texts:
I've tried to solve this contest question regards the band pass filter (find the frequency at low-pass and high-pass filters) the picture below:

My attempt:

I consider that the first stage is 2 low-pass filter identically (R1 C1) and (R2 C_2) -  circuit RC - \$R = 5\,k\Omega\$ and \$C = 50\,nF\$

So compute the cut-off frequency: \$ f_c = \frac{1}{2\pi R_1C_1} = \frac{1}{2\pi R_2C_2} = \frac{1}{2\pi \cdot 5\cdot 10^3\cdot 25\cdot 10^{-9}} \approx 636,6 Hz \$

Seems "ok".

Continue: when I look to the second stage I can see 2 high-pass filter (C3 and R3) and (C4 and R4)

cut-off frequency: \$ f_c = \frac{1}{2\pi R_3C_3} = \frac{1}{2\pi R_4C_4}=\frac{1}{2\pi \cdot 3\cdot 10^3\cdot 10\cdot 10^{-9}} \approx 5,3 kHz \$

The answer is letter d)

But whats about the others resistances the circuit? and when you use the same filter in series the simple question is: the frequency response has the same value when you use only 1 low-pass filter?

I tried to simulate this circuit and figure out that the frequency cut-off ( i guess) is  \$0.79kHz\$ e \$4.18kHz\$

SIMULATED FREQUENCY RESPONSE

I presumed that the correct schematic this circuit to match the same \$ f_c\$ as the question required must be such as the imagem below:

So, anyone has any advice to solve the entire circuit and provided a decent analysis to this circuit? thanks for any hints.


texts: What 'cool' things can you build as a parent and child activity?

texts:
I would like to have a list on things a parent could build with his or her child? The things should be considered 'cool', fun and not be too advanced (the child should be able to help out and be able to understand what we are doing). A child would be anything from a 3-4 year old kid up to (say) 12.

I know there are tons of science kits (and lego kits such as lego mindstorms and lego technic) out there so please try to avoid mentioning them.

Example:
One can build a laser from an old DVD burner [insert guide here].


texts: My multimeter is rated to 600V.  How can I readily (and safely) use it to measure higher voltages?


texts:
I have been following the tutorial below to build an AM radio, and when powered on I was picking up what id presume to be radio waves (what I'd describe as a mishmash of "whooshing" sporadic oscillations).

http://www.instructables.com/id/Simple-OP-Amp-radio/?ALLSTEPS

This was great, but I wanted to single out a specific frequency and listen to a radio station.  I did some research and figured out that I have to add a resonance circuit called an LC circuit to single out specific frequencies.  I made one with a variable inductor I made with 47 coils in 10cm with square steel railroad spike of diameter 1.5 cm in the center and a capacitor like below.  I experimented with 220 pF capacitors in parallel to make 220, 440, and 660 pF and tried using my variable inductor to tune into a station for each of them but it did not work.

(apologize for the poor drawing)

I chose that coil count using the following equation to tune into mid freq radio singles (535-1500  khz), I made sure it covered the lowest frequency and then I could shorten it to get the higher frequencies.:

At this point I was stumped, I heard that you had to put a diode in to single out high frequency singles so desperate, I inserted it between pin 3 and my LC circuit but it didn't help.  I also made a home made variable capacitor but likewise I coundn't tune into a station.  Most importantly I heard you had to ground the circuit so I attached a wire for the tuner circuit to my computer(which is ground) and it changed the tone slightly but still couldn't tune into a station.

I started to wonder whether there were any am stations in my area due to its falling popularity, but a quick test with my mother's car radio yielded handful of them.

I apologize if my troubleshooting may seem stupid but I'm a little new to this circuit building stuff.  I Thank you for reading thus far, and I appreciate any assistance you guys may offer.

^Current setup pic


texts: What happens after disconnecting DC powered inductor?

texts:
Voltage over an inductor is proportional to the di/dt.
I want to know what happens if I disconnect an inductor from a DC power suddenly.
After disconnecting no current could pass through it, right?
So the voltage must tends to infinity or make a spark?


texts: Low-Speed CANbus Common-Mode Choke Insertion Loss

texts:
I'm designing a low-speed CAN transceiver breakout-board (schematic below) and I'm trying to select the proper choke to use to reduce common-mode noise. I've found a few common-mode chokes meant specifically for CAN, and the one I'm trying to model is DLW43MH201XK2L. It has a DCR of 4.5Ohms and an LCM of 200uH. My issue is that I'm not quite sure how to model the circuit to determine the insertion loss.

I know that \$ I_{L}= 20log\left ( \frac{V2}{V1} \right )\$.
I'm thinking the circuit looks something like below, but again, I'm not sure if this is correct so not sure if my insertion-loss figures given in the AC simulation are correct. It would also be nice to figure out how to model the circuit to determine the differential-mode insertion loss to ascertain the distortion caused to the signal, but I'm not sure how to do that either, and Ldiff isn't given in the datasheet. Is my model correct?


texts: Son's science project (high powered fans)

texts: My son (an aspiring inventor in the 5th grade) is aiming to design and prototype a 'levitating shelf'.  The shelf can be any size (or material), the key is that he would like to use fans to try to levitate it off the ground.  I would love some advice on what sort of fans might be needed and where to look.  Any other input on making this get off the ground (even briefly) would be much appreciated.


texts:
I'm trying to design a speed trap for an airsoft BBs. My original idea was to use IR photosensor. But this solution is prone to fail if dirty.

I'm playing with the idea to use a coil on a PCB with hollow centre where a BB would fly through. Can I use change of relative permeability of coil's core to detect proximity of a plastic BB? Would it be practical?

BB's diameter is 6mm and it should fly parallel to PCB coil with hollow center.

Thank you


texts: How to size an in-line fuse for the input of the DC-DC power supply

texts:
I have purchased a Meanwell switching power supply with the following specifications:
Input: DC 36-72V (6.7A)
Output: DC 24V (8.4A)
I want to put an inline fuse on the positive cable going to the input of the power supply (V+). The load is around 7.2A. The source is from a 48V forklift battery.
The reason for the inline fuse is to protect against shorting the inputs when connecting power. Should I spec the fuse for the input current of 6.7A and use an 8A fuse or should I spec the input fuse for the output of 8.4A and use a 10A fuse?


texts:
If an LDO generates 3.3V/300mA output voltage and current, what is the input current of the LDO?

Must I give more than 300mA current at the input?


texts: Why does the peak power change with the spectrum analyzer's span?

texts:
Consider a continuous wave signal being displayed on a spectrum analyzer at f=5GHz. It's a single peak. When I put marker on the peak it shows me the peak measured power. Now when I decrease the span of the instrument from 10MHz to, lets say, 1MHz, the measured peak power is increased. Can someone explain why this is so?
I am sure it has something to do with the RBW of the instrument. Also if the power changes with span, if I just need to measure the peak power should I be using zero span mode?


texts: Diffusion capacitance approximation for bipolar power transistor

texts: I'm trying to remember the approximation for the value of the diffusion capacitance for a bipolar power transistor.  I think it might have been gm/Ft?  Can anyone confirm this and/or give a reference? Thanks!


texts:
My main problem in this deign, as you can see, is the mosfet gate driver circuit .

How can the latter be improved, assuming that it cannot oscillate?


texts: If I have a device drawing 300mA @5V and I need to use a 15V PSU what current rating do I need for the PSU?

texts:
I have an application with multiple components and multiple voltages in use and current calculations are giving me a headache.

A simplified version of my application would include:

1x device drawing 300mA @5V
1x device drawing 100mA @6V
1x device drawing 500mA @12V
1x 13.7V SLA battery being trickle charged

In order to trickle charge the battery I need a 15V PSU with current limiting resistor fed from the 15V PSU.

Done.

In order to supply 12V, I am using a voltage regulator MC7812 fed from the 15v PSU.

Done.

6V device gets power from a step down converter 62180 fed from the 15V PSU.

Done.

The 5V device feeds off the 62180 6V supply and uses current limiting resistors to reduce down to 5V.

Done.

But what wattage PSU do I need?

Using P=IV suggests
P=0.3 x 5 = 1.5w
but as my voltage supply is ultimately 15V and not 5V, would I need to multiply this by 3 (to get current draw at 15V) before adding to the other calculations or can I just calculate the wattage for each device (@ each devices voltage level) and then add them up?

using method 1 (excluding the SLA battery):
(0.3*5) * 3.0  = 4.5w +
(0.1*6) * 2.5  = 1.5w +
(0.5*12)* 1.25 = 7.5w
               =13.5w

However using method 2 (excluding the SLA battery):
0.3*5  = 1.5w +
0.1*6  = 0.6w +
0.5*12 = 6.0w
       = 8.1w


texts: Fixing the wiring on a keyboard sustain pedal

texts:
I have a cheap keyboard sustain pedal of the basic on/off variety. When the footswitch is pressed down sustain is on, and off when it's released. There is also a polarity switch so that it can be used with different makes of keyboard.

I opened the pedal to apply some grease and when doing so managed to disconnect the wires from the footswitch. I don't know the correct way to reconnect these wires. I have a attached a quickly drawn diagram of how things look.

The smaller rectangle is the polarity switch, which has 3 prongs, and the larger rectangle is the footswitch, with 6 prongs.

I need to know what numbers on the footswitch do the blue, green and red wires connect to, and also if any of the prongs on the footswitch should be connected to each other.

PS. Here's a few more photos as requested. I changed the colours of the wires in my diagram for the sake of clarity (pink in diagram = white, blue = black, green = red, red = also red).


texts: Wake up with external Interrupt from deep sleep mode (Adafruit Feather 32u4)

texts:
I have an Adafruit Feather ATMega 32u4. I want to put it into sleep mode and wake it up with pressing a switch as an external interrupt. This is what I tried so far and which worked:

switching a LED on and off with the switch
putting the Adafruit to sleep and let it wake up with a watchdog timer.
I tried to combine the code examples that I found in the Internet to make the code fit my board. I manage to put it to sleep but then I have to reset it because the Interrupt doesn't work. I would be very happy for any help and please don't blame me, I am a complete beginner!

