to make pin 13 go high and low every 1 sec (1000 ms). The relay refuses to get triggered. Can someone please tell me what am I doing wrong? Struggling with this for way too long.


texts: Separate Vector Table for USB Bootloader (Infineon 4400-CortexM4F)

texts:
I am developing a USB bootloader for Infineon XMC 4400 micro . I have modified linker_Script.ld file and have allocated 32K for flash.

MEMORY
{

BOOT_FL_cached(RX) : ORIGIN = 0x08000000, LENGTH = 0x8000
BOOT_FL_uncached(RX) : ORIGIN = 0x0C000000, LENGTH = 0x8000

FLASH_1_cached(RX) : ORIGIN = 0x08008000, LENGTH = 0x00078000
FLASH_1_uncached(RX) : ORIGIN = 0x0C008000, LENGTH = 0x00078000

PSRAM_1(!RX) : ORIGIN = 0x1FFFC000, LENGTH = 0x4000
DSRAM_1_system(!RX) : ORIGIN = 0x20000000, LENGTH = 0x8000
DSRAM_2_comm(!RX) : ORIGIN = 0x20008000, LENGTH = 0x8000
SRAM_combined(!RX) : ORIGIN = 0x1FFFC000, LENGTH = 0x14000

}

stack_size = DEFINED(stack_size) ? stack_size : 2048;
no_init_size = 64;
SECTIONS
{
    /* TEXT section */

.Boot_text :
{
    sText = .;
    KEEP(*(.Boot_section));
    . = ALIGN(4);
} > BOOT_FL_cached AT > BOOT_FL_uncached

.text :
{
    sText = .;
    KEEP(*(.reset));
    *(.text .text.* .gnu.linkonce.t.*);

    /* C++ Support */
    KEEP(*(.init))
    KEEP(*(.fini))

    /* .ctors */
    *crtbegin.o(.ctors)
    *crtbegin?.o(.ctors)
    *(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
    *(SORT(.ctors.*))
    *(.ctors)

    /* .dtors */
    *crtbegin.o(.dtors)
    *crtbegin?.o(.dtors)
    *(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
    *(SORT(.dtors.*))
    *(.dtors)

    *(.rodata .rodata.*)
    *(.gnu.linkonce.r*)

    *(vtable)

    . = ALIGN(4);
} > FLASH_1_cached AT > FLASH_1_uncached

The problem is when i try to debug the code , and open disassembly , I don't see anything at address 0x08000000(which is the start of the BOOT FLASH). My vector table for application is pointing at 0x08008000 which is where it should be as expected. So DO I NEED TO have a separate VECTORTABLE for BOOTLOADER ? Also I am using a separate function  JumpToApplication(Jump_address) to jump to the application .


texts: 24GHz Radar : IF amplification and strange mixer output

texts:
I am currently working on a project where I have to study a microwave Doppler Radar.
Here are some details so that you can better understand it : a local oscillator (LO) at 24GHz is linked to an emitter antenna. A moving target reflects back the emitted wave with some Doppler effect, which is taken back in a receptor antenna. A double-diode mixer follows, taking the LO signal and the received signal, it is linked to an IF filter/amplifier so as to extract the Rice components of the signal.

I have two questions.
First on the oscillator, shown here :

24GHz corresponds to WR-42 waveguide format, which we can see on the pic. The two upper pins are the diodes (outputs) + a third pin for ground reference. But what kind of input is shown in red ?

Second on the IF filter/amplifier, shown in block diagram here :

The purpose of a bandpass filter is to extract a frequential component at ω (reflected frequency) minus ω0 (LO frequency), while filtering upper components from the diode mixer and lower componants as DC or 50Hz. But there are two things I don't understand here : why two stages of bandpass filter / amplifier ? And why finally a low pass filter ? Aren't all upper frequency already filtered ?


texts: Extract numbers from String on ATMega168

texts:
I try to separate and parse two numbers out of a string, one is a float and one is an int. So I do this...

char packet_buffer[24];
float dist_float;
uint32_t quality;
uint32_t distance;
strncpy(packet_buffer, ": 2.846m,0089", 24);
memmove(packet_buffer, packet_buffer+1, strlen(packet_buffer)); //Remove leading colon
sscanf(packet_buffer, "%fm,%d", &dist_float, &quality);
distance = (uint32_t)(dist_float*1000);

This returns 96 for quality and 0 for distance... but running it with Ideone works. Did I overlook something in combination with the ATMega?

I'd expect 89 for quality and 2846 for distance.

Edit: After adding the build parameters suggested by Filo, the output looks like this

    "C:\Program Files (x86)\Atmel\Studio\7.0\toolchain\avr8\avr8-gnu-toolchain\bin\avr-gcc.exe"  -x c -funsigned-char -funsigned-bitfields -I"C:\Program Files (x86)\Atmel\Studio\7.0\Packs\atmel\ATmega_DFP\1.2.150\include"  -O1 -ffunction-sections -fdata-sections -fpack-struct -fshort-enums -g2 -Wall -mmcu=atmega168p -B "C:\Program Files (x86)\Atmel\Studio\7.0\Packs\atmel\ATmega_DFP\1.2.150\gcc\dev\atmega168p" -c -gdwarf-2 -std=gnu99 -ffreestanding -fdata-sections  -Wl,-u,vfscanf -lscanf_flt -lm -MD -MP -MF "src/main.d" -MT"src/main.d" -MT"src/main.o"   -o "src/main.o" "../src/main.c"
    Finished building: ../src/main.c


texts: Input Impedence of Transmission Line Loop

texts:
I am practising questions from old tests for an upcoming exam on EM fields and waves. I came across this question which has me confused. I'm not sure where to start.

A lossless TL of length l and characteristic impedance of Z_0 has its ends joined together forming a loop as shown below. Find the input impedance Z_in.

Is this an open circuit termination? How is the TEM wave travelling in this circuit. This circuit looks bizarre compared to the typical TL questions that I see.


texts: Design of a 5kW residential Solar system with battery- need help with electrcial diagram

texts:
A design project asks for a design proposal of 5kW solar panel with inverter and battery system for a residential house.

I have completed the energy estimation, panel size, orientation, and selected suitable solar inverter (SMA Sunny Boy 5kW) and battery (Tesla Powerwall 7kWh)

The question asks to provide an electrical wiring diagram of the system-

Single-phase with earth and neutral connection
Switchboard layout of generation and storage
At least one of the loads is more than 5kw

I know how to design the diagram for parts 1 and 2 but could not understand how to approach part 3.

Should I show the connection of all residential loads?


texts: Is associativity number for caches per row?

texts: If a cache memory has associativity 4, then it means than the memory has "4 blocks per set" but how do I visualize it? It "4 blocks per set" the same as "4 blocks per row" so that a cache memory with associativity 4 and 10 sets will have 40 blocks, 4 per row or did I misunderstand?


texts:
I'm getting measurements from an IoT device.

This measurements are in amps (I get one every 2 min or so).

I know the voltage of the device.

From what I've seen online I can calculate the power in kW doing
\$P = I * V / 1000\$

Is there any way from this information for me to calculate the kWh for this device?

I've seen on another platform that to do that with the same data than me, they basically put everything in a graph and calculate the integral on one hour and use that to deduct the power consumption of the device, but it seems wrong instinctively.

I'm not very qualified with this electrical problematic so please keep that in mind.

Example of measurement taken at different times :

11:00 =>  19.56 amp => 4.49 kW
12:00 =>  20.8 amp => 4.78 kW
13:00 =>  21.7 amp => 5 kW
14:00 =>  18.2 amp => 4.18 kW
15:00 =>  13.04 amp => 3 kW

Would that mean that my power consumption is 4.49 + 4.78 + 5 + 4.18 + 3 = 21.45 kWh ?


texts: advantages and disadvantages of using a microcontroller vs dedicated switching controller for a switching power supply?

texts:
Trying to build a constant current power supply for a laser diode here. I don't think I can use an off the shelf one because of the large 10A max current and because the current has to be controlled electronically by PWM.

So, I will design a buck converter. But I don't know if it's better to build one based on a microcontroller or use a dedicated chip like TI's simple switcher?

For software people like me, a microcontroller solution will be more familiar and have the fewest components - one chip to rule them all. I've searched for other people's experience on this and it seems quite feasible according to Olin's response

Can I use a microcontroller to control the output voltage of a switching powersupply?

The main downside to me is that I can't drive a MCU directly from a 24V source, so I will have to add another regulator. But even that might be simpler than using a dedicated switching chip.

