texts: Arduino Uno only lighting up 3 of 8 LEDs in WS2812 Strip

texts:
I have an Arduino UNO driving a 8 x WS2812 strip but only the rightmost three of the strip are lighting up. The UNO should be able to deliver current for more than 3 WS2812s. That previous link states a 200mA max on Vcc so I should be able to see ~6-8 of the LEDS depending on the current draw. I was reading ~45-55mA when displaying some basic RGB colors on the strip and was reading 115-120mA when all 3 were being driven to provide a white hue (i.e. all 3 internal LEDS to the WS2812 on). This is a little lower than what the spec sheet states as they said ~50-60mA for all three internal LEDs on to produce white.

I'm powering from the USB port of a laptop, but have also used a 5V 1A USB wall wart with no change in the number of WS2812s lighting up.

I can add in a standalone WS2812 to the circuit with no problems, so I'm unclear as to why the 8 x WS2812 is only partially lit.  I've tried a second 8 x WS2812 and it behaves the same way, only lighting 3/8 of the LEDs. I've even soldered on Vcc + GND to the other end of the 8 X WS2812.

I have a small resistor on the data line per the Adafruit best practices.  The 8 x WS2182 has built in power protection so it doesn't need a cap in front of it and I'm just being lazy for the single WS2812.

As you can see in the photo I am only partially lighting up the 8 x WS2812.  The stand alone WS2812 works fine and removing it doesn't allow for another one on the 8 x to light up. The piece of paper is just there to get a decent picture as the LEDs are bright such that it is hard to take a picture that isn't overexposed.

The schematic is basically what I have.  There wasn't an 8 x WS2812 in Fritzing but it basically would just be a drop in replacement for the single WS2812.  I am using the pot as an input that the Arduino reads and based on that reading changes the color that is fed to the WS2812.
I realize that in the image above, I'm using an Arduino UNO and in the schematic I'm using a Nano.


texts: Given a CAN bus with one master and 4 motor drivers, is there a way to measure the time between sending a command from the master (e.g. PC or PLC) and the execution of the said command (e.g. the motor moving)?


texts: Modified PWM for faster transient response

texts:
My heating controller "Thermostat" uses PWM of the water valve to control the heating power to the room. It has a fixed cycle length and varies the proportion of on-time to manage the temperature, using a PI controller.
I've slowed the PWM down to reduce wear and tear on the valve. With a 30-minute period the room fluctuates only 0.2 degrees over the cycle.
However it is slow to respond to sudden changes in temperature or setpoint, because of the long cycle. Ideally it would immediately start (or stop) heating when the error is greater than 1 degree. Possible solutions could include:

Shorter PWM cycle (but most of the time this is a waste)
Breaking out of the PI-PWM control into a special fast-ramp mode when a major disturbance is detected

Is there a type of PI-followed-by-PWM that encapsulates this completely, in a single algorithm?


texts:
I am trying to build some sort of electric cart, to help me push something. The cart would have to push about 120-150 pounds. It wouldn't have to completely push the whole thing, just assist me with pushing it at a slow speed (5-7 mph). My primary objective is to keep costs down. It needs to be battery powered. There's not much else I can think to clarify, so I will say any extra information if requested.

I have done a little bit of research, but I am new in this field, and help would be nice. I was thinking about using this motor, but as I said, I don't know too much. Maybe a battery like this? I also don't really know what speed controller would be nice.

Any help would be appriciated!


texts: How can I view, debug, or analyze data being input to my FPGA?

texts:
I'm working with a Xilinx Spartan6 on Digilent's Nexys3 board.

I've also purchased their PmodMIC so I can try to get some audio data onto my board to perform some signal processing.

The PmodMIC has a simple SPI connection, and is supposed to serially output 12 samples per "run" that get shifted into a 12-bit vector inside the PmodMIC VHDL module.

I have created some top-level code and supporting code that I think might be working, but I find myself completely lost when I ask myself - "How do I verify I'm getting correct data, or any good data at all for that matter?"

I decided to map 8 of the 12 bits in the output vector to the LEDs on the board so I could see something at all.  When I press my button mapped to start the conversion process, I can even see which LEDs are lit occasionally change and move around, but I know this is essentially useless for anything meaningful.

At this point, I'm entirely clueless.  If only there was a way to serially output data back over USB to the PC, or freeze the FPGA's state and examine the contents of its memory after storing some samples there.  If methods like this do exist, I certainly don't know about any of them.

Logic Analyzer

I bought the Analog Discovery (another Digilent product) and tried to view the serial data coming from the PmodMIC to the FPGA. I simply routed the serial data to another unused output on the JA bank and hooked up the analyzer, but my results have been pretty poor.

I am sure much of this has to do with my inexperience with the device (I can't even figure out how to control its sample rate).

In any case though, my ultimate question is a bit more broad, which is:

What tools, methods, or processes exist to view, debug, or analyze data on an FPGA?


texts:
What is the need for an external watchdog timer for a microcontroller?

Most of the microcontrollers are designed with an internal watchdog timer. However, in some of the circuits they are using an external watchdog timer (such as PIC16F1824).


texts: Transformer fuse for primary coil. 240V with 16VA

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So I know it may be a basic question but hear me out. These are the specs for the transformer I would like to buy.

To add a fuse to the primary coil I would do 16VA/240V which gives 0.06A. Does that mean I need to get a 100mA fuse?


texts:
Please look at the picture for this description.
I have a problem with writing verilog for the following logic:
Consider clk and R3 are input signals & out is the output signal. At the falling edge of clk, out is reset to 0. At the falling edge of R3, out is set to 1.
How can I implement this logic in verilog? I am stuck because it seems to me that there is no way to distinguish between falling edge of R3 and falling edge of clk.

At the falling edge of both clk and R3, both clk and R3 are equal to 0 so I can't distinguish them.

    module startup(clk, R3, out);
   input clk, R3;
   output reg out;
   always@(negedge clk, negedge R3) begin

   end
   endmodule


texts:
I want to input some analog signals (audio) to my Arduino board. This signals are generated by a cellphone using the audio jack.

As you know we need to add an offset to the signal in order to stay always above 0 so arduino can read the value, and this is achieved very easy by a condenser and two resistors: (ignore the op-amp for the moment)

We just filter any offset on the input with the 10uF condenser and then add a 2.5V to the line using the resistors so the input always oscillate around 2.5.

Well this is ok if you are expecting always the same levels of audio signals, for example this circuit designed to "listen" audio from a microphone and so the op-amp can expect always values from -200mV to 200mV, and so we can set the correct amplification values.

But since my input is the audio jack of a cellphone, what if the volume of the cellphone is set to high or medium or low? What are the maximum voltage levels of an audio output jack of a cellphone? How can set an amplifier to amplify only when i need to or in other words, how can I guarantee a nice audio input on the arduino by regulating the input.

The circuit needs to be simple and ideally without the need of negative power supply.


texts: CL8800: how RC bridge regulate the tap current?

texts:
As in CL8800 datasheet, page 8, the document refers to simplified block diagram (Figure 3-6)

How do I calculate the value or R_SET for controlling the amount of current in each tap?

What is the relation between R_SET and I_TAP if V_TAP is given?

Thanks in advance!

http://ww1.microchip.com/downloads/en/DeviceDoc/20005357A.pdf


texts: Designing ammeter for an external ATX power supply adapter

texts:
I'm trying to design and build an external ATX power supply adapter, much like this one. I want to use it as a benchtop power supply.
I wanted my adapter to have one more feature: I wanted it to have a voltmeter and an ammeter at each positive rail (+12V and +5V). I'm planning on having an ATmega328P do the voltage readings and display them in a common 16x2 LCD.

Here's where my problems begin. I'm having trouble designing the ammeters. My first attempt at it was the schematics below.

The idea behind the schematics is that I'll read voltages in ports A0 and A2 to determine voltages of +12V and +5V rails, respectively, using ATmega328P ADC. There I would have my voltmeters, no problem. The voltage dividers in each circuit are there to bring voltages to the ADC's 5V limit.

To determine currents for the +12V and +5V rails, I would calculate the differences A1 - A0 and A3 - A2, assuming I'll be using 0R1 (0.1 ohm) 5W shunt resistors.

The shunts I'm planning to use yield 100mV/A. I plan on making readings well below 7A to respect the 5W spec on the resistors.

The problem is that I'm not comfortable having to make two readings to get the currents. I would much rather have the shunt connected to ground and then make a single voltage reading at its other end using the ATmega's 1.1V internal analog reference. That would give me the accuracy I want, all the way to about 6A. But then I don't know how to design such circuit so that all current that goes to each rail gets measured.

So, my question is: Is this design going to work? I'm afraid I won't have enough accuracy, especially because I'm depending on two readings to calculate current. Will the stacked up errors be too much?

Another related question: is there a better way to measure the current of each rail?


texts: How can I increase the number of hardware UARTs in a design with a single UART MCU?

texts:
I am using a TI CC430 MCU because it contains an embedded CC1101 radio frontend.  I would really like to stick with this MCU. However, I need to simultaneously interact with a separate serial radio, a FTDI (uart->USB), and an RS232 GPS.  So it would be nice to have 3 separate UARTS on the MCU.

What are my options for increasing the number of UARTs?  I have considered adding a CPLD and muxing the single UART to 3 outputs, but I really don't like that approach because it not really 3 simultaneous connections.


texts:
I am using SN75188 for converting 5V,0V 16 kHz square wave to -7V,7V 16 kHz square wave and using SN75189 to process opposite convertion. I have shown the dataheet information of them. I considered that i considered that i can do this operations with these ICs. Am i right? That was my first question. The second is i cannot find any information related to frequency range of ICs. Is 16 kHz signal value available for operation? If you share your idea, i will be happy.

SN75188 Datahseet Information:

SN75189 Datahseet Information:


texts: Using Arduino Uno R3 + Ethernet Module, how to control current pass to Lamps?

texts:
I have Arduino Uno R3 and Arduino Ethernet Shield V5.

What's missing in order to control 6+ lights (bulbs) from my home? Those are connected to 220V AC.

My idea is to send a packet via ethernet that has an order for example: "Turn on light 1", "Turn on light 4".

Maybe a relays module?

Obviously the power cables for lights will come from the controller. I want to test now so I can deploy it in real house lights.