Here is my code:
#include <avr/sleep.h>
#include <avr/power.h>
#include <avr/interrupt.h>

int pin2 = 2;

void pin2Interrupt(void) {
/* This will bring us back from sleep. */

detachInterrupt(digitalPinToInterrupt(2));
}

void enterSleep(void){
/* Setup pin2 as an interrupt and attach handler. */

delay(100);
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sleep_enable();

attachInterrupt(digitalPinToInterrupt(2), pin2Interrupt, RISING);

if (digitalRead(pin2)){
sleep_mode();}

/* The program will continue from here
   First thing to do is disable sleep. */
sleep_disable();
}

void setup(){
Serial.begin(9600);

/* Setup the pin direction. */
pinMode(pin2, INPUT_PULLUP);

Serial.println("Initialisation complete.");
}

int seconds=0;

void loop(){
delay(1000);
seconds++;

Serial.print("Awake for ");
Serial.print(seconds, DEC);
Serial.println(" second");

if(seconds == 3){
Serial.println("Entering sleep");
delay(200);
seconds = 0;
enterSleep();
}
}


texts: How can I trigger other circuits based on specific values of a 12 bit ripple counter?

texts:
I've built quite a few circuits but I've never really designed anything from a "schematics first" approach.  Mostly just tinkered with designed and code until I got it right.

Now, I want to build a horizontal timer circuit for an NTSC computer project I am working on.

Anyway, assuming I have a 74xx4040 12-bit ripple counter that is clocked at 7MHz I want to enable other circuits when the master counter (the 74xx4040) reaches certain values.  The counter would count from 0 to 447 and on the 448th value reset to 0.

During those 448 counts, I have identified the following bit values as my "trigger" points.  These are the 4 MSB's.

0001 00000  (32)
0010 00000  (64)
0011 00000  (96)
0100 00000  (128)
1100 00000  (384)
1110 00000  (448) -- RESET

Other than putting a crazy amount of AND/NAND/NOR/etc. gates connected to the 4 MSB's, is there a simpler way?  I only have 2-input gates available (AND/NAND/NOR/XOR/etc.).

My thinking is that each area of the circuit would be clocked by the same 7MHz clock.  And as the master counter reached, say 96 for example, the first 4 bits (0011) would turn on the CE pins of all of the other IC's for that section.  And when the master counter reaches 128 (0100) then only that section would be enabled and the CE of the previous would be disabled.

Hope that makes sense.

Is this a practical/sane way of approaching this?

Thanks


texts:
I use 2N3904 as switch to power off/on the NEO-6M module control by Atmega328p.

I can draw until 96mA ( 100 mA ) .

I see on the stackexchange that Ib=Ic/10 to force full saturate the transistor.

Compute the current for base Ib :

Ib=Ic/10
Ib=100/10
Ib = 10mA

Compute the Rb :

Rb = (VCC - Vbe) / Ib
Rb = (4 - 0.95 ) / ( 10 / 1000 )
Rb = 305 Ohm

But when i put 305ohm / 100ohm to base the gsm module power on but restart loop, I think Ic do not provide enough current.

I strange but when I connect the GPIO directly to the base it works ?

Note : I share the same VCC between the collector and base emitter (from my lithium battery).

Maybe the transistor is not design for my application maybe connect two transistor as darlington ?

Regards


texts: Why amplifiers (RC coupled) are based on voltage divider bias?

texts:
What actually determines the type of bias to be used for different practical applications.
Also I do not get the point of using capacitors (coupling) for emitter current and high input resistance. If input resistance is high the signal is not likely to pass through base. Please correct me if i'm wrong.


texts: How to achieve feedback in regenerative braking?

texts: I’d like to implement regenerative braking in my own brushless ESC I’m designing. I’m stuck however on the part regarding voltage step-up. As I understand it, ESCs during braking usually use the motor as a boost converter to increase back EMF voltage to battery voltage in order to charge it. However, I have no idea how the output voltage is measured for feedback as it would be connected to the bridge supply lines and hence we would actually be measuring supply voltage. How is this feedback achieved in a commercial ESC?


texts: Aluminum Electrolytic Capacitor with small dent still usable?

texts: I have three 10000µF 75V Aluminum Electrolytic Capacitors. The aluminum can has a very shallow dent. Would you think this is still safe to use them? I have three of them, and they are expensive


texts:
I have lessons about VHDL in one of my university class and I have to write simple entity which will generate clock from 1MHz source. I'm using CoolRunner-II CPLD Starter Kit with ISE Webpack 13.1.

When I run simulation of my code, I've got odd results. I have no idea, where the problem is. My VHDL entity looks like this:

entity clock is
  Port ( clk_in : in  STD_LOGIC;
    clk_1M : out  STD_LOGIC;
    clk_500k : out  STD_LOGIC;
    clk_100k : out  STD_LOGIC;
    clk_1k : out  STD_LOGIC;
    clk_1hz: out STD_LOGIC);
end clock;

Input is 1MHz signal from oscilator and I want to create 1MHz, 500kHz, 100kHz, 1kHz and 1Hz output signal. I defined several signals:

signal c100k: std_logic_vector(3 downto 0) := (others => '0' );
signal c1k:  std_logic_vector(9 downto 0) := (others => '0' );
signal c1hz: std_logic_vector(9 downto 0) := (others => '0' );
--
signal c500k_out: std_logic := '0';
signal c100k_out: std_logic := '0';
signal c1k_out: std_logic := '0';
signal c1hz_out: std_logic := '0';

And finally, my code is:

process (clk_in) begin
  if clk_in'event and clk_in = '1' then
    -- 500kHz
    c500k_out <= not c500k_out;
  end if;
end process;

process (clk_in) begin
  if clk_in'event and clk_in = '1' then
    -- 100kHz
    c100k <= c100k + '1';
    if c100k = X"A" then
      c100k <= (others => '0' );
      c100k_out <= '1';
    else
      c100k_out <= '0';
    end if;
  end if;
end process;

--
-- Code for 1kHz and 1Hz is same as 100kHz
--

clk_1M <= clk_in;           -- Clock source 1Mhz
clk_500k <= c500k_out;  -- Clock source 500kHz
clk_100k <= c100k_out;  -- Clock source 100kHz
clk_1k <= c1k_out;      -- Clock source 1kHz
clk_1hz <= c1hz_out;        -- Clock source 1Hz

When I run simulation, I got this odd results:

What is wrong with my code?


texts: How are stuck at faults in a combinational circuits considered

texts: I came over this example given in literature explaining the stuck at faults (possible) to be considered in a combinational circuit. I don't understand why g, h, i nodes in the circuit are considered seperately... If its because those correspond to a particular Logic gates design fault.. then why wasn't a stuck at fault considered for the last outermost NAND gate whose output is "z" as shown ?


texts:
I'm using a voltage detector for a solar powered ESP8266 project. Its purpose is to make sure that if for some reason the battery goes below a certain value (around 2.7v) then the MCU goes into "zombie" mode and does not power up as needed again. So I tried to use a voltage detector.
According the datasheet (see Test 5 figure)- there is a resistor RL which noted at the beginning as 200 ohm, and a capacitor, whose value is not noted anywhere.
When using without RL and capacitor, erratic behavior after sleep reboot occurs causing it to it to fail (MCU's led flickers very rapidly.)
Is there a rule of thumb for the capacitor?
**Edit 1 Circuit: **

Although tried several combinations of R1(200,1K, 10K) and C1(3.3 to 1000uF), I still get the following behaviour :

Dropping down input voltage from 5.5v to 3.3v works as expected (ON ), while going below 3.3v - cutting off the voltage to merely 0.1v ( measure at RST ).

Going back up ( 0v -- ~2.5v ) - measures 0.1v anf then, until ~3.8v (!!) MCU's boot led flickers, while measures at RST pin rises from 1.6v at some point to 3.0v ... and when Vin reaches 3.8v RST pin is arround 3.3v.

when MCU is not connected, going up & going down behaves as expected.


texts:
I am looking for a Zero Insertion Force (ZIF) socket with 0.1" between the two rows. The socket is to accept a DIP header like this:

So one side of the header would go into the ZIF socket, the other side is soldered to a PCB that is being tested.

The problem is that all the ZIF sockets I have found are similar to the green one below. They have 0.1" spacing between pins, but the two rows are at least 0.3" apart (they are all made for DIP package chips that are 0.3" across or more)

Has anyone used or seen or have any ideas on a ZIF connector that would fit a DIP header/connector with 0.1" spacing between the two rows?


texts: Why transformer is used in arc welding and what will happen when anyone touch the electrode at the time of welding?


texts: MFRC522 - Impedance control with External Antenna

texts:
I am a newbie into the world of RFID. For one of my upcoming designs, I am using the chip MFRC522 and an external antenna. The antenna is W7001.
As you can see in the datasheet,

It is mentioned that the impedance is 50/80. Could you please tell me what this means ?

Further, I have done my calculations for finding requisite passives values for EMC filter, matching circuit and antenna.
In these calculations, I have chosen R match to be 50 Ohms. Can you please confirm if this is correct for the antenna chosen?

The schematic as of now looks something like this.

So, my next question is depending on Rmatch, how will trace widths and trace impedances of TX1 and Tx2 change ? i.e. Lets assume Rmatch is 50 Ohms. Does it mean that single endedly both lines ( Tx1 which runs upto L1 , Tx2 which runs upto L2 ) have to  be 50 Ohms impedance matched in the PCB ?

Hope I have clarified myself. It would be really great if anyone can help me with this.


texts: Current in Saturation and Active regions of BJT

texts:
In the image(http://www.allaboutcircuits.com/vol_3/chpt_4/4.html), the result of SPICE simulation for active mode operation of BJT is shown.

The current source is set at a constant value of 20uA and the collector bias voltage is varied from 0 to 2V.

If you see the description of the image, it's mentioned that:

"A Sweeping collector voltage 0 to 2 V with base current constant at 20 µA yields constant 2 mA collector current in the saturation region"

Constant 2 mA collector current in the 'Saturation Region'? As I have understood, the saturation region is the part that lies to the left of active region(where Vce is almost zero) From what is shown in the image is it not that the 2 mA collector current in Active Region?

If the voltage is increased above 2V, there would be no change in the collector current as it's limited by the base current. The maximum current that we have as output is 2mA. How do you say that the transistor is now in Saturation mode?

Please explain me why the saturation region is indicated to the left of active region? From the characteristic curves, it seems that the region that is marked as 'active', is actually the Saturation because there is maximum collector current there.


texts: Altium database library management - Is it possible to edit same database lib by two people?

texts: We are using Altium database library. But our concern is if an engineer is working on the library then another engineer who needs to add new part in the same database have to wait. Is there a way to add the component in the same library by two or more persons at a time?


texts:
I'm looking to build an amplifier circuit to amplify a small DC voltage signal (between 0-15mV) to the range of 0-1.3V. I tried messing around with a standard non-inverting op-amp amplifier circuit but have found that the gain is not consistent in this range, it increases as the input voltage increases until the input voltage reaches 20mV then stays steady until the output hits the rail (as expected).

