texts:
I've designed circuit to drive an analog VU meter for my project, but I would like to test it in circuit simulation program before I build it.
Unfortunately, there is no such thing as 'VU meter' in the circuit simulation program that I'm using, so I have to use other components to make something that behaves as close as possible to real VU meter(I guess it's called equivalent circuit).
I'm not sure how to do that.
My first idea was that impedance of VU meter is inductive, so I can approximate VU meter using an inductor.

  The reading of the volume indicator shall be 0 VU when it is connected to an AC voltage equal to 1.228 Volts RMS across a 600 ohm resistance (equal to +4 [dBu]) at 1000 cycles per second.
  The VU meter and its attenuator should present a 7,500-ohm impedance to the circuit it is applied to, measured with a sinusoid signal that sets the indicator to 0

Inductor that has 7.5k impedance at 1kHz has inductance of approximately 1.19H.
However when I use just 1.19H inductor in place where VU meter would be in my circuit I get rather weird results.

I heard that some meters have integrated rectrifiers, and some doesn't.
My circuit is designed for one without integrated rectrifier.
So what is the correct way to approximate VU meter?


texts: I have designed a circuit to provide pulses with a slew rate of 3kV/50ns.  The pulse train is made up of N successive pulses with duty cycles of 10us on 40 us off repeated at 2 Hz.  My challenge is to find a track to track clearance rule to maintain my pulse integrity in copper.


texts: What is the easiest most cost effective way to print conductive ink?

texts:
I've designed some interesting prototypes with conductive paint (bare paint). I'd like to see if I can make them more space efficient via some sort of printed design. However, I would like to keep using ink on paper, ie, actual PCBs are out of the question for this project.

Are there any off the shelf cost effective ways of printing a conductive pattern to paper?

Bonus love if you know if printing is possible with a transparent solution like: http://en.wikipedia.org/wiki/Indium_tin_oxide


texts:
I used 3 different PCB design software packages (Proteus, Eagle and Express PCB) and no matter what I'm doing the DIP-28N (or any other ICs) pins are printing bigger than actual IC pin number/size.

This is my printer setting:

I tried Microsoft print to PDF, taking an actual print on paper and used other "virtual printers"...

Why can't I print at a size identical to the PCB?


texts:
I have to create a two level circuit NAND only gates for the Fibonacci from 1-8. After creating a truth table and K-Maps, I got the Function F=A'B + B'C. Then I drew the AND-OR circuit and tried to convert it NAND only circuit. After implementing it on our bread board, I did not get the correct output, so I am guessing something is wrong with my circuit diagram. I am not sure. For the truth table that we were given, the directions given were:

Each row in the truth table is identified by a decimal number.
For each row that corresponds to a Fibonacci number, specify the output to be 1.
Otherwise, specify the output to be 0.


texts: Troubleshooting multi-staged multiplexer design

texts:
I am designing a circuit to read a large (500+) number of analog sensors. The goal was to do this on all one circuit and landed on using multiplexers. I started with the CD4051B which allowed me to read 8 sensors with four pins on my microcontroller. Cool, but not impressive. Doing some more digging I came across this figure in the datasheet (page 14).

This configuration, which only shows 3 4051s, can actually handle four now allows me to use 5 pins on a microcontroller to read 24 sensors. An improvement for sure, but I needed more.
Now hoping over to the CD4556 datasheet, I came across this figure (page 5).

Then from this figure I was able to combine the CD4051 circuit and end up being able to read 256 sensors only using 8 pins on my microcontroller! This was perfect for my application.
Now for the actual question, I built a smaller version of this circuit which allows me to read 80 sensors on a breadboard to do some testing. This circuit works, but there is some weird stuff that I am hoping to mitigate.
For example, let’s say I interact with sensor one and the values move up and down as expected with the rest of the sensors remaining stable. However, the minimum value the sensor reaches is around 5000. Now, if I go over to sensor two and interact with it while also interacting with sensor one the minimum values will drop significantly (to around 1500). When interacting with the sensors without any multiplexers (or just one or two layers) the values get even lower.
Did I just hit the limitations of this system? Or am I experiencing something like leakage current that can be resolved. I will add that I am not using any type of resistors or capacitors and hooking everything up exactly as the datasheets show.


texts: Understanding and finding this DC-DC converter

texts:
Reading a circuit, I found the following component:

Which is a simple DC-DC converter. There is no possibility to find a datasheet for it. My two questions are:

I understand that VO1 is supposed to be 5V, and VO2, 13,6V. But what does the capital M mean before the 15V in VO3? Does it mean millivolts? I had never seen that before and did not find any information about it.
How can I search/find an equivalent IC in the market? I am new to this and do not really know how to search for specific components like this one.

If some context was needed, the DC-DC converter was part of the following power supply:

Thank you in advantage and sorry if this seems a too elementary doubt.


texts: Is the maximum current of a wire related with its length?

texts:
Well, I Know this seems to be a silly question..

Note that the voltage drop and the delivery efficiency is not under consideration, just the maximum current limited by the maximum dissipation power of the wire itself.

Thanks.


texts: ATMEGA328 Serial input via ISR to buffer - buffer messed on printout

texts:
Using an ISR on the atmega328 to read a string ended by a \r from UART and echo back the readout string afterwards

volatile char usart_input_buffer[8];
volatile int usart_in_count = 0;
volatile int usart_valid = 0;

ISR(USART_RX_vect)
{
    usart_input_buffer[usart_in_count] = UDR0;

    if(strcmp(usart_input_buffer[usart_in_count],'\r')) {
        usart_in_count = 0;
        usart_valid = 1;
    } else {
        usart_in_count++;
    }
}

void serial_send(char* ar) {
    int i;
    for (i = 0; i < strlen(ar); i++){
        while (( UCSR0A & (1<<UDRE0))  == 0){};
        delayms(1);
        UDR0 = ar[i];
    }
}

void init_uart() {
    CLKPR = 128;
    CLKPR = 0;
    DDRD |= (1 << PIND1);
    DDRD &= ~(1 << PIND0);
    UCSR0B |= (1 << TXEN0) | (1 << RXEN0) | (1 << RXCIE0);   // Turn on the transmission and reception circuitry
    UCSR0C |= (1 << UCSZ00) | (1 << UCSZ01); // Use 8-bit character sizes
    UBRR0H = 0;
    UBRR0L=54;
}

int main() {
    init_uart();
    sei();
    while(1) {
        if(usart_valid == 1) {
            serial_send(usart_input_buffer);
            usart_valid = 0;
        }
    }
    return 1;
}

But the result that comes back, is messed up and contains a maximum of 1 correct character, intermittently.. What could be wrong?


texts: AXI4 communication over Chip2Chip and Aurora

texts:
I am trying to exercise the communication between AXI4 master and slaves over the Chip2Chip IP core. When I have a master in one design and the slaves in the other, everything works fine - I properly access both slaves as shown below. However, if I add an identical slave into the design with the master, the master can not access the slaves of the other design. The PG067 on page 5 says that "The AXI Chip2Chip Master instance provides an AXI4 slave interface that can be directly connected to AXI Master or AXI interconnect devices." So, having an interconnect is ok.
This design works:

Here's what  does not seem to be working

Questions:

Why having an interconnect and a slave in the master design stops
working? I would expect that something is missing in the axi
communication. Additional signals?
If I had two slaves with identical addresses, one in design1 and another in design2, how would the master (or interconnect) know
which one to access? Would this be even legal, or the designer must
ensure that both designs have slaves with unique addresses?


texts: monostable 555 timer - buzzer motor and pulsing

texts:
I need this circuit to pulse an LED while running a buzzer motor for an adjustable period

RV1 and C1 should give me 1 - 5s of pulse, while RV2 and C2 should adjust the LED ramp times

The LED will be a strip of up to 10 white LEDs

Will the 555 drive these transistors, or do I need a third transistor to drive both of them, or would mosfets work more effectively?

Thanks


texts: Problem based on Latches (Sequential Circuits)

texts:
I am trying to solve the following question:

I want to know:

If the truth table for \$ Q_{n+1}\$ and \$\bar Q_{n+1}\$ is correct.
I have found out the Reset and \$Q_{n}\$ conditions. However, I see two sets of inputs (\$X=0,\, Y=0\$ and \$X=0,\, Y=1\$) for set condition.
What is the invalid input condition?


texts: How do I compute the average power from the PSD plot attached?

texts: I want to calculate the average Power from the Power spectral density plot I have here. Any help would be greatly appreciated.


texts:
Power four circuits from one adapter an output of the adapter is 12v, 3A.

Should I use the Extention cables like the daisy chain, Should I make some connection in series after the adapter to get 4 outputs.

If I applied the following steps there will be no voltage drop on 4 of the circuits?


texts:
I have a simple circuit using an LM317-type voltage regulator (ZLDO1117GTA) as a constant-current source. The input is connected to a 15v source, and the output is charging a lead-acid battery.

In one mode, the output will be connected to the battery, but the 15v source will be disconnected. However, there will still be things connected to the 15v rail, so that needs to be at 0v.

Unfortunately, the behavior I'm getting is that power is backfeeding through the regulator's adjust pin and coming out the input, driving my 15v line high. How can I prevent this? Would a diode on the ADJ pin work?


texts: Op-amp triangle-square oscillator won't oscillate in simulator

texts:
All my theory tells me this should oscillate and I should have a triangular wave at \$V_a\$ and a square one at \$V_b\$ But those nodes all come out completely zero.

I don't understand what I have incorrect, could someone please point me in the right direction?


texts: Measure current on a constant current source

texts:
I need to measure current on a constant current source(LM317), because I am using a 3v3 chip I also need a voltage divider to read it. Will this circuit work Or will it wreak havoc trying to increase voltage to drive current over the voltage dividers?

simulate this circuit – Schematic created using CircuitLab


texts:
I made a simple full wave rectifier using a center tapped transformer and 2 1N4007 diodes.
The DC output is around 14 volts but when I connect a 100uF capacitor with the output leads of the DC output, I get around around 21 volts DC and 44 volts AC.
Without the capacitor it works as expected but with the capacitor why is this the case?


texts: How do you create an Octagonal Microstrip Inductor without a bridge/underpass in NI AWR Microwave Office?

texts:
Microwave office has a built-in element like "MOCTIND", but it has a bridge from the center and I would like to construct my own without the bridge that comes with the model.  (They do have non-octagonal bridgeless versions, but I don't see an octagonal version.)
Is there a way to modify the element code (or create my own parameterized octagonal model) to place the port in the center without the bridge so I can do my own implementation?


texts:
For my master thesis I'm simulating the cooling of an 2.5D microchip (2 dies next to each other on an interposer (slice of silicium with interconnections)). So I want to calculate the flow over the chip and the attached ducted straight fin heat sink. The fluid can only flow through the fins of the heat sink. The inlet velocity is over 2 m/s so that there is no influence of natural convection. The flow can be seen as a combination of a forward facing step and a backward facing step.

