texts: PID controller quickly drops command signal and quickly rises it when initially given control?

texts:
I have tried my hand at writing a PID controller to control a the output power of a laser in response to the measured temperature of some thing. The measurement of the temperature can be very noisy at certain temperature ranges, though the picture below was taken in a less noisy range.

Here is a current view of the PID in action

My current issue is not the oscillation in the command signal to the laser, I have since found some descent parameters that smooth it out nicely. My real issue is the initial drop off to the lower limit of the command signal range then the rise back to appropriate levels.

Some more background. The PID itself works by first using a lookup table to command the laser signal to a "close" value of what it should be to get the initial temperature close for the PID, it does this for X amount of seconds (20-30 has worked well to get it to a stable temperature).

The idea behind this was to hopefully fix the issue we were (are) having of the PID initially wildly oscillation between the minimum and maximum output signal. This is highly undesired and can hurt the thing being heated.

So once the lookup table value command time has expired the PID is then given control, in the image above you can see pretty clearly when this is (the initial sharp drop). Then it relatively quickly rises back to an appropriate signal.

What I think is happening is that the previous error and previous integral terms have not yet accumulated proper values (they start at 0) for the PID to produce the proper command signal at the desired set point.

Is the way to fix this to initialize the previous error and previous integral to values close to what they are when the PID is stable near the end of the graph?


texts: choosing surface mount resistor/capacitors

texts:
So I need design a prototype PCB circuit and need to decide on using what kind of surface mount resistors and capacitors to use. But looking at digikey, there are so many types with many variations in size, manufacturers, etc.!

Since there is not really any strict requirements for my project, I'm assuming most of them would work fine. Cost and precision is not a huge issue for my case.

But what are some deciding factor on choosing which size/packaging/manufacturers to use?


texts:
Ok, I have no idea if this is the best place to ask for this kind of question but I've been scattering the internet for a while to find any info regarding this:

Can we sell DIY electronics online? I'm from Canada.

Let's first define "DIY electronics":

Power supply is bought so has all the needed regulation. We are not
going into power supply design. DIY means to me, not having to go
through a 10k$ certification process only for AC/DC conversions. A
decent market supplied power supply seems safe.
A PCB with a microcontroller/processor with all low DC voltage and signals
3D printed cases and accessories.
If there is RF signals, it all comes from already approved modules bought on the market. (Because I know there is some more regulations
regarding RF designs approval).
A nice box for shipping.

Would there be any regulations/problems/anything I should be aware of or that I may be missing?

Please share any experience or relevant links on the subject.


texts: Infinite current draw for BLDC/Synchronous AC motor

texts: I have recently created a motor that runs off of outlet power, single phase 120 V AC. My stator is taken from a universal motor from a vacuum cleaner and has two windings on either side, wired to form opposite polarities at every cycle of the AC sine wave. My rotor sits inside the stator and is made of a LEGO body with 4 neodymium magnets arranged in a N, N, S, S configuration each 90 degrees apart from each other. This allows the rotor to rotate either clockwise and counterclockwise depending on the orientation of the permanent magnets and the initial position of the sine wave when it is plugged in. When I plug it into a surge protector, I can only run the motor for around 1-2 seconds at no load before the breaker switch pops. It is worth mentioning that the universal motor from which I took the stator from originally had a brush DC type rotor inside complete with a commutator, brushes, and its own set of 16 windings. Current was being used by both the stator and rotor, but when I replaced the original rotor with my permanent magnet design all the current was being directed only to the stator, which I feel like is what is causing the massive current spike as the current is not being used by multiple components anymore. In the vacuum cleaner I'm pretty sure the current was used by different components such as valves before it got sent to the motor. Is there a way I can design a circuit to limit the current draw from the surge protector? Perhaps I can create a transformer to drop the current, or create a soft start but I do not know how. Maybe I can wire lightbulbs in parallel to act as resistors and drop the current before it gets sent to the motor. My theory is that by adding more resistive components the motor can only receive a limited amount of current and cannot "pull" more current from the power source because of the resistors in the way. However the more components I add the more current is needed for them to operate, so the effect might cancel out. What is the most efficient way?


texts: I messed up the tip on my soldering iron. Is there any saving it?

texts:
I accidentally left my soldering iron, an XYTronic 258, on all night last night, set to a pretty high temp setting. Today I found that the tip was all oxidized and pitted looking. I tried cleaning it, I tried re-tinning it, but to no avail. Then I tried sanding and finally filing the tip. I got down to clean metal, but solder won't stick to it any more.

Did I ruin the tip? This is for hobby use, and I don't know of any places locally that sell tips for this iron. I'd really rather not wait a week for a replacement tip.

I read on other threads here that the tip is iron coated in Copper. Is that correct?

Is there anything I can do to rejuvenate the tip, short of getting some copper sulfate and electroplating a copper coating on it? Or is even that hopeless? I have stuff I'd like to solder this evening, but the heat transfer stinks now.

I have a fixed temp Radio Shack soldering iron that this one replaced (along with a fresh tip for that one) but my memory is that it is dreadful. The tips are not interchangeable between them, either.

It looks like my iron is variable power rather than thermostatic. It sounds like what I really need is a thermostatically controlled iron. Is there a moderately priced iron my readers can recommend? (I've been doing a lot of electronics lately, using it several times a week, and do end up doing electrical/electronic soldering a few times a month even when I'm not in the middle of an electronics project.) And what should I expect to spend on a decent iron for electronics and general electrical soldering?


texts:
I'm tryinig to implementan IIR filter like:

y(n) = 2*y(n-1)-y(n-2)+x(n)-2*x(n-6)+x(n-12);

My vhdl code is:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_SIGNED.ALL;
use IEEE.NUMERIC_STD.ALL;

entity ECGfilter is
    Port (
        reset: in std_logic;
        clk: in std_logic;
        filter_in : in std_logic_vector (0 to 15);
        filter_out: out std_logic_vector (0 to 23)
    );
end ECGfilter;

architecture FPB of ECGfilter is
    constant size_x : integer := 15;
    constant size_y : integer := 23;
    constant size_bank : integer := 12;
    type input_bank is array (0 to size_bank) of std_logic_vector(0 to size_x);
    type output_bank is array (0 to size_bank) of std_logic_vector(0 to size_y);

    signal x_bancoFPB : input_bank := (others=> (others=>'0'));
    signal y_bancoFPB : output_bank := (others=> (others=>'0'));

begin
    process(reset, clk)
    variable res_aux : std_logic_vector(0 to size_y) := (others =>'0');

    begin

        --Si el reset se pulsa (asíncrono)
        if (reset = '1') then
            x_bancoFPB <= (others=> (others=>'0'));
            y_bancoFPB <= (others=> (others=>'0'));
        elsif (clk'event and clk = '1') then
        --Funcionamiento síncrono.
        --Se actualiza información en los bancos de memoria
            for i in 0 to (size_bank-1) loop
                x_bancoFPB(i) <= x_bancoFPB(i+1);
                y_bancoFPB(i) <= y_bancoFPB(i+1);
            end loop;

            x_bancoFPB(size_bank) <= filter_in;

        --Se realiza la aritmética entre posiciones del banco de memoria
          res_aux := (2 *y_bancoFPB(size_bank-1))  -
                                      (y_bancoFPB(size_bank-2)) +
                                      (x_bancoFPB(size_bank))   -
                                 (2* (x_bancoFPB(size_bank-6))) +
                                      (x_bancoFPB(size_bank-12));

            y_bancoFPB(size_bank) <= res_aux;
            filter_out <= res_aux;

        end if;
    end process;

end FPB;

When I try to obtain res_aux, I get the following error (Vivado simulator):

ERROR: [VRFC 10-724] found '0' definitions of operator "*",
cannot determine exact overloaded matching definition for "*"

It's caused by the 2* multiplication. I know that I have the option of shift 1 bit to obtain the same result. However, I want to know why is this error.

Thanks!


texts: 17" screen panel and 2 channel 8 bit 40 pins LVDS connector on motherboard

texts:
I was looking for 17" screen panel for my motherboard. And after tones of datasheets I couldn't find any that may fit my 2ch 8bit 40pin LVDS connector. Most panels have 2ch 6bit 30/40pin or I found some 2ch 8bit but only 30pin. And can't really figure out how to connect my LVDS output to any of them panels as if I try to do it with 2ch 6bit panel then 2 pairs od Odd/Even will be missing connection from my motherboard and when I try to do it with 2ch 8bit 30pin panel then there is no input for EEID data and Colck. Is there any way to connect it, like cross cabels or just miss few pins? Are EEID data and Clock obligatory?

I attach images of LVDS input/output pin description from my motherboard and 2 panels.

images


texts: Programming the MK20DX256VLH7 with Arduino IDE

texts:
I want to start using the MK20DX256VLH7 in my projects. This is going to be my first 32bit microcontroller. I love the simplicity of the Arduino IDE and I would like to keep using it with this microcontroller.

I found the Teensy 3.1 board that already use this micro and it is possible to program the board using the Arduino IDE, BUT, it use a non open source bootloader inside a mini54tan microcontroller (schematics).

I understand that the author does not want the board to be cloned, but that is not my goal. When I use my 8bits microcontroller, the atmega328p, I have it on my breadboard using just the minimal components and an arduino board programmed as ISP programmer. In this way I can still use the Arduino IDE and program the 328 with no bootloader on so I can use the complete memory of the microcontroller.

I want to do the same with the MK20DX256VLH7 (I know is SMD, im going to build an adapter). Can I use the same principal? Is the arduino board programmed as programmer capable of writing code to this microcontroller, do I have to make huge changes to the Arduino IDE in order to make this work, or I can just use the Teensy arduino mod?


texts:
I have a MOSFET IRF Z44n and want to control 5V using 3.3V at the gate:

If I replace L1 with a voltmeter, the circuit behaves as expected: if SW1 is closed, I measure 5V. If SW1 is open, I measure 0V. I also can connect a lamp in place of L1, and it switches on when SW1 is closed (the lamp pulls less than 10mA).

Now the problem: if I close SW1 and connect the coil L1 that pulls normally about 500mA, I measure 0V in parallel to L1 with a total current of <10mA. Normally, the coil should pull its 500mA and generate a significant magnetic field (which it doesn't). As described above, connecting a lamp works.

Is the problem that the coil is pulling to much current? It isn't above the max current described in the data sheet.
I really don't know what to do.

simulate this circuit – Schematic created using CircuitLab


texts: I'm designing a preaplifier for a geophone. The amplifier uses OPAMPs which require +/-15V power supply for optimal operation. How can I generate such voltage rails without inserting excesive noise into circuit? Power supply should be as quiet as possible, with 9V unregulated input. The signals from the microphone are very weak.


texts: Fine delay tuning using phase interpolation

texts:
In the schematic of fine delay, each unit should produce 3ps delay, so the fine delay block is constructed using parallel combination of 8 inverters... Like that parallel combination of inverters we have 2 structures. To one structure we applied the signal which is to be fine delayed. To another structure we applied the signal which is delayed by 24ps.
So here in this structure how is fine delaying happening and how is phase interpolation happening?


texts:
I've calculated everything up and came up with the following.