My question is are there any good circuits that can be used to amplify DC voltages with a consistent gain at this level of input. I need to be able to math my way back to the original signal (from a photo-diode) so consistent gain is important. Also this is for a class so I need a circuit I can build with components, not one chip that solves the problem.

Thanks!


texts: Formula for efficiency of half wave rectifier

texts:
I came across this formula for rectification efficiency of half wave rectifier:

η= (40.6 *resistance of load resistor )/ (resistance of load resistor+ resistance of secondary of transformer + resistance of semiconductor diode)

I couldn't understand how is it derived, although I am familiar with the derivation in which no resistances are considered and efficiency is obtained as 40.6 %.
Can someone help me with the logic behind this formula?


texts: why does absolute encoder (even multiturn) have the option of an additional incremental output

texts:
Many companies make absolute encoders for motor drives some can output an optional incremental track . my question is why is that needed since the encoder have a BiSS interface that can go as high as 10Mbit/s .

for example : https://www.kuebler.com/usa/prod-sen-multiturn.html

I have read on this site somewhere :
Magnetic Encoders - Tips and Tricks

Qoute :" I wouldn't recommend closing a velocity loop on absolute position feedback but rather use quadrature signals"

If this is true then my initial guess is that the cascaded Closed loop drive use Absolute output for position loop and incremental for speed loop .

But why ? It doesn't make any sense especially that absolute encoder have much higher single turn resolution (up to 17bit and even 21bit) which can be really helpful for controlling motor at very low speeds.


texts:
I want to build a spotify controller [next song button for the moment] with Arduino

to build something like this song changer physical song changer

What do I need to control my spotify? using a windows machine? [using processing?]

the examples I have seen use a mac and AppleScript spotify box

so do I need to connect to the spotify  API with Processing ??

do you guys know of an example to do this?, if not, what would be the best way to accomplish it?

thanks!


texts:
I am using an instrumentation amplifier AD620ANalong with another amplifier TL084CN in series. Both have gains of 100 which essential for me since the input is in microvolt range. The frequency is 87 hz and note channel 1 is input while 2 is output.

The circuit diagram looks something like this [
 Readings:

When normal input of 1.76 volts is given the DSO shows the expected output of square wave of similar frequency as the input as shown in the image here
When the input signal is attenuated by 20db the signal still tends to remain intact showing the same frequency of the input with a question mark on DSO
image
Now here is where the problem starts whenever I switch my function generator to 40db or 60 db the signal at the output is square wave but the frequency is not the same and again a question mark is seen in the DSO in the frequency  slot. And the distortion or frequency changes even further with 60db. This can be seen in below 2 images.
40db
60db

Technically the frequency shouldn't change throughout the process. Believing in this my professors and lab assistants told me that the frequency is actually the same however the DSO is causing errors and hence the frequency shown is different by the DSO. But I don't believe this because if it was a small signal of small amplitude at the output then I would understand that the DSO is not capable of sampling such small signals but since in the images you can see that the output is in the range of 8 volts then how can an instrument show false readings?? Also initially when the input signal was at 1.76 the output was pretty smooth and as expected but after making input smaller the output is varying then definitely it has got something to be related to the circuit I have created.
Am I right or wrong?
Can anyone spot if there's a different problem?
Suggestions please!

Update:
I found out hysterisis was the problem. Thank you for your help!


texts: Can you connect in series 2 unequally charged batteries?

texts:
So I have 4 batteries. 2 of them are charged (about 70%) and 2 about 10%. I have a flashlight (which uses 2 batteries in series) which I would like to power at small current and voltage because the light produced is too powerful. Would combining a charged battery and discharged battery be a good idea? If not, what can I do? I thought of placing a piece of iron where the discharged battery would be so it conducts the current from the first one. Would that work?
Note that they are single use batteries.

Thanks in advance!


texts: Change antenna so bluetooth beacon works in all directions equally well?

texts:
I am looking at using a long range bluetooth LE beacon on a project.  The beacon comes with a SMA interface whip antenna that has the following radiation characteristics.  It is over my head to clearly understand the report but I think it is indicating that the antenna has weak zones at the ~0, ~60, ~120, ~180, ~240, ~300 off of vertical.

First off, is this correct?

If so then this has some downsides to my project. This beacon will be mounted in an large ball and will rotate with the ball so the orientation of the antenna could end up in positions were it has a very short range.

Second question: Is there another style of antenna I could use that would be more uniform in all directions?  I assume it would mean sacrificing the maximum distance it would be readable?  However if I can get even half of the stated 4000m distance then it this could still work quite well for me.

In case you are wondering about the final application:  The ball is actually a 3ft diameter 20 sided die that is an art piece which is free to roam around a festival site.  The purpose of the beacon is to allow us to track it down periodically to make sure it's okay and to do any maintenance.

Thank you for any clarity you can provide.


texts:
There is a term in HDL simulation/verification called
"backdoor memory access".

I've heard this a lot of times though I'm
not sure how is this implemented.

Also, there are a few references for this concept.


texts: Does this look like amplitude modulation?

texts: I have designed a transmitter and a receiver  for amplitude modulation. Does the signal in the image looks like amplitude modulation?


texts: I have a bunch of green LEDs (not super bright), the plastic around the actual LED is physically green, but they did not come with a turn on voltage. 3V seems to work but they're not too bright, is there any way I can figure it out? What's the standard turn-on voltage for non super bright green LEDs?


texts: How can I use formulas in MC34063 DC-DC converter datasheet?

texts: In MC34063 datasheet, for step up configuration we have this table that describes calculation procedure. I stucked with this recursive formulas in this table. Why they providing such unresolved calculations in the datasheet? They cannot be used as they are in the table, as I thought and saw in another datasheets. Does it mean, that I should resolve equations by myself in order to find ton and toff?


texts: Automatically numbering elements in Kicad

texts:
Does Kicad have a function to automatically number components?

At the moment, whenever I insert a new resistor, I must also number it (e.g. R? -> R12). Is there a way to do that automatically?


texts: Is it safe to use MR16 12V AC halogen bulb on 12V DC power source as artificial load

texts: I'm searching for a artificial load for an old computer PSU (cheap chinese 400W, only passive PFC) and found in a box a couple of halogen bulbs rated for 12V AC (35W). Tried one of them on the 12V wiring (the yellow one) and the bulb worked for 20-25min without problems - no strobing, no overheat, PSU looked stable for its class (12V rail showed ±0.08-0.15). What can possibly go wrong?


texts: Multimeter shows different voltages for positive and negative voltage(interchanging multimeter probes) for same source

texts:
I have designed a 5v and a 3.3v regulator getting same source of 12v battery.
When I measure, the 5v regulator output shows -4.67v for + on black probe and - on red probe, and 5.12v when red is connected to + and black to -.

Similarly for 3.3v regulator...

Now I have an Arduino project and it includes a flow sensor. This project works fine if the serial port is connected to a laptop. But if I only connect an external power supply as described above, the sensor gives some output even if there is no flow.....

[The second problem involving a flow sensor has now been asked in a separate question here.]


texts:
I have soldered a simple adapter to connect my AVRISP mkII to my bradboard.

The AVRISP mkII couldn't communicate with the ATmega on my bradboard. After a while I figured out, that the voltage at the reset pin of the ATmega is only about 3.2 volts. I disconnected the AVRISP and still the voltage was at 3.2V. After plugging out my adapter the voltage was back at 5V.

After inspecting the solder pads and some cleaning (I even used a knife to be sure nothing shorted together) I reconnected the adapter and measured again. The voltage is at about 3.7V.

What is causing the voltage drop? Can the remains of flux conduct?

The picture shows my adapter (back and front) the red line is connected to the reset pin, the blue line to the GND pin.


texts: Low-impedance tap in this oscillator circuit

texts:
Here is the schematic of Michigan Mighty Mite, a popular transmitter circuit design. It seems to be quite close to a regular feedback oscillator, with a few peculiarities.

What puzzles me is the mechanism how the feedback (output from the transistor amplifier) is fed back to the LC circuit. The inductor in the LC circuit has a tap. I've been explained that the tap is made closer to one end of the inductor because that is the "low-impedance point" of the inductor. As the LC circuit is being fed through a lower impedance, more current gets out of the amplifier and therefore there is more oscillating current on the LC circuit and thus a larger signal gets out to the antenna.

I attempted to draw a simplified schematic of the LC circuit and the amplifier in this circuit, omitting everything else, including the crystal:

simulate this circuit – Schematic created using CircuitLab

The battery appears as a short for an AC signal, so one side of the LC is connected to the ground. I omitted details of the amplifier and replaced it with a generic amplifier whose output is being fed back to the LC circuit, and the two inductors represent the tapped inductor. Is this anything close to representing the circuit?

Now, if the tap is made closer to the battery, the amp sees a lower impedance. But how does the current flow from there? It now sees a lower impedance to the ground, is that where the current goes? But then again, the amplifier is an inverting one, so I'm not sure what happens here.

So my question is: How does this idea of having a lower impedance tap in the LC part of this circuit increase the current oscillating in the circuit?


texts: On one of my boards we were using integrated circuits with PDIP layout. Some of those ICs died recently, and we wanted to replace the ICs with newer versions. Unfortunately, now we only can buy SOIC packages. Is there a way to mount them on the existing board (with the PDIP-layout) without having to design a new board?


texts: Frequency and magnitude of power variations in a DC circuit.

texts:
I have a 5 V 5 A power source which is connected to a simple development board with a processor that draw current dependent on utilization. I use a multimeter that measure 1000 samples / s to measure energy consumption. I measure a voltage drop across a shunt resistor coupled in series with the input power to calculate average power and energy consumption of the development board.
My question is : What can we say about error in this case ? Between two samples with a 1 ms interval, how frequent and how much can the power fluctuate in this interval ? Is there any way to find this out ? It would be unfortunate if there are several violent spikes between the samples.


texts: Whats the most interesting to build with 7400 series

texts: I'm currently doing a project and have no idea what to build


texts:
I'm currently working on a project to create a sustainable energy system. I have come up with a design to the system.

A model house will be produced and on top of the house there will be solar panels, however I would also like the solar panels to tilt towards the direction of the light.
 In order to do this I will need some sort of hydraulic mechanism; to tilt the solar panels. Could someone suggest a type of hydraulic mechanism?
For this part I would require using solar panels, light sensors and some sort of hydraulic mechanism, in order to tilt them to the direction of the light.

I was also going to use a wind turbine to harness some wind energy that will be produced.

I have also come up the idea to produce a miniature water wheel; these will work when it’s raining

I was also thinking about producing a small dam, however I wanted the flow of the water to be dependent, on how much energy will be produced by the other systems.
 After doing a little bit of research I came to the conclusion that a micro controller could be programmed, in order to do this automatically.  could anybody suggest a suitable microcontroller that could be used ? I also know that when programming a micro controller it uses a very low form of a programming language. so would I be able to write my program in a higher programming language and be able to use a compiler to produce the code necessary.