I calculated the Reynolds number between the fins and it was 1075. So the flow should be laminar (or at least that is what i think). Because of the high velocity the flow because unsteady behind the heat sink (I can only calculate the flow with the transient option in fluent). I assumed that it was an unsteady laminar flow. But when I look to the velocity in a point, it isn't periodic in time. So the flow behind the heatsink could be in the transitional or turbulent regime. But I'm not sure of that.

Is there a way to check the regime behind the heatsink?


texts: Very basic question about vectorial representation of an electromagnetic wave

texts:
This might sound a dumb question but I have some confusion about relating em fields as propagating vectors.

Below shows how an electromagnetic wave travels:

But let's focus and look at point X below:

The point X is outside of the E and H vector fields.

Does that mean there is no electric or magnetic field at that point?


texts: How does a common-emitter rail-to-rail opamp output stage work? Is there a discrete example?

texts:
I'm reading an article about how a rail-to-rail opamp works. The materials from Maxim and Analog Device all mentioned that, in a conventional operational amplifier, the output stage, in its essence, is a pair of NPN/PNP forming an emitter follower.

One can instantly recognize that the principle of operation is similar to a push-pull output stage found in discrete Class-AB amplifiers, the output stage is used as a buffer for current gain. The input is at the center of the diodes, and since it's an emitter follower, the output is a replica of the input. This arrangement comes with a Vbe drop, with means the output can never get to the power rails.

The articles continue to explain that in order to overcome this limitation, in a rail-to-rail opamp, the output stage is a pair of PNP/NPN transistors forming an common-emitter amplifier. And in this arrangement, the maximum output swing is only limited by Vce_sat, and is able to get very close to the rail.

But I have never seen this configuration before (The only time I've seen it before, is in The Art of Electronics as a bad example of a miswired Class-B amplifier - once an input is applied to the bases, both transistors are turned on and they blow up...).

How does this output stage supposed to work? How do I apply an input? Are there some practical examples of this circuit with discrete transistors?


texts: I have disassembled 20 broken hard disks and taken out the motors, thinking they might be useful. However, they didn't work using DC current, because they required some kind of control circuit. Now I have a project (electrolysis) that might require to use those motors as generators. I want to know what kind of current these generate (DC or AC)? They were able to power an LED but as LEDs are diodes, I couldn't tell whether that motor generated AC.


texts:
There are times that a design is given constraints in the placements of components. For me, I would like to start from placing them first before creating the schematic.

Is there such a capability in Eagle? As I remember, such function is available elsewhere in OrCAD or other tools

Also, I want to know if this is a practical requirement in design i.e. is it common?


texts: How to simulate a thermistor input without a thermistor

texts:
I would like to test one of a data acquisition modules.  The input type is thermistor.  I do not have a thermistor.  I simply want to know if the module is able to read a temperature. I would like to know if it is possible to test the channel by just placing a jumper across the terminal(applying a 0 ohm resistance).
Thermistor module

Will this work?
Is there a type of thermistor which has a known temperature at 0 ohms?

The module I am using has an interface to view the corresponding temperature value.


texts:
I would like to build a proximity tracking system. A a central unit small enough to fit on a key chain or necklace that would be able to detect as soon as a tagged object is farther away than a dozen or so feet.

I was thinking the central unit would consisting of a Arduino Mini and some sort of RFID reader. I would use semi-passive RFID tags since passive tags wouldn't be able to provide the range I need.

I haven't been able to find much information on semi-passive RFID tags. Would I be able to get the range I need with the form factor constraint I have? How can I obtain some semi-passive tags? I wasn't able to find any on digikey or any information on designing them myself.

Will I need to use fully active tags? Or maybe there's a better solution that doesn't use RFID?


texts:
I'm relatively new to electronics. I've seen a few circuits online, I just wanted to check that this schematic I drawn would work.

The purpose of the photodiode will hopefully be to read a modulated LED signal.
Is the choice of Op-Amp suitable to the job?


texts: Raspberry pi 3 access point - broadcast power calculation / measurement?

texts:
Using hostapd to turn a Rpi3 into a wireless access point on 2.4Ghz
band.

How can I estimate the broadcast power of this AP?
PS adapter is 5V 2.5 A.  P=IV = 12.5 watts, but, I think that's just
the available source adapter power and not really what would be used.
What could I do to measure the broadcast power of this?

SoC: Broadcom BCM2837
Broadcom BCM43438 chip provides 2.4GHz 802.11n wireless LA
Networking: 10/100 Ethernet, 2.4GHz 802.11n wireless

Looking at the specs of the BCM43438 I see:

So looking at the table I see a range from 37 to 41 mA * 3.6V = max 0.1476 Watts.

Does this look right?  And, is that powerful for an access point if so?


texts: Why the output voltage of dsPIC IO ports is not constant?

texts:
I expect output voltage of dsPIC pin should be 3.3V, and this seems to be true when the output pin is connected to high resistance.

However, when I connect to low resistance, the voltage of output pin is pulled low.(The image below shows the voltage is 2.75V).

I suspect it is caused by the circuit in the microchip, but I don't know how to analyze it.

BTW, here's the datasheet of this chip.


texts: System-verilog generate module instances and pass input/process output data

texts:
I wrote a module in System Verilog, I need 32 modules, so I am using generate statement for instantiation.

The problem is that in every rising edge of clock I need to instantiate new values to the modules and then need to choose one of them (in the same posedge clock, depending on the outputs of the modules, in my case the min between all the module output).

How can I do that?

This is my current version of the code:

    genvar j;
    generate
        for (int j=0; j<32; j++)
         begin: module_instant_loop
            always @(posedge Clock)
               begin
                  MyUnit unit[j] (.A(TEST1[j],.B(TEST2[j]),.OUT(MYOUT[j]);
               end
            end
         end
    endgenerate

And this is the code that I want to add:

for (int i=0; i<32; i++)
    begin
        if (MYOUT[i] < MINIMUM) MINIMUM=MYOUT[i];
        if (MYOUT[i] > MAXIMUM) MAXIMUM=MYOUT[i];
    end

How can I add the loop to my code?


texts: Power Distribution Blocks for DC voltage?

texts:
So, I'm pretending to use a somewhat uncommon component for my generator system. With an alternator, I will generate 24 V DC and a maximum of 100 A. My question is, can I use a power distribution block like one of these?

My initial guess would be that yes, I can use it, but as these products are not specified for what I intend to do I'm asking if my project will bump into any strange electrical problems.


texts: Input impedance of audio amplifier, unclear from datasheet

texts:
I have a AN7190NK audio power IC. It is a amplifier for the car radio.
I want to know it's input impedance.
In datasheet it states that:

Input impedance ZI VIN = ± 0.3 VDC  28 kOhm

I don't really understand what Vin = ± 0.3 VDC mean. These are conditions at which impedance was measured. What does that mean?
The VDC is not mentioned in datasheet after that.


texts: Topology for ideal cutband response (-20dB per decade per order) for passive, low pass, constant output impedance filter

texts:
I am trying to develop a low-pass constant output impedance filter.
The output impedance must be within ±10% of 5Ω from DC up to 1GHz.
The filter is driving an open load (>10M) and must filter current noise above 1kHz.

To build such a circuit, I would normally use a transimpedance amplifier with a low pass feedback.
Unfortunately, the filter must only be composed of passive (RLC) elements.

Typical low pass filters have the problem that their output impedance changes after the cut-off frequency.

My current solution requires that I must add a resistor (R2) to a LC filter (L1-C1) to prevent the capacitor from shunting my output impedance. By doing so, the frequency roll-off corresponds to a filter with half the order. i.e. in this case, -20db per decade instead of -40db per decade.

Is there a way to achieve -40dB per decade without cascading other elements? There seems to be a lack of literature on constant output impedance passive filters.

simulate this circuit – Schematic created using CircuitLab

EDIT: Parasitics were omitted to keep the question about the topology of the filter.
In practice, I have the ESL of C1 and the parallel capacitance of L1. These parasitics are compensated by a second LC+R stage with smaller values, which have smaller parasitics.


texts: How to find Base CPU Time and Memory-Stall Time

texts:
The program described below runs on a multiple issue processor with a 3-level CPU cache, a 4 GHz clock frequency, and the following performance metrics:

Miss Penalty R/W
Data Miss Rate
Instruction Miss Rate

L1 Cache
2
5%
2%

L2 Cache
5
2%
1.3%

Main Memory
100
0.3%
1%

with

Instruction Class
Instruction Count
IPC

Branch/Jump
2x10^5
1.1

Load/Store
4.1x10^4
0.9

Arithmetic
3.6 x10^6
1.5

Float Add
5.5x10^5
0.25

IPC is given instead of CPI because of multiple issue
What is the base CPU time of the program? And what is the amount of time consumed by memory-stall clock cycles?
My attempt to answer this has been:
For Base CPU Time, I am using the following formula:
CPU Time = instruction count / IPC * T_clk
for each instruction count, so
Base CPU Time = (2x10^5/1.1 x 0.25) + ... + (5.5x10^5/0.25 x 0.25)
and for memory-stall clock cycle I am calculating
The number of stalls (miss cycles) per instruction can be treated as a portion of CPI. To get this value in terms of time, multiply this rate by the clock period:
MST = summation (miss rate_i x miss penalty_i) x T_clk x Instruction count
where i is the instruction class. Memory stall cycles/times are always subdivided into Data and Instruction. So the total MST is equal to MST_data + MST_instruction.
Is this the correct approach? I have doubts since I am using all the instructions to calculate the MST of the caches and main memory, and I don't know how to split it. I also am not sure if I should be using all the instructions to calculate the Base CPU Time, since part of those instructions contribute to the miss rate.


texts: Can this shift-register circuit be simplified?

texts:
I've created a circuit using a shift register to drive a 7-segment display which is all controlled by an Arduino Uno.  The circuit appears to work fine, I have a sketch running which simply counts from 0 to 9 over and over. Attempting to put this together on my tiny breadboards was a bit of a challenge due to the number of comonents and connections necessary.

My question is, are all the components I used necessary?  Could the circuit be simplified by re-arranging and removing some of the components?

The circuit

simulate this circuit – Schematic created using CircuitLab

Datasheets for the display and shift register:

ELS-321HDB 7-Segment Display
TI SN74HC164 8-bit Shift Register

About the design

I was unsure from the datasheets whether or not I could drive the LED display directly from the outputs of the shift register.  Based on the resistors I had available, I calculated that each segment would draw roughly 11mA. If all 7 segments were on that would then be a total current of 77mA.  From what I see the datasheet for the shift register, Absolute Maximum Continuous output current is 25mA, but it's not clear to me if that is per-output-pin or combined.  I assumed combined.