Vin,max – 4.2v , Vfb = 0.1v , 1.8 <= Vf <= 2.4V, Vout – Vf + Vfb

fsw = 1.5MHz, 30mA <= I_led <= 250mA,     I_led = Vfb / Rs

I set I_led to be 160mA and I_ripple is 40% of I_led ( 64mA).
So, I got 10uH inductor. I guess I could get smaller inducter if I set I_led to be higher like 200mA or 250mA. Then, what would be the consideration. power dissipation?


texts: Determine a resistor's value in a circuit with an N-type MOS-FET transistor

texts:
In a circuit involving an N-type MOS-FET I am to determine the value of resistor \$R_2\$

Now in order to solve this I need to know what  \$V_{DD}\$ represents, is that the voltage relative to node D in the circuit or the lowest part of the circuit? What does this subindex stand for? I guess it can be safely assumed that \$V_S\$ is not zero, since it isn't grounded on the diagram.

The condensator C is so big that it acts as a short circuit for AC signals (as I understand it C can be ignored for solving this).

\$v_D\$ = \$V_{DQ}\$ = 8.0 V in this situation.

We are to show that \$R_2\$ = 20.6 kohms. Now I'm at a loss, because of the confusion regarding the voltages and how this circuit works. Suggestions are highly appreciated!

Threshold voltage is right under 2.40 volts.


texts: Why is the true power so low when adding inductors to the circuit?

texts:
For an electronics class, we used a vacuum pump that works with inductors and measured the current in the system. This creates a phase shift, where the current lags the voltage, as is expected.

We also had a heater, to serve as a pure resistor that wouldn't burn out from having 240 \$V_{AC}\$ applied to it.

The goal for this part was to measure the apparent power and true power of the circuit.

However, the true power with the vacuum pump+heater combo is much lower than the power with just the heater. From what I understand (mind, the concept of apparent/true/reactive power is new to me), this shouldn't happen.

This is the equation I'm using to calculate the phase shift in degrees: \$ \phi = 360\cdot{d \over T} \$

Where d is the phase shift in seconds and T is the period of the waves. The true power should therefore be \$P = |S|\cdot cos(\phi) \$, with \$ |S| = I_{RMS}\cdot V_{RMS} \$.

Say that with just the heater, \$ P = |S| = 700 \$, for example. With the pump and the heater, however, \$ P = 300 \$. Shouldn't the result be slightly higher than 700, given that the inductors in the pump are literally being taken out of the equation?

TL;DR: True power with a device that causes a phase shift is lower than without the device. Is it supposed to be this way?


texts: Does the position of the Ferrite bead matter?

texts: Often I will see a ferrite bead a couple of inches from one end of a cable. Does the position of a ferrite bead really matter?


texts: In a shimano dynamo hub with 6V regulator rest of power is being wasted?

texts:
I bought a Shimano hub dynamo that gives a maximum of 6 V with a regulator that they have provided. From what others here have said the regulator is a Zener diode.

But the output voltage of the dynamo increases with speed at which the bicycle is driven and 6V is only at around 10 km/h. So by using the regulator is all the energy being generated when I ride at greater than 10 km/h being burnt in the regulator. Isn't this a very wasteful way of dealing with the higher voltage.

Is there a more efficient way to deal with this, thanks a lot.

PS. I've added a picture of the regulator that was with the dynamo. If this is not used, voltage rises linearly with speed. When it is used the voltage only rose till 8-9V


texts: Reversing a .5-4.5V analog sensor output to 5V-0V

texts:
I have a pulse width modulation (PWM) control board that uses a 0-5V input via a potentiometer to control a DC motor speed. As I understand how this works, the potentiometer goes from 0% PWM at 0V to 100% PWM at 5V. I want to use a pressure sensor that outputs .5VDC at 0 PSI to 4.5VDC at 100 PSI to control the DC motor. Specifically, the controller will need to be at 100% PWM when the pressure is 0, and 0% PWM (off) when the pressure is at 43 PSI or 2.2VDC.

I found a somewhat similar question here,
How do I invert the output of this current sensor using the other side of the LM358?
but the answer was not clear to me.


texts: How to isolate a RLC circuit with MOSFET switches?

texts:
I'd like to isolate, with high-side and low-side switches, a RLC circuit after the inductor has been energized with a current of 2-3A from a 12V source (see sketch).

When the RLC circuit is isolated quickly, the AC voltage in the RLC circuit will go to 200V due to the back-emf of the inductor (400uH). The sense resistor is small (22 mOhm).

Because I'd like low resistance in the switch and because of the fast switching speed required (<100ns) my thought was a back-to-back mosfet switch. Can anyone recommend how the high-side and low-side mosfet switches should look like to effectively isolate the AC circuit from the DC supply, and how to best drive them from 3.3V logic? Any advice would be much appreciated.

For Andy aka: I include the spice simulation of a (not working) single mosfet circuit as you suggested. {B} is 400uH.

Voltages at gate (blue) and drain (green) of mosfet.

and zoom-in

and just to show that's not the capacitor (or anything else) that causes the problem, here's the same trace when the IRF740 is replaced by a voltage controlled switch (which is of course not practical).


texts: How would the pole and zero frequency expression look like for this transfer function I derived?

texts:
This is a practice problem in deriving the transition frequency function for mos and part of the set of questions is to determine the pole and zero frequency expression but this transfer function i derived is kinda different from what i'm used to from  the previous lectures. I usually see this form:

But my derived transfer function looks a little different.

Could somebody guide me how to derive them?


texts:
I am in a middle of getting the required components for my project. I will be using ESP32 microcontroller and SIM7600SA module for 4g/lte.. Since, I am a beginner in this field, can someone suggest if it is possible to connect sim7600sa to esp32. If yes, How can this be done?
Secondly, I cant find sim7600sa module online, all I can find is a chip - if I buy the chip, how can I hook it up with a sim jack and connect it to the controller?
I know the question is quite basic but want to be sure if this can be done or not.
Thanks,


texts: PCB Layout - Ground Plane Clearance Around and Under Ceramic Resonator

texts:
We are using Murata's 4MHz Ceramic Resonator (CSTCR4M00G53-R0) in one of our designs and request help in PCB layout design around Ceramic Resonator. The below Murata's FAQs page suggests not to place any GND plane under the Ceramic Resonator. Picture in page is attached below.

https://www.murata.com/en-us/support/faqs/products/timingdevice/ceralock/cct/cc0010

We are using a 4 layer PCB with continuous GND plane in Layers 1,2 & 4 and continuous power plane in Layer 3.

Kindly help us with the questions below:

Should we provide copper clearance area under the Ceramic Resonator in the inner layers also i.e. layers 2, 3 & 4? Or is it sufficient if we just clear the GND plane in Top Layer?
Is it recommended to place GND stitching vias around the Resonator (green dots as shown in below image) or should we completely avoid any vias around the Resonator?

Thanks.


texts: Using CMOS to detect transmittance in sample from LEDs

texts:
I am trying to get the transmittance through various liquid samples using specific wavelength LEDs.  Originally I was experimenting with photodiodes, but do not seem to be ideal.

The target color range is near UV / Violet and Blue (~400-550nm).  I am attempting to source a CMOS image chip that I can experiment with and am not sure as to which requirements I am looking at.

The basic requirements would be: Drivable with an atmel (Xmega, Atmega, etc).  I think ARMs are more standard, or FPGAs but in terms of cost and programming complexity, would prefer to stay within microproc. territory.

Essentially I intend to sample the light from the LEDs with the intent of processing with an FFT algorithm in order to detect frequency components.  A standard supported protocol like i2c or similar would be nice.  Working with an AVR dragon.

Essentially help to find out what the important criteria in CMOS selection are.


texts: Does a robotic lawn mower sense that it is outside the perimeter wire? If so, how?

texts:
I have a robotic lawn mower. Sometimes if the grass is really slippery, the lawn mower can slide outside of the perimeter wire. When that happens, the lawn mower shuts down and I get a notification on my phone. The notification says that the mower is outside of its wire.

Does the lawn mower really have sensors that can distinguish whether the movwer is inside or outside the perimeter? Or does it only assume that it is outside, since it has crossed the perimeter wire once (and only once)?
How does the lawn mower know that it is outside of the perimeter wire?


texts:
I am trying to write the data into the NOR flash but for some reason it is taking some random/garbage data .
First i tried to erase the sector
then i read the data from the same location which i have erased so i get some garbage data so it seems that it does not erase the data .below is the code called from main

uint8_t datatemp[128];

 W25QXX_erase_Sector(0);
 W25QXX_Read(datatemp,0 , 128);

void W25QXX_erase_Sector(uint32_t Dst_Addr)
{
    // Monitor flash erase, test
    printf("fe:%lx\r\n",Dst_Addr);
    Dst_Addr = Dst_Addr * 4096;
    W25QXX_Write_Enable(); //SET WEL
    W25QXX_Wait_Busy();
    HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_RESET); //Enable device
    SPI1_ReadWriteByte(W25q64_SectorErase); //Send sector erase instruction
    SPI1_ReadWriteByte((uint8_t)((Dst_Addr)>>16)); //Send 24bit address
    SPI1_ReadWriteByte((uint8_t)((Dst_Addr)>>8));
    SPI1_ReadWriteByte((uint8_t)Dst_Addr);
    HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_SET); //Cancel the chip selection
    W25QXX_Wait_Busy(); //Wait for erasure completion
}

void W25QXX_Read(uint8_t* pBuffer, uint32_t ReadAddr, uint16_t NumByteToRead)
{
    uint16_t i;

    HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_RESET); //Enable device
    SPI1_ReadWriteByte(W25q64_ReadData); //Send read command
    SPI1_ReadWriteByte((uint8_t)((ReadAddr)>>16)); //Send 24bit address A23-A16
    SPI1_ReadWriteByte((uint8_t)((ReadAddr)>>8)); //A15-A8
    SPI1_ReadWriteByte((uint8_t)ReadAddr); // A7-A0
    for(i = 0; i < NumByteToRead; i++)
    {
        pBuffer[i]=SPI1_ReadWriteByte(0xff); //cyclic reading- 0XFF
    }
    HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_SET); //Cancel the chip selection
}


texts: A basic question about the meaning of dB of an antenna radiation pattern

texts:
I know that dB is always a power ratio. And to obtain dB there must be a reference power or voltage measured with respect to another.