I have also got a budged of £20( approx$36) so I wouldn't be able to use an Arduino or a raspberry pi.
All of the wiring a circuitry will be done on a breadboard.
Could anybody answer some of the question that I have? also does anybody have any suggestions and improvements. I have also attached a diagram in case people are still confused.


texts:
Trying to figure out what this is, and suitable replacements.  Markings are "1 Wt 77" Cannot seem to find anything.

Edit: I removed and sized it today, looks like 2.04 mm square package, exactly like the one on the below spec sheet... but not that part. Still cannot find those markings...


texts:
I recently visited a factory in China and saw people soldering headphone pins with a soldering device that gave sparks, melting the tin. The soldering iron was hooked up to a device and the pin was also connected with a tool to this device, which has a dimensions of a small coffee table. The input was 220v AC and output 5v DC. There was another meter that said 30. Could this have been the current? What device would be able to reproduce such a spark for soldering? A cheap welding machine?

Edit:  Thanks to you all for helping me!

I do not have a picture of the device a saw. It was similar to this device (made for spot welding batteries) only the size of a small coffee table:

They use this to solder wires to jack plugs for headphones with high speeds and reduced energy costs (compared to heat soldering).
The process is old but not documented in for example YouTube.
However, you can all see it here.

The person in the video is doing it so fast that the tip runs hot. The tip I observed in the factory did not run hot continuously, or the settings (ampere) were lower, or the guy was slower. What I observed was more with a spark of about 5 mm.

I want to simulate this process at home, only one pulse, not multiple sparks like the video. I will therefore start with tinkering around with an old PC power supply 5V 20A or old car battery 12V 40A. Probably going to buy someone a coffee at the university to give me some help with this.

Edit: 2016-01-17
I have taken a photo of two devices who do the same thing:


texts: Configuring TI TPA6138A2 for Single-Ended PWM Inputs

texts:
I'm looking to use the TPA6138A2 to ground-center, LPF, and amplify 2 PWM inputs (between 0 and 3.3 V). My desired LPF cut-off frequency is 18 kHz and I would like to use a digital potentiometer for volume control (I was thinking a 10 kΩ potentiometer should do the trick).

What R and C values should I use with respect to the passive components shown in Figure 10 found in the data sheet (TPA6138A2) for my application?

Figure 10:


texts:
I've recently designed a FPGA breakout board using an FPGA BGA package, and due to the lack of packages I had on hand, I got the BGA-256 and drew new symbols and updated the connections from scratch.

Everything was spot on until I started drawing the schematic - upon a quick spot check to the PCB layout, my one BGA had turned into two identically-oriented packages with identical airwires as well as identical pin consolidation within the BGA array.

Any ideas on how to correct this issue? I cannot delete the duplicate part because if I do, I receive the "No forward-/backward-annotation can be performed!" error. Here's the schematic:

Board with "cloned" device:

So, what I was trying to do is put two pairs (four FPGAs) of FPGAs together for bitcoin mining onto a DIMM-form card that can "hot socket" into a multi-socket backplane/motherboard that carries the I/O and interface devices.

To save space and prevent from cluttering the schematic excessively, I decided to only connect pins that I determined were needed for my setup, namely the configuration and power pins and certain pins from I/O banks 0 to 3. Mapping these pins would also give me a much clearer view upon routing.

This is why the FPGA symbol in the schematic is multi-grouped and not a standard shape or size. The larger symbol to the left is a representation of the DIMM edge connector that I will build these FPGAs to. The only connection I have made at the point of screen capturing was to tie low all appropriate grounding points on the edge connector and FPGA ballout.

At first glance, because I stated I was using two pairs, having second copies may seem to make my life easier; but instead of having two pairs in parallel, I would have two doing the exact same thing.


texts: Tesla coil miniature model (slayer exciter) parasitic capacitor

texts:
I have been trying this miniature Tesla coil based on Slayer's exciter circuit (shown below). The part that I don't understand is how this parasitic capacitor exists? I know that for a capacitor there needs to be 2 opposite charges separated by a distance L (which should not be too large as the capacitance becomes negligible). So how do I visualize the capacitor based on these conditions (opposite charges and distance of separation)?

And even assuming that it exists, initially when the switch is turned on voltage is induced on the primary which is reflected on the secondry side charging the capacitor. But after a while since it's only a DC source the induced voltage slowly fades away, but how does the base emitter diode get reverse biased? I have made the circuit and it works even though I did not have the diode shown in the image, but I just want to get it working right! I did see an earlier post similar to this, but it did not really help with my questions.


texts: how to build a low-voltage disconnect switch for DC 12.4V 70A?

texts:
How can I make a device that will make the power connected as long as the voltage of the power-supply keeps over 12.4 V (adjustable) and disconnect it if it falls below?

It also must connect the power back, but only if it rises above 13.5 V.

This has to sustain at least 70 A.

Is there a simple way to build such device?


texts:
I need a thermally AND electrically conductive heat sink compound for attaching power transistors to an aluminium heat sink. I've given Coollaboratory's LiquidPro a try and that oxidized the aluminium. Artic Silver 5 was completely the wrong solution, not conductive at all (I had some exploding FETs on my hands).

Any suggestions?


texts: Boost Converter: Low voltage high current VS. High Voltage, low current?

texts:
I'm in the process of assembling a 1000w total LED light bar, which consists of 10x100w chips, which at full power, consume 3A at around 35V. For this, I'm using 3 dc-dc boost converters, each which converts 12V+ from a car battery, to anything from 12V all the way up to 75V. Each boost converter can handle 20A output, so either works fine.

My question is, should I wire half the LEDs in parallel, and then in series, and have the boost converters pump the voltage all the way up to 70V, or should I keep them in parallel and lower the output voltage to 35V?

I know that normally, boost converters lose efficiency when boosting more, but I'm not sure which will put less stress on the boost converters themselves, as I want to have the setup be as stable as possible.

Thanks in advance.


texts: Raspberry multiple accelerometers please help with schematic

texts: I am new to electronics, and I have been playing around with Raspberry Pi 3 and an ADXL accelerometer. So far, I have managed to draw data in I2C from the accelerometer. However, now I am trying to draw a schematic for a prototype with two ADXL accelerometers. I have made an attempt, but since I am new to this, I have no idea whether I am on the right track. Here's what I've put together. In particular, I am not sure about the pullup resistors.


texts: Issue with RPi and BLDC controller board

texts:
I'm having some trouble figuring out what I'm doing wrong so hopefully someone can spot my error and help set me straight.

These are my motor and the board with everything labeled. Then below that is the schematic of how I have it all hooked up.

I have a PWM output on the BCM 16 pin.  The board adjusts the speed based on the input voltage from 0v-5v.  I've run the program on the RPi and tested the output voltage and PWM works perfectly.

BCM 20 outputs 3.3v "high" to set the direction of the spin.
BCM 21 outputs 3.3v "high" to enable the motor.

The board technically states that the "high" state is 5v so just in case 3.3v wasn't enough I've also connected it straight to a 5v pin.

I tested all the pins and they are all outputting the voltage they should be.  The power source for the motor was tested and is outputting 48v.

Everything looks like it should work but when I run the RPi nothing happens with the motor.

So my biggest question is: does it look like it's wired up correctly?  The main question mark I had was the 5v and ground to the hall sensors on the board. Do the black and red wires from the motor connect there or are there supposed to be from the RPi?

simulate this circuit – Schematic created using CircuitLab


texts:
I am a rookie on both RF and PCB design and I am currently trying to do a 50 ohm 11 watt dummy load project for 100MHz-1GHz.

My calculations are done for the load but I have some questions about designing the PCB.

My new design is as below:

My instructor keeps saying that :

  ''There is a problem with lining up resistors on a row, because you will see a high impedance with reflections on first resistor, then traveling to the next, and the next ... Try designing so that the signal reaches all resistors at the same time. This is difficult with so many resistors. If the attenuator is then directly connected to the same point your series resistor can be of high impedance without affecting signal, because of the short length.''

I don't know how to do this and out of ideas, I tried to do it as a circle around the connector but still not accepted.

Attenuators written as AT1,AT2,AT3.  The other resistors are for the load.

Project Specification:

The power I am trying to terminate is 5-10 watts.
SMD resistors are 560Nohms 1 watt resistors and the signal strength should not exceed -10dBm that is why I am using an 50dB attenuator, to achieve the desired signal strength.

PCB design Specification:

Trace Width = 0.5mm
Dielectric Thickness = 0.3mm
Trace Thickness = 0.036mm
Substrate Dielectric (Ɛr) = 4.6
Total board thickness = 0.39mm
Size of the resistors (x,y) = (6.4,3.2)mm
Dimensions of the board are (x,y) = (7.5,10)cm

EDIT

So I decided to do it as a star or circle shaped design to make the lines equal to each other. Here is what it looks like:

I just draw this schematic to show how my circuit looks like there might be errors.


texts: Sensing a tag passes through a virtual "fence"

texts:
We have two cats who like to hide in our house. It would be great to know where they are in the house. At first I thought about setting up an indoor localization system (iBeacon, etc.) in place, but those seem expensive.

So now I'm thinking that it would be good enough to know which part of the house they're in. There's a short hallway in our house that connects the two parts of the house together. I'm thinking about setting up two sensors, one on each side of the hallway, and put a tag (Bluetooth?) on the cats' collars. The sensor would send a message to the central system whenever the tag gets near it within, say, 50 cm. Would be great if the tag is passive.

Any idea on where I should start? Thanks!

Background: I have some experience with Arduino projects.


texts: How to determine the current rating of Litz wire winding at high frequency?

texts:
How can we determine the current rating of a litz wire winding at high frequency?

This is my try:
For example, if we use 660/38 litz at 85kHz, we can see the equivalent AWG is 10 (reference). Then, according to this table, the amperage for the equivalent AWG of 10 is 15A.

But is it same for high-frequency current?


texts: What is going on with these SPI transmissions?

texts:
I just got a Saleae logic analyzer and I'm using it to hack a Guitar Hero drum set. The main board within the drum set talks to another sub-board using SPI. When I tap into the conversation, I see this:

Black is MOSI, Brown is MISO, Red is CLOCK, and Orange is ENABLE/slave select.

I notice two strange things going on here:

The clock doesn't always "run". It certainly has a pattern to it: It runs when ENABLE is low (every 100 Hz).
Even when ENABLE is high (which I assume to mean the slave is not selected), conversation between the master and slave occurs.

