texts: How to calculate frequency and channel bandwidth

texts:
I made a regenerative receiver by slightly modifying the design at http://www.ke3ij.com/am-univ.htm to match the design below and with the right part combination I managed to pick up many stations including many FM stations within a 60km radius and even a local TV station (cable channel 12) within approx 10km radius thanks to the invention of a trimmer capacitor that I constantly played with.

I read that resonant frequency is calculated as:

\$f = \frac{1}{2 \pi \sqrt{L C}}\$, but I think with my circuit there is a catch because if I tune my trimmer too far, I start to hear internal oscillation (actual noise). Also, if I set the capacitor connected between emitter and collector of PN3563 incorrectly, then I'll get either no sound or noise.

I feel in my circuit, the inductor and capacitor connected between emitter and ground plays a huge role in determining frequency and capacitor between emitter and collector helps with feedback and capacitor between base and ground has something to do with bandwidth as well as the resistor between base and collector.

I don't know the math to calculate bandwidth, and I think I can use the standard formula I typed above to calculate frequency.

Any ideas?

Also, the part values are not set in stone except for the PN3563 since I am still experimenting.


texts: Why is my Pi Pico resetting from HDMI hotplug (transients question)

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Why exactly is my Raspberry Pi Pico (MCU) resetting during HDMI hotplugs with my simple HDMI signal sniffing circuit? Although the solution to this is obvious, I'm curious as to exactly what's happening and if this is cause for extra considerations for my circuit.
Minimal example to reproduce this (no signal pins connected to HDMI, only ground). Note (1) pico is powered by laptop USB and (2) the “run” pin is meant to reset the device when pulled to ground.

I put a Raspberry Pi Pico in a breadboard. There are only two jumper wires attached to Pico, but neither attached at other end - one on "run" pin, the other on ground. I power on the pico with my laptop USB, running a small C program I wrote. My laptop is not plugged into an outlet.
Pin 30 (Run) has a single short ~4" jumper wire connected via breadboard, but it's not connected to anything at other end (e.g., just left loose in air, or placed in empty row in breadboard).
Pin 3 (Ground) also has a single short jumper wire attached to it, and is left dangling.
I plug one end of an HDMI cable into my TV, which is on, and leave other end disconnected.
I take the ground jumper wire and tap it a couple on the shell (shield/ground) loose end of the HDMI cable connected to my TV.
Pico resets.
The pico only resets when I tap the ground jumper wire to my TV ground shell/shield, not my set-top-box shell/shield.
If I disconnect the jumper cable from pin 30 "Run" (which is not actually connected to anything), and redo this, the pico does not reset.
Note: The "run" pin resets the pico if pulled to ground. According to datasheet, there is a ~50k internal pullup resistor to 3.3v VCC.
I think it's clear that when I leave the jumper wire attached to "run" in breadboard and dangling, somehow the run pin goes low when connecting grounds from Pico to TV HDMI, but why?

Another note... Similar to https://www.tivocommunity.com/community/index.php?threads/hdmi-ports-voltage.482253/ I am seeing about 50V AC (60hz) RMS on my digital voltmeter between Samsung TV hdmi shell and wall ground when TV is not connected to anything except wall power (it has 2-prong plug). So I'm guessing this is what's doing it. Presumably this is very low current, but what can I do to protect against this during hotplug?
To explain why I am doing this, I was interested in using the Pico to sniff DDC (i2c) and CEC traffic (one-wire protocol for control messages) on HDMI. My actual circuit uses a 74LVC245 to level shift the HDMI signals, and I have a separate board to breakout the HDMI pins while passing through from source to sink. Also, it uses DDC ground, not shell (but there’s continuity there on both source and sink side). I want this to work through an HDMI hot-plug. However, doing hot-plugs (regardless of which device is plugged in second) was resulting in these resets. I had the jumper wire connected to "run" to reset the pico to upload code, and only after removing that did the resets stop.
More important than why is this happening, I am wondering if this means I should be adding some sort of protection for voltage transients to this circuit, especially if I were to make this more permanent? What sort of considerations should be made here for hot-plugs? Note: I'm not interested in doing anything with the high-speed differential HDMI signals.


texts:
I don't entirely understand static electricity; particularly how it seems to flow through rubber shoes and paint, but seemingly not rubber tyres or car seats.

I am tired of getting shocks from my van.

I've read that those anti-static strips for vehicles that drag on the ground were banned from being marketed since they don't actually work. I also read that the strips are less effective than the tyres depositing charge as they roll on the road.

I've read that the best methods for avoiding the shocks are to either hold onto the frame of your car as you're getting out, or alternatively, once you're out of your car, before touching the door to close it, hold the metal of your key and tap it with the end. I believe I've had some success with these, but not all the time.

What different ways and where might the static electricity be building up? Why do/don't the above methods work? And what can be done?

Some ideas:

Cover the seat with anti-static [something]
Try an anti-static strip anyway


texts: Were single-in-line packages (SIP) ever popular in the West? Or even used much?

texts:
My impression is (and I could be wrong) that single-in-line packages (SIP) were never popular in the West (relative to DIPs anyway), while they saw more adoption in Japan and in Asia in general. I'm saying this based on how I see the current state of the market, in which one can still find through-hole SIPs from Japanese manufacturers, but they seem to have practically disappeared from the Western manufacturers' portfolios, if they were  even present in those. (Now I know that the through-hole technology in general is on the decline, but let's not get too far afield.)

It seems difficult to find any sort of written history on this matter, i.e. how prevalent SIPs were in various parts of the world over time, so anecdotal evidence based on personal experiences would be appreciated too.


texts: How to simulate ~1ms long power interruption

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I am looking to test an embedded system for its behavior during power interruption soon after power on. The system is supplied with 15V DC power with a steady state draw of <500mA

The power transient is shown below - 1ms on, 1ms off, and then on again for steady state, simulating the action of a specific mechanical interrupter to turn the device on. The turn-off and turn-on time is <10us . When the power is turned off the supply line is left floating

simulate this circuit – Schematic created using CircuitLab

Mechanical relays are not quick enough to do this, I have considered solid state relays but their behavior is load dependent. Programmable Power supplies are usually with a resolution no better than 1ms.

Since the total load is under 1A peak I have considered using a Power MOSFET as the switching device and this is my current approach.

Is there anything else that you can suggest to test these conditions in a controlled, repeatable manner?


texts:
I've been wondering if its common and a good idea to combine a buck converter with a LDO to for example move 5V down to 1V for a microprocessor.

I'm unsure about the stability of the processor doing this, because I have no experience in using buck converters. However as my prototypes are getting smaller and smaller, heat dissipation is becoming a problem and this might be a solution.

Would it be a good idea to use a buck step-down converter to move 5V to something like 1.3V and do the last 300mV with a low noise high quality LDO?

How sensitive are microprocessors to ripple? Is it maybe even possible to only use a buck converter without compromising stability?

The microprocessor is being used as a part of the USB Audio decoding to I2S to the DAC, I know its a bad idea to use any kind of buck converter for analogue circuitry, so won't using a buck converter make ground more noisy and introduce noise to the audio signal?

Sorry for all the questions and thanks for you time!


texts: Where does an op amp's input bias current come from if capacitor is used?

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In the case of a non-inverting amplifier, if I DC couple the input signal with a capacitor only, \$C_1\$ (i.e. no resistor to ground), sources (as well as an experiment in the lab) show me that the op amp input will be saturated as the input bias current deposits charges on the terminal without having a return path to ground. This is solved by using connecting a resistor (\$R_1\$, as shown in the image below) to ground to create the return path. [The image is reproduced from an answer by "Neil_UK" on one of my previous questions, thanks Neil!]

My questions:

1) How is the input bias current able to continuously deposit charges and saturate the input if I don't use the resistor? The resistor should not allow the DC bias current through, so where is this current flowing from/into?

2) Why is this not a problem for the feedback path to the "-" terminal? There is no resistor to ground in that case, and capacitor \$C_2\$ seems to be causing no issues. The PDFs I've been reading suggest that the feedback behaves similar to when I have a resistor to ground by acting as the return path, how is this?


texts:
In my audio project, speakers are connected to voice chipcorder(ISD3800) and the voice chip is connected to micro controller.
Audio functions well with the setup.

My question is, Is there any way to find my speakers are playable before playing any audio?
Ideas to detect speaker failure before playing any audio...

Thanks in Advance


texts:
simulate this circuit – Schematic created using CircuitLab

Please read the LM358 as LM339 as I could not find LM339 in schematic library

I am designing a LC Tank circuit with comparator to be used in an inductance measurement circuit.

Ideally, when the circuit is charged for a couple of seconds and then the switch disconnected, the circuit frequency should be 13.30kHz according to the resonant frequency formula but when I simulated the circuit, the frequency measured is 220Hz.

Can anybody please check if the circuit is correct or not?


texts: AVR - NRF24L01+ : Encrypt Data Transmission

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I have a pair of AVR's that communicate over the 2.4GHz link using NRF24l01+. The payload sent is 5 bytes long.

Right now the payload sent is in clear format so that anyone with enough knowledge and skill could theoretically build a device to intercept the data stream.

Can you please provide me with some recommendations on ways to encrypt this data stream considering it would be implemented on a 8 bit AVR (small code size) and would be done real time (so should be fast).

Thanks!


texts:
This video lecture (start at 32:01), the professor showed a demo about the effects of feedback on noise and non-linearities.

The graph below is a system with input signal which is applied directly to an operational amplifier(the amplifier models the linear portion of the forward path gain), followed by a nonlinear element (has dead zone and two different degrees of compression of linear region). A potentiometer is put between the output and input of nonlinear element to moderate the effects on the non-linearity.

What I am confused is why the feedback path (potentiometer) is connected between the input and output of the non-linearity element as the figure 1 instead of the one as I modified in figure 2.

Can I use the feedback path with the voltage divider as figure 2?

Figure 1: system from the lecture

Figure 2: modified system


texts: after replacing micro usb port, tablet charges only 450mah

texts: I changed micro usb port which was broken (it takes out from motherboard) on tablet. On motherboard are 5 contacts and one is damaged (4. - it is for data transfer, ID). I solder +5 VDC contact and Ground, and left 4,3,2 pins for data transfer (not solder them). Now tablet is charging but "only" with 450mA. Why charging chip doesnt increase charging power more than 450mah. I think that 4,3,2 pins are not needed for charging by charger, only for data transfer and smart recognition. Am I right or wrong?


texts: Combine two signals of different frequencies in a test setup

texts:
I have a device that is powered from a current source. The current source supplies 10A at 60Hz - the magnitude is roughly 5-10VPP.

I would like to inject another signal on top of that to simulate noise or data at a high frequency.