In order to try and avoid pushing too much power through the shift register I decided to use it to drive transistors instead. The only way I could see to get the transistor to work as an on/off switch was to tie it between the resistor and the segment display.  With this arrangement I figured when the transistor was closed, current would bypass the display and flow through the transistor resulting in the display being off. When the transistor was open the current would instead flow through the display and turn the segment on.


texts: DHT21 / AM2301 sensor not measuring humidity

texts:
I am trying to use a DHT21 with a Lamobo R1 aka Banana PI R1 to read temperature and humidity, with Armbian/Jessie and a 4.5.2 kernel. A Lamobo R1 is basically an A20 board raspberry pi compatible, with an inverted compatible raspberry pi 2 bus.
I have setup it up in GPIO5, raspberry pin compatible 24, WirinPi 5, physical pin 18, according to a table here, plus the GND and +5V pins.
I tried to read the temperature and humidity with and without the recommended resistor. While the temperature is reading fine, and is also corroborated by a  DS18b20 sensor connected to GPIO2, the humidity is always at 99.9%.
I have installed the WiringPi compatible library from WiringBP repository.
However, using for instance DHT21-AM2301 or lol_dht22 I have got always the output of Humidity as 99.9% or 99.90%
A custom kernel module for this chip, am2301 simply hangs the machine.
What I have found until now is:

It seems to work with Raspberry and Arduino;
The DHT21 is highly sensitive to timings, even in the original raspberry;
Some people did report it only worked in GPIO1 and GPIO2 in the original raspberry, whilst the other GPIOs had much greater latency;
There is a much more complicated hardware setup to connect it to a I2C, in which I am not particularly interested;
Some people also theorise it only works with kernel 3;
The Lamobo R1 seems to have a pullup pin bus by default;
Readings can be done only every second due to chipset limitations;
The physical implementation of the R1 bus compared to the rpi allows me to get by without the resistor;
The limit of cable seems to be 25m, and there are anecdotal tales of people achieving 60m with UTP cable. Mine is no longer than 20cm;
It cannot be exposed to direct sunlight due to maintaining the chemical balance;
Said chemical balance degrades over time (2-3 years?).

Does anyone has anything else to add?
Additional notes as per comments:

Humidity comes first than temperature;
As @ChrisStratton correctly theorised, humidity bits are all 1;
I have already tested two DHT21 sensors with the same results.

The output of
gpio readall

is
+----------+-Rev3-+------+--------+------+-------+
| wiringPi | GPIO | Phys | Name   | Mode | Value |
+----------+------+------+--------+------+-------+
|      0   |  17  |  11  | GPIO 0 | IN   | Low   |
|      1   |  18  |  12  | GPIO 1 | IN   | High  |
|      2   |  27  |  13  | GPIO 2 | IN   | Low   |
|      3   |  22  |  15  | GPIO 3 | IN   | Low   |
|      4   |  23  |  16  | GPIO 4 | IN   | Low   |
|      5   |  24  |  18  | GPIO 5 | OUT  | High  |
|      6   |  25  |  22  | GPIO 6 | IN   | Low   |
|      7   |   4  |   7  | GPIO 7 | IN   | Low   |
|      8   |   2  |   3  | SDA    | ALT5 | High  |
|      9   |   3  |   5  | SCL    | ALT5 | High  |
|     10   |   8  |  24  | CE0    | IN   | Low   |
|     11   |   7  |  26  | CE1    | IN   | Low   |
|     12   |  10  |  19  | MOSI   | ALT5 | Low   |
|     13   |   9  |  21  | MISO   | ALT5 | Low   |
|     14   |  11  |  23  | SCLK   | ALT5 | Low   |
|     15   |  14  |   8  | TxD    | ALT0 | Low   |
|     16   |  15  |  10  | RxD    | ALT0 | Low   |
|     17   |  28  |   3  | GPIO 8 | IN   | Low   |
|     18   |  29  |   4  | GPIO 9 | ALT4 | Low   |
|     19   |  30  |   5  | GPIO10 | OUT  | High  |
|     20   |  31  |   6  | GPIO11 | ALT4 | Low   |
+----------+------+------+--------+------+-------+


texts: How to implement Clock Gating Style RTL into synthesis?

texts:
I'm studying to implement a Clock Gating in RTL.
So I've followed as the below
https://www.design-reuse.com/articles/23701/power-analysis-clock-gating-rtl.html

always @(posedge clk)
begin

    if (enable_in)
        gclk <= clk;

end

But Problem is that I encounter an Error Message when I synthesis above code.
TOP.v:55: Clock clk used as data. (ELAB-305)

It does not makes sense Because this is just gating signal not a data. If I wrong, Could you please guide me?
How to implement Clock Gating STYLE code into RTL ?
Full Code :
module  omsp_clock_gate (

// OUTPUTs
    gclk,                      // Gated clock

// INPUTs
    clk,                       // Clock
    enable,                    // Clock enable
    scan_enable                // Scan enable (active during scan shifting)
);

// OUTPUTs
//=========
    output reg        gclk;           // Gated clock

// INPUTs
//=========
    input          clk;            // Clock
    input          enable;         // Clock enable
    input          scan_enable;    // Scan enable (active during scan shifting)

    wire    enable_in =   (enable | scan_enable);

    always @(posedge clk)
    begin

        if (enable_in)
            gclk <= clk;

    end

endmodule // omsp_clock_gate

module TOP(Clk, Reset, Crnt_Instrn, Zro_Flag, Carry_Flag, Neg_Flag, Return_Addr, Current_State, PC);
        input                   Clk;
        input                   Reset;
        input   [31:0]  Crnt_Instrn;            // Current Executing Inst
        input           Zro_Flag, Carry_Flag, Neg_Flag; // Flags from ALU or Stack
        input   [7:0]   Return_Addr;
        output  [2:0]   Current_State;          // CurrentState from Control FSM
        output  [7:0]   PC;     // Program Count

        wire                    Incrmnt_PC, Ld_Brnch_Addr, Ld_Rtn_Addr;
        wire    [2:0]   CurrentState;

          omsp_clock_gate u_omsp_clock_gate (
    // OUTPUTs
        .gclk   (   gclk        ),                      // Gated clock

    // INPUTs
        .clk    (   Clk     ),                       // Clock
        .enable (   Neg_Flag        ),                    // Clock enable
        .scan_enable    (   1'b0)                // Scan enable (active during scan shifting)
);

        FSM     I_FSM (
                .Clk(Clk),
                .Reset(Reset),
                .CurrentState(CurrentState)
        );

        DECODE  I_DECODE (
                .Zro_Flag(Zro_Flag),
                .Carry_Flag(Carry_Flag),
                .Neg_Flag(Neg_Flag),
                .CurrentState(CurrentState),
                .Crnt_Instrn(Crnt_Instrn),
                .Incrmnt_PC(Incrmnt_PC),
                .Ld_Brnch_Addr(Ld_Brnch_Addr),
                .Ld_Rtn_Addr(Ld_Rtn_Addr)
        );

        COUNT   I_COUNT (
                .Reset(Reset),
                .Clk(Clk),
                .Incrmnt_PC(Incrmnt_PC),
                .Ld_Brnch_Addr(Ld_Brnch_Addr),
                .Ld_Rtn_Addr(Ld_Rtn_Addr),
                .Imm_Addr(Crnt_Instrn[7:0]),
                .Return_Addr(Return_Addr),
                .PC(PC)
        );

        assign  Current_State   = CurrentState;

endmodule


texts: Is my explanation of a USB battery pack correct?

texts:
Being the most technically proficient person in my office I was asked to answer this, but not being sure of myself, I wanted to make sure I explained this well.
A customer asked of the device "how many watts is it". The only technical data I had onit was it's mAH (2200). Our guess is that they might not really be asking the right question, so we wanted to give them an answer that was better than their question. I told my boss this:

  The USB chargers should provide power like this:
  500 mA
  5 V
  2.5 W

  Since it is 2200mAH and it outputs 500mA, it would be expected to last
  up to 4.4 hours, depending on the device it is charging.

Is my explanation (mostly) correct?


texts:
I'd rather not destroy any of my Wii kit, so I'm wondering if anyone knows what voltage I should drive the Wii Sensor bar with if I wanted to use it as an IR transmitter for a project.

If you're feeling extra helpful, any recommendations for low power IR phototransistors which would be able to detect pulses from the bar would be helpful!


texts: Charging a LiFePo4 12v 40ah battery with 10A charger instead of 6A

texts:
I purchased a Bioenno Battery with 12v 40ah.
I already have a 10A LiFePo4 battery charger.

The new battery says charging current should be 6A.
Can I charge it with a 10A charger since it has a built in PCB/BMS?
Seems like you would have to have a charger for each type of battery otherwise.

Data sheet?

UPDATE 20 Jan 2020:

I emailed Bienno and asked them the same question (since the Battery and the charger are both theirs).

Their response was "That's fine."


texts: Significance of cut-off frequency in a low-pass filter

texts:
My question is: why do we choose cut-off frequency to satisfy that the magnitude of transfer function \$ H(\omega) = \frac{1}{\sqrt{2}} \$?

Therefore I am not asking how cut-off frequency is calculated as \$ \sqrt{\frac{R}{L}}\$, but I am asking why it is chosen that way.

I know I sound a bit confusing but it is because I am confused. Thanks in advance


texts: Can I replace a 3.8V 2900mAh battery with capacitors?

texts:
I have a 3.8V 2900mAh battery and I was thinking if it's possible to replace it with a bunch of capacitors

Here more specs about the battery

This is for a mobile phone and was planning to use capacitors instead of batteries since I use the phone as a modem and it always powered by its charger (Not sure how much power is given to the battery by the phone while charging) and I prefer to power the capacitors by what phone gives to the battery if its possible


texts: What is the difference between power inductors and decoupling inductors?

texts:
I am trying to pick an inductor for use with switching regulator with switching frequency of 500KHz.

I looked at single inductor manufacturer which has two line up. One saying "Inductors for Decoupling Circuits", and the other saying "Inductors for Power Circuits."

The links to datasheets are below.

[Datasheet] Inductors for Decoupling Circuits

[Datasheet] Inductors for Power Circuits

What are the difference between the two other than the current capacity?

May I use any of them if both fits my current budget?


texts: Circuit to switch charge controller inputs +18V non-regulated panel vs 12V regulated panel

texts:
Problem: Multiple input voltages that need to be sorted.

Solution: Switch the current path based on voltage level:

Path 1 - Battery terminals (panel has been regulated to 12V)

OR

Path 2 - Rooftop solar input terminals (panel is unregulated and 18V or higher)

What should go into this unlabeled box in the middle to sort the inputs?

I hear that a Schmitt trigger may work?

Solution must be able to pass 30A.


texts: Please help me critic my H-Bridge MOSFET motor driver circuit

texts:
This is the first time I build the H-Bridge MOSFETs driver circuit. Due to some limitation of desired components. It is all SMD, so I don't really have a proper way to test it before building the board. Can you please take some minutes to look at the schematic and if there is something wrong that catch your eyes, please let me know!

Here is the schematic

Edit:

The FET part number is SISS98DN-T1-GE3

The Driver is IRS2004

Walkthrough:

The circuit will receive a PWM signal from uC at 1 kHz to control the speed of the motor as well as the direction.