Does anyone have a guess as to what is going on here? Did the board designers get lazy, or did I do something wrong when capturing the data?

Details:

Captured at 4 MHz
The clock runs at 2 MHz, when it is actually running

Here is another view, zoomed in:

Obviously, neither of these pictures provide much information as to what is actually being "said", since I didn't zoom in far enough. But I think that they are enough to get my point across. If you want a different image, just ask.

EDIT

Kris suggested that the enable line is used to poll the slave board into sampling. This makes sense. Check out this screenshot:

The small black bubbles with red outlines are instances where the software was able to decode a SPI transmission. These only occur when the enable line is low, which follows what Kris suggested.


texts: Power supply specifies range of voltage output: how is this possible

texts:
The power supply I bought has an output voltage of "15-24V". I need 19V for my laptop and I couldn't find anything where I could adjust the output voltage to a desired value (like a little screw or something).

Measuring the voltage gives an output voltage of 20V.

Now I am confused: shouldn't the output voltage be specified more exactly?


texts: How do I get v0 using superposition in this circuit?

texts:
I'm trying to get the value of \$V_o\$ in this circuit. Here's the circuit:

Using Superposition theorem:

So first, we remove the voltage source and replace it with a short circuit. Then we calculate \$V_o\$.

Second, we remove the 1A current source replace it with an open circuit, then we calculate \$V_o\$.

Third, we remove 2A current source and replace it with an open circuit, then we calculate \$V_o\$.

Finally, we should add the three values of \$V_o\$ that we got in each case and thus we get the final answer of the total \$V_o\$.

My problem is that I'm unable to calculate the value of \$V_o\$ in each case, what exactly should I do after removing the source to get \$V_o\$. Any help is much appreciated!


texts: slick way of muxing power+NTSC video over RG59/RG136?

texts:
I've got a few NTSC security cameras I'd like to set up around the perimeter of the house. They output standard NTSC video and require 12V for power. I was hoping to power them and take video off the same cable, but I haven't been able to figure out a slick way to do it yet. Structured cable isn't all that expensive but if I could stick with standard RG59 or RG136 I think that'd be best.

Unfortunately it's not like injecting power into RF signals; NTSC video sits around 1Vp-p and has high frequency components to it so it's not as simple as just using a DC blocking cap. Has anyone done something like this before and what kind of success have you had?


texts: How can I build a circuit with this transfer function, using only resistors?

texts:
I'm trying to build a circuit that realizes the transfer function:
$$ V_o = 0.33V_i + 1.65V
$$

Using what I know about voltage dividers and resistive adders, I built:

simulate this circuit – Schematic created using CircuitLab

but this is giving me an output much closer to:
$$V_o = 0.2V_i + 1V$$

Where am I going wrong?


texts:
I recently got a power supply schematic for my project, but for the rest of the project I need to know how much current is being used on the AC input and I don't have the completed board yet to test it or I don't know how to calculate it.

(input 220V)
(output 6.5V 200mA)

I also have an AT Mega 8 on the out put !!!


texts: How much force does a solenoid really have?

texts:
This hopefully isn't too off topic for this forum, but here goes: after many days of tinkering I managed to get a circuit working that, in the end, energizes a solenoid to pull a lever. Sadly, even though the solenoid became energized and pulled its plunger in, it didn't have the strength to pull the lever. The solenoid I used says that it is rated to have a holding force of 1.1 lbs and an operating voltage of 12V.

I gave it 12V, and the solenoid snapped on and pulled its plunger in (it's a pull type of solenoid). But when tied the plunger to the lever, it seemed to lose all strength, not budging the lever at all...not even a wiggle. The same is true if I resisted the movement of the plunger with my hand--or just held it lightly in my hand. It seemed to lack any pull power when there was something there to actually pull. I then upped the voltage by stacking three 9V batteries in series, thinking it might give the solenoid some more muscle--but to no avail.

Is this related to its holding force? Should I buy a different solenoid that can hold more weight? Have others experienced this?

UPDATE

I measured the voltage of the batteries I was using to power the solenoid. It was very interesting. First off, they must have already been drained from powering the solenoid the last time because, although they're relatively new, their voltage from the get-go was reading about 14V instead of the 18V I would expect from putting two 9V in series. I connected them to the solenoid and watched the voltage drop down to less than 2V and continue dropping. So it would seem that at the current that the solenoid needs, the batteries can't sustain their voltage. Perhaps a 12V solenoid can't be powered with common batteries? Or am I thinking about this all wrong and I should expect to see the voltage of the batteries drop when connected to something that draws a current? Especially that much current? Is that normal operation for a battery? Or maybe I need to add a current-limiting resistor, while allowing enough current to go through to power the solenoid?


texts: I would like to know an in depth definition of the re transistor model in BJTs. I know most diagrams very well, but the definition does not. Also, can you guys help me differentiate the small scale transistor model into the re transistor model? I am using Robert Boylestad's Electronic Devices and Circuit Theory by the way.


texts: TCA9509 level translating I2C bus repeater - can levels be the same?

texts:
The TCA9509, a nice little I2C bus repeater, has two supplies: \$V_{CCA}\$ and \$V_{CCB}\$, for supplying the two sides, master and slave respectively.

I can't tell if it can be used as a normal bus repeater for an all-\$5V\$ bus, or whether the master bus must be 1 volt lower. The datasheet seems annoyingly ambiguous: the expression \$V_{CCA} \leq (V_{CCB} - 1)\$ appears in the "Electrical Characteristics" section, some of the Application examples and even on the main page, as linked above, under Parametrics:Supply restrictions, as shown:

Obviously not actually from the datasheet, but someone thought it important enough to extract it and put it on the main page. All the examples in the datasheet ensure that \$V_{CCA}\$ is at least a volt lower than \$V_{CCB}\$, and the constraint is mentioned multiple times in the datasheet.

The description says:

  This TCA9509 integrated circuit is an I2C bus/SMBus
  Repeater for use in I2C/SMBus systems. It can also
  provide bidirectional voltage-level translation (up-
  translation/down-translation) between low voltages
  (down to \$0.9V\$) and higher voltages (\$2.7V\$ to \$5.5V\$)
  in mixed-mode applications. This device enables I2C
  and similar bus systems to be extended, without
  degradation of performance even during level shifting.

The "It can also provide..." wording sounds awfully like level-shifting is an additional, optional capability. The actual "Recommended Operating Conditions" - where you'd expect restrictions like this to appear - doesn't mention it or suggest it (max value for both is \$5.5V\$, not \$V_{CCA}=4.5V\$, \$V_{CCB}=5.5V\$, as you'd expect if this was a real limit).

Does anyone know the truth, please? I want to run both sides at \$5V\$, plain and simple. Is there something I've missed here?


texts: I am trying to make a electro magnet. I bought a coil of enamel copper wire from Ebay. How do I determine its resistance?

texts:
I didn't even know you need AWG rating to get a coil's resistance. But this is may sound naive, can I use the physics formula: $$R=\rho\frac{L}{A}$$.

\$\rho\$ is resistivity of copper, which I looked up to be \$0.000 000 017 W m\$.
I know the length, \$L\$, is 100m. And the diameter is \$.5mm\$. So I know the cross-sectional area, \$A\$.

Now, my question is how accurate is the result?

Here is the website where I bought the coil:
http://www.ebay.com/itm/142313954017


texts: I2S on dsPIC gets interrupt on both left and right channels, how to distinguish them?

texts:
This is hopefully not too silly question: I did set up the dsPIC33CK256MP503 to work with audio microphone via I2S, and it does interrupt for each 32-bit data as expected.
There is per I2S standard alternating of left and right channels, see my analyzer picture.
The PIC's SPI automatically generates the clock and WS streams. Microphone answers with data and PIC calls an interrupt every 32-bits.
Once I am in the interrupt routine... how to easily recognize that specific interrupt is from left or from right channel (or what was the value of WS output)?
I do not want to use the data value of 0x0000000 from the Right channel for that, because what if someone has two microphones and there would be actual data as well? I rather know what was the status of WS channels select generated by the PIC at the time of interrupt.
Anyone can suggest a simple trick how to do it?


texts: How to split high current low voltage? Voltage regulators , current regulators(?)

texts:
I am using a 20v dc laptop charger that supplies 4 amps. I need 5v dc 4 amps. When I use a linear voltage regulator it’s too much current to pass through safely.. 15 amps change and 4 amps, so I use a buck converter. After converting with buck converter I have a whopping 16 amps available.. and for one thing my buck converter cannot sustain this voltage and I'd also like to reduce the current to what I need, 4-5 amps. From where I’ve read there are many solutions available for splitting voltage and regulating voltage, is there a solution for high current?

Also is it more practical to limit the current before the voltage is converted? How can that be done?

I suppose if I limited the current so that when it changes to 5v it could be the perfect amperage, that’s works better.
I’ve seen current limiters for small current values and also using resistors to limit current or voltage but not on this scale.

EDIT:

this post covers most of the information that may be needed to answer this question Choosing power supply, how to get the voltage and current ratings?? as suggested by @The Photon

the remaining issue i have here is with this example in mind , explained by @stevenvh "Olin explained with fruit, I'll try to explain with another flow: water. If my faucet can fill a bucket in a minute that's its maximum flow, or current. That's the 1000 mA the wall wart specifies. Yet I can open the faucet partly to fill my glass, and then I'm the 500 mA device. The faucet still can supply 10 liter per minute, but will supply less if I ask for less. I can ask for anything as long as it isn't more than the 10 liter per minute. If I want only a few drops to fill a thimble I'll be a 1 mA device. From a 1000 mA supply."

with my setup my faucet(the buck converter) is rated for 10 liters per minute and my pump(laptop power supply) can do 16 liters per minute.. so i am seeking a way to limit the amount of flow, also similar to how a circuit breaker functions. (probably using a fuse)
so the idea is get a bigger faucet or a smaller pump or limit it in between.
i can make it so that my valve only open to 5A

To explain this further i am looking to limit the amount of current that is available so it doesn't reach 16A output. With a 2A wallwart that plugs into a 15A wall socket , the current limiting is set within the wallwart rather than within the wall socket. The wall socket can provide 15A so that it's available to more devices and a wallwart is designed so it has current protections limiting it to a 2A draw.