I'm also afraid about fault tolerance. A MCU clearly has way more components inside that can fail. If the switcher fails in the on state, that can burn out the laser diode or worse, start a fire. To mitigate that, I was thinking of installing a watch dog timer, combined with a fuse for the laser.

-------------------update-----------------------------

My first LM5117 circuit using nichrome wire for testing; potentiometer for adjusting switching frequency (output voltage has strong dependence on it)


texts: Reducing speed of motor in cheap record player

texts:
I bought a cheap record player, and it is spinning too fast. It is using a 12V 1Ainput with what I believe is a cheap Chinese 12V motor for turning the belt.
There is a pitch control on the turntable, which was a 10k potentiometer. When it's supposed to be spinning at 33 1/3 rpm, I believe it's at 36 rpm. I've swapped the potentiometer for a 100k one and it made a slight difference, but not much.
The record player is the Thomson TT600BT. What is the best way to reduce the speed of the meter closer to the desired speed?


texts: LM3485 current limiter (\$R_{adj}\$) value selection

texts:
I have what I believe is a working buck converter design centered around the LM3485. It's intended to be a Raspberry Pi power supply.

The schematic is at Pi Power schematic, which I copy below.

(note that in the image there are two errors: L1 is 15 µH instead of 33, and the MOSFET is a Si3443CDV in the latest version).

The parts selection came largely from an online TI design tool. I changed some of the values for availability and cost, and the resulting circuit seems to perform well on the bench.

But since I have some time before the first production boards come back, I've been going over and over the design with a fine toothed comb, and the one thing I can't quite work out is the selection of \$R_{adj}\$ - the current limiter comparator resistor.

According to the datasheet, the comparator compares \$V_{isense}\$ with \$V_{adj}\$, and when \$V_{isense}\$ is lower, it triggers the over-current shutdown.

Well, \$V_{isense}\$ is the voltage drop across a sense resistor, which for this design is 25 mΩ. The maximum rated current for the design is 2 amps, and the datasheet says the peak amps is \$(I_{max} + I_{ripple}) \times 1.1\$, and that for currents over 2 amps, \$I_{ripple} \le I_{out} \times 0.3\$.

On the \$R_{adj}\$ side, there is a calibrated 3.0 µA current sink that's connected on the opposite side of \$R_{adj}\$ from \$V_{in}\$.

Put it all together and the current limit should be

$$R_{adj} \times .000003 = I_{max} \times .025$$

or

$$R_{adj} = \frac{I_{max} \times .025}{.000003}$$

For an \$I_{max}\$ of 2.53A ( \$= 2.3 \times 1.1\$), \$R_{adj} = 22k\$ (roughly).

So why did TI's design software recommend 39k?

I have to assume TI is smarter than I am. What did I miss?


texts: Xilinx FPGA Input data timing constraint

texts:
I'm using Xilinx Spartan 6 Automotive FPGA. My FPGA design has a SPI interface to a external peripheral.

From FPGA to the peripheral, I have these SPI related signals:

spi clk
spi data (mosi) - the data is presented on the falling edge
of the spi clk

From the peripheral to FPGA:

spi data (miso) - the data is presented on the rising edge using the spi clk received from FPGA

FPGA samples the MISO SPI data using the SPI CLK falling edge - it's generated internally (via a state machine).

Now, I want to add a timing constraint on the MISO pin to ensure the MISO data reaches the first sync component (a latch clocked by spi clk) without violating the setup and hold time. Which Xilinx timing constraint should I use?

Some options I was looking into are OFFSET IN, FROM/TO...

I perfer OFFSET IN because it relates data to the clock, but I cannot figure how to specify an internal clock (I don't have SPI clk loopback). FROM/TO might work, but it's not relative to the clock.


texts: Why doesn't a capacitor connected to a MOSFET charge to VDD

texts:
If an nmos which has the gate and drain connected to VDD, and the source connected to a grounded capacitor, the nmos will start conducting and the capacitor will start charging as long as VDD > VTn (the threshold voltage of the nmos). The gate is connected to VDD and the source is connected to a grounded capacitor so VGS = VDD - Vx (Voltage across capacitor).

Because the nmos is in conducting mode it will act like a resistor, so a current can flow from  VDD to the the capacitor and charge it. This should keep charging until Vx equals VDD, but apparently it doesn't. In steady state, the capacitors final charge value is VDD-VTn.

Why does this happen?

The threshold voltage (Vtn) concerns the voltage that the gate needs to be at before a conducting channel between the source and drain can form. Why would this cause the capacitor not to charge to VDD when the capacitor isn't connected to the gate?

The picture below shows the circuit which I am talking about.


texts:
i am third year Electrical engineering student, i have some issues that i could not find a good explanation for it. lets say we have an RC circuit (low pass configuration). if we calculate the transfer function we get Vo/vi=1/1+RCS. so we have a single pole in s=-1/RC. my question is what will happened to transfer function we stimulate the system in frequency that is equal to the system pole. i would expect it to blow since the denominator is zero in this case, but if we look at the frequency of this system it never blow. so what am i missing here? is it possible at all to stimulate the system in it pole frequency?
thanks!


texts: How to build large demultiplexers using SystemVerilog?

texts:
Note: This question about demultiplexers is similar to but not identical to this question which is about multiplexers.
I want to build a fully parameterisable demultiplexer in SystemVerilog. So far, I know how to build demultiplexers of variable widths like this:
module scale_mux #(parameter WIDTH = 1) (
  input logic sel_a,
        logic [WIDTH-1:0] in,
  output logic [WIDTH-1:0] out_a, out_b);

  always_comb
    unique case (sel_a)
      1'b1 : out_a = in;
      1'b0 : out_b = in;
    default: out = 1'bx;
    endcase

endmodule

I also know how to extend this for 1:4 and 1:8 demultiplexers. But the number of case statements for large demultiplexers will be a lot.
I'd like to build a demultiplexer in which the number of inputs is variable. I'm not sure how I can extend the case statement for the n input case, do you have any ideas?


texts: Is this input-output relation correct? Schmitt trigger

texts:
OK, operational amplifier will want to keep node A at GND level. It will try to set its output so that the condition (inverting input potential = non-inverting input potential) is satisfied all the time.

So, why isn't a 5V of input mapping to -10 V which will hold node A at 0 V, but rather it is shown that +5V of input will result in +/- 12 V of output?


texts: Insulation of components in a breadboard

texts:
One of the usual problems I have when using a test breadboard is legs of one component touching the legs of another one. Jumper cables are insulated, but the long legs of resistors, capacitors, etc are not.

I'm thinking to protect them using a plastic cover (if I found some tube of the appropriate diameter) or some insulating paint.

Does anyone have experience with this issue and suggestions of possible solutions?

Thanks.


texts: Renesas Compiler: KPIT vs GCC-Renesas (CyberThor)

texts:
When looking around at Renesas (RL78) compilers, I noticed GCC mentioned a decent amount, but the links are different. Many of the older (<= 2015) URLs point to an India company, KPIT, and is mentioned in a Renesas press release. That website currently comes up with an empty web page for me.

Google searches for "renesas gcc" return gcc-renesas.com which is operated by a Romanian company named CyberThor Studios. Renesas's website doesn't mention CyberThor (that I've found).

I guess what I'm asking is...

What is the GCC for Renesas history?
KPIT and CyberThor look to be for-profit companies. Is their paid support any good?
Is it preferable to just use CC-RL from Renesas?
(bonus) Any experience comparing CC-RL to (currently CyberThor's) GCC code? Things like better bit manipulation, smaller code size, or faster execution with CC-RL maybe?

Cheers!


texts: How do I display a certain character on a 16-segment display?

texts:
I'm trying to display my name on 16-segment displays and I know that each pin corresponds with one segment. The problem is it is too much work to derive the pin assignments for each letter since there are so many. Is there an IC that will do that for me if I give it the ascii code for each letter ? I googled that but I couldn't figure it out. google led me here:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/3211
I can't understand what it is about.
Any tips on how I can do this in an easy way and efficiently ?


texts: Opinions on what I've come up with for a 12 V-to-5 V automotive circuit?

texts:
Is this a solid solution for an automotive 12 V-to-5 V circuit to power an ATtiny? I've been trying to come up with a solution for my needs that can handle the automotive environment that is so scary some places won't even talk about it.

From recommendations, scouring datasheets and lots of googling this is what I've come up with so far. It will be placed inside the cabin of a vehicle (not the engine bay) and everything selected is AEC qualified, but I don't know if it will actually work as intended or if I don't have enough protection (the ESD/TVS should kill most of the automotive nightmare right?). The other part of my circuit (not shown) is an ATtiny that will operate some auxiliary lighting.