The bootstrap components are designed to switch the high-side gate at 15V maximum (actual switching voltage is 13.9V).

The gate driver is synchronous half-bridge type. I believe when there is an input signal, the high-side FET would turn on and the low-side FETs on both sides would stay off? (I am not really sure about this part)

Here is the block diagram of the Gate Driver

Note: I study a many different gate driver circuits and came up with this. Still in the learning phase. B1


texts: Ohms law and LED driver efficiency? How can this possible be true?

texts:
I am having a meltdown with a Chinese supplier at the moment and hope dearly that someone can help.

I have an LED driver that is in my mind 28.8W. The output of the driver is 48 V @ 600 mA (48 V x 0.6 A = 28.8 W).

I was however talking to the Chinese supplier who tells me this is a 32.72W driver.

They are justifying this by quoting me P=U·I/efficiency formula (48 · 0.6 / 0.88 = 32.72).

Now what I can't understand is how a driver that puts out only 28.8 W by definition of Ohms law can this be then considered 32.72 W by terms of this formula regarding efficiency? Surely this is simply not possible?

I have gone around in circles trying to get my head around it but can't seem to get past the fact this won't power 30W of LEDs.

Can anyone explain this to me or are they trying to pull the wool over my eyes?

Thanks Guys really impressed with you responses and you have confirmed what I suspected. Essentially he trying to sell the input power as output power, which is what I thought. Absolutely ludicrous.

@ Marcus I think you are absolutely right need to nail down specs before I even have a discussion with these jokers. Unfortunately I buying off the shelf and not having anything specifically tailored. I am committed to the purchase unfortunately luckily it doesn't actually matter for the project but lesson learnt.

Out of interest are there any EU or US conventions of directives for the labelling of Power supplies for output power rather than consumption?


texts: RC filter on ADC voltage reference pins: overkill or necessary?

texts:
I've been scouring the web for circuits suitable for reading RTDs using ADCs. In one document from TI it is suggested that the following filter be placed on the inputs of the voltage reference pins (REFP0 and REFN0) which matches the filter on the analogue inputs, to reduce noise:

I haven't seen this recommendation in any other design and was wondering if it is really necessary?

My second question: suppose an RC filter would in fact help on the voltage reference pins. I don't understand why REFN0 pin also needs a filter? Wouldn't it be better if I directly connected it to GND and removed the R and C circled in red?


texts: Measure resistance of multiple unknown resistors with single analog pin

texts:
I'm currently using the circuit below the measure the resistance of multiple resistors (R1 and R2) using a voltage divider with a known resistance (R1). I'm using a PNP transistor for every unknown resistor to be able to measure them separately.

The goal is to be able to measure a lot of different unknown resistors with a single analog pin. Is there a better way to do this?


texts: Mini-UPS schematic - load-sharing of battery pack and power source

texts:
I am a beginner working on a mini-UPS project for a low-power server (computer).
I've made the following schematic where I'm trying to achieve the following:

Charge 3S 18650 battery pack BMS with 12.6V @1A
Load-share between battery power and DC in @12V
Pull maximum 2.5A from the DC in (I would like the computer to be able to pull more from the battery pack if there is a momentary peak)

I've watched a ton of videos and read about load sharing, how to connect multiple power supplies, etc. but I really would love to benefit from someone's experience to see if I am headed in the right direction. I added 2 Schottky diodes on the positive of the VOut on the two power sources so they wouldn't leach power from each other, as well as a capacitor to smooth interruptions. To simplify this, I didn't draw out the circuit of the BMS board connections to the batteries.
I am looking to answer the following questions:

Would this schematic work?
Regarding the load sharing - how does the "failover" between the DC in and the battery power work? Does it just happen when there is a drop in voltage, it will just start pulling current from the higher voltage source?
Do I need some kind of MCU and MOSFET setup to intelligently switch power? I thought I did, but have seen other setups like the one I've got here referenced in DIY videos - what are the disadvantages of the "dumb" approach?

Here is the schematic:

Here are the parts referenced:

CC buck convertor
Boost convertor
BMS board


texts:
My understanding is that SEPICs, Cuks, and Zeta converters all provide a stable output voltage despite an input voltage that can vary either above or below what is desired. The SEPIC and Zeta maintains the same polarity, while the Cuk reverses the polarity but by making an isolated version you can maintain the polarity.

Given an application that benefits from these intrinsic properties why might I consider one over the others?


texts: Diode capacitance and Drain to Source capacitance in function of the frequency

texts:
I m trying to determine what is the biggest parallel capacitor between a P-CHANNEL MOSFET and a diode. The datasheet give the diode capacitance @ 1 MHz and the different capacitors into the MOSFET @ 1 MHz. The drain to source capacitance is equal to Coss-Crss. Nevertheless, I do not kow how the capacitor into the diode and the MOSFET evolve in function of the frequency. It may decrease for the diode and it may increase for the MOSFET. I would like to determine the two parallel capacitances for each components at a frequency around 50 kHz - 100 KHz. Here are the datasheets:
https://www.infineon.com/dgdl/Infineon-BSS84P-DS-v02_07-en.pdf?fileId=db3a304330f68606013118ac7a9b4549
https://www.vishay.com/docs/88959/byg22a.pdf
Thank you very much !


texts: Is there anybody can show me how the voltage distribution of this MOSFET?

texts:
I have a problem to solve.
Below is the my question

I want to see how the voltage distribution of this mosfet.

Like this(below)

at this case, it's e-Density. (It's my school's data, I can't run this program.)
But I want to see Voltage all region.
Is there anybody can help me?


texts: I'm working on a project and I need to use 3 parallel bjt to give me 20 A current.Total power dissipation is 356 W.I know how to calculate a sink for one transistor,but in this case I'm not sure what is Pdiss in Rja=(Tj-Ta)/Pdiss, is it 356 W or ,as I'm using 3 2SA1302 bjt,356/3 W.Also is Tj (junction temperature) 150 C (for one 2SA1302) or is it 3*150 C ?


texts: Potential difference between DC floating power supply and earth ground

texts:
I have a question about a simple DC floating power supply: it is as simple as possible, secondary coil -> bridge rectifier -> filter cap, as shown on the figure below.

If I connect the input of the oscilloscope between the negative terminal of this simple floating power supply and the earth ground (which is the negative terminal of the oscilloscope input too), I can measure 140 Vpp with the frequency of 50 Hz (figure attached).

Why is this high amplitude voltage present between these two terminals? Can somebody explain to me the causes of this measurement result?


texts: torque-speed characteristics of induction motors

texts:
I have come across a website which says that zero staor resistance makes the maximum torque constant for different frequencies while keeping v/f ratio constant. And a non-zero stator resistance affect the value of maximum resistance.
My question is: How come that having non-zero stator resistance causes the maximum torque to decrease significantly as we deacrease the frequency of the stator (while keeping v/f ratio constant) {while it is not the case for zero stator resistance}?

Thanks


texts:
I am trying to charge an 850mah 3.7v battery using a TP4056 circuit that will recieve regulated 4.2v at a maximum of 500ma though the current can drop due to it being regulated solar power. What will occur if the regulated voltage is below what current I set the TP4056 to charge. I am using the TP4056 due to its trickle charge feature and its overcharge protection. Can I just set the current on the TP4056 to the max and let it charge at whatever current it has available?

Is there any chip that justs stop the flow of current once the battery has reached 4.2?


texts:
In the datasheet, they wrote:

Rated frequency of operation with / without load 6 / 1200 min-1

What's the signification of this line ?

When they talk about Mechanical endurance cycle, is it open to close or  open to close to open


texts: Do any commercial products use dead bug construction?

texts:
I'm talking about connecting electronic components without using a PCB. Soldering such an assembly is pretty fast if you have a jig holding the components in place.

(The examples below are laid out in 2D like a PCB, but dead-bug construction often isn't)

source


texts:
I'm trying to measure current to a DC motor on an RC car I took apart. The car is powered by 3 AA batteries and seems to be made of three different boards. Two of the boards are for switches and LEDs, the other is the main one in this shot that I'm trying to measure so I can replace it with my Arduino.

I am trying to measure the amperage to the motor, as well as that motor in the back of that shot. I have tried using my multimeter on 20mA, 200mA, and 10A with no sensible reading and it always stalls the RC car.

Shouldn't I be able to get a reasonable result?

Edit: All the pictures I have of it are in this page

I've tried connecting on the motor directly and on the wires leading to it  both before and after that capacitor.

Edit: Thanks again for the help everyone. I'm going to give it another go soon and post some pictures of the configuration once I get it going


texts: Phase-shift oscillator (high pass configuration) why only 2 resistors to ground?

texts:
Today I built another phase-shift oscillator (you can see my full notes here). The circuit is based on those I've found online, and uses the capacitors in a high-pass configuration:

The circuit works, but I'm confused about two things:

I've labeled a resistor RXXX in the schematic, but did not fit it in my circuit. It seems like it should be required to allow the final capacitor to work. But the circuit doesn't work if it's fitted. Why?
What is the purpose of the resistor above RXXX going from the base to the positive supply?

I'm guessing these two questions are probably related?


texts: Microcontroller hanging during serial communication

texts:
I was working on a project in which microcontroller is communicating serially with computer.

Initially it works properly but after some duration (i.e 2-3 hours) microcontroller get hanged.

I think it hangs due to serial communication with computer. To verify it I have written a program to for microcontroller as well as for computer to transmit and receive data serially.

In my program I am first transmitting string of five characters serially from computer. Microcontroller will receive the string and re-transmit the same string to computer.
Computer will receive the string transmitted by microcontroller.

Now I have transmitted string and a received string at computer, I am comparing both the strings and if they are same I am writing '1' in a file and '0' if they are different.

I want to know that my process to verify serial port communication is correct or not?


texts: Nooby, can't control a DC brushed motor with a MOSFET, please help

texts:
First time trying to control a dc brushed motor with a N-Channel MOSFET.

I believe I understand how it should work but it just isn't and I am stuck as to what to test and fix or change.

I have a small Dc brushed motor(if i connect it directly to +5V power supply it works fine) that i connected to ma IRF1010N MOSFET as per the schematics.
Arduino runs just blink code (but it also doesn't work if i manually connect gate to +5V)

However if i replace the motor with an LED it works just fine Led blinks like it should

I have tried running the motor on 12V(thinking the MOSFET was dropping the voltage too much) and it still doesn't work, but if i connect Gate to +12V for a while, it like "charges" and starts turning, but a 1 sec pulse from arduino doesn't turn it on.