Below is an antenna pattern which shows a -3dB point for instance:

What does that mean literally? Can it be explained clearly? -3dB obtained by dividing which units? And what is relative to what? Basically I'm asking the idea of antenna pattern and the dB associations. And how is that obtained.

Edit:

Edit 2:

I marked two points A and B in X, Y, Z coordinates. A is on the plot surface B is not. Red and pink share the same XY point and different Z. Are the powers at A and B same? If not is the power pattern only valid for that plotted surface? How about the rest of the sapce?


texts: Multiplex two displays or use a higher pin count uC?

texts:
I am currently learning to program a NXP LPC1347 for a project which will utilize two SSD1963 controller-based displays. The issue is that the uC only has 51 IO pins whereas the total pins of the display would amount to 26. This leaves too few pins for the peripherals that I need to have on the board (switches, UART, SPI, I2C)

I was initially going to upgrade to a LPC17xx but I figured I could also multiplex the 8-bit data and could save quite a few pins. Perhaps I could even multiplex the 5 control signals as well. Is this a better solution than using a more complex and more expensive part like a LPC17xx or are there pitfalls that I'm not considering?


texts: What is the advantage of a Z transform derived PID implemenation?

texts:
I've seen many PID articles, such as this, use a Z transform of the generic PID equation to derive some crazy difference equation which can then be implemented in software (or in this case an FPGA).  My question is, what is the advantage to such an implementation versus the traditional and much more intuitive, PID without a PhD type implementation?  The second seems easier to understand and implement.  The P term is straight multiplication, the integral uses a running sum and the derivative is estimated by subtracting the previous sample from the current sample.  If you need to add a feature such as Integral Windup protection, it is straight forward algebra.  Trying to add Integral Windup protection or other features to a difference type algorithm, such as linked above, seems like it would be much more complicated.  Is there any reason to use such an implementation, other than the "I'm a bad ass who likes to do Z transforms for fun" type bragging rights that go along with it?

EDIT: The PID without a PHD article I linked is an example of the simpler implementation that uses a running sum for the integral term and the difference between consecutive samples for the derivative term.  It can be implemented with fixed point math in a deterministic manner and can include real time time constant information in the calculation, if desired.  I'm basically looking for a practical advantage to the Z transform method.  I can't see how it could be faster, or use less resources.  Instead of keeping a running sum of the integral, the Z method appears to use the previous output and subtract the previous P and D components (to arrive at the integral sum by calculation).  So, unless someone can point to something I'm missing, I will accept AngryEE's comment that they are essentially the same.

FINAL EDIT:
Thanks for the responses.  I think I've learned a bit about each but in the end, think Angry is correct in that it is just a matter of preference.  The two forms:

$$ u(k) = u(k-1) + K_p(e(k) - e(k-1) + K_i T_i e(k) + \frac{K_d}{T_i}(e(k)-2e(k-1)+e(k-2)) $$
$$ e(k-2) = e(k-1), \quad e(k-1) = e(k) $$
$$ u(k-1) = u(k) $$

or

$$ \mbox{sum} = \mbox{sum} + e(k) $$
$$ u(k) = K_p e(k) + K_i T_i\cdot \mbox{sum} + \frac{K_d}{T_i}(e(k)-e(k-1)) $$
$$ e(k-1) = e(k) $$

will evaluate to essentially the same thing.  Some mention the first can be implemented in a DSP or FPGA faster, but I don't buy that.  Either could be vectorized.  The first requires two post operations, the second requires one pre and one post operation, so it appears to even out.  The first also requires 1 more multiplication in the actual calculation.


texts:
When I was debugging my microcontroller-based boost SMPS I accidentally got 85V (instead of 15V as I intended) across the 1kΩ test load resistor. Does this spell a hazard for the one debugging the circuit?

The SMPS is powered from a 9V wall wart capable of 1A max, and the microcontroller is powered with AMS1117 drawing power from the 9V rail.


texts: What space applications use the 555 timer?

texts: The 555 timer is considered the most famous integrated circuit of all time and is also credited with a versatile use in space travel. Hans R. Camenzind (the designer of the 555 timer) said that this IC is used for spacecrafts. However, I can't find more on this. Therefore the question, what is the 555 timer used for in space travel?


texts: Powering 800mA router for approximately 1 min

texts:
I need a cheap way of powering my internet modem (rated at 0.8A, 12V) for approximately 1 minute in case of power failure (which happens every hour or two) till my secondary power takes over.

I am thinking capacitors but i am not sure if they will be able to power for 1 minute.

Edit: If i connect a 12 v battery in parallel and update the power adopter to 14V to charge the battery, would this kind of setup damage my modem?


texts: understanding oscillation in op amp circuit

texts:
I understand what causes oscillation in a negative feedback op amp circuit- when an op amp circuit is not stabilized to have its AB<1 at the frequency whose phase shift is 180, then the negative feedback will turn positive.

I attached the circuit I am working with (not gonna lie, its for school). The point is to mimic a whole op amp system (the amplification is now much bigger hence, is now in danger of instability) and being able to add poles and zeroes to stabilize

Here is what I don't understand-When I input a small sin wave signal at R1,and at the output, I saw the signal magnified by 1/B. Magnifying the signal, I saw, riding on my sin wave, another very small sin wave- these are my oscillations from noise.

Why don't these oscillations take over the signal? If they are created from positive feedback, shouldn't they keep growing? Does it have to do with slew rate?

Thanks


texts: Controlling hundreds of motors using an arduino uno

texts:
I'm trying to build a haptic feedback suit, which requires me to control over about 576 vibration motors (24x24), using an arduino uno. I have no idea how to do this because the uno has only 13 gpio pins... Does anybody have suggestions as to how to go about this?
EDIT:
I don't think that the arduino UNO is capable of handling this task..
I'd appreciate it if you could suggest another microcontroller to use.
And also, if i can use a raspberry pi.
EDIT2: I need 524 Analog outputs


texts:
I am currently an EE/Physics undergrad doing scanning tunneling microscopy research at my local university. For future experiments, it would be helpful to employ a higher gain preamp than we currently have, and given that other groups have built them, I was looking into doing the same.

We're hoping to measure current signals from about 0.05-10pA from DC to a few kHz (though more bandwidth with a low noise floor is certainly welcome), requiring a transimpedance gain on the order of 0.1-1 teraohm. This certainly seems possible as it was done at the University of Florence (circuit below), as well as in a number of other papers. A few other topologies are presented here.

simulate this circuit – Schematic created using CircuitLab

I was able to perform a noise analysis of the circuit in LTspice, but I'm a little uncertain of how to translate the spectrum of uV/rtHz vs frequency into a average value for noise floor as it seems to blow up at low frequency with 1/f noise.

Additionally, the LTC6268 seems to have a very low input bias and reasonable noise characteristics, so I was considering using it in place of the above for the first stage.


texts: Simpler ways to develop a buck regulator

texts:
I am designing a low profile space grade buck regulator. I have the following constraints

ICs must be space grade
Low component count
Small size

The converter specifications are as follows. Input voltage varying from 15-25V, Required outputs at 3.8V or 5.6V. I came across this converter design from an LM136 datasheet. Could someone explain the functioning of this circuit.
I can understand that there is the standard buck regulator configuration and a difference amplifier using the npn transistors. The switching functionality eludes me


texts: How to interpret the relationship between WGN and PSD in digital communication?

texts: We know that the white Gaussian noise (WGN) process is the delta function δ (t) at autocorrelation t = 0, so how should the power distribution (PSD) in the frequency axis be, explain from the relationship between autocorrelation PSD?


texts: How to solder something as tiny as this?

texts:
I have an LED strip that is a little over 1 cm wide with 5 connectors on it, each about 1 mm wide I estimate. The wires on the left are the ones that were originally on this strip. It's supposed to be possible to cut this strip so I'm not doing anything out of spec.

My problem is that anytime I solder a wire to one of the copper traces on the strip, and then try the next one, the heat de-solders the existing wire. I sometimes manage 2 or 3, but then I invariably loosen one after which I have to desolder and clean all of them.

So far I have tried after the 'usual' technique (putting wire on the spot, apply heat to wire, push tin on wire until it starts to flow):

Tinning wire, putting it on trace, apply heat
Solder a solder copper piece first (the stranded wire has a tendency to 'fan out' to nearby wires), using all of the fore-mentioned techniques
Drill a hole in the trace with a dremel, put tinned wired in there, apply heat to wire a bit away from the trace until tin starts to flow. Very hard to get hole right, plus once the tin starts flowing, it flows to the next trace.

I'm running out of ideas. I've tried the above with those tools with the two crocodile clamps to keep everything in place (not sure what they're called), and with magnifying glasses, and it's not just a matter of keeping steady or seeing everything correctly - it just seems that there is too much solder in too small an area (I've tried to keep it minimal, of course). Is this possible with only a soldering iron? Maybe there is a way to fab my own push-on connector so that I don't have to bother with soldering so close together anymore? I'm just a DIY amateur, I wouldn't know what sort of equipment this sort of thing is done with in a real lab (the connections that were pre-soldered look so near and precise).

Thanks.


texts: I am looking for a fast SPDT switch that is controllable using GPIB (IEEE-488). The maximum voltage applied across the switch would be something like 10V (and in practice more than around 5V). I'm quite new to electronics and am having trouble working out how various switches are controlled, and what to look for in switch specifications. Are there some general guidelines to identify a suitable switch for a particular application, and in particular what to look for in a switch controllable by GPIB?


texts: Can we give a PWM of amplitude more than the rated voltage to a motor but making sure that the averaged voltage is lower than that of the rated voltage of the motor.Is it safe for the motor?


texts: loops with C18 Compiler on mplabide for 18f4550

texts:
I am facing trouble with glowing multiple LED simultaneously on a 18f4550 micro-controller under the same " while(1) ". I am new programming. [C18 compiler with Mplab ide.]

I was able to alternate blink RB0 and RB1 led with a piece of code found on web by setting the RB pins to output and then making it high.

#include<pic18f4550>
// Chip config and setting for make RB pins output

void main(void) // Main block
   {

   While(1)
        {
          blink-RB-two-led-alternatively-forever(); // a function prototype for blinking RB0 and RB1 Alternatively.

         } // loop forever

   }

That works Fine without any problem.
I can do same with PortD pins as well., With no problems .

But I want RD0 and RD1 to blink alternatively , Simultaneously with RB0-RB1.

Means when I Power on the pic18f4550 I wish to get both RB0-RB1 and RD0-RD1 Flash alternatively and Simultaneously.

I tried this. But didn't work.

void main(void) // Main block
   {

   While(1)
        {
          blink-RB-two-led-alternatively-forever(); // a function prototype for blinking RB0 and RB1 Alternatively.

          blink2-RD-two-led-alternatively-forever(); // a function prototype for blinking RD0 and RD1 Alternatively.