How can i limit the current requested by the buck converter to 5A?


texts: Thevenin Equivalent Voltage: why ignore the 3-kΩ resistor?

texts: In order to find the Thevenin voltage here, why is it that the 3k Οhm resistor is ignored and no current goes through it? (hence \$V_{TH}=8mA \cdot 7kΩ = 56V\$)


texts: Does a 5w LED lamp require 5w/per hour to run ? eg. would 200 x 5w LED lamps running for 1 hour would require 1kwhr of electricity. Or is the 5w related to some other time scale ?


texts:
I designed a 6-bit current-mode R2R DAC in LTSpice. This is the output spectrum with a 500kHz input sinusoid to an ideal ADC (running at 10MHz clock) which feeds directly into the DAC. Vin is input to ADC, Vout is output of DAC

The output FFT spectrum looks like this:

I have a few questions about this:

How do I determine the SNR and SNDR of this? Usually when I use Cadence Virtuoso for this kind of stuff, it gives me that output.
Secondly, does my FFT spectrum seem okay? I know there is a lot of posts about LTSpice putting junk at the end of the FFT. I have tried my best to follow all the tips given by others on how to reduce it. (plotwinsize, etc.)


texts: Putting linear feedback shift registers on FPGA's

texts: I need to put seven 128bit linear feedack shift registers on a FPGA chip. Are there any FPGA's that can impliment this? Thank you.


texts: How to best run long distance low voltage electric

texts:
I am looking into options for running 12 VDC approximately 2000 feet to power some remote equipment. The equipment will have a low current draw (2A max).

I am seeking to keep the cost low.  Copper wire is quite expensive, especially as size gets larger.

Here are the options I can think of...  Can anyone suggest a better alternative?

Run 1AWG wire the entire distance and input about 14VDC  (Too expensive!)
Run 14AWG or smaller (24AWG?) wire and input 120VAC with a step-down transformer and rectifier/smoothing circuitry at the destination (is this crazy?)
Use solar power with deep-cycle battery and charger (unreliable?)
Battery-only system: swap out and recharge batteries as they discharge. (too much maintenance)

Any suggestions for a better way to do this?


texts: I know why silicon is used for ICs and transistors in general due to its doping features. But I don't know why we use silicon as a PCBs, all we need is to isolate pins from each other in a PCB, right? So, will any insulating material work? Such as wood?


texts:
In this circuit I am wondering if I really need the n-channel mosfet to control my dual p-channel MOSFET. I think I can drive this straight from the micro. Just want to second opinion before I modify my design.

The CG2_En output can go from 0V to 3.3V. EDIT: The P-Channel MOSFET does not need to switch 20V but it does need to block 20V when it is off.  It will only be asked to switch 5V. (Still entertaining answers that require 20V since I have another circuit that will) By default the micro can have its input buffer off presenting somewhat high impedance.  Once it wakes it can put out 3.3V. In either state I think the micro would still be subject to a reverse current flow due to the overvoltage.  The spec sheet says it can handle an injection current of 1ma (Attiny 1606). @20V with the 47k resistor in place worst case would be (20V-3.3V+0.6V)/47000 = 0.37mA. (I didn't add the 330)
Note: This circuit should be initially off.
I intend to keep R10 but dump R6 and Q4.  Doable?

Original Circuit

The New circuit


texts: In my application the user needs to read a few simple shapes and characters under the bright sunlight. In terms of visibility, what would be the ideal solution? I am basically looking for experience of previous implementors or some research on the subject. Currently considering simple LED matrix (8x8) and blue color.


texts: How does the loopback on a non-retriggerable monostable work?

texts:
I understand how to connect a monstable multivibrator to be in the non-retriggerable mode. Just loopback the /Q to the falling edge input or the Q to the rising edge output) as in the following picture (taken from the MC14528B datasheet).

Now I think I understand this can be used as a divide by two counter circuit. If I feed it 1kHz square wave on the A pin, i should get a 500Hz square wave on the Q output pin. This would give the following timing diagram:

I do not understand why the feedback of the /Q output into the falling edge trigger input (B) enables this behavior? Can anybody provide more insight on why this loop back suppresses the action of the rising edge on the A port at 1ms?


texts: In this clipper circuit, what is the value of output voltage when the diode is off?

texts:
I am having confusion over what value the output waveform will take when the input voltage has negative half cycle (so that diode is reverse biased). In my intuition, the diode acts as open circuit and output voltage should be 2V. And during positive half cycle, the output voltage is still 2V for Vin < 2V(as diode is still reverse biased) and then follow Vin for all other values of Vin.

The problem is that I don't get the same answer as my textbook depicts. My answer looks something like this:

Is this the correct way, or am I wrong?

Edit: The Texbook says:


texts:
I have a Peltier (TEC) module, with diodes in series with each lead. (see image below)

I'm not quite sure what the specs are for the diode, but it says 130 on one line and SB560 on another, so I did a google search and found this.

How can I figure out how what the actual voltage on the Peltier element will be?


texts: Adding a resistor to a adjustable LDO to be able to adjust it via a DAC?

texts:
simulate this circuit – Schematic created using CircuitLab

This circuit lets me adjust the output voltage of a LDO further by varying V2 via a DAC. I am trying to understand how it works and why this works. Also, how do I come up with the equation that will determine my output voltage based on the value of V2. I am using the LT1965 that has a 1.2V adj.


texts: The phase between current and voltage in LC circuit

texts:
I came across this question in my text book and it says:

  When does Voltage lag current by 90 degrees in an AC circuit contains only a capacitor and an inductor (its ohmic resistance is negligible).

And I thought of this:

  When Xl = 2Xc.

Is my answer correct? As in the solution the book mentioned two methods and mine wasn't one of them. They are:

  When the capcitive reactance is larger than the inductive reactance.
  When we take the inducor out of the circuit.


texts: Add a voltage offset to a resistor ladder R-2R

texts:
I want a cheap DAC from a microcontroller for audio output. A resistor ladder is one solution. The output needs to be buffered by an op amp. Most op amps have some limitation on how close the input and output can be to the rails.

How can a resistor ladder be modified so that the output is some offset from the rails? Instead of 3.3V to 0V, I would like to limit the output to 3.0V to 0.3V without losing the 8-bits of resolution.


texts:
The title does not tell the entire story. I have successfully powered my WeMos by supplying 5vdc to the 5v pin. My power source is 12v battery so I am using a buck converter to drop the voltage to 5v. All is well so far. However, I need to trigger 12vdc relays so I am using a ULN2803 Darlington IC to drive the relays.
I am using the same 12v battery source. This is where my problem seems to be. Everything works if I power the WeMos via USB but if I unplug USB and apply 5vdc to the 5v pin. I fry the WeMos if I leave it connected for more than a few seconds.
If I remove the yellow 5V connection in the lower left and connect USB, everything works. This is my first WeMos project and I'm not great at electronics so I may have everything wrong here. :-\
I am powering the relay directly rather than using a relay module because I need a 4PDT relay. This is the relay I'm using: https://www.amazon.com/gp/product/B07QXYPJH7?pf_rd_r=QF9QDBDWNHVJMV4MH62T&pf_rd_p=5ae2c7f8-e0c6-4f35-9071-dc3240e894a8&pd_rd_r=80baeb28-2cc8-407f-a4c0-46fe12d96261&pd_rd_w=4PD2F&pd_rd_wg=826cB&ref_=pd_gw_unk&th=1
How can I use a single 12VDC power source to both power the WeMos and drive 12VDC relays?


texts: What is the theory behind LC circuit's damping ratio value with a little positive/nagtive feedback?

texts:
I need to measure damping ratio of LC circuit attached to microcontroller. I want to achieve it by measuring voltage of the highest/lowest point of consecutive oscillations by internal ADC.

ADC measures voltage by attaching for a short period of time additional discharged capacitor (typ. 5-8pF) and then by succesive approximation unit it outputs digital value.

But attachment of such capacitor acts as negative or positve feedback during measurements.

In such circuit damping ratio between any two consecutive amplitudes should be constant, but with this little feedback the smaller the amplitude the lower/higher damping ratio is (depending on feedback sign). I tried to find out some theory behind this and get formula describing damping ratio's change but with no success. Can any one give me a formula to calculate it?

P.S.
If it is nessecery I can bring some data to shows this behaviour.


texts: Resistor and Capacitor Package types Eagle CAD

texts:
For a Eagle CAD PCB board design, I am trying to use through-hole capacitors and resistors

I am using C050-035X075 package type capacitors from Eagle CAD library and 0207/10 for Resistors.

Are these the standard through hole resistors and capacitors? or am I doing something terribly wrong.

The capacitors are mainly decoupling 0.1 uF capacitors


texts: What is wrong with this LTspiceIV model of a Deliyannis bandpass filter

texts:
I'm trying to analyze a Deliyannis bandpass filter at fc=7.15Mhz. I have constructed the following in LTspiceIV:

which results in the following net list:

* C:\Program Files (x86)\LTC\LTspiceIV\Draft1.asc
XU1 0 N005 N002 N003 N006 LT1818
V1 N003 N006 5
C1 N002 N001 2.7p
C2 N005 N001 2.7p
R1 N004 N001 8450
R2 N001 0 432
R3 N002 N005 165k
V2 N004 0 AC 1
R4 N002 0 50
.ac lin 1000 6MEG 8MEG
.lib LTC2.LIB
.backanno
.end

However the results are not, it seems, consistent with a bandpass filter:

It should be noted that I am new to spice and rf circuits, so there could be several errors.

Thanks.


texts: Understanding the complex circuitry in supplying voltage to an IC chip

texts:
I'm very new to microcontrollers and I'm trying to understand the purpose of the pinouts of an IC so that I can interface it to a microcontroller. Most of the pinout description from the datasheet are straight forward, but then I look at a sample application schematic and it's gotten really complex and confusing. In particular, the part circled in red that deals with supplying the necessary voltages.

Most of the microcontroller projects I've worked with simply required a supply of Vcc and ground, so I'm having a really hard time in why all those circuitry is necessary. Are there any resources I can look into to understand where that circuitry design came from? A simple explanation on their purposes would be most appreciated.


texts: How can I run a 6.5V-100V power meter on 5V?

texts:
I have an eBay power meter (V/A/W/Wh) that is specced between DC 6.5V and 100V. It's wired with a 75mV 100A shunt, like this:

If I wanted to run the thing at 5 volts what would be the easiest way? There's an 3.3V linear regulator on the board (Z1) so I assume the logic runs fine on less than 6.5V. I haven't checked what the LCD backlight runs on, but I guess it would be fine on 5 volts.

My first thought was to remove D1 (1N4007) which has a 1 V forward voltage drop and replace with a short, but I'd rather keep the reverse protection. What would be the easiest way to convert this to run on 5V? On 5V it doesn't even power on. When I connect it to a 12V supply it runs fine, except the readings (other than current) would obviously be off.

Here's a picture of the circuit board. U2 is the LCD controller. Z1 is a 3.3V linear regulator. Also the 2 points marked "W" read 3.15 volts. Other components I haven't checked.

