texts: Stopping a brushless DC motor in a specific position

texts:
I have a BLDC motor on an autopiloted model airplane, running with an ordinary PWM-controlled ESC.

I have a feature I'd like to add which the ESC I have doesn't support, so I either want to find one that does or to learn enough to build one that is integrated with the rest of my (mostly home cooked) autopilot.

The feature I'd like to add is a mode that stops the prop and holds it in a horizontal position (it is a 2-blade prop) both to reduce drag during glides and for landing so that the pusher prop on my flying wing won't be as easily damaged by the ground.

From what I understand of how these motors work, it should be possible for the usual 6-MOSFET driver circuit to hold the output shaft in any of 6 (maybe even 12, if you leave one high side and the other two low sides on etc?) positions. Of course, without sensors, I'm not sure if it is possible to get it to that position in the first place? (I mean, if the motor were entirely off and I just connected certain leads and left them on -- with appropriate current -- would the shaft spin to that position? Or might it not have enough torque to move at all from some starting positions?)

Has anyone tried this? Thoughts or advice?


texts: Toggle two LED status lights with two transistors

texts:
I have an input that is either floating, or grounded.

The switch is fixed, it's either open or closed. Ie, I can't replace with a double throw.

Here is the schematic / sim.

If the switch is closed, I want the lower LED to come on. If the switch is open, I want the upper LED to come on.

I feel like i'm pretty close, but that diode in there just feels wrong, and when the switch is closed you can see the upper LED stays on dimly.

Here is my second attempt.

This one has a pull up resistor for the NPN and it has a pull up resistor for the switch. But the upper LED still is slightly dimly lit.

How do I fix that?


texts:
In the circuit below what additions are needed so that charge will move from Ch to Ca, given that the charge on Ca can be higher that Ch?

In this system (see image below, it's a thought experiment for me at this stage), it is possible for the capacitance of the capacitor to dynamically change.

ps. this question is a simplification of an argument that occurred between two electrically inexperienced people, me being one of them.

Thanks


texts:
Since lower voltage means proportionally higher current for a given power, and higher current means more impedance, presumably having a lower voltage at the outlet means transmission power losses are greater than if a used a higher voltage.

How much more energy is lost per year due to the USA using 110V than if it used Europe's 220V? What is the dollar cost?

Assume the USA consumes 5 billion MWh per year, and 1 MWh costs $US0.20 to produce so total current (no pun intended) cost is $US1B p.a.


texts: LED is turned on directly after power up without a reason

texts: I am programming a PIC micro-controller to turn on an LED by serial communication. at first the program just works fine. But suddenly, when I power on the micro-controller the LED turns on, and remains on, and if I remove the +ve branch and reinstall it again everything works again fine as it should be. what is the reason for this problem? And how to solve it?


texts:
how does a table function work in LTspice?
In the LTspice library, it says,
table(x,a,b,c,d,...):
Interpolate a value for x based on a look up table given as a set of pairs of points.

I don't really understand what it means. Could somebody help me understand what it does?

For example,

.step param n 0 5 1

.param cc=0.01 ; delta

.param a1=table(n,0,0,1,1,2,0,3,0,4,0,5,0,6,0,7,0,8,0,9,0,10,0)

.param R1=2k*(1+cc*a1)

.meas Vout0 FIND V(out) when n=0

how do the above statements work?


texts:
I'm planning to make a custom LCD made. The LCD has 128 segments. Now, in order to drive it, I have two options :

Use 4 COM + 32 pins
Use 8 COM + 16 pins

The MCU which I'm looking at (STM8L052R8) has support for 4 COM x 28 (112) or 8 COM x 24 (192). Since I have 128 segments, If I choose this MCU, then I'll need to go for 8COM config (8x16 = 128).
Many vendors have flatly told me that the viewing would not be good, and given me advice that 4COM would be better to view. Since I've little idea what they mean, I need better understanding of why this is so. And how bad would this viewing angle be, apart from other issues which I dont know of if 8 COM is used.
My expectation is its okay if the LCD has to be viewed in a 45 degree range.


texts: How do you determine the orientation of both ends of a USB-C cable from the UFP device?

texts:
As the heading states, I would like to semi-passively detect the orientation of both ends of a USB-C connection. I understand that it is possible for the UFP and DFP devices to infer their own plug orientations, but how would the UFP device itself infer the overall cable arrangement?

I'd like to avoid having to introduce or use a high level protocol (ie USB 2.0 or something else). Low level manipulation of the CC pins or some other method would be acceptable.


texts: USB bus Differential signals and Pin swapping

texts:
USB 1.0 and 2.0 has D+ and D- two differential pins.

My understanding is that differential signals are symmetrical so any of the two lines carries an inverted signal of the other line.

But in the case of USB if I swap the two lines then the USB ceases to function. Is it because the USB lines are differential as well as tri-state logic also to reverse the data direction in them?


texts: PIC16F877A: Transmitting data but not receiving from Bluetooth module

texts:
I interfaced PIC16F877A with a HC-05 Bluetooth module using serial communication and I can transmit data from the PIC to my PC.  I connected my PC's Bluetooth to HC-05 Bluetooth module and in Tera Term or termite 2.9 I see the output.  However, when I send data from the terminal I receive nothing on the PIC. As per my code the data received by PIC showed by echoed back by transmitting the same.

My PIC code

#include <htc.h>
__CONFIG(0x2F0A);
#define _XTAL_FREQ  16000000
#define BAUDRATE 9600
void InitUART(void)
{
    BRGH = 1;
    SPBRG = ((_XTAL_FREQ/16)/BAUDRATE) - 1;
    TRISC6 = 0; // TX Pin
    TRISC7 = 1; // RX Pin
    TXSTA = 0x24;
    RCSTA = 0x90;
    //SPBRG  = 129;
}
void SendByteSerially(unsigned char Byte) // Writes a character to the serial port
{
    while(!TXIF) ; // wait for previous transmission to finish
    TXREG = Byte;
}

unsigned char ReceiveByteSerially(void) // Reads a character from the serial port
{
while(!RCIF)
    continue;   // Wait for transmission to receive
return RCREG;
}

void SendStringSerially(const unsigned char* st)
{
    while(*st)
        SendByteSerially(*st++);
}

void main (void)
{
    unsigned char SerialData;
    unsigned int i;
    TRISB=0x00;
    PORTB=0xff;
    InitUART(); // Intialize UART
    SendStringSerially("Hello World");
    while(1)
    {
    PORTB=0x00;
    for(i=0; i<100; i++)
        __delay_ms(10);
    PORTB=0x01;
    for(i=0; i<100; i++)
        __delay_ms(10);
    SerialData = ReceiveByteSerially();
    SendByteSerially(SerialData);
    }
}

In the while loop I blink a LED for 1 second if any data is received.


texts:
I've been bashing my head against a wall for the last day trying to get this to work.. I have a custom schematic and pcb library, when I try to update my pcb document I get the following error:

I have checked both the schematic symbol and the pcb footprint about a million times and am certain that I have correctly designated the pins.

I have learned a little bit about using Altium at university, and I have had some success using custom schematic/pcb libraries in the past but for some reason I just can not get this one to work. I've done some searching on the forums for this error but have not yet been able to find a solution that worked for me.

Any ideas/suggestions are welcome! Thank you

EDIT:
This is the schematic:

here are the properties of pin 2:

and here is the PCB footprint:


texts: Model for small signal - 3 transistors JFET

texts:
Could you tell me if the models for small signs are well made? And if they were not, you could tell me what I missed, please? Thanks.

\$V_{dd}=17 \,V\$

\$IDSS= 8 \,mA\$

\$V_P=-3\$

\$r0=30 k\$

\$cgs=5 pF\$

\$cgd=2 pF\$

\$R_L=10 k\$

\$R_G\, (resistance \,\,of\,\, the\,\, input \,\,signal) = 100 k\$

For the first transistor:

For the second transistor:

For the third transistor:


texts:
I have seen multiple designs that reference the RF on layer 1 to layer 3 with a cutout on layer 2, on an 8 layer board. All the calculations work out (using Qucs and Saturn) so the impedance is 50R. My question is why not made the L1-L2 distance a little larger so the sums work out?

It would simplify the layer stack considerably especially when adding RF on other layers using stripline.

On the same topic, what are the constraints when deciding track impedance? There are a lot of combinations of track width, layer gap and plane pullback that will give 50R. Do I set the desired track width and go from there?
Any papers on this topic would be appreciated.


texts: Can a system with more than 180 phase lag ever be stable?

texts:
For a system to be stable you must not reach a phase of 180 degrees before gain reaches 1 (for an ideal system). The layman explanation I was offered was that otherwise, your negative feedback becomes positive and you just built an oscillator.

What if you created a system (ie 4 poles H(s) = 10^100/(s-10)^4 that underwent a phase change of -360 and then limit inputs to the system to be >Fmin (which is the frequency after the phase changes). Would the system be stable for these inputs Fin > Fmin?


texts: Use SFP modules for HDMI or Dp TMDS line

texts: I just wonder if it's possibile to take four SFP modules and connect them dirrectly to TMDS lines of HDMI output and send such signal via four fiber to other similar end? Is it doable?


texts: A few questions regarding the functionality of this negative peak audio detector

texts:
I have some queries regarding this peak detector from an audio compressor circuit:

My understanding of the process is that when the positive input swings low, D5 is negatively biased and stops conducting whereas D4 is positively biased so the input of the op-amp sinks current and charges C1 down to a negative voltage. During this period there is no negative feedback so the output of the op-amp goes into negative saturation.
Once the voltage across the capacitor becomes equal to the input voltage, the inputs of the op-amp become equal and the op-amp stabilises. The image below shows a simulation of the circuit in which the input voltage drops from 0, to -1V. Why does the output of the op-amp (purple trace) stabilise at -0.6V?. I note that this is equal to one diode drop voltage, but can't see why this happens.
Also, it's not visible on this image but over time the op-amp output slowly drops down to become equal to the input voltage, but the circuit is static, so why would there be current flowing to cause the voltage to drop?

Finally, given that this is a negative peak detector, aren't these capacitors in the wrong direction? If they're being charged to negative voltages, shouldn't the anode be connected to ground?


texts:
I have a situation that just baffles me here...

I bought these cheap XY-MK-5V RF receivers with FS1000A transmitters. I fitted the receiver to an Arduino UNO connected to an 8-channel relay board, ready to go. The transmitter is attached to an Arduino UNO that would be connected to a home automation control system of some sort.