I am powering my device from the power line current through a CT, and I am also measuring the current through another CT.

Ideally I would like to be able to measure the frequency response of my power input circuitry to see what my passbands are at the input to my power supply, and I would also like to see what my passbands are at my ADC input.

So here is my harebrained Idea:

As you can see, the point between the two diodes should be DC Biased to 12V. There should be no DC current though. But because that section is biased up, the diodes should block any of the signal from flowing back into the current source or back into the source on my spectrum analyzer. Then I would strip the DC off using some arbitrary low valued power capacitor. I would effectively be floating my current source to a virtual ground 12V above my system ground. To do this I would need to use a cheater plug. If I tie the negative terminal of the battery to system ground and to the output tab of my UUT and tie the positive tab of the battery to the tab on the cheater plug I think this effectively makes the battery part of my AC current path which may be a problem. Anyone think this will work?

The only other thing I can think of is building some LC PI filters - one a high pass from the analyzer source, and then a low pass from the current source. I need to pass several amps of current though so I would need to keep the impedance down on the low pass. But that could be an option.

EDIT:
Here is the type of current waveform I want to drive into my system. Note that I want to sweep the frequency on the higher frequency component.

As of right now I leaning towards using a high current buffer amp w/ summing amp input to do this and ditching my existing current source. I can't figure out how I would wire up the above circuit to float my current source without burning the building down.


texts: How Do I Calculate The discharge Time of Capacitor with a resistor as a load?

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I  was trying to make an ADC with an RC circuit. I was using an ATMEGA328P to measure the time the capacitor needed to discharge to 0V. I created the circuit with a sample and hold opamp, a precision 1uF Cap, and a 10K precision Resistor.
I was trying to find out the formula to calculate the capacitor original charged voltage with the time constant I get from my microcontroller and my known resistor and capacitor value.
Is there any way/formula to calculate it?

simulate this circuit – Schematic created using CircuitLab


texts: Making Sense of oscilloscope specifications

texts:
When looking for oscilloscopes, you often see the following specs:

bandwidth [in Hz]
sampling rate [in Samples/s]
capture rate [in waveforms/s]
record length [in pts/channel]

My question is: How are these specifications related?

Take for example the following comparison table from the company Siglent:

All these scopes have a sampling rate of 1GSamples/s, meaning they can take 1 billion measurements every second. From the Nyquist-Shannon Theorem these scopes should all be capable of accurately measuring frequencies up to 500MHz. But their bandwidth only allows for at most 200MHz, and only 100MHz for the scope in the centre row. How is this reconcilable?


texts: Filter Design Preparatory Book Recommendation

texts:
It is generally agreed that Zverev's "Handbook of Filter Design" is THE reference work for LC filter design.  However, I crack it open, and the first thing he does is head off into lattice filter theory, and I don't have that background.

I have a rudimentary grasp of elementary RLC circuit analysis (steady-state, not impulse) (first EE circuit analysis class).  Can anyone suggest book(s) suitable for getting me from there to ready to tackle Zverev?

My interest is casual design of HF and VHF receiver preselector filters, and HF and VHF transmitter output harmonic suppression filters, for amateur radio applications.  I am NOT afraid of math; I am NOT afraid of numbercrunching; I am NOT afraid of MATLAB (GNU Octave, usually).

Thanks to everyone!


texts: Vivado : constraints setup for SPI interface with common clock

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I have been using Vivado 2018 for a system level design and am having trouble with a SPI interface programming. A block diagram of my system is shown below.

The Artix-7 FPGA (on the motherboard) sends out a 3-wire SPI interface  to 4 daughterboards. Following are the specifications :

FPGA :

CLK : input clock to the FPGA
SCLK : MMCM generated clock used to generate the SPI clock for the internal modules. These module generate the serial data to program the IC's on the daughterboard.
SPI_SCLK : serial clock for the SPI interface common to all daughter-boards.
SPI_CS : select lines common to all daughter-boards (using the select line from module #1 on the FPGA)
SPI_SDI[1,2,3,4] : serial data specific to each daughter-board generated by the corresponding module on the daughter-board

Daughter-Board(s)

CLK_BUF : a clock buffer for the SPI clock, which introduces a 5ns propagation delay.
IC #1 --> IC #7 daisy chained on the daughterboard
Common select lines to the daughterboards

CONDITIONS

Delay on all SPI lines going from FPGA to daughter-boards are equal.
delay introduced by BUF IC = 5ns
tsetup (IC) = 5ns
thold (IC) = 5ns

I have setup my constraint files as follows:

create_generated_clock -name sclk [get_pins clock_sources/inst/mmcm_adv_inst/CLKOUT2]

set_output_delay -clock sclk -max 5.000 [get_ports {spi_sdi[*]}]
set_output_delay -clock sclk -min -5.000 [get_ports {spi_sdi[*]}]

set_output_delay -clock sclk -max 5.000 [get_ports {spi_cs]
set_output_delay -clock sclk -min -5.000 [get_ports {spi_cs}]

QUESTIONS

Is this the correct approach to setup the constraint file for the SPI interface? Because of the propagation delay introduced by the CLK BUF IC on the daughter-board, I would like to delay the SPI_CS and SPI_SDI[1,2,34] lines by the amount equal to the propagation delay of the CLK BUF IC.
I believe the Modules 1,2,3,4 will have different net delays for the SPI_SDI[*] paths going out of the FPGA board. How should I ensure that these line see the same delay and hence are output synchronous to each other?
Similarly the SCLK going into each of the modules on the FPGA vs the SPI_SCLK going to the daughter-boards see different delay. Will this affect the serial data put on the bus?

I would like to understand how to tackle these issues. Any help is appreciated.

Thanks


texts:
I need to connect 5V laser module looks like this one.

I connected it like an LED and it works. But i am afraid of doing something wrong.

I came across things like "laser diode drivers" such as this one.

Why do we need a driver for laser diode? what is wrong to connect it like an LED since it seems it works.

Is laser diode and laser module different things?


texts:
In schematic below when current exceeds the set point of PR1 it toggles the relay and as soon as current drops the relay goes back to normal state:

How can i keep the relay state as triggered even when the current drops and only switch the relay back to normal state when i pressed a push-button?


texts: Purpose of capacitor in audio amplifier circuit

texts:
The circuit above is from a kit and is described as a Class AB audio amplifier.  This is a screenshot from LTSpice.  The audio input comes in at the center-left.  The battery is 9V.

I am trying to understand the purpose of the 0.001uF capacitor, C46, at the top and just a bit left of center.  I have considered that combined with R46 it might be part of a filter or it may be to short high frequency components from the base of Q11 to the battery rail and thus to AC ground.  I am just not sure.

Thanks.


texts: Need help understanding a parallel circuit and how to make it work right

texts:
I'm building a prop for a game. Its an Arduino Nano that runs some LEDs via a controller board, a small motor, and a mini MP3 board for sound. It's powered by a 9v battery. It runs great. I wanted to add some extra LEDs to it so a small analog meter that's attached to it could be seen at night, and wired some LEDs up to the battery in parallel with the arduino circuit. When it's turned on, the extra LEDs flicker and then die as the Arduino turns on and gets going. I'm obviously not understanding something about how the circuit works, voltage, etc. The Arduino is providing 5v that is enough to power a bunch of LEDs through an adafruit LED matrix board - why are 3 LEDs in parallel with the whole thing not getting enough power when the Arduino turns on? Here's an oversimplified circuit of how it's laid out:

simulate this circuit – Schematic created using CircuitLab

Obviously I left out all the components attached to the Nano itself, but I wanted to show where the battery and power switch was and the 3 LEDs in parallel with the arduino circuit.

The 3 LEDs are white LEDs that are listed to have a voltage drop of 2.8v and pull 20mA. ledcalc.com said it needed a 30ohm resistor. Which works great when NOT also using the arduino.

So I'm not understanding something about how voltage works when powering different devices in parallel. Every search I do on google talks about LEDs in parallel vs series, but not much about parallel circuits. Any guidance here? Thanks.


texts: Advantage of clock enable over clock division

texts:
I have an FPGA design which uses different clocks. There is a 100 MHz reference clock provided by an oscillator. The reference clock is used in a DCM (Xilinx FPGA) to generate 3 related clocks, 100 MHz, 50 MHz and 10 MHz (no phase offset).
In situations like this the advice of tool vendors and collegues is to use only one clock, the 100 MHz one, and instead of the other clocks create clock enables which are only active every 5th / 10th clock cycle.
What's the advantage of doing this? Yes, there will only be one clock and timing analysis will become easier, but that's a tool issue and should not dictate fundamental design decisions.
Especially for a design with a high device utilization I can see advantages for divided clocks, since e.g. the 10 MHz clock domain will have a much easier time to achieve timing closure and will "leave more room" for the placement and routing of the logic in the 100 MHz clock domain. With clock enables I'd carelessly give away this advantage.


texts: How is this CD4013 application supposed to work?

texts:
I'm trying to troubleshoot an issue in a synthesizer I have, an early 80s synthesizer from Roland called RS-09. I'm just starting to study logic and am perplexed by what's going on. In this synthesizer, a 4013 is being used as a frequency divider to divide or not divide a trigger signal from a master oscillator based on whether the user has selected a feature called "Octave down" via a switch. The output Q of the 4013 then passes to a "top octave generator" that uses it to generate the 12 notes of a chromatic scale from which all the other notes are then made. Right now it is only working in "Octave down" mode; without "Octave down" selected, all keys just produce noise. Here's a closeup of this part of the schematic. The vertical line labeled with "10" connects to the switch, and the horizontal line with the indicator that the square wave should be there connects to the octave generator:

The 4013 is set up so that the "high" voltage is 0V and the "low" voltage is -10V (down arrow is -10V supply). When the "Octave down" is selected and the 4013 is supposed to divide, the switch applies -10V which sends a little less than that -10V to SET (pin 8) via the 15kohm resistor; when "Octave down" is not selected, 0V is connected to that path.
In Octave down mode, that -10V is also able to pass through the diode D206 to RESET (pin 10) (less 0.6-0.7V from the diode drop) and with reset and set held in the low state, the flip flop is in clocked mode, responding to the trigger signal from the master oscillator. This seems to be working just fine. With Q/ connected to D as it is, the flip flop also "binary divides" and Q outputs a square wave at 1/2 the frequency of the trigger.