Please don't say just use a USB 12 V adapter, because I'm not trying to couple multiple boards together hence trying to nail this circuit so I can include it on my device's PCB, but other than that please school me if I have anything incorrect.

**Also note the resistor for the LED is incorrectly rated in the schematic. It's supposed to be 150 ohm like the component list.

Components:

D1: SMA6J5.0CA-TR
IC1: ZLDO1117QK50TC
C1: C1210X106M3RACAUTO 10 µF 25 V
C2: TPSC107K010R0150 100 µF 10 V

-- Optional, for testing (not really important) --

R1: ERJ-U06J151V (150 ohm)
LED1: 150080GS75000


texts:
I have almost no experience with electronics so this might be a stupid question.

I have a "switch" that I want to operate from a computer running Linux, it's actually two cables that I need to connect to each other closing the circuit for about 1 second. They operate at 5V.

I did some research and apparently I can do this with an Arduino, but since it seems like a very simple circuit I was wondering if I can build something with only a few components. I also found the Teensy board but it still seems overkill.

Any advice?


texts: CMOS Fabrication Process - Ion Implantation

texts:
During the process of producing the source and drain of the MOSFET, people use a technique called ion implantation. So my question is why use ion not atom?
Thanks very much!


texts: Thevenin's Theorem for the circuit with controlled voltage source

texts:
We have a circuit like this:

The task is to transform it with the use of Thevenin's Theorem to a circuit like this:

I got the voltage \$U_i\$ by using the node voltage method, but I don't know, how to get the resistance \$R_i\$. I have tried to combine the passives from the first scheme, but it didn't lead to right answer. Voltage of the controlled source is \$u_v = R\cdot i_r\$ if that's important for some reason.


texts:
These are the connectors you can typically find on the back of stereo head units in cars, to connect the FM radio antenna.

I measured the external diameter at ~10mm.

You can easily find a ton of such products by googling "ISO antenna connector". But they all are various kind of adapters sold on alibaba or car accessories shops. I need to find some source for the mating PCB connector, but I don't know what is the "official name" of that type of connector.

There has to be an official name, though, since it seems to be an ISO standardized connector. The number of the ISO standard it adheres to would satisfy me enough.

Here is a picture:


texts: IC that would pull output to the ground, perhaps NOT gate?

texts:
I have a board with four relays on it. It has a standard Vcc, Gnd, and In1-In4 pins. I want to control it with Arduino or in my case an ESP32. However, I noticed that when output pin on my controller is pulled HIGH nothing happens when it's pulled LOW the relay will engage.

This is a problem when the board is reset because of all the relay switches will engage until and this isn't something I want. After some digging, I made this:

This works as desired, there's always 5V on the relay and the relay is disengaged all the time. When I output a signal to the base of the Q1 it will pull the output to the ground and the relay will engage.

Right now I have four of these relays and pretty soon I'll have more. So, I'd like to solve this with an IC. In particular, I was looking at the IC7404 which is a bunch of NOT gates, however, I am not sure this will solve my problem.

So, is there an IC that would pull the output to the ground when the signal is present on the input? Will 7404 work and I'm just not seeing something? :)

Edit: This is the relay module I am using. I wasn't able to find any useful data sheets on it.


texts:
Ok guys, first of all thanks for your support and your help, I can't understand how the drift current work, let's say that we have this junction

By the definition of the drift current we can understand that this current is made from minority carriers, so it is made between the holes in the N region and the free electrons in the P region (The minority carriers) but how can the drift current flow if the free electrons in the P region are pushed away from negative zone of the depletion zone that attract holes, and the holes in N zone are pushed away from the positive zone of the depletion region (That will attract free electrons), so if the minorities carrier are pushed away how can this current flow?Thanks for read have a great day :)


texts:
I'm in a pursuit of finding the fastest PCB relay there is and there is a Chinese manufacturer that produces DPDT PCB relays that are rated 5V, 12V and 24V.
Which of these would have the fastest switching time? Can you conclude that without doing a measurement? (cause, you know, the shipping takes like 3 weeks or so...)
I'd argue that higher voltage rated relays would contain more windings, therefore would take more time to magnetize up to the switching point.

P.S. knowing the "problem-solving mentality" of the SO folk, I do not want to switch to a SS-Relay or transistor, I am building a highly useless thing called a relay CPU :)

Edit1: thank you for all the comments. Usually, cheap chinese manufacturers don't provide useful datasheets at all. And buying more expensive relays can get really expensive quite fast. But still, thank you all for infos :)


texts: Where can I find a TDFN/14 part definition for Eagle?

texts:
I'm new to Eagle (previously only worked with Fritzing) and I'm porting a layout into Eagle that uses the MAX98306 IC (http://www.maximintegrated.com/datasheet/index.mvp/id/7413).

I can't seem to find the right package type for Eagle, but it's possible it can go under another name and I just don't know what I'm really looking for!

Edit/update:
I have found reference to the exact IC I want in SparkFuns Eagle library: https://github.com/sparkfun/SparkFun-Eagle-Libraries. Specifically in the file SparkFun-PowerIC.lbr. I have added the library to Eagle and can see a ton more parts than before, but searches don't bring up that specific item.

Result!:
OK I finally figured it out. Once a new library is added you may need to 'enable' it's part sets by clicking the dot to the right of the part set in the Control Panel window in Eagle. Man this program has some major UI issues. :)


texts: Connect multiple 3.7 V Lithium-ion Polymer Battery in parallel

texts:
If I connect 2 1000mAh battery in parallel would I get 2000mAh over 3.7V?

https://www.aliexpress.com/item/1000mAh-3-7-V-Lithium-ion-Polymer-Battery-102050-For-MP3-MP4-MP5-GPS-KTV-Household/32952678499.html?spm=a2g0s.8937460.0.0.18452e0e5myegg

would it be safe to connect two of the above? i understand that i can buy 2000mAh battery but just want to understand the basic concept.

Should I add any safety mechanism for that?


texts: My printer injects hum into my USB ports

texts:
I have a Brother HL-L2305 laser printer. I love it. I also have a pair of KRK Rokit 6 G3 speakers that I run off of an MBox 3.

Every time I plug the printer into any USB port, hub or not, a loud hum instantly emits from the speakers until I unplug the printer or it goes to sleep.

So my question is is there a schematic for a device I can build to eliminate this noise, something I can maybe plug in between the printer and USB port?


texts: What is "current rating" in a battery implied by?

texts: How battery limits current to the maximum level that is indicated in its specification? If V/R value is greater than maximum current rating then current through the device will be V/R or maximum current rating of battery?


texts: What electronic component of a computer produces (sound) noise?

texts:
Certain mechanical components of a computer produce noise, such as speakers, fans, harddrives and disk readers.

Can electronic components of a computer (transistors, resistors, capacitors, ICs, screens, power supplies, etc.) also produce noise, or is noise limited to the realm of mechanics?


texts: How to build the simplest assembly file in MPLabX IDE 5.4

texts:
I just started learning assembly coding in MPLabX IDE 5.4. Without connecting any hardware, simulator or debugger, I simply want to build an object code file and generate a listing file from an assembly file - just to check if the IDE works. But I kept getting obscure error messages even from building the simplest possible assembly lines.
As shown in figure [1 - 6], I should have the MPLabX IDE installed properly along with integration of XC8 (which seems to package with it the pic-as assembly compiler or another name for the MPASM assembler - after I struggled for hours asking and searching why a I need a C compiler for MPASM code until I realized they were bundled). I then tested building an assembly file with one single line of comment and one end instruction. The assembly was built successfully, but I can't find anywhere for the listing file (not one *.lst file was found searching through all directories).
As soon as I add any instruction before end, the building process failed as shown in Figure [7].

Why is my assembly code not building?
Why didn't my building process (failed or successful) generate the list file like everyone else

[EDIT]

Here is the assembly code file. The project was generated from step [1-6]. I just created a new assembly file (FooFile.asm) with three lines of instruction - org, clrw and end.


texts: Electromagnetic Radiation and Communication!

texts:
I read that the accelerated charges create electromagnetic field/spectrum which consists of following different waves:

gamma
X-rays
ultraviolet
visible light
infrared
microwaves
radio waves

gamma,ultraviolet and x-rays are injurious to human so why humans are not effected by them during normal transmission of electricity as electricity is all around us. Plus only radio waves and microwaves are mostly used for communication. So how these waves are picked up from the spectrum for communication ?


texts: STM8 TIM2 interrupt not taking place. What am I missing?

texts:
I've just started using STM8 microcontrollers, specifically the STM8S003F3P6 chip, in my own custom test board. The board works and I am able to blink an LED on PA3 without using an interrupt.
However, when I try to make the blink take place in the Tim2_OVF interrupt, nothing happens. I think the interrupt is not taking place. What have I missed?? I have declared the function, "rim" has been added, checked the lst file that shows the int vector has been written. I am adding the hex file also for your reference:

My complete code is below. It blinks the led 5 times before the timer TIM2 is started. My SDCC version is 3.9.0
Your help is appreciated.