         }

   }

The loop goes into " blink-RB-two-led-alternatively-forever(); " and keeps Flashing the RB0 and RB1 pins and it never gets to Second function Prototype.

If I change the Order Then RD0 -RD1 starts to flash alternatively But it never comes to PortB.

Please Suggest me a Solution.
How to make both the things to Work Simultaneously together.

Thanks a lot in advance.


texts: The 'gap' between understanding of transistors and their application in real circuits

texts:
How do they even work? I'm in senior high school year and have electronics as a subject. I'm really interested in getting to understand this and take up electronics in college too. But now this seems like a distant dream with my feeble understanding about 'how transistors work' and their 'actual applications in circuits'. I've read numerous guides online and after finishing them, I feel like I've learnt most of it but when I start studying about the TTL NOT gate (IC 7404) and a few others, (like 7402, 7400) which is part of my coursework, and which is based upon working of the transistors, I don't get anything! Sometimes the emitter is used as input, sometimes, it is used as output and I feel some of the sentences in the text (about the working of ICs) contradict what I learnt in other guides. I feel there's some gap remaining between, my understanding of transistors, and their applications in circuits, which is pissing me off and can't seem to see what it is.

Can anybody please point out some articles which would fill this gap and enlighten me?

Update: I'd like to learn about their working in application circuits. About the 'depth of understanding', I know what role electrons and holes play in working of transistor.


texts: Power Ratings of RF Attenuators In Series

texts:
If I connect RF attenuators in series, does the power rating of the attenuator closest to the antenna have to be high enough to handle the expected RF power on its own? Or does the placing attenuators in series limit the amount of power each attenuator must dissipate by spreading it out amongst attenuators?

For example, if my expected RF power is 2W, do I need to use a 2W attenuator nearest to the antenna even if there is going to be a 1W attenuator between it and the receiver? Or can I get away with a 1W for the attenuator nearest to the antenna?


texts:
This s a newbie question.

When receiving serial data from a microcontroller by a PC program I need the microcontroller to be nearby and it needs to be connected to a USB port and send the data via this USB port to the PC program.

But I want to send and test a PC program by a virtual port program which sends data to a specified port without a microcontroller is around. So one can test the received data by a PC program without an actual device sending data to the PC.

How is it done? Is there such emulator program electrical engineers use?

I know how to use hyperTerminal but it is used for sending or receiving data from a real device like a microcontroller.


texts: Single supply op-amp voltage follower - negative clipping with AC-coupled load

texts:
I am using a µC running DDS algorithm to synthesize certain waveforms (in fact I made 3 channel music generator with portamento&ampltude modulation effects, commands for changing waveforms etc. but that is not relevant to the question). The output from µC is 15686.27 Hz (8e6/510) PWM signal with variable duty-cycle. I am updating duty-cycle from a lookup table to generate the desired waveform at desired frequency and then the signal goes to the low-pass RC filter.

The output from RC filter has +2.5V DC offset and 2.5V amplitude (absolute peak values are 0 and +5 V). I've connected that signal to 50k trimmer acting as voltage divider to reduce the signal to +1.5V offset and 1.5V amplitude so I can use LM324 in voltage follower configuration to drive the load. I reduced the voltage because LM324 with 5V single supply can't go above about 3.7 V. This is the signal going to LM324:

The settings are: DC coupling, 1V/DIV, 2ms/DIV. Sine wave frequency is 329.6 Hz (tone E4).

Waveform at the output of the voltage follower (LM324 output shorted with the inverting input) of course looks exactly the same (with or without resistive load).

The problem occurs upon inserting the AC-coupling capacitor to remove the DC offset, this is the waveform at the output of the op amp with 100 Ohm load AC-coupled with 470 µF capacitor:

And here is the waveform after the capacitor:

The DC bias is now removed.

Now, I am aware why this clipping would occur with single transistor emitter follower (common collector configuration). Here is the detailed explanation whay clipping happens when using AC with single transistor voltage follower. The explanation is unfortunately too long to insert the text into the question but this is well known fact - the problem is transistor cannot sink current during the negative half of the waveform.

However, since LM324 can reach 0V using 5V single supply I thought there wouldn't be clipping but there is.

By increasing the load resistance the clipping decreases, here is the waveform with 10k load:

And even better result with 15k load:

However, I need undistorted signal with 100 - 200 Ohm load (4 Ohm speaker + resistor) and the question is if there is a way to get rid of the clipping without using a high input impedance amplifier.

I might put another op amp behind the capacitor to prevent clipping (because the input impedance would be very large) but then I'd have to use dual supply because of already removed DC bias. Is there a simple way to avoid the negative clipping in such configuration?

EDIT:
The schematic:

simulate this circuit – Schematic created using CircuitLab

UPDATE:
Output from TL084 in place of LM324:


texts: How can I use a NPN transistors to convert from 3.3v to VCC (3.9-3.0v)

texts:
I'm wanting to drive a NeoPixel from a CMOS device. The power for the neopixel is a 4v LiPo battery and will fall from around 3.9v to 3v before it cuts off. I have a few PN2222 NPN transistors, I'm not sure what kind of circuit I should be building out of them. The neopixel needs around 0.4us timing.

Edit

The CMOS device will have a step up/down regulator. It's output will be a steady 3.3v. I will be powering the neopixels from the battery directly (3.9-3v is in it's operating range). I need to ensure the signal the CMOS device is sending to the neopixels matches the neopixel's input voltage.

Thanks!


texts: What are the downsides of using a LM7805 with a 11.1v Li Ion Laptop battery to charge a USB device?

texts:
I want to use my thinkpad battery(11.1v) hooked up to a LM7805 to charge a USB Device.

What are the downsides to such a setup?


texts: How to make 1uA consumption on Attiny13a?

texts:
I'm measuring my standalone Attinty13a (internal 128kHz) current consumption with li-ion accumulator (3.7v, 220mAh). Here is my schema

and code:

#include <avr/interrupt.h>
#include <avr/sleep.h>

ISR(WDT_vect) {
   digitalWrite(4,HIGH);
   delay(1000);
   digitalWrite(4,LOW);
   delay(1000);
}

int main(void) {
    DDRB = 1<<DDB4;
    WDTCR |= (1<<WDP3);
    WDTCR |= (1<<WDTIE);
    sei();
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    for (;;) {
      sleep_mode();
   }
}

Everything works fine: when it sleeps ammeter shows 5uA, and when digital pin 4 comes "on" ammeter shows more than 40mA. Nothing is connected to the chip, all pins are empty outside. I wonder could i reduce "pin on" state to 1uA?

Update:

I succeed with current reduction by setting all ports as outputs by using this code.

#include <avr/interrupt.h>
#include <avr/sleep.h>

ISR(WDT_vect) {
    PORTB ^= 1<<PB4;
    PORTB ^= 0<<PB4;
}

int main(void) {
    for (byte i = 0; i <= 20; i++)
    {
        pinMode (i, OUTPUT);    // changed as per below
        digitalWrite (i, LOW);  //     ditto
    }
    WDTCR |= (1<<WDP3);
    WDTCR |= (1<<WDTIE);
    sei();
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    for (;;) {
        sleep_mode();
    }
}

I do not quite sure how everything works now, but I added a LED with 1M ohm to pin 4, and 150 ohm resistance to Reset pin <-> Vcc, and my ammeter on scheme now shows 5uA in sleep state, and ≈7uA when pin turns on.
ps:

●https://www.gammon.com.au/power not all function of this tutorial works with Attiny13a, probably because its for Atmega328

●http://brownsofa.org/blog/2011/01/10/the-compleat-attiny13-led-flasher-part-3-low-power-mode/ i used this tutorial to make my Attiny use power down mode.


texts:
I'm still stuck on this task:

And I'm trying to calculate Vth. I've calculated:

And the Vth equation is:

My problem now is that I want to convert from rectangular form to polar form for 100j/100 + 100j. I can't seem to get it right. I tried multiplying with the conjugate, however I just got (j). I want to convert it to polar form so that I can multiply the amplitudes and add the angles. However I'm stuck.

Could someone help?

Update: I solved the upper part. Now I need help with time-domain. Please look below:

I've got a hard time understanding how to calculate the time domain. I've found the Vth and Zth like so:

Note: Ignore the white markings, it was written in swedish, therefore I tried to hide it so it wouldn't led to confusion.

And this is how far I've gotten to be able to find the time domain:

I don't know how to find the angle and how to proceed with finding the time domain so that I can draw a schematic of it.

I would appreciate some help. Thanks!


texts: Operating two wireless cars simultaniously

texts:
This is my first "serious" electronic project, so I apologize if my question is silly.

I tried to follow this tutorial to construct a remotely controlled car.
Moreover, I wanted to make two cars. Each one operated by its remote control
(to make fun with both my boys). I thought that this is what address pins are standing for, so I connected differently the address pins (1-8) of each pair of ht12e-ht12d chips.

However, only one car can be operated at a time. If I turn on both transmiters, this causes a collision (I speculate) and nothing works.

Currently, both cars are operated by the radio trasmitter/reciever of the same frequency (433MHz).
From my search, I found that if I use 433Mhz for one car and 315Mhz for the other, no collision should occur. I'll use this solution if I do not find something better.

My question is why different pinout of address pins doesn't solve the problem. This is what these pins are for (or they are not?).


texts: What do you call a pair of SPDT switches controlled by one toggle?

texts:
I need a toggle switch which allows me to switch the poles of two separate single-pole-double-throw switches together. It would work like the diagram below. Note that the dotted line represents a physical connection not an electrical one.

I need to find one online (for UK shipping). What are they called?


texts:
I am a bit confused about this differential base-emitter resistance.

I has been said that r_pi doesn't have much influence on small signal input impedance, when CE with emitter degeneration is used. Well, I doubt this claim.

Can someone please explains why or when should r_pi be neglected in small signal input resistance calculus for CE with emitter degeneration?


texts:
I'm super new to electronics, but I wanted to clarify something just in case I was wrong:

Duty Cycle is the measurement of what the percentage is High and Low from when a signal starts from low and goes high, stays high until it goes back low and ends right before the signal is about to go high again.

Hertz is the number of duty cycles that occur every second, so if there was only one duty cycle in one second, it would only have 1 hertz, if there were 50 duty cycles in one second, there would be 50 hertz?


texts: Difference between medical device status: CE mark versus FDA approval

texts:
Can anyone tell me what the exact difference is between a medical device getting a CE mark versus FDA approval?

As far as I know, a CE mark only means that a medical device conforms to the European Standard of electronic engineering and that its use is considered reasonably safe.