My problem is that I don't understand what's supposed to be happening when "Octave down" is not selected. I don't see how it could possibly work, and it doesn't. This is what my understanding is, but something must be wrong:

The ~0V at SET holds it in the high state but cannot pass through D206 to RESET, leaving the reset open to receiving its "instructions" from the oscillator (direct mode). The trigger oscillator starts out oscillating between +5 and -10V but the diode clamps it at 0V to cut off the positive portion and is then sent to RESET [edit: this is not quite what is actually happening-- see oscilloscope images below]. But with the Set held high, the only possible outcomes for Q are the high state when the oscillator is at its low point sending ~-10V to Reset, when Q is high and Q/ is 0, and the "disallowed state" of both Set and Reset being high, leading to both Q and Q/ being high, when the oscillator is at its high point. Therefore, Q just sends out a constant "high voltage" (0V in this case) with a little bit of noise. That is what I'd expect and what I'm seeing it do. My meter and oscilloscope measurements confirm that this is what is happening.

How is this supposed to work? Something is clearly wrong both in my interpretation of how it should work and in the way the circuit is actually working, but I've looked it over so many times and still can't figure it out.

Your help is very much appreciated!

Edit: I am adding these shots of the oscilloscope showing different inputs and outputs in the setting that is not working (higher octave).  I left the vertical position where center is 0V to show their relative positions. I am on 0.5V/div.  I was surprised to see how far negative the waveform at Reset is and how small the amplitude is.  This is a little different from what I thought I observed before and more apparently "incorrect".

The output of the master oscillator (where it arrives at CLOCK) is not a great-looking trigger waveform either, and my understanding was that 4013 requires a good trigger, but it seems to be working in clocked mode so maybe that's not an issue.


texts: How do I simulate a dc-dc boost converter in LTspice?

texts:
For a electric circuits lab I had to implement a dc-dc boost converter circuit and take certain measurements while I varied the duty cycle of the pulse applied to the MOSFET so that I could observe the relationship between the output voltage and the duty cycle. Unfortunately, I forgot to measure input current \$i_{in}\$ show in the schematic below

where L = 455 uH, C = 18.92 uF, and R_L = 0.98137 kOhms. The voltage source v_in is constant 5V dc while the PWM voltage to the MOSFET is a 5V max, 0V min, 100 kHz, square wave with duty cycles varying between 10-90%.

So now I'm simulating the circuit in LTspice so I can retrieve at least the theoretical current values at different duty cycles.

Here's the reconstruction of the circuit:

This is the voltage I get across the load:

This behavior concerns me because it looks nothing like the signal I saw on the oscilloscope in the lab AND when I vary the duty cycle of the PWM signal, the voltage across the load doesn't change. The experimental behavior, and the behavior I'm trying to re-create with the simulation, is:

Duty  Voltage
(%)   (V)
10    6.273
20    8.2296
30    10.884
40    13.03
50    14.55
60    15.3
70    15.898
80    23
90    37

How can I fix my simulation to mimic the actual behavior I observed?


texts: How to wire RJ12 to db9f modular adaptor?

texts: I have a RJ-12 to DB9f modular adapter. There are 6 wires that come out of the adaptor (White, Black, Red, Green, Yellow Blue) - these, as I gather from pin out diagrams, correspond to the 6 jacks of the RJ12. There's also a female connector - with 9 holes. How do I wire the previous wires into the appropriate holes?


texts: Can You Swap Two Capacitors With Different Ratings?

texts:
I've bought a broken receiver recently and I need to swap out a few of the capacitors.

the original capacitor is rated at 100v and 0.01uf. The local electronic store sells 100v 3.3uf capacitors. Would I be able to swap these two, or would the different in uf make them not work with the rest of the system?


texts:
I am playing with 3,5" (400x240 chinese unknown 8-bit controller driven) TFT display which is placed into Arduino Mega 2560 R3 board.

My final goal is taking .raw data from SD card and drawing it on display.

What I have done so far:

- My drawing method in the sketch:

void LoadImage(File& file)
{
    for (int y = 0; y < SCREEN_HEIGHT && file.available(); y++) {
        uint16_t buf[SCREEN_WIDTH];
        for (int x = SCREEN_WIDTH - 1; x >= 0; x--) {
            byte l = file.read();
            byte h = file.read();
            buf[x] = ((uint16_t)h << 8) | l;
        }
        myGLCD.drawPixelLine(0, y, SCREEN_WIDTH, buf);
    }
}

- For reference drawPixelLine method's implementation from UTFT library:

void UTFT::drawPixelLine(int x, int y, int sx, uint16_t* data)
{
    unsigned int col;
    cbi(P_CS, B_CS);
    setXY(x, y, x+sx-1, y);
    for (int tc=0; tc<sx; tc++)
    {
        char* p = (char*)&data[tc];
        LCD_Write_DATA(*(p + 1), *p);
    }
    sbi(P_CS, B_CS);
}
void UTFT::setXY(word x1, word y1, word x2, word y2)
{
    if (orient==LANDSCAPE)
    {
        swap(word, x1, y1);
        swap(word, x2, y2)
        y1=disp_y_size-y1;
        y2=disp_y_size-y2;
        swap(word, y1, y2)
    }
        LCD_Write_COM(0x2a);
        LCD_Write_DATA(x1>>8);
        LCD_Write_DATA(x1);
        LCD_Write_DATA(x2>>8);
        LCD_Write_DATA(x2);
        LCD_Write_COM(0x2b);
        LCD_Write_DATA(y1>>8);
        LCD_Write_DATA(y1);
        LCD_Write_DATA(y2>>8);
        LCD_Write_DATA(y2);
        LCD_Write_COM(0x2c);
}

My current rendering:

Desired image:

TFT Lcd and Mega Board

UPDATE1

I ran henningan test from utft library, drawing sin/cos graph and simple squares

Here is attempt to render yellow square 100x100 raw data


texts: DIY 3 V -16 V, 300 watt boost converter for ultracapacitors

texts:
I am trying to build a power supply for a portable Tesla coil project using 6 × 3000 farad supercapacitors in series (16.2 V @ 500 F). I am trying to maximize the usability of the supercapacitor as the voltage drops drastically under load as opposed to batteries which supply constant voltage, and using a boost converter will hopefully do so. Any plans available for a build that can boost 3 VDC to 16 VDC @ 20 amperes will be appreciated.

Edit: initially I was planning for 800 watts but realized that is too dangerous of an output plus it will shorten the life of the capacitors, so 300 watts is somewhat more manageable


texts: Does USB connector do any thing special like impedance matching or it's just a way to connect two devices to each other?

texts:
I'm designing a board that both USB Host and device are in the same board. The host is a microprocessor and the device is a HID device which has a stm32f107 as usb device controller. What I need to know is:

Is it possible to connect my host and device data lines as differential pair on the board without any extra components like USB connectors, resistor and ...?

As in antenna connectors in telecommunication board that matchs impedance of the board and the antenna, does USB connectors do the same thing? I mean does omitting the USB connectors from the circuit affect the operation of USB communication?


texts: P-MOSFET power dissipation spike when turning off (10 - 100khz)

texts:
I designing battery charging circuit, I found the following step down converter for charging. The target is to charge a battery with 3-4 A, but the P-FET (NTF2955) becomes very hot at 0.5 amps:

I measured with scope at marked points. When the FET is turned on, and Vgs signal goes to 0 volt (turning off the FET) for some reason the voltage on drain - source arises and the current flowing through the circuit decreasing too slowly (~5-10 us) and this makes huge power dissipation on FET, its very clearly appear:

I tried between 10 - 100 khz but the result is the same.
The FET do not close enough fast? Maybe the FET is broken? Unfortunately I don't have any others to try (but its on the way). Or something else is the problem? Maybe I should add some components somewhere?


texts:
I got a container that must be heated up to atleast 250 celsius, but I don't have alot of space to work with and I am also not so familiar with this kind of topic.

So I've attatched an image which shows my design. Everything in the color dark blue or red will be in iron or steel or even stainless steel, the red container will be in the same material as the blue discs, but I've colored them to visualize what that will be going to 250 celsius and what that should not be heated at all.

I was thinking about heating it up by using the container as a resistor, shown on the second image I would have a circuit of a copper cable going into red through the container out from green and then to a power supply unit (400W, same thing that powers most stationary computers) which leaves me at 12V and X amps. I do have an N-Channel MOSFET 60V 30A and an arduino and a Thermocouple Type-K  for controlling the heating.

So my question to you is: Will it even work having the container as a heater? Or do I need some heating-resistors?

On the image below I've shown the diameter for calculation purposes. The resistance got something to do with the area through the material, and I'm sadly not sure how to exactly calculate it since it's going sideways rather than vertical.

I will be checking out this topic about once per day so if there's any extra information you need or even the model itself then I'm happy to give it to you, but since it's a blueprint of something very valueable to me I don't want to give it away unless it's necessary.


texts: Does attraction of charges or voltage cause a current

texts:
Does a current flow in a circuit due to voltage (potential difference between the 2 points of the battery) or due to the attraction of unlike charges (e.g. an electron and the positive terminal of the battery).

Also, imagine there is an ideal circuit with a 9V battery with no internal battery resistance, superconducting wires and no resistors. Since V=IR, 9=I(0). What will be the current in this case?


texts: Converting negative DC voltage to positive equivalent

texts:
Requesting some input on this topic which has already been discussed (partially for my requirement) here:
Negative to Positive Voltage Converter

I also have a positive-only display and I need to measure up to -32v DC. I need to convert the minus voltage to the positive equivalent in a simple manner and I am currently thinking of doing this in TWO op-amp stages as illustrated.

Questions:
1. Is there a more elegant & simple way to do this? Using only one op amp perhaps? The limit on +/- supply is a limiting factor hence my 2-stage design.
2. Does anyone see a problem doing it this way? This is a basic block diagram only.

Thanks for your input.
Steve


texts:
I  am looking for a CAMERA ( CMOS + Shield ) to implement on my Arduino project. I was using the LinkSprite JPEG but now is broken, I want to buy a new one but I am not sure that the LinkSprite is the better camera to use with Arduino.

The issue that I found on Linksprite was the slowness to download the picture and I couldn't to change the bitrate ( there is the command but didn't work ).

I found that there is the camera C328 that it was used for a lot of projects but now it's seems that is out of stock.

If you suggest me to rebuy the LinkSprite, do you have any example that I can take a look?


texts:
To understand modern semiconductor diodes, I looked up their simpler predecessors to get to know what is actually expected of them when I saw this circuit.
How can I do an electrical analysis of this circuit (Kvl or Kcl)?

Image taken from the book RCA Receiving Tube Manual (http://www.tubebooks.org/tubedata/rc30.pdf) Page 7


texts: RF receiver to hear all carriers at once? (to hear electrosmog)

texts:
I would like to build "radio ears", a RF receiver that would allow me to experience the RF "smog" around us as sound in my headphones. A more sophisticated version of the cellphone-to-speakers interference we all know. I'd like to walk through buildings and streets and find out which places are "quiet" and which are "loud". Or to hear that a new WiFi transmitter has been installed upstairs. Also, to hear what sources have higher carrier frequency and which ones have lower. And hear the silence when there is a blackout. Some people call this "augmented reality".