#include <stdint.h>
#include <stm8s.h>

#define F_CPU 2000000UL
#define LED_PIN     3

void delay_ms(uint16_t ms);
void mS125_isr() __interrupt(TIM2_OVF_ISR);

char tix, i,j,six, mins, b_chgLED;

void mS125_isr() __interrupt(TIM2_OVF_ISR)
{
    tix++;
    if(tix==8)
    {

        six++;
        tix=0;
    }
    if(six==60)
    {
        mins++;
        six=0;
    }

    if(tix==0 || tix==4)
    {
        PA_ODR ^= (1 << LED_PIN);
    }

    TIM2_SR1 &= ~(1 << TIM2_SR1_UIF);

}
//-------------------------------------------------------------------------
//Main routine starts
void main()
{
    PA_DDR |= (1 << LED_PIN); // configure PA3 as output
    PA_CR1 |= (1 << LED_PIN); // push-pull mode

    /* Prescaler = 128 */
    TIM2_PSCR = 0b00000111;

    /* Frequency = F_CLK / (2 * prescaler * (1 + ARR))
     *           = 2 MHz / (2 * 128 * (1 + 1952)) = 8 Hz */
    TIM2_ARRH = 0x07;
    TIM2_ARRL = 0xa1;

    for(i=0;i<10;i++)
    {
        /* toggle pin initially with a delay */
        PA_ODR ^= (1 << LED_PIN);
        delay_ms(125);
    }

    __asm__("rim\n");

    TIM2_IER |= (1 << TIM2_IER_UIE); // Enable Update Interrupt
    TIM2_CR1 |= (1 << TIM2_CR1_CEN); // Enable TIM2

    while (1){};
}
//---------------------------------------------------------------------------
void delay_ms(uint16_t ms)
{
    long li;
    for (li = 0; li < ((F_CPU / 18000UL) * ms); li++)
        __asm__("nop\n");
}


texts: Arch Linux - KiCad Spice netlist generation fails when using a pulsed voltage source

texts:
I'm new to KiCad and I'm trying to simulate a simple circuit:

This works fine. The simulation tool works, and if I generate the netlist for spice and can see no problem:

Works like a charm.
But now I try to edit the voltage model, just like this:

Now the simulation fails, and if I generate the netlist I can see that it is wrong! The voltage source is not connected as in the schematic:

The Net-_R1-Pad2_0 is missing! Am I doing something wrong?


texts: What is a good way to shift a function by 90 degrees through hardware?


texts: What is the purpose of a master-slave flip-flop?

texts: Why is having a 2 stage flip-flop desirable? Are there advantages of having a master-slave compared to a one stage JK flip flop?


texts:
So I've just received my first bench power supply and she seems like not working. But As it's my first I'm perhaps doing something wrong.

First test, I go to continuous voltage, set it to 0V. Put the negative probe of my multimeter in the ground output and the positive to the +V output. Set the multimeter to 20V DC resolution . Start to increase the voltage on the power supply from 0V to 15V (max). My multimeter is like going crazy from -1.5V to +1.5V with any loads (from 0.1V to 15V same result) But the screen on the power supply looks like displaying the correct value.
Second one, set it up to continuous current, can't change the value, always display 0A, sometimes voltage change a bit without any wires attached to the output. Usually when the current wheel is at 100%, then I can read 0A and around 1V to 1.2V.

So, am I doing something wrong or does it just doesn't work ? (In that cas have to return it asap)

EDIT : Additional tests :

I've checked the fuse, seems ok (for me shouldn't even turn on without but who knows).
I've tested with another multimeter and same result.
I've try do plug a PC fan on it 12V, 150mA, in CC or CV doesn't work but work when plugged on a 9V battery so the fan is ok.


texts: Understanding equation for capacitor-voltage

texts:
For an simple RC-network the following solution of an ODE is given:

\$u_c=A_1+A_2\cdot e^{\frac{t}{\tau}}\$

I fully understand how the solution is calculated, but I want to have an feeling for it..

Am I right if I say that \$A_1\$ is the Voltage that would be across the C if the actual circuit would remain like it is for \$t -> \inf\$?

and \$A_2\$ is the voltage defined like:

\$A_2\$ = actual voltage over the C - \$A_1\$

Is my assumption right?


texts: Why can't superconducting inductors be used in LC filter design？

texts: If I replace the copper wire of the coil with superconducting material, what will be the effect on the design of the passive LC filter?why superconducting cant design?


texts: I am making a datalogger arduino based, it reads from the adc mcp3008 and save on the sd card ADC and SD Module uses SPI . when the adc is used alone it works fine . but when adding the sd module to the spi bus, the adc output 1023 for all the channels.


texts: How do I determine which microcontroller can help me measure peak to peak voltages for my 400 kHz sine wave signal?

texts:
I have 400 kHz sine wave signal with a variable voltage between 0 V to 5 V, and I would like to use a microcontroller to measure peak to peak voltage of the sine wave. My understanding is that the microcontroller should have a sampling frequency of twice times the frequency of the signal being measured8. (Nyquist theorem).
I usually use Arduino since there are lot of example implementations online, but for the problem described, I don't know which microcontroller can help me.

Can you suggest any microcontrollers that have a high sampling rate?
Beside using a microcontroller to measure the peak to peak voltage of
the sine wave, is there any other method?


texts: Fuse blowing in 12 multimeters rated for 200mA, only measuring 12.5mA. Why?

texts:
I'm a high school electronics teacher and while doing a lab on Ohm's Law we just blew the fuses in 12 out of 18 brand new digital multimeters while measuring current, and no the meters were not hooked up directly to a voltage source!

Details:
18 Brand new 30V DC Power Supplies,
18 Brand new Radio Shack 22-810 15 Range DMM's,
Smallest Resistor 2KOhm

The students connected the resistor and ammeter in series to the power supply.

The multimeter is rated for up to 200mA and the fuse is a 315mA 250V ceramic.

Voltages ranged from 5V to 25V.  Even with the smallest resistor of 2KOhm, the largest current that would have been measured is 12.5mA.  Even if the students max'd out the power supply to 30V the current would still only be 15mA, which is way under 200mA and 250V.

So my question is, why did the fuse blow on 12 out of 18 multimeters? I was directly supervising the students and no one connected the multimeter to the power supply without the resistor. I looked for current surges by connecting the multimeter to the power supply in voltage mode and voltage didn't change at all.  I also measured the voltage with an analog multimeter and it was also solid. And I doubt there would even be current surges because the power supply should hopefully filter those out, and they should also be visible on the power supply output meter.

I contacted Radio Shack to see if there was maybe a batch of bad fuses, and of course they said no and that the fuses are not covered under warranty.

After all the checking I've done would you recommend wrapping the fuses with aluminum foil to get the multimeters up and running? It's not like I want to wrap a fuse in the source panel of a house, car, or airplane.  Only on the multimeters which are only connected to the power supply output.


texts: Toaster Oven Reflow Thermocouple Grounding

texts:
In order to create a homeade reflow solder oven, I am using a K-type thermocouple connected through a MAX6675 module and reading it with an ATMEGA8 microcontroller.

When the oven is disconnected from mains, the readings work fine. Through trial and error this lead me to determine that when the thermocouple itself is mounted to the chassis of the oven (which is grounded), the readings are no longer accurate. Obviously I know I can unground the chassis, but I don't really want to do that for safety purposes.

How can I make the thermocouple work while attached to the chassis so I can get proper temperature readings?

I was considering using some RTV silicone to put around the thermocouple intersection point with the frame of the oven, but I wasn't sure this was the best route since I would have to make sure the entire braided metal jacket of the thermocouple doesn't touch the chassis at all.

Also, since I am in the development stage, I haven't tried using the microcontroller without a direct USB serial connection to my computer and as such there are different grounds. Could this be the issue? Will it simply disappear when I move to the stand alone circuit. Thanks!


texts:
I'm trying to understand how a car alternator efficiently charges the battery.