The transmitter has a single-core 17.2 cm insulated wire attached as an antenna. Same goes for the receiver, except that I accidentally pulled of the insulation and now it's just a single-core 17.2 cm "naked" wire. I use RadioHead (successor to VirtualWire) to handle the comms between the RF units.

And suddenly the receiver just stops working. Here's how it went:

Tested Arduino-to-Arduino transmission using VirtualWire, it works.
Tested Arduino-to-Arduino transmission using RadioHead, it works.
Boosted transmitter operating voltage to 12V to increase range, it still works. (I used a XTW-SY-8 unit here)
Modified transmitting Arduino to act as MQTT client (I also added an Ethernet shield at this point), and tested sending messages via MQTT broker installed on my RaspberryPi unit; it still works.
I modified my MQTT broker to be a little bit more secure by adding a username and password, it still works.
I installed OpenHAB on my RaspberryPi, configured some stuff, and got it to send messages via my MQTT broker. It FAILS! Note: The MQTT message topic, format, and content, are exactly the same.
I went back to sending direct messages from MQTT without using OpenHAB, and it still won't work.
I tried reprogramming the receiver Arduino, still won't work.
I tried switching the receiver unit with a new one, and it still won't work.

Has anyone ever experienced the same thing? I'm really baffled here. Both the receiver and transmitter is in my room, about 5 feet apart from each other, if that matters.

I'm really out of ideas, and any help would be much appreciated.


texts: Choice of the appopriate conditional statement

texts:
I'm measuring the width of a PWM puls with the external interrupt:

void interrupt ISR() {

if (INTCON3bits.INT1IF) {                   // INT0 interrupt
    if(INTCON2bits.INTEDG1) {               // Rising edge detected
        T1CONbits.TMR1ON = 1;               // Start TMR1
        INTCON2bits.INTEDG1 = 0;            // Swap edge
    } else if (!INTCON2bits.INTEDG1) {      // Falling edge detected
        T1CONbits.TMR1ON = 0;               // Stop TMR1
        INTCON2bits.INTEDG1 = 1;            // Swap edge
    }
 INTCON3bits.INT1IF = 0;                    // Clear flag
    }
}

I want to store the width of the current pulse and the width of the next pulse. By width I mean the TMR1 value[hex], not a time value [s]. How and where should I do this?

Something else: If these two pulse values are the same I want to do 'something1', if they are not then I want to do 'something2': Looks like this:

if (current_value == previous_value) {
     Do something1; // if entered here, I will start UART communication and keep reading incomming data constantly, so I suppose this is a dead end.
 } else {
     Do something2; // if entered here, there is no need of pulse measurment anymore
 }

But while in this if routine I want constantly check for the pulse width, how can I do that? I thought of a do-while routine, but not sure about it too.

I'm working with pic18f25k80, using MPLAB X if this is important


texts: Driving multiple optoisolators, with fault detection

texts:
I'm building a board controlling external stepper motor drivers that have optoisolators (with integrated resistors, these are meant to be driven with 5V and consume 13mA then) on their inputs. As the external boards are connected via cables that may be accidentally disconnected or shorted, I'd like to verify that there is indeed a LED connected on the other side. The signals are generated from an FPGA, so I have a bit of flexibility in the implementation.
Idea 1: Constant-Current 16-Output LED Driver IC with Fault Detection
This integrates everything in a single package, but it seems all of these ICs need data to be shifted in serially (which reduces the number of I/Os required, but adds complexity in the FPGA design). These seem to detect faults only when the channel is active, which is probably good enough, but could be improved. I'm not sure how well these detect faults if a series resistor is present.
Idea 2: 16-Channel Driver, High-Impedance Current Measurement, Comparators
A driver outputs a 0 or 7V signal, 2V drop in a series resistor, then the voltage is compared to 6V and 4V. Above 6V, the connection appears to be open, below 4V, the connection appears to be shorted. The series resistance protects the driver.
Fairly simple logic, detects faults while the LED is on. Downside is that it requires 48 IO pins on the FPGA and 32 comparators (but banks of comparators should exist) for an error condition that should essentially never happen.
Idea 3: "Open-Collector"
A colleague suggested an open-collector system, where I would run the IO pins essentially in bidirectional mode, and drive either 0V or go high-Z, at which current would flow to the LED through a pull-up resistor, however I still haven't quite understood how I could detect a broken connection this way (shorts are easy: while not pulling down, I can set the IO to input mode and check that it is high). Broken connections are more likely than shorts in the wiring.
Are there simpler approaches how I could control 16 optoisolators and detect wiring faults on the way to them?


texts: Maximum battery charge current by technology

texts: I know the exact values depend on the specific battery used, but is there a general rule for the maximum charge current (as a function of the battery capacity) for each of the mainstream battery technologies (NiCd, NiMH, Li-ion, Li-Polymer, lead-acid), for normal and fast charging? The typical capacity I'm going to use is 10 - 40 Ah.


texts: Why is the metal tab of a BJT power transistor is always connected to its collector pin?

texts:
Until now I thought the metal tab of a BJT power transistor is connected to ground but it seems like it is connected to its own collector pin´as shown in the below illustration:

Is there a particular reason for this?


texts:
Again I Have a question regarding Bridge Rectifier's Made using 4 Diodes

if I use 4 pieces of 1N5408 with rating of  3 amp in Bridge mode what will be current rating or handling capacity of rectifier ,does its rating will increase or will be same as single 1N5408


texts: Connecting the FSR sensor with the plunger rod as to transfer the full force

texts: I am using FSR sensor for force measurement, I am using rod plunger to transfer force to the other side of the rod which is connected to the FSR sensor. The force is not going to the active area of the sensor, it varies each time when I am pressing the sensor. Does the force has to be applied to the single point in the active area or whole active area, I am not able to find this information in the datasheet. I am thinking to connect the gasket or some packing material between the sensor and the rod. I have done some experiments with the 1mm acrylic sheet but not sure about the results. Is there any standard material/method which is used for connecting the sensor with external rod, so that full force can be transferred to the sensor.


texts:
I'm in a bit of a quandary as to if I've approached something the right way or if there's an obvious solution I'm missing.
(Sorry for lack of schematic, still WIP).
Goal:
Self-powered isolated USB > UART adapter with RX @ 3.3V and inverted TX signal @ 12V.
(Weird, I know)
So far:
Starting off with an FT232RL @ 5V.
CBUS#4 (SLEEP) on the FT232RL going through a NOT gate (SN74LVC1G04) - more on this later.
ADuM5401 isolator with integrated DC-DC doing 5V > 3.3V.
5V, TXD, RXD and the now inverted SLEEP piped through the ADuM.
(So far so good)
For the 12V feed, I thought an inductor-less charge pump like LTC1263 would be a good choice.
However this requires 5V and on the isolated side I now only have 3.3V (the level RX is working at)
So I then figured adding an LTC1751-5V would get the 3.3V > 5V > 12V - I don't need much current so efficiency isn't critical.
Then tying in the isolated SLEEP signal to the shutdown (SHDN) pins on the LTC1263 and LTC1751.
And ultimately shifting the 3.3V TX signal upto 12V with something like a MMBT3904 which also achieves the inversion. (Welcome to suggestions on alternatives!)
Alternative thought was to drop the LTC1751-5V, throw 5V through the ADuM and then use an LDO to get a 3.3V source on the isolated side and chuck a BSS138 (or similar) to handle the 3.3V > 5V pre ADuM for the RX.
Any thoughts much appreciated!


texts: Where finite-state machine code belong in µC?

texts:
When I learned about micrcontrollers, teachers taught me to always end the code with while(1); with no code inside that loop.

This was to be sure that the software get "stuck" to keep interruption working. When I asked them if it was possible to put some code in this infinite loop, they told me it was a bad idea. Knowing that, I now try my best to keep this loop empty.

I now need to implement a finite state machine in a microcontroller. At first view, it seems that that code belong in this loop. That makes coding easier.

Is that a good idea? What are the pros and cons?

This is what I plan to do :

void main(void)
{
    // init phase

 while(1)
 {
    switch(current_State)
    {
    case 1:
        if(...)
        {
            current_State = 2;
        }
        else(...)
        {
            current_State = 3;
        }
        else
            current_State = 4;
        break;

    case 2:
        if(...)
        {
            current_State = 3;
        }
        else(...)
        {
            current_State = 1;
        }
        else
            current_State = 5;
        break;

And this code goes on...

I ask the same question in stackOverflow to get some more detail.


texts:
simulate this circuit – Schematic created using CircuitLab

What voltage needs to be applied at \$V_{\text{in}}\$ for the LED to turn on?

My answer:
\$V_{\text{in}} > 9\text{V}\$

Is this correct?


texts:
I was asked to write a verilog code about the SLE shown in the picture above.
I have wrote the code until satisfying the condition of LAT=0, however the other half of the truth table I couldn't satisfy (I thought of making 2 always block that acts as a mux between the latch and the flip flop).
Can anybody can help me out or explain to me how can I implement it?
module question10(D,CLK,EN,ALn,ADn,SLn,SD,LAT,Q);
input D,CLK,EN,ALn,ADn,SLn,SD,LAT;
output reg Q;

always @(posedge CLK or negedge ALn)begin

  if (~ALn)begin
              Q<=!ADn;
           end
  else if (EN) begin
              if (~SLn)begin
                 Q<=SD;
              end else begin
                 Q<=D;
              end
        end
  end
endmodule


texts: Why does Vivado creates two muxes from this Verilog case statement?

texts:
This is the code:

always @(*)
  case(NormalCtrl[7:6])
    2'd0: TrigA = 0;
    2'd1: TrigA = TrigAA;
    2'd2: TrigA = TrigBA;
    default: TrigA = TrigA;
  endcase

This is the resulting RTL schematic (Vivado 2015.1):


texts: Small low frequency magnetic field measurement: soft iron or ferrite coil core?

texts:
Disclaimer: I'm just computer scientist.
I'm planning a simple experiment that uses a coil to measure a small varying magnetic field. How small ? I don't know yet. I'm exploring the unknown. All I know is that other people claim they made it with a 300 Ohms coil that had a 6mm diameter soft iron core. That is all the information I have. I don't know the wire gauge, the number of turns, or the coil dimension.
In order to try reproducing this experiment I would like to know if I should better use a ferrite core or an soft iron core. The frequency are low, below 20kHz.
Another question is the diameter. Will I gain in sensibility with a larger core diameter ?
It is surprisingly difficult to find soft iron cores. I found some in China and the smallest diameter is 10mm. I found ferrite cores of 8mm diameter.
I know that soft iron is easier to cut at the right dimension. I read that ferrite falls appart when we try to cut it with a conventional saw.
A last question is if the inductance of a coil is a directly linked to the sensibility to varying magnetic field. In other words, may I assume that the higher the inductance, the more sensible to magnetic field my coil will be ?
EDIT The output voltage of the coil is described to be in the microvolt range.


texts: Best communication option for multiple arduinos?

texts:
My father and I want to develop a cow pedometer to measure a cow's activity. The idea is that if you can measure a cow's activity you can detect when she enters heat. Detecting heat with sensors will help us increase the probability to choose offspring sex depending on insemination time since heat detection, and increase insemination rates since we are not relying on humans to detect cows in heat.