A simple crystal radio without tuning would receive all carriers (rectification only), but I would like the circuit to somehow preserve information about the carrier frequency. For example, if it were the year 1910 and the air would be full of wireless telegraph transmissions, I would like to hear them beeping one over the other in my headphones, with the frequency of the acoustic sinewaves scaling with the frequency of the telegraph transmitter's RF carrier (e.g., 1 MHz transmitter -> 1 kHz in headphones, 1.5 MHz -> 1.5 kHz).

Technically, I want to scale the frequencies, not shift them, and that is where the problem lies!

Is such a circuit possible at all? Mathematically, I want to squeeze a 1000 times larger bandwidth into a smaller one, so there has to happen some information loss. However, I was not able to come up with a reasonable mathematical description of what kind of loss this should be (its none of the simple things like low-pass, band-pass, frequency shift etc.).

Right now, I'm not looking for performance, but rather for the principle. The question is:
what kind of simple analog circuit would turn 1 MHz into 1 kHz and 1.5 MHz into 1.5 kHz?

edit: if you suggest a digital algorithm or a mathematical formulation, I'd like to stress that I need it to be (almost) real-time. To produce 1 s of output from each 1 s of input. In other words, to be able to listen to several 1910's telegraphers transmitting Morse code at the same time (and write it down with my eight hands :) )


texts:
I have setup a hackduino following this instructables http://m.instructables.com/id/Perfboard-Hackduino-Arduino-compatible-circuit/step6

This connects AREF to 5V directly. My understanding now is that this is wrong.

Is this a problem at all if I do not plan on reading or writing to analog pins of my Arduino?

Do I understand it correctly that the default is to connect the AREF via a 100nF capacitor to GND?

I have seen several questions regarding AREF that seem to indicate that, however most of them use analog read or write.


texts: Can I use a buck regulator for mains voltage if I put a resistor before it?

texts:
I am reverse engineering a consumer product that I have, and the circuit seems to be mains voltage (85-250VAC) -> resistor (10ohm) -> bridge rectifier -> buck regulator -> linear regulator -> load.
The current is around 0.3A, output voltage is 3.3V. I would expect the resistor would be a very inefficient way of dropping the voltage. The application requires a very small power supply circuit and so a flyback with a transformer can not be used.
Is using a resistor + buck regulator as a power supply okay, or is there a much more efficient way of doing so?


texts: How do Ethernet cables/USB cables send binary 0?

texts: I was wondering how your computer sends binary zero as an electrical signal. Is there a certain delay or does it do something unique.


texts:
Im new to use of mosfets.

If I was to use two Mosfets with an Arduino, would I be able to drive them both with just one digital pin connected to both mosfet's gates but opposite actions?

For example: Digital pin 2 goes High, Mosfet-1 opens a circuit, Mosfet-2 closes a circuit... and vice versa.

I'm currently using n-channel mosfets but I read about p-channel. Having p & n gates tied to one pin?


texts: How to define a microcontroller pin as open collector or open drain?

texts:
Source

I have understood the fundamental theory of open collector and open drain configuration. But the problem is how to define/make a micro controller's pin as open drain?  Can any pin of a micro controller can be used in open drain configuration??

If I define a GPIO pin as an input pin, can I use this pin in open drain configuration?
Is it mandatory to define a pin as output for using it in open drain configuration?


texts:
How many Watts DC are equivalent to 1,000 Watts AC?

For instance, my load in AC is 1,000 Watts 220V. Then, how much DC watts would an equivalent load dissipate in 12V or 24V DC system?


texts: I built a true RMS-to-DC converter circuit using AD736 chip on breadboard. The schematic is shown below. I'm a little confused with the output that I'm getting though. When I applied a sine wave of 100 mVpeak, the DC level equivalent output that I'm getting is 142 mV instead of 70.7 mV. Is this due to the crest factor of this AD736. The crest factor is 2 (Vpeak/V rms). Hence, I assume that it is giving me the output of 142 mVpeak which is equivalent to 70.7 Vrms. Did I get this correct?


texts: Spaced air core inductor wire size effect?

texts:
I'm intrigued by the second circuit in Spehro's answer and/or it's precursor (FM Crystal Radio) https://electronics.stackexchange.com/a/217086/33670

But I don't happen to have any 18 Ga solid wire, while I have a vast excess of 14 Ga and 12 Ga solid wire as construction byproducts.

The two versions of this circuit at the linked page call for 4 or 5 turns of 18 Ga (1.02 mm dia.) wire with a 12mm inside diameter.

That calculates out to 343 nH or 537 nH when I find a coil calculator that takes wire diameter as an input. Changing to 12 Ga (2.05 mm dia.) lowers it to 285 nH to  445 nH.

Using 12 Ga, if I increase the diameter to 16.05 mm (i.e. a 14mm ID) this seems to restore (nearly) the original inductance values - but then I realize that the coil calculator I'm using has no entry for overall coil length, and thus is probably assuming a close-wound coil, which these are distinctly not.

I find other calculators that let me play with length of the coil (which I note is not specified in the source, unless I'm missing it, though it can be ballparked from the stated inside diameter and photographs) but they don't have wire diameter as a variable. Nor do many of the formulas I find given on various sites. I begin to plumb the depths of what I don't know about inductance, and what effect wire diameter has on it.

Going with one of the "no wire diameter" coil formulae, 86 nH to 135 nH at D = 13mm (the original, approximately) assuming the coil length is 25 mm. If it's 15mm, 128-200 nH. Formula I'm using is  $$ I (uH) = {0.394*(Coil Radius In cm)^2*(Number of Turns)^2 \over (9*Coil Radius In cm)+(10*Coil Length In cm)} $$

Seems for 22 cm of straight wire (about enough to make the longer coil), "self-inductance" for 18 Ga is 264 nH and 12 Ga is 234 nH - not a lot of difference - 30 nH or 13%-ish. But either (rather than the difference between them) is also somewhat more than the "coil calculation" gives for the coil, in this instance. If "wire-diameter self inductance" for a given length of wire simply adds to coil inductance, it seems to be somewhere between "make small adjustment" or "lost in the noise" - if I get this correctly, which I very well might not. For self-inductance I'm simply using several web calculators that seem to agree, I have not transcribed that one into a local spreadsheet yet.

So, is that the way it works when changing wire sizes for a given widely-spaced coil - (simple addition of self-inductance for a given length of given size wire to the coil inductance for a given coil inductor with no wire diameter specified) or not?


texts:
I have a coil to make an electromagnet but I want to pass current (2.25 A) to it a little period of time (less than second) so many times and fast that I can't control the voltage-current source by pressing the button.
So what I will use is and Arduino to control it, but as you know, the current is high, so ...

What I want is a method to control de current of the DC source from the Arduino.
I already have two methods, one safer than the other. One uses just a transistor and the safer uses an optocoupler with a Darlington.

Do you think that the circuit with just the transistor is safe and I can use it, or is better to use the safer? Or is there any easier Idea?,

Thanks.


texts: Why do devices stop operating properly in extreme cold?

texts: I have noticed that a lot of smart phones say that they won't operate under -4 degrees F (-20 degrees C). Can anyone explain to me what happens when the phones get cold that stops them from operating?


texts:
I am designing a small PCB that has several digital and relay outputs. The signals to and from the board will be 24VDC, while the logic on the board will be 3.3VDC. There will also be 12VDC for the relay coils. I am using optocouplers on the inputs and outputs. I have built the circuit on a test board and it seems to work as expected. However, I have had 3 optocouplers fail during testing so far and I am not sure why. My design is basically the same as the test circuit from the K847P datasheet, shown here:

I have a second LED in series with each one optocoupler LED so that I can tell at a glance which ones are on. Each LED/opto LED combo has a resistor that should limit them to 10mA.

I am also using relay drivers (Darlington arrays) to run relays on this board. I used the extra channels on the driver to run the LED side of my optocoupers on the outputs so that I didn't have to worry about the LED current on pins of my microcontroller.

This shows one digital output:

Is there something obvious here that might be killing the optocouplers? The dead ones seem to have low forward voltage (anywhere between 0V and .7V) and open circuits on the outputs. It seems to me like the LEDs are burned out but I am not sure how that could have happened.

I have built a mockup of my board by hand and it has six of these 4 channel optocouplers. So far I have one with all 4 channels dead, and two with 1 dead channel each. This seems like too high a failure rate to be coincidence to me.

UPDATE BASED ON QUESTIONS: I have used an oscilloscope to watch the 12V bus, the 3.3v bus, and across the relay coil terminals while switching one of my relays on and off. I did not see any transient voltage spikes. I think the snubber relays on my relay driver are doing their job, which lands me back at square 1...

Also from a comment but moving up here for visibility:
The optocoupler is a Toshiba TLP291-4 and the darlington array is a Texas Instruments ULN2003A. I was also using a K847P optocoupler to test on a breadboard and discovered a burned out channel on that one as well, so I would guess it isn’t something specific to my optocoupler choice.


texts: Are these AC wires in this cable swapped?

texts:
(I am located in the US)

I'm taking apart a cable to use for AC in a project.  When I stripped the ends, I saw the expected Black/White/Green colors to indicate hot/neutral/ground respectively.  However just to be sure (before using the cable) I traced each with a multimeter.  What I found was as below, however their positions on the plug are REVERSED from what I would expect to find in an AC plug in the USA. (As indicated in any number of the results from e.g. this Google Images search)

Am I correct, that I should be using this cable's BLACK wire for neutral, and it's WHITE wire for hot?


texts: DALI: Resetted short addresses but now ballasts not responding to COMPARE?

texts:
I currently have a DALI set-up with three LEDs.

All LEDs turn off when sent a broadcast command to turn off, so the set-up is wired correctly.

I have removed all of their short addresses according to the procedure outlined here and a search from 0-63 with QUERY STATUS reveals that there is no assigned short address to any of the ballasts.

I have sent out INITIALISE with second byte 00, twice within 100ms, to target all operating devices. I have sent out RANDOMISE twice within 100ms. I set the high, medium and low addresses to FF (i.e. the 24-bit address I'm searching for is 11111111 11111111 11111111) and have sent out COMPARE.

Previously I was able to get a response from this procedure but today I am not getting a response from any of my lights.

I am currently using a Raspberry Pi with this AL-DALI-HAT to control my DALI lights. I interpret an "N" and an "X" as no response.