Sorry if I am not being too much specific, I am starting to learn.


texts: Strange crystal schematic notation appears un-connected

texts:
I'm transcribing a Cypress CY8CKIT-059 schematic for use in my device when I came across this curious notation for the crystal:

What does this mean? Like normal, I assume it is connected across the P15_2/3 nets with 22p caps going to ground. But why do they indicate the 'X's on the crystal leads? This is how I believe it must be:

Is this correct? Can someone explain to me why they would put 'X's on the leads instead of connecting them?


texts: How to decide the DDR3 routing topology?

texts: I am designing board which has got 4 DDR3 Die on it, 64 bit SDRAM interface. DDR3 Memory controller will be xilinx FPGA. I have some confusion in the signal routing from the DDR3 interface to DDR3 memory controller. How to decide the routing topology for the 4 DDR3 die? Any logical reason for selecting T topology and flyby topology?


texts: How to trigger 50v solenoid with 120v AC

texts:
I have an old clock with an analog circuit and the timing sync mechanism gets triggered by a solenoid that likely requires 40-50v. The only power input into the circuit is 120v AC.

Ideally I'd like to trigger the solenoid from a microcontroller, but how could this be accomplished without a gigantic transformer?


texts: Industrial connectors with fail-safe disconnect under cable tension (like MagSafe)

texts:
Background/problem:

We install electronic monitoring systems on semi-mobile industrial equipment. The environment is harsh and sometimes our cables are treated in a very rough manner. This can result in cable breaks (usually at the connector terminating the cable into our equipment). This is a problem because at a minimum we then need to replace/repair the cable; at worse a short can damage our electronics.

We currently use Deutsch connectors which are extremely sturdy and waterproof.

The question:

Does anyone know of industrial cable connectors that operate with the same purpose as Apple's MagSafe safe disconnect? Ideally if someone yanks one of our cables I want the cable to disconnect rather than breaking.


texts: How to truncate an expression bit width in Verilog?

texts:
Consider an expression like:

assign x = func(A) ^ func(B);

where the output of the func is 32 bits wide, and x is a wire of 16 bits. I want to assign only the lowest 16 bits of the resulting xor.

I know the above code already does that, but it also generates a warning. The "obvious" approach doesn't work:

assign x = (func(A) ^ func(B))[15:0]; // error: '[' is unexpected


texts: What is the purpose of SRAM in the DS1307 RTC chip and the onboard AT24C32N EEPROM chip??

texts:
I am going to interface a RTC to PIC18F and  before doing so, I'd like to clear some doubts regarding the module and its connections. I am using the "Tiny RTC" as shown in this link!.

The following questions are:

What is the use of the SRAM in the RTC chip?
From my findings, I got to know that the SRAM is used to store the current time and date when the chip is powered off while being backed up by the battery to keep the time. Is this right?, If so, does the data backing up happen internally?
What is the use of the onboard AT24C32N EEPROM?. Does it have to do anything with the RTC chip?
I am not using the LIR2032 rechargeable battery but using the normal CR2032 non rechargeable battery. From this video link!, It is suggested to remove some components to prevent the CR2032 from being charged as it will cause overheating to damaging it. Just to confirm,Is this necessary?
Now coming to the module connections. How do I know If the +ve terminal of the CR2032 is connected to VBAT terminal of the RTC chip and its -ve to ground?. And how to identify the +ve and -ve terminals of the CR2032. I tried doing it by checking the connectivity using a multimeter, however, I am not able to figure out what connections to make if I need to use the battery.

Sorry, If my questions are too lame. But any advise and support regarding this will be helpful before I do the hardware connections. I have simulated it in Proteus as shown in the image below


texts: Curious Behavior In Logisim while trying to mimic a halt instruction

texts:
I'm in the process of trying to simulate a halt instruction based on some arbitrary value. My circuit design may not follow best practices as I'm disabling the overall or master clock sign with a tristate buffer and a comparator circuit. This is only meant to be used for study and research and isn't meant to be for practical use. So I'm not concerned if this is considered a "bad" implementation design.

What I'm after here is an explanation as to the behavior; the output results that Logisim is giving through its simulation.

I have an image with my circuit in 3 different conditions or states, albeit the last state is a slightly modified version of the original. I'll display the image here first so that you can visually see it's overall design. Then I'll give a brief explanation of the 3 states finishing off with my overall question towards my curiosity and or concern of this unexpected behavior.

-Note- The Registers that I'm using in Logisim are counter type registers 4 bits wide, but this should be obvious from the images.

Condition A:

The value in the counter register is at 3. On the next rising edge of the clock, I'm expecting it to go to four then halt as the comparator should return 1 and and through the inverter it should disable the connection of the clock through the tristate buffer. However it doesn't. This is where Condition B comes in.

Condition B:

Here I pulsed the clock one full clock cycle and as you can see the value went from 7 straight to 0, and the halt signal as well as the value coming out of the counter are not being compared, so the counter register just loops around.

Condition C:

Is a quick hack solution that works or gives the behavior that is desired however, it also appears to be an invalid solution. In Condition C, I tied the output of the comparator and the input into the tristate enable line to 0. As long as I have a non 0 value in the halt signal the circuit works and the counter register reaches the halt signal value, it does count up to that value instead of resetting before hand and the comparator does compare equal and produces a one which does in effect trigger the tristate buffer to turn off or disconnect the clock from the rest of the circuit. This the behavior that I want, however if you look closely you will see read lines in the circuit as multiple values are being sent through the same wire which is an invalid solution.

I have a few general questions regarding this.

Why is the original intended circuit as seen in Conditions A & B not allowing the counter register to count to the desired value and resetting at [n-1]. I've tried this with other values and it does the same thing. Thus the comparator part of the circuit never outputs 1 to disable the clock and why does it appear to work when I tie that same line to a constant 0 as in Condition C?

Shouldn't the original circuit count up to 4, compare the two and return 1 out of the comparator? Is this a potential bug in Logisim?

My other question would be what would be the proper way to design a halt signal in Logisim to stop the master or system clock?


texts: I've tried running following circuit in simulator, It gives value of current across top right most resistor(of 2k)=0.2mA(200microA), why it isn't 0.3mA as provided by current source?


texts:
The 74HC4051 Mux (spec is here: http://www.nxp.com/documents/data_sheet/74HC_HCT4051.pdf)

has 8 input/output pins labelled Y, one output/input pin labelled Z, three digital selectors S0, S1, S2, and an active-low enable pin E (bar).

That all seems perfectly reasonable.  There is also Vee which is labelled "supply voltage"

To test the mux, we set S0 = S1 = S2 = E = 0V
Then we set Y0 = 3.3V, then 0V

Taking The documenation at face value we set Vee = Vcc = 3.3V
When Y0 = 3.3V, Z = 3.3V, which seems reasonable.  But then when Y0 = 0V, Z = 1.4V???

If we set Vee = 0V, this does not happen, but why is it labelled supply, and if it's ground, why is it needed at all?


texts: How to check if my quadrature encoder is broken or not?

texts:
I have purchased some cheap quadrature incremental encoders (YUMO E6A2-CW3C) for which I have found "a" data-sheet here. Now based on my limited knowledge the quadrature incremental encoders are conceptually two switches. on the encoder itself, there is a color coding as:

Brown: 5 to 12 VDC --> this I suppose I should connect to 5V
Blue: OV(COMMON) --> this I think should be ground?
shield: GND --> this is also ground?
Black: OUT A --> this I think is the first phase/channel
White: OUT B --> and this should be the second phase/channel

but there is an orange wire which according to the above data-sheet is channel Z, but I have no idea what it is for.

now what I expect to see is if I connect the output of channel A or B to some LEDs it should blink when I rotate the encoder:

simulate this circuit – Schematic created using CircuitLab

However, what I see is those LEDs are on all the time. I measured the resistance between the pins using a multimeter:

                   |        | Brown | Black | White |  Blue | Orange |
                   |:------:|:-----:|:-----:|:-----:|:-----:|:------:|
                   |  Brown | ----- | ----- | ----- | ----- |  ----- |
                   |  Black | 1.4M | ----- | ----- | ----- |  ----- |
                   |  White | 1.4M | ----- | ----- | ----- |  ----- |
                   |  Blue  | 0.6M | ----- | ----- | ----- |  ----- |
                   | Orange | 1.4M | ----- | ----- | 0.7M |  ----- |

and the resistance doesn't seem to change by rotation. Now I want to know if my encoder is broken or am I making a mistake here? plus what the heck is the orange one?


texts:
I am fairly new to hands-on electrical engineering (I have taken Physics II and have played with computers and electronics all my life, but am only now truly seeking to learn how to safely handle many different electrical appliances) and am involved in a greenhouse automation project.

The greenhouse has 220V AC power.  I have a number of submersible liquid pumps that draw 12V, 1.8A DC and have 4A fuses.  I've hacked up some old router and cellphone AC/DC adapters that do the trick, but I would like to add a dedicated DC line to the work space for additional motors, pumps, sensors, and other electronics that need DC power.

My question is: if I have an AC/DC adapter that outputs 12V, 16.5A, 203W DC power, would that fry my 4A fuses (as I suspect?)  What if I have 8 or 9 1.8A pumps wired in parallel?  Could I hook and Arduino Mega into any old DC line, or must I downstep it to the current amperage?


texts: Blocking messages in one direction on a CAN bus

texts:
I have a vehicle that I only want to read CAN bus messages from. But I also have to send out messages on the same bus, but the vehicle may not receive these messages.

Is it possible to block the flow in one direction - so that I can only read from the vehicle, but the vehicle won't receive the messages I send out?


texts:
I am trying to build a voltage divider as shown in the circuit.
I want to adjust my Vout using the potentiometer within the range of 2V-3V.
With my current R1 & R2 I am not able to achieve it. How do I calculate the values for R1 and R2 so that I can adjust my output from 2V-3V?


texts:
I'm working with an LMT85 temperature sensor.  I want it to be waterproof, since it will be working submerged in water. I'm thinking of using hot glue on the connections and then using a heat shrink tube.
Is it a good idea use hot glue?


texts: Initial experiments with an oscilloscope

texts:
So I finally have access to an oscilloscope, after wanting to use one for a very long time.

Now that I am in university, I can use the lab equipment. So my first question is, what should I do with this new found resource?

Are there any experiments which you all suggest I should try as an introduction to this tool?

Thanks, I hope this question is not too vague.


texts:
I am new to breadboard electronics projects. I am looking to do this project but am a bit lost on what all I need parts wise. This is my current parts list:

WAV Trigger
Breadboard
1n914 diode
6N138 optoisolator
2 Resistors
3 M/F Jumper cables
Midi Cable
2 Ports

Are these correct?
What resistors do I use for this project?
How do I connect a midi to a port and what type of port should I buy?
What are the wires circled in the picture below? How are they connecting all the components?
In step 1 what is he closing the connection with? Should I add that to my parts list?