What am I missing? the motor alone works, MOSFET with LED works it just when I try connecting the motor in place of the LED it doesn't work? What can i try what can I test?


texts: In nut shell, how to manually program a microconntroller

texts: I know we can program and load program inside micro controller with easily available programmer with Computer based interface. But I want to know how same thing was being done in older days when No programmer or modern computer kind of interface was not available? Consider it as i am making a full project, so don't miss any steps.


texts: Till now I studied voltage feedback opamps and I know how circuits involving them are solved. What is difference between current feedback and voltage feedback amplifier? What are steps in analysis of current feedback opamps?


texts: Optotriac+triac: how do I calculate the gate resistor

texts:
I am building a small circuit to turn on/off a 200W heater. I am using a MOC3023 and a BT136. At the datasheet of the the optotriac, this circuit  is recommended:

My question is how is the 180Ohm resistor value determined. I understand that it conducts for a very short time, but not much more. Is this a valid value for both 230VAC and 12VAC? Is 1/4W resistor always suitable?


texts: What size capacitor to protect equipment from temporary voltage drop?

texts:
Or maybe a different way of doing it?

Problem:
Electrical circuit (12vDC) on my boat is supplied from the battery but on engine start there is a brief voltage drop. This doesnt affect any equipment other than the chartplotter (marine satnav) which shuts down. When re-started it takes a minute to boot up and find itself which can be a touch nervewracking at times!

Some boats deal with this by having the instrumentation powered by a separate battery to the one that is used exclusively for starting the battery, but that isn't really economically viable to retrofit

A friend has suggested that a capacitor and diode will provide adequate temporary power to maintain the voltage until the engine start is finished. The plotter draws maximum 13 watts at minimum operating volatge of 10.8 V.

Is this viable - and if so, what size Cap?

I am not too worried about load dump as there is little else to shed!

Alternatively (it has been suggested) a circuit with a small lead acid gel 12v battery that will cut in when the voltage drops and otherwise charge up when the main circuit voltage is at normal 13+V with engine running etc.


texts:
I wish to understand how a battery charger may best be designed in order to maximise the life of Lithium Ion batteries. I have specified Lithium Ion batteries as they are what is used in most laptops and in many other pieces of modern equipment.

There is much advice and opinion available but as some is contradictory it is clear that any one opinion or offered advice may be partially or largely incorrect.

I wish to understand which parameters are genuinely important, how varying them will affect battery lifetime and which of the "commonly given" advice is actually incorrect.

In orer to make the question more specific initially and to provide a finite target for answers people could consider addressing the following charging scenarios. These may not be the only options.

Force charging-Charging even after reaching 100% of Lithium Ion battery capacity.
Charging only after the battery is empty.
Charging the battery in parallel while the powered equipment is working.

How do these affect battery life?


texts:
After reading some relevant questions on ESD here, I have come up with the following approach to protect some ADC GPIO pins on my lipo battery operated board that are open to external input, thus being potential ESD targets.

I want to be able to protect against real world ESD events that could be upto 15kV or 20kV. These pins are 3.3V level, so I found found this ESD array chip that is rated to handle 30kV. It has a pF range capacitance, so that shouldn't be a problem.

I am not entirely sure how to handle the clamping voltage level. The data sheet says the DC breakdown voltage if 6.5V, which is definitely higher than the rated max on the chip. So even if the diode protects itself, my input could potentially be fried?

One of the ways to mitigate current due to high voltage I have seen is adding a series resistor after the diode stage which is usually in the sub 100ohm range. I am not sure of the math involved here in getting this resistance. I have seen notes suggesting resistance before and after the ESD diode stage. How do I decide? These two threads[one, two] provide conflicting suggestions


texts:
I have a splitter SVI Digital SV-2G Splitter (5/1000MHz) from my Comcast high speed internet self-installation kit.

I try to understand what a splitter is used for, so I found this Wikipedia article
http://en.wikipedia.org/wiki/Power_dividers_and_directional_couplers

  Power dividers (also power splitters and, when used in reverse, power
  combiners) and directional couplers are passive devices used in the
  field of radio technology. They couple a defined amount of the
  electromagnetic power in a transmission line to a port enabling the
  signal to be used in another circuit. An essential feature of
  directional couplers is that they only couple power flowing in one
  direction. Power entering the output port is not coupled to the input
  port.

I am not sure what "couple" means, so I don't quite understand the quote in order to understand the purpose of a splitter.

My guess is there is one input (the top one) and two outputs (the lower two) for the splitter in the picture.

Are the two outputs two signals that are identical to the input? In other words, is a splitter used like a switch/router for Ethernet network?

Do the cables connected to both input and outputs belong to the same type, such as belonging to coaxial cable for the splitter in the picture?

Thanks!


texts: How to solder QFN-16 with a central pad component to proto-board?

texts:
I have a QFN16 breadboard adapter and an ASXL335 chip, which I'd like to solder to it:

However, the accelerometer chip has a central pad, while board does not. This causes an annoying problem of soldering paste gathering under the pad and pushing the whole chip up (I have not expected this problem beforehand).

Is there any way to workaround this problem or is it futile? Will, for example, a small hole in the center help?

UPDATE: just to be clear. I do not need the pad as I am not concerned with thermal or physical strength issues (datasheet mentions the pad is there so accelerometer sits firmer to receive all those Gs it is supposed to measure). Also, I am using rework station fir this task.

UPDATE2: I've soldered it to the board after drilling a hole in the center and using less soldering paste. The device seems to have survived all these attempts. This time Z channel is not functioning, but X and Y do. Also, the picture was taken before adding GND-Vcc capacitor, as per datasheet.


texts: Is circuit elements' placement order in a series connection matters?

texts:
I know the current is the same in a series branch. But does it make a difference, in the operation and purpose of the circuit, if elements arrangement order changed in a series connection?

Say a circuit to filter out AC signal using an AC source with DC offset, a resistor and a capacitor. What difference there is if the arrangement of the elements is changed?

In short words using an analogy: Does the current run like a human and it reacts to each element it sees first according to what the element orders it to do and it doesn't know what the future, upcoming circuits' elements ,holds for it?

EDIT:

First output using an arrangement:

Second output using another arrangement:


texts: Analyse data discrepancies: Efficiency of wire vs current

texts:
Please help me explain why the efficiency of the wire does not follow a distinct path (ie R^2 value is low).

Graph 1 Efficiency of wire vs current:
http://postimg.org/image/p49bzm4ab/

Is is to do with non-linear relationship between resistance and efficiency (see link below)?

Graph 2: Change in temperature vs wire efficiency

http://postimg.org/image/t3oihsb6p/


texts:
I am trying to experiment with capacitor. Basically, here I am trying to replace the battery source with the capacitor when the switch is turned off.
However, my circuit doesn't illuminate the LED1. What basics I am missing here.
Is capacitor won't be charged here when the 5v is supplied. Once the switch is off shouldn't it give the power to the LED1.


texts: So I am to design a mealy state machine which detects the sequence 101. The state diagram was given, and from there I obtained the flip-flop excitation equations. I am supposed to use 2-1 multiplexers to implement the excitation equations, but I am having difficulty tying this together with T flip flops. I don't want anyone to do my assignment for me (which is why I'm only asking for theoretical answers), but I am a bit stuck as to how to approach this.


texts: Single cable for dual Ethernet plus power (PoE)

texts:
I would like to run two 100 Mbit Ethernets including a common PoE over a single cable which will be about 3-5m long. Since 100 Mbit needs 4 wires I will need 8 plus some wires for the PoE which is at least 10 or better 12 wires altogether. I wont mind having even more wires (14, 16...).

Do I need a twisted pair for such cable length? Are there any standards for cables (twisted/non-twisted) with more than 8 wires that UTP has? The environment for the setup is a passenger car.

EDIT:

The reason I want to do this is that I am synchronizing 2 devices with Ethernet and am not able to put a switch close to them so I need to run 2 Ethernet lines down to the switch. Also, the 2 devices can't do PoE by themselves - I will inject and split the power from the cable manually by hand (and lead it to DC inputs on those devices for power). The cable I intend will have 2 RJ-45 connectors on each side plus the power lines.


texts: How does the electricity "know" the ratio of the resistance in a voltage divider?

texts:
I'm having a hard time conceptualizing what/how things are working in a voltage divider setup. I've read a couple other questions/explanations where the answerer has said to "not think about it in terms of water", but it's difficult to not do so, to some extent.

What I don't get is how the electricity changes/adapts after the FIRST resistor based on the ratio between it and the SECOND resistor? I know it's in the arena of having to do with "pressures" and pipes, but if you have a resistance further up in the chain of flow, conceptually how does it matter what the resistance is further down the pipe?

And stepping outside voltage dividers (but still in the realm of the question of voltage drop and ratios) -- how/why does ALL the voltage get dropped over a resistor in a one-resistor circuit, but with 2+ resistors/loads, the electrons "know" to somehow ration the voltage drops proportionally? (Obviously I know the electrons aren't consciously working this out and making decisions). Why isn't a voltage drop static over a static resistance/load? Why does it depend on the other resistors/loads in the circuit?

(I don't mind technical, but if possible, please at least add some type of visual conception or demonstration, if you may! :) Thanks!


texts: Lead-Acid vs Lithium-Ion Rechargeable Batteries

texts:
I originally planned to use Lead-Acid rechargeable batteries in a medical device prototype, but it seems that nowadays most devices on the market are using Li-ion rechargeable batteries, which are definitely more expensive and generally have less capacity.
I also realize that many lithium-ion rechargeable batteries are labeled as smart batteries and have more communication interfaces like SMBus. My goal is to build an uninterruptible power supply with rechargeable batteries and a power management module, and wonder how much of a help those smart features would be.
Is it outdated now to use lead-acid battery in (medical) devices? I am new to the field and would love your input on this matter.


texts: What happens when an FPGA is "programmed"?

texts:
From what I understand, the process of programming an FPGA comes in two parts:

Encode the hardware description into bits that the FPGA can understand (i.e. write some HDL and compile it)
Load the compiled HDL onto the FPGA.

My question is: "What does the FPGA do with the compiled HDL?". At the moment, I think of FPGAs as "mouldable hardware", where wires and logic gates can be moulded to whatever you want. One of the nice things is that the mouldability is permanent: FPGAs can be reprogrammed.

How do FPGAs interpret compiled HDL? How is permanent mouldability achieved?


texts: Toriod, how many turns of wire to get 100 uH?

texts:
I need a toroid of 100 uH and handle 15 A.
It will be used in a MPPT wind generator charge controller of 48 volt DC.
I have a yellow iron core toroid ring, 23 mm outer diameter, 13 mm inner diameter and 10 mm high. I have 1 mm enameled copper wire.
Can somebody please tell me how many turns it would require?


texts: how to design a low pass filter for square waveform

texts:
I have square wave signal of 100KHz with few high frequency ringing from 555 timer.when i tried to use a 100KHz first order rc low pass filter,i got a sawtooth waveform because the 100KHz square will have harmonics of sine of higher frequency which got cut down.
The formula available in internet for low pass is valid for sine wave alone.So I want to know if there is any formula for low pass filter for square input.
To generate a 100KHz square wave of 20Vpp which is best method?