Can anyone suggest debugging steps or if need be how I can hard-reset my DALI lights?


texts: Is there a digital input that registers light? / Can only ADC pins register signals from an LDR?

texts:
I have been building a traffic light over the past year as a GCSE project. Initially, what was unique about it was that, the pedestrian interface would light up when it was dark outside. Subsequently, I added a qualitative counting system for drivers so they would know how long was left but couldn't jump the lights at 1 or 2 seconds.

Now to my current dilemma. Apparently, all of the above doesn't differentiate my project enough from the current model. So I thought, what if you no longer needed to press the light button. What if you could just walk up, and an input would register the movement and start the process. I thought about having a laser pointing at an LDR and when the laser point was obstructed by a person for example, the ldr would register this and start the cycle. Unfortunately, my chip only has 1 ADC pin, so i can't use the LDR. I was wondering if there was an input that could register this obstruction of light and then transmit to the chip.

Side Questions:
Can a non ADC pin register an ldr
Are there such things as infra red lasers e.g. a laser point which can't be seen to the human eye
Can an optoisolator replace a normal PTM switch

EDIT:
I have done some research and found something called a photo transistor which by my understanding could replace a switch. Is this a viable option?


texts: Ethernet LEDs won't turn off when i unplug the Ethernet cable

texts:
I'm working on a custom board equipped with a Ka-Ro TX28 module and the LAN9500A USB to Ethernet controller without EEPROM for the network interface. Operating system is Linux (Yocto). The LAN9500A is connected to a RJ45 jack with integrated Magnetics and LEDs.

I can see the LAN9500A is detected and correct driver is loaded..., Everything works fine when a cable is plugged...

The only problem is that when I unplug the Ethernet cable from the RJ45 socket, Linux does not detect it, and the status LEDs stay ON or may be blinking... However, if I again plug the network cable, link goes down then up again and it works okay...

Does anyone have any ideas?


texts: Multiple hall effect sensors in proximity

texts:
I'm interested in using a linear Hall effect sensor to measure displacement varying by about 1.5 inches. The idea is I have a piston with a magnet at the end and a Hall sensor at the end of the cavity to output a voltage roughly proportional to the proximity of the magnet.

Question is, what if I have several of these pistons side by side? They need to be less than half an inch apart. Will they interfere? I understand that the Hall sensor is only sensitive to magnetic field lines perpendicular to it. Does that mean that the magnetic field from a magnet displaced half an inch away horizontally will not register a voltage?

Thanks guys.


texts: Is there anyways I can take apart a microwave (any kind) and some how plug it into my computer and control it from my computer? Where to start... where to start...


texts: Transmit 7MHz analog signal from board to board

texts:
I want to transmit real passband analog  single ended signal with bandwidth, 0 to 7.3MHz, from board to other board. distance from these board will not be more than 15cm. what's the best choice for wire interfacing these boards?
The signal is exactly pure sinewave between 0 and 7.2MHz, it's beat signal of FMCW RADAR. Thus it may become DC (0.00000001%).
Update:
The boards are FMCW radar front end and the other is processor.
Update:
signal is 2.7 p-p, I'm not sure how to determine the systems SNR yet!(Other question has been created for this issue)
update:
you can assume SNR is good :)
Mistake confess:
O O, I made a mistake, my sampling frequency is 7.2MHz and the analog bandwidth will be less than 3.6, but I think it not too different.


texts:
let me start off by saying I am a computer science student so I'm not familiar with electronics whatsoever. Anyway, I am faced with this problem:

I am given some input (say, a sine wave) centered on 0V (Peak to Peak is, say, -5V to 5V). I want to make my output signal with a Peak to Peak of 5V to 15V, how would I approach this? One attempt at the solution was the following circuit i got from googling -

The circuit managed to change the DC offset but the peak to peak is not where I want it to be. Are there any other circuits I could try? I read somewhere that a non-inverting amplifier (with an op-amp) may change the offset so I will attempt that next.

Any thoughts?


texts: Inter-PAN transmission possibilities with XBee modules

texts:
I'm trying to create a working ZigBee Light Link device using common XBee modules. Now I've ran into a problem where Digi the creators of the XBee modules can't help me either.

I'm trying to find out if it's possible or not to use inter-PAN transmission with these modules. And if so how?


texts: Can I use pwm to control speed of at motor driver?

texts:
Ive got this motor driver from Sparkfun, https://www.sparkfun.com/products/9670. Where I get it that setting ENA and IN1 to high will enable connected motor 1 to og full speed in one direction.

But, can I connect IN1 to pwm and in that way control the speed? For instanse, instead of full speed I could get 50% speed by adjusting the dutycycle? And if I wanted I could read CSA pin to get the actual break "force"?


texts: How to continuously sample a signal WITHOUT using a trigger?

texts: Hi all I am trying to sample a 5 MHz square wave signal with jitter as a source of entropy using my oscilloscope (Tektronix MSO 3054), however, I don't know how to turn off the trigger while I am sampling (at a rate of 5 MHz) the data. I need to turn off the trigger because it affects the entropy of the measured voltage points (causing most of the measured points to be zero). I am also trying to collect this data from my pc using NI Signal Express which seems to require a trigger to be set until data collection can start. Any guidance would be appreciated on how to sample this data without using a trigger.


texts: How current can flow through open circuit output and 9v across diode?

texts: ,how voltage across diode can be greater than 0.7 volts in forward bias


texts: I need help designing a speed control dc motor circuit

texts:
We were asked to design a motor speed control circuit using the following components:

15V source -> potentiometer -> LPF -> OpAmp -> ADC -> DAC -> OpAmp -> Motor Driver -> 3V DC Motor (because of its low cost)

I am going to wire this on a breadboard.

1. First things first, I have a 15 and -15 Source (VCC, VEE)

1.1 (Update) I have two 20k resistors before the pot so I would have finer control over the motor (-3V to +3V)

2. A low pass filter with a cut off frequency of 100Hz (My prof suggests that we use this value just to clear unwanted signals)

3. An OpAmp with unity gain because I need something to drive the transistors from the high-impedance output of the pot.

4. A push-pull amp configuration that consists of the NPN and PNP transistors so that I can make my motor spin either way (i.e., a motor driver).

So my questions are:

Are my resistor/capacitor values practical?
How do I implement the ADC -> DAC part?
Do I need to place a resistor before the pot so that it won't burn out due
to high voltage?

Notes:

No PWM.
The motor driver circuit can also be an H-Bridge circuit or IC but I think that would be more expensive.

I also need some suggestions on how to improve the circuit.


texts: Communication between 3 Atmega controllers

texts:
I am studying a bio chemistry analyzer, in which there are Main controller, printer board controller and detector board. To establish communication between these three, RxD pin of one controller is connected to same (RxD) of others and same with TxD (all ic's TxD is interconnected.

Is this type of communication possible (Normally we connect TxD to RxD and vice versa)? How they are communicating then? Which protocol is used (I2C,SPI or USART).

How will be master and slave configuration?


texts: Getting wrong answer for problem involving transfer functions and Laplace transforms

texts:
I need help finding where I have made the error in this problem set by my control systems lecturer.

The Question:
The output of a linear time invariant system for an input \$r(t)\$ equals \$c(t)\$. If the input signal is passed through a block with transfer function \$e^{-s}\$, and then applied to the system, what will the output, \$y(t)\$, be?

The answer should be \$y(t) = c(t) \cdot u(t-1)\$ but I get \$y(t) = u(t) \cdot c(t-1).\$

My working:

Transfer function one, \$H_1(s)\$, applies to the original system.
Transfer function two, \$H_2(s)\$, applies to the system including the new block:

$$H_1(s) = \frac{C(s)}{R(s)}$$

$$H_2(s) = e^{-s} \cdot H_1(s) = \frac{e^{-s} \cdot C(s)}{R(s)} = \frac{Y(s)}{R(s)}$$

Therefore \$Y(s) = e^{-s} \cdot C(s)\$,

\$y(t)\$ is the inverse Laplace transform of \$Y(s)\$:

$$y(t) = u(t) \cdot c(t-1)$$


texts: Why is the voltage across the capacitor constant?

texts:
I've connected a 6V DC voltage source via a 1Ω resistor to a 1F capacitor. I was expecting the simulation to reveal a less constant t-vs-v graph: it would start at 0 and after a while stabilize at 6 volts. But it seems that the voltage across the capacitor begins at the source level and remains so. Two questions:

Why is the voltage across the capacitor constant for the 10 seconds?
(Secondary) Why isn't the current through the resistor I = V/R = 6/1 = 6 A (at least while the capacitor is being charged)?

I'm making my first steps in electronics. Any feedback would be very helpful to me.

Solution.  Thanks to everyone for the feedback. Lack of reputation doesn't allow me to upvote them, but all were very helpful to me. Turned out that I didn't check "use initial voltage", so while the initial voltage of the cap was set to 0, it wasn't being used:

Circuit designed and simulated using SystemVision.


texts: How to connect 1.5mm SMT alternating pins to 0.1" pin header?

texts:
I have a toy I'm trying to rehabilitate - the microcontroller was fried and I'm attempting to replace it with an Arduino.

It looks like the connections were at a SMT pin-pitch (1.5mm spacing).  To work with breadboard and jumpers, I'd like to install something that terminates in a female pin header with breadboard spacing (0.1" pin pitch).

What is driving this: as you can see in the photos, I have a sort of janky setup where I've soldered each individual contact of a ribbon cable.  This is not a mechanically sustainable solution! The pins are breaking free.

I'd like something that is more solid, for example a cut-to-size PCB with the (mystery SMT contacts) on one side and a pin header on the other.

So my questions are:

What would be the best way to get this to end up having a 0.1" pin header?
What is this SMT alternating connections pattern used on the motherboard called?
Is there a thing I can buy that will connect to the SMT alternating connections?

Pictured is the motherboard, with the empty slot that once held a daughterboard, which in turn had a microcontroller.  Note that you can see the ribbon contacts breaking off.  The connectors on either side alternate and never line up with each other.

Here's a photo of the original daughterboard with the connections.  A fried, blob-covered microcontroller chip is on the other side.


texts: Transmission order of lower and higher priority messages in the CAN bus

texts:
I would like to ask a theoretical question which is about the CAN bus protocol.

Let's say that we have three nodes, namely A, B and C. First message which has lower priority is sent from A node to C node. The second message which has higher priority is sent from B node to C node during the transmission of first message.