Commercial options are too expensive for us so we have decided to develop the sensors ourselves. I have no EE background, just CS. I come to you for guidance on how to proceed with the project.

Project background

We want to create a pedometer that can be attached to a cow's feet and is powered by a battery. The pedometer must be able to send the accelerometer's data to a central system for data logging and processing. The maximum distance a cow can be from the central system is 1.5km. There are about 400 cows. The farm is on flat ground and doesn't have a clear line of sight (trees block the sight, although it's just a few of them). We also have a mountain overlooking the valley where the farm is (maybe to but up the main receiver?) SEE FARM MAP. Trees in green, farm limits red, circle of radius 1.5 with center in house covers the whole farm.

Here are the questions I have, any question you could give feedback on would be great.

How can I achieve a low power long range transmitter? I suppose it will be low bandwidth (only sending sensor id, x accel, y accel, z accel)

Are there any available systems I can use to reduce development time?

At first I will be prototyping with Arduino.


texts: Why in semiconductor studies, we are only concerned with reduced zone representation of e-k diagram?

texts: Does electron transition from conduction band to valence band takes place only in first Brillouin zone? Or can it happen in any other Brillouin zone?


texts:
My imaging system currently produces a stream of digitized video data at 10Msps. That is, parallel 12bit ADC output at 10MHz. The next step is to collect the data in 1024*1024 chunks and perform image processing on it. With pauses, the frame rate is about 0.25s. Thus, the data for the new image is ready every 0.25s. The image processing might involve many complicated operations (not known yet).

Where do I start? What embedded systems would be most suitable for my application? I found several similar question like this one, which suggested embedded systems such as DSP uCs, FPGAs, other mini computers based on Windows (if I understood it right). However, I wish to hear more speculation on device selection.

I doubt I could keep up with the frame rate and perform real time image processing, but it would be great to find a solution that will have a reasonable performance speed (close to my frame rate) as well as good price, ease of implementation, the size, etc.


texts: Say if i use 5x eneloop AA batteries to run 6x MG996R servo, will it be good enough since im afraid for the motor if it will burn out. I already read the spec sheet what im afraid is the stall current


texts: How to measure capacity of a Lithium-ion battery

texts:
I bought a Lithium-ion battery for a camera (much cheaper than the brand replacement but non unreasonably cheap compared to AAA Li-Ion batteries with similar charge). I however have doubts that it has the capacity it claims on the package (in mAH). Is there a simple way for me to roughly verify the claim on the package which is more precise and less time consuming that to run some benchmarks with the camera and a comparison battery? I.e. is there some device / method that given a a Lithium-ion battery which is supposedly fully charged determines:

Is it actually fully charged
What is its current charge in mAH


texts: Why won't the bandstop filter work in this circuit?

texts:
This is the EMG circuit I designed.
The cut off frequency of the bandpass is 20-3k Hz. This somehow worked already. But the bandstop filter doesn't show. Why is this?
This is the freq-vout graph and the resulting figure. The same thing shows in ac sweep.

What changes should I do?


texts:
I have a PIC18F46K22 and program it with the XC8 compiler. In the end, I'll have a system like a pc with stdin and stdout. So in the main loop there will be a function which is checking if there is new input. If there's input, a function will be called accordingly. So for example when I input an A on stdin, the PIC will run a function like function_A instead of function_B which is called when I input a B.

When the PIC is done with the function, I want that the new input is sent to the function. So when pressing A opens the RS232 transmitter, from that moment every input will be sent over RS232. In the end the project is a stand-alone text editor. So when pressing A opens the file system, from that moment you aren't text editing anymore but looking through a list of files. That means that pressing Up and Down means something different than in the text-editing environment.

I've done a lot thinking on how to program this in C. I thought this up last night and would like to know if it's possible and if so, how. What I want to do is:

The main function calls a function like function_A
function_A changes a global variable function_addr to the address pointer of function in_function_A
From that moment, main calls the function at function_addr when there is new input.

So what I'd need is a main function which checks if function_addr is zero. If it is, a 'normal' function should be called, like function_A. If it isn't, the function at function_addr should be called. I also need a function_A which changes the function_addr to a pointer to in_function_A.

Note: when the filesystem function should be closed, is_function_A should just change function_addr to 0.

So basically my question is how can I

Get the address of a function (and store it in a variable)
Call a function at a specified address


texts: How to determine system order with degeneracy?

texts:
We know that system order is determined by the number of capacitor and inductors (minus the number of capacitor loops and inductor cut sets). Thus, the system is related to number of independent states.
Let's take simple example with LC circuit and ideal current source in series.

The state of inductor current is already determined and it is equal to the value of current source (some sort of inductor cut set). This would than mean that this circuit is first order. However if voltage source is connected the order is 2. That is a bit confusing for me. Am I missing something?
Another example would be the voltage generator with tow capacitor in parallel. I know that this is idealised circuit, but by theory this would be circuit with order 0. If Heaviside excitation is applied to this crcuit, Dirac impulse of current would be appear.

Thus, my question is: How to determine order of these degenerate circuits?


texts: Mulitple switches connected to one pull-up resistor vs separate resistor for each

texts: I have 16 SPDT switches to be used as the address inputs to a UM61512A 64Kx8 CMOS static RAM module. I have designed the circuit to have separate 10k pull-up resistors to +5v when each switch is up and a direct to GND connection when the switch is down. As I was getting ready to solder it all up, it seemed redundant to have 16 pull-up resistors. Are there any issues with just using a single pull-up resistor and connecting all of the switches' up connections to it? Maybe connecting groups of four switches each to a single resistor - thereby only using four resistors? Are there any advantages/disadvantages to these methods?


texts: 4 or 5 Time Constants to reach practical potential?

texts:
While I'm aware that a component can never "fully" charge or discharge to 100%, one textbook I'm using (Practical Electronics - 6th Edition, Sinclair, Dunton) says that we can assume a component has reached roughly its full practical potential after 4 time constants. Another source (allaboutcircuits.com) says that it takes 5 time constants for a component to reach its potential.

I understand that 4 time constants equal roughly 98% of capacity and 5 time constants equal roughly 99% due to 63% of value being added every time constant, but one is telling me to assume component has completed charge after 4, another tells me 5. This makes it confusing when calculating time for component to reach its capacity (difference of 25%).

Which is right?


texts: This is probably a simple question but how come CMOS Logic Gates built from Only Transistors is completely different from one that uses TTL Logic (Like BJT's). I know BJT aren't really used anymore because they consume power when they are "on" as compared to the low amount CMOS used.....but shouldn't the "Schematic" to produce a Gate be the same?


texts: Operational amplifier with reverse diode

texts:
On the first picture is a simple schematic. For example, we can get the transfer function simply by equaling
"ud+u2" and "Ad*(u1-u2)".
The transfer function is: u2 = (Ad*u1)/(1+Ad) - ud/(1+Ad)

On the next picture, that diode is turned in other direction.
I am not sure how can I get transfer function. My logical explanation (which is probably wrong) is that the diode does not conduct any electricity, so the current there is zero.

I am asking for the explanation, when and why do we have a voltage on u2 (on the last picture).


texts: Understanding the voltage across the inductor in a boost converter

texts:
I am studying boost converters in my power electronics class.  Something I cannot wrap my head around is the voltage across the inductor.
When the low side switch (the switch connected to ground, see diagram below) is closed, the circuit is just an inductor in series with a DC voltage source. According to every reference I can find on the internet and an LTspice simulation I downloaded from my professor, the voltage across the inductor is just Vi and stays at Vi for the time that the low side switch is closed. This makes sense according to KVL - the voltage around the loop has to equal 0 one way or another.
However, wouldn't the voltage be changing? If we just take the simple circuit of a DC voltage supply in series with an inductor, eventually after some time, the voltage across the inductor would just equal 0 and the source would be shorted to ground, right? So why is it different in a boost converter? What makes the voltage across the inductor stay constant at Vi?


texts: PSpice, collector emitter voltage is way too big

texts:
I'm trying a few exercises with transistor circuits that are later to follow with an amplifier circuits exercises, but although I'm following the instructions that my university has provided and theoretically all the numbers are right, in the PSpice the circuit doesn't quite come out right.

We are to assume the Ic would be 2mA and for the Ve to be 6V, and I calculated everything else according to that, but then Vce seems to be intent on being almost the whole source voltage. Also, I'd hoped for the Ib to be between 4-5uA, so I guess everything just went wrong. I even tried to recalculate both R2 and R3 by assumption that the voltage across R2 is 5.3V ('cause if there would be 5.3V across R2, then Vbe assumed to be 0.7, then the 6V across the R1, that would add up) and its current to be I while R3's current to be I-Ib, but I still got the same values.

I tried doing another exercise, one that I'd done before at a university computer instead of my own laptop, just to check if maybe this one circuit is being wonky, but the same thing happened, Vce ended up being over 75% of the source voltage, while I clearly remember that circuit working alright when I'd done it before.
Can it be something to do with the PSpice model parameters? It even says that the Bf is 416.4 by default while in the transistor's datasheet its maximum is 300, so maybe something else went wrong in there?

Or what are the other ways to make PSpice to listen when I need the voltage across R1 to be 6V and the Ie to be close to 2mA? Any tips? Any advice? What did I mess up, what do I fix?


texts: KiCAD - Automating library part creation

texts:
I started a project in EAGLE, however found that the free version limits were too restricting. I then moved to KiCAD. I am trying to create a 144 pin chip as a library component for use in Eeschema.

In EAGLE I created commands from a spreadsheet using the datasheet so I could just copy and paste them into the command line. The commands designate the type of pin (power, I/O etc) pin name, pin number, position, orientation etc.