555 timer and amplify it using amplifier
or

directly use a amplifier as oscillator


texts: How to interface a RPi Pico to DMX / RDM

texts:
Years ago, I was looking at creating a stage DMX controller using AVR. Time moved on and the Raspberry Pi Pico has now been released. I'd like to revisit the project using a Raspberry Pi Pico, which has got me excited about hardware again. I come from a software background and am confident I can do that, but am not at all confident with hardware (although I find circuit design very interesting).
This is my first attempt, adapted from my AVR design which was in turn adapted from an open source project online. Does this look like it should work as far as electrical compatibility with DMX/ RDM?

I'm aware about galvanic isolation being required across the optoisolators and obviously haven't shown how the Pico is wired to anything other than the RS485 portion of my project. I've also switched out a Max485 for a 3483 (shown as a part label) to keep it all at 3.3v. It still shows in Fritzing as a 485...
Although I'm very excited about the possibility of working on this, it's purely hobby, I have no timescale and just want to learn, so any criticism is appreciated.


texts: Buck regulator output capacitor via current sharing - whether via symmetry matters

texts:
I have a question regarding Buck regulator output capacitors via current sharing.
we have 12V to 1V @ 35A regulator design, which uses 7x100uF,5x150uF bulk capacitors, which are placed sequentially few on TOP and remaining are ON BOT layers with vias connecting all capacitors from TOP to BOT and Internal shape which carries the current to load.
When we have simulated IR drop, Plane drop, power density, via current density using POWER DC we see most of the current is handled by via which is very close to first Output capacitor. Actually all vias should share the current equally to internal planes.
Is this the real scenario, whether all the via's near the output capacitors in the generating shape won't share current equally.
If we need to share current equally, what needs to be done.
I see in Evaluation board layout the vias are arranged very symmetrically with equal vertical & Horizontal spacings - maintaining such a symmetry is required?
I have our report for reference and Vendor EVB reference layout for comparison.
Here, are my questions.

In regulators layout's Output capacitors will be arranged sequentially few on TOP and few on BOTTOM layers. The ripple current shared by these capacitors whether varies based on Capacitor relative position from Inductor, How much will be the ripple share between TOP & BOTTOM side capacitors.

Whether BOTTOM capacitors will conduct any ripple current compared to TOP capacitors.

We have output shape starting from Inductor to some distance to connect all Output capacitors on TOP & BOT. This shape has via's which are used to share current between TOP to Internal Power planes. Whether these via's needs to have symmetry to share current equally.


texts: How is generator output voltage kept constant?

texts: I read that if we increase the load at the terminals of a generator, the current driven from the generator will increase which will slow down the generator. But for this to happen the generator should output constant voltage. How does it achieved? And if there is no voltage regulation (just a generator and we increase the load step by step), what would happen?


texts:
I need to drive 2 high power LEDs (1 watt each) from a 5 volt supply. My current solution is to use a separate current source for each LED, each of which is made of a mosfet and bjt. This is only as efficient as a series resistor, and the LEDs each have a 2.7V drop and 350mA draw, so with a 3V supply it's around 75% efficient which is not terrible. However, with a 5V supply this drops to around 50%. An additional requirement is that the whole circuit be small and light enough to wear.

I need a new solution which is at least 80% efficient when operating from a 5V supply. The trouble is, almost all the driver chips I can find are designed for driving long series strings of LEDs from higher supply voltages. Can anyone recommend a chip or constant current source that might do the job?


texts: Why such large error on Tinkercad opAmp in my setup?

texts:
I'm working on a device that would restore voltage on my collection of used 18650 cells. The theory is that they need to be charged extremely slowly with constant current of max 100mA until they are around 3V. This can take above 24 hours. To make the device cheaper I decided to create 40mA-50mA constant current source using just NE5532 opAmp it should not have any problems delivering that amount as it can provide up to 60mA.

I used Tinkercad for simulation and divided the device into two parts. On the left there is a simple DAC design using 4.7kOhm resistor, 10uF capacitor and opAmp in buffer configuration. This part works without a problem and is easily controlled by analogWrite command.

Second part is the charging circuit. There is a 1 Ohm resistor to detect voltage drop, opAmp in 100x amplifier configuration (with 2 x 10kOhm and 2 x 1MOhm resistors) with a 10uF capacitor to smooth out the error. There is a diode to prevent discharge of the battery before voltage in the device is high enough to charge it (broken cell voltage can be between 0.5V and 2.5V so a slow ramping up is required)

Everything is OK in simulation when I try to keep amperage at 10mA level. (The 18650 cell is represented as 1.5V battery) As you can see 12mA of voltage to flow into device and the amplifier turns that into 1.2V that is read by Arduino, and it stops ramping up the voltage.

But as soon as I try to set amperage to 20mA or higher this happens.

The system stabilizes at 31mA and 2V from the opAmp. At 31mA opAmp should return 3.1V. the 2V should correspond with 20mA of charge current.

The question is.
Can I somehow decrease the error in 100x amplifier circuit?
Is it just a behavior of the simulator, or real NE5532 will have the same issue?
Should I simply fix the non linearity in the Arduino code?

Code I used:

float INITIAL_VOLTAGE_V = 1.90;
float CHARGE_AMPERAGE_A = 0.02;

int v = 0;
int a = 0;

void setup()
{
  pinMode(A0, OUTPUT);
  pinMode(11, OUTPUT);

  v = map(INITIAL_VOLTAGE_V * 100, 0,500,0,255);
  a = map(CHARGE_AMPERAGE_A * 100, 0,5,0,1024);

  Serial.begin(9600);

  analogWrite(11, v);
  delay(1000);
}

void loop()
{
  int x = analogRead(A0);

  if (x < a)
    v += 1;

  if (v > 255)
    v = 255;

  analogWrite(11, v);

  Serial.print(x);
  Serial.print("->");
  Serial.println(v);

  delay(500);
}

EDIT
I prepared the device schema.

After some simulation I found out that the issue is in the voltages I put into the opAmp. Tinkercad uses LM741 in it's opAmp, and I wanted to use NE5532. they both are extremely nonlinear close (around 1V) to the Vcc- and Vcc and their values are completely unreliable.

It was suggested to me to use LM358 for the feedback loop.


texts: What is the best way to tap 12v from a 6x6v battery array for intermittent loads?

texts:
Greetings beloved comrades,
I recently acquired a 36v golf cart that has 6 6v batteries in series.  The existing 12v accessories, mainly lights, are powered by a separate series connection to 2 of the 6v batteries.
I don't like tapping only 2 of the batteries, since prolonged usage will imbalance the batteries and possibly require individual charging.
My question is:  Can I wire 3 12v circuits in parallel from the 6 batteries for an always active supply, or would it be better to add a separate switched 36v circuit and a buck converter to get 12v?
I would prefer the first solution just to avoid buying a chunky switch and converter, but if the latter is better is for efficiency/battery life, I'll go that direction.


texts:
I have an ADC (ADS1672 datasheet) (20MHz) with serial interface and xilinx spartan 3 XC3S400-208 (50MHz)
In its datasheet to data retrieval comes this:

for that I implemented this code:
inputs and outputs:
input wire DRDY;
input DOUT;
input OTRD;
input wire SCLK;
output CS_ADS;
output reg START;
output [1:0]DRATE;
output FPATH;
output LL_CONFIG;
output LVDS;
output SCLK_SEL;
output PDWN;

reg DRDY1=0,DRDY0=0;
reg [4:0] ADS_bit=0;
reg [23:0] ADS_buff=24'b0000_0000_0000_0000_0000_0000;
reg [23:0] ADS_buff_last=24'b0000_0000_0000_0000_0000_0000;
reg onetime =1'b1;

parameters:
parameter PWRDWN=1'b0, PWRUP=1'b1 , FPATH_LowLatency=1'b1 , FPATH_WideBand=1'b0 , LL_CONFIG_SingleCycle=1'b0 , LL_CONFIG_FastResponse=1'b1;
parameter DRATE_00=2'b00 ,DRATE_01=2'b01 , DRATE_10=2'b10 , DRATE_11=2'b11, SCLK_SEL_Internal=1'b0 , SCLK_SEL_External=1'b1 , LVDS_LVDS=1'b0 ,LVDS_CMOS=1'b1;

Configuration:
assign DRATE            = DRATE_00;
assign FPATH            = FPATH_LowLatency;
assign LL_CONFIG        = LL_CONFIG_SingleCycle;
assign LVDS             = CMOS;
assign SCLK_SEL         = SCLK_SEL_Internal;
assign PDWN             = PWRUP;
assign CS_ADS           = 1'b0;
assign START            = 1'b1;

Data Retrieval segment:
always @(posedge SCLK)
begin
    START<=1'b1;     //hold start hi

    DRDY1   <=  DRDY;
    DRDY0   <=  DRDY1;

    if((DRDY1==1) && (DRDY0==0))     //rising edge of DRDY to start retrieval
        begin
            ADS_buff[23]<=DOUT;    //First bit is comes with posedge DRDY
            ADS_bit<=5'd23;    //bit index Counter
            onetime<=1'b0;
        end
    else if(ADS_bit==5'b00000 && onetime==1'b0)
        begin
            ADS_buff_last<=ADS_buff[23:0];    //Update last final buffer value
            ADS_buff<=24'b0;     //flush buffer
            onetime<=1'b1;     // to prevent run this again
        end

    if(ADS_bit!=5'b00000)
        begin
            ADS_buff[ADS_bit-1]<=DOUT;     //get data
            ADS_bit<=ADS_bit-1'b1;     //count down (MSB to LSB)
        end
end

when i set SCLK internally (i means by SCLK_SEL=0,make ads1672 to generate it), i never get right value(values are not zero)
but when i set it externally (and generate SCLK from FPGA) by same Data Retrieval some times i get right value and some times zero!!
just difference is frequency, when it is externally it is 12.5 MHz.
and when it's internally it is 19.9 MHz.
SCLK Generator (for when it is externally):
always @(posedge main_clk)
begin
    SCLK_cnt <= SCLK_cnt + 8'd1;
    if(SCLK_cnt>=(8'd4-1))       //divide per 4(50MHz/4=12.5MHz)
        SCLK_cnt <= 8'd0;
end
assign SCLK = (SCLK_cnt<8'4/2)?1'b0:1'b1;

any body have idea why this happen?


texts: IPC-7351C polarization mark in real-life?

texts:
I know IPC-7351C is not released and probably won't be for... forever? The draft version of IPC-7351C differ from what's out there in the wild in many ways. For example, the draft uses a bar instead of a dot to indicate pin 1.

Has anyone seen any PCB with IPC-7351C land patterns in the wild (any photo, maybe)? Does the new silk screen cause any confusion at PCB assembly manufacturers?


texts: How can I provide a 12v no-load output with a 5v source?

texts: I have an aftermarket stereo that has an input to toggle the reverse camera display. When I apply +12v to the input it switches to the video input. This input is not used to power the camera or anything else - so it doesn't really carry a load - guessing it's just connected to a comparator. I've looked at relays (seem like overkill) and BJTs. What's the simplest way to provide +12v to this type of no-load application using the +5v output pin on an Arduino as the source?


texts: Ideal Switching Signal for a Featherwing power Relay board

texts:
The featherwing power relay board is a simple transistor controlled electromechanical relay.