Is the lower priority message going to be processed before high priority message or is the lower priority message going to be stopped?


texts: Detect stepper motor movement using a Hall Effect sensor

texts: Is it possible to detect that a stepper motor is rotating using a Hall sensor against its body? Kind of a simple detection mechanism for motor stall without moving parts.


texts: Calculating resistance with a multimeter

texts: I recently took on the job of working on someone's amplifier. There was a burnt smell coming from it. I found the pieces of the puzzle that were fried and replaced the ones I could, two diodes and two resistors. There's a third resistor, however, that was completely blackened. I can't read the color code so I can't tell what resistance is it. I haven't used a multimeter since high school because I primarily only work on guitars and they're simple enough to work on without one. Can someone walk me through the steps of calculating the resistance so I can order the part and get this amp back to the customer? Thanks.


texts:
This is the circuit:

I saw it in a book. It said that this is a 7th order circuit.

From theory we know that the order of linear passive circuits is determined by the sum of capacitors and inductors, minus  the number of Inductor-nodes (a node where only inductors meet), minus the number of capacitor-meshes (a mesh that has only capacitors on it's branches).

This is my attempt to verify the order.

Capacitors + Inductors = 11

That component to the leftmost part of the schematic, judging from the way the book is illustrated previously, is just a complex electric impedance, so I believe that we can't do anything with that component. It doesn't count neither as capacitor, or inductor. It may contain 10 inductors inside but that's irrelevant, in order to find the order of the circuit (I'm not sure about that though).

Far to the right (my rightmost arrow) the inductor and capacitor can change their place without the circuit being affected in any way, so we have an inductor node.

Another inductor node exactly to the left of the previous one.

And one capacitor mesh, that I have marked to the left.

Therefore the order is 11 - 2 inductor nodes - 1 capacitor mesh = 8, not 7. So I'm clearly missing something here and I have no idea what it is. The way this problem was presented in the book seemed more like a trick question.

I will appreciate any help on this! Thanks in advance!


texts: What is this circuit called? (Dual of a boost converter)

texts:
A boost converter is a circuit that uses power from a voltage source, to act as another voltage source with a greater voltage. To conserve power, it draws more current from the input than it provides to the output. A boost converter looks like this:

(image from Wikipedia)

The general idea is to charge the inductor up (with the switch closed) then discharge it through the load, in series with the power supply. The capacitor is for smoothing the output voltage, and the diode allows the capacitor and load to retain a voltage while the switch is on (it prevents the capacitor from discharging through the switch).

The following circuit uses power from a current source, to act as another current source with a greater current. To conserve power, it "draws" more voltage across the input than it provides across the output.

(shown in LTspice IV) Here Q1 and I2 represent the switching element - I2 is a pulsed current source.

The general idea is to charge the capacitor up (with the switch open) then discharge it through the load, in parallel with the power supply. The inductor is for smoothing the output current, and the diode allows current to continue circulating through the inductor and load while the switch is off (it prevents the inductor from discharging through the switch, and damaging the switch).

What is this circuit called?


texts: Is there an advantage in using 8-bit mode in 16x2 LCD displays?

texts: Since almost all 16x2 LCD displays support 4-bit mode, and as it seems to be pretty efficient, is there a reason why they have 8-bit modes? I am using a JHD162A display with my Arduino Mega. Since the Mega has a lot of pins unused, I was wondering if I should use the display in 8-bit mode, if that could improve something. I do realize that I might be able to save a bit on the time factor by writing all 8 pins at the same time and not having to wait for the latching, and I just want to know if there's something else.


texts: Since I2C, SPI, etc all communicate bits in some serial fashion, is there an equivalent name to refer to the type of communication/protocol that occurs on the TX/RX pins (associated with UART) of a micro-controller other than "Serial" regardless of whether its voltages are TTL (3.3V,5.0V) level or RS-232?


texts: Running following circuit in under 18mA and 15-20V.

texts: So i build above circuit to drive a high frequency transformer that have Primary 10 Turns, Feedback 8 Turns, and Secondary winding of 1350 turns.It works great for my application with 7V input and drawing .2-3A current. But i was wondering if i could bring it down to work under 15-20V and 18mA power supply. Also is there anyway to limit current drawing through the circuit. Q1 is MJE182 - NPN transistor.


texts: How do you structure large embedded projects?

texts:
Background:

Junior R&D electronics engineer (the only EE in the company) -
the hardware and the coding is not the problem. My biggest issue is getting a proper overview of the project, and where to start.

So far I've only made minor software projects (sub 500 lines of code), but I can't envision myself doing larger projects without losing overview of the functionality or lack of functionality.

How do you best structure / what tools do you use to structure large embedded software systems?

What I'm currently doing:

I usually start out, by sketching the functionality of the project.
It could be one to many layered flow charts or related diagrams (block diagrams, etc.) and doing some research of the components/chips. Then I jump straight into coding (fail fast I guess) while referencing the datasheets / Internet,
Coding one functionality at a time and testing it with dummy data, or similar test. It could be writing data to a MEM chip, and then if that works then
it could be an SPI driver between the main chip and the MEM chip.

What answer I'm looking for:

Anything really. I will sort out what I find sensible. It could be a book, an article, personal experience, recommendations, etc.

I'm very interested in knowing how seniors tackle this.

Edit

First off, thank you for sharing your years of experience! All the answers are much appreciated. My take from this is;

Create a clear and precise specification document.
Create a software design document. (Something I will now add)
Design doc templates
Think in modules how ever redundant it may seem. (Something I need to focus more on)
Follow a coding standard for structuring header/source files. (Never did this)
Barr Group C standard
Focus on creating the low level implementations first. (Communication etc.)
Implement design patterns where ever possible/sensible.
Design patterns
Set up something for revision control (Github etc. - never used this much)
Research continuous integration / continuous deployment (Something new I stumbled upon)
CI & CD basics


texts:
I'm trying to create a schematic for powering 196 LEDs (yellow, 2.1V, 20mA)
by using 2 or 1 of these LED drivers
STP16CPP05 which is 16 channel (40mA per channel)

LED series/parallel calculator says:

Solution 0: Source voltage: 14.7V = 7 x 28 array uses 196 LEDs exactly
R = 1ohms
the array draws current of 560 mA from the source.

Solution 1: Source voltage: 30V = 14 x 14 array uses 196 LEDs exactly
R = 33ohms
the array draws current of 280 mA from the source.

my input voltage will be 12V battery, so my questions are:

what is more power efficient to boost voltage to 14.7V or to 30V?
do I really need the resistors?
am I better of by designing the LED array for 12V input?

I'm also having some trouble of picking the right switched regulator and calculating the necessary resistor and other values to boost the voltage to 14.7V/30V

Can anyone recommend a good average priced regulator (SMD that can be hand soldered) and help me out with the math?
Any help is greatly appreciated.


texts: How to find the current in this circuit?

texts:
Please help me find the current flow in A1,A2 and A3. its my First FEE class and I was able to solve this with voltage source but with current source Iam Having trouble.
also V1 and V3 are the voltages that also need to be found. any idea on this ?
any help would be appreciated.

Spent the last 7 hours and tried all solutions best I know how with no luck getting the same values as the simulated results.

P.S I need to solve this manually.


texts: Why does the stator field rotate at the same speed as the rotor field in a synchronous generator?

texts:
In the case of the induction motor the rotor never catches up with the rotating field of the stator because if it did the induced voltage would be zero as there is no relative movement between the rotor and the stator field.

What changes in the synchronous generator that makes the stator field rotate as fast as the rotor field?

(!)If they rotate at the same speed,there is no relative movement.So how is the voltage induced and the current that creates the revolving stator field produced?(!)

However, there is relative moment between the rotor and the windings. Is this what causes the current?

Edit: I completely understand how the induction motor works. What I'm trying to work out is the synchronous generator and why isn't there a problem if the rotor and stator field are synchronized as there is in the case of an induction motor leading to the 'slip'. Why don't we have a slip in the synchronous generator?


texts: How do you split a summing point into two?

texts: I am solving a control system example on block reduction rules and stuck on this particular step. According to me, I can move the summing point ahead of the middle block to get G4 multiplied to both but that would not get the summing points in the form that they are in the next figure. Would appreciate any help or pointers on this.


texts:
I have a circuit with a voltage of about 150 volts but with just about 1.75 mA current draw. Will I be alright with a 1K, 3K or 5K 1/2 watt or a 1 watt potentiometer to adjust and dial in the voltage?  This is sometimes nice for a microphone in order to get the desired sound.  I would of course rather use a 5 watt potentiometer but I will need to order one.

What kind of power rating do I need for a potentiometer if I run 150V across it?


texts: What do the inductors L2 and L3 do in the following rf power amplifier circuit?

texts:
I found a circuit online about an rf power amplifier working in the 88 to 108MHz FM spectrum. The circuit diagram is shown below

I understand that an amplifier needs an inductor and a capacitor in a resonant circuit to build the output waveform without distortion. But why are there 2 inductors over the collector of the transistor and another inductor L2 near the output.


texts: SD card with STM32 in memory-mapped mode

texts:
I need an external flash in STM32H743 MCU and it must work in memory-mapped mode (it's necessary for LTDC display controller). Can I use SD card instead of usual flash chip in this case?
It will be connected to qspi controller like single spi flash memory.


texts: How to identify the value of a SMD resistor soldered on a board and without marking?

texts:
How to identify the value of a SMD (surface-mount device) resistor soldered on a board and without marking?
I suppose it is in 0603 package considering my measurements.

Is there a way to do that? Or should I remove it from the board, test it, and put it back?

The context is that I have a Phottix Mitros+ speedlight flash which had an internal damage (a small explosion) when a screw came into contact with an internal circuit board. I have another fully functional flash on which I clearly see a SMD resistor and I would like to identify what is the value of the resistor to replace the one that grilled in the damage flash.


texts: I have a 48vdc to 120vac inverter with a 3 wire output (hot, neutral and ground). I installed a GFCI outlet using those output wires. I tried putting a resistor (I tested with 1k 100 and 22 ohm values) between the hot and ground but the outlet doesn't trip. Using the same resistor on another GCFI outlet connected to the grid, will trip the outlet. When I press the test button on the GFCI outlet connected to the inverter, the outlet will trip. The inverter ground is grounded. I get 120v from neutral to hot and 60v from neutral or hot to ground. It seems like the GCFI won't work if you were to make a circuit to ground. Any ideas of what is happening?


texts: I want to repair an LED Christmas light string with 3 wires per bulb. How is this string wired?

texts: My prelit tree has strings of LED lights and each bulb has three wires going to it.  Looking on the web there are a number of sites that describe how to repair strings wired in series that have two wires per bulb.  However I cannot find any reference to strings with three wires per bulb.


texts:
the company i work for has tasked me in rebuilding an old LED sign we had replaced. (newer led rgb version) The driver board that was in the sign has gone out. So i am trying to rebuild the driver boards.