Is there any way of automating the creation of a library in KiCAD? I have spent a day or so going through the Eeschema manual but if the explanation is in there then I definitely missed it.


texts: How to write SPWM program for 5 level inverter in arduino

texts:
I am making an 5 level inverter using arduino so for that i have written simple arduino program for switching the mosfet but problem i am facing in this is it has low switching frequency so i want to write program using spwm technique now i dont know where to start can any one help me out.
This is the simple code which i had made.
https://pastecode.io/s/M3j3iQV0o2


texts:
I need to trigger a 555 timer IC in astable mode as soon as it has power. It CAN NOT be done manually through a negative pulse like it usually is. The solution must be compact as space in my project is certainly at a premium. I either need a method of converting a constant high to a negative pulse, however this would require other components, or another method of triggering it. If neither are possible, is there an alternate astable IC I can use which would enable me to provide a 60s mark time followed by 1s space?
Thanks in advance for your time,
Regards,
Eerf


texts: What would happen if you accidentally switched live and neutral

texts: Short and simple. What would happen if you accidentally switched the live and neutral wires when wiring your home electricity into the distribution board?


texts: can I get noise of 24G with accelerometer configured at +-16G

texts:
I'm using lsm9ds1 accelerometer configued to +-16G. by reading raw data, I've got a value of 24G which I think it's a noise. I didn't configure any filter on the accelerometer.

can a noise reach 24G even when the accelerometer is configured at +-16G

vertical scale in mg


texts: Is it necessary to protect old devices against "new" 230V?

texts:
So, i was recently listening to old automatic music playing machines. These are devices from the year 1910 +/-. They are most likely purposed for 220V European power net.

To me, most of the machines sound like they are speeding trough their song and dance way too quickly.

An example is here: https://www.youtube.com/watch?v=3eBdKztfSHk
This machine plays singing in the rain, and is the fastest rendition i heard to date.

So this made me wonder, does our current power net have something to do with this? Is it necessary to "downgrade" our power net for these kinds of machines to get their original experience, or would it be for a different reason?

In general, besides faster wear and tear that i can find documented on wiki's. What else affects old electrical devices on our modern power net?


texts:
I'm new to all this. I'm trying to design a power supply. I need 3.3v, 5v and 170v outputs.

Does this look OK? Are there any issue I need to fix? Is there any advice you can give?

Update

Ok, based on the comments I've come up with this, based on this:


texts: I have a solid state relay which wants a 1.25-2.5V "activation" input, but my output from the micro controller is 5V. Is it possible to use a zener diode for this? Or do I need a buck converter? I don't know how small/big the resistance or current through the relay is, but if I knew that I could perhaps use a parallel resistor with a lower resistance? Perhaps there is a better way?


texts: How to measure only the true RMS AC component of the waveform in an ADC?

texts:
I need to read an AC signal on an ADC. I have already conditioned the signal with an offset of 2.5V, which will vary from 0 to 5V.
How to calculate the Vac true RMD voltage of any signal (sinusoidal, square, triangular) and, when the AC signal is not added to the 2.5v offset, the result of the calculation must be 0?
I've tried to rectify the signal by processing the data from the adc and creating a virtual offset of 2.5 V, but I would not like to use a virtual vmed.
In short, what I need to calculate is only the true RMS AC component of the waveform, disregarding the DC.


texts: What exactly does it mean to be a lower rate LDPC code? Is the ratio of information bits to parity bits being decreased? For instance, (128, 64) ldpc code is a higher rate than (90, 30) ldpc code? It is stated that a lower rate ldpc code is stronger. Thus, if I am correctly understanding the difference between lower and high rate ldpc codes, than why is a lower rate stronger? Isn't the code stronger as the number of parity bits increase? Sorry, I am kind of confused on this. Please let me know if I should clarify anything.


texts:
I have a book statement:

  A content addressable memory is a circuit that combines comparison and storage in a single device.

I want to know how this is implemented in real world? Sounds like an bitwise-and(&) which does the job in instant? But won't this cause the size of the circuit increase?


texts: What is the right-most component in this picture?

texts:
I'm reverse engineering an old RF transmitter circuit and I can't seem to figure out if the right-most component is a 3 band resistor (+/- 20%) or a capacitor (as the label on the board would indicate).

If it is a resistor, my best guess is that it is 380 ohms. Otherwise, I'm completely at a loss.


texts:
Raspberry Pi has 3.3V I2C bus without any protection against overvoltage. So, I want to add protection against an accidental 5V level on the bus. How to do it?

My two tries:

simulate this circuit – Schematic created using CircuitLab

Is it OK, what is better, what there are other solutions? Does serial resistors (R1, R9) make a problem for I2C communication? What is recommended value for it?

Note. I need not a level convertor. I assume that all I2C slaves has 3.3V levels. 5V maybe on the bus only for accident.


texts: Why are the green traces thick at the peaks of the cycle? What causes this ‘roughness’ in the oscilloscope reading?

texts: This is probably a very basic question but I could not find the answer to it online. I just want to make sure - is the roughness caused by electromagnetic interference?


texts:
I am trying to setup a simple blinking LED on a PIC18F25K50.  I can get RA0 to toggle using

LATAbits.LA0 = ~LATAbits.LA0;

However, if I try to use

LATAbits.LA0 = ~PORTAbits.RA0;

The LED stays on.

According to the datasheet (among other sources), the PORT register reads the levels on the pins, whereas the LAT register sets the output.  Why is the PORT register not reading the correct levels?  The circuit is below.

simulate this circuit – Schematic created using CircuitLab


texts: Why do 18650 batteries with lesser capacity (mAh) produce higher Amps?

texts:
Sony VTC4 IMR 18650 High Drain Flat top (2100mAh, 30A)

Sony VTC5A IMR 18650 High Drain Flat top (2600mAh, 25A)

LG HG2 INR18650 High Drain Flat Top (3000mah, 20A)

Sony VTC6 IMR 18650 High Drain Flat top (3000mAh, 15A)

Would it not be vice versa?


texts: How does i2c standard or fast mode effect the output data rate of the sensor?

texts:
I am using BNO055 motion sensor supports standard mode 100kHz and fast mode 400kHz

but sensor specifies following

Gravity Vector 100Hz

Euler Vector, 100Hz

Quaternion, 100Hz

Magnetic Field Strength Vector (20Hz)

How do they change from when 100kHz vs 400kHz?

What is the actual use of those two modes?


texts: Raspberry Pi as basis for commercial device?

texts: I am thinking of using a Raspberry Pi as the basis of an electronics project that I am working on, and plan to eventually sell to the public. I want to use the Raspberry Pi in order to reduce the development time and development complexity of the device. As a general statement am I better off taking the time, developing an ARM based system that runs Android, or should I just use the Raspberry Pi?


texts:
I have a question regarding finding poles by inspection. The technique that I know is

Find the resistance R tied from the node to AC ground.
Find the capacitance C tied from the node to AC ground.

The pole can then be approximated as 1/RC.
Now, with that mind, consider the following circuit:

Consider the input pole (gate of M1). The capacitance tied to AC ground is C1 and the input impedance of M1 is extremely large. Does that mean that the 1/RC pole is extremely low? I see most books usually place an additional external resistor at the gate of M1 to calculate the pole, they don't take into account the input gate impedance of M1, why?
Thanks.


texts:
Several of my devices with 3.5mm jacks make unreliable connections. The sound will cut out when the plug is wiggled slightly, or one ear will not have sound at all, or the sound will "cancel" in a way that seems to remove center panned audio but keep left- and right-panned audio. It seems to be a function of the jack and not the plug. Often it will get worse with device age.

What causes this unreliability? Also, bonus points for answering: Is there a way to repair damaged jacks and restore reliable connections?

Some guesses for why this might happen:

Different manufactures have different specs/tolerances.
TRS jacks don't precisely mate with TRRS plugs or vice versa.
The spring mechanism (for tension fit) is located in the jack, so the jack tends to wear out faster than other connectors (compare to USB, HDMI, and DisplayPort, which put the spring mechanism in the plug).


texts:
I am using LM139 comparator
There are two stages of the circuit:

First stage is amplifier stage
Second is comparator stage

I apply input signal of 1.098Vac to noniniverting input of LM139 comparator.
Reference voltage for comapartor is 0.5Vac.

Now as 1.098 v is higher than 0.5volt(ac), output of comparator should go high and vice versa.

If input is 0.2volt AC, output should go low driving led, but it is not working.

LED is off in both case.

Is this circuit right?


texts: Are these two equivalent? Z is characteristic impedance of the transmission line and theta is electrical length of it.


texts: How to calculate the resistance of a complicated circuit?

texts:
I learned in high school the basic rules of how to compute resistance between two points, given a network of resistors.  You try to rearrange the circuit so into parallel parts and series parts, then compute the resistance of each piece individually using those rules, until you're left with just one number, and you're done.  Maybe I explained that poorly, so consider the following schematic:

simulate this circuit – Schematic created using CircuitLab

Sorry it's so large, that seems to be the default.

Anyway, it's easy to compute the resistance from A to D (regardless of the values of the all the resistors)- A-B-D, A-D, and A-C-D are all series connections (easy to compute) then you combine them with the parallel formula and you're set.

But!

How do you compute the resistance from B to C?  There seem like lots of possible ways to think about it, and they all generate different answers.  I've left the specific numbers off the diagram because this isn't homework and I don't care about the answer specifically, I just want to understand the principles involved and how to solve the problem.

Any help, or links to especially readable guides, would be very much appreciated.


texts: Op-amps, their impedance and current flow

texts:
I'm an undergratuate student and I have a question about op-amps.

As I understand it you need infinite input impedance so there is voltage drop across the op-amp and not the signal device. However, doesn't infinite resistance means that no current will flow through the op-amp? Do you get any form of current at the output?

Thank you for taking your time to read this.


texts: Interfacing to metal dome keyboard matrix PCB

texts:
I have a project where I need to physically interface with a remote control keyboard matrix PCB to simulate key presses. Actually, this could be several different remote control PCBs we need to interface with, so we're just looking at this as a generic 8x8 matrix interface, and we'll customize configuration for each. As far as I can tell, all of these use metal domes for the buttons/keys. We've worked out the details of the electronics to connect rows to columns, but we're not exactly sure of the best way to actually interface to the PCB.
Options are:

Solder (or pogo pin?) to test points. However, not all of these will have test points for all of the keyboard matrix rows/columns
Solder (or pogo pin?) to vias. One board's test points are adequate, another has vias for both sides of each of the button switches, but still we're not sure if we'll find these on all boards.
Connect somehow to the conductive part on the PCBs under the metal domes. See picture below (found on Google). This isn't exactly how things look, but basically there's an inside and outside part of the switch, and pressing the dome connects it... Note, per comment below. I think this is conductive ink; it doesn't look like something I could solder to.