Thanks!


texts: Problems when loading an Ultrasonic transducer (reflected power)

texts:
I have a very simple setup that is giving me problems I cannot understand:

Apparently, the reflected power is the same as the power generated by the amplifier (both measured by the amplifier, although I double checked with a power meter). The load, a 50 ohms ultrasonic transducer in this case, seems to be completely mismatched. HOWEVER, this problem sometimes disappear after some minutes (5-10 min) without changing anything.

I have switched all the equipment, transducers and cables (+connections). Can someone rationalize this behavior? Could it be due to the driving frequency?

Some details if necessary:

The function generator is one from Agilent which I double checked by
means of an oscilloscope.
The RF amplifier is from Electronics &
Innovation
The ultrasonic power transducers are from American Piezo. The behavior described is the same for everyone of them.

Note: Obviously, my background in electronics is very limited.


texts: Replacing s with jw in transfer function. When the input function is oscillatory and has exponential decay

texts:
I understand a version of this question has been asked numerous times before but I could not find an answer to this specific one.

This is how I understood replacing s with jw. From the impulse response,

\$y(t)=\int_0^\infty h(\tau) u(t-\tau)d\tau\$ where \$y,u\$ are output, input.

Taking \$u\$ as \$e^{st}\$, \$y(t)=u(t)*H(s)\$ most of the sources Ive found say that it is easier to analyze the system for constant amplitude signals so we replace \$s\$ with \$j\omega\$ and I understand till this part.

The question is if \$H(s)\$ = \$\frac{1}{s^2+2s+2}\$ which has a stable pole at \$-1+i\$ and \$u(t)=e^{(-1+i)t}\$ wouldn't that mean the output should be unstable since the denominator of \$H(s)=0\$. Ive plotted the results on simulink and mathematica and the outputs are stable.

Can someone tell me what I'm doing wrong.

EDIT(28-oct-19)- Figured it out, I MADE A STUPID MISTAKE \$y(t) \ne  \int_0^\infty h(\tau) u(t-\tau)d\tau\$ but \$y(t) =  \int_0^t h(\tau) u(t-\tau)d\tau\$


texts: Selecting small motor (wrist watch sized)

texts:
I want to build a skydiving altimeter, which is a device with a pointer that looks like and is slightly bigger than a wrist watch. In this device I want to display altitude information using a pointer, again, in clock-like fashion.

It needs to have continuous and bi-directional rotation motion, so I'm initially discarding analog meters.

What type of motor fits the bill?


texts: How can I make a 10 minute and 15 minute buzzer timer?

texts: Basically, I have a big project going on in my campus which we were told to make digital counter. So when the timer counts reach at 10 minutes (by this case, the timer counts is shown by 7-segment display), it will produce alarm sound or buzzer sound, and when it continues and reach to 15 minutes, exactly doing the same by how the timer goes to 10 minutes. Any ideas guys on how to make the circuit? I'm kinda stuck here. (We aren't allowed using an IC NE555, but we are told to use 7-segment display, logic gates IC like IC 7408, any basic IC. And I'm on Digital Electronics course, I'm still learning about basic logic gates, boolean algebra, XOR and XNOR gates, multiplexer and duplexer. My reference book is Digital Electronics, a practical approach with VHDL by William Keiltz)


texts:
I am using PIC18F4550

I am trying to generate an interrupt every 1 sec, and by trial and error(i.e. just writing and simulating on hardware ) I am getting interrupt approx to 1 sec. Code for this is:-

 #pragma config PLLDIV = 5 , CPUDIV = OSC1_PLL2 , USBDIV = 2
#pragma config FOSC = INTOSCIO_EC
#pragma config FCMEN = OFF
#pragma config BORV = 3
#pragma config WDT = OFF
#pragma config CPB = OFF
#pragma config CPD = OFF

 void intinter(void)
{
RCONbits.IPEN =1; //Priority Interrupt is enabled
INTCON = 0b11100000; //all high and low priority interrupt is enabled, timer 0 overflow interrupt enable
INTCON2bits.TMR0IP = 0; //set timer 0 interrupt  low priority
}

void inittimer(void)
{
T0CON = 0b00000111; //prescaler of 256, 16 bit, internal clock
TMR0H = 0xFFFF;  // Set TMRH and L Value
TMR0L = 0x0000;
}

void interrupt low_priority timerinterrupt (void)
{
 if(TMR0IF == 1)
    {
        TMR0ON =0;//Timer 0 off
        TMR0IF = 0; //Timer 0 IF disable
        TMR0H = 0xFFFF;
        TMR0L = 0x0000;
        i++;

    if(i==4)
    {
//if i==4 I am getting approx 1 sec interrupt.
}

Now after reading the datasheet and about the procedure to calculate the value of the TMR0H and TMR0L register, I am unable to make sense of my code.

As I have set internal clock with default value by just using this,

#pragma config FOSC = INTOSCIO_EC

I think the clock is Fosc = 1Mhz, so the calculation is,
Our FCPU=1MHz/4 (We are running from 1Mhz Internal Clock)

=0.25MHz

Time Period = 4uS

Prescaler Period = 4 x 256 = 1.024x10^-3 (Prescaler is set to divide frequency by 256)

Overflow Period = 1.024x10^-3 x 65535 = 67.10 s (Each over flow takes 65535 counts)

So it seems each overflow takes 67 seconds but it is taking 4 overflow for 1 sec timer, how is it possible? Is my calculation procedure wrong? Or I am taking wrong clock.

Please help me understand my error as I am new to PIC programming.

Thank You.


texts:
I am implementing this circuit but want to make it automated to avoid the use of jumper headers. I have replaced all the headers with P-FETs.
Is this the best solution?


texts: Will placing a strong magnet near my electric skateboard Li-Ion Battery pack damage or discharge it?

texts:
The original clips securing my battery cover are broken and i thought of devising an alternate way to keep the cover shut involving a hard drive magnet and a hinge

the battery pack would sit in proximity (3-5 cm away) to the magnet while in use (1-2 hours/day), but I would remove it when the session ends.

Here's a rough plan. If  you can make any sense of my drawing skills, the battery pack sits right under the cover. The hard drive magnet would be inside the battery case (dashed trait)

Before refining this idea I just wanna make sure this setup would not be harmful to my battery pack or other electronics (bluetooth remote receiver, ESC, ...).
What if I decide to switch to a LiPo battery pack later?


texts: The way to efficiently operate some power devices with less loss, and appropriate heat sharing

texts:
I'm using a buck converter(OKR-T/10-W12-C made by Murata Power Solutions). The converter supports 4.5 ~ 14.0V input.

The input is 9.5V voltage from the another buck device.

And between of them, the schottky diode SR54L is stationed. So, because of the diode, some voltage drop occurs(0.2 ~ 0.3V) but the input is 9.5V so the voltage drop will not come a big problem.

Then, have to I use a schottky diode? Or, can I remove the diode?

Which way is more efficient to make less power dissipation? I want to use less power because of the efficiency but I'm worried about the heat dissipation of the converter. Will dividing the heat with schottky diode just not good solution for the heat sharing? Will using the diode can affect to the performance of the converter?

(Using heatsink is impossible because the converter is too small to use a heatsink.)


texts: How can feedforward be used with PID for motion control

texts:
In a motion control system where a motor accelerates, coasts, and decelerates (setpoint is position, not velocity!), what would be the benefit of using feedforward with PID, instead of solely PID?

How would you calculate a feedforward value to add to the PID output?


texts:
Do RGB LEDs have very different brightness levels?

I'm running an RGB LED (common cathode) via some TIP120 transistors, controlled from a raspberry Pi.

There is a 5v feed from the rPi.

Initially I had ~2k resistors in series with the output pins and the base of the trans. but they were failing to trigger so I've removed them.

I also then had what I thought were the correct resistor values in series with the LED (82R and 150R for red and blue / green respectively) but they were so dim as to be useless.

So those have gone as well.

So against everything I know to be "right" I've got no resistors on the LED or the output pins.
The red is nice and bright but green and blue are still both pretty dim.
I'm controlling with software PWM from the pi and have had to limit the red channel to 25% of the green and blue just to level things out a bit.

Any idea what's going on?


texts: Circuit to switch between direct USB and Bluetooth/battery charging

texts:
I am planning to modify a wired keyboard to use a wireless connection, using the HID Relay project (YT, GitHub) as the communication method, along with a LiPo battery, with accompanying  charger and booster (for simplicity's sake, I will refer to the charger/battery/booster/HID Relay combo as just HID Relay from now on).

Thing is, I still wish to use the keyboard using just a cable, in case of a low battery or the device where I want to use it doesn't have Bluetooth capability.

All those components will be inside the keyboard, with just the USB female connector and the switch being exposed.

1st version (Works partially)

My idea is to, instead of using an USB switching IC, just route the power line between a direct connection to the keyboard and the power input of the HID Relay, along with a option to just charge the battery.

I read from this article that power can be joined by using diodes.

Here is a (rather crappy, sorry) diagram for it:

(The HID Relay was condensed as a component for simplicity's sake)

My questions are:

1) Is this schematic correct? As in, is there something placed improperly?

2) On the 3rd position (Charge and Bluetooth enabled), in case of plugging the cable to a device that can interact with the keyboard, how can be the data pins from that source can be suppressed?

Here's what SW1 will do:

Position 1) Direct mode - pass 5V directly to the keyboard. In circuit 2, powers the IC to pass the data pins through.

Position 2) OFF / Charge only - Only the battery charging IC will receive 5V from the input USB port.

Position 3) BT mode - Allows for battery charging, while connecting the internal battery to the booster circuit (the 2nd connection set on SW1) that in this case, powers the HID Relay circuit.

Thanks in advance.

UPDATE: This version would not work in the case of, while using BT mode, a usb connection to a PC would interfere in the data lines shared by the HID Relay

2nd version (not tested yet)

Here's a version using a switch IC:

Another thing: I would prefer to not use a switching IC because they would be the only component not available locally.

This version is not tested as I don't have the IC in hand

3rd Version (UPDATE: Does not work)

Instead of the USB-specific IC, this version uses a 74HC157 selector IC, which is more accessible to me.

Sadly this version does not work, as the IC data lines are not bidirectional.

4th Version (Works as intended)

After checking the problem with version 3's data direction, I tried to use a combination of a inverter and an analog switch ICs (that I had lying around) to block the unwanted case of the external USB data lines interfering while the HID Relay was active. This seems to work perfectly.

Also, the physical switch used (3 positions, 6 terminals) guarantees that the VBUS line is cut while changing modes.

As the ICs are just what I had at the moment, the inverter IC could be any that have at least 2 channels.


texts: LAN9500AI (USB to Ethernet IC) hang if Ethernet cable removed

texts:
I need some help on debugging the issue faced on USB to Ethernet design. I have took reference form LAN9500Ai Development board.