I don't understand why a power-factor controller isn't needed to effectively use the alternator.  Current would only flow out of the windings when their voltage is a diode drop above the load (battery), so an alternator that put out 15V peak would produce current only a very short portion of each cycle. This would seem to result in a very low utilization of the windings and very high peak currents.

Or does the alternator act more like a current source than a voltage source?


texts: current measurement in series-parallel solar panel array

texts: I have a solar panel array wired in series-parallel. I know the voltages in a series network will be the average voltage, and the current in a parallel network will be the smallest contributing current. I'd like to monitor the output of each panel. I can't really do this without adding some circuitry. I'm using a Raspberry Pi 3B computer-on-a-card to monitor and control the installation. I'm thinking a relay associated with each panel and switched periodically to isolate each panel is the best I can hope for. I may be able to substitute semiconductor switches for electromechanical relays, but that is as simple as I think I can get. Any options I'm not aware of? Any alternatives? The array has panels in series to develop a 36vdc optimum voltage level for the charge controller used, and several such strings in parallel to increase the current.


texts:
I saw this circuit while going through some circuits and have been trying to solve it since. I get confused at multiple points while solving for the current.

  Since there is a buffer for feedback, does that mean that there is no current going from the Vout+ to this branch?
  Going by a technical datasheet , as seen here, I tried solving for Vout+ and Vout-. However the datasheet suggests that Beta1 or Beta2 is 0 when there is no feedback. When resistance is 0, doesn't mean that the feedback is essentially shorted and not open?
  I have solved for V (which I guess was pretty easy) but I don't know how to proceed further.
  V = Vin- (1 + R2/R1) - R2/R1 Vin+

  Can someone help?

Btw, this was not a homework assignment. I am just really bad at analyzing analog circuits :|


texts:
I'm developing a power controller which monitors and recharges a 9.6V NiMH battery pack (8x 1.2V cells @ 3300mAh) which is used to supply power to a board when mains supply is lost. The controller is able to use a trickle charge of 75mA and eventually will be able to monitor the remaining battery capacity.
The controller has to charge the battery to an "acceptable level" so that it has enough power to supply to the board (the board draws 12V from the mains supply) for at most ~30 seconds each time mains supply is lost.
My question is what would be a good method of charging an NiMH battery without damaging it? My original idea was on power up, the controller checks the remaining capacity of the battery and if it's less than 90% (e.g starts the trickle charge until it's at ~100% and then stops). However I read that an NiMh battery shouldn't be recharged until it's nearly empty according to:
NiMH or Li-ion trickle charge?
Can anyone recommend a charging method for my situation?


texts: optoisolator +ve polarity in - negative polarity out

texts:
This is an amateur application and I am just starting out with optocouplers (and electronics in general).

The optocoupler calculations in the circuit below were mirrored from an online tutorial, except the use of Vcc -5V. I am not completely sure they are correct for the application.

However, I cannot find a specific answer to my question...

Will the circuit below work in the configuration shown. Primarily, Vdd +5V and Vcc -5V, theoretically producing an output of ~-5V? (Though the circuit would be non-inverting if both sides were +ve polarity).

Is this a correct application of an optocoupler circuit, to separate sources of different polarity. It seems like an ideal application for the device.

The thought comes to mind, that Vcc could / should be connected to +ve ground. Guessing that the output would then need to be configured as an inverting optocoupler.

simulate this circuit – Schematic created using CircuitLab


texts: For connecting two micro which one is better, UART or RS232?

texts: I'm trying to connect two devices which in both of them use pic micro. I am curious to select best connection solution. I can use uart for connection between them and also with helping of MAX232 rs232 connection could be used. Anyone with experience have recommendations about it? Which is better and what are their advantages and disadvantages?


texts: How can a 11 bit address bus access 1M memory locations?

texts:
According to this datasheet of a SDRAM module it has 2 banks of 524,288 memory locations, but only a 11 bit (\$2^{11}=2,048\$) address bus.

How can an address bus with only 11 bits access all those memory locations?
Does it access rows and columns of the memory separately?


texts:
How do the first two statements (quoted below) logically correct when the third is viewed as voltage drops are only across resistors and the voltage rises are only across voltage sources? Where is the equivalence between those three versions?
The book says:

KLV has three equivalent versions: at any instant around a loop, in either a clockwise or counterclockwise direction,

The algebraic sum of the voltege drops is zero.
The algebraic sum of the voltege rises is zero.
The algebraic sum of the voltege drops equals the algebraic sum of the voltege rises.


texts:
I recently got a small LM386M-1 based amplifier kit, mainly to practice my SMD soldering. I managed to solder it, but it's giving me unexpected results.

Here's the schematic:

The input signal is supposed to be connected to NF (for positive) and GND connectors. ZV is obviously a speaker. Pin 1 is not connected.

Now about the results: When I power on the device and sent a 1 kHz sine wave to it, I get this:

The peak to peak voltage here is around 190 mV.

When I turn it off, I get this:

and the peak to peak voltage is around 1.46 V.

So it works much better when it's off than when it's on.

Also after reading the LM386 datasheet, the circuit looks a bit strange to me.

Here's the pinout of LM386 from the datasheet:

So is the PCB I got plain wrong or should I start checking out each individual component?


texts: Why does a capacitor not discharge in the same cycle it is charging in a clamper circuit?

texts:
As far as I understand, in an AC circuit, a capacitor is supposed to charge as the voltage is increasing, and as soon as the voltage starts decreasing, the capacitor starts to discharge (Since it will be the higher voltage source out of all in the circuit by then).

But in a clamper circuit, for instance in the one below:

In the positive half cycle, the diode should conduct, and the capacitor should charge. But as soon as the input voltage starts decreasing from Vm, shouldn't the capacitor start discharging?

Also, since the diode is forward biased, shouldn't the output be zero during the positive half cycle?


texts: Difference between VDD-VSS and VDDQ-VSSQ pin pairs for SDRAM ICs

texts:
I am referring to Micron MT46V16M16CY-5B IT:M DDR SDRAM. In its datasheet, I see two different set of pins, VDD-VSS and VDDQ-VSSQ.

What is the difference between them?

The datasheet suggests that the VDDQ and VSSQ have been isolated on the die for improved noise immunity. Does that the VDDQ-VSSQ pair doesn't need a decoupling capacitor between them?


texts:
I'm using atmega8 running at 1MHz. I wrote a function that counts the milliseconds and it was working flawlessly.

However, when I modified the code to count microseconds the result was weird to my eye, e.g. instead of blinking the LED each second, the LED was turned on for one second and then turned off permanently.

Is there anything I'm not aware of? Could it be related to the fact that timer2 is 8bit (some overflows happening)?

The timer.c (commented snippets are working)

#define F_CPU 16000000UL

#include <avr/interrupt.h>
#include <util/atomic.h>
#include "../include/timers.h"

volatile unsigned long milliseconds;
volatile unsigned long microseconds;

ISR (TIMER2_COMP_vect)
{
    microseconds += 50;

    if (microseconds % 1000 == 0) {
        milliseconds++;
    }
}

void timers_init(void)
{
    TCCR2 |= (1 << WGM21);

    //Set the prescaler to 8
    TCCR2 |= (1 << CS21);

    //OCRn = [ (Clock / Prescaler) * Seconds ] - 1
    OCR2 = 99;

    TIMSK |= (1 << OCIE2);

    sei();
}

unsigned long timers_millis(void)
{
    unsigned long millis;

    ATOMIC_BLOCK(ATOMIC_FORCEON) {
        millis = milliseconds;
    }

    return millis;
}

unsigned long timers_micros(void)
{
    unsigned long micros;

    ATOMIC_BLOCK(ATOMIC_FORCEON) {
        micros = microseconds;
    }

    return micros;
}

And calling the LED blinker

while (1) {
    if (timers_micros() % 1000000 == 0) {
        leds_on(LEDS_REGISTER_PORT, LEDS_PORT_LEFT);
    } else {
        leds_off(LEDS_REGISTER_PORT, LEDS_PORT_LEFT);
    }

    if (timers_millis() % 1000 == 0) {
        leds_on(LEDS_REGISTER_PORT, LEDS_PORT_RIGHT);
    } else {
        leds_off(LEDS_REGISTER_PORT, LEDS_PORT_RIGHT);
    }
}

UPDATE

The previous code has been updated to reflect the changes in soft / hardware.

I've updated the hardware with external 16MHz oscillator, set the fuse bits, modified the macros, e.g. F_CPU accordingly. Now, I just wanted to check if my counter works as I suspect but it failed - the led RIGHT that acquires timers_millis() and is supposed to turn on every second works fine but the other led LEFT flashes randomly. The only pattern with LEFT is that if it turns on the RIGHT is on as well.