We're looking at doing only a few of these initially, but this could scale up a bit and be across multiple different remote controls, and we'd rather not have to hand solder wires for all of these.
How would you recommend making a permanent fixture for something like this? I'm wondering if it's possible to design and order a flex-type PCB that is adhesive that can just be stuck to the matrix in place of the metal dome array? Or anything like this at all? The boards have mounting holes, so we can use that for compression, if necessary.


texts: backup capacitive touch button with momentary switch

texts:
I would like to plug a capacitive touch button on an arduino input and a momentary push button on the same input.
Any suggestion ?
The touch button spec : https://www.electroschematics.com/wp-content/uploads/2015/04/ttp223-datasheet.pdf
thanks


texts: Are Digital Signature Analyzers still used?

texts:
Are digital signature analyzers (such as the HP 5004A) still used?  These seemed to be very useful in troubleshooting digital circuits.

Could anyone expand on what has replaced them?


texts: Propagation Constant Expression in a Transmission Line

texts:
let's consider a generic transmission line:

Its wave vector Kz is equal to:

where

Then, I read also that it is true that:

where does this relation come from?


texts:
I am having some issues with my up and downconverter. What I'm trying to do is to receive a 125 kHz signal, upconvert it to 433.125 MHz, transmit it, receive that signal, and downconvert it back to 125 kHz. I have 2 circuits which are shown in the attached images.

I have verified that the mixers are working properly but there's something wrong going on and I can't seem to know what it is. Somewhere along the way the signal either isn't being transmitted or received properly. I would like to get some pointers and also to see if there is something wrong with the design of the circuit that I have missed.

Upconverter Schematic

Downconverter (U2 is an LT6202)


texts: Crowbar circuit causes unexpected behavior for op amp circuit

texts:
I am using an op amp to amplify an input signal from a microcontroller, which in general is working fine.

For over voltage protection, I added the crowbar circuit taken directly from figure 32, page 27 of the TL431 data sheet and that added some undesirable behavior to the circuit I don't quite understand.

With the TL431 triggering at a voltage of 2.5 V and the voltage divider \$R_3\$/\$R_4\$ the crowbar should trigger at an op amp output voltage of 4.8 V and blow the fuse.
But what I see is, that as soon as the output voltage reaches 3 V, the output drops to 0.75 V and stays at that level until the input voltage drops far enough, that the output should be below 0.75 V in normal operation. After that, it works as expected again, until 3 V or more output is reached.

I found in this discussion of this crowbar circuit, that the placement and size of the capacitor as depicted in the data sheet might not be ideal. Could that somehow cause my problem? If not, what else might be responsible for this behavior?

EDIT:
For proper context for the added crowbar, I regulate the power of a laser with the op amp output. I have to make sure that the laser is not permanently turned on by a short circuit of the output to the 5V that is used as +Vcc for the op amp and for other parts on the pcb. Since I don't need more than 4.2V output and shouldn't get more that that during regular operation, blowing a fuse with the crowbar was the best I could come up with to protect against this case.

Datasheets:

Fuse: https://www.mouser.de/datasheet/2/358/typ_MGA-A-1388649.pdf

Op amp: https://www.mouser.de/datasheet/2/609/AD8605_8606_8608-877839.pdf

Triac: http://www.ween-semi.com/sites/default/files/2018-11/BT137S-600D.pdf

simulate this circuit – Schematic created using CircuitLab

Update: Removing C1 completely does not eliminate the described behavior, but increases the voltage at which it occurs to 3.3V


texts:
I need to build a passive high-pass filter that has a cutoff frequency of 2-3 kHz.  Sounds simple?  It needs to pass between 10 and 20 W rms power at 20 kHz without overheating and going "bang".

The purpose of this circuit is to supply AC power to a nichrome wire heating element avoiding n*50 Hz amplifier noise due to mains electricity frequency.  The rms voltage is below 20 V and the current is below 1 A.

In a previous attempt, I tried to build the circuit below, where R1 is the nichrome wire heater and C1 is two opposite 100 uF electrolytic capacitors in series (cathodes joined together):

This worked for about 10 seconds, then one of the capacitors exploded:

My questions are:

What do you think went wrong with my attempt?  e.g. Was a 35 V capacitor rating not high enough, or was cooling needed?
What would you suggest will give the circuit the best chance of working as intended.


texts: 2 x 90 Ah 12v deep cycle batteries in series runs 77-90w for under 20 minutes. Why?

texts:
I am trying to understand the maths here. I have 2x90Ah 12v batteries in series (24v) and they are powering my computer. The peak power is 120w while the computer is shutting down during a power loss. I get less than 20 minutes run time.
As far as I can tell, when I do the calculation of how many amps it draws I get somewhere around 1A at idle and up to 5A when it is in full draw.
Am I correct to assume that if I am right, at full draw at 5A I should be getting many hours of power out of it? Or at least an hour+? Are my calulations wrong or is there something else going on here?
Thanks!


texts: Very low power voltage regulator - diode?

texts:
I'm developing a very very low power system, and it has some components that need 3.3V. These components are actually spec'd to operate anywhere between ~1.8V and 3.7V, so theres some wiggle room there. Most of the time, these components will be taking in the range of uA's, maybe even under 1uA. The catch is, sometimes they will need up to 30mA. The power supply will be a 7.2V lithium something battery, which obviously needs to be regulated down. I imagine the voltage of this will swing between about 7.9V to say 6.9V (obviously will check).

Since its difficult/expensive to find a buck converter that a) has a low part count, b)has a quiescent current low enough to make it worthwhile, and c) can work down at the uA level but still supply those 30mA bursts, I'm thinking about just using diodes.

If I just chain a load of diodes (say 6 or 7) in series, that will bring the voltage down to what I need. Obviously the actual voltage will vary somewhat with current, although I imagine not that much when the max current is only 30mA. However, I am a bit nervous because I've never seen this being an accepted design. Can anyone see any issues with this? The main benefit is that there is no extra quiescent current draw, and its super simple and cheap. Obviously half the power is being wasted, but that's only the same as adding like another 2 or 3uA on average, which is great.


texts: Help understanding circuit with diodes in it

texts:
I'm having trouble figuring out how this circuit works in the real world. I know theoretically the diodes should have a resistance of 0, 0 and infinite respectively, which makes the question quite easy to solve.

However I'm more confused when you factor in a voltage drop of say 0.6V across the first two diodes. How does that change the voltage drop across the resistors and how do I factor it into ohm's law?


texts: How can I use all of AA battery's energy in an instant?

texts:
It would be fun to know how to pull the whole energy supply of a single AA battery for a one time operation, like making a huge spark, firing a photo flash or a very bright light.

What kind of electronics would be needed?

upd: discharging the battery should power some useful device (or be useful without a device), not just discharging for the sake of it.


texts: Backlight dimming Innolux at065tn14 with vs-ty2662-v1 (PCB800099) LCD driver board

texts:
I would like to dim an Innolux at065tn14 LCD backlight via an PWM signal generated by an arduino pro mini. The driver board has an pt4103 Step-Up Converter to drive the backlight of the LCD display. I'm having trouble dimming the display via the enable pin of the pt4103 with any frequency < 1 Khz.

I've cut the original trace to the enable pin of the PT4103 and connected the enable pin to one of the PWM pins of the arduino.  Dimming the backlight works, but it causes severe distortion of the image with lines and stripes rolling over the screen.

How can i prevent the distortion which is caused by the PWM?

This is the board (vs-ty2662-v1 als known as PCB800099):


texts:
I am interested in designing with cartridge heaters to implement a temperature control system, with a microcontroller sampling temperature sensors and controlling heating elements. I will probably aim for a cartridge heater since they are cheap.

I was wondering if there are any novel circuits or parts for controlling the temperature of a cartridge heater from a microcontroller. The microcontroller is capable of generating a DAC output, if that helps.

My plan was to have the uC control the temperature by providing a PWM square wave into a solid state relay, controlling the duty ratio of the power. I am unsure if cartridge heaters will naturally average the power into an average temperature, or if they get upset from transients.

Also, I'd like to put in as much safety checking as possible. I'd like an open-loop device that can remove power (and keep the power off until a system reset) if something catastrophic happens causing the temperature to run away.


texts: Phototransistor OpAmp - compensating for ambient light

texts: How to automatically compensate (LDR?) for ambient light so as to eliminate the need for adjusting manually with potentiometer.


texts: Looking for help wiring Peltier hear/cool in vehicle w/o the hvac console using dpdt relay

texts:
I am trying to wire seats from a '12 Lincoln MKS into a '02 4runner.
Peltier & blower/fan were controlled via CAN Bus & HVAC module in Lincoln.
Not having that I am needing to devise a relay setup to power/control it.
Found a partial solution (youtube did not show full wiring) utilizing a 4 or 5 pin relay with a DPDT relay.
I have wiring diagram for oem heat/cool setup. (Not seeing an upload/attach option on phone)
Would anyone:
A) be able to assist with how I would need to wire spdt to dpdt to activate heat/cool with a pair of switches
B) be able to verify if above setup would allow for only on/off for both heat/cool
C) if answer to b is on/off only - how much harder would variable hot/cold be (say low/high for both)
D) verify if on/off switches could be replaced with potentiometers (but would want the variable current only to peltier, not fan/blower im guessing so not picturing wiring)
I can provide the stock (thru CAN) wiring diagram - also the utube link for the vid that shows 75% of the dpdt wiring what worked.
Was able to bypass the memory "box" for the power motors/switch but the Peltier wiring is past my Neophyte wiring abilities.
Thanks in advance.
Scott


texts: Issue converting halogen desk lamp to LED

texts:
I have a halogen desk lamp with a three position rocker switch with a central off position and either side representing a different dimming setting. It has a transformer with two coils  connected to each side of the rocker.
The transformer started buzzing which I believe was due to the separating of the plates. I can't get a replacement so I rather than through it in the bin I wanted convert the lamp to LED.
I'm not great with electrics but got most of the way there I just can't explain one issue.
I removed the transformer and replaced it with a 20W LED driver. I snipped and heatshrunk one side of the rocker switch and connected the other to the LED driver. I replaced the halogen bulb with an 11W LED bulb. It works as expected in that the light does not turn on when in the off or heatshrunk positions, it turns on when the switch is in the correct position. The issue is when I return the switch to off, the lightbulb stays on.
Can anyone explain what's going on?
See more information below, the switch is shrouded so I can't see what type or positions.
Wiring

LED DRIVER

Shrouded rocker switch

LED Bulb

I believe the fuse is a simple 1A.
Let me know if any other information would help.


texts: Essential or recommended Digital ICs for a software

texts:
I am creating a program in which circuits using (only) Digital ICs can be made. I have shortlisted around 25 ICs from the 74xx family. Some of them are

7400 (Quad 2 input NAND)
7402
7404
7408
74161 etc.