However, it does not tell you anything about the functionality of the device, or does it? That is unlike an FDA approval in the USA where, as far as I understand, an important requirement is that it is deemed safe, but also has been proven to be functional and effective as well.

Am I correct to say that a CE mark for medical devices is about safety and FDA approval is about safety + effectiveness?

I'm having a hard time getting to the bottom of this. Many sites are quite intransparent. If possible, please mention your sources in the answer so I can read further on the topic.


texts:
I am looking for a way to search for a replacement LED.
Unfortunately I don't know the name of the package.

The LED has a kind of conical recess at its tip to diffuse the light sideways instead of axially.

I am missing the technical name for that specific tip. Therefore I have difficulties to search the manufacturer's websites for that specificity.

What is the official name of that kind of tip?


texts: How should I deal with KiCAD Electrical Rule Check warnings?

texts:
I have drawn up a modest size schematic in KiCAD, for the first time.
It seemed more or less straight forward. But now that I run the ERC error checker, I get boatloads of errors with seemingly disconnected pins even though the automatic junctions appears. The most frequent error being:
"Pin connected to other pin but not driven"

It's random where it comes and where it doesn't even in setups that were copy pasted. Sometimes I need to unplug things and put them back together one by one, sometimes it's the little power components and sometimes the passive ones and sometimes I just move out the entire chip and put it back in. It sometimes fixes those problems and sometimes I rip my hair out doing it over and over and it just won't go away. Here is one on pin 1 of U24, no matter what I do it comes back. Similar problems on pins 2, 3, and 4 although they don't appear in the error box near this one.
This is very annoying and it must be bugs in KiCAD that is showing components connected, even with junctions, but the underlying model is apparently randomly different from what's shown.
Or can I just ignore those errors? And is there a way to tell the checker to ignore particular errors -- I know one can suppress classes of errors and warnings, but I mean particular occurrences of them. For example the second error (warning) "Conflict problem between pins ..." tri-state signal pin connected to fixed GND or +5V, the warning is fine once, but once I checked and find it correct, I want to acknowledge the particular warning and make it not be raised again, I don't want to see it any more. Same thing with disconnected pins, disconnected outputs shouldn't be a problem, I want to tell the checker that it is fine in particular cases.


texts: Looking for formulas for figuring out R1,R9,R10. The transistors and regulator is what I have on-hand. Any help would be appreciated.


texts: JTAG Programmer using Zedboard - Signal Integrity problems?

texts:
I am trying to build my own JTAG programmer using the Zedboard but I am stuck with hardware issues.

For the Zedboard side, I am using the Pins XADC-GIO0, XADC-GIO1, XADC-GIO2 and XADC-GIO3 as TCK, TDI, TDO and TMS. I constrained these pins as LVCMOS25 as my target board's JTAG has a VREF of 2.5V. On my Zedboard, I used the jumper setting for the Vadj at 2.5V.

When programming the target board using the Zedboard, I simply connect the 4 JTAG pins using wires from the Zedboard to the target board and pull-up TDO using a resistor to the VREF of the target board. I do not have any buffer chips or series resistors termination or and decoupling capacitors to ground for the JTAG pins. I was thinking that TCK is 1MHz and not really that high-speed for signal integrity issues to set in?

When issuing the JTAG commands to the target board, I am however unable to read back the device ID correctly, somehow, the TDO output just isn't correct.

I checked the output from the Zedboard to the target board several times and I am certain that they are issuing the correct bits to the target board. I have also checked the setup and hold times of the TCK wrt TDI and there's nothing wrong there as well. The Zedboard and the target board are powered separately with their own power adaptors but I connected some of the ground pins on both boards together to have a common ground. (another noob mistake or is this normal?) The target board's FPGA is also a Xilinx FPGA.

If this is really a case of signal integrity issues, can anyone advise how I may solve this?

Thanks in advance.

Update 20171004 1:
Ok so I stumbled upon the problem but I got no idea how to fix it. Apparently the problem seems to lie with TCK. It is the same setup but I removed the pullup resistor from TDO. Now when I issue a read Device ID and probe TCK (not TDO!) using an oscilloscope, the Zedboard FPGA reports the correct Device ID. When I remove the oscilloscope probe, the Device ID is wrong again. This isn't intermittent; placing and removing the oscilloscope probe on/from the TCK pin respectively causes the TDO to be correctly and wrongly read. Any ideas how I should solve this?

The Zedboard FPGA pins are LVCMOS25 with Drive at 16ma.

Update 20171004 2:
Ok I added a pull-up resistor on TCK (no pull-up resistor on TDO) and the Device ID is read correctly everytime. Still haven't successfully configured the target FPGA but I guess at least the signal integrity part seems to be tamed a little for now.

Update 20171005:
Ok I finally found the problem. Turns out my TMS pin was assigned to XADC-GIO3 (Pin J15) and this pin was the issue. Every other pin H15, R15 (respectively TCK, TDI) has a Vpp of 2.5V while J15 only has ~1point-something volts. I turned this into an input pin by swapping with TDO (K15) and everything turned out fine! No need for twisted pairs or termination or pull-up resistors on any signal - TMS, TCK, TDI or TDO. I was also finally able to program the target board with my Zedboard JTAG programmer.


texts: Determining the resistor value to dissipate energy in inductive and capacitive components in the circuit

texts:
I am trying to model the following low-loss LC circuit, but I need to add a resistive load to dissipate the energy that accumulates in the inductive and capacitive components. I am not sure I fully understand this, so some feedback as to whether the following is correct would be much appreciated.

Basically I would add a resistor in parallel with C3 and C4. To calculate the value of the resistor, I first got the capacitive equivalent of C1, C2, C3 and C4 ie 1/c(eq) = 1/C1 + 1/C2 + 1/(C3+C4). The value was 57.49nF.

For the total inductance of the transformer, L1 + L2 + -2M, where M is sqrt(L1*L2). In the above the results are 0.00204 and -0.01996, but a negative value doesn't seem to make sense so I would discard it.

Then I calculated total impedance:
50Hz from the power supply is 314.16 rad/s (w)
So, Z(Total) is R + X(L) + X(C) = R + j(wL - 1/(wC)) = 100K + j(0.06408864 + 0.00001806105) = 100K + j0.0641067

So the current in the circuit is: I = V(s)/Z(total)
which is 240/(100K+j0.0641067) = 0.0024-0.00000000153j

I: jwL = j0.00001806105
C: j(1/wC) = 0.06408864

from V=IZ

V(inductive): 0.00000004334-2.76334*10^(-14)
V(capacitive): 0.00015381273 - 9.80556* 10^(-11)

Total V(Z) is: 0.00015386 - 9.808322*10^(-11)

Would you then insert a resistor to the value of 0.00015386/0.0024 = 0.0641083, with V and I real values taken from above?


texts: Safety/efficiency of a makeshift aluminium can heatsink?

texts:
I had recently received a 9v 1A DC wall-wart off eBay, and needed to open it to swap the polarity of the jack to center negative. As I had the case open, my finger bumped against the metal part of the TO-220 voltage regulator - on which there was no affixed heatsink -  and I noticed it was quite hot, I thought I'd been shocked.

I wasn't sure if the heat would be a problem with extended use; I knew it was a cheapo eBay buy, so I wouldn't expect proper heatsinking. But I was in an experimental mood, so I thought I might see if I could remedy the supposed problem.

I couldn't find any actual sinks in my parts, but as any good student would, I had plenty of aluminium beer cans in my recycling bin. I cut a rectangle from one and tested its conductivity, could not get anything on either side, and screwed it to the regulator.

It does not make any contact with any electrical pins or other parts, and even though the thermal contact is flaky, when plugged in, the side of the plastic case it is touching does get comfortably warm, so I assume it is doing at least something in the way of thermal conduction.

So, my questions. Should the 9 Volt regulator under full 1 Ampere load, have required a heatsink in the first place? If so, would I be making even the slightest difference with my bodge? And most importantly, is this a hazard in any way shape or form?


texts: For my projects I have always used hacky power supplies: wall plug + 7805, a USB port or an ATX PSU. I am looking at getting into 3.3 V circuits and I am having trouble getting hold of the necessary regulators in Australia. Can anyone recommend a good lab/bench-top power supply or alternatively a cheap way of getting 3.3 V?


texts: Is it possible to execute a left shift in a single clock pulse?

texts:
I am currently designing my own 16 bit CPU and want to have a logic left shift instruction. I can make it shift only 1 position easily, but I want it to shift it b positions. Is that possible in a single clock pulse (or a constant number of clock pulses).

Example (using 4 bits):

Input A: 0011

Input B: 0010

Desired output: 1100


texts: Application and bootloader written in different tools can not be compatible?

texts:
I have a bootloader to PIC18F4550 that was written using Mikro C for PIC and I have two firmware applications, one was written using Mikro C for PIC and the other using MPLAB X with XC8 compiler.

With the bootloader installed, I can upload the application written in  Mikro C without problem, but, with the same bootloader installed, when I try to upload the application written in MPLABX I can't. I load untill 100% but in the end it crashes . I thought that upload the applicatoin in hex it would not be a problem and would be independant of the tool used.

The version of the bootloader that I'm using is this that I found in this site:

http://microcontrolandos.blogspot.com/2013/09/pic-bootloader-usb.html

Some one has any idea of why it is happening ?

EDITED:

I don't know if it is at the top or at the bottom of memory. Based on the following code, I guess it is on the bottom:

const unsigned long BOOTLOADER_SIZE = 8000;//7432;
const unsigned long BOOTLOADER_START = (( __FLASH_SIZE - BOOTLOADER_SIZE) / _FLASH_ERASE) * _FLASH_ERASE;

This says, basically, that the start of bootloader begins at memory region given by the flash memory size minus the bootloader size. So, I don't know why, it divided and multiplied by the size of flash erase block.
The size of the bootloader is already given too.

I did nothing to the XC8 app to ensure it does not overlap, I just compiled it. How can I do ensure it does not overlap ?


texts:
I would like to know what circuitry I will need in order to drive a N-Channel MOSFET (IRF1405) with the load placed on the source.

From my understanding the laod is placed on the drain however I would like to build a H-bridge driver with ONLY N channel mosfets. The high side mosfets of the bridge would therefor require some method of driving the MOSFETS properly.


texts: Designing a state machine to detect if input was high exactly 2 times in last 4 clocks

texts:
Design a Mealy machine with a one bit input, and a one bit output. The
  output is 1 if in the last 4 clock s, exactly 2 of 4 values on input
  are 1. Use D flip-flops and discrete gates. Use binary state
  assignment

I have problem in drawing state diagram for this circuit. Isn't it too complicated? Because for each state, we can have too many different states based on previous one.