The power supplied is 3.3V and it requires a signal to switch.

Looking at the data sheet, the signal voltage is not specified.

https://cdn-learn.adafruit.com/downloads/pdf/adafruit-power-relay-featherwing.pdf

From the schematic, any voltage above 0.7V should switch the switch.  Is there an ideal safe switching voltage and how is it calculated or is it rule of thumb, i.e same as collector or random sensible value?


texts: How to reduce transformer secondary voltage?

texts:
Trying to make a bench power supply. What would be a cheap easy way to reduce voltage (to protect the series pass transistor)? 3 Amp transformer has these terminals 12-6-0-6-12. No load voltage is 33 VAC (47 Vpeak DC). Primary taps are 0 and 230V. I came up with these options, and can't decide between them.

Couple of 5A rated household AC staircase switches between the 6V and 12V terminals. Cheap and easy, but manual control. Series transistor needs thermal protection against "accidents" (including output short circuits).
Couple of relay tap changer between 6V and 12V terminals. Maybe cheap, not easy. Needs zero crossover, Schmitt trigger control circuit. Relays will probably need eventual replacement.
Triac tap changer. Possibly more complex than above, and may need more parts list. Triac has voltage drop.
Triac (or SCR) to chop AC waveform on secondary side. I have no clue where to begin. Have seen the old HP manuals. But if bad comes to worse, I am ready to pop in an Atmega88.
60V buck converter. Where to get a reliable one? Is switching noise an issue?
Series pass regulator to reduce voltage to below 40V (max dissipation 2W @ 750mA), then a 40V buck converter, and then a series pass linear regulator? This is becoming confusing, and wasting a lot of volts. Will also have switching noise.
Roll my own buck converter???

I'm leaning towards #1 right now (couple of $0.15 switches). Power supply will be used for analog work mostly (test op amps and audio amplifiers etc and other hobby electronics stuff). Is the inability to smoothly change voltage from zero to 30V or 40V, a likely hindrance? I don't think I've ever had to change voltage by more than ±3V for anything (usually characterizing LED, or optimizing current draw for small projects). Why would someone want to smoothly change voltage all the way from 0 to 30V? Only convenience, or something more?

I'm hoping this works out, as transformers seem to cost less than a third of a good 36V SMPS (same wattage). Only problem with transformers is the >40V at no load, and then it goes downhill.

So, any suggestions?


texts: Why is the microphone output level not proportional to the sound level?

texts:
I set up a system to measure the sound pressure level in a location. This consists of  a Knowles SPU0410LR5H-QB microphone connected to the codec SGTL5000, which is connected to the micro-controller over I2S.

The SGTL5000 codec microphone input has a 30dB gain before the ADC. I calculate the SPL by sampling the I2S data over 1 second and getting the logarithmic of the RMS value. I took some measurements with the device and a commercial sound level meter and another I2S MEMS microphone using the same calculation method.

Although the measurement method wasn't very scientific, it's clear that there's a deviation from the 45° line indicating that the microphone output level(mV) is not proportional to the sound pressure (Pa).

This is not the result of any Automatic Volume Control by the CODEC by feeding the mic input from a signal generator. (SGTL5000 has AVC but it's turned off in my case).


texts: Logisim: timing problems setting register

texts:
I'm having some problems understanding the timing behaviors I observe in Logisim. I've isolated some cases which illustrate the problem.

Say I have a register (1-bit, to keep it simple), which is being fed a logical 1 on its input D. Upon the clock the register is set to 1, as expected:

For this to work, the D input must already be receiving the logical 1 when the clock signal arrives. If, by using an N-type transistor, we only let the data line be high when the clock is high, then the register will no longer be correctly set, due to the delay introduced by the transistor:

Indeed, if we add two NOT gates to the clock line that is sufficient to delay the clock signal  (relative to the data line) and make sure the D input receives the logical 1 on time again, allowing the register to be correctly set:

Of course, that is a horrible kludge and cannot be relied upon, since gate timings can vary due to component tolerances and other reasons. Still, so far so good, all of these behaviors made sense to me. What I don't understand is the following two cases.

I thought: if I put an N-type transistor in the clock line, to only let the clock signal pass after the data signal has passed its respective transistor, that should synchronize everything up. But it doesn't work:

It also doesn't work with a "Controlled Buffer" component:

Even more surprisingly, if I use a P-type transistor then the register is set, even though the register's clock input is floating, instead of set to high:

Can you please explain me these last two behaviors?


texts: Protecting a 3.3V board against a 5V programmer

texts:
I'm designing a home automation board with ATmega328. For programming it I'm exposing the appropriate pins via the AVR ISP interface. Now some ICs of the board allow only up to 3.5V power. What are recommended ways of preventing damage when using a 5V programmer? I have several ideas, neither of them perfect:

Always use a modified 3.3V programmer. But it's easy to forget and damage the board by using a standard 5V one.

Use a jumper to connect the MCU's VCC to the ISP instead of the board's power supply. So far this seems to me as the best solution, as the visual presence of the jumper also acts as a reminder.

Still, there are possible issues:

If the jumper isn't switched before programming, the MCU will be unpowered, while the programmer will attempt to communicate with it's data lines. That can potentially damage the MCU.
I'm not very happy with routing power to anything via jumpers.

Incorporate a level-shifter and always power the board before programming. This makes the design more complicated, although it's probably the cleanest solution.

Which of them, or perhaps yet another, would be recommended?


texts: Using 24 bit audio DAC for low frequency/DC output?

texts: I am looking for a high precision DAC for an output to act as a control element in a PID loop (running about 100Hz). Now, devices such as the AD5791 can provide a true 20 bit output with remarkable precision. How do 24 bit audio DACs (much cheaper) fare in such applications?


texts: FPGA Synchronized Digit Counter goes Asynchronous!

texts:
I'm trying to implement one digit counter from 0 to 9 using an FPGA board. The digit is incremented when the signal "pulse" is set.
The "pulse" signal is set every fixed number N of clock cycles. The clock frequency is 5 MHz.
However the counter jumps inconsistently depending on the "pulse" period. For example when it's set to 1000000, the
counter works fine and the digit is incremented every 1/5 of a second. When the period is different, it does not behave as expected.
Even if the period is set longer, every 5000000 clock cycles, it jumps from 0 to 1 to 0..., the increment is 10!

Here's the VHDL code that increments the counter based on the pulse.

process(clk, reset)
begin
    if (reset = '1') then
        digit_reg <= (others => '0');
    elsif rising_edge(clk) then
        digit_reg <= next_digit;
    end if;
end process;

process(pulse, digit_reg)
begin
    if (pulse = '1') then
        if (digit_reg >= 9) then
            next_digit <= (others => '0');
        else
            next_digit <= digit_reg + 1;
        end if;
    end if;
end process;

Any idea what the problem might be?

Thanks.


texts:
I've been working with electronics for a while now, and I understand how to work with/account for voltage drop. But I'm still mystified as to how it works, particularly with components in series. Say I have two small incandescent lamps in series hooked up to a power supply. Through what physical mechanism is the voltage spread evenly over both lamps, resulting in both lamps running dim, instead of the first lamp consuming all the power and running at full brightness and the second running dark?

EDIT: It seems that people were getting hung up on the fact that I was using LEDs in my example and were focusing on whether the LEDs would run at all with lower-than-rated voltage. This wasn't my intention - I am focused on the phenomenon that both drop an equal amount of voltage instead of the lead LED dropping more voltage than the second LED. As a result I changed the example to incandescent lamps which show a closer-to-linear relation between voltage and brightness.


texts: Why the port type of this module default to 'var'?

texts:
In "IEEE Std 1800-2012 SystemVerilog", p. 668, I find this:

module mh11(output integer x); // output var integer x

I wonder why it is default to 'var' but not 'net'? Which rule defines it, or itself just is the rule?


texts: I would like to flash a new firmware on my STM8L15xC8. I have ST Visual Programmer (STVP) installed and can successfully flash the MCU of the STM8 Discovery board. Now, I setup the STM8 Discovery board to flash external applications. However, when I want to write to the MCU my hex file, I get the error The device is protected. What should I do?


texts:
I was solving this exercise where I have to find the current through each of the circuit branches. Sorry if the image is a bit confusing but after determining the current I I used the current divider formula to find the current in each of the branches. Apparently I got the wrong answer but I can't understand what I have done wrong.

(Original)


texts:
I am kinda new to electronics design and I am having some trouble with the Analog Devices LT319AN chip. I am trying to do simple 250KHz PWM which worked on a lesser LM393 chip in this exact setup. I know I am probably missing something simple due to the lack of some basic knowledge, any help would be much appreciated! Anyway I have added a schematic diagram and oscilloscope pictures so you can see what I am dealing with.

Edit:

Forgot the Schematic!

Edit #2:

Thank you @DKNguyen! Per your input I added 10k OHM resistors between +5vDC and ground to bias the input's and this is the output am now getting:

https://youtu.be/hdRFULSaPc0

Thank you for your help!


texts:
With STM32-H407 (STM32F407ZG), I am trying to make rectangular waveform output like;

---_  _ ---_ _ _ _ _ --- _ _ ---_ _ _ _ _ --- _ _ ---_ _ _ _ _ _

With numbers

---_ _  ---_ _ _ _ _ _ is 125us (0.000125s or 8kHz) long and it repeats.

--- is 3.5MHz or 0.2857 us long.
In other words, ---_ _ --- must be 0.2857 us + 0.2857 us + 0.2857 us long.

To summarize, 3.5MHz pulse pops twice every 8kHz.

What has been tried are  1) PWM + Timer.  Failed to stop the 3.5MHz pulses after two cycles.  2) Timer + Timer.  Timers did not work together.

How would you code this?  Can you give some simple examples?

Thanks.


texts:
I have a 12 V load that works by connecting an adapter from the AC socket and this adapter output 12v to the load. I decided to make a 12 v battery that can charged and the feed this load , all the work is done perfectly but the problem is that the battery when connected to the load its output voltage varies from 12 til 0 and the increase and continues like that, which may damage my load, so i think i should use a voltage regulator that outputs 12 v but it will work? if yes what kind of regulators i can buy??
Note : the load takes 1.2 A and the batteries are 4000 mAh


texts:
Say I have some audio device with the following absolute frequency response:

I want to shift the curve up, so that the 1kHz point is the 0dB point, and everything else is relative to this point. Am I correct, that I cannot simply add 0.35dB to the entire curve, but need to compute back to Vout from:

dB = 20log(Vout/Vin)

add whatever voltage is necessary to the initial Vout to make the 1kHz point 0dB (we'll call this added voltage "curve offset voltage"), then offset all of the Vout values across the measurement range with that same curve offset voltage to obtain the frequency response relative to 1kHz?