I have used most of these.

Now my queries are:

How many ICs do you want to see supported in such a program?
Name some specific, essential/recommended ICs to be included.
Are digital ICs alone able to model a large number of circuits, or are analog elements also required?
Is it correct to name an IC with the same function (like XOR) but a different packages (like W, N, D etc.), different types (like LS, S), or different manufacturers as a single name, such as 7486?
IC 7400 & IC 7401 do the same job, so is it ok if I skip 7401?

Suggestions & criticism welcome. This will greatly influence my software design, like extensibility.

By the way, the project is free and open source, hosted here on Sourceforge if you're interested.


texts: I have been trying to record audio using the circuit below. It is different from the normal microphone circuit in that the MIC_IN and MICBIAS are separate paths. I tried to connect an electret microphone to the audio jack and short the MIC_RAW and MICBIAS2_RAW path but no sound was recorded. I used ALSA arecord to record. Does anyone know if I am connecting it correctly?


texts: Boosting Peak Draw spec on LiFePO4 using Capacitors

texts:
Attempt to replace a 4.5Ah 12V Pb battery with LiFePO4 for a Profoto Acute B flash generator I have a detailed writeup here...

Previously I had used a Tenergy drop in Li replacement which worked for a few years but is reaching EOL as well as my Pb versions. It is no longer available.

I am looking to avoid building a Li pack from components and modify an existing pack to do the job by adding capacitor(s) parallel to the battery in order to reduce the peak current by at least 10A to prevent the PCB on the LiFePO4 from cutting out.

Some facts:

-Acute B 600 generator (load) outputs 600 joules
-load is primarily large capacitor bank
-load in turn discharges to circuit powering Xenon tube
-Recycle time is under 2 sec
-Pb Battery is rated 4.5Ah 12V
-Approx Peak Draw is 30A
-battery is fused at 40A (slow blow)
-Attempt with [CTC LiFePO4][3]
   -failed: PCB cuts out at 22A and it did
-Battery Box is 89mm x 69m x 106mm

Options:

-[Bienno stock cell:][2] 4.5AH LiFePO4 rated 4C peak (18A)
-Bienno opt 2 6Ah LiFePO4 rated 4C peak (24A)

I don't have a true measurement of the peak draw, a figure of 30A was given to me by a repair tech.

Looking at a goal of reducing the 30A draw down below the trigger point for either Bienno LiFePO4 pack above noted, I calculated using C=Q/V respectively for the packs noted above.

-  Q=12A/S V=15 C=0.8F
-  Q=8A/S V=15 C=0.5

In either case, I should be able to get the Pack and a pair of caps in Series or parallel depending on available values and build to fit existing  battery box spec.

If someone would chime in on my calculations, it would be nice to know. I don't see where any additional circuitry is necessary on this, the generator only sees a source of V & A beyond it's input terminals.


texts: Why would a three phase motor suddenly change it's rotating direction?

texts: A pump is run by a three phase motor, after a voltage fluctuation suddenly the motor starts moving in the reverse direction. However, the motor is connected with a single magnetic conductor for rotation in one direction. How could the motor rotate in the opposite direction? How do I prevent this from happening?


texts: Measuring current from solar panel using an arduino?

texts: I am designing a MPPT buck converter and bought ACS712 30A arduino current sensor and it is awful. Not accurate at all. so I find two configurations circuits that might help find an alternative to this. However, I really can't find a link or reference that explain the theory behind that and how to design them.


texts: How should I search up parts for basic hard-wired computer? (really basic, no, more basic than that)

texts:
I'm looking to build a computer the size that I can use small jumper cables for the programming, no soldering. Of course it won't be able to do much more than binary counting, etc.

What kind of parts would I use? I would like to assemble inverters and diodes to build the AND gates, XOR gates, etc. on my own. I would however need a way to ensure consistent timing, so I would need a CPU clock, and it would need to be slow enough for debugging purposes.

For those of you who have built computers inside the Minecraft game, that is what I have in mind, except I want it in the real world.

Can you point me to the right class of parts that I should be using? I would like to keep everything on the surface, so I don't want to buy pre-built XOR gates, for example, I would like to keep it to diodes and inverters and then whatever timing mechanism I would be needing.

Actually I was tempted to use magnetic relay switches for the AND gates, cause it makes that cool clicking sound and has an inherent delay.

Can you outline what I need to build such a computer?


texts: Switch power ratings to control multiple RGB diodes

texts:
I will be using 6 RGB common anodes in parallel setting.
I will be connecting the diodes on a car speaker and will need a switch to toggle between colors.

Voltage supply is 12V(or 13,5V), with a FW current of 20mA and FW supply of 2V,3V,3V (red,green,blue respectevly) for each diode

I need help choosing the right switch that can handle the voltage and Ampers.

i found this

The switch can handle 0.05A/50mA, Will it be sufficient for my project?
If not, What power/ampere rating switch shauld i look for for my application.

Edit:

This is how i will wire them(+ resistors) Sorry for bad representation.


texts: Possibility to change IC HCF4060BE to IC 74HC4060

texts:
I recently purchased a very old synthesizer that uses CI HCF4060BE and I want to know if it is the memso that CI 74HC4060.

To help here is the CI datasheet HCF4060BE: LINK

Here the dataset of the CI 74HC4060: LINK

Here the base circuit of the synthesizer IC HCF4060BE:

One of the IC's burned out (it was a problem in the voltage regulator and one track that feeds the other CIs was broken saving the other ICs HCF4060BE).
I am very doubtful because this 74 ... works with 5 or 6v at the most, would that be a problem? why the filter circuit also works with 15v

Thank you all for helping me. I am a hobbyist and I understand the basics of circuits like this so I sent this question.


texts: What's the accuracy of the data sampling clock of LSM303D?

texts:
I have a bad case of "please, read the datasheet for me".

There is a way to auto trigger the sampling in the LSM303D accelerometer, with a fifo to collect the samples afterwards, and a choice of sampling frequency ("ODR" in the datasheet), but I can't find the details of the clock used to sync the sampling. I'd like to have a feel for its absolute accuracy and jitter.

Here is the datasheet: https://www.pololu.com/file/0J703/LSM303D.pdf


texts: Physical principle of the torque of DC and BLDC motors

texts:
I have watched several videos about this topic. According to these videos, the torque of DC motors relies on the Lorentz force (a force that acts on moving charged particles in a magnetic field). However, the working principle of BLDC (or stepper) motors is based on the force between magnetic poles.

My question is: are these two type of forces different, or is it the same force which can be calculated with two methods? I guess, there are magnetic-electric and magnetic-magnetic forces in each motor, but why do they mention only one force per motor? Maybe they mention the dominant force?


texts: Simplest touch sensor for a copper surface

texts:
I'm looking for the simplest way to implement a binary on|off touch switch using a single pole.  The touch surface is copper. The position or pressure of the touch is not needed, just simply:
On = finger touching the copper
Off = finger not touching the copper

The goal is to light up an LED while the copper is being touched. Also, bonus points for small, low-cost, and low-power components.

I found this video which appears to use only a transistor and a resistor, but it's hard to tell what's going on. Is his other hand touching another wire?
http://www.youtube.com/watch?v=StshNHY_3E8


texts: Circuit that retains a state even after power loss

texts:
I was wondering if it's possible to build a digital circuit without using mechanical relays or micro controllers to retain a state even after a power loss?
So a circuit would have a input and an output. The input could be, let's say, a rising edge detecting to toggle the output pin to high/low. When a power loss happens it would retain the last state.
If there are already prebuilt ICs for this, great! If not, is it even possible to build one?


texts: Detecting if specific signal is applied to circuit

texts:
I am doing a project and need to detect if a specific signal in the form of 2 + Asin(2πft) where A is between 1 and 4 and f is 20Hz - 20kHz. Once this id detected I will light an LED.

I was thinking of using op-amp comparators but they can only detect a range of voltages right?


texts: op amp (348) dual supply voltage and feedback capacitor problem

texts:
I have to make a transfer function via op amps  G(s)= 100*20*100/((s+10)(s+20)(s+100)).I have figured that i need 3 stages of that circuit(obviously the circuit below is only for the first  pole  100/(s+10))

simulate this circuit – Schematic created using CircuitLab

so i used a LM348 and used the 3 741 it contains  .When i omit the capacitor i get correctly for square input of 2 V peak-peak at the output the same square but max value is 10 V because ofcourse my transfer function has 10 V/V voltage gain. However when i connect the capacitors my output is no longer square its sth like sin or triangle and very low voltage , about 300 mV , i believe its something like noise .So the question is this , why capacitor mess up so much my output?


texts: How does one determine Lead-Acid battery end-of-life?

texts:
I  have a deep discharge  small       lead-acid  battery bank comprising        only 2 batteries in series, whose terminal voltage reads 26.5V. My past method of determining the need to change batteries is based on it's terminal voltage and overall installation age. This particular bank is about 2yr 10months old (so still should have a 1.5-2yrs of service life, from past experience), and terminal voltage seems in healthy range too. This is not a SMF type, but has had been regularly been topped-up with distilled water.I know that terminal voltage is easy to test but not the best.Do I need to look at things like source impedence or load capacity?

The suspicion on battery is being raised by the UPS service technician. The UPS (APC make), had the fault indication when I called him. He checked UPS, and is asking me to change batteries. I'd prefer to be sure that it is indeed the batteries, since he's done couple of flip-flops with his diagnosis.

Edit (Feb 11, 2013)
Found some excellent reading material here, although it is clear that understanding the health of lead-acid battery is not a simple matter of testing only terminal voltage. Low terminal voltage, after what might be a long duration charge, can indicate a poor health of battery, but not much more.

Battery university
Someone's thesis


texts: What are these LED power supply plugs called?

texts:
New LED lamps made in China have fancy new connectors and I'm searching for the IEEE official name (or whichever authority names them). I need to order male and female ends that can be opened to expose wiring screws inside or soldering posts.

According to Power Brick it's probably 20V DC. The wire looks like 24 gauge? Let's call them think speaker wires. I think the lamp is about 7 watts?