Can someone help me a little to simplify the problem?


texts: how to correctly power the LED of a push button?

texts:
So I've got a push button and a switch. Both of them have LEDs inside.
Both of them seem to have LEDs working at 12V.
But according to the specs of the push button, you could also use 6V.

My question is, wether you have to use a resistor for this LED and if not, how this actually works that the LED can accept different levels of voltage?

Would an LED rated for 12V even lit up when powered with 6V?
I actually bought a step-up converter to be able to use this LED with my 5V power supply. But now that I've read that you could use 6V, I am asking myself if I even need that step-up converter. What do you think?

The bush button has these specs.
I don't have a data sheet for the switch, but it is called "LA16JS".
Both of them seem to use 12 V for the LED.


texts: devices for measuring tension or detecting "slackness" in fishing wire

texts:
How might I go about measuring the tension in a line of fishing wire?  I'm mostly interested in determining when the line is in tension vs when it's slack.

The application is a boat-mounted depth-finder.  A weighted line could be lowered into the water via a stepper motor.  When the weight hits the bottom, the line goes slack and the depth is determined by the stepper motor's rotations.

I'm considering the feasibility of this approach vs a sonar/fishfinder-type setup.  A mechanical measurement would be kind of fun, in a way, despite its many flaws (accuracy, waterproofing..).  Thanks!


texts: How to implement a Recurrent neural network (RNN) on FPGA

texts:
For learning purposes, I want to implement a Gated recurrent unit (GRU)-RNN accelerator on FPGA. Can anyone please share how should I start and the learning path I should follow? I want to use Xilinx Zynq 7010 and prefer using system Verilog coding. I have already gone through a couple of online tutorials but don't have a clear idea about the whole process.
Thanks!


texts: I have a 50 Amp current shunt, Tyco, specified as "Accuracy class: 0.5 (0.25 USA)" What does 0.25 (USA) mean? Is it somehow equivilant to class 0.5 ISO, or does it mean something else? I'm not in the USA or Canada, and our supplier doesn't know either.


texts: Sparkfun using 500Ω resistor on circuit with 9V battery and 2V/0.018A LED

texts:
A Sparkfun tutorial explaining voltage, current and resistance shows a simple circuit where a LED is powered by a DC source (9V battery). The LED is a red 2V/0.018A LED. The tutorial explains that limiting the current flowing through the LED is important, and uses Ohm's law to calculate a resistor value of R = U / I = 9V / 0.018A = 500Ω, in order to limit the current to 0.018A and protect the LED.

Wouldn't using a resistor value of 500Ω cause a voltage drop across the resistor of 9V, leaving the LED dark because no potential difference is left?


texts: Why does E-ink displays have to do a full-screen refresh to remove ghosting?

texts:
E-ink readers (like a Kindle) has been out for years, but even now after several generations of the products, all of them still does a full-screen refresh to remove the ghosting.

I can't find the answer on the official e-ink website, however this question: Why does "flashing" prevent ghosting on E-Ink displays? does explained how E-ink works but still not anwsering my question:

  Why is it necessary to refresh the whole screen?

Wouldn't it be enough to just refresh the part that wasn't empty (white) plus some "padding" (since a answer in the linked question mentioned that "However, each cell might be influenced by its neighbors as well as the applied charge.")

For example, when we read a book, it's very likely that some part of the screen will be always empty (like page margin, line margin, etc...) why can't those reigons be left out (like when you use the "Page Flip" function in Kindle PW2, only the small preview window gets refreshed and the rest part of the screen stays still)

EDIT:

@CL. reminds me in the comment section that no matter how much "padding" is added, the boundary between refreshed and unrefreshed parts is always there... So as long as a cell could be influenced by it's neighbors, this won't work - duh!

But still, I think it would be nice to add a few padding to keep the ghosting away from interfering with new texts to keep readability without doing a full-screen refresh which I really, really hate.

So what's the technical difficulty to prevent this influencing between the cells? The latest generation of E-ink is "Carta" is introduced in CES 2013, no upgrade for two years already.


texts:
I'm trying to understand the following circuits for an MPPT, and I do have some questions:

Why there is a capacitor C6 in parallel with R2 for the voltage divider for analog reading, and how was the value of  0.1µF selected?
Why are (D11,D12) and (D1,D2) in that setup?
What is the role of this circuit (L1,R6,C2,D5,C9)?


texts:
I have made a sensor that produces a 4 bit output. I want to perform some logic based on patterns.

I was thinking if somehow I could give that 4 bit input to my computer, I could then write code to perform logic. But, the problem is, I have no idea how to do this.

How can I give a 4 bit input to the computer? Can I use USB or some other hardware?


texts: Why is it bad to have traces close to the edge of the board?

texts: I keep reading that one shouldn't have traces close to the edge of the board and am curious as to whether there is an electrical reason behind this or if it's a mechanical issue (like when they cut the pcb, it might somehow rip up the traces)?


texts: Can I use a DVI-D dual link cable in place of a USB-C cable?

texts:
TLDR: Can I solder a DVI-D Dual Link cable to a USB-C receptacle and will it work well?
According to the USB-C cable spec:

Figure 3-21 illustrates an example of USB Full-Featured Type-C cable cross-section, using
micro-coaxial wires for TX/RX pairs. There are four groups of wires: USB D+/D− (typically
unshielded twisted pairs (UTP)), TX/RX signal pairs (coaxial wires, twin-axial or shielded
twisted pairs), sideband signal wires, and power and ground wires .

Also according to the spec, there are 4 pairs of TX/RX signal pairs and 1 pair of UTP wires.
Although I couldn't find the specifications for DVI-D, I could see by looking at the pinout and cutting into one such cable that there are 7 groups of wires wrapped in aluminum foil. Each group contains 3 wires, two twisted signal wires and one drain wire (does this mean shielded twisted pairs?). This, along with the information above, would make me assume that the two cables are compatible, ignoring wire gauge since I couldn't find any such info for DVI.
Assuming I don't plan on using power delivery, can I use a DVI-D cable to transmit USB-C 3.1 data?
Long story:
I have been tasked with building a sort of a kiosk computer whose motherboard is physically separated from the peripherals. One requirement is that it must have a USB-C port, so I need to route a long (~2 meters) cable from the motherboard to the kiosk.
Ideally, I would use something like this USB C header cable from amazon.
Unfortunately, the panel where I have to mount it is so small that I can only fit a USB C female PCB connector soldered to a breakout board. I chose to use an Attend 217B-AG01, since this is what was readily available to me, which I soldered to a small breakout of my making.
The final problem I have is that the panel needs to be removable for maintenance purposes. As such, I can't just solder a cable to the breakout board and call it a day since that would mean I would have to either cut the cable to remove the panel, or to use a longer cable so that I can pull the panel off and have it hanging from the cable.
A better option would be to solder a small cable to the breakout board, which would have another connector on the other end of it. I could just use a simple USB C extension cable and chop off the male end to have it soldered to the breakout board, but I would like the free end to have a more secure connection, such a locking cable with a screw. I know there are USB-C cables with single screw locking plugs, but I just wasn't able to find a matching female receptacle cable. I suspect this is because the expectation is that the plug screws directly into the case/chassis of whatever you are connecting it to.
Alternatively, I could use molex or other kind of connectors with clips. The automotive industry is full of them. Problem is, even though the actual connectors and pins are cheap, the crimp tools I find are extortionately expensive.
This leads me to my question. There is one cable/plug which has enough wires/pins, is still somewhat common, can be found in both female and male variants and has locking screws: the DVI cable.


texts: How to select frequency resolution and window size in FFT?

texts:
I am doing spectrum analysis of a time varying signal with frequency changing from 200Hz to 10kHz. I am using the FFT for analyzing the frequency component in the signal. My questions are:

How to decide on the frequency resolution and window width for the signal?
Which type of window function is suitable for the time varying signal?
What should be optimum size for FFT?

The sampling rate of the signal is 44.1kHz.


texts: Current Limiter -- How to limit 16v 3.36a to 16v 1a?

texts: I am trying to equalize charge a 150AH Lead-Acid 12v battery. To do this, 16v at 1a needs to be delivered to the battery for a period of +-10 hours. If a 16v 3.36amps power brick (laptop charger) is directly connected to the battery then, amps drawn reaches 4.3amps and the power brick becomes extremely hot -- in danger of frying the power brick.


texts:
A designer in our team has a habit of putting freewheeling diodes on the output of every voltage regulator. Buck converters, LDOs, you name it. The loads in our applications are mostly logic gates, FPGAs, DDR3 RAMs and similar. No motors or relays (inductive loads). The reason for this practice he says, is that if there is a sudden negative transient during power off, the freewheeling diode will catch this.

But. I have never seen this in any other application except for systems with inductive loads. Is he just wasting board space?

simulate this circuit – Schematic created using CircuitLab


texts: Is there any connector for SMD components

texts:
I want to fine-tune the resonance of multiple LC-circuits with hand made inductors(coils), and SMD capacitors (NP0 type). Currently, I am tuning the resonance frequency by soldering and desoldering capacitors until I get the required accuracy. But soldering and desoldering is quite inconvenient and also, it may harm my PCB.

My question is: do we have any connectors/sockets to hold SMA components (e.g sizes 0806, 1206) in a PCB so that swapping the components become easier?

Other related details about the application:
This will be used in high-Q resonance circuit at 5-10MHz. Therefore, the contact resistance is expected to be as small as possible. Current through the capacitors will be less than 5A at 5-10MHz.


texts: Differential pair output voltage formula derivation

texts:
I am trying to get to the simplified form of the equation of the differential output voltage of a differential pair:

I know the correct equation is:

*Image above from Franco, S. Analog Circuit Design. Please let me know if it is not proper to show this excerpt here.

I am stuck with simple algebra, really. I want to get the equation 4.73. Here is what I did:

Notation:
In the book, VoD. In my text, Vodif
In the book, ViD. ViD is the complete differential input voltage, vid =vi1 - vi2. In my text, I named it Vdif.

Also I've just considered αf = 1, so it is not explicit in my equations.
Considering Ree too large and just ignored.

I am stuck at this point for a while now. This is not homework or alike. Just reviewing some basic concepts.


texts: What chips does a Sony Ericsson (feature phone) use? (e.g. K510i, K610i, W705, C510)

texts:
I'm trying to replicate the behavior of these awesome Sony Ericsson phones by using Teensy 3.6 so I'm wondering what kind of specifications and chips do these phones have.

The phones in question are: Sony Ericsson K510i, K610i, W705 and C510.