Issue:- When Turn on the Power , USB to Ethernet work, and Three LED glow with one of them blinking. After that I removed the Ethernet cable and plug it back than it does not work. ( Sometimes All three LED light still glow even after removing the Ethernet Cable). My schematics is attached.

Schematics details:-
D6,D7,D8 and D9 NOT mounted.
R33 is Do not Mount
Connector J2 comes form PC USB port ( PC USB 5V convert to 3.3V via regulator than 3.3V apply to connector j2) , See attached
C2,C3,C4 and C5 Do not Mount.

Unsuccessful solution Tried
1. Mount C2,C3,C4 and C5 and No advantage
2. Remove R36 but no advantage

Successful solution Tried
1. Removed Connector J2 and reinsert then it Works, but again if i remove the Ethernet cord and reinsert it did not work. So every time after removing and reinserting cable i have to follow this

In Schematics IC U3 pin , (manual Reset) , i tried to reset the LAN 9500 chip using this pin , and Chip get reset and it works, but again if i remove the Ethernet cord and reinsert it did not work. So every time after removing and reinserting cable i have to follow this

Please suggest how to resolve this problem, since in hardware i do not have reset control in current PCB version,

(Schematics broke down to two above image, since do not know how to attached PDF file)

Thanks


texts: Is Wifi With Arduino Fast Enough to Control a Vehicle?

texts:
I'm building a simple motorized vehicle that I wish to make autonomous through the use of neural networks. I am using Arduino as I am new to electronics but more experienced in programming. I'm sure there are much more powerful microcontrollers out there, but for my purposes (and funds) an Arduino Mega 2560 is what I would prefer to use (and I already have one).  Now I suspect that the Mega, even though it is far more capable than an Uno or similarly small Arduino boards, is not capable of running a neural network that take inputs from a decently numbered array of sensors and generates several outputs (maybe 5?).

My idea, then, is to run the neural network on my phone if it is fast enough, or my desktop computer if not. Either way, I figured the best way to transmit the input and output data back and forth between the external processing unit (phone/desktop) and the Arduino will be WiFi. I saw a YouTube video of someone controlling an RC car with an android app they created, transmitting data through WiFi, and while a bit laggy for RC purposes, it seemed to be within 1 second of latency.

Does anyone know if WiFi would be fast/reliable enough to control a little autonomous vehicle? Assume that it will be traveling about the pace of an adult human walking, and reacting to its surroundings based on sonar sweeping. (Latency of data transmission will be important because the sonar data will have to be processed by the computer, but ideally the robot will keep moving without slowing down or stopping to wait for the data.)


texts: Selecting a stable operating point in a core loss vs temperature graph

texts:
Not a native english speaker so please bear with me.

I want to build an Inductivity of 10uH for a sinewave current (50kHz, 0.5A RMS) and calculate the magnetic resistance . Magnetic Flux should stay at 200mT. I can select a 3F3 core and have the core loss vs temperature graph but i need to pinpoint a stable operating point. What confuses me is the frequency next to the 200mT magnetic flux on the graph. My sinewave has 2x higher frequency than the one on the graph, which value do I need for my calculation ?

Task is to find the right air gap for the core

I can select models with one of the following Al (nH) values:

40+-3%
25+-3%
800+-25%

This is how I wanted to proceed, first I want to calculate the power loss by multiplying the core loss (first finding the right operating point) with the effective core volume (215mm^3), afterwards I can use R = U^2/P to calculate the magnetic resistance with Ul = wL*Irms

for the air gap i can use following formula to first calculate the windings LI=NB*A

afterwards I can calculate the Al value with Al = L/N^2 and select the right one.


texts: Limiting small signals to one direction (ideally with passive components)

texts:
My setup is as following:
I use a Y-Cable for splitting an audio signal to two devices (boxes and earphones). The headphones have quite big speakers so they act also like a microphone - feeding back the signal to the boxes which then amplify the crackling signal.

Initially it sounded pretty easy to me, but it got more complicated than I thought. Additionally, I'm still not sure if there is a problem with the linearity of components up to 20kHz.

The idea was to use a Schottky diode in between the two devices, so none of them could back-feed the other. Unluckily the signal is only 250mV, so even a germanium Schottky diode with voltage drop of 0.2V is not so optimal.

Are there other solutions which are ideally passive or semi-passive by using a small part of the signal for their independent power supply? (Multiplying voltage until its common 5V and using only a few nA)
Ideally kind of a low signal diode: If the same principle works for big signals, there should be a way making it work also for small signals.

Or maybe a second reverse diode which will lift the "signal voltage drop" back up? For this I thought a logic connection that has a diode attached, but the logic chips need their own power supply.

What could be a simple circuit?

Other searches:
What I found using electronics between audiojack, was pretty sparse: One was the use of Schottky diodes (for bigger signals), the other was this (but not so related): http://www.instructables.com/id/How-to-Harvest-Power-from-an-Audio-Jack/all/?lang=de


texts:
In a project I'd like to control a heating circuit with an SSR, and I'd need a contingency plan for when the SSR fails closed, and the microcontroller cannot turn off the heating element, which would be unsafe.

The easiest option I can see is to have two SSRs in series, and do a check on startup to check that turning off either will interrupt the current, and display an error as well as refuse to operate.

What would be considered best practice here?


texts: How do I determine the electrical characteristics of a cheap kit motor?

texts:
I have a kit that includes several cheap 3V electric motors of the free-spinning variety (e.g. not servos or steppers).

I would like to design a simple controller circuit to replace the contact switches that came with the kit. I am doing this largely as a learning exercise with ISIS, and so I would like to simulate the design as accurately as is reasonably possible.

How can I measure or otherwise determine the simulation characteristics needed to model these motors (shown below)?

I have changed the nominal voltage to 3V, and I can probably figure out how to measure the zero load RPM, but which of the remaining parameters are critical to accurately simulating the motor's electrical characteristics in my circuit?


texts: Offsetting Voltage from 2.5 V to 0 V without Effecting gain

texts: I'm trying to digitize a Hall Sensor whose center voltage is 2.5V and the gain it's output is 1.5V to 3.5V, or ±1V. My digitizing card's center voltage is 0V and I would like to get the full range of the sensor in the 0V space, -1V to +1V.  I'm using a LM358 op amp to try to do the task.  I'm very new to building circuits and I really don't know where to start.


texts: Reading the closing of 12 volt circuit over RS232

texts:
Car trouble.  I suspect the fuel injector circuit.  I am trying to construct a com port reader that will place a timestamp into a log on the closing the 12v fuel injector circuit.

The fuel injector is a simple normally open 12v circuit of 2 wires.  The + is tied into the ignition switch.  The ground is held open by the ECM (Electronic Control Module). When it is time to squirt fuel into the cylinder, the ECM pulses/flashes the ground to complete the circuit.

I am planning on using Eltima's Serial Port Monitor to record the event of the closed circuit with a timestamp on a single injector and store the data into a log so that I can evaluate and analyze the data.

Originally, I thought I would simply run pin 3 of a DB9 to a back probe on the injector and run the engine.  But with the circuit always powered by 12 volts, I would get a reading on pin 3 coinciding with the ignition switch and not with the pulsing ground.

Do you have any ideas on how to read the pulsing ground on the fuel injector?


texts:
The notation \$ c|d \$ is to be read 'c NAND d'
I have this function:
$$f(a,b,c,d)=(a+b)*(c|d)$$
$$=(a+b)*(\overline{c*d})$$
$$=(a+b)*(\bar{c}+\bar{d})$$
$$=(a\bar{c}+a\bar{d}+b\bar{c}+b\bar{d})$$
$$=(\bar{c}+\bar{d}+\bar{c}+\bar{d})$$
$$=(\bar{c}+\bar{d})=(\overline{cd})=(c|d)$$
There must be some mistakes I have done. My final result has to have a NAND between each two terms. Don't know how to get there.


texts: Can the inductive kick be discharged without a freewheeling diode, in this example?

texts: In literature we commonly see the use of a freewheel diode to protect the circuit against the inductive kick when the switch goes from closed to open (Fig 1). However, what would be the pros/cons of discharging the energy to ground through say a Zener diode (Fig 2)? I have never seen this in practice and I wonder why.


texts: How to change the Circuit Diagram to indicated a connection to a sourcemeter?

texts:
I have 2 circuit diagrams representing the connection of a transistor.
However in reality the Current/Voltage source and Current/Voltage meter are done with a SourceMeter.
How do I modify the circuit to accurately indicate that the Transitor is connected to a SourceMeter?

The following circuit diagram represents a TFT where we are:

Passing a voltage (with SMU) between Source and Gate (VGS)
Passing a voltage (with SMU) between Source and Drain (VDS)
Measuring current (IDS)

simulate this circuit – Schematic created using CircuitLab

The second circuit diagram represents a TFT where we:

Shorted the Drain with the Gate (VDS)
Are passing a current (IDS)
Are measuring the Voltage (VDS=VGS since it is shorted)

simulate this circuit

How do I change it to indicate that I am using a Sourcemeter?
And also how would I show that the SourceMeter is connected to a PC, or is it redundant?


texts: Basic resistor question for parallel LED circuit

texts:
I'm planning on building an LED circuit to place inside a model miniature for wargaming. The circuit would be in parallel as I'd need a really big battery to power up all the LEDs.

I wanted to check my understanding of setting up the resistors so things work properly. I'm going to have different types of LEDs with different voltages but here's my basic question.

Let's say I have 10 blue lights at 3.4V 20mA and a 9V supply. Based on my calculations each lamp would need a resistor of only 28 ohms? My math is

$$\frac{9-3.4}{\frac{10\cdot 20}{1000}} = 28$$

Is that right? The final circuit will have close to 20 LEDs, and it seems like at that point the ohms of the resistors will get much smaller?

Once I figure out all the different types of lights (all at 20mA), I will need to calculate the resistors individually for each as they have different voltage requirements?


texts: Why is the signal at X getting distorted at the input of the mixer (node "X" as shown in figure)

texts:
If the signal at X is different from the signal at Y or the pure sine (transient difference) at Y gets distorted at the X, then the sample and hold operation of the input sine wave is not happening here. The attached figure is a Spectre RF simulation of the simple sampling mixer.

Is something wrong with the simulation setup or LO feed through?


texts: Timing Analysis of Asynchronous Interface

texts:
I have performed timing analysis for synchronous interfaces using clock signal. But how do we do timing of asynchronous interfaces where there is no clock??

To be precise, I am using P2020 from NXP & trying to perform timing analysis of local bus interface.

How do I start without having a clock signal?


texts: How it will work if i solder thin wire with thick wire

texts:
I have a simple power supply for a rc airplane. I need to connect the speed controller to my brushless motor. The motor has very thin wires without a connector. But the speed controller has thick wires. I would like to connect them.