Here's what the male plug looks like next to a dime:

Here's what the female receiver looks like next to a standard USB plug:

My goal is to buy 100 feet of speaker wire and make a 35 foot extension cable and a 25 foot extension.

A nice thin wire pair will run across the living room baseboards nicer than 14 gauge 120VAC cable.


texts: Designed a Buck converter, Need to add galvanic isolation

texts:
I have made calculations for a 22-12V 10W buck converter, which runs at 15 KHz, and uses a half-bridge configuration to deliver power through a 1.34mH inductor.

after simulation in PSIM the interleaved converter seem to function properly looking at the different curves, this was at a fixed duty cycle without feedback control.
I choose a MOSFET driver to be driven by a micro-controller, and got 2 MOSFETS with the proper ratings. However, I ordered the wrong inductor. This inductor has galvanic isolation, and has 2 inputs and 2 outputs. Is there any way I can salvage the inductor? I looked online but failed to see buck converters that have galvanic isolation. I understand the inductor in the link has actually 2 inductors. If I need a 1.34 mH inductor can I just use the first (primary) side as the inductor for this application and neglect the secondary?


texts: Please assume a semiconductor chip like IGBT or MOSFET heated by a specific power loss. It is found that the more the power loss is, the more severe the chip's temperature distribution non-uniformity is. Could you please explain why?


texts: Bridge rectifier with no load draws too much current

texts:
I have a circuit that includes a bridge rectifier and a transformer.

Values are,

Transformer secondary 4.7v x 2  9.4v AC

Diodes 1n5408 (3A Rectified Output Current)

Rectifier connections are right and i measure from anode anode junction to cathode cathode junction. Multimeter reads around 15V DC

When i put an amp meter between one of the outputs of the transformer and bridge rectifier input it reads 1.7 Amps.

In the continuity test there are no short circuits.

Can you think of a reason why is this happening?
I would expect around 6.5 or 7 volts DC at the rectifier out and next to none amps in the amp meter.

Thank you very much.
(By the way this case happens when a reservoir capacitor connected or a load connected also. Transformer itself without the rectifier works as expected.)


texts: With which capacitor and resistance values can I get a 2.1Mhz signal from the tlc555 timer IC? I tried the astable circuit diagram, but I got an error. Which capacitor and resistance values should I use? Or is there a special circuit diagram for this?


texts: RF Transmitter and Receiver circuit controls

texts:
I'm trying to build a Radio controlled TX and RX circuit (using a 2.4 GHz chip and MCUs), to control a robot with four DC geared motors.

I plan to use four momentary on-off-on switches on the TX side to control each corresponding motor on the RX side, but I'm not sure how to accomplish this. From what I understand each momentary on-off-on switch is a "DPDT switch" made from two SPDT switches, so it can control four different circuits. I'm not sure how I should connect them or how this will translate to each channel on the RX end.

What I'm looking to do in simple terms is, when I push a switch up, the corresponding motor will go forward.  When I release the switch and it's in its centre open position, the motor will stop.  When I push the switch down, the motor go in reverse.

Can you explain to me how I can achieve this?


texts: When is it an instrumentation amplifier (In-Amp) and not an operational amplifier (Op-Amp)?

texts:
I've seen a number of different configurations for instrumentation amplifiers, including 2 opamp versions. This

is also one. But it's just a differential amplifier preceded by input buffers. When do you call it an instrumentation amplifier, in other words, what's so special about it that it deserves a separate name?


texts: Does the Machinery Directive (EN60204) require separate mechanical Start and Stop switches?

texts:
I have a prototype machine with mechanical moving parts (all contained inside a transparent interlocked enclosure) to review. Single-phase AC power enters at the rear via a fused IEC 60320 C14 inlet, through a rotary isolator switch (adjacent to the inlet at the rear) to a front-mounted emergency stop switch and then on to the rest of the unit.

The main unit is controlled via an LCD display with a rotary turn and click encoder for navigating menus. Selecting a task and starting / stopping it is achieved via this interface - effectively implementing a software Start / Stop switch. All stops are uncontrolled - i.e. a shutdown signal is sent to the motor drivers causing an immediate loss of power to all moving parts (they have minimal inertia).

In many machines with simpler functionality (pillar drill, band saw) I see this same topology but with the addition of a series contactor controlled by a pair of mechanical Start and Stop switches. Obviously, in this case there is no need for a complex LCD + encoder control system, so the start and stop switches are both necessary and sufficient. But in the case of the system I have described
, does the LCD control described provide compliant control of the system, or is an additional pair of mechanical Start / Stop switches required for compliance with EN60204?


texts: Optimizing a boolean expression to (NAND,AND,NOT) system

texts:
I'm trying to simplify the expression given by the following Karnaugh map to an expression that is using only NANDs, NOTs and ANDs- the less gates (of any kind), the better.

I know how to optimize it to an (OR,AND,NOT) system, but that doesn't seem to help.

I also know how to create an OR gate using only NANDs and NOTs, but that creates a really complicated expression and I've been hinted there's a simple one.

I tried using Wolfram Alpha, but no (AND,NAND,NOT) system exist. The closest one is a (NAND, NOT) system and that expression still looks complicated.

I'm allowed 4 inputs per NAND and 2 inputs per AND.

Thanks in advance!


texts: How may I select a smoothing capacitor to mitigate LED flicker without the use of a scope?

texts:
I recently replaced a set of incandescent bulbs from the interior of my old car with some very inexpensive festoon LEDs.  Unfortunately the LEDs are not 100% compatible with the lighting system as dimming is accomplished via pulsing the voltage signal.  The pulsing effectively dims the incandescent bulb, but causes the LEDs to flicker/blink.

I think a quick solution to mitigate or eliminate the flicker is to solder a ceramic or film capacitor in parallel with the LED power supply terminals.  However, I don't have access to a scope to measure the pulse frequency so I can't calculate an ideal capacitor value to use.

The bulbs run at 12V, draw ~250mA of current -- can someone suggest a safe range of capacitor values I can experiment with?  Perhaps the frequency needs to be estimated for this question to make any sense.

I may also be able to emulate the resistance of the incandescent bulb with a resistor in series, but I don't want to lose the intensity that the LEDs are currently providing.


texts: Why don't we use neutral wire for to ground devices and earth wire for closing the circuit?

texts:
I know that the neutral point of a distribution transformer is connected to the grounding (earthing) wire, so I think they are the same.

Can I use the neutral wire for protecting metal-cased electric devices by connecting it to the case (cover)?

Can I use the grounding wire to close the circuit? For example, can I connect a light bulb between the live wire and the ground wire?

I think the answer would be, "Yes, but It is bad to do this," but I don't know why it is bad.

Edit:

transistor, Thank you very much for your great answer and your time. I appreciate that. I have one more thing that I still don't understand. I wonder if you would mind answering me and I hope I'm not bothering you by my questions.

If the bulb is connected this way:

simulate this circuit – Schematic created using CircuitLab

If the customer touches the lamp when it is switched on, I do not think she will notice a slight tingle because the return path is the ground.

If the neutral wire fell off, the metal case is not live. If the ground wire fell off, the bulb will just turn off but there is no danger. Is it correct to wire devices this way?


texts:
I have an ATMega88PB on a PCB which won't enter programming mode after changing the fuse settings to EXTFSXTAL_16KCK_14CK_0MS. Prior to this, the AVRISP MkII was able to communicate with the microcontroller (I've since switched to an Atmel ICE which still isn't able to communicate).

In case there are any doubts that I have changed other fuse settings incorrectly, here is a screenshot of the fuses prior to programming.

I find this confusing because the oscillator appears to be running fine - if I had programmed the incorrect fuse setting (e.g. ext clk) then I would expect the oscillator to be disabled to save power. As you can see this isn't the case, with the oscillator running just slightly under 20MHz.

XTAL2 waveform:

XTAL1 waveform:

Here is the schematic for the oscillator circuit:

I've tried programming the device at every available speed and still haven't had any luck. I also tried feeding in a clock signal from a working AVR's CLK0 pin unsuccessfully, and have tried 18pF load capacitors in place of the 33pF indicated in the schematic.

What else can I try to get this microcontroller running again?


texts: Why do farads multiplied by ohms produce a result that has a unit of seconds?

texts:
Why is the time constant (RC) measured in seconds even though the units are farads x ohms?

This is to fulfill my own curiosity as I haven't had much luck at finding the answer. I would be most grateful if someone could give me a solid answer or send me in the right direction.


texts: How safe are pre-charged supercaps compared to pre-charged batteries?

texts:
How safe is it to transport and sell pre-charged supercaps with a system?

I'm designing a solar-powered system and I'd like to use something like a
 Maxwell's BCAP0005 supercap (2.7V, 5F) to store the energy.

Even with a supercap charger circuit, it could take 80 secs to charge up. It's been suggested that I could package the system with the supercap pre-charged to save time on the first use. This sounds reasonable because there are systems that come with pre-charged LiPo's; but I've heard anecdotally about safety concerns with large capacitors.

Added:

Thanks to people who pointed out that a supercap may self discharge in a period of under a day, making the question about shipping charged caps somewhat moot.

Please address matters relating to self discharge in my new follow up question
 How to calculate self-discharge time of capacitors given the leakage current?


texts: What's the cheapest type of package to assemble?

texts:
Say you have a microcontroller that you want to use on a production board. Most microcontrollers come in several different packages. Assuming all the packages cost the same, what typically would be the cheapest one to use in terms of board assembly? Also, assuming that space wasnt a problem?

For example, the atmega88p comes in PDIP, TQFP, and MLF. Is one more/less expensive to assemble than the other? I'm talking about from the whole process, from board production to assembly.


texts: Low-power Linux-based ARM system on module for data logger?

texts:
I want to develop a data logger with several hardware characteristics (low-power consumption, SDI-12, I2C, SPI, UART, USB, Ethernet, touchscreen display, SD card, RTC, internal memory at least 128MB...) and multiple high-level capabilities (FPT, HTTP/-S, SMTP, encryption, NTP...).

The problem is that if I use a microcontroller it will be hard to implement in software the high-level capabilities (even drivers). Another solution is to use a System-on-module and implement the software part in a high-level programming language (e.g., Python) in Linux, which will make it easier.

The second option seems better, but is there a (ultra-)low-power ARM-based SoM that allows accessing low-level components (interfaces, incl. interrupts) via a high-level programming language in Linux and, most importantly, enables the user to control the sleep modes from the Linux application? Regarding the latter, how can the CPU enter sleep mode and keep the OS running? I am open to any suggestions.


texts: Can we present the current-driven BJT as two cascaded non-linear converters?

texts:
In the simple BJT current mirror, two non-linear converters - inverse (log) and direct (antilog), are cascaded. As a result, a linear relationship between the output and input current is obtained.