I've run out of ideas and solutions. What could be wrong with my soft / hardware and how can I count microseconds precisely?


texts: Driving 5 RGB LEDs using a microcontroller

texts:
I need to run 5 differnet rgb LEDs from a microcontroller. All the LEDs will be producing the same color so there will only be 3 separate PWMs (1 for each channel of rgb.) My problem is most microcontrollers can't handle this load. What's the best way to handle this?

I was wondering if there is a microcontroller chip/board that can handle 3 separate PWM's outputting from 15 pins. If possible I'd rather not have to use a PWM Driver as this would increase the complexity of my design.

Bonus points if you guys know of a board that's compact.


texts: Differential amplifier (transistors): Which input is inverting?

texts:
For example, on the following differential amplifier it is clear, which of the inputs is the inverting one. If the voltage on the non-inverting input (base of Q1) is higher, the current through Q1 will increase. That leads to a higher voltage on R2 and the collector potential will go down. On comparison, the current through Q2 is being decreased which means less voltage through R4 and the collector (=output) will become higher. Is that correct?

However, on this circuit, it looks different: The inputs are swapped as the output is being taken from the "non-inverting transistor". However, logically the output should become lower when increasing the positive input? I don't understand how they come to the conclusion that the inputs are correct?

simulate this circuit – Schematic created using CircuitLab


texts: AC Circuit + Parallel resonant band-stop filter

texts:
My EE book says about this circuit:

"The parallel LC components present a high impedance at resonant frequency, thereby blocking the signal from the load at that frequency. Conversely, it passes signals to the load at any other frequencies"

When the current is flowing from "1" to "2" it makes sense, but the thing i do not understand is that since the circuit is AC, the current will flow in the other direction eventually (from "1" to "0" to "0").  So how can the LC Circuit "get in the way" then ? (present impedance)

EDIT:

Ok let me rephrase my question: The LC acts like a kind of "resistor" when current passes through it.  What i do not understand is if the current goes the other way, it does not have to pass through the LC so each "odd" frequency offersno impedance.

example:
at Time0, the current goes "up" so the LC presents some impedance.  But at Time1, the current goes "down" so it does not even "meet" with the LC.

EDIT 2:

I think there must be something VERY fundamental that i do not understand.  Here is an example with how i "understand" it:

Let's say the tank circuit is at resonant frequency and R1 is a light bulb.

When the current goes into the red direction, it can't reach R1 ("stopped" by the impedance of the LC) but when it goes in the blue direction it can go through R1 without even having "to stop" at the LC circuit (so the light bulb will glow).


texts: I2S Clock in Audio Codec on dev board, how is this working?

texts:
I'm using a dev board, the keil mcb4300. In the schematic, the audio codec UDA1380HN has the BCKI going to the SYSCLOCK.

According to the codec data sheet:

BCKI: bit clock input

SYSCLOCK: system clock 256fs, 384fs, 512fs or 768fs input

fs, is the sample frequency. If I am sampling at 8,000 samples per second, I assume that the lowest SYSCLOCK I can have is 256*8,000 = 2.048MHz.

According to the wiki on I2S, BCLK should be: frequency * word width * num of channels

In my case, that would be 8,000(Hz) * 16(bits) * 1(mono) = 128,000Hz

128KHz is not even close to 2.048MHz.

When I measure these settings on the scope, I see a 512KHz clock at BCKI. It is possible I have a higher sample rate than I think, and there is a firmware issue. In either case, it is working at a 512KHz clock. How is that possible? What am I misunderstanding?


texts:
I have spent the last two months trying to build a door controller for a chicken coop.
The idea is simple:

The ESP32 recieve signal from my house Wi-Fi to close or open the door.
So the corresponding relay is triggered while the corresponding limit switch is not closed.
When the limit switch is closed, an interrupt is triggered which stop the relays.

With a small fan on the output of the relay, everything is working fine. But once I use a salvage small automatic door motor, the relay stops instantly. I really don't know why but the issue is that interrupts are sometimes triggered without the switch being closed.

I don't think the code could be the issue but here it is. (pastebin.com)
Edit: Updates after recommandations

Added bidirectional TVS diode and 100nF ceramic capacitor on the motor terminal.
Added 100uF electrolytic capacitor next to the ESP-32 vin.
Added 2200µF cap and 15Ω resistor (RC filter) before the converter.

Result
For the first 3 times everythings was working fine. But after leaving the door open for 3 minutes (so upper switch closed), the ESP32 think the lower switch is closed and instantly stop the relay (I hear a double click). Since then I have tried 3-4 times and it was never working fine, except if the upper switch is not closed when ESP start closing the door.


texts: Testing crystal oscillator with multimeter crashes system

texts:
I have an old XT computer with a crystal oscillator that I would like to test.

My multimeter has a Mhz setting that as far as I know should allow me to test it. (Providing the crystal is powered)

The problem is that most of the time during the measurement the computer crashes. About 1 out of 10 times am I able to see a constant measurement (the actual frequency also displayed on the oscillator), but only for a couple of seconds. Most of the time the pc crashes as soon as I touch 1 of the 2 leads.

I would like to ensure that it is operating correctly. Is this normal and as such not the proper way to test ?
Is there another way to determine the crystal is in good working order ?


texts: Send Serial data and Ethernet data both over WiFi

texts:
we have to make an upgrade in the system which currently uses

serial communication using RS 232 which is wired(obviously).
send video data via ethernet.

So now we want to add send both the data over WiFi after taking input from ethernet and serial port and receive it over WiFi
I need some suggestions.


texts:
I'm a student in an IT school and we are trying to think of a project we could use to show 1st year students how things work behind the stage and we eventually thought of making a retro computer.

I've read many things concerning the Z80 processor, but my guess would be that we need something more powerful, we're still wondering about the architecture although ARM might be a good choice considering we'd find a lot of documentation, we have also established some special needs:

An external address bus if we need more RAM
> 50Mhz
16 or 32 bits
No BGA/QFN package
No FPGA board
A serial interface (?)
Not too expensive either as we have a limited budget

The P8X32A-D40 looks like a good CPU but lacks the amount of RAM we'd need (32k), I was more thinking about something like >1MB. Maybe the eZ80 is worth considering. We'd like answers from experimented people like you are.

Thank you.

Edit: Even though I have accepted an answer as it fills our needs, the question is still open to other suggestions as we'll have to discuss about the choices with the team of students willing to participate to the project.


texts: Why are overhead electric wires allowed to have higher voltages than third rails for rapid transit railways?

texts:
I hope this question is on-topic for this site.

The city I live in (Chennai, in India) got a rapid transit metro rail a few years ago that uses overhead electrification of 25kV, 50Hz AC voltage to power the trains. I also know several other rapid transits over the world sometimes use a different method of powering trains called a "third rail", where a solid rail close the ground, which carries 700-1000V DC voltage to power the trains.

Doing some research, I read that the overhead voltages can carry high voltages since they are located high above the ground and thus, wont arc to the ground due to the capacitance, and the sheer magnitude of the AC voltage. This seems to be the reason why third rails use such thick rails, to carry high current with such lower voltages to output the same power an overhead rail would.

Now, the rapid transit in my city has some sections elevated and some underground. The elevated sections have a catenary wire like arrangement for the overhead electrification, while the underground portions have a solid metal rod attached to the top of a circular tunnel. A picture of this rapid transit's tunnel at a crossover is here:

Now, since the tunnel is underground, the earth surrounds the tunnel from all directions, including up. Wouldnt the same problem of the third rail, i.e, arcing to the ground also occur here. What is preventing the 25kV AC from arcing to the ceiling (which is infact the earth, so it's more or less similar to grounding).

Can someone please help me understand what I'm missing here?

Edit: another relevant picture of the tunnel itself for viewer


texts: How to calculate the amount of change on gate-source voltage needed in this two stage comparator?

texts:
This is a homework question.

Below schematic of a two stage comparator is given.

I understand that \$I_5=2*I_4\$ and \$I_6\$ and \$I_7\$ can be written in terms of \$I_4\$.