Will it heat the wires?


texts:
I'm trying to connect a buzzer to my Arduino Uno to play a tone. Instead of giving a melody I will give a HIGH value which translates in to 5V. Since I don't want to blow up anything I think I should use a resistor. But according to Ohm's law, I need to know how much miliamps the buzzer will draw. (R = V/I and in my case, I can't find my buzzer's I).

Any ideas on what resistor I should use?


texts: ESP32 - Can I safely use GPIO ADC2 pins for non-adc use while using WiFi

texts:
According to ESP32 design guidelines; ADC2 GPIO's should not be used when using WiFi due to conflicts. (or used with restrictions)

This affects GPIOs 2,12-15 and 25-27.

Suppose I use don't use any of the ADC2 GPIOs for analogReads while using WiFi, can I safely use those ADC2 GPIO pins for digitalWrites and digitalReads without conflict to WiFi?

Thanks


texts: What kind of basic circuit design can block current if volage is about a certain level?

texts:
What kind of basic circuit design with basic components (no op-amp chips or IC's)
can be used to stop current if voltage goes above a certain level?


texts: I want to energize a solenoid based on a temperature without arduino?

texts:
I want to open a 12V solenoid valve and close another based on a temperature reading I will be getting from the lm35dz temperature sensor. I should mention, the solenoids are normally closed and they will be activated through relays that are connected to the arduino board.

I think I can do this project with an arduino board, but I was wondering, is it possible to accomplish this same task using electronic components ?


texts: Why is there ampere listed in DC power adapter?

texts:
1.The current of a battery is decided by the resistance of electronics used.(Correct me if I am wrong).So there is no limit to current than can be taken from a battery (Except the time)

2.Is this also true for AC(No limit for current that can be taken out)
If both of the statements are true, then why there is ampere listed in the dc adapter (mobile adapter).

3.When I use the DC adapters for my project what should I take into consideration (Should I take the amperage listed into consideration)


texts: Need help! SOT23 SMD transistor identify by marking FEQEQ

texts: Can somebody help me to identify SOT23 SMD transistor by marking FEQEQ


texts: Is noise density over a bandwidth a measure of the noise's standard deviation?

texts:
Suppose I have a sensor which has a dominant white gaussian noise source, a \$1\textit{unit}/\sqrt{Hz}\$ noise density and a bandwidth of 100Hz. Then the noise becomes 10\$units\$. Is this a measure of the standard deviation of the noise? What exactly is \$10units\$ a measurement of?

In essence my question is, assuming a AWGN source with noise \$10units,  \$ is it proper to say that this implies that the noise \$w \sim N(0,10^2)\$?


texts: Why is one transistor in active and the other in triode?

texts:
Vtn = 0.4 V, W = 1um, L1=0.25um, L2=0.5um.

For a question I got the circuit above, and the solution said that M1 is in triode and M2 is active. Also, V1 is unknown so I can't figure out how they determined this. Any help?


texts:
I'm building a simple intrusion alarm system with a piezo buzzer fed by a 9V battery, I have a switch to activate/deactivate the alarm, and a trigger (like a switch) connected to a tripwire so if someone goes through the wire the alarm is set off.

My question is which of these configurations (A or B) is better in terms of saving battery life (so that the battery lasts longer if there is never an intruder), is there even a difference between the 2 configurations. I'm a newbie.

Conf A:

Conf B:

Which one would you use?


texts: Part identification help needed? Diode SO8 package with logo

texts:
I've been trying to identify the following part. It is marked with the following logo:

I haven't come across this logo before, but the "P" and the fact that it is a likely a diode (see below) brings Panasonic to mind.

The part is as shown:

Its reference designator is "D12" so it is likely a diode array of some sort. The markings are: logo + "0551 STA". It appears to be connected between a transformer and a Broadcom 10/100 BASE-TX (ethernet) transceiver, specifically the BCM5221 (Datasheet).

Can anyone identify the part or the logo as shown?

Thanks in advance.

Sam


texts: Building a wireless keyboard (preferably with a kit)

texts:
This is the project that spawned these earlier questions.

I'd like to  create my own keyboard. Functionally it's going to be a keyboard, but visually it's going to bear more semblance to a joystick than to a keyboard. (Except there won't be a movable stick; there are just going to be many small buttons for each finger to be responsible for.)

It would come in 2 pieces (i.e. 2 joystick-like things.) I would mount each of those to the end of the armrest of my office chair. I'd like to have it connected to the computer wirelessly (either by Bluetooth or anything else.) That way I could move freely with my chair and not even have to put my hands on the desk.

My goal for this is to create the world's most ergonomic and efficient keyboard. I looked around on the Internet for a keyboard like this, but couldn't find one, just a bunch of defunct companies. (DataHand looked okay, but you can't get it even on eBay.) I would easily pay $2,000 for a keyboard like this, but I couldn't find one.

I also intend to use an assortment of AHK scripts with it to boost efficiency; for example allowing chorded keys to type common words, to save even more effort.

I'd like to note that I'm a newbie at electronics and have very little experience with it. (I'm a software developer.)

Now, the way I've approached this is buying a Microsoft wireless keyboard and trying to connect to its switches. But I've underestimated how difficult this could be. The main annoyance with this is that there isn't a separate circuit to close for each individual key. I could play that keyboard's game and create a circuit for each combination of the connections on the keyboard. But, if I could simply buy a kit that'll just give me a connection for each individual key, that'll make my life so much easier.

Someone pointed me to MaKey MaKey. It's a great project, but (a) it doesn't have wireless built-in, only as an add-on which seems to require some Arduino knowledge to use, (b) there don't seem to be connections for each and every keyboard key and (c) I'm not sure whether their approach of using high resistance switching and a moving window averager would work for a keyboard with normal switches, rather than banana-operated keyboards.

Is there something similar to a MaKey MaKey, except without the above issues?

I'd also appreciate any other suggestions and ideas relating to this project! Thank you!


texts:
Is it bad coding practice to use Buffer Ports in VHDL?
I define an entity with an out port with o_done.
entity blahblah is
  port (
...other signals...
 o_done    : out std_logic;
  );
end entity blahblah;

The synthesizer does not like me reading an out port and wont synthesize it - even though it is legal VHDL 2008 code.  I can't change my synthesizer.
I use o_done in 2 clocked processes:
process begin
    wait until rising_edge(clk);
    if (reset = '1') then
      o_done <= '0';
    else
      if ( State1 ) then
        o_done <= '1';
      elsif ( o_done = '1' AND State0 ) then
        o_done <= '1';
      else
        o_done <= '0';
      end if;
    end if;
  end process;

  process begin
    wait until rising_edge(clk);
    if (reset = '1') then
      count <= to_unsigned(0, 8);
    else
      if( stateS0 AND done = '1' ) then
        count <= to_unsigned(0, 8);
      elsif( stateS1 AND y_counter >= 2 AND p >= 0 ) then
        count <= count + 1;
      end if;
    end if;
  end process;

Again, o_done, since defined as out in the port declaration, is not synthesizable since the synthesis engine isn't fully VHDL 2008 compatible.  I can't change the synthesizer.
So how do I work around o_done being an output port and wanting to read it ?
Can I make an intermediate signal - how do I do this typically ?


texts: How could extension cord detection be implemented in Tesla Roadster?

texts:
Googling finds evidence that Tesla Roadster electric car can detect cases when it is plugged in via extension cord.

Specifically this page lists error codes 937 and 9 meaning "extension cord detected". And this post says that when a cable with 2.5 square millimeters cross-section in each wire is used the charging goes just fine but when a cable with 1.5 square millimeters cross-section in each wire is used the car displays "extension cord detected" message.

Now the latter post says it's because of notable voltage drop on a thinner cable. Looks reasonable but the lower voltage on the car end of the cable can be because the mains voltage gets lower than the nominal, not because of voltage drop in the cable.

How can such check be implemented so that it only detects thin wires and ignores cases when mains voltage is low?


texts: Is resistor/capacitor in parallel to the transformer primary (adequate) inrush protection?

texts:
Having tackled my first project using a mains transformer (in the UK - 230V), I haven't put any inrush protection into the circuit. The circuit is a power supply, following these instructions: The Spyder - an Eight-Output Pedalboard Power Supply.

The schematic shows a resistor/capacitor in parallel to the transformer primary, which I neglected to put in. My guess and hope is this is what is needed to limit the inrush current to the transformer. I have come humbly to you because I can find no other examples of this being used as inrush protection, and  because currently (no pun intended) if I switch on the supply my TV will turn off then on briefly, which I can't see is doing it much good.

Is this resistor/capacitor combo intended to stop inrush current, and is it adequate?

If it is adequate, what component values would you recommend? And if not, what component(s) do I need and how should it be wired?


texts:
I am trying to repair a Nokia X6 headset in which one earpiece is not working. Any help on the questions below would be greatly appreciated.

Is there a way to test the earpieces with a multimeter to identify whether it has a problem?
How can I check the connectivity from earpiece to the headphone jack? Can I simply check this by connecting one end of multimeter to the wire at the earpiece and the other end to the TRS connector?


texts: What is voltage trimming in bandgap references?

texts:
I just started reading about bandgap reference circuits (PTAT, CTAT generation, etc.) in CMOS and I see a lot of papers about something called trimming in relation to these.

What does it actually mean and why is it used?


texts:
Im looking to drive a 16 vac solenoid from a battery pack. Specifically I want an electric door catch to function when mains are down. I want to do this with out with out using a commercial UPS. Im not worried about doing the switch over from mains to battery; just how to get the correct form of power to that latch. Im assuming I will only need about 650-800mA of current for maybe 5 seconds per unlock event.

Ive seen 4047 multivibe based inverter designs with a center tapped transformer but I have also seen that there are some issues with most of those designs (lack of any kind of regulation.) Im also wondering If I need simulated AC or if I can just send pwm dc at the door catch and get the desired result. I've heard there is a way to do it called "peak and hold" basically do one high low switch then like 50% duty pwm on high to drive ac selonoides from DC but i have only seen this mentioned once.  any advice would be appreciated.


texts:
I am having some issues making my boost converter (TPS61085PWR) output the correct amount of current to 3 LEDs connected in series. I am using a 600 mAh 3.6 V lipo battery to power the circuit. When the circuit is being powered from 3.6 V, the boost converter is outputting ~11.5 V, and the LED's are consuming ~0.011 A. When I increased the input voltage to 7.6 V, the boost converter outputs ~11.6 V, but the current goes up to 0.09 A (where it should be). I am running this IC at 650 kHz.

TPS61085PWR specs.