If we can see the same configuration in the single transistor,  we will be able to explain in an intuitive way the linear relationship (Ic = beta x Ib) between the collector and base current.

In the BJT, the base-emitter voltage controls the collector current in an exponential manner. So if we directly drive the base-emitter junction by a perfect voltage source, the bare transistor can be thought as an "antilog voltage-to-current converter".

If we drive the base-emitter junction through a resistor or by a perfect current source, we will control indirectly the base-emitter voltage... and it will control the collector current as usual. So the base-emitter junction serves here as a "log current-to-voltage converter".

The conclusion is that, in this arrangement, there are two cascaded (reverse and direct) non-linear convertors. .. and the overall relation between the output quantity (collector current) and input quantity (base current) of this "aggregate" is linear - Ic = beta x Ib.

Is this a reliable viewpoint at the bipolar transistor and its current transfer characteristic... or I have fallen into some kind of a logical trap?


texts: opamp input bias voltage vs. common mode rejection ratio

texts:
Common Mode Rejection Ratio (CMRR) is often explained as the ratio of out and V1 in a circuit like the one below:

simulate this circuit – Schematic created using CircuitLab

This ignores Input Offset Voltage.

Input Offset Voltage (Vos) is usually explained as the V1 that makes out to be zero in a schema like that:

simulate this circuit

This in turn ignores CMRR.

Usually only upper limits are provided for Vos, but no information on how it depends on common mode voltage or frequency.

Is Vos dependent on common mode voltage?

The point I'm trying to make is that when the Vos may change with common mode voltage, then what's the point of CMRR? Or is Vos considered to be a fixed voltage for each device?

What about input bias current?

I have the same problem with the currents. The datasheet gives me limits, but no indication on how 'stable' they are with frequency or common mode voltage.


texts: Why does DMM show AC and DC current when source is a battery? (How to calculate power in this case?)

texts:
The circuit is an altered Joule Thief of my design that is driven by an AA or AAA battery. I’m observing the current at the battery anode with my DMM in series. (Extech EX330)
This circuit is extremely efficient (In relation to other Joule Thief I've build.) and does some weird stuff - like, it needs a pushbutton sometimes.

Measurements:
It is drawing 9.21 mA DC and 6.48 mA AC in series with the battery.
It shows 1.364 VDC and 0.010 VAC in parallel with the battery.
Output on the LED is 2.572 VDC and 0.011 VAC with no measurable frequency. (with my DMM at least)
All measurements are taken with the same configuration and voltage.

But how is it drawing AC and DC and how do I calculate power consumption?
--> Could it be because the emitter pin of the NPN is directly connected to ground?
--> Or is the circuit just "switching on and off"?

Download schematic: https://drive.google.com/drive/folders/1Vr9mQx449-RmjqclVZdgrnk5SyXjxTlG?usp=sharing
(I tried to simulate the circuit in LTspice. Thanks for making me aware of this amazing program, Sredni Vashtar!)

What the pushbutton is used for:
The pushbutton is used to "kickstart" the oscillation when it wont start by itself.
For example: I have to manually "oscillate" using this button to start the circuit if the capacitor is too big and battery voltage is low.
Pushing the button releases the energy in the transformer into the capacitor. If it reaches LED forward voltage the circuit keeps oscillating on it's own.
It does work without manual intervention when then capacitor in parallel with the LED is not too big, like <5000 µF, and it's a fresh battery.

.
Thank you for your answers! I'm learning so much! :D


texts: Problem with a infrared integrated transistor IS1U621

texts:
Hi I'm working on a project in witch I need to use the IS1U621, the circuit implemented is:

but no matter what I'm always getting voltages over 3v on the output, anyone has a tested circuit that I can use??

PD: The drawing has a mistake in the ground and Vcc pins but I have corrected it on the protoboard implementation. That's not the problem.


texts:
I just started reading about operational amplifier from the book Fundamentals of Microelectronics by Behzad Razavi.
I want a to get a better understanding of precision amplifiers and their design.
The book this diagram as an example of a precision amplifier:

The book says that "when v(input)=0 op amp raises Vy such that it barely turns on the diode."
I don't understand how this is possible because we know an ideal non-inverting amplifier has finite closed loop  gain and if the input is zero then the output should also be zero (0×finite gain.)

How to justify that statement intuitively? (Better would be mathematically.)

If we remove R1 (in the figure) and replace it by a short circuit (figure below) what will be its output?


texts:
Im new to electronics. In fact, I'm a computer scientist looking into embedded systems.
I am going through Vol. 1 of Jonathan Valvano's book on embedded systems and got stuck when i read on Gated D Latches:

What does it mean when an input falls? He says that: "the last D input is remembered or latched when the enable input falls"???

See the truth table where W is the enable input:


texts: In a 74HC14 Schmitt trigger IC, unused inputs/outpus

texts:
I have a 74HC14 Schmitt trigger IC. I only use one of its I/O pairs, and everything else is not used.
I understand that in TTL logic the unused inputs should be set to either high or low to prevent floating pins.
But I wonder, can I set the outputs to high instead? Will the effect be the same, i.e prevent floating pins? Is this a bad idea?


texts: Why is the signal-power-signal-ground 4 layer PCB stack frowned upon?

texts:
Commonly, the best practice 4-layer PCB stack up is (from top to bottom) signal-ground-power-signal. That keeps the signal layers close to a reference plane, and allows signals to be routed directly to the components.

Alternatively, for stringent EMC requirements, power-signal-signal-ground can be used to provide some shielding at the expense of ease of re-work and component-signal routing.

Other more exotic stack-ups can be used with care.

Why then, is signal-power-signal-ground not generally recommended? It maintains the signals-close-to-reference-plane characteristic while adding a shielded signal layer for those signal worth shielding. For slower/less critical signals, the top signal layer provides convenient routing. Additionally the bottom ground layer potentially provides better heatsinking options.

The only concern I've come across is that the asymmetry can lead to warping during manufacture.

Why is this stack-up generally not recommended, and what is the mechanism of the warping issue?


texts: While making colourful LEDs why dont we just coat the LED with a filter to just give out the colour of the light we want , rather than constructing the LED with different combinations of semiconductor which would give out that light?


texts: In what condition power MOSFET gate capacitances Cgs and Cgd can be paralleled?

texts:
I would like to get some understanding about the gate charge of a power MOSFET. I am referred to this MOSFET gate drive circuit application note:
https://toshiba.semicon-storage.com/info/docget.jsp?did=59460
In page 5, subsection 1.2.3. Gate charging mechanism, they assert that Cgs and Cgd capacitances are charged in parallel but I didn't figure out why, normally the MOSFET is in off state and there is no short-circuit across its drain and source. Also, the figure 1.4 and 1.7 state that from time t0 to t2 only Qgs is involved!


texts: Powering of Peltier Elements and power issues!

texts: I want to power up 4-5 peltier elements TEC 12706 which have maximum voltage of 16.4V and max current of 6.4A (at 50 C). Will a power supply of 12V 30A do the job (I'm thinking about connecting them in parallel). Also in which case peltier is going to take it's maximum current? I have done experiments before, peltier does not sink more than 2A of current. Why so?


texts: Reverse blocking IGBTs no longer available, why?

texts: I've been looking at IGBTs for a power project. Primarily since they can handle high voltage and have decent reverse blocking capabilities. Two devices I'm familiar with are Punch Through (PT) and Non-Punch Through (NPT). A third one was offered a few years ago (I can only find one vendor who sells the device) but has since been deemed obsolete. This particular device was called the "reverse blocking IGBT" or RB-IGBT. It had blocking diode that would allow for a more robust reverse Vce breakdown (the semiconductor structure of the RB-IGBT was similar to a NPT, but RB has the p+ layer (connected to the emitter) actually encapsulates the entire device up the oxide as if the p+ layer acted as a bucket). Seemed to me that the RB would be a better device for AC operations than an NPT. So, what happened? Or did they come up with a better, cheaper NPT device? Or did I miss something obvious?


texts:
I was developing a BPSK modulator with an AD9852. Since AD doesn't seem to offer any way to functionally simulate their DDS ICs, suddenly i see myself in the need to change for a FPGA architecture. I haven't work with an FPGA or VHDL yet. After researching a while, i came up with a couple (rather, a lot) of questions regarding FPGA and DDS architectures on it:

1) How fast can the internal reference clock on the FPGA go? can it be divided internally to obtain a higher reference clock?

2) Is it possible to make an internal DAC on the FPGA?

In case it isn't, can the internal reference clock be outputed to an external DAC? how can the pipeline delay in this case be fixed?

In case both are possible, which one would be recommended?

3) In several projects with FPGA, the modulator is simplified by using the DDS to generate the carrier frequency, then multiplex it with it's complement and the binary data input. In traditional schemes, the phase modulation is done to the phase accumulator output, before the LUT. How can this be practically done (for what i can see with the FPGA tools, most of these block are already available).

Also, the LUT can be reduces by exploiting the sine wave symmetry up to one quarter or just simply remove it and applying CORDIC algorithm. How can this phase truncation be done? in the case of CORDIC, is there an implemented CORDIC block for this?

By the way, silly question. Does the LUT values have to be calculated for each frequency tuning word  in the phase accumulator or does it only depends on the reference clock (in which case it would need to be calculated for an specific reference frequency)?

4) Is it possible to make DSP floating point calculations on FPGA? i'm aware there are some embedded boards with ARM cortex.

Finally, what models/boards of FPGA would you recommend for this particular application (also considering that i'm on a budget)?

i'm aware these are a lot of questions, but any help on these issues would be appreciated

Thanks in advance


texts: SDC constraints for source clock and derived clock

texts:
There are two clocks in the system, clk2 is derived from clk1 with a 180-degree phase shift. There is 1-bit data from clk1 to clk2.

I know this is a kind of asynchronous scenario and the traditional method is the use of 2 FFs or an asynchronous FIFO to synchronize the data. However, since these two clocks have a fixed phase difference, so is it possible to synchronize the data JUST with SDC constraints? If it is possible, how to set the SDC?


texts: When to use buffer/ low-pass filter on ADC input?

texts: Sorry if this is a bit of a sophomoric question, but when should you buffer an ADC input, specifically from a potentiometer.  I've seen circuits add a low-pass to the wiper/ ADC input.. is this only necessary if you have switching noise on the reference voltage bus?