Edit: U3 is a chip marked MXM11P62 and I could only find a Chinese datasheet and here is a Google translation

Thanks for the answers...


texts: What is the role of discrete resistors and capacitors in a motherboard?

texts: I know the basic function of resistors and capacitors. I know filters, oscillators, one-shot,  differentiator/integrator, ADC/DAC, power supplies, etc. But in a motherboard why are there so many external resistors and capacitors? How many of these analog circuits are there? Or does it have something to do with the copper transmission lines?


texts: Microchip 9808 temperature sensor - Incorrect calculation result

texts:
I am using a Microchip MCP9808 I2C temperature sensor (https://learn.adafruit.com/adafruit-mcp9808-precision-i2c-temperature-sensor-guide/overview).

I'm having problems being able to calculate the temperature using the values I'm reading from the sensor.

The temperature is 13 bits wide. According to the datasheet, I need to send two read commands, the first read to return the upper byte and the second read will return the lower byte. 3 of the remaining bits are used to indicate temperature alarms, and 1 bit is used to indicate the sign of the reading (positive or negative).

I'm able to read the two bytes, by using the sample code from the datasheet as a starting point. However, the values I'm getting from it are incorrect. I'm also unable to get negative temperatures, so I think my code has something wrong with it.

I'm using a USB->I2C adaptor, and I've written a C# implementation of the datasheet sample code to calculate the temperature.

And then my code (which apart from some extra necessary castings due to the way C# handles data types) I think is identical.

    public static double CalculateAmbientTemperature(byte upperByte, byte lowerByte)
    {
        const byte ALERT_MASK_VALUE = 0x1F;
        const byte CLEAR_SIGN_MASK = 0x0F;

        double temperature = 0.00;

        upperByte = (byte)(upperByte & ALERT_MASK_VALUE);

        // Ambient temperature less than 0 degrees
        if((upperByte & (byte)(upperByte & 0x10)) == 0x10)
        {
            upperByte = (byte)(upperByte & CLEAR_SIGN_MASK);
            temperature = 256.0 - ((double)upperByte * 16.0 + (double)lowerByte / 16.0);
        }
        else
        {
            temperature = ((double)upperByte * 16.0 + (double)lowerByte / 16.0);
        }

        return temperature;
    }

So to test the code, I've been sending the bytes: START_BIT 0x3E (the address) 0x05 (the address of the temperature register) This tells the sensor to point the register pointer at the temperature register, so that when I send the two read commands, it reads from that register.

And when I read the data back, I'm getting 0xC1 0x24. When I pass these values to the function, I'm getting 17.0625 degrees C. Bearing in mind, I'm holding an ice cube on the sensor. (Currently don't have a more precise way). So basically, my calculation is faulty but I don't know where to begin with fixing it.

Any help would be appreciated.

(EDIT: To check I'm able to read the chip correctly, I read the Manufacturer ID register and get back the expected 0x54)


texts: Drawback of using Schottky Diode to lower MOSFET threshold voltage?

texts:
I am considering using Schottky diode to lower PMOS's Vth as the following diagram:

As the current extracted from Schottky diode is small enough to provide 0.3-0.4V voltage drop, PMOS's threshold voltage will decrease due to body effect. Thus, PMOS only requires small vgs to be turned on.

However, some people say this method is impractical or rare to see in low voltage IC design. I would like to know if there is any drawback when we use it in LDO. Thanks!


texts:
This should be pretty straight forward, but my google-ing is not turning anything up... I can build my project successfully in TI Code Composer Studio (CCSv5) and target my device.

Now I want to know my program code size, so that I know how much space I have for future growth etc. When I develop for AVRs in eclipse with the avr-gcc tool chain it conveniently tells me this in the compiler output in the console. Even Arduino compilation reports this information right there in the IDE. No such luck with CCS it seems.

So the question is, how do you get the MSP430 memory utilization statistics in CCS? A bonus would be how to configure the IDE to tell me this information in the console output when I do a build.

Note: I know that it tells me in the console when I load it onto a device with Run => Debug. I'm looking for output at compile time.


texts: Switching between three output voltage settings on a switching regulator

texts:
I am currently in the process of designing a load control circuit based on a switching voltage regulator. The assumption is that the regulator would provide three different voltage settings based on the user's choice, using a tactile switch.
My idea was to develop and test this logic circuit on a simple voltage regulator like MC34063 from TI. Since in most (all?) of the switching regulators the output voltage setting is based on a voltage divider composed of two resistors, my idea was to find a way to switch on/off the resistors in a pair, in order to obtain different voltage values.
I thought of using a logic counter CD4017 with clock input being a tactile switch and then to pass one of the three states of choice to the regulator's circuit, through a transistor with the resistor being switched connected to the NPN's emitter.
However, I encountered some trouble setting up the whole circuit on a breadboard so I came back to LTSpice to evaluate and test its performance. It turned out that it does not work, due to the fact that the connection through a transistor makes the voltage on the feedback to the comparator constant and over 1.25V which makes the whole device unable to regulate the voltage according to the desired values.
Below is my setup presented in the LTSpice - I simulate the clicks on the tactile switch by a pulse signal to the CD4017 clock input.

Is there any way to make it work with the use of these elements? Is there any other way to switch the resistor pair and obtain the three voltage settings on the regulator's output?
Thanks in advance, any advice would be appreciated.


texts:
I have a DALI interface board the circuit of which is shown below. This board was working so far but now the optocoupler in the circuit is not switching on DALI signals.

Dali interface circuit:

The DALI bus is around 16v. I have tested the optocoupler separately by removing the DALI bus and giving external supply and it is switching properly.
Below are some scope shots were taken at different test points(Points are mentioned as the title of image)

Pin1_U2 to GND

Cathode D4 to GND

pin2 U2 to GND

DALI BUS

DALI IN

Optocoupler is supposed to switch between 5v and 0v but as you can see output amplitude is very minimal. what could be the possible issue?


texts: Reset and trigger 555 timer with one push button

texts:
I want to turn on a LED with a single push button. When the button is pressed, the LED has to be turned on for an X amount of time. But what I also want, is to turn of the LED with the same push button in this X time period. I've searched the internet for quite a time now but I never found the solution for this problem. Is there anyone who can help me with this ?
Thanks in advance


texts: In2 I2C leakage at each IO pin (0.1VDD<VI<0.9VDD)can be 10u. Why have they mentioned 0.1 to 0.9VDD specifically?

texts: Why havethey mentioned the input in such a way i.e 0.1VDD<VI<0.9VDD?


texts:
I have a question about the following Pulse Plethysmograph Diagram:

This diagram was taken from the project page.

But that website explicitly states:

  Components are not critical but the two 2.2 µF capacitors must be able to stand some reverse bias so they should be non–polarized or tantalum.

My question is:
Should I use non-polarized or polarized 2.2uF capacitors? (The diagram and the above description seem to contradict themselves), How about the 68nF ones?


texts: Why is my 5K potentiometer sparking during regulation of LED bulb?

texts:
There are two potentiometers in my DC circuit analysis. When I turn on the wall switch, which is connected to the 220V transformer which is in turn connected to the circuit, one of the potentiometers is sparking (as seen in the picture), when it is being regulated to increase/decrease light intensity of the LED. What could be the reason for this?

And should I replace the potentiometer before I solder the components onto a narrow board? Could it be sparking because the circuit is connected to a very high voltage wall power supply, instead of a battery with lower power?

Please help out.


texts:
I a working on a project around the STM32H7 (Nucleo STM32H743ZI2) on which I am using the user USB to communicate through CDC interface.
Everything is working fine, however, I just noticed that this User USB port is not powering the board. I am pretty sure initially it was, but well it's no longer the case.
what is the CubeMX settings to enable this user USB port to power the board? The goal is to use this USB port to connect to the PC communicating with the board (and not the STLINK USB).
right now I have the USB_OTG_FS set to Device_Only, activate_VBUS set to VBUS sensing and activate_SOF is enabled.
thanks!


texts: If the energy meter sees a reactive load, will it register a lower reading?

texts:
At an exhibition on home appliances, I saw this guy hawking his 'energy saver device'. The guy claimed that merely plugging his instrument into the supply would reduce the consumption reported in an energy usage meter by a fourth. He mentioned something about the load seen by the meter being non-resistive ...

Not sure if this is the right forum to post the question (feel free to vote for the question to be closed)... Anyhow I find myself wondering  - Is this just a sales-pitch (no warranty/guarantee on the device) or is there some fire to the smoke?


texts: How to debug new Brushless DC motor not working?

texts:
I'm building an autonomous boat, for which I so far used this brushless motor powered by this drone ESC (both pictured above).
I now want to start using a more efficient motor, so I bought the 12V 4000RPM version of this motor (pictured below this message). I removed the old motor and connected up the new one. It gives the same beeping sounds when I calibrate it with the software, but after that, it doesn't move at all. I use the exact same code and ESC setup with the new and the old motor. I tried the Go code I used for the other motor, and also tried some other example Python code with which the other motor also works great.
The wiring info of the new motor has 6 wires, as compared to the only 3 of the old motor. The wiring diagram of the new motor looks like this:

I connected it as follows:

the + of the ESC => red wire of the motor
the - of the ESC => black and the blue wire of the motor
the PWM signal of the ESC => yellow wire of the motor

I'm not sure if this is the correct way, but it's the best I could come up with. I'm not sure whther the -/minus of the ESC should also be connected to the blue wire, so I tried it both connected and disconnected. But none of my attempts make the motor spin.
And from here I'm kinda lost. Seeing that I'm more of a software guy than an electronics guy I don't really know how to debug such a hardware problem.
Could anybody give me some pointers on what the problem might be, and more importantly, how you go about debugging something like this? All tips are welcome!


texts:
I want to measure magnetic fields with my oscilloscope, so I need a magnetic field sensor / probe.

My oscilloscope does a FFT for 50Hz to 2MHz.

The sensor should be 3D, because I don't care for direction.
The sensor should be sensitive enough for measuring human exposure at computer workstations.

I have read that a Hall  effect sensor should do this and is fairly easy to drive, which would explain why I haven't found any good ready to use sensors in the internet.

My search coil tends to be very sensitive at 590KHz, maybe an article about search coil calibration would be helpful.