Inductor specs.

LED specs.

If anyone could give me some insight to this issue I would be forever grateful!


texts: what is the point of this "C" shaped metal 'clip'? (circled in yellow)


texts: Mitigate voltage drops when using a relay

texts:
Hi and thank you for reading my question.

I have a small experimental solar panel setup which charges a deep-cycle battery using an MPPT converter.
I would like to power some garage and garden lights using this setup and would like to include some low-power computers like the Raspberry pi.

Because the setup will not generate enough power during the dark winter months and during multiple days of bad weather I would like to build in a back-up power supply.

The setup is simple:
I'm using a XH-M602 battery monitoring module that will switch on a relay when the voltage drops below a configurable voltage and will switch off the relay when the power has reached another configurable threshold.
Using this module I want to power a 230v 30AH DPDT relay that switches between the 12V battery and a 12V AC to DC transformer.

When using this setup however there will be a voltage drop/spike, partially because it's switching from a low battery to a transformer and partially because of contact bounce.

What is the best way to mitigate these voltage drops? I was thinking about using capacitors, but i'm not sure how to incorporate this into my project.

TLDR:
Want to switch from power sources using a DPDT relay, want to mitigate the voltage drops during that transition.

I wanted to include some images from my oscilloscope, but it somehow refuses to save them to USB atm, but i'm sure most of you know what i'm talking about.


texts: Delayed insulation failure of DC barrel jack

texts:
Recently I had to replace a male DC barrel jack that connected a string of LEDs to a driver. Unconnected, I measured 100 VDC out of the driver.  The male jack I salvaged from an old 12 VDC power supply.
I made sure the current out of the driver is lower than the current the old power supply was rated for, but there was no way to find out what the jack´s voltage rating is. I replaced the jack and ran the LEDs for a couple of hours, after which everything ran normally and the jack didn't feel warm at all.
What I am worried about is that the jack is being used at a voltage higher than it was originally intended for. It ran without any issues for a couple of hours. If insulation were insufficient, I would expect it to fail rapidly.

How long does insulation take to fail when used over its rated voltage?
How is it expected to fail?
Should I be worried about my replacement causing a fire or other adverse effects?


texts: Compact multi-cycle adder for fpga: adding 1 to wide counter

texts:
I want to implement some kind of event counter in my FPGA design (Vendor-A or Vendor-X). I have several dozens of signals: half are 1-bit and other half of them is 5-bit. Signals are located in different parts of my design.

I want to count summation of every signals at the same time. Signal will come at high frequency, sum of every signal should be written in 48- or 64-bit register or memory. There is no much free space in my FPGA and I want not to use full 64-bit wide adder, but find some more compact (in number of LUTs required).

How should I design my adder to be more compact? Should I split it into small fast-counting counter (of 8, 12 or 16 bits) and slow and compact serial adder for remaining bits, which will use carry from small counter? Small counter will send carry not too often, so I will have hundreds of ticks to work on wider parts in multicycle adder. Can I use one serial adders with several different small counters?


texts: 3x AA battery phone charger input voltage drop

texts: I am using a 0.9-5 V to 5 V dc-dc step up converter to charge a phone using 3 AA batteries, but whenever I plug in the phone it starts charging but the input voltage drops from ~4.5 V to less than 2 V and the converter only heats up without really charging the phone even though it lights up as if it is charging. How can I fix this problem?


texts: Energy Meter energy calculation from power

texts:
I have interfaced a smart energy meter IC (ADE7878) to a microcontroller. The datasheet of the IC can be found here,

http://www.analog.com/media/en/technical-documentation/data-sheets/ADE7854_7858_7868_7878.pdf.

As per the datasheet, on page 50 total active power of each phase can be read from the registers AWATTHR, BWATTHR, and CWATTHR. What parameters I should consider and formula I should use to calculate the kwh value ?


texts: How do I make an electrical signal from a switch into an AVCRP signal to control audio player on my phone

texts:
This is my first post here so bear with me. Here is what I'm trying to do:

I am making an audio box that receives a Bluetooth audio signal from a mobile device and can rewind or fast forward that audio track you are playing through the box. This is the same concept as having Bluetooth headphones that let you play/pause/fast-forward/rewind. I have searched high and low on the internet to learn how a Bluetooth audio remote works and I have come up with nothing. I researched AVRCP and I think that is what I need to use to accomplish this but I don't know how to implement it and take an electrical signal from a switch and turn it into an AVRCP signal to rewind the song on my phone. Let alone how an AVCRP signal works and how it can specify volume up or down or play or pause.

I hope I explained this well enough. If not I can explain more. Thanks for listening an I hope someone can help me solve this or at least tell me if it's possible or not and then point me down an alternate path.

Jeff


texts: How can we measure sinusoidal signals in atmega8 ?

texts: How is the signal frequency measured in ATmega? In particular, how is the signal frequency (sine) measured in ATmega8?


texts:
Consider the following the frequency response of the impedance of a resistor component :

We know that a resistor has a parasitic capacitance and inductance due to its leads. So the impedance of the resistor = \$Z_{inductor} + \frac{Z_{resistor} \cdot Z_{capacitor}}{Z_{resistor} +Z_{capacitor}}\$.

To find this parasitic capacitance we should use the point at \$f = 1.592\cdot 10^3\$  in such a way that \$100 = \frac{1}{\omega\cdot C}\$.

So my question is, why did we equate Z=R=100 to \$\frac{1}{\omega\cdot C}\$ only?

Why not to   \$Z_{inductor} + \frac{Z_{resistor} \cdot Z_{capacitor}}{Z_{resistor} +Z_{capacitor}}\$?

One more question, why did the impedance decrease after this mentioned point? According to my understanding, the impedance before this point =100=R, if the capacitor effect will be effective after this point then this effectiveness should be added to R (i.e Z= R+1/jwc) and therefore the curve should not decrease?


texts: Automotive power supply - considerations for selecting fuse

texts:
A power supply circuit for a device that runs off the 12V battery of a car, is shown below.

simulate this circuit – Schematic created using CircuitLab

LM7805 is used to generate a 5V supply for the circuit - max load current is 200mA. A forward diode and a TVS diode are used for negative/positive spike protection (load dump). And a 10R, 2W resistor is used to limit the inrush current due to the 470uF cap at the input of LM7805. To prevent tripping during load dump or inrush current events, I am using a 3A slow-blow fuse (1.27 A2s).

Questions:

One normal current overload situation is inrush current due to the 470uF cap (inrush current = 1.2A but might be 4x that if a huge positive spike occurs on start up). How do I calculate the inrush current pulse duration?
Another normal current overload situation is load dump wherein, as per ISO-7637-2 pulse #5, the pulse duration can be as much as ~500ms (Vp ~ 100V). Vc for the TVS diode I am using is 30V so the circuit could potentially see a current pulse of (100-30)/10 = 7A for 500ms due to load dump. Is my calculation correct?

3.Considering the above, I am using a 3A slow-blow fuse but this might actually be useless considering that LM7805 should prevent more than 1.5A being drawn through the circuit and if LM7805 input node gets shorted, then a maximum of 12V/10R = 1.2A (nominal) would flow through the circuit. This 1.2A would be sufficient to burn out resistor & is therefore a concern. However, if I use a lower current rating for the fuse (say 1 or 1.5A), it might blow up during either of the 2 normal current overload situations above. Plus if I take derating factor of 0.5x due to thermal cycling and temperature, a 1 or 1.5A fuse might blow that much more easily couple of months down the line. Also, I don't think I can increase the resistor value much - the max voltage drop I can afford across it is ~3V (min LM7805 i/p voltage = 7V and there will be voltage drop across the FWD diode and fuse in addition to R) which for a 200mA peak load current, means 15 ohm max.What would be the optimal tradeoff here with respect to selecting the fuse?

What sort of situations could actually result in a short to GND at any of the nodes connected to 7805 i/p? i.e., assuming the device is mechanically robust, should I still be concerned about a potential short to GND there?


texts: Thermal compound for Alumina Ceramic Insulator

texts:
My main question is there any article or standard that says that Alumina Ceramic Insulator needs any thermal compound or it could be used as it is (in particular for the Transistor/Triac/Thyristor), I mean just dry contact by tight screwing will be ok?
Second, if the first is true, what thermal compound will be the best for that type of insulator?


texts: Simple sound pulse (or frequency) to voltage for switch

texts:
I am building a tiny project using an android phone -- it simply has to drive a transistor switch on and off. Instead of going down the route of trying to interface to a micro controller via USB/Bluetooth, etc., I thought it would be easy to drive the switch through the headphone jack: play a sound through the jack and have the sound translated into a DC voltage that can drive the transistor.

I found this post, but it didn't seem to lead anywhere.

EDIT: A bit more searching led me to an LM2907, which seems like it might do the trick.


texts:
I know in free licenses of modelsim / questa simulations run slower than the full version.

But how slow?  will it be 2x 3x 10x faster in the paid version?

what about actel/microsemi free version ?


texts: Linear Technology PMIC (LTC3566) - powering circuit entirely from VOUT1

texts:
I'm looking into Linear Technology's LTC3566 PMIC for an upcoming portable design. Its a really nice PMIC with a buck-boost regulator on-board. Here is the typical application:

The reason I want to use this part is cause it allows me to save board space by not having to include a DC/DC regulator. In my application, I would power my entire circuit of Vout1 and skip the use of Vout altogether.

The one part I'm not clear about is this section here in the pin descriptions:

I have two concerns:

It says the majority of the load should be powered by Vout - In
my application i would power my entire application from Vout1. Is
this a concern?
The chip is smart enough to partition input power between Vout and the battery. Do I still get that functionality by using Vout1?


texts:
Below is the circuit for backup power from BAT2 when BAT1 is missing. BAT1 in my case is the LD1117 regulator.

simulate this circuit – Schematic created using CircuitLab

Suppose only two situations are possible: (1) BAT1 and BAT2 both exists, (2) BAT1 missing. Can I exclude D2?

UPD. "BAT1 missing" mean LD1117 still exists in the circuit, but its input voltage missing.


texts: Building a synthesizer with no prior experience

texts:
I've got an extensive music background and have been infatuated with synthesizers since I was young. I had dreamed of going into an EE program to make my dream a reality, but I couldn't afford school (long story).

Basically, I'd like to build a 3 oscillator analog synthesizer, but I have zero experience building boards. I know basic signal flow and process and have a strong design sense, but I really lack the knowledge otherwise to get started.

I think starting simple with a 1 oscillator and building upwards would be an awesome learning experience, and I would love to get to the level that some of you are at and actually make a fully usable synthesizer.