It is given that in the below circuit, \$I_6>I_7\$. How much change is needed on \$V_{GS6}\$ is solved as:

\$\Delta V_{GS6}=\dfrac{\sqrt I_6 - \sqrt I_7}{\sqrt {\dfrac{K_6'}{2}*\dfrac{W_6}{L_6}}}\$

How is this equation obtained?


texts: Isolated Triac Driving on Low RMS Current Load

texts:
I'm trying to drive a triac to control contactors. Here is the circuit I'm using:

I have 3 different contactors which has series resistances like: 200R, 550R, 1.4k
When using contactors with 200R and 550R resistance, there is no problem, the driving circuit works fine. When I try to use the contactor with 1.4k resistor, circuit pulls the contactor but never release it, so it's not working properly with contactor with high resistance.
I've found an application note AN-4993 from ST indicates that "this circuit is not able to drive low rms current loads", which is same as my situation.
Here is AN-4993: https://www.st.com/content/ccc/resource/technical/document/application_note/group0/b1/6f/59/1d/45/f1/4f/30/DM00356324/files/DM00356324.pdf/jcr:content/translations/en.DM00356324.pdf
What's the reason behind this, why is this driving circuit not working with high resistance(low current) contactors?
My optotriac is MOC3021, main triac is BTA12, R1=tried many from 50R to 3k, R2=tried 100R to 350R, C1 is 100nF.
PS: When I reduce the C1 value to 50nF, it solve the problem but turn on spike started to happen on triac so the 100nF is a proper value for protecting triac from turn on issues.


texts:
Apologies in advance due to my lack of experience with embedded C.

I am working on a PIC24FJ64GA004 project in which a 16-bit PWM value need to be changed multiple times. I am using MPLAB IDE and C30.

I am wondering how I can change PWM values and where in code to change them. Is it a good idea to change PWM values in a timer ISR? In main()?


texts: PTV independent current reference without any golden voltage reference

texts: I'm familiar with building current references using Mosfets. But they are generally dependent on one of the corners (either Process,Voltage,Temperature). I haven't been able to remove the dependence on all the three parameters together. Please suggest me if it's possible to build one such without using BJT's/ bandgaps/ any external source references.


texts:
I want to make a 70 VDC power supply, output unregulated with +/- 10V variation allowed.
I also want 50 A current from it.
My input can be 3-phase 380 V mains supply.
I cannot think of a 3-phase transformer for this power supply that can give me 70 VAC at the output. How is it possible to wind this type of transformer?


texts: Matched and Identical Concepts of Transistors

texts: I realize some expressions like "Q1 and Q2 are matched" or "M1 and M2 are identical" about BJT and MOSFET configurations. I have some questions related to this. Are "matched" and "identical" concepts' meanings same? Which parameters of transistors that i mentioned above are same if transistors are identical? Thank you.


texts:
I am trying to figure out how to use a Zetex ZDS1009 IC. The chip contains 2 PNP and 2 NPN BJTs set up for current mirroring. I have learned about current mirrors, but I have not seen a 4 BJT mirror.

I have another chip that outputs a current, but it is weak and I would like to isolate it from the load. Any recommendations on how to hook up the ZDC1009 to take the current input and mirror it?

I have a 24VDC supply if needed.


texts:
Having nothing to do in my workshop, I decided to practise my skills a bit. I digged up a scrapped graphics card from the junk box and decided to try to desolder the RAM-chips (BGA) after seeing how "easy" it looks when Louis Rossman does it.

I applied flux around, launched the hot air station, and started to heat. Realizing after a few minutes that nothing at all had happened, I tried a combo of 1) other nozzles, 2) higher temperature and 3) more airflow.

At the last point I had 400 degrees celsius and 90% airflow. Zero reaction. Even heated on the back side, no reaction.

Finally I gave up and simply pried off the chip to see how the solder balls were laid out, so I could use that info for the next chip (which went just as badly).

Then I tried the 400C / 90% setting straight upon the solder balls of the pried off chip, but the solder did not even melt. My next approach was to use the soldering iron at 350C straight on the balls, with and without a wick, but not even that melted the solder.

What I had to do was to apply a large blob of fresh solder to the iron tip, drown the solder balls in it, and then - finally - I was able to remove some of the balls with the wick. Note: some of the balls, not all of them because they did not melt.

What the hell is this BGA-ball kind of solder anyway, that does not melt?


texts:
When we find electric field for a conductor having closed surface, then we take charge inside conductor zero, because in conductor charge comes on surface due to force between charges. This is what I have studied.

But for an ideal conductor, permittivity is infinite so electrostatic force must be zero inside conductor, then how charges come on surface?


texts:
appreciate if anyone is able to help to identify this connector in the photo below.

Basically i am trying to identify different types of connectors/ports around different PCB to find debug ports.

thank you in advance! :)

edit: dimensions
length: 5mm
width: 12mm

additional info: this connector seem to be used in automotive tcu


texts: What is the largest gain configurable with an opamp?

texts: With an LM358, is a gain of 5,000,000 possible? or by cascading several opamps?


texts: Connecting a spectrum analyzer without DC block

texts:
I have seen many spectrum analyzers with the warning on the RF input port: “!!! Avoid electrostatic discharge and DC voltage !!!”.

Out of precaution I always connected my signal source with a DC block but now I find the DC block filters my signal too much.

The signal comes from a line driver, there should generally be no DC voltage but I can’t completely guarantee that.

Since I have seen this multiple times I assume that this is something generic.

I understand that excessive ESD might be bad ... but DC voltage?

Does anyone know the reason for it and how seriously to take the DC voltage?

I mean, some amount of DC voltage (uVs) may always present.

Am I too over cautious? Is it safe to have a low DC voltage, say +/-1V on the signal?


texts: How does one get the common PC frequencies (33.33 MHz, 48.000 MHz) from 14.318 MHz?

texts:
I see that a lot ICs for PC use a single 14.318 MHz crystal oscillator (which is an NTSC standard frequency, so very widely available in terms of parts) to generate the clocks for PCI, USB, etc. Here's a table from one such chip, ICS932S421B.

How does this work? These don't seem obvious multiples.

I found an older datasheet RTM520-39 that at least has clue for the 33.33 MHz (but not for 48.000 MHz): 149/16 * 14.318 = 133.34, which divided by 4 gives a decent 33.3341 MHz PCI clock. For USB it said that it used 107/16 * 14.318 = 95.75 MHz and then divided by 2.

Also worth noting here is that more recent PC ICs, e.g. SLG84901, use a 25 MHz reference clock, which surely makes PCI Express (100 MHz) clock generation simpler.


texts: Is ECC feature in DDR realized with using Hamming code technique?

texts:
The fundamental formula for a Hamming coding is as below:

2^k≥n+k+1
Where k = # of parity bits and n = data bits

In a DDR system with ECC feature, every data byte will generate an additional ECC bit which makes a byte data 9 bits long.
However, if simply applying the Hamming code formula here, 8 bits of data will require 4 parity bits which will make the encoded data 12 bits long.
In this case, how can the DDR ECC feature be realized with the Hamming coding scheme?


texts:
I am taking up electronics and bought some used test equipment. I have been measuring anything and everything, sometimes with unexpected results. Above is one of those cases.

The function generator is outputting a sine wave of 1kHz at 5Vpp. It shows up as expected on the oscilloscope. The multi-meter on the other hand shows 1.77Vac and 0.02Vdc  Perhaps someone here would be kind enough to explain to me why the multi-meter does not display 5Vac?


texts: Interface between two different bus speeds?

texts:
I am creating a homebrew computer and am stuck on how to design/approach handling data requests between two different sections. I am creating it from mostly 74HCxxx series logic chips.

I have a homebrew CPU that runs at 1Mhz and has a bus to the RAM. It has 32 address lines and 32 data lines along with a Clock and Read lines. So an address is placed on the address lines and if the Read line is high then it expects the appropriate data to be placed on the data lines immediately. If the Read is low then the CPU also places a value on the data lines and the memory should update at the next clock tick. All very simple and works because the SRAM is comparatively fast (~50ns) and easily meets the timing needs of the CPU (1000ns).

I have now created a separate piece of hardware which is a video driver. It works at 12.587Mhz in order to output a low res VGA signal. It internally has some SRAM memory that stores the data for display. This works fine on its own.

But I have no idea of the correct approach to getting the CPU to be able to send data to the video driver. I want the video driver to be memory mapped and so when the CPU writes to a defined range of memory addresses the video driver will notice this and pick up the new value and store it internally. It would be nice to be able to also read from the video driver memory but that is optional.

I am a programmer and have no training in electrical enginerring so this might be trivial to others but not obvious to me. Should I be looking at FIFO buffers? Do I need some complicated interface between the two? My concern is that they are going at different clock speeds and so sometimes they will clash in timing?


texts:
I am following this application note for relay coil suppression. It suggests a diode and zener in series to be used for better contact life. I am using Panasonic ADW1212HLW relay. It's a 2 coil latching relay with a coil voltage of 12 V. Coil current is 33 mA.