When choosing a Hall effect sensor,

Do I have to consider my frequency range (50Hz to 2MHz?)
Are all Hall effect sensors sensitive enough for measurements of human exposure at computer workstations (60cm to CCFL screens?


texts: Bundling HDMI cables and power cables: can it stand the RF?

texts:
I need to run a large number (12) of HDMI cables along with some AC power cables (two, for monitor power.)
I was hoping to be able to put them all together into a sleeve to make them more manageable.
I know for sure that doing that with analog VGA cables would cause tremendous amounts of signal loss. However, with HDMI being digital, I assume they will fare much better.
Is this practical, or do I need to give them some separation to prevent interference?
The cables will be about 10 ft long, and I'll probably bundle the low speed USB 2.0 cables in the same trunk.


texts:
I am using an Xmega32A4U
I convert an audio with ADC and after processing it sends out with DAC.
I checked Power supply and try all of parameter to use ADC but it is a big problem and the audio out covered with a white noise.
After measure ADC conversion to a USART I see it have 10 difference output  value in a fixed dc input.
I try it with ATmega8 and maximum difference value is 2 number but it's so slow for audio processing.
If I can reduce tolerance of conversion result to 3?


texts: Intel IA-32 Protected Mode HW-Tasks: IRET return from interrupts within a nested HW-Task ( EFLAGS.NT=1 )

texts:
The INTEL manuals tell us that when a HW-task has been switched to using a 'CALL' instruction the destination task is considered a nested task:

The processor

copies the segment selector for the current TSS ( task A ) to the previous task link
field of the TSS for the destination task ( task B's TSS )
sets the EFLAGS.NT = 1

                  task A  task B

                    v      .
                    .    / v
                    v   /  .
                    .  /   v
                    v /    .
                    ./     v
               CALL        .
                    .\     v
                    v \    .
                    .  \   v
                    v   \  .
                    .     IRET
                    v

The 'nested task' should eventually return to the calling task ( task A ) by means of an IRET instruction. When software in task B uses an IRET instruction return, the processor checks for EFLAGS.NT = 1, it then uses the value in the previous task link field to return to the previous task ( task A ) if the flag is set.

However nothing is to stop an interrupt occuring while execution is in progress in task B.

Now when the handler tries to return to the interrupted thread in task B, it would do this with an IRET. Since the handler is executing within task B, it would seem that the processor checks the EFLAGS.NT and since it will still be set ( i.e. 1 ) returns to task A, rather than returning to the next instruction of the interrupted thread within task B.

                      WHAT HAPPENS WHEN:

                      task A  task B

                        v      .
                        .    / v
                        v   /  .   /.
                        .  /   v  / v
                        v /    . /  .
                        ./     v/ interrupt handler
               CALL            .    v
                        .           .
                        v           v
                        .          IRET
                        v          EFLAGS.NT = 1
                        .              Get the previous task link in B's TSS?
                        v          OR
                                       Go to the return address on the stack?

I would expect the following behaviour

                      task A  task B

                        v      .
                        .    / v
                        v   /  .   /.
                        .  /   v  / v
                        v /    . /  .
                        ./     v/ interrupt handler
               CALL            .    v
                        .\     v \  .
                        v \    .  \ v
                        .  \   v   IRET
                        v   \  .
                        .     IRET
                        v

In other words first a return is made from the interrupt which occured during task B ( consumes 1st IRET ) then a return is made to the 'calling' task ( task A ) which uses a 2nd IRET.

Would this be reasonable?

If so how does the processor 'know' that eventhough EFLAGS.NT=1, it must return to the interrupted thread in task B itself; or in other words it is dealing with a simple interrupt return in within task B and that it should not return to task A ?

What am I missing here?


texts: Help with following question about Muxes?

texts: Could anybody provide help in answering this question? I'm pretty sure I should use a Kmap to analyze it but not sure how to do so.


texts: Is there a PCB coplanar edge connector made for high power transmission instead of data transmission?

texts: Looking for a PCB-to-PCB coplanar edge connector that can carry ideally 40V and 30A.


texts: Output impedance imbalance and CM noise in truly floating sources

texts:
In the following Figure 1 and Figure 2, the sensor is the one in dashed box.
The output impedance of the sensor is big and in this case is 1k Ohm.

And as you see regardless of the sensors are bipolar or single-ended output, the sensor ground is shared with the InAmp's AI GND. So in Figure 1 and 2 the sources are not truly floating correct?

simulate this circuit – Schematic created using CircuitLab

On the other hand in below Figure 3, the same sensor's signal and ground first goes to this signal cond. module and then to the InAmp. There is truly isolation so we can say truly floating. The inputs are floating with respect to AI GND and the power supply common.

simulate this circuit

Why does in Figure 1 and Figure 2 the 1k output impedance matter for common mode noise but not in Figure 3? How can this be explained by using diagrams and current flows ect. for clarity?

After reading Andy Aka's answer here are the models for above scenarios and sim results:

(left-click to zoom in)


texts:
What radiation pattern will this integrated PCB antenna have?

Will it be mostly horizontal (XZ plane), or mostly out the top side, or something else?

It's a 2.4GHz module. Datasheet is here:

http://ww1.microchip.com/downloads/en/devicedoc/atmel-42486-atsamr21b18-mz210pa_datasheet.pdf


texts: Component for switching 1000V - 100Amps condenser discharge pulse

texts:
I am miniaturizing a circuit used to generate a pulse using condensers into an inductive load. I am a little lost on what would be the best type of component to choose to start the discharge (ie. a switch closing the circuit and allowing the condensers to discharge in the inductance).

What in your opinion would be the best component given these constraints:

Pulse width in the order of us (0.1 to 100us).
Pulse frequency of 10hz.
Component must be able to block at least 1000V.
Pulse current between 100Amps to 200Amps.
Size constrained: Less than a few inches for this particular component.
Can be expensive, but not in the hundreds of $.

Condensers are in the order of a few uF and the load is an inductance of between 50 to 300 uH and a few ohms.

So far I am thinking either Silicon Carbide MOSFETS (big and expensive but allow good control), or avalanche diodes like this one (cheap and small). Thyristors are what I am using rigth now but I am trying to get smaller and if possible cheaper.
As far as I read, spark gaps and Gaz discharge tube tend to have a limited lifetime (which is not okay in my case).

Do you see any other alternative ? Did I miss something ?


texts: Noise problem with buck/boost switching regulator

texts:
I am designing a electrical device for a research project (I'm a PhD student, but unfortunately not EE!). More info on the device can be found at http://iridia.ulb.ac.be/supp/IridiaSupp2012-002/

The last prototype had a problem with the power supply, and thus I tried to overcome the problems by designing a new and better one. As the device is powered by a Lithium-Ion battery, I decided to use a LTC3536 buck/boost switching regulator: http://cds.linear.com/docs/en/datasheet/3536fa.pdf

I basically used the reference implementation (page 1 of the datasheet) for a 1A/3.3V power supply as seen here:

(source: ulb.ac.be)

There are three separate ground planes: PGND, coming from the battery, GND, the normal ground, and AGND for analog sensors etc.

This is the board as I designed it in Eagle. I already noticed some deviations from the reference design, for example, C3 and C4 should be places a lot closer to the LTC (U3):

(source: ulb.ac.be)

This is the output that I see on VCC (with or without load, Vin=4.7V)
As you can see, Vpp is huge! It's smaller for Vin<4.3V, but still quite substantial.

(source: ulb.ac.be)

I did a bit of trial-and-error by moving C3 and C2 closer to the LTC, and adding in another 1µF cap to C7. This didn't help much. I then replaced C7 with a 220µF cap instead of the 22µF mentioned in the datasheet. With this, Vpp is ~200mV. This is a lot better but still a long way from what is specified in the datasheet. Additionally, this is only the case for Vin>4.3V; below this threshold Vpp is still over 2V. I guess it's the boost vs. the buck regulation that makes the change, but I don't really see how I can correct it.

Now the questions:

I was wondering if I made a mistake that is obvious to the trained eye?
Why is Vpp so huge, when the noise given in the datasheet is only 40mV?
Is there another way to fix this other than randomly dropping in different output capacitors?


texts: Why does a large filter capacitor draw large (peak) current?

texts:
In my book it says that in a diode rectifier the capacitor gets charged close to the peak of the ac voltage.

Is it true the larger the (filter) capacitor the larger the peak current drawn and if so why?
And why is it that when the capacitor gets charged to a value close to the peak of the ac (input) voltage that the current through the rectifier is very large near the peak of the 50-Hz ac (input) voltage ?


texts:
I've printed, populated and baked a test PCB with most components that I needed. I left off a GPS chip and associated passives because the GPS chip itself costs more than the rest of the board, and I'm testing unrelated functionality at the moment (and I thought there would be a good chance that I'd have to change something). That said, the stencil was made with the GPS components in mind, and those pads are now covered with solder.

Would simply covering all the pads with flux, populating the components and reflowing again work?

I'm doing all of this by hand, and would prefer to avoid having populate another 100+ BOM lineitem board. The IC itself is an LGA 69 package, and the passives are mostly 0402.


texts: Isolated Flyback vs Isolated Buck Voltage converter. What are the Pros and Cons?

texts: I am working on a project where I need an isolated power supply. My input is 10-20V and I am looking to get an isolated 3.6V out @ 5A or more. My priorities are easy of implementation, voltage stability, and cost, in that order. There are no specific size limitations. I am new to both types of circuits, what are the pros and cons of both in this application?


texts: What is the foam stuff that semiconductors come in?

texts: Sometimes when I order semi-conductors, there pins are put in this black foam (im guessing static sensitive stuff). If I put a high voltage through it, it conducts and burns. What is this stuff called and what is it made out of?


texts:
So I tried to power up codec (CS4272) together with my F401 board.
After a lot of tweaking I got I2S to work and send data, but there were gaps. Upon further investigation it looks like HAL_I2SEx_TransmitReceive_IT doesn't return until it sends all of it's data.
for(int i=0;;i++)
  {
    for(int j=0;j<256;j++)
        data[2*j]=16843009*(i%256);
    HAL_GPIO_WritePin(GPIOC,GPIO_PIN_13,1);
    HAL_I2SEx_TransmitReceive_IT(&hi2s2,(uint16_t*)data,(uint16_t*)ret,128);
    HAL_GPIO_WritePin(GPIOC,GPIO_PIN_13,0);
    //printf("dupa: %d\r\n",i);
  }

Here is main loop from my test code. The rest is just cubeMX output. Logic analyser shows that I2S activity is only when C13 is HIGH. Why is so? How can it be fixed?
Here's is logic analyser trace of signals. On top there's C13 and I2S below.

As you can see the I2S transmit doesn't return until it's done.
And no, C13 is not CS for codec but simply debug utility to track why I2S transmission executes so slowly


texts:
https://www.hobbyprojects.com/8051_tutorial/acall_absolute_call.html

I was learning about acall on the above website, but then came across the term page. What exactly is a page?