Initially I just added +0.35dB to the entire curve but after thinking about it, I don't think that makes sense, since it would be changing the output magnitudes at each frequency exponentially.


texts:
this is a closed loop feed back circuit in order to make a precise current source.

my first question is about R23. haw much it should be?  i think it is
better to just mounted a 0R resistor and reduce the error of voltage drop on this resistor due to Ib of op amp. but i'm not sure about this. i would be grateful for any advise.

my second question is about R15 and C11. these are not mounted . should i keep them not mounted?


texts: Connections for Panel Mount 12VDC Power Supply

texts:
I'm using a 12V Panel Mount Power Supply, taking a 110/220VAC input and giving a 12V/5V DC output.

What is the best practice for connecting this power supply to the AC mains?

And how should this unit be mounted for use with a PCB, ie: do you mount this directly to the PCB, or is there a special mounting platform that we can mount both the PCB and this power supply to?


texts: How can I minimise the power consumption of this crossover clipping circuit?

texts:
I am trying to produce a circuit that produces crossover clipping distortion for musical purposes (to sound like a crappy old transistor radio). The problem I am running into (among a few, but to limit the scope) is that to observe clipping distortion, the circuit draws a ton of current to drive the BJTs and load. My intention for the circuit is to run it in a guitar pedal off a 9 V battery (though boosted to 18 V for op-amp headroom), but this seems implausible with the current design.

Is there an efficient way to emulate crossover distortion?

Circuit

The current circuit used is a simplistic Class-B amplifier. As R4 increase the bias improves, moving it towards Class-AB and reducing the distortion. This will be parameterised with a potentiometer so that musicians can dial in the amount.

simulate this circuit – Schematic created using CircuitLab

Here is an example output:

Design constraints

The three design constraints I am dealing with are:

Keeping resistances relatively high so that the highpass filters formed with C1 and C2 keep a low cutoff frequency, allowing wide-band signals to pass through. Ideally the cutoffs should be beneath 20 Hz.
R3 and R2 can be left equal for simplicity.
The ratio between R3/R2 and R4 is one factor that determines the amount of crossover clipping
The second clipping factor is the load, R1, as it decreases the distortion increases.

Problem

Overall the circuit draws nearly 10 mA of current. For comparison, I have two Sallen-Key op-amp filters before it which each draw less than 1 mA each (ideal LTspice simulation, mostly quiescent). Do I just have to suck it up and suggest that users keep a draw full of batteries to use? (Or more likely a wall wart).


texts: How to get rid of this reflection on falling edge of i2c SDA line?

texts:
This is the scopeshot of the falling edge:

How to get rid of the reflections on the falling edge of this SDA line?


texts: AC 220v Single Phase Motor Control using relay

texts:
i've been looking for a diagram for motor control using arduino and relays, and i only found tutorials using DC motors. i know you can use a contractor but for my project i want to be able to use Bluetooth and buttons as well as an LCD display, anyway i've already got everything setup and working, i only got a few questions.

1.) Would it kill a relay if i use a 1HP 220v 8a single phase motor to drive a bridge forward,(it's about 1200 lbs not that sure yet though hehe)

2.) is there a diagram for forward reverse using a 2 channel relay?


texts: I'm working with a few BGA chips of a very fine pitch 0.5mm even smaller sometimes. What is the practices for being able to essentially breakout all the connections from these chips? I've just been dead bugging them for now but that's a very time consuming process and it has caused damage to a few of my chips before.


texts: How to switch an AC signal on and off with a BJT?

texts:
I built a phase shift oscillator and now I want to turn the output of the oscillator on and off using a pulse, generated with the NE555 IC.

I am trying to do this using a BJT. I connected the oscillator output as Vcc and the pulse to Vb.

I got more or less the short sinusoidal pulse that I wanted but as you can see the output only follows Vcc for values larger than -Vce. I have only used BJT's with DC values for VCC so I am not really sure how to redesign this circuit in order to get the output to follow Vcc for larger negative values.

So my questions are:

1) Is it possible to get what I want using a BJT?

2) If it is possible how should I redesign my circuit?

UPDATE:
This is the new circuit I am using:


texts:
can you help me with the basic comprehension of this Voltage Controlled Oscillator scheme (it was used in a PLL)?

I do not understand why there are two varactors instead of one, and the role of the variable capacitance CT.

Reference: http://mwl.diet.uniroma1.it/people/pisa/RFELSYS/L03_VCO_PLL_Phase%20noise.pdf


texts:
I am new to this forum and also knew to the program LTspice. I want to create a IRF530 VMOS component and have found a model for it;
.model IRF530 VDMOS(Rg=3 Vto=4 Rd=50m Rs=12m Rb=60m Kp=5 lambda=.01 Cgdmax=1n Cgdmin=.26n Cgs=.2n Cjo=.4n Is=52p mfg=International_Rectifier Vds=100 Ron=160m Qg=26n)
I have managed to find a page that describes all the abbreviations above (http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_6.htm). I have however no idea about how to create this IRF530 VDMOS. I appreciate any help and if there is a way around it :)


texts: I can't get the Assura system to do simulation of the schematic versus layout. I followed all the steps and inserted all the libraries according to the tutorials and what it is to prescribe writing and I can't simulate someone could give guidance. One of the errors says that the pins are not connected in the layout, but they are connected, yes, has anyone been there?


texts: Measuring noise on DC rails with active probe

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I have a Tektronix P6245 active probe (allows only DC input) and wish to use it to see noise on various power supply rails.  I've done this already on a +3.3V rail, and can get sufficient DC offset on the scope (Tek TDS744a) to see millivolts.

However, it gets tricky with higher voltages (within the probe limits).  For example, a +12V DC rail is tough.  Bringing the vertical resolution to a level that will provide meaningful data is simply not possible.

I'm considering a dc blocking capacitor between the probe and the rail under test.  Is this a reasonable option?  Any suggestions for best way to do this?


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Question:Find the Vo voltage using the node voltages method.Thanks in advance.

I chose the following node as the reference node.I created the equations but i couldn't destroy the i delta.Because it was on the 10V source.I could easily write the delta if resistance but I can not write now.


texts: Simple voltage/wattage/resistor question about night light

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By chance, I came across my childhood night light.  Plugged it in and low and behold, 30+ years old, but it still works but the bulb is very dim.  I decided a fun little project would be to replace bulb appropriately.  It's a very simple light, just an opaque thick blue plastic dinosaur that is illuminated from behind with a bulb wired directly to plug.  I have experience with some soldering and arduino work but have very little working knowledge of electricity in regards to voltage, watts, amperage and how they all play together.

The plug of the night light had a black plastic cap with specifications stating 1/3w - 125v (pictured).  The actual assembly (pictured) has what I believe to be a 30k resistor with a 5% tolerance judging from the bands (orange, black, orange, gold) and a calculator website (can't post the link as already have two links in this post which is the max for less than 10 rep).

I went to Lowe's and figured it best to go with the lowest wattage I could find - a small 12v 10w halogen.  I also picked up a 120v 2w LED but the housing is too big so that won't work regardless.  And after reading up more about all of this that 12v halogen bulb won't do in a household plug either, correct?

Long story short, what's a good small bulb and resistor to solder to the plug to make this functional again?  I suspect maybe a 1w LED bulb?  Would that still be in an appropriate range for the current 30k resistor in place?

Thanks for any help and sorry I know this is pretty simple stuff I just don't want to set my house on fire.


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I have been assigned a control systems problem, where I am supposed to stabilize a system using a controller technique from the frequency domain. When I implemented the system on Matlab and calculated the phase margin of the system it turned out to be infinite. I am not exactly sure what that means.
Can someone tell me what exactly does it mean that the phase margin comes out infinite, and how can such a system be stabilised?
This is my code:
clc
clear all
close all
num=[1];
den=[1 0 -9];
sys=tf(num,den);
bode(sys);
[Gm,Pm,wcp,wcg]=margin(num,den)


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I am a 14 year old electronics noob. I am mostly a programmer and mechanical designer. I have been working on a robot which needs around 4 amps of current. I am thinking about using a simple 5V 4A AC to DC adapter but they seem to be a pain to connect to a PCB. Especially since many mounts cannot even work with 4 Amps. I am trying to power 4 micro servos.
EDIT: How can I power this?
Edit 2: here is an image of my planned circuit:

Edit 3: There is a slight error in the circuit diagram in servo 2: pin 2 of that is supposed to be connected to pin 6 of the Arduino.


texts: Energy stored and Lagging of Current In a Inductive Circuit

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In a purely Inductive AC Circuit, the voltage/emf Leads the current in phase by 90.
The graph between Voltage and Current is given below:

Now can anyone here please tell me in a more intuitive way how the current is varies sinosuidally with emf in every quarter of cycle?
Also how Inductor stores Energy in its Magnetic Field?

I don't need any Mathematical Explanation.
Thanks...


texts: (idle) energy consumption motored valve vs solenoid valve?

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For my use case, shutting off/turning on a water flow of to my heading system I can buy two different type of valves, mototed ball valves and solenoid valves. Most of the time the valve (either option) is not doing anything but is changed (open -> closed / closed -> open) maybe 4 times a day.

My question is about the (idle) energy consumption while there is not action happening. Does a solenoid not work by constantly iducing a magnetic field, hence consuming energy?
Would a servo motored ball valve be better then, or is either case using energy in idle state (at least either for open or for closed?)

To give an example of a solenoid I have been looking at is this:
https://www.amazon.co.uk/BACOENG-DC12V-Stainless-Electric-Solenoid/dp/B01054IED0

  Suitable Media: Water Oil Air
  Valve Type:Direct Acting, Wet Armature
  Operation Mode:Normally Closed
  Plunger Tip:NBR
  Working Pressure:0-1.0Mpa
  Fluid Temperature: 23-176 F
  Operating Viscosity: Under 20CST
  Installation: Fluid direction should be as the arrow shows


texts:
let's consider a fractional frequency divider, which is defined (wikipedia) in the following way:

  A fractional-n frequency synthesizer can be constructed using two integer dividers, a divide-by-n and a divide-by-(n + 1) frequency divider. With a modulus controller, n is toggled between the two values so that the VCO alternates between one locked frequency and the other. The VCO stabilizes at a frequency that is the time average of the two locked frequencies. By varying the percentage of time the frequency divider spends at the two divider values, the frequency of the locked VCO can be selected with very fine granularity.

So, if I have a signal of frequency f0, and for instance I want to get a signal of frequency f0/(2.5), I may use it and divide half of the time by 2 and the other half by 3.

But I do not understand how can I get a signal with frequency f0/2.5 in that way. I think I get: a signal of f0/2, then a signal of f0/3, then a signal of f0/2 etc. Ok, the average frequency is f0/2.5, but the instant frequency not (and I'd say that it is the instant frequency which is important in most of the circuits).

The text speaks about VCO so I think it means that this kind of divider should be inserted in a PLL. But also in this situation I do not understand how can I get an instant frequency equal to f0/2.5.