The chips I need to know about about are:

The CPU: Is it a microcontroller or a CPU or a System-on-a-Chip? What is the architecture? What is the frequency? Does it execute or interpret Java bytecode? Does it have an MMU? What are its I/O functions? DMA, hardware M2 card I/O, audio DAC? Would such a CPU be stronger than the one in Teensy 3.6?
The storage memory chip: What kind of a storage memory chip do these phones have? Is the storage embedded in the MCU/SoC?
Where is the RAM contained? How much of it and what type of it? SRAM or SDRAM? Is it in the CPU/MCU/SoC or is it a separate chip?
What encodes and decodes images, videos and music?
Do the display and the camera have any encoding algorithms in hardware/firmware?

Does anyone have any information about these phones?


texts: Identify this circuit symbol with two overlapping circles

texts: I came across some images of schematics and have never seen this component before - what is it?


texts: SR latch timing diagram or waveform with delay, help!

texts:
I'm having trouble solving these two problems (my solution and general solution showed):

What I did was follow the truth table and based on the combination on the graph draw the appropriate state with a delay of 10ns:

PLEASE HELP ME UNDERSTAND HOW TO DO IT AND WHERE I'VE GONE WRONG AS IM STRUGGLING TO DO THIS.
Thank you in advance.


texts:
My name is Nick. I’m a idiotic prideful 17 year old who didn’t think he needed to watch a youtube video before using his dad's oscilloscope. What makes this post more ironic is that I purchased an “oscilloscope tutor kit” which is just a PCB and tutorials to teach me how to use an oscilloscope. Where my trouble came in was it didn’t come with a power supply and it says “9V AC" on the PCB next to the barrel jack.
I found a very old AC bench power supply in my barn and checked it with a multimeter until the voltage read 9V RMS. I cut the end off of an extension cable and soldered that to a barrel jack that fit the socket. This is my first problem - I soldered the ground of the connector to the neutral wire not knowing there was a difference between neutral and ground. After that, having only used a multimeter before, I connected the ground of the oscilloscope lead directly to the grounded outer part of the barrel connector which tripped a GFCI and killed the power in my basement. Being the idiot I am, I reset the GFCI and did it again to the same result. The probe was in 10x mode if that helps at all.
Since it was only 9V RMS and I was in 10x mode on the lead, did I still harm and or destroy my dad's oscilloscope? I am very sorry for the length of this post and how basic it is but I need help.


texts: Better single via with long GND path or multiple vias with short GND path?

texts:
I want to ask if it's preferable to have a single via that connects multiple decoupling caps and components to a single point of main GND plane, like in this image: (of course all will be filled with a solid plane)

Or it's better multiple vias to have a short GND path and to avoid the effect of via parasitic inductance? Like this:

I read discordances about this, someone can tell me what is better? (in this case I have Analog power supply and Analog ground return, but this can be also a general power supply)


texts: Explanations of the "protected area" functionality are very brief and I want to know more. Is it in anyway related to CPRM? Does it use the whole card or part of it? Is it a form of write protection? How can I set one up?


texts: Why 7805c Voltage regulator drops the current if the current enters around 13mA to 7mA?

texts: I know there should be voltage and current drop from the voltage regulator but my question is why current drops off ?


texts:
The load cells here: http://www.cnloadcell.com/mlc700-postal-scale-load-cell and here: http://www.cnloadcell.com/mlc714n-personal-scale-weight-sensor have 4 wires (red, white, black, green).

The diagram is quite confusing, I think I can see it is somehow part of a wheatstone bridge.

But from reading up on Wheatstone bridges, each strain gauge should only have 2 wires and these gauges have 4? Is the diagram showing how to use just one gauge or many?

Two wires coming out the strain gauge:


texts: How to choose a Instrumentation Amplifier

texts:
For my project, I need to design a simple EEG circuit. As known, input signals are in micro volts.

After some research I understand that I should use an inst. Amp. to process the signal. Voltage gain should be 100.

The question is how I can choose the appropriate ins. amp ?
Any help or guide will be appreciated.

Sincerely.


texts: Some questions regarding ripple counter and 74HCT

texts:
I'm very new to the subject of counters and tried to simulate a four bit ripple counter using a D flip-flop IC 74HCT in LTspice.

If the above topology is correct I have some questions regarding this counter:

1-) In reality if I implement this circuit, do I need decoupling capacitors for VCC pin as used in opamps? Do PRE and CLR pins require resistors or is it okay to directly connect them to Vcc as in my schematics above?

2-) In what circumstances the propagation delay matter? In my circuit simulation what can I do to simulate and demonstrate the effect of propagation delay?


texts: I my project MOSFET need 13 v 65% PWM to trigger but controller output is 5 volt then how can I amplify this in voltage


texts:
I recently disassembled some old Night Vision goggles (Jakks Pacific Night Vision goggles) and found a 420x234 LCD Panel inside connected to a 40 pin ribbon cable.

Do you know of any drivers I could use to control the panel? I found a link to what I think is the datasheet LCD Panel datasheet. The datasheet calls for the use of an HX8224B driver however I could not find where to purchase one. Thank you for any help!


texts:
I want to get an approximate energy model for wireless sensors when a given task is executed. I know that we can compute the energy consumption from a PC based on the time performing a task. For instance, a 2.2 GHz pentium 4 with a 400 MHz FSB has a typical Vcc of 1.3725 Volts and Icc of 47.9 Amps which is (1.3725*47.9=) 65.74 watts which a process taking 0.00454278s will consume 65.74 watts * 0.00454278s = 0.305 watt seconds (or joules). How can I do the same operation for wireless sensor? For instance, this one from Intel . How can I get the energy consumed from that node from a task which took 1.5 seconds to be executed?

Which other elements should be considered to get a more realistic energy model? In overall, I want to know how much an operation consumes in-node for WSN.


texts: Desktop PC power supply is Inductive or resistive loads?

texts:
Our daily computers (Desktop PC, Server or normal laptop, mobile chargers)

are those power supply inductive or resistive loads?


texts: So this question seems pretty straightforward to me, just plug the values in and find the answer, however I have no clue as to where im supposed to get Vd from. Can someone explain this or help me understand what I've missed.


texts:
I have built the circuit depicted below in order to start a 10A 220V dust collector(Load 2) when I run my 20A 220V table saw (Load 1). So far, I have not been able to activate the relay to power load 2. The voltage output from the rectifier (as measured at the relay) is only 0.5VDC and the solid state relay does not trigger with less than 2.5VDC.  I have measured the voltage potential between the secondary of the 1:100 CST and a common line to be  13VAC.  I have checked the bridge rectifier with my multimeter and both legs show 0.56mV between AC legs and DC. I also built this circuit with a 1:500 CST but only produced 1.4VDC from the rectifier.  Thoughts?

simulate this circuit – Schematic created using CircuitLab
relay data sheet
https://cdn.sparkfun.com/datasheets/Components/General/SSR40DA.pdf
CST data sheet
https://www.coilcraft.com/senhitr.cfm


texts: PWM dimming with ZCD generates humming noise from fan at low speeds

texts:
I have created a circuit which implements PWM dimming using phase cutting with Zero cross detection which works well on incandescent bulbs but creates humming noise when connected to a fan.
I am using BTA16-800CW (Snubberless triac) to control AC and my triac driver is MOC3023. The ZCD is done using SFH620A-3 opto coupler. I have not connected any snubber / rc filters as BTA16 is mentioned to have it inbuilt.
Is the humming expected when doing PWM dimming ?
Is there any way to get rid of it ?

I am using the standard approach to detect zero cross as shown below.


texts:
I am creating a custom CPU and would like it to be programmable on the fly instead of hard coded in VHDL.  The issue I am having is that without initial code for the CPU to run, ISE will trim large amounts of my logic away.  I have tried using the 'S' attribute to declare my signals and variables as 'not trimmable', but that does not work on all of the signals.  I have also tried setting the keep hierarchy option in XST, but even that fails sometimes (complains that there is a conflict with the KEEP settings and will trim anyway).  Is there a way for me to tell ISE to not trim anything at all without having to create a default program that runs through every opcode?

Here is one of the errors I am seeing:

WARNING:Xst:638 - in unit cpu_instructor_copy Conflict on KEEP property on signal brain.current_opcode<0> and brain.stack_pointer<14> brain.stack_pointer<14> signal will be lost.

Without the S attribute, the stack_pointer will just get removed.

I have the following at the top of my 'brain' process

variable stack_pointer : integer range 0 to (2**mem_addr'length) - 1 := stack_origin;
attribute S : string;
attribute S of stack_pointer : variable is "YES";

Thank you in advance!

Edit: Here is the actual code (no attributes in it currently as those are on my personal test copy)

Edit 2: The problem was fixable by changing my program from a constant to a signal, adding a new process that could 'program' the CPU with serial (at least that's what the design thinks), and setting the Map process to not trim unconnected signals.  I will post the code a little later.  Thank you all!!


texts: How do I condition a really noisy pulse for a 3.3V microcontroller

texts:
I'm reading the pulse from my spark pulse on an old motorcycle and finally got a decent pulse, but it's too high for mere microcontrollers to use (~10V ±6V). I've attached a picture below, but disregard the voltage level and AC. After some adjustments the voltage is about 10 and in DC.

My goal is to get the signal to just clamp at 3.1V or so and hold till it drops out cleanly (no hiccups to trigger again).

Do you guys think the circuit below will be what I need?

simulate this circuit – Schematic created using CircuitLab


texts: how to find series inductance of a transformer

texts: I'm designing feedback loop compensator for inverter. here i have H bridge, output transformer and output capacitor. it is just like dc dc converter for inverter so i needed to know How to calculate series inductance of a transformer


texts: IC Timer 555 Astable Multivibrator 50% Duty cycle

texts:
I'm given this configuration to solve for a IC-Timer 555 in astable mode to get a 50% duty cycle however I'm having some difficulties in the calculations.

The circuit is modified a bit as shown.

simulate this circuit – Schematic created using CircuitLab

So during a HIGH output, Discharge is open and the capacitor charges in time 0.69R2*C2.

However, during LOW output, R1 is also grounded. In this case I'm having difficulty calculating the time period. If I could get some help in calculating the Tlow and thus proving that the duty cycle is 50%, that would be a big help.

$$What I'm getting is, Voltage across capacitor(t)=[Vcc/Ra*C + 2Vcc/3]e^-(1/C(R1||R2)

Now, a t=Tlow I should have Voltage across the capacitor as Vcc/3. On solving this I get Tlow = (R1||R2)*C *ln((3+2R1*C)/R1*C))

My attempt at the solution:

Applying KCL at the common node:

\$(Vcc-Vc)/R2=Vc/Rb + C\$*dVc/dt\$\$

Taking Laplace transform (Initial condition: \$ Vc=2Vcc/3\$
and simplifying:

\$ Vcc[1/R1 + 2C/3] = Vc *[1/R1 + 1/R2 + sC]\$

on Rearranging:
\$ \frac{Vcc(\frac{1}{R1} + \frac{2C}{3})}{(C*[\frac{1}{R1*C}+\frac{1}{R2*C}+s])}\$ = Vc

Taking inverse laplace transform, putting Vc=Vcc/3 for t=Tlow, I get the above answer. Please help me out.