My question is, for audio-oriented electronics, where can I get started for this full analog synthesizer? Am I reaching too far? What will I need to make this happen?


texts: How should I choose a power supply for a stepper motor, if the motor requires 7V and 1A? Should I buy a power supply of exactly 7V and current of minimum 1A?


texts: Schottky diode leakage / PowerPath sharing

texts:
I've got a pretty simple circuit here where main regulator is powered either from battery or from USB source. When USB power is conected Q2 is closed and battery is charged by MCP73831 at the same time as system is powered from USB bus via D3 diode (PMEG4010 in my case).
The problem that I'm facing is that even if I'm using a very low leakage Schottky diode (PMEG4010 should have less than 7uA reverse leakage current at 10V, while I only have max 4.2V LiPo voltage) I still have around 0.8V at Q2 gate. This is taking into account that my R3 is already 10kOhm, not 100k as per the image below. Maybe I don't understand something? Why gate voltage of Q2 is not going closer to GND?
Previously I was using a B130LAW Schottky diode and Gate voltage was about 1.03V. So switching to PMEG4010 definitely helped, but still the result is quite strange to me.
My circuit is based on circuit from here and yes, I've read all the comments about pull-down resistor to fix the Schottky diode reverse leakage current, but if that current is around 10uA than 10kOhm should be more than enough to bring Q2 gate voltage down to almost 0V, but that's not happening.
https://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing/
Please have a look at my schematic. I'm talking about the situation when no VCC_USB is present and system is powered from VCC_BAT only, so Q2 should be open because R3 pulls VCC_USB net down opening Q2 MOSFET. Thanks for help!
P.S. You can ignore MCP130T and TPS63060 circuits as they're not relevant to my question.


texts:
Is there a design methodology to create a circuit that implements a specified transfer function?

I know that there are automatic top-down design flows in logic design where you describe a function at RTL level and technology does the rest, but what about other domains? Transfer functions were taught to us in University. I am sure that they can be implemented with linear elements: resistors, inductors and capacitors. But I have never seen how to do that in general, nor seen a tool that would do that. Why?

update IEEE says:

  The rational transfer function is realized as a linear causal
  time-invariant system using well-established techniques

Which techniques to they have in mind?


texts: Can someone please explain to me in depth as to how this twin notch circuit is working. Also is what is the formula for finding the notch frequency  because some sites give the answer as (1/2×pi×RC) while the others as (1/4×pi×RC).


texts: A separate MCU to cutoff LiPo on low voltage?

texts:
I'm designing a project that is going to work on a flying quadcopter. It features an ATmega328P MCU in the main 5V circuit, and is powered by a small (<500 mAh) 1-cell LiPo battery. I want to provide low-voltage cutoff mechanism to protect the battery. Currently I'm considering the three options:

Just let the main MCU to monitor the battery voltage, using VCC as reference. VCC is usually 5.1 V, but to be sure I will also need to measure own VCC.

Pros: no additional circuitry. Can signal cutoff reason using a LED. Configurable cutoff voltage. Soft cutoff.

Cons: in case of malfunctioning of the main MCU (software bug) the battery voltage may be left unobserved under a high load. Complicates software. Requires powering the 5V network.
Use a Reset Monitor like MAX809. Power-down current is 0.5 μA.

Pros: highly reliable.

Cons: no signalling. Not easily configurable. Hard cutoff only. Additional circuitry (voltage divider).
Use an intermediate MCU like ATtiny25/45/85. It is tiny but can measure own VCC. Power-down current is 2 μA.

Pros: signalling. Configurable. Easy to test. Measures voltage before powering other things. Soft cutoff (can signal the main MCU that it's a time to gather stones).

Cons: requires additional (but very simple) software. Weight (1g?)

Option #3 is illustrated here:

I'm thinking of going with option #3. Does it make sense?


texts:
I'm in the process of learning about diodes and I'm currently learning about diode models. I came across the model called the constant voltage-drop diode model.
So, let's say the diode built-in voltage is \$V_{bi}=0.7V\$, which means the diode won't conduct forward current unless the source voltage exceeds the built-in diode voltage, or am I wrong?
My main question is: If the built-in voltage has a higher potential at cathode side of the diode and lower potential at anode side, as shown in this picture:

Why is \$V_{bi}\$ then shown like this in the model:

so that the voltage \$V_{bi}\$ is higher at anode side of the diode.
What am I missing?


texts: Can two 802.11n devices communicate via a coaxial cable?

texts:
Coaxial cables with RP-SMA connectors are often used as extensions for external antennas / with software defined radios.

What would happen if I were to connect two access points (wifi chips, via their antenna ports) using a coaxial cable? Would they be able to communicate? What should I take into account to not damage the devices?

I am trying to extract the angle of arrival from the channel state information reported by the wifi chip. Therefore I need to remove the phase shift introduced by the chips design. I can do this by measuring it, for that I need to receive a signal with the same phase at both antennas though. This is pretty hard in a multipath environment therefore the only solution I can think of at the moment is connecting both 802.11 chips via cable.


texts: Firstly, this applies to the UK - so 3 pronged sockets and 240V. Short and sweet question - should there be any voltage difference between the live and neutral prongs on a surge protector once it has been unplugged?


texts: Divide household power to multiple adapters

texts:
I'm working on a custom charging station rack which would allow me to charge 3 of my tablets simultaneously. I already have the rack and adapters setup for the tablets but it requires 3 different outlet plugs. I am looking into combining these into a single plug by wiring each adapter in parallel with the wall outlet. I never have strayed far from battery and microcontroller power sources before so in my mind household power is no different but surely the 120V is nothing to scuff with so my confidence is weary.

Would running multiple adapters in parallel actually work as I expect it? What would then be the best path to achieve this? What about if I ever want to extend to more devices? Any regulations or additional safety precautions for the circuit?

I live in the US and two of the adapters are the standard 5V-2A transformer, the other one is also not far off.


texts: How can I Build a Full Bridge Rectifier?

texts:
For further detail, I plan to extract an alternating current and convert it to direct current. Suppose that the AC flowed through the wires; how can I make it a direct current using the full bridge rectifier and use it to power electronic devices?

Thank you for your help.


texts: finding suitable substitute for 2n3904 transistor

texts:
i have to make a portable handly lie detector but i was not able to get a 2n3904.What substitute can i use?I have searched a lot and get to know that 2n2222,2n4401,2n2907,bc547 can be a replacement but i want to know a perfect substitute for 2n3904 transistor.

This is the circuit we're dealing with:


texts: TYPE-K Thermocouple wire to a thermistor

texts: I have thermocouples and thermistors on my job measuring temps. I accidently ran type k thermocouple wire to my thermistors. I am wondering if they will still read accurately or if I need to replace the wire with a 2 pair shielded conductor ? thank you


texts: Choosing between ipex connector and SMA Connector for LoRa, LTE and GPS

texts:
I have completed designing of PCB with LoRa (868 MHz), GPS and LTE (1800 MHz). Earlier version of my PCB had this SMA connector. But now the PCB will be placed in enclosure and I am thinking to replace PCB antenna connector with uFL or IPEX connectors (for LoRa, GPS and LTE).

The picture below shows the setup that I am planning to use:

The N-type Connector in the encircled part will be screwed in my enclosure and IPEX part of it will be connected to the PCB.

The reason of moving to this new setup as earlier PCB edge Right Angle SMA connector was difficult to make weather-proof and they were occupying a huge PCB space.

Can someone explain the advantages and disadvantages of using either setup? Is there any standard? Is there any difference in RF performance? Is there any particular setup which will yield better soldering or production efficiency ?

I would really appreciate if anyone could cover things that I haven't asked (possibly because I don't know) and save my time, effort and money.


texts:
I want to specify the scaling factors for my mosfet dimensions. How do I do it ?

I am following some beginner tutorials but they have done everything in HSPICE. I use LTSPICE. And LTSPICE doesnt seem to have a scale option.

I looked at all the options here:

http://www.gnu.org/software/gnucap/gnucap-man-html/gnucap-man042.html

But there's no option to specify scale factor.

There are DEFL and DEFW options but they dont specify scale.

How do I go about it ?

Thanks


texts: What is the difference in assigning output before end process and after end process in VHDL

texts:
I have written a code to check the difference in assigning output before "end process" and after "end process" in VHDL. And the results of the simulation I have posted with it.

What I found is assigning output
1:After "end process" there is no delay, output port is reflected with change in variable.
2:Before "end process" there is a pulse  delay.
but I'm not able to conclude it.

entity signal_delay is
port (clock_50M: in Std_logic;
        r: in std_logic;
        r_delay1, r_delay2: out std_logic);
end signal_delay;

architecture ada of signal_delay is

 signal r_1,r_2: std_logic;

 begin
     process(clock_50M)
     begin
        if ( clock_50M='1') then
            r_1<= r;
            r_2<=r_1;
        end if ;
     end process;

    r_delay1<=r_1;
    r_delay2<= r_2;

 end ada;

----case:2-------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity signal_delay is
port (clock_50M: in Std_logic;
        r: in std_logic;
        r_delay1, r_delay2: out std_logic);
end signal_delay;

architecture ada of signal_delay is

signal r_1,r_2: std_logic;

begin
    process(clock_50M)
    begin
        if (clock_50M 'event and clock_50M='1') then
            r_1<= r;
            r_2<=r_1;
        end if ;
        r_delay1<=r_1;
        r_delay2<= r_2;
    end process;

end ada;


texts: Do defective voltage regulators pass full voltage through?

texts:
I'm suspecting my voltage regulator is defective because I made the same circuit twice with the exact same components but this time, the battery voltage of 7.2V is being passed to the entire circuit when the rest of the circuit should only get 5V.

So when a voltage regulator is defective, does the input and output normally short together when its turned on?

The regulator I'm using is LM2940 with 22uF grounded electrolytic capacitors at its input and output.


texts: How much current can a tin solder track handle?

texts:
I'm working on a DIY project where I need to control some 9V solenoid valves with an Arduino.
I don't have the tools to make a PCB myself, so I chose to work on perfboards.
Now, I have to connect power supply (MeanWell ) to the step down regulator (Polou D36V50F9) that powers the solenoid valves, and I'm doing it with a solder track.
With a solder track I mean a connection between perfboard pads made with standard solder tin.
My power supply is capable of sourcing 4.5 amperes at 12, with a total power of 54W.

Can a solder track hadle all that power?
How wide should it be?
How thick?

Note:
My solenoid valves are latching, and this means that they need only a short pulse to open and close  (opposite polarity), and I can control them one at a time to minimize the current. But I want to be sure that my circuit won't burn in case the program does not work properly.


texts: Relay DC voltage rating, absolute or relative?

texts:
Is the dc voltage rating for a relay taken to be the absolute value on the high voltage terminal or the voltage difference between the input and the connected terminal?