The boards are 8x8 for a total of 64 leds per board and 32 boards.
I have done multiplexing of led's before the problem i am running into is that the board is NOT set up as the following....

however, they are set up as the following

As you can see they each have their own pin but share a common ground.
I am having a problem finding something that can control that many leds at one time that can be expanded to 32 other panels.

I found the Mux Shield II over at sparkfun but i dont think its big enough to do what i want.
What am i missing there has got to be something out there that will control 64 leds at a time!

Also the led boards are RED led's only. no RGB


texts:
My question is a pretty direct follow-up to this one. I have what looks to be the same amp, with the same burned part, and it happened after leads were hooked up reverse when jumping my car. The selected answer says it should work with the part removed, albeit without reverse-polarity protection. I have some pictures of the part, it kind of split as I removed it, it seemed that there wasn't certainty as to what kind of component it was without further info. I would love to replace the component, but the pads are completely burnt out.
My question is: with the further information about the part (diode?), will the amp work if I put it back in my car, albeit without protection, with the component removed, as assumed before?


texts: Unused twisted pair termination with RS-485 on 8P8C

texts:
For my digital electronics project, I'm making a device which will among other things have RS-485 communication.

From what I've seen, the recommended cable type for RS-485 is twisted pair, and one of the requirements for my project is that the communication doesn't need more than one pair of wires, so the two ideas fit in more or less nicely.

The most elegant way to actually connect the cable to the PCB that occurred to me was the RJ-11 jack. Unfortunately, it's heavily associated with telephone use and all suitable telephone cables I could find here were flat. From what I've seen, it's almost impossible to actually find the twisted pair telephone cable which will nicely mate with the RJ-11 plug. So to solve that problem the next best thing to me looked like the 8P8C connector and standard network cable. The middle pair on the 8P8C will connect with the middle pain on the RJ-11 jack, should I manage to get twisted telephone cable, and all network cables that are commonly used with the 8P8C already have twisted pairs, so it looks like the twisted pair problem is solved.

One thing that bothers me is what should I do with the 3 remaining pairs in the network cable?

The communication will be simplex and each device will have it's own ground-isolated power supply. In some tests I did with the unused pairs floating the communication worked fine at the expected cable length (around 50 m in my case) and at much higher data rates than those which will be used in the final design (115200 b/s in test and 9600 b/s in the final design), so one option is to just leave the pairs floating. That seems a bit wasteful to me so the other idea that I thought of would be to use the unused pairs to make sure that the voltages between the grounds of the two devices are within the specified values. It also seems a bit wasteful to me to use 3 whole pairs for that. Unfortunately I'm out of ideas what to do with the remaining pairs.


texts: Calculating Data rate function of bandwidth and SNR

texts:
I plotted BER vs SNR for BPSK modulation in Matlab and I am given bandwidth of channel (bandlimited channel). lets say it is BW1. I would like to find the data rate based on this information. I am using Shannon capacity formula: Therefore

C=BW*log2(1+SNR).

However I wonder for this equation the bandwidth is actually bandwidth of my channel or not? also what is the SNR since in Matlab we usually loop through the eb/No and call that one SNR can I use that value for SNR or should I convert it to real SNR by multiplying by a constant?


texts: Resistor in series and capacitor in parallel to ground

texts:
Could somebody tell me why someone would need circuit like that in supply rails?

I assume it is for making DC voltage smoother by parallel capacitor.

However, my 24V power supply has 500mA output (I am going to feed amplifier with 12-0-12 V instead of 15-0-15V).

So 10Ω does nothing in this case to decrease current level.

Do I need a minimum 100Ω or 1kΩ protection resistor or not? I read that an amplifier should have no more than 5mA current flowing. Or does that concerns only inputs?

If I put a 1kΩ resistor, should I change the capacitor?


texts:
I have designed a circuit to measure impedance of certain tissues. It injects a constant current from two electrodes and measures the voltage at different electrodes. The system mainly consists of a frequency generator, voltage controlled current source, some multiplexers connecting the electrodes and then the measurement circuitry.

When I connect different resistors between OUTA and OUTB I can verify the circuit is behaving as expected. However, when I connected the secondary board with multiplexers, the output suddenly changes to a distorted waveform centered around 5V.  The same occurs if I bring my hand close enough to the OUTA terminal. This does not recover until I restart the frequency generator.


texts: Should Ethernet MDI Pairs all be Length Matched (Inter-Pair) before going into magnetics?

texts:
I've been trying to find information for the above question and I can't seem to find anything. I have 1000 BASE-T lines coming from an Ethernet cable to a PCB mounted connector. I'm pretty much confined to the area shown below:

The lines are not matched inter-pair (some are mismatched by 100 mils), however, they will be matched intra-pair. How important is it for the differential pairs to be length matched (inter-pair wise)? I've gotten conflicting responses from my peers that they do not need to be matched inter-pair wise and I can't seem to find any info online in regards to 1000-T.

Much help appreciated.


texts: Why does my ceiling fan spin the wrong way?

texts: My ceiling fan blows are at the ceiling (uselessly).  At first, I wondered whether I could fix it by maybe removing it and switching some kind of polarity.  But is there a polarity?  Aren't the residential power wires live and ground?  How does the fan know which way to spin?


texts: Measuring Resistance/Impedance with SPICE

texts:
How does one measure impedance/resistance using SPICE?  I have access to regular SPICE(MacSpice) and HSpice.

The DC current divider circuit at the bottom of this webpage seems to be one method.  0V DC sources are used, and the current through these zero volt sources is measured.  Using the node voltage and the current measured, we can deduce resistance.  Of course for circuits where we already know the resistance this is only good for measuring the current.

How can one do resistance/impedance measurements for AC circuits, such as the inputs or outputs of transistor amps (e.g. resistance looking into base, output at emitter, etc.)?


texts:
I want to use a counter MC100EP016A which requires PECL clock input.

What is the difference between LVPECL and PECL?

If a clock source provides LVPECL clock  how can I use it with the MC100EP016A IC?


texts: How to migrate from Teensey LC to Final PCB?

texts:
Im an new to Teensey LC. So the following question is a beginners question on Teensey LC.
How do I migrate from a Teensey LC to a final PCB?
Is it similar to migrating an Ardunio to a bread board -where DIP ATMEGA is used , with crystal, and capacitors and so on?-if not similar whats the procedure?
If so where do I get DIP version of CPU in Teensey LC?


texts: How to calculate error amplifier output in amplifiers

texts:
I'm trying to derive an accurate formula for the output of an error amplifier in the class D amplifier I'm simulating. Most literature on the error amplifier/integrator in class D amplifiers glosses over the technical details and and some even contradict eachother in how it works.

In the previous question I asked here, we found the transfer function of an ideal summing integrator:

$$ V_{\text{OUT}} = \frac{V_{\text{FB}}}{\omega R_{\text{FB}} C} + \frac{V_{\text{IN}}}{\omega R_{\text{IN}} C}$$

I tried applying this to my simulation but come up short. My understanding, based on the simulation is that the circuit integerator acts as a filter to the sum of the two inputs with a -3dB frequency at roughly 41kHz. I'll attach pictures of the simulated results below at 1kHz but i increased frequency until i got 3dB attenuation and it was around 41kHz.

My question is, how can the equation above be accurate when it depends on frequency and a lower frequency means a higher gain? At 1kHz using the values of the simulation below at t = π/2:

$$ V_{\text{OUT}} = \frac{-1.6}{2 \times \pi \times 1kHz \times 5.9k \times 220pF} + \frac{0.95}{2 \times \pi \times 1kHz \times 3.6k \times 220pF}$$

$$= -5.28V$$

This does not match the plotted value of roughly -3.7V. This calculation becomes more wrong as the frequency changes. In the time domain, the integral equation also does not make sense with huge numbers generated by the time constant 1/RC. How can I mathematically express the output of the error amplifier in the below circuit better?

Circuit is a unipolar PWM switching class D amplifier at 500kHz.

To be clear: Green is input, Red is feedback signal and contains 1MHz triangle wave ripple. I assume this ripple is caused by the 1/RC relationship on the differential amplifier (U1) where the square wave inputs are attenuated and integrated. And blue is the output of the error amplifier/integrator (U2).

Edit: From the advice of Sunnyskyguy EE75, i'll attempt to construct a transfer function based on the loop shown below.

G1 is the preamplifier gain that is not included in the simulation.

H1 is the differential amplifier gain:

$$H_1 = -\frac{R_2}{R_1}V_{\text{OUT}}$$

Vout is a peak to peak sine wave of roughly 12V so this makes sense with resistors R2 = 1k, R1=6.8k looking at the waveform.

G_PWM is simply Vint as a ratio of the carrier signal which is a triangle wave 500kHz +/-4.2V:

$$G_{\text{PWM}} =  \frac{\left \lvert V_{\text{INT}}\right \rvert}{4.2} \times V_{\text{DD}} $$

Gint is still unknown to me.

VN is noise introduced from switching/deatime.


texts: prox sensor with NPN open collector output or a dry contact

texts:
I am totally new in this field. I want to use a 5 V / TTL signal from a National Instrument to switch on/off a Red lion PXU series temperature controller. But this controller required a dry contact input or a prox sensor with NPN open collector.
What does it mean?

How will the circuit look like?

Thank you in advance!


texts: Unsure of transistor to use for LED strip

texts:
I'm trying to control an LED strip by means of a Raspberry Pi, replicating what is done here: http://popoklopsi.github.io/RaspberryPi-LedStrip/#/

It recommends using the IRLZ34N transistor between the Pi and the lead for each color in the strip.

However, in my lab we have about a dozen different transistors - none of which are the IRLZ34N. I do not have enough background knowledge to determine which other ones may be used interchangeably here. The Pi GPIO pin output is 3.3V, and the LED strip takes 12V, and will consume approx 32W when all LEDs are lit.

On the bench I see MJE3055T, MPF102, TIP31A/32A/102/120, among others (but the aforementioned appear to have similar form-factor to the IRLZ34N). Are any of these interchangeable?


texts: Estimate the power consumption of a C program without hardware

texts: I have a C application running on TI CC2650 SENSORTAG microcontroller that performs gesture recognition. Is there any way I can figure out its estimated power usage probably through Raspberry Pi or something, so that I can use it to compare the actual power consumed when I synthesize it on a FPGA? This is an academic project targetted at Hardware acceleration.


texts: I am trying to find an equivalent circuit for autotransformer. But there is no any source about it. I tried to solve something about it. Can anyone have any idea about it?


texts: Usage and charging of 2S Li-ion batteries

texts:
The BAK 18650CA-2S-3J is a 2S 7.4V battery I am interested in using - however I am unsure of the workings of the device. The image here (and farnell page) shows a 3 cable interface - what is the purpose of the  third (middle?) cable? is it for balanced charging only, or is there a 3.7V source also available form here?