I'm getting the correct answer by solving only in time domain, while I'm satisfied with that, I'd like to know what possible mistake am I making in the method using laplace transform?


texts: Why spectrum analyzer ruined my oscillator's output?

texts:
I have been tried to investigate and fix this problem by myself. I however cannot find the solution. Please give me some advises.

I used 3 traditional oscillator circuits with opamps (Wien bridge, phase-shift, and twin-T circuits). All of them work correctly when I measure with oscilloscope. I get the sinusoidal waves and can adjust their frequencies and gains. Everything is fine.

The problem is when I use spectrum analyzer (Rigol DS815). After the probe touches the circuit, my sinusoid is ruined (The harmonics rise up). I saw the change in oscilloscope at the same time too. Sometimes the signal disappears and I have to adjust gain to take it back.

In wien bridge, I varied frequencies from 500Hz to 300kHz and Tested with UA741, TL082. Still cannot work it out.

I am thinking that the problem is not about the oscillators, but how I use spectrum analyzer to probe it since the oscilloscope works fine.


texts: Design a veroboard/stripboard layout from an Eagle schematic

texts:
So I have just finished learning the basics of Eagle (Lite) and I really like it.  As I don't have the full kit to start home PCB etching yet (something I am looking into now) I would like a tool that could help me design a layout for a veroboard/stripboard.

If I had an Eagle schematic, how would I go about designing an equivilent veroboard/stripboard layout either within Eagle itself or possibly even through an export/import into another tool.

Thanks


texts: How to shield multiple flat (ribbon) cables properly?

texts:
I have a situation where I need to connect 10 flat cables (20 way, 0.625mm pitch) to special PCI-E card in my computer. They go from PCI-E card on back to drive bays in front of computer case.

Those flat cables are around 50cm length and come to PCI-E card in one group, from one direction. They look very neat, stacked one to another and taped to stick togeather. I've read that stacking flat cables largely increases EMI, maybe I should consider distancing them somehow?

I have experienced some problems with communication between nodes connected with flat cable and PCI-E card, which was realized to be EMI problem.

First, flat cables didn't have any kind of EMI protection. Then, I installed ferrite cores on both ends of the cables. That helped a bit, but there are still problems.

I have some ideas:

Putting aluminum tape around cables and grounding it on metal
case
Separating and twisting flat cables as much as possible (tho that
would look ugly and messy so I would like to avoid that)
Distancing them with one from another with aluminum tape and foam
tape

Are those good points?
What else can I do to get better EMI protection?


texts: How do superconductors avoid breaking Kirchoff's Voltage Law?

texts:
So, let's imagine that you've got a superconductive voltage source (e.g. a wind turbine) hooked up to a loop of superconductive wire to form a circuit. Kirchoff's Voltage Law states that the sum of electrical potential differences around a circuit must be equal to zero; however, in this scenario, you've got a voltage source hooked up to a circuit with no apparent voltage drops. In analysis of ideal circuits, this is where you add in parasitic resistance, but if everything in the circuit is composed of superconductors, their resistance would be zero, right?
Here's an image of the circuit (I apologize for low-quality because I made it in MS Paint because I don't have any professional circuit-drafting software, and I can't find the symbols used to designate things as being superconductors):

Obviously, there has to be something screwy going on here; where is the voltage dropped? Is there some sort of exotic property of superconducting materials that comes into play in these situations?


texts: How Specifically the Control Unit (CU) Works

texts:
I am a software developer now interested in the electronic implementation of computers.

When I think about computers, the thing performing the action is the "processor". But the processor is technically the CPU. So looking within that, what looks like is doing the actual processing is the Control Unit (CU). It turns out the GPU also has a CU(s).

  The CU receives external instructions or commands which it converts into a sequence of control signals that the CU applies to the data path to implement a sequence of register-transfer level operations...
  Hardwired control units are implemented through use of combinational logic units, featuring a finite number of gates that can generate specific results based on the instructions that were used to invoke those responses. Hardwired control units are generally faster than microprogrammed designs...
  The algorithm for the microprogram control unit is usually specified by flowchart description.

It is said that the control unit is what actually reads instructions from memory and runs them. But I'm wondering how exactly this works. Maybe not specifically the circuits because that seems highly dependent. But at a high level, what is the "spark" that actually is moving around electronically. What types of circuits there are involved. Whereas disk storage has a very detailed description (below), CU's don't (on Wikipedia).

My questions are:

On a modern computer like the MacBook Pro, if the CU is hardwired or a microprogram.
What is the actual spark or piece of electricity that is doing the "processing", i.e. "moving around the memory". How it actually "fetches from memory" and "stores to memory" and "fetches an instruction" and "executes an instruction". How it "reads an opcode", etc.. Wondering what is actually going on at the electronics level. Don't need to know each piece in detail if it's too complicated, just at a high level the electronics involved of any one of them.

While flip-flops have a detailed description so you can understand how actually a "bit" is stored, the CU is lacking so I can't actually tell how the program is "running". I would like to be able to explain how the computer runs, at a deeper level than that instruction cycle, down to the electronics.

Magnetic disk storage demo of how detailed the description is, to show you how it works.

  ...Due to the polycrystalline nature of the magnetic material each of these magnetic regions is composed of a few hundred magnetic grains. Magnetic grains are typically 10 nm in size and each form a single true magnetic domain. Each magnetic region in total forms a magnetic dipole which generates a magnetic field....


texts: Need help understanding how this decoder IC & differential amplifier circuit works

texts:
I need help to better understand differential amplifiers, when interfaced with an decoder IC. For the circuit below, which is from the reference design here:

It shows a mono differential amplifier (TPA751), driving a speaker on the same PCB. Not shown is the MP3 decoder IC (VS1003) driving the amplifier input. The amplifier has gain of -2Rf/Ri=2*47k/10k= 9.4. So the differential output is 9.4x the differential input.

As per the VS1003 datasheet, the output voltage from the CODEC (and input to the amplifier) is 1.7 Vpp (peak to peak) with a 1.2V DC offset.  The outputs from CODEC and into the amplifier IN- and IN+ terminals are opposite of each other (ie. IN+=--IN-). I’m trying to understand how this circuit would work and would appreciate clarifications on the following points:

1.7 V peak to peak for the CODEC output means an amplitude of 0.85V. Therefore, with the 9.4 gain of the amplifier, the output to the speaker will be 0.85*9.4 = 8.0V peak to peak (OUT+ relative to OUT-). Is this correct?
If we measure OUT+ (pin 5 of the amplifier) with respect to ground and not to OUT- (pin 6 of the amplifier), the maximum amplitude will be 4V (ie. 4.7*0.8).  So the signal will be from 0V to 4V. Is this correct?
Assuming the amplifier can produce a maximum voltage swing of VDD-1V, this means to avoid clipping, the power supply of the amplifier needs to be at least 5V. Is this correct?
My understanding is that speakers can’t handle DC offset. They must be driven by an AC signal. For our case above, based on the datasheet, there is no DC offset at the output.  However, the output signal can be though of an AC signal with amplitude +/- 2V and a DC offset of 2V. Is this considered bad for the speaker? Or is this not a real DC offset?

Thanks!
(This is my first ever post in this forum)


texts:
What is the penalty for using vias in PCB design regarding impedance, capacitance and EMI?

To make the question more specific:
Let's assume that the PCB is going to be used for an 8-bit computer with Vcc at 5 V. Is it safe to have a clock line (~4 MHz) through 5 vias compared to no vias at all?


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texts: Relationship between frequency and other signal characteristics

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As a signal travels through the air it loses it's energy. When the energy of a signal gets low what happens to frequency, amplitude and other characteristics of that signal?

Does frequency decrease due to losing energy?

Does amplitude decrease due to losing energy?


texts: How to know power consumption of core FPGA

texts:
I am using a DE0-Nano board in my project. It has an Altera Cyclone IV E FPGA chip in it plus other components such as ADC, RAM, etc. When connected to a USB power supply, the DE0-Nano requires around 5V to operate. However, from my research, the Core FPGA only uses 1.2V as its core voltage. When the board draws power, is it possible to identify which is due to the Cyclone IV E FPGA and which is due to the other components? I attached some links to schematics and references. I cannot figure it out on my own. Thanks in advance.

http://www.terasic.com.tw/cgi-bin/page/archive_download.pl?Language=English&No=593&FID=75023fa36c9bf8639384f942e65a46f3


texts:
I have written a code which takes two digit number from laptop and changes the PWM dutycycle to that number. It is part of a bigger requirement where I need to control motor speed over UART.

#include "io430g2553.h"
#include <stdint.h>

void PWM(uint8_t duty_cycle);
void PWM_Config();

int main( void )
{
  // Stop watchdog timer to prevent time out reset
  WDTCTL = WDTPW + WDTHOLD;
   WDTCTL = WDTPW + WDTHOLD;
  BCSCTL1 = CALBC1_1MHZ;                  // Run at 1 MHz
  DCOCTL = CALDCO_1MHZ;                   // Run at 1 MHz

   PWM_Config();
   PWM(5);
   __delay_cycles(5000000);
   PWM(15);
    __delay_cycles(5000000);
   PWM(25);
   __delay_cycles(5000000);
   PWM(50);
    __delay_cycles(5000000);
    PWM(25);
    __delay_cycles(5000000);
     PWM(15);
    __delay_cycles(5000000);
     PWM(5);
   while(1)
   {}

}

void PWM_Config()
{
  P1OUT &= 0x00; // Clearing P1OUT
  P1SEL |= BIT6 ;
  P1SEL2 &= ~BIT6 ;
  P1DIR |= BIT6; // Configuring P1.6 as Output

}

void PWM(uint8_t duty_cycle)
{
 TA0CTL =0;
 TA0CTL |= TACLR;
 TA0CCR1 |= (duty_cycle*100);
 TA0CCR0 |= 10000;
 TA0CTL |= TASSEL_2 + MC_1 + ID_0;// Register TA0CTL -> SMCLK/8, Up mode
 TA0CCTL1 |= OUTMOD_7 ;//Set/Reset Mode
 TA0CCTL0 &= ~CCIE; // Interrupt Disabled
}

Edited My question on received comment:

The problem with the void PWM(uint8_t duty_cycle) function is that first time it generates the correct PWM at P1.6, next if  it is given a value it changes PWM to that DC, but I can not go back to lower DC.

the fisrt 2 PWM functions in the code changes to correct duty cycle PWM(5),PWM(15) then the rest of PWM values do not produce desired dutycycle.

I am not able to troubleshoot where am I wrong, can any1 help?