To clarify, if the relay in the picture has a Vdc rating of 30V, is this circuit correct?


texts: Does this circcuit pose a safety risk that could be avoided?

texts:
I was looking over the circuit design for OpenEVSE. I was specifically interested in the GFCI portion of the circuit:

This circuit measures the current difference between Line and Neutral on a 120/240v 50-60Hz power source using a current transformer on the bottom two pins of the pin heade.

AFAIK this circuit triggers an interrupt on an MCU if the difference in current is larger than 20mA (50mA??).

I assume the 2 zeners are to avoid damaging the circuit from large current(voltage) spikes.

Both op amps are powered with +5v. It seems to me that this circuit will only trigger on the positive half of the AC wave. Since we are talking about 50-60Hz, this could mean there is a whole +/-25ms from the time where a short is created to when it is detected. Not to mention the time for the contactor to open...

I am wondering if I am overreacting and this is typical of GFCI circuitry. This circuit is usually hooked up to a 30+ amp breaker. Is my analysis correct? Is this an acceptable amount of delay to interrupt the power source in a ground fault condition?

My thought would be to have the op amps in an "absolute value" configuration and trigger on both halves of the ac waveform, saving up to 25ms.


texts: Can the Olimex ESP32-EVB be used in a commercial application?

texts:
My friend and I are very near a final product design, but we currently are using an Olimex ESP32-EVB relay module as part of the final system.

Recently we were told by a consultant that the FCC could potentially require us to recall any Olimex "ESP32 evaluation-hardware" due to it not meeting compliance or licensing requirements. We are afraid of having to recall many units in the future.

I would really like to know if a professional opinion could shed some light on this.

We are very worried that the Olimex ESP32-EVB unit does not meet FCC requirements for commercial use. On the product page under Important Notice they state:

  This evaluation board/kit/module is intended for use for ENGINEERING
  DEVELOPMENT, DEMONSTRATION OR EVALUATION PURPOSES ONLY and is not
  considered by OLIMEX Ltd to be finished end-product fit for general
  consumer use.

Does that statement mean it is absolutely not allowed to use this module in our product for commercial purposes?

We really like the ESP32, and the Olimex boards are great in our case because they include 2x mechanical relays packaged inside a metal box and a Rj45 Ethernet connector.

Please can someone help me understand why these Olimex boards would (or would not) be suitable in a commercial product or system?

I also wonder, how would the FCC be involved if the wireless radio were disabled completely (Ethernet only device) and/or if it had no antennas attached, could that help to reduce FCC requirements complexity?

Thanks and I greatly appreciate any insight,

P.S.
If anyone knows of a commercial grade ESP32 based Ethernet enabled relay module, I would really love to know about it!!


texts: Why skin effect happens at the center of a conductor?

texts:
I was reading an article about Skin Effect. I know what skin effect is, but I wanted to know what causes it.

Why is the back EMF strongest at the center?
Why is it not distributed uniformly at the cross section area of the conductor? so that, the main current is resisted but passes through both the centre and surface.

Here is the article I was reading: https://en.wikipedia.org/wiki/Skin_effect


texts: PIC32 Issue with using JTAG Pins as Analog Inputs

texts:
I'm trying to read in a value using a few analog pins on a PIC32 (MX775F512H), including RB12-- part of the JTAG pins on the device.  The device the board is reading from works great, but the board itself can't read the pin in.

I'm able to set the pin high using this code:

    DDPCONbits.JTAGEN = 0;
    TRISBbits.TRISB12 = 1;
    AD1PCFGbits.PCFG12 = 0;

I'm intending there to disable JTAG and then write all the pins to high.  RB0 through RB7 work as expected, but RB8 through RB15 float at a few millivolts.

How can I get my expected functionality out of these pins?  Any searching on here and on Google hasn't led to much, and the documentation isn't clear on what to do other than to disable JTAG.


texts: How to make a constant current source of 5 amps running through the load of 30 ohms

texts:
I have two batteries connected in series of each 12 volts and each rating at 35 AH.

I have tried with voltage multiplier boosting the voltage upto 150 volts so that the current could be climbed upto 5 amps but that didnt work .
Please give the solution for having the load current of 5 amps that runs through 30 ohms load and 24 volt input.


texts: Is the solder paste file necessary for through-hole components?

texts:
I have designed a PCB. There are only through hole components on the top layer, and only surface mount components on the bottom layer.

Is TOP SOLDER PASTE file necessary to send to the PCB fabricator, the same as bottom solder paste, or is it enough to only send the bottom solder paste file, since I only have SMD components on the bottom?

Also please explain, in general, in which situations do we have to send SOLDER PASTE file to the fabricator?

Thank you very much for your time.


texts:
I have this problem to solve where I1 = 6mA, beta=125 and Vbe =0.6V

So far I have solved the following,

a. How circuit works?

Circuit works as a stable output voltage source. This is caused by the negative feedback through the series resistor R2. If I1 increases then IR1 also increases, thus rising the base voltage of Q1. Since, Vbe is increased, thus collector current I1 is also increased, such the excess current I is shunted through Q1 reducing the effective current through R2 to maintaining constant voltage.

b. Output DC voltage
Ib = Ic/beta = 48uA

therefore, Vout = Vbe + VR2 = 0.6V + (100K * 48uA) = 5.4V

c. O/P impedance

I made the AC equivalent circuit as following,

simulate this circuit – Schematic created using CircuitLab

This means that Zout = 0 is it right?

d. One measure to reduce the Zout

According to my AC model of the DC circuit, Zout is 0 so why do I need to reduce it  more, Or I did something wrong in question c?

e. Typical disadvantage

Is it the shunting of I1 to maintain constant Vout when I1 increases?


texts: How to componsate for long power lines voltage drop

texts:
I have implemented a simple backup LED system. The system comprises a 12V 3.2A power supply, a small DB fuse box, and a 12V LED strip.
The system is working as expected. However, I noticed there exists a voltage DROP on the DB fuse box. The power supply output is sitting around 12.4V but the DB box is around 11.2V. The DB fuse box is about 8m from the power supply box and the LED strip is about 40cm from the DB fuse box. I used 0.5mm ripcord power cables.
The DB Fuse box just consists of a fuse in series with the power cable to the LED strip.
I was thinking in order to compensate for this voltage drop at the DB fuse box, I can use a basic boost converter to pick the voltage back to 12.4V then use the series fuse to connect to the LED strip. Is this thought okay or not?
The fuse box is just a plastic box (9x5x2.5cm). I am concerned just by the voltage drop between the power supply and fuse box. The wire is a 0.5mm ripcord and is 8m long. The LED strip pulls around 1.2A.
Reference for website: https://www.arb.co.za/ripcord-0-5mm-white-100m


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I am led to believe that this transistor came out of a (bass) woofer - one one speaker, and only one transistor (not two).

This is the best photo I can get:

The markings appear to read

L70M09CV
MCCO - 0031

Googling L70M09CV comes up with nothing related.

Any idea what it is, a datasheet, and/or a suitable alternative?

I don't have a photo of the PCB, as it belongs to a Thai friend, who speaks no English, and my Thai isn't fluent, so more details are either sketchy or non-existant. I may be able to get a photo of the PCB tomorrow.

FWIW, I get 0.6V across the collector-base and emitter-base junctions, when forward biased - when checking it and assuming it is an NPN transistor.


texts: Multisim - Struggling with a power supply circuit

texts:
I'm new to the website, I found it while trying to research the problem I'm having and thought I could just ask the experts directly :)

I am a student who is trying to design a power supply circuit (DC). I've used Multisim over the past year but I'm still not completely savvy with it.

I have some criteria to meet with the question, and it was going really well until I tried to view the Oscilloscope.

Secondary output voltage needs to be 12v, the DC Output voltage should be 10v, the Peak–Peak ripple voltage must be less than 1.2v, maximum full load output current of 0.5A, Over-current protection to be active at 0.5A and regulation must be better than 10%

At first I was getting the 12V, the 10V and the <0.5A current, but suddenly something just went wrong, I didn't change anything. The DC output voltage began to climb with no signs of stopping and went way over the 10v it was sitting comfortably at.

I would post more pictures but it says I don't have enough reputation points to do so yet. But the Oscilloscope was just straight and constant at zero when the voltage was consistent at 10V, and then (when the circuit did whatever it did!) the voltage started rising on XMM2 with no signs of stopping, and the Oscilloscope showed a large waveform which got smaller and smaller as the voltage increased.

I'm no expert as you can probably tell, if anyone could tell me what I'm doing wrong or how I can fix this I would appreciate it so much.

I'm sure I've connected something incorrectly or missed something out, but I've tried adding, removing and changing everything I can think of and I can't get it working.


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In my ASIC book they are developing a state machine, and they have a statement like:

 Shift <= '1' when State = S else '0';

However in my project I have multiple states that have the same output being required to turn on so is it possible to write VHDL like this:

 Shift <= '1' when State = S OR State = E OR STATE = Q else '0';

Or do I have to assign Shift for each of my states?


texts: Understanding "FFT" Can anyone understand what I have in the picture?

texts: I have a 15volt dc signal with an FFT on channel 1. I see a pulse on the FFT. Does this mean I have a voltage at a certain freg?


texts:
I have a LED strip and an ESP8266-12 to control it. As the LEDs need 5V I'm using an AMS1117 3.3V linear regulator to get the 3.3V needed for the ESP8266. The circuit works fine but when I try to establish a serial connection to the ESP by connecting an USB-TTL-Adapter the AMS1117 starts to overheat and breaks in the end.

The regulator starts to burn when the circuit is running and I connect the ground-cabel of the serial-adapter to the ESP. I'm new to electronics, so I don't know what happens here. Is there a big current floating from my laptops-USB through the regulator to the power-supply? How can I protect the regulator and prevent it from overheating?


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I have the following question about a cascade 555 timer circuit. The thing what I do not understand in this schematic how the second input trigger (2) is triggered for low condition. I know that the capacitor (see red arrow) will be discharged after the output (3) of the first timer goes low. But how can trigger (2) of the second timer see that output (3) of the first timer goes low, because it is connected to the negative (lower) side of this capacitor.

The first 555 chip is triggered when SW1 is depressed, taking pin 2 to ground.
This action takes the output on pin 3 to high, which lights LED1. Notice,
however, that pin 3 of the first 555 is connected through a small capacitor to
the trigger input of the second 555. As soon as the time interval expires on
the first 555, its output goes low, which turns off LED1 and at the same time
triggers the second 555, which in turn lights up LED2. LED2 stays lit until C2
charges, and then it goes out. The circuit then waits to be triggered again by
a press of the switch.