Further, what type of chargers are appropriate, with the correct 3 terminal  connection to charge this battery?


texts: How can I work out the efficiency of two different solar panels (12V and 24V, and both of different makes i.e. different efficiency each one) connected in series?


texts: S domain transfer functions of full bridge inverter

texts:
I need to design an inverter circuit as in the schema. It is driven by the unipolar PWM method. I have a problem with the circuit. It would be great if anyone can help me.
I want to get the s domain transfer function of the circuit from the duty cycle(reference voltage) to output voltage while consisting of the effect of the DC voltage source. So far I am not able to handle to linearize switching actions properly. I know how to do it in a more simple topology like buck or boost but here I am confused

simulate this circuit – Schematic created using CircuitLab


texts:
Hi Guys, I am a newbie to electronics but love to get started learning. So after a few google searches and YouTube videos, I have decided build my own variable Power Supply using an old Computer ATX Power supply for my further learning and future projects.
When I take the power supply apart, the first thing I've noticed behind the AC main input male socket was 2 capacitors from L & N parallel to the Ground, a resistor across L and N. Also some component packed in white plastic across L and N.
I have learned to purpose of resistor and capacitors. But cannot control my curiosity why such configuration needed in an AC input(at least in this case)? Also what is the component in white package? Please excuse if this is a stupid question. I hope someone can explain. Thanks in advance.


texts: Which Machine out of Induction machine, separately excited DC machine and permanent magnet DC machine will have the highest Torque to weight ratio?

texts: Which factors affect this ratio. I am aware of the general statement that Induction machines are bulky and have seen DC machines that appear to be compact and light weight, but I am stumped at comparing the torque produced by them.


texts: What to think about when designing HF PCB's?

texts:
I am currently designing a small PCB in Eagle Cad that has a GPS 1PPS signal (one short pulse per second) as input. The pulsetime for the 1pss is something like 1us.

Ok, I know thats not super HF but still.

What are good design practises when designing PCB's for HF?

Are curved corners of routes better then perpendicular?
Is thicker routes better than thin or opposite?
Groundplane = good?
etc..


texts: I had seen a machine (electro-surgical generator) used for surgery purposes; it had a digital interface having 7 segment displays on the front board. It was using a PIC18f452 and a Atmel EEPROM 24C64. What's the use of a microcontroller in such machine? Traditional (electro-surgical generator) machines use knobs and switches; why is the micro-controller actually used?


texts: How do you make the LEDs come on for a PS/2 keyboard?

texts:
I'm making a simple console type thing for the mbed with a PS/2 keyboard and VGA monitor. I have a PS/2 library working and can receive scancodes and such. I want to go above and beyond what it allows though and also allow for the LEDs such as caps lock on the keyboard to come on as appropriate.

I know how to do this from an abstract message type perspective and have done this before on x86 PCs before. However, I don't understand how to do it electrically and keeping the clock signal and such in mind. Every reference I've found for PS/2 keyboards just drops to x86 assembly code, which doesn't handle how the PC keyboard controller actually works at an electronic level. I mean, how do I know when the keyboard is idle and I can send a command? Does the keyboard set the clock rate or do I for sending commands? There is only a data and clock line, so I don't understand how to send data back to the keyboard.


texts:
According to various sources something as little as 0.01A = 10mA can be painful, at 0.1A = 100mA you can expierence *

"ventricular fibrillation of the heart".
"an uncoordinated twitching of the walls of the heart's ventricles which result in death".
"As well as other painful things such as extreme breathing difficulties, Severe Shock, Muscular paralysis ...".
*

How is that true? I've worked with an arduino and LEDs, LED Strips etc for quite a while yet never heard that 10mA can be painful let alone 50-100mA deadly.


texts: Problem with Network Topology based on circuits

texts:
I have started reading a book lately which covers an introduction to electric circuits. Currently, I'm trying to learn the basic network topology needed to solve exercises in a more efficient manner. To help me understand where I'm mistaken I'll describe you the circuit you see below in topology terms :
BRANCHES
This circuit has 5 branches :

3 resistors.
1 Voltage Source.
1 Current Source.

NODES
This circuit has 3 nodes :

Node a where R1 and V1 are connected.
Node b where R2, R3 and I1 are connected through cables.
Node c where the V1, R2, R3 and the I1 are connected through cables.

MESHES
This circuit has 2 meshes :

abca.

mesh created between R3 and I1.

So if the above are correct then according to the basic network topology theorem:
$$b=l+n-1 <=> 5 = 2 + 3 - 1 <=> 5 = 4 $$
which obviously isn't correct. Where am I making a mistake ?

simulate this circuit – Schematic created using CircuitLab


texts:
I have 70Vrms sine wave, I rectified it with full wave rectifier. So  the output is  100Vp.I will divide it down to 1V using voltage divider (0-100V to 0-1V).
How could I add a 1.4V DC bias to the output of the voltage divided ?

Briefly:
$$ 70V_\text{rms} \Longrightarrow  0-100V_\text{p} \Longrightarrow 0-1V \Longrightarrow 1.4-2.4V$$

I have a 5V DC I could used it in the biasing

Spehro Pefhany, it is hard to find exactly this resistors values:

I read in another answer (Note also that this circuit does not isolate V1 and V2 from each other as a summing inverting amplifier would. Each sees the other with a impedance of R1+R2. Maybe that doesn't matter, but you need to at least think about it.(

Will this circuit work?

Mr. Spehro Pefhany,
I had a lot of distortion in my signal after I did the voltage divider as us advise my to do it.

Here is my project

When the voltage is 56Vrms, I get the following results ( the green is the signal at PWM pin1 and the yellow is at R6 -the AM demodulator- )

The voltage at pin 1 of the PWM IC (UC3526AN) have to be 1.4VDC bias with 1Vpp  when te input voltage is 100Vpp but it is not.
The following is the real measurements at pin 1.

At about 20Vrms input

At about 30Vrms input

At about 68Vrms input

At about 100Vrms input


texts: How would superconducting circuits save a lot of power in a small electric car?

texts:
From the bottom of the New Scientist article called , 'The superconductor breakthrough that could mean an energy revolution.':
Something like 10 per cent of electrical power is lost in long-distance, high-voltage cables, so making them out of superconductors would be an immediate big win.
But then, a few sentences later...
In applications such as motors and generators, they would offer a significant improvement in the power-to-weight ratio, boosting the efficiency of electric vehicles, for example.
Read more: https://www.newscientist.com/article/mg24933170-900-the-superconductor-breakthrough-that-could-mean-an-energy-revolution/#ixzz6kDwgGq8O
If even long-distance power cables only lose about ten percent, how would the much-shorter wires inside a car save so much power?
Apologies in advance if this is a stupid question.....


texts: What happens If the interrupt occurs during the execution of HALT instruction?

texts:
Consider the following program segment on a hypothetical processor .

I have this question in my course CS201.
Suppose this processor has 32 bits Load/Store operations, ALU operations is 16 bits and Branch instruction is 16 bits. Program has been loaded in the memory with a starting address of 3000 (which is in decimal) .

Assuming Byte addressing, If the interrupt occurred during the execution of halt instruction, then the return address pushed onto the stack will be ?

My Try :

I referred this link

http://x86.renejeschke.de/html/file_module_x86_id_134.html

According to this link, The return address saved on the stack must be of instruction after the HALT instruction, which gives me the saved address as

3000 + 4 + 2 + 2 + 2 + 4 + 2 + 2 = 3018

Hence, Stack saves 3018 .

But, I don't have the answer with me, so I can't confirm it.

Am I going Right ?


texts: What criteria do I need to look for when selecting a power MOSFET. It will be controlled by an Arduino board so it has to be "logic level". In my application I have to control a 12-15VDC resistive load at no more than 20A (a bunch of high powered LEDs). Ideally, I would like to get away without a heat sink but I am not sure if this is realistic. Any suggestions are appreciated.


texts:
I have seen two differente digital PID controller so far and I don't know which one should be prefered to control the speed of a dc motor.

1.) out=out_last + Kp err + Ki sum_err + Kd (err-err_last)

2.) out=Kperr + Kisum_err + Kd*(err-err_last)

The first one seems to be very slow for a variing reference signal, but achieves a good velocity control. The second one i cannot stabilize.

Which one should normally be prefered in the implementation of a speed controller on a uC?

Edit: I found a new approach for velocity control from here: https://www.controleng.com/single-article/the-velocity-of-pid/0733c0b7bfa474fb659b259808ddc869.html

Can I implement this on a uC in the form:
$$
out_n=K_p*e_n + K_v*(e_n - e_{n-1}) + K_a*((e_n-e_{n-1})-(e_{n-1}-e_{n-2}))
$$

Where in the last term the $$e_{n-1}$$ cancels. Or how should I implement the second derivative on a uC?


texts:
I try to create a GND pin and a VCC pin to connect them to a battery. On my eagle pcb I haven't found them. They should be like 5mm x 5mm.

On the schematic I added a ground and vcc pin, but I can't found them on the pcb.

I need a place (copper) to solder the battery connectors.

Is there a good way to do this easily?


texts: Finding the output of a node with two diodes (kind of full-wave rectifier)

texts:
Maybe this question sound stupid, but I really suck at electronics.

I have this circuit here:

simulate this circuit – Schematic created using CircuitLab

and i want to find the values of U1 when u0 is:

u0 = +15 V
u0 = -10 V
u0 = +3 V
u0 = 0 V

Diode tension threshold is 0.6 V.

This is my first post here, so if i messed up with anything please let me know.

EDIT: i fixed D2


texts: Boost Voltage before Regulating or vice versa

texts:
I have an input voltage from a 3S battery from 7.4V to 11.1V and I need to regulate / boost it to 5V and 12V. So what is more efficient or what is used in industry

Regulate the voltage to 5V with e.g. a LM7805 and then boost it from 5V to 12V with an LM2731
Boost the voltage to 12V with the LM2731 and then regulate it to 5V with a LM7805


texts: is it possible to install some device which will measure in real time the torque my diesel engine is providing at the moment?

texts:
It is easy to make a meter which will show the engine RPM, many cars have one installed. But to know the power in kW that the engine is providing right now, I also need to know the torque, because:

\$power = RPM * torque/9548.8\$

Besides RPM all in metric units (kW, Nm). BTW, does anyone know how the 9548.8 number is derived?

But back to my main question: is it possible to install some measuring device which will measure and show in real time the torque my diesel engine is providing at the moment? I want to know how many kW is used to move the car in real-time. I want to do something like this with Arduino.