Application circuit looks like this:

Z5, Z6 are 24 V zener diodes. D5, D6 are general purpose 100 V diodes.

Q1) For this setup, what power/current ratings should I select for my zener and diode? It can be safely assumed that max switching frequency won't exceed 1 Hz and it won't be switched more than 10 times in an hour. I want to design the PCB in minimum possible area. Assuming 33 mA current through the diodes during suppression period, the net power dissipated through zener will be 0.8 watts and through regular diode will be 0.07 watts. Since this transient period will be short lived (approx 2-3 ms), 50-100 mW zener should be able to handle it without any problems. Am I right in assuming so?

Q2) Is it OK if I replace D5, D6 with 24 V zener diodes? Motive behind this is to use a zener array to save PCB space. I feel that it should be fine because the second zener will have similar characteristics to regular diode in forward bias and it should be able to block 12 V easily.

Circuit will become like this:

Q3) Is it OK if I replace zener + diode combination with a bi-directional TVS diode? Motive is to use a TVS array to save PCB space. If yes, what should be the rating for the TVS diode? Will such a device work? - https://www.digikey.in/product-detail/en/nexperia-usa-inc/PESD2IVN24-UX/1727-7665-2-ND/8540781

Relevant specs:

As compared to a zener, it has another specification - Max clamping voltage which is given as 42 V. Does that mean it will fail if voltage > 42 V gets applied? Unsuppressed relay can create a voltage approx 700 V. Will it damage the TVS?


texts:
I have a 3.1inch TFT.
I have the below two pins

Can someone tell me what does the 2 pins do?
My questions :

So, I can select either 6 bit or 8 bit for the whole communication and can't change in-between, right? So, I should go completely with 6-bits or 8-bits with no changes?

I can choose only one format for the data, right ? But not alternate between both in-between ?


texts: What's the maximum number of outputs you can control from a microcontroller with n outputs?

texts:
Been pondering this for a while, and I think it's \$2^{(n-1)}\$ outputs.

If I have 5 outputs, I'll use 1 as the signal, and the other 4 as control lines to cascaded decoders, which gets me 16 outputs. This grows exponentially, so it's fine with microcontrollers with more than say 4 outputs.

But what about microcontrollers with limited outputs (eg. 4). Are you limited to only 8 outputs here?

Edit:

The project is to drive a variable brightness (PWM controlled) LED array of 32 x 4 from a single microcontroller with a limited number of outputs (4). I am wondering whether the complexity involved in this is not worth the effort, and whether to instead use a microcontroller with more outputs.


texts: Getting Equivalent Resistance WIth delta and star transforms

texts: I'm trying to solve a circuit using the delta star transformation. Im not being able to get the right answer to the problem which is 10 K Ohms. What is the best way to simplify this circuit?


texts:
I wired up a latching hall effect sensor to an LED. My power source is a stack of three 1.5v coin cell batteries.

Sensor was working just last night and then all of a sudden I tried it again this morning it is not working.

The only thing that I’m thinking is maybe the batteries aren’t strong enough because the sensor I think requires a minimum voltage of 3.5 V?

Took the leads off and tested the battery and it was showing only 2.5V..

Reason why I am a little confused is because last night I tested it by hooking it up to a very small low power LED which couldn’t have pulled that much power out of the battery...


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Hi i found this circuit in the net beacuse i want to make my preamp guitar..
I built it on my breadboard but when attach the battery, guitar doesn't make sound even if the amplificator is on... Have you any suggestion??  the circuit it's ok? or I'm wrong?
I googled a lot but i can't figure out why doesn't work...

(source: labguitars.com)
and finally I'm Italian so sorry for my bad english


texts: Powering 17 meters of RGB LED strip - Worried about voltage drop and wire size

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I'm modifying an IKEA Ramvik coffee table by mounting lengths of individually addressable RGB LED strip under the glass controlled by a Raspberry Pi. The LED strip is pretty standard; running at 5v with 32 RGB LEDs per meter, each one has an WS2801 which talk to each other via SPI. It's identical to this one: https://www.sparkfun.com/products/11272

In total there's going to be just under 17m of strip: 16 rows split into 106cm sections. I'm going to be wiring the rows up snake style and dual feeding to keep brightness consistent across the array.

At full brightness, with all LEDs on, each row of strip will draw just under 2 amps, multiplied by my 16 rows, that's 32 amps in total. With this much ampage running I'm concerned I'm going to need some hefty wires to handle the load without dropping voltage. Unfortunately the design of the table means that there's only around 3mm space underneath the glass so the diameter of the wire is important.

The 5v power supply is going to be mounted inside the table, around 0.5m from the start of the LED strips. I've been running some calculations which says even if I use 16awg wire I'm still going to see a drop of ~0.5v.

Is there any way I can negate this or do something to prevent it?


texts: Reverse voltage and overvoltage protection of USB/battery powered circuit

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Thank you in advance!   I have a simplified drawing that only shows in detail the power components (it looks messy because I deleted some non-power circuits).
The MCU is a nRF52840 that uses USB-5V on VBUS (the on-chip USB is a separate/isolated circuit from the rest of the chip's core 3.3V).  The MCU in addition needs 3.3V in my configuration.
Would like to solicit any improvements/changes to protect the circuit from accidental reverse polarity, short-circuits, over-voltage, static ESD.
ESD: standard protection for outdoors
Over-voltage: 0-5.5V operating voltage, should not be above 5.8V.
Three powering options:

Standard USB phone charger 5V  (only used to program chip)
5V external via 2-prone power-plug       (only used to charge the lipo battery)
Single Lipo 3.6V-4.2V battery   (used for normal operation, no need for USB or 5V external)

Sequence:
USB charger plugged into micro USB port (used only to program). Need to add ESD here for D+ and D-. This USB wire joins with power-plug 5V external input (the two will never be powered at the same time, only one of the other).
After USB and external 5V join, it goes into MOSFET Si2301 for reverse voltage protection.  I think I should add a 6V zener diode here and a 100K resistor to limit overvoltage to 6V.  Would that protect it from negative and positive 6V and higher, or only from negative 6V and higher (reverse voltage)?
Next the USB/5V goes to the lipo charger BQ24090 and comes out as 4.2V-2.5V.  This chip's input has reverse protection, ESD protection, short-protection, but only inside the chip and on the output.
From the charger it splits to the lipo battery and to the dual-P-MOSFET switch/reverse protection array.  This is a simplified version of the Pololu 2810 https://www.pololu.com/product/2810
The Pololu circuit can be switched by a manual switch and/or by a MCU HIGH/LOW signal.  HIGH means ON and LOW turns off the MOSFET.  Normal operation is HIGH.  Software timer inside MCU turns off the MOSFET by sending LOW which in turn "disconnects" the lipo battery and kills all power, including MCU's own power.  Only manual momentary switch can "wake" it up.
Battery is charging even if Pololu MOSFET switch-array is turned-off.
Battery power 4.2V goes to MOSFET switch-array and goes to regulator AP2112 (this may change to other model).  Before the 3.6-4.2V battery enters the regulator there is a MOSFET Si2301 with a standard 1V 20A Schottky low-voltage drop diode MBR120 and 100K resistor (need a 6V zener again?). This only allowing flow if 5V/USB power is not present on the MOSFET's Drain. If the USB or the 5V external are plugged in, the battery power is blocked and the USB/5V goes through the regulator instead.
After the regulator the 3.3V splits up into three.  The MCU draws 4-10ma, the other two draw 1ma each.  Do I need any protection in this 3.3V "bus" after all the 5V/USB protection segment?
On the 5V bus, do I need a diode before the MCU's USB-VBUS pin also for reverse protection?  The allowed voltage range is 4.3V-5.5V, so there is room for a diode drop and its not battery power being used up.


texts: Recently I've made simple buck regulator based on MC34063 from TI. I want to use that to power my SMT32 base application. Voltage on input varies from 9-26V.  I've put some part on general purpose soldering board and while using DMM I got 3.3V on output (in all input range). But when I probe output with oscilloscope I see a lot of noise I'm attaching schematics that I've used. I'm not using any post LC filter only added two 100nF capacitors on input/output to decouple some hihg f noise but that didn't help. Since this is a prototype or prove of concept layout is not optimized (it's very wide) can that play that significant role?


texts:
I'm studying power systems and this question came up: if there are two transmission lines in series and I know the impedance matrix of each one (Zp is self-impedance and Zm is mutual impedance):

Can I afirm that the impedance matrix of these two lines in series is: ?

Or should I just add the self-impedances and keep the mutual impedances as Zm?